Datasets:

adesogus

/

wikipedia-cs

like 0

290

https://en.wikipedia.org/wiki/A

A

A, or a, is the first letter and the first vowel of the modern English alphabet and the ISO basic Latin alphabet. Its name in English is a (pronounced ), plural aes. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version can be written in two forms: the double-storey a and single-storey ɑ. The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In the English grammar, "a", and its variant "an", are indefinite articles. History The earliest certain ancestor of "A" is aleph (also written 'aleph), the first letter of the Phoenician alphabet, which consisted entirely of consonants (for that reason, it is also called an abjad to distinguish it from a true alphabet). In turn, the ancestor of aleph may have been a pictogram of an ox head in proto-Sinaitic script influenced by Egyptian hieroglyphs, styled as a triangular head with two horns extended. When the ancient Greeks adopted the alphabet, they had no use for a letter to represent the glottal stop—the consonant sound that the letter denoted in Phoenician and other Semitic languages, and that was the first phoneme of the Phoenician pronunciation of the letter—so they used their version of the sign to represent the vowel , and called it by the similar name of alpha. In the earliest Greek inscriptions after the Greek Dark Ages, dating to the 8th century BC, the letter rests upon its side, but in the Greek alphabet of later times it generally resembles the modern capital letter, although many local varieties can be distinguished by the shortening of one leg, or by the angle at which the cross line is set. The Etruscans brought the Greek alphabet to their civilization in the Italian Peninsula and left the letter unchanged. The Romans later adopted the Etruscan alphabet to write the Latin language, and the resulting letter was preserved in the Latin alphabet that would come to be used to write many languages, including English. Typographic variants During Roman times, there were many variant forms of the letter "A". First was the monumental or lapidary style, which was used when inscribing on stone or other "permanent" media. There was also a cursive style used for everyday or utilitarian writing, which was done on more perishable surfaces. Due to the "perishable" nature of these surfaces, there are not as many examples of this style as there are of the monumental, but there are still many surviving examples of different types of cursive, such as majuscule cursive, minuscule cursive, and semicursive minuscule. Variants also existed that were intermediate between the monumental and cursive styles. The known variants include the early semi-uncial, the uncial, and the later semi-uncial. At the end of the Roman Empire (5th century AD), several variants of the cursive minuscule developed through Western Europe. Among these were the semicursive minuscule of Italy, the Merovingian script in France, the Visigothic script in Spain, and the Insular or Anglo-Irish semi-uncial or Anglo-Saxon majuscule of Great Britain. By the 9th century, the Caroline script, which was very similar to the present-day form, was the principal form used in book-making, before the advent of the printing press. This form was derived through a combining of prior forms. 15th-century Italy saw the formation of the two main variants that are known today. These variants, the Italic and Roman forms, were derived from the Caroline Script version. The Italic form, also called script a, is used in most current handwriting; it consists of a circle and vertical stroke on the right ("ɑ"). This slowly developed from the fifth-century form resembling the Greek letter tau in the hands of medieval Irish and English writers. The Roman form is used in most printed material; it consists of a small loop with an arc over it ("a"). Both derive from the majuscule (capital) form. In Greek handwriting, it was common to join the left leg and horizontal stroke into a single loop, as demonstrated by the uncial version shown. Many fonts then made the right leg vertical. In some of these, the serif that began the right leg stroke developed into an arc, resulting in the printed form, while in others it was dropped, resulting in the modern handwritten form. Graphic designers refer to the Italic and Roman forms as "single decker a" and "double decker a" respectively. Italic type is commonly used to mark emphasis or more generally to distinguish one part of a text from the rest (set in Roman type). There are some other cases aside from italic type where script a ("ɑ"), also called Latin alpha, is used in contrast with Latin "a" (such as in the International Phonetic Alphabet). Use in writing systems English In modern English orthography, the letter represents at least seven different vowel sounds: the near-open front unrounded vowel as in pad; the open back unrounded vowel as in father, which is closer to its original Latin and Greek sound; the diphthong as in ace and major (usually when is followed by one, or occasionally two, consonants and then another vowel letter) – this results from Middle English lengthening followed by the Great Vowel Shift; the modified form of the above sound that occurs before , as in square and Mary; the rounded vowel of water; the shorter rounded vowel (not present in General American) in was and what; a schwa, in many unstressed syllables, as in about, comma, solar. The double sequence does not occur in native English words, but is found in some words derived from foreign languages such as Aaron and aardvark. However, occurs in many common digraphs, all with their own sound or sounds, particularly , , , , and . is the third-most-commonly used letter in English (after and ) and French, the second most common in Spanish, and the most common in Portuguese. About 8.167% of letters used in English texts tend to be ; the number is around 7.636% in French, 11.525% in Spanish, and 14.634% for Portuguese. Other languages In most languages that use the Latin alphabet, denotes an open unrounded vowel, such as , , or . An exception is Saanich, in which (and the glyph Á) stands for a close-mid front unrounded vowel . Other systems In phonetic and phonemic notation: in the International Phonetic Alphabet, is used for the open front unrounded vowel, is used for the open central unrounded vowel, and is used for the open back unrounded vowel. in X-SAMPA, is used for the open front unrounded vowel and is used for the open back unrounded vowel. Other uses In algebra, the letter a along with various other letters of the alphabet is often used to denote a variable, with various conventional meanings in different areas of mathematics. Moreover, in 1637, René Descartes "invented the convention of representing unknowns in equations by x, y, and z, and knowns by a, b, and c", and this convention is still often followed, especially in elementary algebra. In geometry, capital A, B, C etc. are used to denote segments, lines, rays, etc. A capital A is also typically used as one of the letters to represent an angle in a triangle, the lowercase a representing the side opposite angle A. "A" is often used to denote something or someone of a better or more prestigious quality or status: A-, A or A+, the best grade that can be assigned by teachers for students' schoolwork; "A grade" for clean restaurants; A-list celebrities, etc. Such associations can have a motivating effect, as exposure to the letter A has been found to improve performance, when compared with other letters. "A" is used as a prefix on some words, such as asymmetry, to mean "not" or "without" (from Greek). In English grammar, "a", and its variant "an", is an indefinite article, used to introduce noun phrases. Finally, the letter A is used to denote size, as in a narrow size shoe, or a small cup size in a brassiere. Related characters Descendants and related characters in the Latin alphabet Æ æ : Latin AE ligature A with diacritics: Å å Ǻ ǻ Ḁ ḁ ẚ Ă ă Ặ ặ Ắ ắ Ằ ằ Ẳ ẳ Ẵ ẵ Ȃ ȃ Â â Ậ ậ Ấ ấ Ầ ầ Ẫ ẫ Ẩ ẩ Ả ả Ǎ ǎ Ⱥ ⱥ Ȧ ȧ Ǡ ǡ Ạ ạ Ä ä Ǟ ǟ À à Ȁ ȁ Á á Ā ā Ā̀ ā̀ Ã ã Ą ą Ą́ ą́ Ą̃ ą̃ A̲ a̲ ᶏ Phonetic alphabet symbols related to A (the International Phonetic Alphabet only uses lowercase, but uppercase forms are used in some other writing systems): Ɑ ɑ : Latin letter alpha / script A, which represents an open back unrounded vowel in the IPA ᶐ : Latin small letter alpha with retroflex hook Ɐ ɐ : Turned A, which represents a near-open central vowel in the IPA Λ ʌ : Turned V (also called a wedge, a caret, or a hat), which represents an open-mid back unrounded vowel in the IPA Ɒ ɒ : Turned alpha / script A, which represents an open back rounded vowel in the IPA ᶛ : Modifier letter small turned alpha ᴀ : Small capital A, an obsolete or non-standard symbol in the International Phonetic Alphabet used to represent various sounds (mainly open vowels) A a ᵄ : Modifier letters are used in the Uralic Phonetic Alphabet (UPA) (sometimes encoded with Unicode subscripts and superscripts) a : Subscript small a is used in Indo-European studies ꬱ : Small letter a reversed-schwa is used in the Teuthonista phonetic transcription system Ꞻ ꞻ : Glottal A, used in the transliteration of Ugaritic Derived signs, symbols and abbreviations ª : an ordinal indicator Å : Ångström sign ∀ : a turned capital letter A, used in predicate logic to specify universal quantification ("for all") @ : At sign ₳ : Argentine austral Ancestors and siblings in other alphabets 𐤀 : Semitic letter Aleph, from which the following symbols originally derive Α α : Greek letter Alpha, from which the following letters derive А а : Cyrillic letter A : Coptic letter Alpha 𐌀 : Old Italic A, which is the ancestor of modern Latin A : Runic letter ansuz, which probably derives from old Italic A : Gothic letter aza/asks Ա ա : Armenian letter Ayb Computing codes 1 Other representations Notes Footnotes References External links History of the Alphabet ISO basic Latin letters Vowel letters

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

308

https://en.wikipedia.org/wiki/Aristotle

Aristotle

Aristotle (; Aristotélēs, ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Lyceum, the Peripatetic school of philosophy, and the Aristotelian tradition. His writings cover many subjects including physics, biology, zoology, metaphysics, logic, ethics, aesthetics, poetry, theatre, music, rhetoric, psychology, linguistics, economics, politics, meteorology, geology and government. Aristotle provided a complex synthesis of the various philosophies existing prior to him. It was above all from his teachings that the West inherited its intellectual lexicon, as well as problems and methods of inquiry. As a result, his philosophy has exerted a unique influence on almost every form of knowledge in the West and it continues to be a subject of contemporary philosophical discussion. Little is known about his life. Aristotle was born in the city of Stagira in Northern Greece. His father, Nicomachus, died when Aristotle was a child, and he was brought up by a guardian. At seventeen or eighteen years of age he joined Plato's Academy in Athens and remained there until the age of thirty-seven (c. 347 BC). Shortly after Plato died, Aristotle left Athens and, at the request of Philip II of Macedon, tutored Alexander the Great beginning in 343 BC. He established a library in the Lyceum which helped him to produce many of his hundreds of books on papyrus scrolls. Though Aristotle wrote many elegant treatises and dialogues for publication, only around a third of his original output has survived, none of it intended for publication. Aristotle's views profoundly shaped medieval scholarship. The influence of physical science extended from Late Antiquity and the Early Middle Ages into the Renaissance, and were not replaced systematically until the Enlightenment and theories such as classical mechanics were developed. Some of Aristotle's zoological observations found in his biology, such as on the hectocotyl (reproductive) arm of the octopus, were disbelieved until the 19th century. He also influenced Judeo-Islamic philosophies (800–1400) during the Middle Ages, as well as Christian theology, especially the Neoplatonism of the Early Church and the scholastic tradition of the Catholic Church. Aristotle was revered among medieval Muslim scholars as "The First Teacher", and among medieval Christians like Thomas Aquinas as simply "The Philosopher", while the poet Dante called him “the master of those who know". His works contain the earliest known formal study of logic, and were studied by medieval scholars such as Peter Abelard and John Buridan. Aristotle's influence on logic continued well into the 19th century. In addition, his ethics, though always influential, gained renewed interest with the modern advent of virtue ethics. Aristotle has been called "the father of logic", "the father of biology", "the father of political science", "the father of zoology", "the father of embryology", "the father of natural law", "the father of scientific method", "the father of rhetoric", "the father of psychology", "the father of realism", "the father of criticism", "the father of individualism", "the father of teleology", and "the father of meteorology". Life In general, the details of Aristotle's life are not well-established. The biographies written in ancient times are often speculative and historians only agree on a few salient points. Aristotle, whose name means "the best purpose" in Ancient Greek, was born in 384 BC in Stagira, Chalcidice, about 55 km (34 miles) east of modern-day Thessaloniki. His father, Nicomachus, was the personal physician to King Amyntas of Macedon. While he was young, Aristotle learned about biology and medical information, which was taught by his father. Both of Aristotle's parents died when he was about thirteen, and Proxenus of Atarneus became his guardian. Although little information about Aristotle's childhood has survived, he probably spent some time within the Macedonian palace, making his first connections with the Macedonian monarchy. At the age of seventeen or eighteen, Aristotle moved to Athens to continue his education at Plato's Academy. He probably experienced the Eleusinian Mysteries as he wrote when describing the sights one viewed at the Eleusinian Mysteries, "to experience is to learn" [παθείν μαθεĩν]. Aristotle remained in Athens for nearly twenty years before leaving in 348/47 BC. The traditional story about his departure records that he was disappointed with the academy's direction after control passed to Plato's nephew Speusippus, although it is possible that he feared the anti-Macedonian sentiments in Athens at that time and left before Plato died. Aristotle then accompanied Xenocrates to the court of his friend Hermias of Atarneus in Asia Minor. After the death of Hermias, Aristotle travelled with his pupil Theophrastus to the island of Lesbos, where together they researched the botany and zoology of the island and its sheltered lagoon. While in Lesbos, Aristotle married Pythias, either Hermias's adoptive daughter or niece. She bore him a daughter, whom they also named Pythias. In 343 BC, Aristotle was invited by Philip II of Macedon to become the tutor to his son Alexander. Aristotle was appointed as the head of the royal academy of Macedon. During Aristotle's time in the Macedonian court, he gave lessons not only to Alexander but also to two other future kings: Ptolemy and Cassander. Aristotle encouraged Alexander toward eastern conquest, and Aristotle's own attitude towards Persia was unabashedly ethnocentric. In one famous example, he counsels Alexander to be "a leader to the Greeks and a despot to the barbarians, to look after the former as after friends and relatives, and to deal with the latter as with beasts or plants". By 335 BC, Aristotle had returned to Athens, establishing his own school there known as the Lyceum. Aristotle conducted courses at the school for the next twelve years. While in Athens, his wife Pythias died and Aristotle became involved with Herpyllis of Stagira, who bore him a son whom he named after his father, Nicomachus. If the Suda an uncritical compilation from the Middle Ages is accurate, he may also have had an erômenos, Palaephatus of Abydus. This period in Athens, between 335 and 323 BC, is when Aristotle is believed to have composed many of his works. He wrote many dialogues, of which only fragments have survived. Those works that have survived are in treatise form and were not, for the most part, intended for widespread publication; they are generally thought to be lecture aids for his students. His most important treatises include Physics, Metaphysics, Nicomachean Ethics, Politics, On the Soul and Poetics. Aristotle studied and made significant contributions to "logic, metaphysics, mathematics, physics, biology, botany, ethics, politics, agriculture, medicine, dance, and theatre." Near the end of his life, Alexander and Aristotle became estranged over Alexander's relationship with Persia and Persians. A widespread tradition in antiquity suspected Aristotle of playing a role in Alexander's death, but the only evidence of this is an unlikely claim made some six years after the death. Following Alexander's death, anti-Macedonian sentiment in Athens was rekindled. In 322 BC, Demophilus and Eurymedon the Hierophant reportedly denounced Aristotle for impiety, prompting him to flee to his mother's family estate in Chalcis, on Euboea, at which occasion he was said to have stated: "I will not allow the Athenians to sin twice against philosophy" – a reference to Athens's trial and execution of Socrates. He died on Euboea of natural causes later that same year, having named his student Antipater as his chief executor and leaving a will in which he asked to be buried next to his wife. Speculative philosophy Logic With the Prior Analytics, Aristotle is credited with the earliest study of formal logic, and his conception of it was the dominant form of Western logic until 19th-century advances in mathematical logic. Kant stated in the Critique of Pure Reason that with Aristotle logic reached its completion. Organon What is today called Aristotelian logic with its types of syllogism (methods of logical argument), Aristotle himself would have labelled "analytics". The term "logic" he reserved to mean dialectics. Most of Aristotle's work is probably not in its original form, because it was most likely edited by students and later lecturers. The logical works of Aristotle were compiled into a set of six books called the Organon around 40 BC by Andronicus of Rhodes or others among his followers. The books are: Categories On Interpretation Prior Analytics Posterior Analytics Topics On Sophistical Refutations The order of the books (or the teachings from which they are composed) is not certain, but this list was derived from analysis of Aristotle's writings. It goes from the basics, the analysis of simple terms in the Categories, the analysis of propositions and their elementary relations in On Interpretation, to the study of more complex forms, namely, syllogisms (in the Analytics) and dialectics (in the Topics and Sophistical Refutations). The first three treatises form the core of the logical theory stricto sensu: the grammar of the language of logic and the correct rules of reasoning. The Rhetoric is not conventionally included, but it states that it relies on the Topics. Metaphysics The word "metaphysics" appears to have been coined by the first century AD editor who assembled various small selections of Aristotle's works to the treatise we know by the name Metaphysics. Aristotle called it "first philosophy", and distinguished it from mathematics and natural science (physics) as the contemplative (theoretikē) philosophy which is "theological" and studies the divine. He wrote in his Metaphysics (1026a16): Substance Aristotle examines the concepts of substance (ousia) and essence (to ti ên einai, "the what it was to be") in his Metaphysics (Book VII), and he concludes that a particular substance is a combination of both matter and form, a philosophical theory called hylomorphism. In Book VIII, he distinguishes the matter of the substance as the substratum, or the stuff of which it is composed. For example, the matter of a house is the bricks, stones, timbers, etc., or whatever constitutes the potential house, while the form of the substance is the actual house, namely 'covering for bodies and chattels' or any other differentia that let us define something as a house. The formula that gives the components is the account of the matter, and the formula that gives the differentia is the account of the form. Immanent realism Like his teacher Plato, Aristotle's philosophy aims at the universal. Aristotle's ontology places the universal (katholou) in particulars (kath' hekaston), things in the world, whereas for Plato the universal is a separately existing form which actual things imitate. For Aristotle, "form" is still what phenomena are based on, but is "instantiated" in a particular substance. Plato argued that all things have a universal form, which could be either a property or a relation to other things. When one looks at an apple, for example, one sees an apple, and one can also analyse a form of an apple. In this distinction, there is a particular apple and a universal form of an apple. Moreover, one can place an apple next to a book, so that one can speak of both the book and apple as being next to each other. Plato argued that there are some universal forms that are not a part of particular things. For example, it is possible that there is no particular good in existence, but "good" is still a proper universal form. Aristotle disagreed with Plato on this point, arguing that all universals are instantiated at some period of time, and that there are no universals that are unattached to existing things. In addition, Aristotle disagreed with Plato about the location of universals. Where Plato spoke of the world of forms, a place where all universal forms subsist, Aristotle maintained that universals exist within each thing on which each universal is predicated. So, according to Aristotle, the form of apple exists within each apple, rather than in the world of the forms. Potentiality and actuality With regard to the change (kinesis) and its causes now, as he defines in his Physics and On Generation and Corruption 319b–320a, he distinguishes the coming to be from: growth and diminution, which is change in quantity; locomotion, which is change in space; and alteration, which is change in quality. The coming to be is a change where nothing persists of which the resultant is a property. In that particular change he introduces the concept of potentiality (dynamis) and actuality (entelecheia) in association with the matter and the form. Referring to potentiality, this is what a thing is capable of doing or being acted upon if the conditions are right and it is not prevented by something else. For example, the seed of a plant in the soil is potentially (dynamei) a plant, and if it is not prevented by something, it will become a plant. Potentially beings can either 'act' (poiein) or 'be acted upon' (paschein), which can be either innate or learned. For example, the eyes possess the potentiality of sight (innate – being acted upon), while the capability of playing the flute can be possessed by learning (exercise – acting). Actuality is the fulfilment of the end of the potentiality. Because the end (telos) is the principle of every change, and for the sake of the end exists potentiality, therefore actuality is the end. Referring then to the previous example, it can be said that an actuality is when a plant does one of the activities that plants do. In summary, the matter used to make a house has potentiality to be a house and both the activity of building and the form of the final house are actualities, which is also a final cause or end. Then Aristotle proceeds and concludes that the actuality is prior to potentiality in formula, in time and in substantiality. With this definition of the particular substance (i.e., matter and form), Aristotle tries to solve the problem of the unity of the beings, for example, "what is it that makes a man one"? Since, according to Plato there are two Ideas: animal and biped, how then is man a unity? However, according to Aristotle, the potential being (matter) and the actual one (form) are one and the same. Epistemology Aristotle's immanent realism means his epistemology is based on the study of things that exist or happen in the world, and rises to knowledge of the universal, whereas for Plato epistemology begins with knowledge of universal Forms (or ideas) and descends to knowledge of particular imitations of these. Aristotle uses induction from examples alongside deduction, whereas Plato relies on deduction from a priori principles. Natural philosophy Aristotle's "natural philosophy" spans a wide range of natural phenomena including those now covered by physics, biology and other natural sciences. In Aristotle's terminology, "natural philosophy" is a branch of philosophy examining the phenomena of the natural world, and includes fields that would be regarded today as physics, biology and other natural sciences. Aristotle's work encompassed virtually all facets of intellectual inquiry. Aristotle makes philosophy in the broad sense coextensive with reasoning, which he also would describe as "science". However, his use of the term science carries a different meaning than that covered by the term "scientific method". For Aristotle, "all science (dianoia) is either practical, poetical or theoretical" (Metaphysics 1025b25). His practical science includes ethics and politics; his poetical science means the study of fine arts including poetry; his theoretical science covers physics, mathematics and metaphysics. Physics Five elements In his On Generation and Corruption, Aristotle related each of the four elements proposed earlier by Empedocles, Earth, Water, Air, and Fire, to two of the four sensible qualities, hot, cold, wet, and dry. In the Empedoclean scheme, all matter was made of the four elements, in differing proportions. Aristotle's scheme added the heavenly Aether, the divine substance of the heavenly spheres, stars and planets. Motion Aristotle describes two kinds of motion: "violent" or "unnatural motion", such as that of a thrown stone, in the Physics (254b10), and "natural motion", such as of a falling object, in On the Heavens (300a20). In violent motion, as soon as the agent stops causing it, the motion stops also: in other words, the natural state of an object is to be at rest, since Aristotle does not address friction. With this understanding, it can be observed that, as Aristotle stated, heavy objects (on the ground, say) require more force to make them move; and objects pushed with greater force move faster. This would imply the equation , incorrect in modern physics. Natural motion depends on the element concerned: the aether naturally moves in a circle around the heavens, while the 4 Empedoclean elements move vertically up (like fire, as is observed) or down (like earth) towards their natural resting places. In the Physics (215a25), Aristotle effectively states a quantitative law, that the speed, v, of a falling body is proportional (say, with constant c) to its weight, W, and inversely proportional to the density, ρ, of the fluid in which it is falling: Aristotle implies that in a vacuum the speed of fall would become infinite, and concludes from this apparent absurdity that a vacuum is not possible. Opinions have varied on whether Aristotle intended to state quantitative laws. Henri Carteron held the "extreme view" that Aristotle's concept of force was basically qualitative, but other authors reject this. Archimedes corrected Aristotle's theory that bodies move towards their natural resting places; metal boats can float if they displace enough water; floating depends in Archimedes' scheme on the mass and volume of the object, not, as Aristotle thought, its elementary composition. Aristotle's writings on motion remained influential until the Early Modern period. John Philoponus (in the Middle Ages) and Galileo are said to have shown by experiment that Aristotle's claim that a heavier object falls faster than a lighter object is incorrect. A contrary opinion is given by Carlo Rovelli, who argues that Aristotle's physics of motion is correct within its domain of validity, that of objects in the Earth's gravitational field immersed in a fluid such as air. In this system, heavy bodies in steady fall indeed travel faster than light ones (whether friction is ignored, or not), and they do fall more slowly in a denser medium. Newton's "forced" motion corresponds to Aristotle's "violent" motion with its external agent, but Aristotle's assumption that the agent's effect stops immediately it stops acting (e.g., the ball leaves the thrower's hand) has awkward consequences: he has to suppose that surrounding fluid helps to push the ball along to make it continue to rise even though the hand is no longer acting on it, resulting in the Medieval theory of impetus. Four causes Aristotle suggested that the reason for anything coming about can be attributed to four different types of simultaneously active factors. His term aitia is traditionally translated as "cause", but it does not always refer to temporal sequence; it might be better translated as "explanation", but the traditional rendering will be employed here. Material cause describes the material out of which something is composed. Thus the material cause of a table is wood. It is not about action. It does not mean that one domino knocks over another domino. The formal cause is its form, i.e., the arrangement of that matter. It tells one what a thing is, that a thing is determined by the definition, form, pattern, essence, whole, synthesis or archetype. It embraces the account of causes in terms of fundamental principles or general laws, as the whole (i.e., macrostructure) is the cause of its parts, a relationship known as the whole-part causation. Plainly put, the formal cause is the idea in the mind of the sculptor that brings the sculpture into being. A simple example of the formal cause is the mental image or idea that allows an artist, architect, or engineer to create a drawing. The efficient cause is "the primary source", or that from which the change under consideration proceeds. It identifies 'what makes of what is made and what causes change of what is changed' and so suggests all sorts of agents, non-living or living, acting as the sources of change or movement or rest. Representing the current understanding of causality as the relation of cause and effect, this covers the modern definitions of "cause" as either the agent or agency or particular events or states of affairs. In the case of two dominoes, when the first is knocked over it causes the second also to fall over. In the case of animals, this agency is a combination of how it develops from the egg, and how its body functions. The final cause (telos) is its purpose, the reason why a thing exists or is done, including both purposeful and instrumental actions and activities. The final cause is the purpose or function that something is supposed to serve. This covers modern ideas of motivating causes, such as volition. In the case of living things, it implies adaptation to a particular way of life. Optics Aristotle describes experiments in optics using a camera obscura in Problems, book 15. The apparatus consisted of a dark chamber with a small aperture that let light in. With it, he saw that whatever shape he made the hole, the sun's image always remained circular. He also noted that increasing the distance between the aperture and the image surface magnified the image. Chance and spontaneity According to Aristotle, spontaneity and chance are causes of some things, distinguishable from other types of cause such as simple necessity. Chance as an incidental cause lies in the realm of accidental things, "from what is spontaneous". There is also more a specific kind of chance, which Aristotle names "luck", that only applies to people's moral choices. Astronomy In astronomy, Aristotle refuted Democritus's claim that the Milky Way was made up of "those stars which are shaded by the earth from the sun's rays," pointing out correctly that if "the size of the sun is greater than that of the earth and the distance of the stars from the earth many times greater than that of the sun, then... the sun shines on all the stars and the earth screens none of them." Geology/Natural Sciences Aristotle was one of the first people to record any geological observations. He stated that geological change was too slow to be observed in one person's lifetime. The geologist Charles Lyell noted that Aristotle described such change, including "lakes that had dried up" and "deserts that had become watered by rivers", giving as examples the growth of the Nile delta since the time of Homer, and "the upheaving of one of the Aeolian islands, previous to a volcanic eruption."' Aristotle also made many observations about the hydrologic cycle and meteorology (including his major writings "Meteorologica"). For example, he made some of the earliest observations about desalination: he observed early – and correctly – that when seawater is heated, freshwater evaporates and that the oceans are then replenished by the cycle of rainfall and river runoff ("I have proved by experiment that salt water evaporated forms fresh and the vapor does not when it condenses condense into sea water again.") Biology Empirical research Aristotle was the first person to study biology systematically, and biology forms a large part of his writings. He spent two years observing and describing the zoology of Lesbos and the surrounding seas, including in particular the Pyrrha lagoon in the centre of Lesbos. His data in History of Animals, Generation of Animals, Movement of Animals, and Parts of Animals are assembled from his own observations, statements given by people with specialized knowledge such as beekeepers and fishermen, and less accurate accounts provided by travellers from overseas. His apparent emphasis on animals rather than plants is a historical accident: his works on botany have been lost, but two books on plants by his pupil Theophrastus have survived. Aristotle reports on the sea-life visible from observation on Lesbos and the catches of fishermen. He describes the catfish, electric ray, and frogfish in detail, as well as cephalopods such as the octopus and paper nautilus. His description of the hectocotyl arm of cephalopods, used in sexual reproduction, was widely disbelieved until the 19th century. He gives accurate descriptions of the four-chambered fore-stomachs of ruminants, and of the ovoviviparous embryological development of the hound shark. He notes that an animal's structure is well matched to function, so, among birds, the heron, which lives in marshes with soft mud and lives by catching fish, has a long neck and long legs, and a sharp spear-like beak, whereas ducks that swim have short legs and webbed feet. Darwin, too, noted these sorts of differences between similar kinds of animal, but unlike Aristotle used the data to come to the theory of evolution. Aristotle's writings can seem to modern readers close to implying evolution, but while Aristotle was aware that new mutations or hybridizations could occur, he saw these as rare accidents. For Aristotle, accidents, like heat waves in winter, must be considered distinct from natural causes. He was thus critical of Empedocles's materialist theory of a "survival of the fittest" origin of living things and their organs, and ridiculed the idea that accidents could lead to orderly results. To put his views into modern terms, he nowhere says that different species can have a common ancestor, or that one kind can change into another, or that kinds can become extinct. Scientific style Aristotle did not do experiments in the modern sense. He used the ancient Greek term pepeiramenoi to mean observations, or at most investigative procedures like dissection. In Generation of Animals, he finds a fertilized hen's egg of a suitable stage and opens it to see the embryo's heart beating inside. Instead, he practiced a different style of science: systematically gathering data, discovering patterns common to whole groups of animals, and inferring possible causal explanations from these. This style is common in modern biology when large amounts of data become available in a new field, such as genomics. It does not result in the same certainty as experimental science, but it sets out testable hypotheses and constructs a narrative explanation of what is observed. In this sense, Aristotle's biology is scientific. From the data he collected and documented, Aristotle inferred quite a number of rules relating the life-history features of the live-bearing tetrapods (terrestrial placental mammals) that he studied. Among these correct predictions are the following. Brood size decreases with (adult) body mass, so that an elephant has fewer young (usually just one) per brood than a mouse. Lifespan increases with gestation period, and also with body mass, so that elephants live longer than mice, have a longer period of gestation, and are heavier. As a final example, fecundity decreases with lifespan, so long-lived kinds like elephants have fewer young in total than short-lived kinds like mice. Classification of living things Aristotle distinguished about 500 species of animals, arranging these in the History of Animals in a graded scale of perfection, a nonreligious version of the scala naturae, with man at the top. His system had eleven grades of animal, from highest potential to lowest, expressed in their form at birth: the highest gave live birth to hot and wet creatures, the lowest laid cold, dry mineral-like eggs. Animals came above plants, and these in turn were above minerals. see also: He grouped what the modern zoologist would call vertebrates as the hotter "animals with blood", and below them the colder invertebrates as "animals without blood". Those with blood were divided into the live-bearing (mammals), and the egg-laying (birds, reptiles, fish). Those without blood were insects, crustacea (non-shelled – cephalopods, and shelled) and the hard-shelled molluscs (bivalves and gastropods). He recognised that animals did not exactly fit into a linear scale, and noted various exceptions, such as that sharks had a placenta like the tetrapods. To a modern biologist, the explanation, not available to Aristotle, is convergent evolution. Philosophers of science have generally concluded that Aristotle was not interested in taxonomy, but zoologists who studied this question recently think otherwise. He believed that purposive final causes guided all natural processes; this teleological view justified his observed data as an expression of formal design. Psychology Soul Aristotle's psychology, given in his treatise On the Soul (peri psychēs), posits three kinds of soul ("psyches"): the vegetative soul, the sensitive soul, and the rational soul. Humans have a rational soul. The human soul incorporates the powers of the other kinds: Like the vegetative soul it can grow and nourish itself; like the sensitive soul it can experience sensations and move locally. The unique part of the human, rational soul is its ability to receive forms of other things and to compare them using the nous (intellect) and logos (reason). For Aristotle, the soul is the form of a living being. Because all beings are composites of form and matter, the form of living beings is that which endows them with what is specific to living beings, e.g. the ability to initiate movement (or in the case of plants, growth and chemical transformations, which Aristotle considers types of movement). In contrast to earlier philosophers, but in accordance with the Egyptians, he placed the rational soul in the heart, rather than the brain. Notable is Aristotle's division of sensation and thought, which generally differed from the concepts of previous philosophers, with the exception of Alcmaeon. Memory According to Aristotle in On the Soul, memory is the ability to hold a perceived experience in the mind and to distinguish between the internal "appearance" and an occurrence in the past. In other words, a memory is a mental picture (phantasm) that can be recovered. Aristotle believed an impression is left on a semi-fluid bodily organ that undergoes several changes in order to make a memory. A memory occurs when stimuli such as sights or sounds are so complex that the nervous system cannot receive all the impressions at once. These changes are the same as those involved in the operations of sensation, Aristotelian , and thinking. Aristotle uses the term 'memory' for the actual retaining of an experience in the impression that can develop from sensation, and for the intellectual anxiety that comes with the impression because it is formed at a particular time and processing specific contents. Memory is of the past, prediction is of the future, and sensation is of the present. Retrieval of impressions cannot be performed suddenly. A transitional channel is needed and located in past experiences, both for previous experience and present experience. Because Aristotle believes people receive all kinds of sense perceptions and perceive them as impressions, people are continually weaving together new impressions of experiences. To search for these impressions, people search the memory itself. Within the memory, if one experience is offered instead of a specific memory, that person will reject this experience until they find what they are looking for. Recollection occurs when one retrieved experience naturally follows another. If the chain of "images" is needed, one memory will stimulate the next. When people recall experiences, they stimulate certain previous experiences until they reach the one that is needed. Recollection is thus the self-directed activity of retrieving the information stored in a memory impression. Only humans can remember impressions of intellectual activity, such as numbers and words. Animals that have perception of time can retrieve memories of their past observations. Remembering involves only perception of the things remembered and of the time passed. Aristotle believed the chain of thought, which ends in recollection of certain impressions, was connected systematically in relationships such as similarity, contrast, and contiguity, described in his laws of association. Aristotle believed that past experiences are hidden within the mind. A force operates to awaken the hidden material to bring up the actual experience. According to Aristotle, association is the power innate in a mental state, which operates upon the unexpressed remains of former experiences, allowing them to rise and be recalled. Dreams Aristotle describes sleep in On Sleep and Wakefulness. Sleep takes place as a result of overuse of the senses or of digestion, so it is vital to the body. While a person is asleep, the critical activities, which include thinking, sensing, recalling and remembering, do not function as they do during wakefulness. Since a person cannot sense during sleep they cannot have desire, which is the result of sensation. However, the senses are able to work during sleep, albeit differently, unless they are weary. Dreams do not involve actually sensing a stimulus. In dreams, sensation is still involved, but in an altered manner. Aristotle explains that when a person stares at a moving stimulus such as the waves in a body of water, and then looks away, the next thing they look at appears to have a wavelike motion. When a person perceives a stimulus and the stimulus is no longer the focus of their attention, it leaves an impression. When the body is awake and the senses are functioning properly, a person constantly encounters new stimuli to sense and so the impressions of previously perceived stimuli are ignored. However, during sleep the impressions made throughout the day are noticed as there are no new distracting sensory experiences. So, dreams result from these lasting impressions. Since impressions are all that are left and not the exact stimuli, dreams do not resemble the actual waking experience. During sleep, a person is in an altered state of mind. Aristotle compares a sleeping person to a person who is overtaken by strong feelings toward a stimulus. For example, a person who has a strong infatuation with someone may begin to think they see that person everywhere because they are so overtaken by their feelings. Since a person sleeping is in a suggestible state and unable to make judgements, they become easily deceived by what appears in their dreams, like the infatuated person. This leads the person to believe the dream is real, even when the dreams are absurd in nature. In De Anima iii 3, Aristotle ascribes the ability to create, to store, and to recall images in the absence of perception to the faculty of imagination, phantasia. One component of Aristotle's theory of dreams disagrees with previously held beliefs. He claimed that dreams are not foretelling and not sent by a divine being. Aristotle reasoned naturalistically that instances in which dreams do resemble future events are simply coincidences. Aristotle claimed that a dream is first established by the fact that the person is asleep when they experience it. If a person had an image appear for a moment after waking up or if they see something in the dark it is not considered a dream because they were awake when it occurred. Secondly, any sensory experience that is perceived while a person is asleep does not qualify as part of a dream. For example, if, while a person is sleeping, a door shuts and in their dream they hear a door is shut, this sensory experience is not part of the dream. Lastly, the images of dreams must be a result of lasting impressions of waking sensory experiences. Practical philosophy Aristotle's practical philosophy covers areas such as ethics, politics, economics, and rhetoric. Ethics Aristotle considered ethics to be a practical rather than theoretical study, i.e., one aimed at becoming good and doing good rather than knowing for its own sake. He wrote several treatises on ethics, including most notably, the Nicomachean Ethics. Aristotle taught that virtue has to do with the proper function (ergon) of a thing. An eye is only a good eye in so much as it can see, because the proper function of an eye is sight. Aristotle reasoned that humans must have a function specific to humans, and that this function must be an activity of the psuchē (soul) in accordance with reason (logos). Aristotle identified such an optimum activity (the virtuous mean, between the accompanying vices of excess or deficiency) of the soul as the aim of all human deliberate action, eudaimonia, generally translated as "happiness" or sometimes "well-being". To have the potential of ever being happy in this way necessarily requires a good character (ēthikē aretē), often translated as moral or ethical virtue or excellence. Aristotle taught that to achieve a virtuous and potentially happy character requires a first stage of having the fortune to be habituated not deliberately, but by teachers, and experience, leading to a later stage in which one consciously chooses to do the best things. When the best people come to live life this way their practical wisdom (phronesis) and their intellect (nous) can develop with each other towards the highest possible human virtue, the wisdom of an accomplished theoretical or speculative thinker, or in other words, a philosopher. Politics In addition to his works on ethics, which address the individual, Aristotle addressed the city in his work titled Politics. Aristotle considered the city to be a natural community. Moreover, he considered the city to be prior in importance to the family which in turn is prior to the individual, "for the whole must of necessity be prior to the part". He famously stated that "man is by nature a political animal" and argued that humanity's defining factor among others in the animal kingdom is its rationality. Aristotle conceived of politics as being like an organism rather than like a machine, and as a collection of parts none of which can exist without the others. Aristotle's conception of the city is organic, and he is considered one of the first to conceive of the city in this manner. The common modern understanding of a political community as a modern state is quite different from Aristotle's understanding. Although he was aware of the existence and potential of larger empires, the natural community according to Aristotle was the city (polis) which functions as a political "community" or "partnership" (koinōnia). The aim of the city is not just to avoid injustice or for economic stability, but rather to allow at least some citizens the possibility to live a good life, and to perform beautiful acts: "The political partnership must be regarded, therefore, as being for the sake of noble actions, not for the sake of living together." This is distinguished from modern approaches, beginning with social contract theory, according to which individuals leave the state of nature because of "fear of violent death" or its "inconveniences." In Protrepticus, the character 'Aristotle' states: As Plato's disciple Aristotle was rather skeptical concerning democracy and, following Plato's vague ideas, he developed a coherent theory of integrating various forms of power into a so-called mixed state: To illustrate this approach, Aristotle proposed a first-of-its-kind mathematical model of voting, albeit textually described, where the democratic principle of "one voter–one vote" is combined with the oligarchic "merit-weighted voting"; for relevant quotes and their translation into mathematical formulas see. Economics Aristotle made substantial contributions to economic thought, especially to thought in the Middle Ages. In Politics, Aristotle addresses the city, property, and trade. His response to criticisms of private property, in Lionel Robbins's view, anticipated later proponents of private property among philosophers and economists, as it related to the overall utility of social arrangements. Aristotle believed that although communal arrangements may seem beneficial to society, and that although private property is often blamed for social strife, such evils in fact come from human nature. In Politics, Aristotle offers one of the earliest accounts of the origin of money. Money came into use because people became dependent on one another, importing what they needed and exporting the surplus. For the sake of convenience, people then agreed to deal in something that is intrinsically useful and easily applicable, such as iron or silver. Aristotle's discussions on retail and interest was a major influence on economic thought in the Middle Ages. He had a low opinion of retail, believing that contrary to using money to procure things one needs in managing the household, retail trade seeks to make a profit. It thus uses goods as a means to an end, rather than as an end unto itself. He believed that retail trade was in this way unnatural. Similarly, Aristotle considered making a profit through interest unnatural, as it makes a gain out of the money itself, and not from its use. Aristotle gave a summary of the function of money that was perhaps remarkably precocious for his time. He wrote that because it is impossible to determine the value of every good through a count of the number of other goods it is worth, the necessity arises of a single universal standard of measurement. Money thus allows for the association of different goods and makes them "commensurable". He goes on to state that money is also useful for future exchange, making it a sort of security. That is, "if we do not want a thing now, we shall be able to get it when we do want it". Rhetoric and poetics Aristotle's Rhetoric proposes that a speaker can use three basic kinds of appeals to persuade his audience: ethos (an appeal to the speaker's character), pathos (an appeal to the audience's emotion), and logos (an appeal to logical reasoning). He also categorizes rhetoric into three genres: epideictic (ceremonial speeches dealing with praise or blame), forensic (judicial speeches over guilt or innocence), and deliberative (speeches calling on an audience to make a decision on an issue). Aristotle also outlines two kinds of rhetorical proofs: enthymeme (proof by syllogism) and paradeigma (proof by example). Aristotle writes in his Poetics that epic poetry, tragedy, comedy, dithyrambic poetry, painting, sculpture, music, and dance are all fundamentally acts of mimesis ("imitation"), each varying in imitation by medium, object, and manner. He applies the term mimesis both as a property of a work of art and also as the product of the artist's intention and contends that the audience's realisation of the mimesis is vital to understanding the work itself. Aristotle states that mimesis is a natural instinct of humanity that separates humans from animals and that all human artistry "follows the pattern of nature". Because of this, Aristotle believed that each of the mimetic arts possesses what Stephen Halliwell calls "highly structured procedures for the achievement of their purposes." For example, music imitates with the media of rhythm and harmony, whereas dance imitates with rhythm alone, and poetry with language. The forms also differ in their object of imitation. Comedy, for instance, is a dramatic imitation of men worse than average; whereas tragedy imitates men slightly better than average. Lastly, the forms differ in their manner of imitation – through narrative or character, through change or no change, and through drama or no drama. While it is believed that Aristotle's Poetics originally comprised two books – one on comedy and one on tragedy – only the portion that focuses on tragedy has survived. Aristotle taught that tragedy is composed of six elements: plot-structure, character, style, thought, spectacle, and lyric poetry. The characters in a tragedy are merely a means of driving the story; and the plot, not the characters, is the chief focus of tragedy. Tragedy is the imitation of action arousing pity and fear, and is meant to effect the catharsis of those same emotions. Aristotle concludes Poetics with a discussion on which, if either, is superior: epic or tragic mimesis. He suggests that because tragedy possesses all the attributes of an epic, possibly possesses additional attributes such as spectacle and music, is more unified, and achieves the aim of its mimesis in shorter scope, it can be considered superior to epic. Aristotle was a keen systematic collector of riddles, folklore, and proverbs; he and his school had a special interest in the riddles of the Delphic Oracle and studied the fables of Aesop. Views on women Aristotle's analysis of procreation describes an active, ensouling masculine element bringing life to an inert, passive female element. On this ground, proponents of feminist metaphysics have accused Aristotle of misogyny and sexism. However, Aristotle gave equal weight to women's happiness as he did to men's, and commented in his Rhetoric that the things that lead to happiness need to be in women as well as men. Influence More than 2300 years after his death, Aristotle remains one of the most influential people who ever lived. He contributed to almost every field of human knowledge then in existence, and he was the founder of many new fields. According to the philosopher Bryan Magee, "it is doubtful whether any human being has ever known as much as he did". Among countless other achievements, Aristotle was the founder of formal logic, pioneered the study of zoology, and left every future scientist and philosopher in his debt through his contributions to the scientific method. Taneli Kukkonen, writing in The Classical Tradition, observes that his achievement in founding two sciences is unmatched, and his reach in influencing "every branch of intellectual enterprise" including Western ethical and political theory, theology, rhetoric and literary analysis is equally long. As a result, Kukkonen argues, any analysis of reality today "will almost certainly carry Aristotelian overtones ... evidence of an exceptionally forceful mind." Jonathan Barnes wrote that "an account of Aristotle's intellectual afterlife would be little less than a history of European thought". On his successor, Theophrastus Aristotle's pupil and successor, Theophrastus, wrote the History of Plants, a pioneering work in botany. Some of his technical terms remain in use, such as carpel from carpos, fruit, and pericarp, from pericarpion, seed chamber. Theophrastus was much less concerned with formal causes than Aristotle was, instead pragmatically describing how plants functioned. On later Greek philosophers The immediate influence of Aristotle's work was felt as the Lyceum grew into the Peripatetic school. Aristotle's notable students included Aristoxenus, Dicaearchus, Demetrius of Phalerum, Eudemos of Rhodes, Harpalus, Hephaestion, Mnason of Phocis, Nicomachus, and Theophrastus. Aristotle's influence over Alexander the Great is seen in the latter's bringing with him on his expedition a host of zoologists, botanists, and researchers. He had also learned a great deal about Persian customs and traditions from his teacher. Although his respect for Aristotle was diminished as his travels made it clear that much of Aristotle's geography was clearly wrong, when the old philosopher released his works to the public, Alexander complained "Thou hast not done well to publish thy acroamatic doctrines; for in what shall I surpass other men if those doctrines wherein I have been trained are to be all men's common property?" On Hellenistic science After Theophrastus, the Lyceum failed to produce any original work. Though interest in Aristotle's ideas survived, they were generally taken unquestioningly. It is not until the age of Alexandria under the Ptolemies that advances in biology can be again found. The first medical teacher at Alexandria, Herophilus of Chalcedon, corrected Aristotle, placing intelligence in the brain, and connected the nervous system to motion and sensation. Herophilus also distinguished between veins and arteries, noting that the latter pulse while the former do not. Though a few ancient atomists such as Lucretius challenged the teleological viewpoint of Aristotelian ideas about life, teleology (and after the rise of Christianity, natural theology) would remain central to biological thought essentially until the 18th and 19th centuries. Ernst Mayr states that there was "nothing of any real consequence in biology after Lucretius and Galen until the Renaissance." On Byzantine scholars Greek Christian scribes played a crucial role in the preservation of Aristotle by copying all the extant Greek language manuscripts of the corpus. The first Greek Christians to comment extensively on Aristotle were Philoponus, Elias, and David in the sixth century, and Stephen of Alexandria in the early seventh century. John Philoponus stands out for having attempted a fundamental critique of Aristotle's views on the eternity of the world, movement, and other elements of Aristotelian thought. Philoponus questioned Aristotle's teaching of physics, noting its flaws and introducing the theory of impetus to explain his observations. After a hiatus of several centuries, formal commentary by Eustratius and Michael of Ephesus reappeared in the late eleventh and early twelfth centuries, apparently sponsored by Anna Comnena. On the medieval Islamic world Aristotle was one of the most revered Western thinkers in early Islamic theology. Most of the still extant works of Aristotle, as well as a number of the original Greek commentaries, were translated into Arabic and studied by Muslim philosophers, scientists and scholars. Averroes, Avicenna and Alpharabius, who wrote on Aristotle in great depth, also influenced Thomas Aquinas and other Western Christian scholastic philosophers. Alkindus greatly admired Aristotle's philosophy, and Averroes spoke of Aristotle as the "exemplar" for all future philosophers. Medieval Muslim scholars regularly described Aristotle as the "First Teacher". The title "teacher" was first given to Aristotle by Muslim scholars, and was later used by Western philosophers (as in the famous poem of Dante) who were influenced by the tradition of Islamic philosophy. On medieval Europe With the loss of the study of ancient Greek in the early medieval Latin West, Aristotle was practically unknown there from c. AD 600 to c. 1100 except through the Latin translation of the Organon made by Boethius. In the twelfth and thirteenth centuries, interest in Aristotle revived and Latin Christians had translations made, both from Arabic translations, such as those by Gerard of Cremona, and from the original Greek, such as those by James of Venice and William of Moerbeke. After the Scholastic Thomas Aquinas wrote his Summa Theologica, working from Moerbeke's translations and calling Aristotle "The Philosopher", the demand for Aristotle's writings grew, and the Greek manuscripts returned to the West, stimulating a revival of Aristotelianism in Europe that continued into the Renaissance. These thinkers blended Aristotelian philosophy with Christianity, bringing the thought of Ancient Greece into the Middle Ages. Scholars such as Boethius, Peter Abelard, and John Buridan worked on Aristotelian logic. The medieval English poet Chaucer describes his student as being happy by having A cautionary medieval tale held that Aristotle advised his pupil Alexander to avoid the king's seductive mistress, Phyllis, but was himself captivated by her, and allowed her to ride him. Phyllis had secretly told Alexander what to expect, and he witnessed Phyllis proving that a woman's charms could overcome even the greatest philosopher's male intellect. Artists such as Hans Baldung produced a series of illustrations of the popular theme. The Italian poet Dante says of Aristotle in The Divine Comedy: Besides Dante's fellow poets, the classical figure that most influenced the Comedy is Aristotle. Dante built up the philosophy of the Comedy with the works of Aristotle as a foundation, just as the scholastics used Aristotle as the basis for their thinking. Dante knew Aristotle directly from Latin translations of his works and indirectly quotations in the works of Albert Magnus. Dante even acknowledges Aristotle's influence explicitly in the poem, specifically when Virgil justifies the Inferno's structure by citing the Nicomachean Ethics. On medieval Judaism Moses Maimonides (considered to be the foremost intellectual figure of medieval Judaism) adopted Aristotelianism from the Islamic scholars and based his Guide for the Perplexed on it and that became the basis of Jewish scholastic philosophy. Maimonides also considered Aristotle to be the greatest philosopher that ever lived, and styled him as the "chief of the philosophers". Also, in his letter to Samuel ibn Tibbon, Maimonides observes that there is no need for Samuel to study the writings of philosophers who preceded Aristotle because the works of the latter are "sufficient by themselves and [superior] to all that were written before them. His intellect, Aristotle's is the extreme limit of human intellect, apart from him upon whom the divine emanation has flowed forth to such an extent that they reach the level of prophecy, there being no level higher". On Early Modern scientists In the Early Modern period, scientists such as William Harvey in England and Galileo Galilei in Italy reacted against the theories of Aristotle and other classical era thinkers like Galen, establishing new theories based to some degree on observation and experiment. Harvey demonstrated the circulation of the blood, establishing that the heart functioned as a pump rather than being the seat of the soul and the controller of the body's heat, as Aristotle thought. Galileo used more doubtful arguments to displace Aristotle's physics, proposing that bodies all fall at the same speed whatever their weight. On 18th/19th-century thinkers The 19th-century German philosopher Friedrich Nietzsche has been said to have taken nearly all of his political philosophy from Aristotle. Aristotle rigidly separated action from production, and argued for the deserved subservience of some people ("natural slaves"), and the natural superiority (virtue, arete) of others. It was Martin Heidegger, not Nietzsche, who elaborated a new interpretation of Aristotle, intended to warrant his deconstruction of scholastic and philosophical tradition. The English mathematician George Boole fully accepted Aristotle's logic, but decided "to go under, over, and beyond" it with his system of algebraic logic in his 1854 book The Laws of Thought. This gives logic a mathematical foundation with equations, enables it to solve equations as well as check validity, and allows it to handle a wider class of problems by expanding propositions of any number of terms, not just two. Charles Darwin regarded Aristotle as the most important contributor to the subject of biology. In an 1882 letter he wrote that "Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle". Also, in later editions of the book "On the Origin of Species', Darwin traced evolutionary ideas as far back as Aristotle; the text he cites is a summary by Aristotle of the ideas of the earlier Greek philosopher Empedocles. James Joyce's favoured philosopher was Aristotle, whom he considered to be "the greatest thinker of all times". Samuel Taylor Coleridge said: Everybody is born either a Platonist or an Aristotelian. Ayn Rand acknowledged Aristotle as her greatest influence and remarked that in the history of philosophy she could only recommend "three A's"—Aristotle, Aquinas, and Ayn Rand. She also regarded Aristotle as the greatest of all philosophers. Karl Marx considered Aristotle to be the "greatest thinker of antiquity", and called him a "giant thinker", a "genius", and "the great scholar". Modern rejection and rehabilitation During the 20th century, Aristotle's work was widely criticized. The philosopher Bertrand Russell argued that "almost every serious intellectual advance has had to begin with an attack on some Aristotelian doctrine". Russell called Aristotle's ethics "repulsive", and labelled his logic "as definitely antiquated as Ptolemaic astronomy". Russell stated that these errors made it difficult to do historical justice to Aristotle, until one remembered what an advance he made upon all of his predecessors. The Dutch historian of science Eduard Jan Dijksterhuis wrote that Aristotle and his predecessors showed the difficulty of science by "proceed[ing] so readily to frame a theory of such a general character" on limited evidence from their senses. In 1985, the biologist Peter Medawar could still state in "pure seventeenth century" tones that Aristotle had assembled "a strange and generally speaking rather tiresome farrago of hearsay, imperfect observation, wishful thinking and credulity amounting to downright gullibility". Hobbes rejected one of the most famous theses of Aristotle's politics, namely that human beings are naturally suited to life in a polis and do not fully realize their natures until they exercise the role of citizen. By the start of the 21st century, however, Aristotle was taken more seriously: Kukkonen noted that "In the best 20th-century scholarship Aristotle comes alive as a thinker wrestling with the full weight of the Greek philosophical tradition." Alasdair MacIntyre has attempted to reform what he calls the Aristotelian tradition in a way that is anti-elitist and capable of disputing the claims of both liberals and Nietzscheans. Kukkonen observed, too, that "that most enduring of romantic images, Aristotle tutoring the future conqueror Alexander" remained current, as in the 2004 film Alexander, while the "firm rules" of Aristotle's theory of drama have ensured a role for the Poetics in Hollywood. Biologists continue to be interested in Aristotle's thinking. Armand Marie Leroi has reconstructed Aristotle's biology, while Niko Tinbergen's four questions, based on Aristotle's four causes, are used to analyse animal behaviour; they examine function, phylogeny, mechanism, and ontogeny. Surviving works Corpus Aristotelicum The works of Aristotle that have survived from antiquity through medieval manuscript transmission are collected in the Corpus Aristotelicum. These texts, as opposed to Aristotle's lost works, are technical philosophical treatises from within Aristotle's school. Reference to them is made according to the organization of Immanuel Bekker's Royal Prussian Academy edition (Aristotelis Opera edidit Academia Regia Borussica, Berlin, 1831–1870), which in turn is based on ancient classifications of these works. Loss and preservation Aristotle wrote his works on papyrus scrolls, the common writing medium of that era. His writings are divisible into two groups: the "exoteric", intended for the public, and the "esoteric", for use within the Lyceum school. Aristotle's "lost" works stray considerably in characterization from the surviving Aristotelian corpus. Whereas the lost works appear to have been originally written with a view to subsequent publication, the surviving works mostly resemble lecture notes not intended for publication. Cicero's description of Aristotle's literary style as "a river of gold" must have applied to the published works, not the surviving notes. A major question in the history of Aristotle's works is how the exoteric writings were all lost, and how the ones now possessed came to be found. The consensus is that Andronicus of Rhodes collected the esoteric works of Aristotle's school which existed in the form of smaller, separate works, distinguished them from those of Theophrastus and other Peripatetics, edited them, and finally compiled them into the more cohesive, larger works as they are known today. Legacy Depictions Paintings Aristotle has been depicted by major artists including Lucas Cranach the Elder, Justus van Gent, Raphael, Paolo Veronese, Jusepe de Ribera, Rembrandt, and Francesco Hayez over the centuries. Among the best-known depictions is Raphael's fresco The School of Athens, in the Vatican's Apostolic Palace, where the figures of Plato and Aristotle are central to the image, at the architectural vanishing point, reflecting their importance. Rembrandt's Aristotle with a Bust of Homer, too, is a celebrated work, showing the knowing philosopher and the blind Homer from an earlier age: as the art critic Jonathan Jones writes, "this painting will remain one of the greatest and most mysterious in the world, ensnaring us in its musty, glowing, pitch-black, terrible knowledge of time." Sculptures Eponyms The Aristotle Mountains in Antarctica are named after Aristotle. He was the first person known to conjecture, in his book Meteorology, the existence of a landmass in the southern high-latitude region and called it Antarctica. Aristoteles is a crater on the Moon bearing the classical form of Aristotle's name. See also Aristotelian Society Aristotle's Biology Conimbricenses Perfectionism References Notes Citations Sources Further reading The secondary literature on Aristotle is vast. The following is only a small selection. Ackrill, J. L. (1997). Essays on Plato and Aristotle, Oxford University Press. These translations are available in several places online; see External links. Bakalis, Nikolaos. (2005). Handbook of Greek Philosophy: From Thales to the Stoics Analysis and Fragments, Trafford Publishing, . Bolotin, David (1998). An Approach to Aristotle's Physics: With Particular Attention to the Role of His Manner of Writing. Albany: SUNY Press. A contribution to our understanding of how to read Aristotle's scientific works. Burnyeat, Myles F. et al. (1979). Notes on Book Zeta of Aristotle's Metaphysics. Oxford: Sub-faculty of Philosophy. Code, Alan (1995). Potentiality in Aristotle's Science and Metaphysics, Pacific Philosophical Quarterly 76. De Groot, Jean (2014). Aristotle's Empiricism: Experience and Mechanics in the 4th century BC, Parmenides Publishing, . Frede, Michael (1987). Essays in Ancient Philosophy. Minneapolis: University of Minnesota Press. Gendlin, Eugene T. (2012). Line by Line Commentary on Aristotle's De Anima , Volume 1: Books I & II; Volume 2: Book III. The Focusing Institute. Gill, Mary Louise (1989). Aristotle on Substance: The Paradox of Unity. Princeton University Press. Jori, Alberto (2003). Aristotele, Bruno Mondadori (Prize 2003 of the "International Academy of the History of Science"), . Knight, Kelvin (2007). Aristotelian Philosophy: Ethics and Politics from Aristotle to MacIntyre, Polity Press. Lewis, Frank A. (1991). Substance and Predication in Aristotle. Cambridge University Press. Lord, Carnes (1984). Introduction to The Politics, by Aristotle. Chicago University Press. Loux, Michael J. (1991). Primary Ousia: An Essay on Aristotle's Metaphysics Ζ and Η. Ithaca, NY: Cornell University Press. Maso, Stefano (Ed.), Natali, Carlo (Ed.), Seel, Gerhard (Ed.) (2012) Reading Aristotle: Physics VII. 3: What is Alteration? Proceedings of the International ESAP-HYELE Conference, Parmenides Publishing. . [Reprinted in J. Barnes, M. Schofield, and R.R.K. Sorabji, eds.(1975). Articles on Aristotle Vol 1. Science. London: Duckworth 14–34.] Reeve, C. D. C. (2000). Substantial Knowledge: Aristotle's Metaphysics. Hackett. Scaltsas, T. (1994). Substances and Universals in Aristotle's Metaphysics. Cornell University Press. Strauss, Leo (1964). "On Aristotle's Politics", in The City and Man, Rand McNally. External links At the Internet Encyclopedia of Philosophy: At the Internet Classics Archive From the Stanford Encyclopedia of Philosophy: Collections of works At Massachusetts Institute of Technology Perseus Project at Tufts University At the University of Adelaide P. Remacle The 11-volume 1837 Bekker edition of Aristotle's Works in Greek (PDFDJVU) 384 BC births 322 BC deaths 4th-century BC mathematicians 4th-century BC philosophers 4th-century BC writers Academic philosophers Acting theorists Ancient Greek biologists Ancient Greek economists Ancient Greek epistemologists Ancient Greek ethicists Ancient Greek logicians Ancient Greek mathematicians Ancient Greek metaphilosophers Ancient Greek metaphysicians Ancient Greek philosophers Ancient Greek philosophers of language Ancient Greek philosophers of mind Ancient Greek physicists Ancient Greek political philosophers Ancient Greek philosophers of art Ancient literary critics Ancient Stagirites Aphorists Aristotelian philosophers Attic Greek writers Ancient Greek cosmologists Critical thinking Cultural critics Founders of philosophical traditions Greek male writers Greek geologists Greek meteorologists Greek social commentators Humor researchers Irony theorists Metic philosophers in Classical Athens Moral philosophers Natural philosophers Ontologists Peripatetic philosophers Philosophers and tutors of Alexander the Great Philosophers of ancient Chalcidice Philosophers of culture Philosophers of education Philosophers of ethics and morality Philosophers of history Philosophers of law Philosophers of literature Philosophers of logic Philosophers of love Philosophers of psychology Philosophers of science Philosophers of time Philosophers of sexuality Philosophers of technology Philosophical logic Philosophical theists Philosophy academics Philosophy writers Rhetoric theorists Social critics Social philosophers Students of Plato Trope theorists Virtue ethicists Virtue ethics Western culture Western philosophy Zoologists

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

340

https://en.wikipedia.org/wiki/Alain%20Connes

Alain Connes

Alain Connes (; born 1 April 1947) is a French mathematician, and a theoretical physicist, known for his contributions to the study of operator algebras and noncommutative geometry. He is a professor at the Collège de France, IHÉS, Ohio State University and Vanderbilt University. He was awarded the Fields Medal in 1982. Career Connes was an Invited Professor at the Conservatoire national des arts et métiers (2000). Research Alain Connes studies operator algebras. In his early work on von Neumann algebras in the 1970s, he succeeded in obtaining the almost complete classification of injective factors. He also formulated the Connes embedding problem. Following this, he made contributions in operator K-theory and index theory, which culminated in the Baum–Connes conjecture. He also introduced cyclic cohomology in the early 1980s as a first step in the study of noncommutative differential geometry. He was a member of Bourbaki. Connes has applied his work in areas of mathematics and theoretical physics, including number theory, differential geometry and particle physics. Awards and honours Connes was awarded the Fields Medal in 1982, the Crafoord Prize in 2001 and the gold medal of the CNRS in 2004. He was an invited speaker at the ICM in 1974 at Vancouver and in 1986 at Berkeley and a plenary speaker at the ICM in 1978 at Helsinki. He is a member of the French Academy of Sciences and several foreign academies and societies, including the Danish Academy of Sciences, Norwegian Academy of Sciences, Russian Academy of Sciences, and US National Academy of Sciences. Books Alain Connes and Matilde Marcolli, Noncommutative Geometry, Quantum Fields and Motives, Colloquium Publications, American Mathematical Society, 2007, Alain Connes, Andre Lichnerowicz, and Marcel Paul Schutzenberger, Triangle of Thought, translated by Jennifer Gage, American Mathematical Society, 2001, Jean-Pierre Changeux, and Alain Connes, Conversations on Mind, Matter, and Mathematics, translated by M. B. DeBevoise, Princeton University Press, 1998, Alain Connes, Noncommutative Geometry, Academic Press, 1994, See also Bost–Connes system Cyclic category Cyclic homology Factor (functional analysis) Higgs boson C*-algebra Noncommutative quantum field theory M-theory Groupoid Spectral triple Criticism of non-standard analysis Riemann hypothesis References External links Alain Connes Official Web Site containing downloadable papers, and his book Non-commutative geometry, . Alain Connes' Standard Model An interview with Alain Connes and a discussion about it 1947 births Living people 20th-century French mathematicians Foreign associates of the National Academy of Sciences 21st-century French mathematicians Collège de France faculty Institute for Advanced Study visiting scholars Fields Medalists Mathematical analysts Differential geometers École Normale Supérieure alumni Vanderbilt University faculty Foreign Members of the Russian Academy of Sciences Members of the French Academy of Sciences Members of the Norwegian Academy of Science and Letters Members of the Royal Danish Academy of Sciences and Letters Clay Research Award recipients

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

359

https://en.wikipedia.org/wiki/List%20of%20Atlas%20Shrugged%20characters

List of Atlas Shrugged characters

This is a list of characters in Ayn Rand's 1957 novel Atlas Shrugged. Major characters The following are major characters from the novel. Protagonists Dagny Taggart Dagny Taggart is the protagonist of the novel. She is vice-president in Charge of Operations for Taggart Transcontinental, under her brother, James Taggart. Given James' incompetence, Dagny is responsible for all the workings of the railroad. Francisco d'Anconia Francisco d'Anconia is one of the central characters in Atlas Shrugged, an owner by inheritance of the world's largest copper mining operation. He is a childhood friend, and the first love, of Dagny Taggart. A child prodigy of exceptional talents, Francisco was dubbed the "climax" of the d'Anconia line, an already prestigious family of skilled industrialists. He was a classmate of John Galt and Ragnar Danneskjöld and student of both Hugh Akston and Robert Stadler. He began working while still in school, proving that he could have made a fortune without the aid of his family's wealth and power. Later, Francisco bankrupts the d'Anconia business to put it out of others' reach. His full name is given as "Francisco Domingo Carlos Andres Sebastián d'Anconia". John Galt John Galt is the primary male hero of Atlas Shrugged. He initially appears as an unnamed menial worker for Taggart Transcontinental, who often dines with Eddie Willers in the employees' cafeteria, and leads Eddie to reveal important information about Dagny Taggart and Taggart Transcontinental. Only Eddie's side of their conversations is given in the novel. Later in the novel, the reader discovers this worker's true identity. Before working for Taggart Transcontinental, Galt worked as an engineer for the Twentieth Century Motor Company, where he secretly invented a generator of usable electric energy from ambient static electricity, but abandoned his prototype, and his employment, when dissatisfied by an easily corrupted novel system of payment. This prototype was found by Dagny Taggart and Hank Rearden. Galt himself remains concealed throughout much of the novel, working a job and living by himself, where he unites the most skillful inventors and business leaders under his leadership. Much of the book's third division is given to his broadcast speech, which presents the author's philosophy of Objectivism. Henry "Hank" Rearden Henry (known as "Hank") Rearden is one of the central characters in Atlas Shrugged. He owns the most important steel company in the United States, and invents Rearden Metal, an alloy stronger, lighter, cheaper and tougher than steel. He lives in Philadelphia with his wife Lillian, his brother Philip, and his elderly mother. Rearden represents a type of self-made man and eventually divorces Lillian, abandons his steel mills following a bloody assault by government-planted workers, and joins John Galt's strike. Eddie Willers Edwin "Eddie" Willers is the Special Assistant to the Vice-President in Charge of Operations at Taggart Transcontinental. His father and grandfather worked for the Taggarts, and himself likewise. He is completely loyal to Dagny and to Taggart Transcontinental. Willers does not possess the creative ability of Galt's associates, but matches them in moral courage and is capable of appreciating and making use of their creations. After Dagny shifts her attention and loyalty to saving the captive Galt, Willers maintains the railroad until its collapse. Ragnar Danneskjöld One of Galt's first followers, and world-famous as a pirate, who seizes relief ships sent from the United States to the People's States of Europe. He works to ensure that once those espousing Galt's philosophy are restored to their rightful place in society, they have enough capital to rebuild the world. Kept in the background for much of the book, Danneskjöld makes a personal appearance to encourage Rearden to persevere in his increasingly difficult situation, and gives him a bar of gold as compensation for the income taxes he has paid over the last several years. Danneskjöld is married to the actress Kay Ludlow; their relationship is kept hidden from the outside world, which only knows of Ludlow as a retired film star. Considered a misfit by Galt's other adherents, he views his actions as a means to speed the world along in understanding Galt's perspective. According to Barbara Branden, who was closely associated with Rand at the time the book was written, there were sections written describing Danneskjöld's adventures at sea, cut from the final published text. In a 1974 comment at a lecture, Ayn Rand admitted that Danneskjöld's name was a tribute to Victor Hugo's novel, , wherein the hero becomes the first of the Counts of Danneskjöld. In the published book, Danneskjöld is always seen through the eyes of others (Dagny Taggart or Hank Rearden), except for a brief paragraph in the very last chapter. Antagonists James Taggart The President of Taggart Transcontinental and the book's most important antagonist. Taggart is an expert influence peddler but incapable of making operational decisions on his own. He relies on his sister, Dagny Taggart, to actually run the railroad, but nonetheless opposes her in almost every endeavor because of his various anti-capitalist moral and political beliefs. In a sense, he is the antithesis of Dagny. This contradiction leads to the recurring absurdity of his life: the desire to overcome those on whom his life depends, and the horror that he will succeed at this. In the final chapters of the novel, he suffers a complete mental breakdown upon realizing that he can no longer deceive himself in this respect. Lillian Rearden The unsupportive wife of Hank Rearden, who dislikes his habits and (secretly at first) seeks to ruin Rearden to prove her own value. Lillian achieves this, when she passes information to James Taggart about her husband's affair with his sister. This information is used to blackmail Rearden to sign a Gift Certificate which delivers all the property rights of Rearden Metal to others. Lillian thereafter uses James Taggart for sexual satisfaction, until Hank abandons her. Dr. Floyd Ferris Ferris is a biologist who works as "co-ordinator" at the State Science Institute. He uses his position there to deride reason and productive achievement, and publishes a book entitled Why Do You Think You Think? He clashes on several occasions with Hank Rearden, and twice attempts to blackmail Rearden into giving up Rearden Metal. He is also one of the group of looters who tries to get Rearden to agree to the Steel Unification Plan. Ferris hosts the demonstration of the Project X weapon, and is the creator of the Ferris Persuader, a torture machine. When John Galt is captured by the looters, Ferris uses the device on Galt, but it breaks down before extracting the information Ferris wants from Galt. Ferris represents the group which uses brute force on the heroes to achieve the ends of the looters. Dr. Robert Stadler A former professor at Patrick Henry University, and along with colleague Hugh Akston, mentor to Francisco d'Anconia, John Galt and Ragnar Danneskjöld. He has since become a sell-out, one who had great promise but squandered it for social approval, to the detriment of the free. He works at the State Science Institute where all his inventions are perverted for use by the military, including a sound-based weapon known as Project X (Xylophone). He is killed when Cuffy Meigs (see below) drunkenly overloads the circuits of Project X, causing it to destroy itself and every structure and living thing in a 100-mile radius. The character was, in part, modeled on J. Robert Oppenheimer, whom Rand had interviewed for an earlier project, and his part in the creation of nuclear weapons.` To his former student Galt, Stadler represents the epitome of human evil, as the "man who knew better" but chose not to act for the good. Wesley Mouch The incompetent and treacherous lobbyist whom Hank Rearden reluctantly employs in Washington, who rises to prominence and authority throughout the novel through trading favours and disloyalty. In return for betraying Hank by helping broker the Equalization of Opportunity Bill (which, by restricting the number of businesses each person may own to one, forces Hank to divest most of his companies), he is given a senior position at the Bureau of Economic Planning and National Resources. Later in the novel he becomes its Top Co-ordinator, a position that eventually becomes Economic Dictator of the country. Mouch's mantra, whenever a problem arises from his prior policy, is to say, "I can't help it. I need wider powers." Secondary characters The following secondary characters also appear in the novel. Hugh Akston is identified as "One of the last great advocates of reason." He was a renowned philosopher and the head of the Department of Philosophy at Patrick Henry University, where he taught Francisco d'Anconia, John Galt, and Ragnar Danneskjöld. He was, along with Robert Stadler, a father figure to these three. Akston's name is so hallowed that a young lady, on hearing that Francisco had studied under him, is shocked. She thought he must have been one of those great names from an earlier century. He now works as a cook in a roadside diner, and proves extremely skillful at the job. When Dagny tracks him down, and before she discovers his true identity, he rejects her enthusiastic offer to manage the dining car services for Taggart Transcontinental. He is based on Aristotle. Jeff Allen is a tramp who stows away on a Taggart train during one of Dagny's cross-country trips. Instead of throwing him out, she allows him to ride as her guest. It is from Allen that she learns the full story behind the collapse of the Twentieth Century Motor Company (Rand's extensive metaphor for the inherent flaws of communism), as well as a hint of John Galt's true background. Calvin Atwood is owner of Atwood Light and Power Company and joins Galt's strike. Mayor Bascom is the mayor of Rome, Wisconsin, who reveals part of the history of the Twentieth Century Motor Company. Dr. Blodgett is the scientist who pulls the lever to demonstrate Project X. Orren Boyle is the head of Associated Steel, antithesis of Hank Rearden and a friend of James Taggart. He is an investor in the San Sebastián Mines. He disappears from the story after having a nervous breakdown following the failed 'unification' of the steel industry. Laura Bradford is an actress and Kip Chalmers' mistress. She is one of the passengers on his train, and dies in the Taggart Tunnel disaster. Bill Brent is the chief dispatcher for the Colorado Division of Taggart Transcontinental, who tries to prevent the Taggart Tunnel disaster. Cherryl Brooks is a dime store shopgirl who marries James Taggart after a chance encounter in her store the night the John Galt Line was falsely deemed his greatest success. She marries him thinking he is the heroic person behind Taggart Transcontinental. Cherryl is at first harsh towards Dagny, having believed Jim Taggart's descriptions of his sister, until she questions employees of the railroad. Upon learning that her scorn had been misdirected, Cherryl puts off apologizing to Dagny out of shame, but eventually admits to Dagny that when she married Jim, she thought he had the heroic qualities that she had looked up to - she thought she was marrying someone like Dagny. Shortly after making this admission, she commits suicide by jumping over a stone parapet and into the river, unable to live with her evil husband and seeing no way to escape him. Millie Bush was "a mean, ugly little eight-year-old" girl voted to receive gold braces to straighten her teeth by the Marxist "family" committee who determined how pay was allocated at The Twentieth Century Motor Company. Her teeth are later knocked out by a man denied an allowance by the committee to purchase the things he valued. Emma Chalmers, Kip Chalmers' mother, gains some influence after his death. Known as "Kip's Ma," she starts a soybean-growing project in Louisiana and commandeers thousands of railroad freight cars to move the harvest. As a result, the year's wheat crop from Minnesota never reaches the rest of the country, but instead rots in storage; also, the soybean crop is lost, having been reaped too early. Kip Chalmers is a Washington man who has decided to run for election as Legislator from California. On the way to a campaign rally, the Taggart Transcontinental train that is carrying him encounters a split rail, resulting in the destruction of its diesel engine. His demands lead to a coal-burning steam engine being attached to his train in its stead and used to pull it through an eight-mile tunnel. The result is the suffocation of all passengers and the destruction of the Taggart Tunnel. Dan Conway is the middle-aged president of the Phoenix-Durango railroad. Running a railroad is just about the only thing he knows. When the Anti-dog-eat-dog Rule is used to drive his business out of Colorado, he loses the will to fight, and resigns himself to a quiet life of books and fishing. He is not one of those who joined John Galt's strike, his resignation being a personal choice of his own. Ken Danagger owns Danagger Coal in Pennsylvania. He helps Hank Rearden illegally make Rearden Metal, then later decides to quit and join Galt's strike moments before Dagny arrives to try to persuade him otherwise. Quentin Daniels is an enterprising engineer hired by Dagny Taggart to reconstruct John Galt's motor. Partway through this process, Quentin withdraws his effort for the same reasons John Galt himself had. Dagny's pursuit of Quentin leads her to Galt's Gulch. Galt recognizes in him a younger version of himself, having emulated both Galt's achievements in physics and Galt's social reasoning. Sebastian d'Anconia was the 16th (or 17th) Century founder of the d'Anconia dynasty. Escaped from Spain because of expressing his opinions too freely and coming in conflict with the Inquisition, leaving behind a palace and his beloved. Started a small mine in South America, which became the beginning of a mining empire and a new fortune (and a new palace). Eventually sent for his beloved who had waited for him many years. He is the role model which Francisco d'Anconia looks to, as Dagny Taggart looks to Nathaniel Taggart. Francisco remarks that their respective ancestors would have liked each other. Balph Eubank is called "the literary leader of the age", despite the fact that no book he has written has sold more than 3,000 copies. He complains that it is disgraceful that artists are treated as peddlers, and that there should be a law limiting the sales of books to 10,000 copies. He is a misogynist who thinks it disgusting that Dagny Taggart is a railroad vice-president. The Fishwife is one of the strikers, who earns her living by providing the fish for Hammond's grocery market; she is described as having "dark, disheveled hair and large eyes", and is a writer. Galt says she "wouldn't be published outside. She believes that when one deals with words, one deals with the mind." According to Barbara Branden in her book The Passion of Ayn Rand, "The Fishwife is Ayn's Hitchcock-like appearance in Atlas Shrugged." So says too Leonard Peikoff. Lawrence Hammond runs Hammond Cars in Colorado, one of the few companies in existence that still produces top-quality vehicles. He eventually quits and joins the strike. Richard Halley is Dagny Taggart's favorite composer, who mysteriously disappeared after the evening of his greatest triumph. Halley spent years as a struggling and unappreciated composer. At age 24, his opera Phaethon was performed for the first time, to an audience who booed and heckled it. After 19 years, Phaethon was performed again, but this time it was received to the greatest ovation the opera house had ever heard. The following day, Halley retired, sold the rights to his music, and disappeared. It is later revealed that he has joined the strike and settled in Galt's Gulch. Mrs. William Hastings is the widow of the chief engineer at the Twentieth Century Motor Company. Her husband quit shortly after Galt did and joined the strike some years later. Her lead allows Dagny to find Hugh Akston. Dr. Thomas Hendricks is a famous brain surgeon who developed a new method of preventing strokes. He joined Galt's strike when the American medical system was put under government control. Tinky Holloway is one of the "looters" and is frequently referred to and quoted by other characters in the story, but he has only one major appearance: during the Washington meeting with Hank Rearden. Lee Hunsacker is in charge of a company called Amalgamated Service when takes over the Twentieth Century Motor Company. He files a lawsuit that eventually leads to Midas Mulligan and Judge Narragansett joining the strike. A failed businessman, he laments constantly that no-one ever gave him a chance. Gwen Ives is Hank Rearden's secretary, described as being in her late twenties and remaining calm and professional despite the chaos that threatens his business. When Rearden abandons his mills and joins Galt's strike, she and many other employees do the same. Gilbert Keith-Worthing is a British novelist of erstwhile fame, now neglected but still considered a "walking classic," and a proponent of the idea that freedom is an illusion. Kip Chalmers brings him along on the train to California, "for no reason that either of them could discover"; he dies in the Taggart Tunnel disaster. Owen Kellogg is Assistant to the Manager of the Taggart Terminal in New York. He catches Dagny Taggart's eye as one of the few competent men on staff. After seeing the sorry state of the Ohio Division, she decides to make him its new Superintendent. However, as soon as she returns to New York, Kellogg informs her that he is quitting his job. Owen Kellogg eventually reaches, and settles in, Galt's Gulch. Fred Kinnan is a labor leader and member of the looter cabal. Unlike the others, however, Kinnan is straightforward and honest about his purpose. Kinnan is the only one to openly state the true motivations of himself and his fellow conspirators. At the end of Galt's three-hour speech, he expresses admiration for the man, as he says what he means. Despite this, Kinnan admits that he is one of the people Galt is out to destroy. Paul Larkin is an unsuccessful, middle-aged businessman, a friend of the Rearden family. He meets with the other Looters to work out a plan to bring Rearden down. James Taggart knows he is friends with Hank Rearden and challenges his loyalty, and Larkin assures Taggart that he will go along with them. Eugene Lawson heads the Community Bank of Madison, then gets a job with the government when it his bank goes bankrupt. One of the looter's cabal, he is a collectivist who abhors production and money-making. Mort Liddy is a hack composer who writes trite scores for movies and modern symphonies to which no one listens. He believes melody is a primitive vulgarity. He is one of Lillian Rearden's friends and a member of the cultural elite. Clifton Locey is a friend of Jim Taggart who takes the position of vice-president of operation when Dagny Taggart quits. Pat Logan is the engineer on the first run of the John Galt Line. He later strikes. Kay Ludlow is a beautiful actress who quit Holywood because of the roles she was given and married secretly the pirate Ragnar Danneskjöld. Dick McNamara is a contractor who finished the San Sebastian Line. Dagny Taggart plans to hire him to lay the new Rearden Metal track for the Rio Norte Line, but before she does so, he mysteriously disappears. She later discovers that he has joined the strike and settled in Galt's Gulch. Cuffy Meigs is the Director of Unification for the railroad business. He carries a pistol and a lucky rabbit's foot, and he dresses in a military uniform, and has been described as "impervious to thought". Meigs seizes control of Project X and accidentally destroys it, demolishing the country's last railroad bridge across the Mississippi River and killing himself, his men, and Dr. Stadler. Dave Mitchum is a state-hired superintendent of the Colorado Division of Taggart Transcontinental. He is partially responsible for the Taggart Tunnel disaster. Chick Morrison holds the position of "Morale Conditioner" in the government. He quits when society begins to collapse and flees to a stronghold in Tennessee. His fellow looters consider it unlikely that he will survive. Horace Bussby Mowen is the president of the Amalgamated Switch and Signal Company, Inc. of Connecticut. He is a businessman who sees nothing wrong with the moral code that is destroying society and would never dream of saying he is in business for any reason other than the good of society. Dagny Taggart hires Mowen to produce switches made of Rearden Metal. He is reluctant to build anything with this unproven technology, and has to be cajoled into accepting the contract. When pressured by public opinion, he discontinues production of the switches, forcing Dagny to find an alternative source. Midas Mulligan is a wealthy banker who mysteriously disappeared in protest after he was given a court order to lend money to an incompetent applicant. When the order came down, he liquidated his entire business, paid off his depositors, and joined Galt's strike. He is the legal owner of the land where Galt's Gulch is located. Mulligan's birth name was Michael, but he had it legally changed after a news article called him "Midas" in a derogatory fashion, which Mulligan took as a compliment. Judge Narragansett is an American jurist who ruled in favor of Midas Mulligan during the case brought against him by the incompetent loan applicant. When Narragansett's ruling was reversed on appeal, he retired and joined the strike. At the end of the novel, he is seen editing the United States Constitution, crossing out the contradicting amendments of it and adding an amendment to prohibit Congress from passing laws that restrain freedom of trade. Ben Nealy is a railroad contractor whom Dagny Taggart hires to replace the track on the Rio Norte Line with Rearden Metal. Nealy is incompetent, but Dagny can find no one better in all the country. Nealy believes that anything can get done with enough muscle power. He sees no role for intelligence in human achievement. He relies on Dagny and Ellis Wyatt to run things, and resents them for doing it, because it appears to him like they are just bossing people around. Ted Nielsen is the head of Nielsen Motors. He eventually goes on strike, along with most of the other industrialist "producer" types, by closing his motor factory. Dagny later finds him when she visits Galt's Gulch for the first time. Betty Pope is a wealthy socialite who is having a meaningless sexual affair with James Taggart. She is deliberately crude in a way that casts ridicule on her high social position. Dr. Potter holds some undefined position with the State Science Institute. He is sent to try to obtain the rights to Rearden Metal. Dr. Simon Pritchett is the prestigious head of the Department of Philosophy at Patrick Henry University and is considered the leading philosopher of the age. He believes that man is nothing but a collection of chemicals, reason is a superstition, it is futile to seek meaning in life, and the duty of a philosopher is to show that nothing can be understood. Rearden's mother, whose name is not mentioned, lives with Rearden at his home in Philadelphia. She is involved in charity work, and berates Rearden whenever she can. She dotes on her weak son Philip Rearden. Philip Rearden is the younger brother of Hank Rearden. He lives in his brother's home in Philadelphia and is completely dependent on him. He is resentful of his brother's charity. Dwight Sanders owns Sanders Aircraft, a producer of high-quality airplanes, and joins the strike. Bertram Scudder is an editorial writer for the magazine The Future. He typically bashes business and businessmen, but he never says anything specific in his articles, relying on innuendo, sneers, and denunciation. He wrote a hatchet job on Hank Rearden called The Octopus. He is also vocal in support of the Equalization of Opportunity Bill. Scudder claims that the most important thing in life is "brother love" but seems to have nothing but hatred for those around him. He loses his job after Dagny Taggart reveals her affair with Hank Rearden over air on his radio show. Claude Slagenhop is president of political organization Friends of Global Progress and one of Lillian Rearden's friends. He believes that ideas are just air, that this is no time for talk, but for action. Global Progress is a sponsor of the Equalization of Opportunity Bill. Gerald and Ivy Starnes are the two surviving children of Jed Starnes, the founder of the Twentieth Century Motor Company. Together with their since-deceased brother Eric, they instituted a communistic payment-and-benefits program that drove the company into bankruptcy. Gerald, a dying alcoholic, and Ivy, a pseudo-Buddhist ascetic, continue to insist that the plan was perfect and that the failure of their father's company was entirely due to the workers. Eric was a weak, attention-seeking man with a pathological desire to be loved. He committed suicide after the woman he loved married another man. Gerald claims that he always acted for the good of the employees, but he was vain and incompetent and often threw lavish parties using company funds. Ivy, on the other hand, is described as a sadist who relishes seeing others in poverty, but who has no desire for wealth of her own. Andrew Stockton runs the Stockton Foundry in Stockton, Colorado. When he joins the strike, he opens a foundry in Galt's Gulch. Nathaniel "Nat" Taggart was the founder of Taggart Transcontinental. He built his railroad without any government handouts, and ran the business for no other reason than to turn a profit. He began as a penniless adventurer and ended up as one of the wealthiest men in the country. He never earned money by force or fraud (except for bribing government officials and throwing an opponent down a flight of stairs), and never apologized for becoming wealthy and successful. He was one of the most hated men of his time. Dagny is often inspired by looking at a statue of Nat Taggart at the railroad headquarters, and draws a dollar sign on its base as a signal to Francisco when she is ready to join Galt's strike. It is suspected that he is modeled after James Jerome Hill, builder of the Great Northern Railroad. Mr. Thompson is the "Head of the State" for the United States. He is not particularly intelligent and has a very undistinguished look. He knows politics, however, and is a master of public relations and back-room deals. Rand's notes indicate that she modeled him on President Harry S. Truman, and that she deliberately decided not to call him "President of the United States" as this title has "honorable connotations" which the character does not deserve. Lester Tuck is the campaign manager for Kip Chalmers and one of his guests on the train trip to California. He dies in the Taggart Tunnel disaster. Clem Weatherby is a government representative on the board of directors of Taggart Transcontinental. Dagny considers him the least bad of the government representatives, since he does have some real knowledge on the running of trains. She notices, however, that he is the least appreciated by his own bosses. The Wet Nurse (Tony) is a young bureaucrat sent by the government to watch over Rearden's mills. Though he starts out as a cynical follower of the looters' code, his experience at the mills transforms him, and he comes to respect and admire the producers. He is shot attempting to inform Hank Rearden about a government plot, but does succeed in warning Rearden just before he dies. Ellis Wyatt is the head of Wyatt Oil. He has almost single-handedly revived the economy of Colorado by discovering a new process for extracting more oil from what were thought to be exhausted oil wells. When first introduced, he is aggressive towards Dagny, whom he does not yet know and whom he blames for what are, in fact, her brother's policies which directly threaten his business. When the government passes laws and decrees which make it impossible for him to continue, he sets all his oil wells on fire, leaving a single note: "I am leaving it as I found it. Take over. It's yours." One particular burning well that resists all efforts to extinguish it becomes known as "Wyatt's Torch". Later Dagny meets him in Galt's Gulch. Footnotes Notes Citations General references External links Website with comprehensive list of individuals mentioned in Atlas Shrugged Fictional socialites Lists of literary characters Literary characters introduced in 1957

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

569

https://en.wikipedia.org/wiki/Anthropology

Anthropology

Anthropology is the scientific study of humanity, concerned with human behavior, human biology, cultures, societies, and linguistics, in both the present and past, including past human species. Social anthropology studies patterns of behaviour, while cultural anthropology studies cultural meaning, including norms and values. A portmanteau sociocultural anthropology is commonly used today. Linguistic anthropology studies how language influences social life. Biological or physical anthropology studies the biological development of humans. Archaeological anthropology, often termed as 'anthropology of the past', studies human activity through investigation of physical evidence. It is considered a branch of anthropology in North America and Asia, while in Europe archaeology is viewed as a discipline in its own right or grouped under other related disciplines, such as history. Etymology The abstract noun anthropology is first attested in reference to history. Its present use first appeared in Renaissance Germany in the works of Magnus Hundt and Otto Casmann. Their New Latin derived from the combining forms of the Greek words ánthrōpos (, "human") and lógos (, "study"). (Its adjectival form appeared in the works of Aristotle.) It began to be used in English, possibly via French , by the early 18th century. History Through the 19th century In 1647, the Bartholins, founders of the University of Copenhagen, defined as follows: Sporadic use of the term for some of the subject matter occurred subsequently, such as the use by Étienne Serres in 1839 to describe the natural history, or paleontology, of man, based on comparative anatomy, and the creation of a chair in anthropology and ethnography in 1850 at the French National Museum of Natural History by Jean Louis Armand de Quatrefages de Bréau. Various short-lived organizations of anthropologists had already been formed. The Société Ethnologique de Paris, the first to use the term ethnology, was formed in 1839. Its members were primarily anti-slavery activists. When slavery was abolished in France in 1848, the Société was abandoned. Meanwhile, the Ethnological Society of New York, currently the American Ethnological Society, was founded on its model in 1842, as well as the Ethnological Society of London in 1843, a break-away group of the Aborigines' Protection Society. These anthropologists of the times were liberal, anti-slavery, and pro-human-rights activists. They maintained international connections. Anthropology and many other current fields are the intellectual results of the comparative methods developed in the earlier 19th century. Theorists in such diverse fields as anatomy, linguistics, and ethnology, making feature-by-feature comparisons of their subject matters, were beginning to suspect that similarities between animals, languages, and folkways were the result of processes or laws unknown to them then. For them, the publication of Charles Darwin's On the Origin of Species was the epiphany of everything they had begun to suspect. Darwin himself arrived at his conclusions through comparison of species he had seen in agronomy and in the wild. Darwin and Wallace unveiled evolution in the late 1850s. There was an immediate rush to bring it into the social sciences. Paul Broca in Paris was in the process of breaking away from the Société de biologie to form the first of the explicitly anthropological societies, the Société d'Anthropologie de Paris, meeting for the first time in Paris in 1859. When he read Darwin, he became an immediate convert to Transformisme, as the French called evolutionism. His definition now became "the study of the human group, considered as a whole, in its details, and in relation to the rest of nature". Broca, being what today would be called a neurosurgeon, had taken an interest in the pathology of speech. He wanted to localize the difference between man and the other animals, which appeared to reside in speech. He discovered the speech center of the human brain, today called Broca's area after him. His interest was mainly in Biological anthropology, but a German philosopher specializing in psychology, Theodor Waitz, took up the theme of general and social anthropology in his six-volume work, entitled Die Anthropologie der Naturvölker, 1859–1864. The title was soon translated as "The Anthropology of Primitive Peoples". The last two volumes were published posthumously. Waitz defined anthropology as "the science of the nature of man". Following Broca's lead, Waitz points out that anthropology is a new field, which would gather material from other fields, but would differ from them in the use of comparative anatomy, physiology, and psychology to differentiate man from "the animals nearest to him". He stresses that the data of comparison must be empirical, gathered by experimentation. The history of civilization, as well as ethnology, are to be brought into the comparison. It is to be presumed fundamentally that the species, man, is a unity, and that "the same laws of thought are applicable to all men". Waitz was influential among British ethnologists. In 1863, the explorer Richard Francis Burton and the speech therapist James Hunt broke away from the Ethnological Society of London to form the Anthropological Society of London, which henceforward would follow the path of the new anthropology rather than just ethnology. It was the 2nd society dedicated to general anthropology in existence. Representatives from the French Société were present, though not Broca. In his keynote address, printed in the first volume of its new publication, The Anthropological Review, Hunt stressed the work of Waitz, adopting his definitions as a standard. Among the first associates were the young Edward Burnett Tylor, inventor of cultural anthropology, and his brother Alfred Tylor, a geologist. Previously Edward had referred to himself as an ethnologist; subsequently, an anthropologist. Similar organizations in other countries followed: The Anthropological Society of Madrid (1865), the American Anthropological Association in 1902, the Anthropological Society of Vienna (1870), the Italian Society of Anthropology and Ethnology (1871), and many others subsequently. The majority of these were evolutionists. One notable exception was the Berlin Society for Anthropology, Ethnology, and Prehistory (1869) founded by Rudolph Virchow, known for his vituperative attacks on the evolutionists. Not religious himself, he insisted that Darwin's conclusions lacked empirical foundation. During the last three decades of the 19th century, a proliferation of anthropological societies and associations occurred, most independent, most publishing their own journals, and all international in membership and association. The major theorists belonged to these organizations. They supported the gradual osmosis of anthropology curricula into the major institutions of higher learning. By 1898, 48 educational institutions in 13 countries had some curriculum in anthropology. None of the 75 faculty members were under a department named anthropology. 20th and 21st centuries This meager statistic expanded in the 20th century to comprise anthropology departments in the majority of the world's higher educational institutions, many thousands in number. Anthropology has diversified from a few major subdivisions to dozens more. Practical anthropology, the use of anthropological knowledge and technique to solve specific problems, has arrived; for example, the presence of buried victims might stimulate the use of a forensic archaeologist to recreate the final scene. The organization has reached a global level. For example, the World Council of Anthropological Associations (WCAA), "a network of national, regional and international associations that aims to promote worldwide communication and cooperation in anthropology", currently contains members from about three dozen nations. Since the work of Franz Boas and Bronisław Malinowski in the late 19th and early 20th centuries, social anthropology in Great Britain and cultural anthropology in the US have been distinguished from other social sciences by their emphasis on cross-cultural comparisons, long-term in-depth examination of context, and the importance they place on participant-observation or experiential immersion in the area of research. Cultural anthropology, in particular, has emphasized cultural relativism, holism, and the use of findings to frame cultural critiques. This has been particularly prominent in the United States, from Boas' arguments against 19th-century racial ideology, through Margaret Mead's advocacy for gender equality and sexual liberation, to current criticisms of post-colonial oppression and promotion of multiculturalism. Ethnography is one of its primary research designs as well as the text that is generated from anthropological fieldwork. In Great Britain and the Commonwealth countries, the British tradition of social anthropology tends to dominate. In the United States, anthropology has traditionally been divided into the four field approach developed by Franz Boas in the early 20th century: biological or physical anthropology; social, cultural, or sociocultural anthropology; and archaeological anthropology; plus linguistic anthropology. These fields frequently overlap but tend to use different methodologies and techniques. European countries with overseas colonies tended to practice more ethnology (a term coined and defined by Adam F. Kollár in 1783). It is sometimes referred to as sociocultural anthropology in the parts of the world that were influenced by the European tradition. Fields Anthropology is a global discipline involving humanities, social sciences and natural sciences. Anthropology builds upon knowledge from natural sciences, including the discoveries about the origin and evolution of Homo sapiens, human physical traits, human behavior, the variations among different groups of humans, how the evolutionary past of Homo sapiens has influenced its social organization and culture, and from social sciences, including the organization of human social and cultural relations, institutions, social conflicts, etc. Early anthropology originated in Classical Greece and Persia and studied and tried to understand observable cultural diversity, such as by Al-Biruni of the Islamic Golden Age. As such, anthropology has been central in the development of several new (late 20th century) interdisciplinary fields such as cognitive science, global studies, and various ethnic studies. According to Clifford Geertz, Sociocultural anthropology has been heavily influenced by structuralist and postmodern theories, as well as a shift toward the analysis of modern societies. During the 1970s and 1990s, there was an epistemological shift away from the positivist traditions that had largely informed the discipline. During this shift, enduring questions about the nature and production of knowledge came to occupy a central place in cultural and social anthropology. In contrast, archaeology and biological anthropology remained largely positivist. Due to this difference in epistemology, the four sub-fields of anthropology have lacked cohesion over the last several decades. Sociocultural Sociocultural anthropology draws together the principle axes of cultural anthropology and social anthropology. Cultural anthropology is the comparative study of the manifold ways in which people make sense of the world around them, while social anthropology is the study of the relationships among individuals and groups. Cultural anthropology is more related to philosophy, literature and the arts (how one's culture affects the experience for self and group, contributing to a more complete understanding of the people's knowledge, customs, and institutions), while social anthropology is more related to sociology and history. In that, it helps develop an understanding of social structures, typically of others and other populations (such as minorities, subgroups, dissidents, etc.). There is no hard-and-fast distinction between them, and these categories overlap to a considerable degree. Inquiry in sociocultural anthropology is guided in part by cultural relativism, the attempt to understand other societies in terms of their own cultural symbols and values. Accepting other cultures in their own terms moderates reductionism in cross-cultural comparison. This project is often accommodated in the field of ethnography. Ethnography can refer to both a methodology and the product of ethnographic research, i.e. an ethnographic monograph. As a methodology, ethnography is based upon long-term fieldwork within a community or other research site. Participant observation is one of the foundational methods of social and cultural anthropology. Ethnology involves the systematic comparison of different cultures. The process of participant-observation can be especially helpful to understanding a culture from an emic (conceptual, vs. etic, or technical) point of view. The study of kinship and social organization is a central focus of sociocultural anthropology, as kinship is a human universal. Sociocultural anthropology also covers economic and political organization, law and conflict resolution, patterns of consumption and exchange, material culture, technology, infrastructure, gender relations, ethnicity, childrearing and socialization, religion, myth, symbols, values, etiquette, worldview, sports, music, nutrition, recreation, games, food, festivals, and language (which is also the object of study in linguistic anthropology). Comparison across cultures is a key element of method in sociocultural anthropology, including the industrialized (and de-industrialized) West. The Standard Cross-Cultural Sample (SCCS) includes 186 such cultures. Biological Biological anthropology and physical anthropology are synonymous terms to describe anthropological research focused on the study of humans and non-human primates in their biological, evolutionary, and demographic dimensions. It examines the biological and social factors that have affected the evolution of humans and other primates, and that generate, maintain or change contemporary genetic and physiological variation. Archaeological Archaeology is the study of the human past through its material remains. Artifacts, faunal remains, and human altered landscapes are evidence of the cultural and material lives of past societies. Archaeologists examine material remains in order to deduce patterns of past human behavior and cultural practices. Ethnoarchaeology is a type of archaeology that studies the practices and material remains of living human groups in order to gain a better understanding of the evidence left behind by past human groups, who are presumed to have lived in similar ways. Linguistic Linguistic anthropology (not to be confused with anthropological linguistics) seeks to understand the processes of human communications, verbal and non-verbal, variation in language across time and space, the social uses of language, and the relationship between language and culture. It is the branch of anthropology that brings linguistic methods to bear on anthropological problems, linking the analysis of linguistic forms and processes to the interpretation of sociocultural processes. Linguistic anthropologists often draw on related fields including sociolinguistics, pragmatics, cognitive linguistics, semiotics, discourse analysis, and narrative analysis. Ethnography Ethnography is a method of analysing social or cultural interaction. It often involves participant observation though an ethnographer may also draw from texts written by participants of in social interactions. Ethnography views first-hand experience and social context as important. Tim Ingold distinguishes ethnography from anthropology arguing that anthropology tries to construct general theories of human experience, applicable in general and novel settings, while ethnography concerns itself with fidelity. He argues that the anthropologist must make his writing consistent with their understanding of literature and other theory, but notes that ethnography may be of use to the anthropologists and the fields inform one another. Key topics by field: sociocultural Art, media, music, dance and film Art One of the central problems in the anthropology of art concerns the universality of 'art' as a cultural phenomenon. Several anthropologists have noted that the Western categories of 'painting', 'sculpture', or 'literature', conceived as independent artistic activities, do not exist, or exist in a significantly different form, in most non-Western contexts. To surmount this difficulty, anthropologists of art have focused on formal features in objects which, without exclusively being 'artistic', have certain evident 'aesthetic' qualities. Boas' Primitive Art, Claude Lévi-Strauss' The Way of the Masks (1982) or Geertz's 'Art as Cultural System' (1983) are some examples in this trend to transform the anthropology of 'art' into an anthropology of culturally specific 'aesthetics'. Media Media anthropology (also known as the anthropology of media or mass media) emphasizes ethnographic studies as a means of understanding producers, audiences, and other cultural and social aspects of mass media. The types of ethnographic contexts explored range from contexts of media production (e.g., ethnographies of newsrooms in newspapers, journalists in the field, film production) to contexts of media reception, following audiences in their everyday responses to media. Other types include cyber anthropology, a relatively new area of internet research, as well as ethnographies of other areas of research which happen to involve media, such as development work, social movements, or health education. This is in addition to many classic ethnographic contexts, where media such as radio, the press, new media, and television have started to make their presences felt since the early 1990s. Music Ethnomusicology is an academic field encompassing various approaches to the study of music (broadly defined), that emphasize its cultural, social, material, cognitive, biological, and other dimensions or contexts instead of or in addition to its isolated sound component or any particular repertoire. Ethnomusicology can be used in a wide variety of fields, such as teaching, politics, cultural anthropology etc.  While the origins of ethnomusicology date back to the 18th and 19th centuries, it was formally introduced as “ethnomusicology” by Dutch scholar Jaap Kunst around 1950. Later, the influence of study in this area spawned the creation of the periodical Ethnomusicology and the Society of Ethnomusicology. Visual Visual anthropology is concerned, in part, with the study and production of ethnographic photography, film and, since the mid-1990s, new media. While the term is sometimes used interchangeably with ethnographic film, visual anthropology also encompasses the anthropological study of visual representation, including areas such as performance, museums, art, and the production and reception of mass media. Visual representations from all cultures, such as sandpaintings, tattoos, sculptures and reliefs, cave paintings, scrimshaw, jewelry, hieroglyphics, paintings, and photographs are included in the focus of visual anthropology. Economic, political economic, applied and development Economic Economic anthropology attempts to explain human economic behavior in its widest historic, geographic and cultural scope. It has a complex relationship with the discipline of economics, of which it is highly critical. Its origins as a sub-field of anthropology begin with the Polish-British founder of anthropology, Bronisław Malinowski, and his French compatriot, Marcel Mauss, on the nature of gift-giving exchange (or reciprocity) as an alternative to market exchange. Economic Anthropology remains, for the most part, focused upon exchange. The school of thought derived from Marx and known as Political Economy focuses on production, in contrast. Economic anthropologists have abandoned the primitivist niche they were relegated to by economists, and have now turned to examine corporations, banks, and the global financial system from an anthropological perspective. Political economy Political economy in anthropology is the application of the theories and methods of historical materialism to the traditional concerns of anthropology, including, but not limited to, non-capitalist societies. Political economy introduced questions of history and colonialism to ahistorical anthropological theories of social structure and culture. Three main areas of interest rapidly developed. The first of these areas was concerned with the "pre-capitalist" societies that were subject to evolutionary "tribal" stereotypes. Sahlin's work on hunter-gatherers as the "original affluent society" did much to dissipate that image. The second area was concerned with the vast majority of the world's population at the time, the peasantry, many of whom were involved in complex revolutionary wars such as in Vietnam. The third area was on colonialism, imperialism, and the creation of the capitalist world-system. More recently, these political economists have more directly addressed issues of industrial (and post-industrial) capitalism around the world. Applied Applied anthropology refers to the application of the method and theory of anthropology to the analysis and solution of practical problems. It is a "complex of related, research-based, instrumental methods which produce change or stability in specific cultural systems through the provision of data, initiation of direct action, and/or the formulation of policy". More simply, applied anthropology is the practical side of anthropological research; it includes researcher involvement and activism within the participating community. It is closely related to development anthropology (distinct from the more critical anthropology of development). Development Anthropology of development tends to view development from a critical perspective. The kind of issues addressed and implications for the approach simply involve pondering why, if a key development goal is to alleviate poverty, is poverty increasing? Why is there such a gap between plans and outcomes? Why are those working in development so willing to disregard history and the lessons it might offer? Why is development so externally driven rather than having an internal basis? In short, why does so much planned development fail? Kinship, feminism, gender and sexuality Kinship Kinship can refer both to the study of the patterns of social relationships in one or more human cultures, or it can refer to the patterns of social relationships themselves. Over its history, anthropology has developed a number of related concepts and terms, such as "descent", "descent groups", "lineages", "affines", "cognates", and even "fictive kinship". Broadly, kinship patterns may be considered to include people related both by descent (one's social relations during development), and also relatives by marriage. Within kinship you have two different families. People have their biological families and it is the people they share DNA with. This is called consanguineal relations or "blood ties". People can also have a chosen family Finding Connection Through "Chosen Family" in which they chose who they want to be a part of their family. In some cases people are closer with their chosen family more than with their biological families. Feminist Feminist anthropology is a four field approach to anthropology (archeological, biological, cultural, linguistic) that seeks to reduce male bias in research findings, anthropological hiring practices, and the scholarly production of knowledge. Anthropology engages often with feminists from non-Western traditions, whose perspectives and experiences can differ from those of white feminists of Europe, America, and elsewhere. From the perspective of the Western world, historically such 'peripheral' perspectives have been ignored, observed only from an outsider perspective, and regarded as less-valid or less-important than knowledge from the Western world. Exploring and addressing that double bias against women from marginalized racial or ethnic groups is of particular interest in intersectional feminist anthropology. Feminist anthropologists have stated that their publications have contributed to anthropology, along the way correcting against the systemic biases beginning with the "patriarchal origins of anthropology (and (academia)" and note that from 1891 to 1930 doctorates in anthropology went to males more than 85%, more than 81% were under 35, and only 7.2% to anyone over 40 years old, thus reflecting an age gap in the pursuit of anthropology by first-wave feminists until later in life. This correction of systemic bias may include mainstream feminist theory, history, linguistics, archaeology, and anthropology. Feminist anthropologists are often concerned with the construction of gender across societies. Gender constructs are of particular interest when studying sexism. According to St. Clair Drake, Vera Mae Green was, until "[w]ell into the 1960s", the only African-American female anthropologist who was also a Caribbeanist. She studied ethnic and family relations in the Caribbean as well as the United States, and thereby tried to improve the way black life, experiences, and culture were studied. However, Zora Neale Hurston, although often primarily considered to be a literary author, was trained in anthropology by Franz Boas, and published Tell my Horse about her "anthropological observations" of voodoo in the Caribbean (1938). Feminist anthropology is inclusive of the anthropology of birth as a specialization, which is the anthropological study of pregnancy and childbirth within cultures and societies. Medical, nutritional, psychological, cognitive and transpersonal Medical Medical anthropology is an interdisciplinary field which studies "human health and disease, health care systems, and biocultural adaptation". It is believed that William Caudell was the first to discover the field of medical anthropology. Currently, research in medical anthropology is one of the main growth areas in the field of anthropology as a whole. It focuses on the following six basic fields: Other subjects that have become central to medical anthropology worldwide are violence and social suffering (Farmer, 1999, 2003; Beneduce, 2010) as well as other issues that involve physical and psychological harm and suffering that are not a result of illness. On the other hand, there are fields that intersect with medical anthropology in terms of research methodology and theoretical production, such as cultural psychiatry and transcultural psychiatry or ethnopsychiatry. Nutritional Nutritional anthropology is a synthetic concept that deals with the interplay between economic systems, nutritional status and food security, and how changes in the former affect the latter. If economic and environmental changes in a community affect access to food, food security, and dietary health, then this interplay between culture and biology is in turn connected to broader historical and economic trends associated with globalization. Nutritional status affects overall health status, work performance potential, and the overall potential for economic development (either in terms of human development or traditional western models) for any given group of people. Psychological Psychological anthropology is an interdisciplinary subfield of anthropology that studies the interaction of cultural and mental processes. This subfield tends to focus on ways in which humans' development and enculturation within a particular cultural group – with its own history, language, practices, and conceptual categories – shape processes of human cognition, emotion, perception, motivation, and mental health. It also examines how the understanding of cognition, emotion, motivation, and similar psychological processes inform or constrain our models of cultural and social processes. Cognitive Cognitive anthropology seeks to explain patterns of shared knowledge, cultural innovation, and transmission over time and space using the methods and theories of the cognitive sciences (especially experimental psychology and evolutionary biology) often through close collaboration with historians, ethnographers, archaeologists, linguists, musicologists and other specialists engaged in the description and interpretation of cultural forms. Cognitive anthropology is concerned with what people from different groups know and how that implicit knowledge changes the way people perceive and relate to the world around them. Transpersonal Transpersonal anthropology studies the relationship between altered states of consciousness and culture. As with transpersonal psychology, the field is much concerned with altered states of consciousness (ASC) and transpersonal experience. However, the field differs from mainstream transpersonal psychology in taking more cognizance of cross-cultural issues – for instance, the roles of myth, ritual, diet, and texts in evoking and interpreting extraordinary experiences. Political and legal Political Political anthropology concerns the structure of political systems, looked at from the basis of the structure of societies. Political anthropology developed as a discipline concerned primarily with politics in stateless societies, a new development started from the 1960s, and is still unfolding: anthropologists started increasingly to study more "complex" social settings in which the presence of states, bureaucracies and markets entered both ethnographic accounts and analysis of local phenomena. The turn towards complex societies meant that political themes were taken up at two main levels. Firstly, anthropologists continued to study political organization and political phenomena that lay outside the state-regulated sphere (as in patron-client relations or tribal political organization). Secondly, anthropologists slowly started to develop a disciplinary concern with states and their institutions (and on the relationship between formal and informal political institutions). An anthropology of the state developed, and it is a most thriving field today. Geertz' comparative work on "Negara", the Balinese state, is an early, famous example. Legal Legal anthropology or anthropology of law specializes in "the cross-cultural study of social ordering". Earlier legal anthropological research often focused more narrowly on conflict management, crime, sanctions, or formal regulation. More recent applications include issues such as human rights, legal pluralism, and political uprisings. Public Public anthropology was created by Robert Borofsky, a professor at Hawaii Pacific University, to "demonstrate the ability of anthropology and anthropologists to effectively address problems beyond the discipline – illuminating larger social issues of our times as well as encouraging broad, public conversations about them with the explicit goal of fostering social change". Nature, science, and technology Cyborg Cyborg anthropology originated as a sub-focus group within the American Anthropological Association's annual meeting in 1993. The sub-group was very closely related to STS and the Society for the Social Studies of Science. Donna Haraway's 1985 Cyborg Manifesto could be considered the founding document of cyborg anthropology by first exploring the philosophical and sociological ramifications of the term. Cyborg anthropology studies humankind and its relations with the technological systems it has built, specifically modern technological systems that have reflexively shaped notions of what it means to be human beings. Digital Digital anthropology is the study of the relationship between humans and digital-era technology, and extends to various areas where anthropology and technology intersect. It is sometimes grouped with sociocultural anthropology, and sometimes considered part of material culture. The field is new, and thus has a variety of names with a variety of emphases. These include techno-anthropology, digital ethnography, cyberanthropology, and virtual anthropology. Ecological Ecological anthropology is defined as the "study of cultural adaptations to environments". The sub-field is also defined as, "the study of relationships between a population of humans and their biophysical environment". The focus of its research concerns "how cultural beliefs and practices helped human populations adapt to their environments, and how their environments change across space and time. The contemporary perspective of environmental anthropology, and arguably at least the backdrop, if not the focus of most of the ethnographies and cultural fieldworks of today, is political ecology. Many characterize this new perspective as more informed with culture, politics and power, globalization, localized issues, century anthropology and more. The focus and data interpretation is often used for arguments for/against or creation of policy, and to prevent corporate exploitation and damage of land. Often, the observer has become an active part of the struggle either directly (organizing, participation) or indirectly (articles, documentaries, books, ethnographies). Such is the case with environmental justice advocate Melissa Checker and her relationship with the people of Hyde Park. Environment Social sciences, like anthropology, can provide interdisciplinary approaches to the environment. Professor Kay Milton, Director of the Anthropology research network in the School of History and Anthropology, describes anthropology as distinctive, with its most distinguishing feature being its interest in non-industrial indigenous and traditional societies. Anthropological theory is distinct because of the consistent presence of the concept of culture; not an exclusive topic but a central position in the study and a deep concern with the human condition. Milton describes three trends that are causing a fundamental shift in what characterizes anthropology: dissatisfaction with the cultural relativist perspective, reaction against cartesian dualisms which obstructs progress in theory (nature culture divide), and finally an increased attention to globalization (transcending the barriers or time/space). Environmental discourse appears to be characterized by a high degree of globalization. (The troubling problem is borrowing non indigenous practices and creating standards, concepts, philosophies and practices in western countries.) Anthropology and environmental discourse now have become a distinct position in anthropology as a discipline. Knowledge about diversities in human culture can be important in addressing environmental problems - anthropology is now a study of human ecology. Human activity is the most important agent in creating environmental change, a study commonly found in human ecology which can claim a central place in how environmental problems are examined and addressed. Other ways anthropology contributes to environmental discourse is by being theorists and analysts,  or by refinement of definitions to become more neutral/universal, etc. In exploring environmentalism - the term typically refers to a concern that the environment should be protected, particularly from the harmful effects of human activities. Environmentalism itself can be expressed in many ways. Anthropologists can open the doors of environmentalism by looking beyond industrial society, understanding the opposition between industrial and non industrial relationships, knowing what ecosystem people and biosphere people are and are affected by, dependent and independent variables, “primitive” ecological wisdom, diverse environments, resource management, diverse cultural traditions, and knowing that environmentalism is a part of culture. Historical Ethnohistory is the study of ethnographic cultures and indigenous customs by examining historical records. It is also the study of the history of various ethnic groups that may or may not exist today. Ethnohistory uses both historical and ethnographic data as its foundation. Its historical methods and materials go beyond the standard use of documents and manuscripts. Practitioners recognize the utility of such source material as maps, music, paintings, photography, folklore, oral tradition, site exploration, archaeological materials, museum collections, enduring customs, language, and place names. Religion The anthropology of religion involves the study of religious institutions in relation to other social institutions, and the comparison of religious beliefs and practices across cultures. Modern anthropology assumes that there is complete continuity between magical thinking and religion, and that every religion is a cultural product, created by the human community that worships it. Urban Urban anthropology is concerned with issues of urbanization, poverty, and neoliberalism. Ulf Hannerz quotes a 1960s remark that traditional anthropologists were "a notoriously agoraphobic lot, anti-urban by definition". Various social processes in the Western World as well as in the "Third World" (the latter being the habitual focus of attention of anthropologists) brought the attention of "specialists in 'other cultures'" closer to their homes. There are two main approaches to urban anthropology: examining the types of cities or examining the social issues within the cities. These two methods are overlapping and dependent of each other. By defining different types of cities, one would use social factors as well as economic and political factors to categorize the cities. By directly looking at the different social issues, one would also be studying how they affect the dynamic of the city. Key topics by field: archaeological and biological Anthrozoology Anthrozoology (also known as "human–animal studies") is the study of interaction between living things. It is an interdisciplinary field that overlaps with a number of other disciplines, including anthropology, ethology, medicine, psychology, veterinary medicine and zoology. A major focus of anthrozoologic research is the quantifying of the positive effects of human-animal relationships on either party and the study of their interactions. It includes scholars from a diverse range of fields, including anthropology, sociology, biology, and philosophy. Biocultural Biocultural anthropology is the scientific exploration of the relationships between human biology and culture. Physical anthropologists throughout the first half of the 20th century viewed this relationship from a racial perspective; that is, from the assumption that typological human biological differences lead to cultural differences. After World War II the emphasis began to shift toward an effort to explore the role culture plays in shaping human biology. Evolutionary Evolutionary anthropology is the interdisciplinary study of the evolution of human physiology and human behaviour and the relation between hominins and non-hominin primates. Evolutionary anthropology is based in natural science and social science, combining the human development with socioeconomic factors. Evolutionary anthropology is concerned with both biological and cultural evolution of humans, past and present. It is based on a scientific approach, and brings together fields such as archaeology, behavioral ecology, psychology, primatology, and genetics. It is a dynamic and interdisciplinary field, drawing on many lines of evidence to understand the human experience, past and present. Forensic Forensic anthropology is the application of the science of physical anthropology and human osteology in a legal setting, most often in criminal cases where the victim's remains are in the advanced stages of decomposition. A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated or otherwise unrecognizable. The adjective "forensic" refers to the application of this subfield of science to a court of law. Palaeoanthropology Paleoanthropology combines the disciplines of paleontology and physical anthropology. It is the study of ancient humans, as found in fossil hominid evidence such as petrifacted bones and footprints. Genetics and morphology of specimens are crucially important to this field. Markers on specimens, such as enamel fractures and dental decay on teeth, can also give insight into the behaviour and diet of past populations. Organizations Contemporary anthropology is an established science with academic departments at most universities and colleges. The single largest organization of anthropologists is the American Anthropological Association (AAA), which was founded in 1903. Its members are anthropologists from around the globe. In 1989, a group of European and American scholars in the field of anthropology established the European Association of Social Anthropologists (EASA) which serves as a major professional organization for anthropologists working in Europe. The EASA seeks to advance the status of anthropology in Europe and to increase visibility of marginalized anthropological traditions and thereby contribute to the project of a global anthropology or world anthropology. Hundreds of other organizations exist in the various sub-fields of anthropology, sometimes divided up by nation or region, and many anthropologists work with collaborators in other disciplines, such as geology, physics, zoology, paleontology, anatomy, music theory, art history, sociology and so on, belonging to professional societies in those disciplines as well. List of major organizations American Anthropological Association American Ethnological Society Asociación de Antropólogos Iberoamericanos en Red, AIBR Moving Anthropology Student Network Anthropological Society of London Center for World Indigenous Studies Ethnological Society of London Max Planck Institute for Evolutionary Anthropology Network of Concerned Anthropologists N.N. Miklukho-Maklai Institute of Ethnology and Anthropology Royal Anthropological Institute of Great Britain and Ireland Society for anthropological sciences Society for Applied Anthropology USC Center for Visual Anthropology Ethics As the field has matured it has debated and arrived at ethical principles aimed at protecting both the subjects of anthropological research as well as the researchers themselves, and professional societies have generated codes of ethics. Anthropologists, like other researchers (especially historians and scientists engaged in field research), have over time assisted state policies and projects, especially colonialism. Some commentators have contended: That the discipline grew out of colonialism, perhaps was in league with it, and derives some of its key notions from it, consciously or not. (See, for example, Gough, Pels and Salemink, but cf. Lewis 2004). That ethnographic work is often ahistorical, writing about people as if they were "out of time" in an "ethnographic present" (Johannes Fabian, Time and Its Other). In his article "The Misrepresentation of Anthropology and Its Consequence," Herbert S. Lewis critiqued older anthropological works that presented other cultures as if they were strange and unusual. While the findings of those researchers should not be discarded, the field should learn from its mistakes. Cultural relativism As part of their quest for scientific objectivity, present-day anthropologists typically urge cultural relativism, which has an influence on all the sub-fields of anthropology. This is the notion that cultures should not be judged by another's values or viewpoints, but be examined dispassionately on their own terms. There should be no notions, in good anthropology, of one culture being better or worse than another culture. Ethical commitments in anthropology include noticing and documenting genocide, infanticide, racism, sexism, mutilation (including circumcision and subincision), and torture. Topics like racism, slavery, and human sacrifice attract anthropological attention and theories ranging from nutritional deficiencies, to genes, to acculturation, to colonialism, have been proposed to explain their origins and continued recurrences. To illustrate the depth of an anthropological approach, one can take just one of these topics, such as "racism" and find thousands of anthropological references, stretching across all the major and minor sub-fields. Military involvement Anthropologists' involvement with the U.S. government, in particular, has caused bitter controversy within the discipline. Franz Boas publicly objected to US participation in World War I, and after the war he published a brief expose and condemnation of the participation of several American archaeologists in espionage in Mexico under their cover as scientists. But by the 1940s, many of Boas' anthropologist contemporaries were active in the allied war effort against the Axis Powers (Nazi Germany, Fascist Italy, and Imperial Japan). Many served in the armed forces, while others worked in intelligence (for example, Office of Strategic Services and the Office of War Information). At the same time, David H. Price's work on American anthropology during the Cold War provides detailed accounts of the pursuit and dismissal of several anthropologists from their jobs for communist sympathies. Attempts to accuse anthropologists of complicity with the CIA and government intelligence activities during the Vietnam War years have turned up surprisingly little. Many anthropologists (students and teachers) were active in the antiwar movement. Numerous resolutions condemning the war in all its aspects were passed overwhelmingly at the annual meetings of the American Anthropological Association (AAA). Professional anthropological bodies often object to the use of anthropology for the benefit of the state. Their codes of ethics or statements may proscribe anthropologists from giving secret briefings. The Association of Social Anthropologists of the UK and Commonwealth (ASA) has called certain scholarship ethically dangerous. The "Principles of Professional Responsibility" issued by the American Anthropological Association and amended through November 1986 stated that "in relation with their own government and with host governments ... no secret research, no secret reports or debriefings of any kind should be agreed to or given." The current "Principles of Professional Responsibility" does not make explicit mention of ethics surrounding state interactions. Anthropologists, along with other social scientists, are working with the US military as part of the US Army's strategy in Afghanistan. The Christian Science Monitor reports that "Counterinsurgency efforts focus on better grasping and meeting local needs" in Afghanistan, under the Human Terrain System (HTS) program; in addition, HTS teams are working with the US military in Iraq. In 2009, the American Anthropological Association's Commission on the Engagement of Anthropology with the US Security and Intelligence Communities released its final report concluding, in part, that, "When ethnographic investigation is determined by military missions, not subject to external review, where data collection occurs in the context of war, integrated into the goals of counterinsurgency, and in a potentially coercive environment – all characteristic factors of the HTS concept and its application – it can no longer be considered a legitimate professional exercise of anthropology. In summary, while we stress that constructive engagement between anthropology and the military is possible, CEAUSSIC suggests that the AAA emphasize the incompatibility of HTS with disciplinary ethics and practice for job seekers and that it further recognize the problem of allowing HTS to define the meaning of "anthropology" within DoD." Post–World War II developments Before WWII British 'social anthropology' and American 'cultural anthropology' were still distinct traditions. After the war, enough British and American anthropologists borrowed ideas and methodological approaches from one another that some began to speak of them collectively as 'sociocultural' anthropology. Basic trends There are several characteristics that tend to unite anthropological work. One of the central characteristics is that anthropology tends to provide a comparatively more holistic account of phenomena and tends to be highly empirical. The quest for holism leads most anthropologists to study a particular place, problem or phenomenon in detail, using a variety of methods, over a more extensive period than normal in many parts of academia. In the 1990s and 2000s, calls for clarification of what constitutes a culture, of how an observer knows where his or her own culture ends and another begins, and other crucial topics in writing anthropology were heard. These dynamic relationships, between what can be observed on the ground, as opposed to what can be observed by compiling many local observations remain fundamental in any kind of anthropology, whether cultural, biological, linguistic or archaeological. Biological anthropologists are interested in both human variation and in the possibility of human universals (behaviors, ideas or concepts shared by virtually all human cultures). They use many different methods of study, but modern population genetics, participant observation and other techniques often take anthropologists "into the field," which means traveling to a community in its own setting, to do something called "fieldwork." On the biological or physical side, human measurements, genetic samples, nutritional data may be gathered and published as articles or monographs. Along with dividing up their project by theoretical emphasis, anthropologists typically divide the world up into relevant time periods and geographic regions. Human time on Earth is divided up into relevant cultural traditions based on material, such as the Paleolithic and the Neolithic, of particular use in archaeology. Further cultural subdivisions according to tool types, such as Olduwan or Mousterian or Levalloisian help archaeologists and other anthropologists in understanding major trends in the human past. Anthropologists and geographers share approaches to culture regions as well, since mapping cultures is central to both sciences. By making comparisons across cultural traditions (time-based) and cultural regions (space-based), anthropologists have developed various kinds of comparative method, a central part of their science. Commonalities between fields Because anthropology developed from so many different enterprises (see History of anthropology), including but not limited to fossil-hunting, exploring, documentary film-making, paleontology, primatology, antiquity dealings and curatorship, philology, etymology, genetics, regional analysis, ethnology, history, philosophy, and religious studies, it is difficult to characterize the entire field in a brief article, although attempts to write histories of the entire field have been made. Some authors argue that anthropology originated and developed as the study of "other cultures", both in terms of time (past societies) and space (non-European/non-Western societies). For example, the classic of urban anthropology, Ulf Hannerz in the introduction to his seminal Exploring the City: Inquiries Toward an Urban Anthropology mentions that the "Third World" had habitually received most of attention; anthropologists who traditionally specialized in "other cultures" looked for them far away and started to look "across the tracks" only in late 1960s. Now there exist many works focusing on peoples and topics very close to the author's "home". It is also argued that other fields of study, like History and Sociology, on the contrary focus disproportionately on the West. In France, the study of Western societies has been traditionally left to sociologists, but this is increasingly changing, starting in the 1970s from scholars like Isac Chiva and journals like Terrain ("fieldwork"), and developing with the center founded by Marc Augé (Le Centre d'anthropologie des mondes contemporains, the Anthropological Research Center of Contemporary Societies). Since the 1980s it has become common for social and cultural anthropologists to set ethnographic research in the North Atlantic region, frequently examining the connections between locations rather than limiting research to a single locale. There has also been a related shift toward broadening the focus beyond the daily life of ordinary people; increasingly, research is set in settings such as scientific laboratories, social movements, governmental and nongovernmental organizations and businesses. See also Anthropological science fiction Christian anthropology, a sub-field of theology Circumscription theory Culture Dual inheritance theory Engaged theory Ethnobiology Human behavioral ecology Human ethology Human Relations Area Files Intangible cultural heritage Origins of society Philosophical anthropology, a sub-field of philosophy Prehistoric medicine Qualitative research Lists Outline of anthropology List of indigenous peoples List of anthropologists Notes References Further reading Dictionaries and encyclopedias Fieldnotes and memoirs Histories . Textbooks and key theoretical works External links (AIO)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

573

https://en.wikipedia.org/wiki/Alchemy

Alchemy

Alchemy (from Arabic: al-kīmiyā; from Ancient Greek: khumeía) is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, and Europe. In its Western form, alchemy is first attested in a number of pseudepigraphical texts written in Greco-Roman Egypt during the first few centuries CE. Alchemists attempted to purify, mature, and perfect certain materials. Common aims were chrysopoeia, the transmutation of "base metals" (e.g., lead) into "noble metals" (particularly gold); the creation of an elixir of immortality; and the creation of panaceas able to cure any disease. The perfection of the human body and soul was thought to result from the alchemical magnum opus ("Great Work"). The concept of creating the philosophers' stone was variously connected with all of these projects. Islamic and European alchemists developed a basic set of laboratory techniques, theories, and terms, some of which are still in use today. They did not abandon the Ancient Greek philosophical idea that everything is composed of four elements, and they tended to guard their work in secrecy, often making use of cyphers and cryptic symbolism. In Europe, the 12th-century translations of medieval Islamic works on science and the rediscovery of Aristotelian philosophy gave birth to a flourishing tradition of Latin alchemy. This late medieval tradition of alchemy would go on to play a significant role in the development of early modern science (particularly chemistry and medicine). Modern discussions of alchemy are generally split into an examination of its exoteric practical applications and its esoteric spiritual aspects, despite criticisms by scholars such as Eric J. Holmyard and Marie-Louise von Franz that they should be understood as complementary. The former is pursued by historians of the physical sciences, who examine the subject in terms of early chemistry, medicine, and charlatanism, and the philosophical and religious contexts in which these events occurred. The latter interests historians of esotericism, psychologists, and some philosophers and spiritualists. The subject has also made an ongoing impact on literature and the arts. Etymology The word alchemy comes from Old French alquemie, alkimie, used in Medieval Latin as . This name was itself brought from the Arabic word al-kīmiyā ( or ) composed of two parts: the Late Greek term khēmeía (χημεία), also spelled khumeia (χυμεία) and khēmía (χημία) - see below, and the Arabic definite article al- (), meaning 'The'. Together this association can be interpreted as 'the process of transmutation by which to fuse or reunite with the divine or original form'. Several etymologies have been proposed for the Greek term. The first was proposed by Zosimos of Panopolis (3rd–4th centuries), who derived it from the name of a book, the Khemeu. Hermanm Diels argued in 1914 that it rather derived from χύμα, used to describe metallic objects formed by casting. Others trace its roots to the Egyptian name kēme (hieroglyphic 𓆎𓅓𓏏𓊖 khmi ), meaning 'black earth', which refers to the fertile and auriferous soil of the Nile valley, as opposed to red desert sand. According to the Egyptologist Wallis Budge, the Arabic word al-kīmiyaʾ actually means "the Egyptian [science]", borrowing from the Coptic word for "Egypt", kēme (or its equivalent in the Mediaeval Bohairic dialect of Coptic, khēme). This Coptic word derives from Demotic kmỉ, itself from ancient Egyptian kmt. The ancient Egyptian word referred to both the country and the colour "black" (Egypt was the "Black Land", by contrast with the "Red Land", the surrounding desert); so this etymology could also explain the nickname "Egyptian black arts". History Alchemy encompasses several philosophical traditions spanning some four millennia and three continents. These traditions' general penchant for cryptic and symbolic language makes it hard to trace their mutual influences and "genetic" relationships. One can distinguish at least three major strands, which appear to be mostly independent, at least in their earlier stages: Chinese alchemy, centered in China and Indian alchemy, centered on the Indian subcontinent; and Western alchemy, which occurred around the Mediterranean and whose center has shifted over the millennia from Greco-Roman Egypt to the Islamic world, and finally medieval Europe. Chinese alchemy was closely connected to Taoism and Indian alchemy with the Dharmic faiths. In contrast, Western alchemy developed its philosophical system mostly independent of but influenced by various Western religions. It is still an open question whether these three strands share a common origin, or to what extent they influenced each other. Hellenistic Egypt The start of Western alchemy may generally be traced to ancient and Hellenistic Egypt, where the city of Alexandria was a center of alchemical knowledge, and retained its pre-eminence through most of the Greek and Roman periods. Following the work of André-Jean Festugière, modern scholars see alchemical practice in the Roman Empire as originating from the Egyptian goldsmith's art, Greek philosophy and different religious traditions. Tracing the origins of the alchemical art in Egypt is complicated by the pseudepigraphic nature of texts from the Greek alchemical corpus. The treatises of Zosimos of Panopolis, the earliest historically attested author (fl. c. 300 CE), can help in situating the other authors. Zosimus based his work on that of older alchemical authors, such as Mary the Jewess, Pseudo-Democritus, and Agathodaimon, but very little is known about any of these authors. The most complete of their works, The Four Books of Pseudo-Democritus, were probably written in the first century AD. Recent scholarship tends to emphasize the testimony of Zosimus, who traced the alchemical arts back to Egyptian metallurgical and ceremonial practices. It has also been argued that early alchemical writers borrowed the vocabulary of Greek philosophical schools but did not implement any of its doctrines in a systematic way. Zosimos of Panopolis wrote in the Final Abstinence (also known as the "Final Count"). Zosimos explains that the ancient practice of "tinctures" (the technical Greek name for the alchemical arts) had been taken over by certain "demons" who taught the art only to those who offered them sacrifices. Since Zosimos also called the demons "guardians of places" (οἱ κατὰ τόπον ἔφοροι) and those who offered them sacrifices "priests" (ἱερέα), it is fairly clear that he was referring to the gods of Egypt and their priests. While critical of the kind of alchemy he associated with the Egyptian priests and their followers, Zosimos nonetheless saw the tradition's recent past as rooted in the rites of the Egyptian temples. Mythology – Zosimos of Panopolis asserted that alchemy dated back to Pharaonic Egypt where it was the domain of the priestly class, though there is little to no evidence for his assertion. Alchemical writers used Classical figures from Greek, Roman, and Egyptian mythology to illuminate their works and allegorize alchemical transmutation. These included the pantheon of gods related to the Classical planets, Isis, Osiris, Jason, and many others. The central figure in the mythology of alchemy is Hermes Trismegistus (or Thrice-Great Hermes). His name is derived from the god Thoth and his Greek counterpart Hermes. Hermes and his caduceus or serpent-staff, were among alchemy's principal symbols. According to Clement of Alexandria, he wrote what were called the "forty-two books of Hermes", covering all fields of knowledge. The Hermetica of Thrice-Great Hermes is generally understood to form the basis for Western alchemical philosophy and practice, called the hermetic philosophy by its early practitioners. These writings were collected in the first centuries of the common era. Technology – The dawn of Western alchemy is sometimes associated with that of metallurgy, extending back to 3500 BC. Many writings were lost when the Roman emperor Diocletian ordered the burning of alchemical books after suppressing a revolt in Alexandria (AD 292). Few original Egyptian documents on alchemy have survived, most notable among them the Stockholm papyrus and the Leyden papyrus X. Dating from AD 250–300, they contained recipes for dyeing and making artificial gemstones, cleaning and fabricating pearls, and manufacturing of imitation gold and silver. These writings lack the mystical, philosophical elements of alchemy, but do contain the works of Bolus of Mendes (or Pseudo-Democritus), which aligned these recipes with theoretical knowledge of astrology and the classical elements. Between the time of Bolus and Zosimos, the change took place that transformed this metallurgy into a Hermetic art. Philosophy – Alexandria acted as a melting pot for philosophies of Pythagoreanism, Platonism, Stoicism and Gnosticism which formed the origin of alchemy's character. An important example of alchemy's roots in Greek philosophy, originated by Empedocles and developed by Aristotle, was that all things in the universe were formed from only four elements: earth, air, water, and fire. According to Aristotle, each element had a sphere to which it belonged and to which it would return if left undisturbed. The four elements of the Greek were mostly qualitative aspects of matter, not quantitative, as our modern elements are; "...True alchemy never regarded earth, air, water, and fire as corporeal or chemical substances in the present-day sense of the word. The four elements are simply the primary, and most general, qualities by means of which the amorphous and purely quantitative substance of all bodies first reveals itself in differentiated form." Later alchemists extensively developed the mystical aspects of this concept. Alchemy coexisted alongside emerging Christianity. Lactantius believed Hermes Trismegistus had prophesied its birth. St Augustine later affirmed this in the 4th & 5th centuries, but also condemned Trismegistus for idolatry. Examples of Pagan, Christian, and Jewish alchemists can be found during this period. Most of the Greco-Roman alchemists preceding Zosimos are known only by pseudonyms, such as Moses, Isis, Cleopatra, Democritus, and Ostanes. Others authors such as Komarios, and Chymes, we only know through fragments of text. After AD 400, Greek alchemical writers occupied themselves solely in commenting on the works of these predecessors. By the middle of the 7th century alchemy was almost an entirely mystical discipline. It was at that time that Khalid Ibn Yazid sparked its migration from Alexandria to the Islamic world, facilitating the translation and preservation of Greek alchemical texts in the 8th and 9th centuries. Byzantium Greek alchemy is preserved in medieval Greek (Byzantine) manuscripts, and yet historians have only relatively recently begun to pay attention to the study and development of Greek alchemy in the Byzantine period. India The 2nd millennium BC text Vedas describe a connection between eternal life and gold. A considerable knowledge of metallurgy has been exhibited in a third-century CE text called Arthashastra which provides ingredients of explosives (Agniyoga) and salts extracted from fertile soils and plant remains (Yavakshara) such as saltpetre/nitre, perfume making (different qualities of perfumes are mentioned), granulated (refined) Sugar. Buddhist texts from the 2nd to 5th centuries mention the transmutation of base metals to gold. According to some scholars Greek alchemy may have influenced Indian alchemy but there are no hard evidences to back this claim. The 11th-century Persian chemist and physician Abū Rayhān Bīrūnī, who visited Gujarat as part of the court of Mahmud of Ghazni, reported that they The goals of alchemy in India included the creation of a divine body (Sanskrit divya-deham) and immortality while still embodied (Sanskrit jīvan-mukti). Sanskrit alchemical texts include much material on the manipulation of mercury and sulphur, that are homologized with the semen of the god Śiva and the menstrual blood of the goddess Devī. Some early alchemical writings seem to have their origins in the Kaula tantric schools associated to the teachings of the personality of Matsyendranath. Other early writings are found in the Jaina medical treatise Kalyāṇakārakam of Ugrāditya, written in South India in the early 9th century. Two famous early Indian alchemical authors were Nāgārjuna Siddha and Nityanātha Siddha. Nāgārjuna Siddha was a Buddhist monk. His book, Rasendramangalam, is an example of Indian alchemy and medicine. Nityanātha Siddha wrote Rasaratnākara, also a highly influential work. In Sanskrit, rasa translates to "mercury", and Nāgārjuna Siddha was said to have developed a method of converting mercury into gold. Scholarship on Indian alchemy is in the publication of The Alchemical Body by David Gordon White. A modern bibliography on Indian alchemical studies has been written by White. The contents of 39 Sanskrit alchemical treatises have been analysed in detail in G. Jan Meulenbeld's History of Indian Medical Literature. The discussion of these works in HIML gives a summary of the contents of each work, their special features, and where possible the evidence concerning their dating. Chapter 13 of HIML, Various works on rasaśāstra and ratnaśāstra (or Various works on alchemy and gems) gives brief details of a further 655 (six hundred and fifty-five) treatises. In some cases Meulenbeld gives notes on the contents and authorship of these works; in other cases references are made only to the unpublished manuscripts of these titles. A great deal remains to be discovered about Indian alchemical literature. The content of the Sanskrit alchemical corpus has not yet (2014) been adequately integrated into the wider general history of alchemy. Islamic world After the Fall of the Roman Empire, the focus of alchemical development moved to the Islamic World. Much more is known about Islamic alchemy because it was better documented: indeed, most of the earlier writings that have come down through the years were preserved as Arabic translations. The word alchemy itself was derived from the Arabic word al-kīmiyā (الكيمياء). The early Islamic world was a melting pot for alchemy. Platonic and Aristotelian thought, which had already been somewhat appropriated into hermetical science, continued to be assimilated during the late 7th and early 8th centuries through Syriac translations and scholarship. In the late ninth and early tenth centuries, the Arabic works attributed to Jābir ibn Hayyān (Latinized as "Geber" or "Geberus") introduced a new approach to alchemy. Paul Kraus, who wrote the standard reference work on Jabir, put it as follows: Islamic philosophers also made great contributions to alchemical hermeticism. The most influential author in this regard was arguably Jabir. Jabir's ultimate goal was Takwin, the artificial creation of life in the alchemical laboratory, up to, and including, human life. He analyzed each Aristotelian element in terms of four basic qualities of hotness, coldness, dryness, and moistness. According to Jabir, in each metal two of these qualities were interior and two were exterior. For example, lead was externally cold and dry, while gold was hot and moist. Thus, Jabir theorized, by rearranging the qualities of one metal, a different metal would result. By this reasoning, the search for the philosopher's stone was introduced to Western alchemy. Jabir developed an elaborate numerology whereby the root letters of a substance's name in Arabic, when treated with various transformations, held correspondences to the element's physical properties. The elemental system used in medieval alchemy also originated with Jabir. His original system consisted of seven elements, which included the five classical elements (aether, air, earth, fire, and water) in addition to two chemical elements representing the metals: sulphur, "the stone which burns", which characterized the principle of combustibility, and mercury, which contained the idealized principle of metallic properties. Shortly thereafter, this evolved into eight elements, with the Arabic concept of the three metallic principles: sulphur giving flammability or combustion, mercury giving volatility and stability, and salt giving solidity. The atomic theory of corpuscularianism, where all physical bodies possess an inner and outer layer of minute particles or corpuscles, also has its origins in the work of Jabir. From the 9th to 14th centuries, alchemical theories faced criticism from a variety of practical Muslim chemists, including Alkindus, Abū al-Rayhān al-Bīrūnī, Avicenna and Ibn Khaldun. In particular, they wrote refutations against the idea of the transmutation of metals. East Asia Whereas European alchemy eventually centered on the transmutation of base metals into noble metals, Chinese alchemy had a more obvious connection to medicine. The philosopher's stone of European alchemists can be compared to the Grand Elixir of Immortality sought by Chinese alchemists. In the hermetic view, these two goals were not unconnected, and the philosopher's stone was often equated with the universal panacea; therefore, the two traditions may have had more in common than initially appears. Black powder may have been an important invention of Chinese alchemists. As previously stated above, Chinese alchemy was more related to medicine. It is said that the Chinese invented gunpowder while trying to find a potion for eternal life. Described in 9th-century texts and used in fireworks in China by the 10th century, it was used in cannons by 1290. From China, the use of gunpowder spread to Japan, the Mongols, the Muslim world, and Europe. Gunpowder was used by the Mongols against the Hungarians in 1241, and in Europe by the 14th century. Chinese alchemy was closely connected to Taoist forms of traditional Chinese medicine, such as Acupuncture and Moxibustion. In the early Song dynasty, followers of this Taoist idea (chiefly the elite and upper class) would ingest mercuric sulfide, which, though tolerable in low levels, led many to suicide. Thinking that this consequential death would lead to freedom and access to the Taoist heavens, the ensuing deaths encouraged people to eschew this method of alchemy in favor of external sources (the aforementioned Tai Chi Chuan, mastering of the qi, etc.) Chinese alchemy was introduced to the West by Obed Simon Johnson. Medieval Europe The introduction of alchemy to Latin Europe may be dated to 11 February 1144, with the completion of Robert of Chester's translation of the Arabic Book of the Composition of Alchemy. Although European craftsmen and technicians pre-existed, Robert notes in his preface that alchemy (though here still referring to the elixir rather than to the art itself) was unknown in Latin Europe at the time of his writing. The translation of Arabic texts concerning numerous disciplines including alchemy flourished in 12th-century Toledo, Spain, through contributors like Gerard of Cremona and Adelard of Bath. Translations of the time included the Turba Philosophorum, and the works of Avicenna and Muhammad ibn Zakariya al-Razi. These brought with them many new words to the European vocabulary for which there was no previous Latin equivalent. Alcohol, carboy, elixir, and athanor are examples. Meanwhile, theologian contemporaries of the translators made strides towards the reconciliation of faith and experimental rationalism, thereby priming Europe for the influx of alchemical thought. The 11th-century St Anselm put forth the opinion that faith and rationalism were compatible and encouraged rationalism in a Christian context. In the early 12th century, Peter Abelard followed Anselm's work, laying down the foundation for acceptance of Aristotelian thought before the first works of Aristotle had reached the West. In the early 13th century, Robert Grosseteste used Abelard's methods of analysis and added the use of observation, experimentation, and conclusions when conducting scientific investigations. Grosseteste also did much work to reconcile Platonic and Aristotelian thinking. Through much of the 12th and 13th centuries, alchemical knowledge in Europe remained centered on translations, and new Latin contributions were not made. The efforts of the translators were succeeded by that of the encyclopaedists. In the 13th century, Albertus Magnus and Roger Bacon were the most notable of these, their work summarizing and explaining the newly imported alchemical knowledge in Aristotelian terms. Albertus Magnus, a Dominican friar, is known to have written works such as the Book of Minerals where he observed and commented on the operations and theories of alchemical authorities like Hermes and Democritus and unnamed alchemists of his time. Albertus critically compared these to the writings of Aristotle and Avicenna, where they concerned the transmutation of metals. From the time shortly after his death through to the 15th century, more than 28 alchemical tracts were misattributed to him, a common practice giving rise to his reputation as an accomplished alchemist. Likewise, alchemical texts have been attributed to Albert's student Thomas Aquinas. Roger Bacon, a Franciscan friar who wrote on a wide variety of topics including optics, comparative linguistics, and medicine, composed his Great Work () for as part of a project towards rebuilding the medieval university curriculum to include the new learning of his time. While alchemy was not more important to him than other sciences and he did not produce allegorical works on the topic, he did consider it and astrology to be important parts of both natural philosophy and theology and his contributions advanced alchemy's connections to soteriology and Christian theology. Bacon's writings integrated morality, salvation, alchemy, and the prolongation of life. His correspondence with Clement highlighted this, noting the importance of alchemy to the papacy. Like the Greeks before him, Bacon acknowledged the division of alchemy into practical and theoretical spheres. He noted that the theoretical lay outside the scope of Aristotle, the natural philosophers, and all Latin writers of his time. The practical confirmed the theoretical, and Bacon advocated its uses in natural science and medicine. In later European legend, he became an archmage. In particular, along with Albertus Magnus, he was credited with the forging of a brazen head capable of answering its owner's questions. Soon after Bacon, the influential work of Pseudo-Geber (sometimes identified as Paul of Taranto) appeared. His Summa Perfectionis remained a staple summary of alchemical practice and theory through the medieval and renaissance periods. It was notable for its inclusion of practical chemical operations alongside sulphur-mercury theory, and the unusual clarity with which they were described. By the end of the 13th century, alchemy had developed into a fairly structured system of belief. Adepts believed in the macrocosm-microcosm theories of Hermes, that is to say, they believed that processes that affect minerals and other substances could have an effect on the human body (for example, if one could learn the secret of purifying gold, one could use the technique to purify the human soul). They believed in the four elements and the four qualities as described above, and they had a strong tradition of cloaking their written ideas in a labyrinth of coded jargon set with traps to mislead the uninitiated. Finally, the alchemists practiced their art: they actively experimented with chemicals and made observations and theories about how the universe operated. Their entire philosophy revolved around their belief that man's soul was divided within himself after the fall of Adam. By purifying the two parts of man's soul, man could be reunited with God. In the 14th century, alchemy became more accessible to Europeans outside the confines of Latin speaking churchmen and scholars. Alchemical discourse shifted from scholarly philosophical debate to an exposed social commentary on the alchemists themselves. Dante, Piers Plowman, and Chaucer all painted unflattering pictures of alchemists as thieves and liars. Pope John XXII's 1317 edict, Spondent quas non-exhibent forbade the false promises of transmutation made by pseudo-alchemists. In 1403, Henry IV of England banned the practice of multiplying metals (although it was possible to buy a licence to attempt to make gold alchemically, and a number were granted by Henry VI and Edward IV). These critiques and regulations centered more around pseudo-alchemical charlatanism than the actual study of alchemy, which continued with an increasingly Christian tone. The 14th century saw the Christian imagery of death and resurrection employed in the alchemical texts of Petrus Bonus, John of Rupescissa, and in works written in the name of Raymond Lull and Arnold of Villanova. Nicolas Flamel is a well-known alchemist, but a good example of pseudepigraphy, the practice of giving your works the name of someone else, usually more famous. Although the historical Flamel existed, the writings and legends assigned to him only appeared in 1612. Flamel was not a religious scholar as were many of his predecessors, and his entire interest in the subject revolved around the pursuit of the philosopher's stone. His work spends a great deal of time describing the processes and reactions, but never actually gives the formula for carrying out the transmutations. Most of 'his' work was aimed at gathering alchemical knowledge that had existed before him, especially as regarded the philosopher's stone. Through the 14th and 15th centuries, alchemists were much like Flamel: they concentrated on looking for the philosophers' stone. Bernard Trevisan and George Ripley made similar contributions. Their cryptic allusions and symbolism led to wide variations in interpretation of the art. Renaissance and early modern Europe During the Renaissance, Hermetic and Platonic foundations were restored to European alchemy. The dawn of medical, pharmaceutical, occult, and entrepreneurial branches of alchemy followed. In the late 15th century, Marsilo Ficino translated the Corpus Hermeticum and the works of Plato into Latin. These were previously unavailable to Europeans who for the first time had a full picture of the alchemical theory that Bacon had declared absent. Renaissance Humanism and Renaissance Neoplatonism guided alchemists away from physics to refocus on mankind as the alchemical vessel. Esoteric systems developed that blended alchemy into a broader occult Hermeticism, fusing it with magic, astrology, and Christian cabala. A key figure in this development was German Heinrich Cornelius Agrippa (1486–1535), who received his Hermetic education in Italy in the schools of the humanists. In his De Occulta Philosophia, he attempted to merge Kabbalah, Hermeticism, and alchemy. He was instrumental in spreading this new blend of Hermeticism outside the borders of Italy. Philippus Aureolus Paracelsus, (Theophrastus Bombastus von Hohenheim, 1493–1541) cast alchemy into a new form, rejecting some of Agrippa's occultism and moving away from chrysopoeia. Paracelsus pioneered the use of chemicals and minerals in medicine and wrote, "Many have said of Alchemy, that it is for the making of gold and silver. For me such is not the aim, but to consider only what virtue and power may lie in medicines." His hermetical views were that sickness and health in the body relied on the harmony of man the microcosm and Nature the macrocosm. He took an approach different from those before him, using this analogy not in the manner of soul-purification but in the manner that humans must have certain balances of minerals in their bodies, and that certain illnesses of the body had chemical remedies that could cure them. Iatrochemistry refers to the pharmaceutical applications of alchemy championed by Paracelsus. John Dee (13 July 1527 – December, 1608) followed Agrippa's occult tradition. Although better known for angel summoning, divination, and his role as astrologer, cryptographer, and consultant to Queen Elizabeth I, Dee's alchemical Monas Hieroglyphica, written in 1564 was his most popular and influential work. His writing portrayed alchemy as a sort of terrestrial astronomy in line with the Hermetic axiom As above so below. During the 17th century, a short-lived "supernatural" interpretation of alchemy became popular, including support by fellows of the Royal Society: Robert Boyle and Elias Ashmole. Proponents of the supernatural interpretation of alchemy believed that the philosopher's stone might be used to summon and communicate with angels. Entrepreneurial opportunities were common for the alchemists of Renaissance Europe. Alchemists were contracted by the elite for practical purposes related to mining, medical services, and the production of chemicals, medicines, metals, and gemstones. Rudolf II, Holy Roman Emperor, in the late 16th century, famously received and sponsored various alchemists at his court in Prague, including Dee and his associate Edward Kelley. King James IV of Scotland, Julius, Duke of Brunswick-Lüneburg, Henry V, Duke of Brunswick-Lüneburg, Augustus, Elector of Saxony, Julius Echter von Mespelbrunn, and Maurice, Landgrave of Hesse-Kassel all contracted alchemists. John's son Arthur Dee worked as a court physician to Michael I of Russia and Charles I of England but also compiled the alchemical book Fasciculus Chemicus. Although most of these appointments were legitimate, the trend of pseudo-alchemical fraud continued through the Renaissance. Betrüger would use sleight of hand, or claims of secret knowledge to make money or secure patronage. Legitimate mystical and medical alchemists such as Michael Maier and Heinrich Khunrath wrote about fraudulent transmutations, distinguishing themselves from the con artists. False alchemists were sometimes prosecuted for fraud. The terms "chemia" and "alchemia" were used as synonyms in the early modern period, and the differences between alchemy, chemistry and small-scale assaying and metallurgy were not as neat as in the present day. There were important overlaps between practitioners, and trying to classify them into alchemists, chemists and craftsmen is anachronistic. For example, Tycho Brahe (1546–1601), an alchemist better known for his astronomical and astrological investigations, had a laboratory built at his Uraniborg observatory/research institute. Michael Sendivogius (Michał Sędziwój, 1566–1636), a Polish alchemist, philosopher, medical doctor and pioneer of chemistry wrote mystical works but is also credited with distilling oxygen in a lab sometime around 1600. Sendivogious taught his technique to Cornelius Drebbel who, in 1621, applied this in a submarine. Isaac Newton devoted considerably more of his writing to the study of alchemy (see Isaac Newton's occult studies) than he did to either optics or physics. Other early modern alchemists who were eminent in their other studies include Robert Boyle, and Jan Baptist van Helmont. Their Hermeticism complemented rather than precluded their practical achievements in medicine and science. Later modern period The decline of European alchemy was brought about by the rise of modern science with its emphasis on rigorous quantitative experimentation and its disdain for "ancient wisdom". Although the seeds of these events were planted as early as the 17th century, alchemy still flourished for some two hundred years, and in fact may have reached its peak in the 18th century. As late as 1781 James Price claimed to have produced a powder that could transmute mercury into silver or gold. Early modern European alchemy continued to exhibit a diversity of theories, practices, and purposes: "Scholastic and anti-Aristotelian, Paracelsian and anti-Paracelsian, Hermetic, Neoplatonic, mechanistic, vitalistic, and more—plus virtually every combination and compromise thereof." Robert Boyle (1627–1691) pioneered the scientific method in chemical investigations. He assumed nothing in his experiments and compiled every piece of relevant data. Boyle would note the place in which the experiment was carried out, the wind characteristics, the position of the Sun and Moon, and the barometer reading, all just in case they proved to be relevant. This approach eventually led to the founding of modern chemistry in the 18th and 19th centuries, based on revolutionary discoveries of Lavoisier and John Dalton. Beginning around 1720, a rigid distinction began to be drawn for the first time between "alchemy" and "chemistry". By the 1740s, "alchemy" was now restricted to the realm of gold making, leading to the popular belief that alchemists were charlatans, and the tradition itself nothing more than a fraud. In order to protect the developing science of modern chemistry from the negative censure to which alchemy was being subjected, academic writers during the 18th-century scientific Enlightenment attempted, for the sake of survival, to divorce and separate the "new" chemistry from the "old" practices of alchemy. This move was mostly successful, and the consequences of this continued into the 19th, 20th and 21st centuries. During the occult revival of the early 19th century, alchemy received new attention as an occult science. The esoteric or occultist school, which arose during the 19th century, held (and continues to hold) the view that the substances and operations mentioned in alchemical literature are to be interpreted in a spiritual sense, and it downplays the role of the alchemy as a practical tradition or protoscience. This interpretation further forwarded the view that alchemy is an art primarily concerned with spiritual enlightenment or illumination, as opposed to the physical manipulation of apparatus and chemicals, and claims that the obscure language of the alchemical texts were an allegorical guise for spiritual, moral or mystical processes. In the 19th-century revival of alchemy, the two most seminal figures were Mary Anne Atwood and Ethan Allen Hitchcock, who independently published similar works regarding spiritual alchemy. Both forwarded a completely esoteric view of alchemy, as Atwood claimed: "No modern art or chemistry, notwithstanding all its surreptitious claims, has any thing in common with Alchemy." Atwood's work influenced subsequent authors of the occult revival including Eliphas Levi, Arthur Edward Waite, and Rudolf Steiner. Hitchcock, in his Remarks Upon Alchymists (1855) attempted to make a case for his spiritual interpretation with his claim that the alchemists wrote about a spiritual discipline under a materialistic guise in order to avoid accusations of blasphemy from the church and state. In 1845, Baron Carl Reichenbach, published his studies on Odic force, a concept with some similarities to alchemy, but his research did not enter the mainstream of scientific discussion. In 1946, Louis Cattiaux published the Message Retrouvé, a work that was at once philosophical, mystical and highly influenced by alchemy. In his lineage, many researchers, including Emmanuel and Charles d'Hooghvorst, are updating alchemical studies in France and Belgium. Women Several women appear in the earliest history of alchemy. Michael Maier names Mary the Jewess, Cleopatra the Alchemist, Medera, and Taphnutia as the four women who knew how to make the philosopher's stone. Zosimos' sister Theosebia (later known as Euthica the Arab) and Isis the Prophetess also played a role in early alchemical texts. The first alchemist whose name we know was Mary the Jewess (c. 200 A.D.). Early sources claim that Mary (or Maria) devised a number of improvements to alchemical equipment and tools as well as novel techniques in chemistry. Her best known advances were in heating and distillation processes. The laboratory water-bath, known eponymously (especially in France) as the bain-marie, is said to have been invented or at least improved by her. Essentially a double-boiler, it was (and is) used in chemistry for processes that require gentle heating. The tribikos (a modified distillation apparatus) and the kerotakis (a more intricate apparatus used especially for sublimations) are two other advancements in the process of distillation that are credited to her. Although we have no writing from Mary herself, she is known from the early-fourth-century writings of Zosimos of Panopolis. Due to the proliferation of pseudepigrapha and anonymous works, it is difficult to know which of the alchemists were actually women. After the Greco-Roman period, women's names appear less frequently in the alchemical literature. Women vacate the history of alchemy during the medieval and renaissance periods, aside from the fictitious account of Perenelle Flamel. Mary Anne Atwood's A Suggestive Inquiry into the Hermetic Mystery (1850) marks their return during the nineteenth-century occult revival. Modern historical research The history of alchemy has become a significant and recognized subject of academic study. As the language of the alchemists is analyzed, historians are becoming more aware of the intellectual connections between that discipline and other facets of Western cultural history, such as the evolution of science and philosophy, the sociology and psychology of the intellectual communities, kabbalism, spiritualism, Rosicrucianism, and other mystic movements. Institutions involved in this research include The Chymistry of Isaac Newton project at Indiana University, the University of Exeter Centre for the Study of Esotericism (EXESESO), the European Society for the Study of Western Esotericism (ESSWE), and the University of Amsterdam's Sub-department for the History of Hermetic Philosophy and Related Currents. A large collection of books on alchemy is kept in the Bibliotheca Philosophica Hermetica in Amsterdam. A recipe found in a mid-19th-century kabbalah based book features step by step instructions on turning copper into gold. The author attributed this recipe to an ancient manuscript he located. Journals which publish regularly on the topic of Alchemy include 'Ambix', published by the Society for the History of Alchemy and Chemistry, and 'Isis', published by The History of Science Society. Core concepts Western alchemical theory corresponds to the worldview of late antiquity in which it was born. Concepts were imported from Neoplatonism and earlier Greek cosmology. As such, the classical elements appear in alchemical writings, as do the seven classical planets and the corresponding seven metals of antiquity. Similarly, the gods of the Roman pantheon who are associated with these luminaries are discussed in alchemical literature. The concepts of prima materia and anima mundi are central to the theory of the philosopher's stone. Magnum opus The Great Work of Alchemy is often described as a series of four stages represented by colors. nigredo, a blackening or melanosis albedo, a whitening or leucosis citrinitas, a yellowing or xanthosis rubedo, a reddening, purpling, or iosis Modernity Due to the complexity and obscurity of alchemical literature, and the 18th-century disappearance of remaining alchemical practitioners into the area of chemistry, the general understanding of alchemy has been strongly influenced by several distinct and radically different interpretations. Those focusing on the exoteric, such as historians of science Lawrence M. Principe and William R. Newman, have interpreted the 'decknamen' (or code words) of alchemy as physical substances. These scholars have reconstructed physicochemical experiments that they say are described in medieval and early modern texts. At the opposite end of the spectrum, focusing on the esoteric, scholars, such as George Calian and Anna Marie Roos, who question the reading of Principe and Newman, interpret these same decknamen as spiritual, religious, or psychological concepts. New interpretations of alchemy are still perpetuated, sometimes merging in concepts from New Age or radical environmentalism movements. Groups like the Rosicrucians and Freemasons have a continued interest in alchemy and its symbolism. Since the Victorian revival of alchemy, "occultists reinterpreted alchemy as a spiritual practice, involving the self-transformation of the practitioner and only incidentally or not at all the transformation of laboratory substances", which has contributed to a merger of magic and alchemy in popular thought. Esoteric interpretations of historical texts In the eyes of a variety of modern esoteric and Neo-Hermeticist practitioners, alchemy is fundamentally spiritual. In this interpretation, transmutation of lead into gold is presented as an analogy for personal transmutation, purification, and perfection. According to this view, early alchemists such as Zosimos of Panopolis (c. AD 300) highlighted the spiritual nature of the alchemical quest, symbolic of a religious regeneration of the human soul. This approach is held to have continued in the Middle Ages, as metaphysical aspects, substances, physical states, and material processes are supposed to have been used as metaphors for spiritual entities, spiritual states, and, ultimately, transformation. In this sense, the literal meanings of 'Alchemical Formulas' were like a veil, hiding their true spiritual philosophy. In the Neo-Hermeticist interpretation, both the transmutation of common metals into gold and the universal panacea are held to symbolize evolution from an imperfect, diseased, corruptible, and ephemeral state toward a perfect, healthy, incorruptible, and everlasting state, so the philosopher's stone then represented a mystic key that would make this evolution possible. Applied to the alchemist himself, the twin goal symbolized his evolution from ignorance to enlightenment, and the stone represented a hidden spiritual truth or power that would lead to that goal. In texts that are held to have been written according to this view, the cryptic alchemical symbols, diagrams, and textual imagery of late alchemical works are supposed to contain multiple layers of meanings, allegories, and references to other equally cryptic works; which must be laboriously decoded to discover their true meaning. In his 1766 Alchemical Catechism, Théodore Henri de Tschudi denotes that the usage of the metals was merely symbolic: Psychology Alchemical symbolism has been important in depth and analytical psychology and was revived and popularized from near extinction by the Swiss psychologist Carl Gustav Jung. Initially confounded and at odds with alchemy and its images, after being given a copy of the translation of The Secret of the Golden Flower, a Chinese alchemical text, by his friend Richard Wilhelm, Jung discovered a direct correlation or parallels between the symbolic images in the alchemical drawings and the inner, symbolic images coming up in dreams, visions or imaginations during the psychic processes of transformation occurring in his patients. A process, which he called "process of individuation". He regarded the alchemical images as symbols expressing aspects of this "process of individuation" of which the creation of the gold or lapis within were symbols for its origin and goal. Together with his alchemical mystica soror, Jungian Swiss analyst Marie-Louise von Franz, Jung began collecting all the old alchemical texts available, compiled a lexicon of key phrases with cross-references and pored over them. The volumes of work he wrote brought new light into understanding the art of transubstantiation and renewed alchemy's popularity as a symbolic process of coming into wholeness as a human being where opposites brought into contact and inner and outer, spirit and matter are reunited in the hieros gamos or divine marriage. His writings are influential in psychology and for people who have an interest in understanding the importance of dreams, symbols and the unconscious archetypal forces (archetypes) that influence all of life. Both von Franz and Jung have contributed greatly to the subject and work of alchemy and its continued presence in psychology as well as contemporary culture. Jung wrote volumes on alchemy and his magnum opus is Volume 14 of his Collected Works, Mysterium Coniunctionis. Literature Alchemy has had a long-standing relationship with art, seen both in alchemical texts and in mainstream entertainment. Literary alchemy appears throughout the history of English literature from Shakespeare to J. K. Rowling, and also the popular Japanese manga Fullmetal Alchemist. Here, characters or plot structure follow an alchemical magnum opus. In the 14th century, Chaucer began a trend of alchemical satire that can still be seen in recent fantasy works like those of the late Sir Terry Pratchett. Visual artists had a similar relationship with alchemy. While some of them used alchemy as a source of satire, others worked with the alchemists themselves or integrated alchemical thought or symbols in their work. Music was also present in the works of alchemists and continues to influence popular performers. In the last hundred years, alchemists have been portrayed in a magical and spagyric role in fantasy fiction, film, television, novels, comics and video games. Science One goal of alchemy, the transmutation of base substances into gold, is now known to be impossible by chemical means but possible by physical means. Although not financially worthwhile, Gold was synthesized in particle accelerators as early as 1941. See also Alchemical symbol Biological transmutation in Corentin Louis Kervran Cupellation Historicism History of chemistry List of alchemists Nuclear transmutation Outline of alchemy Porta Alchemica Renaissance magic Spagyric Superseded theories in science Synthesis of precious metals Western esotericism Notes References Citations Bibliography Further reading General Lawrence Principe, The Secrets of Alchemy, Chicago, 2013. Jennifer M. Rampling. 2020. The Experimental Fire: Inventing English Alchemy, 1300-1700. University of Chicago Press. Greco-Egyptian alchemy Texts Marcellin Berthelot and Charles-Émile Ruelle (eds.), Collection des anciens alchimistes grecs (CAAG), 3 vols., 1887–1888, Vol 1: https://gallica.bnf.fr/ark:/12148/bpt6k96492923, Vol 2: https://gallica.bnf.fr/ark:/12148/bpt6k9680734p, Vol. 3: https://gallica.bnf.fr/ark:/12148/bpt6k9634942s. André-Jean Festugière, La Révélation d'Hermès Trismégiste, Paris, Les Belles Lettres, 2014 (, OCLC 897235256). Robert Halleux and Henri-Dominique Saffrey (eds.), Les alchimistes grecs, t. 1 : Papyrus de Leyde – Papyrus de Stockholm – Recettes, Paris, Les Belles Lettres, 1981. Otto Lagercrantz (ed), Papyrus Graecus Holmiensis, Uppsala, A.B. Akademiska Bokhandeln, 1913, https://archive.org/details/papyrusgraecusho00lage/page/n8. Michèle Mertens and Henri-Dominique Saffrey (ed.), Les alchimistes grecs, t. 4.1 : Zosime de Panopolis. Mémoires authentiques, Paris, Les Belles Lettres, 1995. Andrée Collinet and Henri-Dominique Saffrey (ed.), Les alchimistes grecs, t. 10 : L'Anonyme de Zuretti ou l'Art sacré and divin de la chrysopée par un anonyme, Paris, Les Belles Lettres, 2000. Andrée Collinet (ed), Les alchimistes grecs, t. 11 : Recettes alchimiques (Par. Gr. 2419; Holkhamicus 109) – Cosmas le Hiéromoine – Chrysopée, Paris, Les Belles Lettres, 2000. Matteo Martelli (ed), The Four Books of Pseudo-Democritus, Maney Publishing, 2014. Studies Dylan M. Burns, « μίξεώς τινι τέχνῃ κρείττονι : Alchemical Metaphor in the Paraphrase of Shem (NHC VII,1) », Aries 15 (2015), p. 79–106. Alberto Camplani, « Procedimenti magico-alchemici e discorso filosofico ermetico » in Giuliana Lanata (ed.), Il Tardoantico alle soglie del Duemila, ETS, 2000, p. 73–98. Alberto Camplani and Marco Zambon, « Il sacrificio come problema in alcune correnti filosofice di età imperiale », Annali di storia dell'esegesi 19 (2002), p. 59–99. Régine Charron and Louis Painchaud, « 'God is a Dyer,' The Background and Significance of a Puzzling Motif in the Coptic Gospel According to Philip (CG II, 3), Le Muséon 114 (2001), p. 41-50. Régine Charron, « The Apocryphon of John (NHC II,1) and the Greco-Egyptian Alchemical Literature », Vigiliae Christinae 59 (2005), p. 438-456. Philippe Derchain, "L'Atelier des Orfèvres à Dendara et les origines de l'alchimie," Chronique d'Égypte, vol. 65, no 130, 1990, p. 219–242. Korshi Dosoo, « A History of the Theban Magical Library », Bulletin of the American Society of Papyrologists 53 (2016), p. 251–274. Olivier Dufault, Early Greek Alchemy, Patronage and Innovation in Late Antiquity, California Classical Studies, 2019, https://escholarship.org/uc/item/2ks0g83x. Sergio Knipe, « Sacrifice and self-transformation in the alchemical writings of Zosimus of Panopolis », in Christopher Kelly, Richard Flower, Michael Stuart Williams (eds.), Unclassical Traditions. Volume II: Perspectives from East and West in Late Antiquity, Cambridge University Press, 2011, p. 59–69. André-Jean Festugière, La Révélation d'Hermès Trismégiste, Paris, Les Belles Lettres, 2014 , . Kyle A. Fraser, « Zosimos of Panopolis and the Book of Enoch: Alchemy as Forbidden Knowledge », Aries 4.2 (2004), p. 125–147. Kyle A. Fraser, « Baptized in Gnosis: The Spiritual Alchemy of Zosimos of Panopolis », Dionysius 25 (2007), p. 33–54. Kyle A. Fraser, « Distilling Nature’s Secrets: The Sacred Art of Alchemy », in John Scarborough and Paul Keyser (eds.), Oxford Handbook of Science and Medicine in the Classical World, Oxford University Press, 2018, p. 721–742. 2018. https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199734146.001.0001/oxfordhb-9780199734146-e-76. Shannon Grimes, Becoming Gold: Zosimos of Panopolis and the Alchemical Arts in Roman Egypt, Auckland, Rubedo Press, 2018, Paul T. Keyser, « Greco-Roman Alchemy and Coins of Imitation Silver », American Journal of Numismatics 7–8 (1995–1996), p. 209–234. Paul Keyser, « The Longue Durée of Alchemy », in John Scarborough and Paul Keyser (eds.), Oxford Handbook of Science and Medicine in the Classical World, Oxford University Press, 2018, p. 409–430. Jean Letrouit, "Chronologie des alchimistes grecs," in Didier Kahn and Sylvain Matton, Alchimie: art, histoire et mythes, SEHA-Archè, 1995, p. 11–93. Lindsay, Jack. The Origins of Alchemy in Greco-Roman Egypt. Barnes & Noble, 1970. Paul Magdalino and Maria Mavroudi (eds.), The Occult Sciences in Byzantium, La Pomme d'or, 2006. Matteo Martelli, « The Alchemical Art of Dyeing: The Fourfold Division of Alchemy and the Enochian Tradition » in Sven Dupré (ed.), Laboratories of Art, Springer, 2014, . Matteo Martelli, « Alchemy, Medicine and Religion: Zosimus of Panopolis and the Egyptian Priests », Religion in the Roman Empire 3.2 (2017), p. 202–220. Gerasimos Merianos, « Alchemy », In A. Kaldellis & N. Siniossoglou (eds.), The Cambridge Intellectual History of Byzantium (pp. 234–251). Cambridge: Cambridge University Press, 2017, . Efthymios Nikolaïdis (ed.), Greek Alchemy from Late Antiquity to Early Modernity, Brepols, 2019, . Daniel Stolzenberg, « Unpropitious Tinctures: Alchemy, Astrology & Gnosis According to Zosimos of Panopolis », Archives internationales d'histoire des sciences 49 (1999), p. 3–31. Cristina Viano, « Byzantine Alchemy, or the Era of Systematization », in John Scarborough and Paul Keyser (eds.), Oxford Handbook of Science and Medicine in the Classical World, Oxford University Press, 2018, p. 943–964. C. Vlachou and al., « Experimental investigation of silvering in late Roman coinage », Material Research Society Symposium Proceedings 712 (2002), p. II9.2.1-II9.2.9, . Early modern Principe, Lawrence and William Newman. Alchemy Tried in the Fire: Starkey, Boyle, and the Fate of Helmontian Chymistry. University of Chicago Press, 2002. External links SHAC: Society for the History of Alchemy and Chemistry ESSWE: European Society for the Study of Western Esotericism Association for the Study of Esotericism The Alchemy Website. – Adam McLean's online collections and academic discussion. Dictionary of the History of Ideas: Alchemy Book of Secrets: Alchemy and the European Imagination, 1500–2000 – A digital exhibition from the Beinecke Rare Book and Manuscript Library at Yale University Othmer MS 2 Alchemical Miscellany at OPenn Alchemy featured topic page on Science History Institute Digital Collections featuring selected manuscripts, rare books, paintings, and ephemera relating to alchemical topics and experimentation. Esotericism Hermeticism History of philosophy History of science

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

580

https://en.wikipedia.org/wiki/Astronomer

Astronomer

An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either observational (by analyzing the data) or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies. A related but distinct subject is physical cosmology, which studies the Universe as a whole. Types Astronomers usually fall under either of two main types: observational and theoretical. Observational astronomers make direct observations of celestial objects and analyze the data. In contrast, theoretical astronomers create and investigate models of things that cannot be observed. Because it takes millions to billions of years for a system of stars or a galaxy to complete a life cycle, astronomers must observe snapshots of different systems at unique points in their evolution to determine how they form, evolve, and die. They use these data to create models or simulations to theorize how different celestial objects work. Further subcategories under these two main branches of astronomy include planetary astronomy, galactic astronomy, or physical cosmology. Academic Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws. Today, that distinction has mostly disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are highly educated individuals who typically have a PhD in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although they quite often have other duties such as teaching, building instruments, or aiding in the operation of an observatory. The American Astronomical Society, which is the major organization of professional astronomers in North America, has approximately 7,000 members. This number includes scientists from other fields such as physics, geology, and engineering, whose research interests are closely related to astronomy. The International Astronomical Union comprises almost 10,145 members from 70 different countries who are involved in astronomical research at the PhD level and beyond. Contrary to the classical image of an old astronomer peering through a telescope through the dark hours of the night, it is far more common to use a charge-coupled device (CCD) camera to record a long, deep exposure, allowing a more sensitive image to be created because the light is added over time. Before CCDs, photographic plates were a common method of observation. Modern astronomers spend relatively little time at telescopes usually just a few weeks per year. Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities also have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field. Those who become astronomers usually have a broad background in maths, sciences and computing in high school. Taking courses that teach how to research, write, and present papers are also invaluable. In college/university most astronomers get a PhD in astronomy or physics. Amateur astronomers While there is a relatively low number of professional astronomers, the field is popular among amateurs. Most cities have amateur astronomy clubs that meet on a regular basis and often host star parties. The Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. Like any hobby, most people who think of themselves as amateur astronomers may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to the very ambitious, who own science-grade telescopes and instruments with which they are able to make their own discoveries and assist professional astronomers in research. See also List of astronomers List of women astronomers List of Muslim astronomers List of French astronomers List of Hungarian astronomers List of Russian astronomers and astrophysicists List of Slovenian astronomers References Sources External links American Astronomical Society European Astronomical Society International Astronomical Union Astronomical Society of the Pacific Space's astronomy news Astronomy Science occupations

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

586

https://en.wikipedia.org/wiki/ASCII

ASCII

ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters. The Internet Assigned Numbers Authority (IANA) prefers the name US-ASCII for this character encoding. ASCII is one of the IEEE milestones. Overview ASCII was developed from telegraph code. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on the ASCII standard began in May 1961, with the first meeting of the American Standards Association's (ASA) (now the American National Standards Institute or ANSI) X3.2 subcommittee. The first edition of the standard was published in 1963, underwent a major revision during 1967, and experienced its most recent update during 1986. Compared to earlier telegraph codes, the proposed Bell code and ASCII were both ordered for more convenient sorting (i.e., alphabetization) of lists and added features for devices other than teleprinters. The use of ASCII format for Network Interchange was described in 1969. That document was formally elevated to an Internet Standard in 2015. Originally based on the English alphabet, ASCII encodes 128 specified characters into seven-bit integers as shown by the ASCII chart above. Ninety-five of the encoded characters are printable: these include the digits 0 to 9, lowercase letters a to z, uppercase letters A to Z, and punctuation symbols. In addition, the original ASCII specification included 33 non-printing control codes which originated with Teletype machines; most of these are now obsolete, although a few are still commonly used, such as the carriage return, line feed, and tab codes. For example, lowercase i would be represented in the ASCII encoding by binary 1101001 = hexadecimal 69 (i is the ninth letter) = decimal 105. History The American Standard Code for Information Interchange (ASCII) was developed under the auspices of a committee of the American Standards Association (ASA), called the X3 committee, by its X3.2 (later X3L2) subcommittee, and later by that subcommittee's X3.2.4 working group (now INCITS). The ASA later became the United States of America Standards Institute (USASI), and ultimately became the American National Standards Institute (ANSI). With the other special characters and control codes filled in, ASCII was published as ASA X3.4-1963, leaving 28 code positions without any assigned meaning, reserved for future standardization, and one unassigned control code. There was some debate at the time whether there should be more control characters rather than the lowercase alphabet. The indecision did not last long: during May 1963 the CCITT Working Party on the New Telegraph Alphabet proposed to assign lowercase characters to sticks 6 and 7, and International Organization for Standardization TC 97 SC 2 voted during October to incorporate the change into its draft standard. The X3.2.4 task group voted its approval for the change to ASCII at its May 1963 meeting. Locating the lowercase letters in sticks 6 and 7 caused the characters to differ in bit pattern from the upper case by a single bit, which simplified case-insensitive character matching and the construction of keyboards and printers. The X3 committee made other changes, including other new characters (the brace and vertical bar characters), renaming some control characters (SOM became start of header (SOH)) and moving or removing others (RU was removed). ASCII was subsequently updated as USAS X3.4-1967, then USAS X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986. Revisions of the ASCII standard: ASA X3.4-1963 ASA X3.4-1965 (approved, but not published, nevertheless used by IBM 2260 & 2265 Display Stations and IBM 2848 Display Control) USAS X3.4-1967 USAS X3.4-1968 ANSI X3.4-1977 ANSI X3.4-1986 ANSI X3.4-1986 (R1992) ANSI X3.4-1986 (R1997) ANSI INCITS 4-1986 (R2002) ANSI INCITS 4-1986 (R2007) (ANSI) INCITS 4-1986[R2012] (ANSI) INCITS 4-1986[R2017] In the X3.15 standard, the X3 committee also addressed how ASCII should be transmitted (least significant bit first), and how it should be recorded on perforated tape. They proposed a 9-track standard for magnetic tape, and attempted to deal with some punched card formats. Design considerations Bit width The X3.2 subcommittee designed ASCII based on the earlier teleprinter encoding systems. Like other character encodings, ASCII specifies a correspondence between digital bit patterns and character symbols (i.e. graphemes and control characters). This allows digital devices to communicate with each other and to process, store, and communicate character-oriented information such as written language. Before ASCII was developed, the encodings in use included 26 alphabetic characters, 10 numerical digits, and from 11 to 25 special graphic symbols. To include all these, and control characters compatible with the Comité Consultatif International Téléphonique et Télégraphique (CCITT) International Telegraph Alphabet No. 2 (ITA2) standard of 1924, FIELDATA (1956), and early EBCDIC (1963), more than 64 codes were required for ASCII. ITA2 was in turn based on the 5-bit telegraph code that Émile Baudot invented in 1870 and patented in 1874. The committee debated the possibility of a shift function (like in ITA2), which would allow more than 64 codes to be represented by a six-bit code. In a shifted code, some character codes determine choices between options for the following character codes. It allows compact encoding, but is less reliable for data transmission, as an error in transmitting the shift code typically makes a long part of the transmission unreadable. The standards committee decided against shifting, and so ASCII required at least a seven-bit code. The committee considered an eight-bit code, since eight bits (octets) would allow two four-bit patterns to efficiently encode two digits with binary-coded decimal. However, it would require all data transmission to send eight bits when seven could suffice. The committee voted to use a seven-bit code to minimize costs associated with data transmission. Since perforated tape at the time could record eight bits in one position, it also allowed for a parity bit for error checking if desired. Eight-bit machines (with octets as the native data type) that did not use parity checking typically set the eighth bit to 0. Internal organization The code itself was patterned so that most control codes were together and all graphic codes were together, for ease of identification. The first two so-called ASCII sticks (32 positions) were reserved for control characters. The "space" character had to come before graphics to make sorting easier, so it became position 20hex; for the same reason, many special signs commonly used as separators were placed before digits. The committee decided it was important to support uppercase 64-character alphabets, and chose to pattern ASCII so it could be reduced easily to a usable 64-character set of graphic codes, as was done in the DEC SIXBIT code (1963). Lowercase letters were therefore not interleaved with uppercase. To keep options available for lowercase letters and other graphics, the special and numeric codes were arranged before the letters, and the letter A was placed in position 41hex to match the draft of the corresponding British standard. The digits 0–9 are prefixed with 011, but the remaining 4 bits correspond to their respective values in binary, making conversion with binary-coded decimal straightforward. Many of the non-alphanumeric characters were positioned to correspond to their shifted position on typewriters; an important subtlety is that these were based on mechanical typewriters, not electric typewriters. Mechanical typewriters followed the de facto standard set by the Remington No. 2 (1878), the first typewriter with a shift key, and the shifted values of 23456789- were "#$%_&'() early typewriters omitted 0 and 1, using O (capital letter o) and l (lowercase letter L) instead, but 1! and 0) pairs became standard once 0 and 1 became common. Thus, in ASCII !"#$% were placed in the second stick, positions 1–5, corresponding to the digits 1–5 in the adjacent stick. The parentheses could not correspond to 9 and 0, however, because the place corresponding to 0 was taken by the space character. This was accommodated by removing _ (underscore) from 6 and shifting the remaining characters, which corresponded to many European typewriters that placed the parentheses with 8 and 9. This discrepancy from typewriters led to bit-paired keyboards, notably the Teletype Model 33, which used the left-shifted layout corresponding to ASCII, differently from traditional mechanical typewriters. Electric typewriters, notably the IBM Selectric (1961), used a somewhat different layout that has become de facto standard on computers following the IBM PC (1981), especially Model M (1984) and thus shift values for symbols on modern keyboards do not correspond as closely to the ASCII table as earlier keyboards did. The /? pair also dates to the No. 2, and the ,< .> pairs were used on some keyboards (others, including the No. 2, did not shift , (comma) or . (full stop) so they could be used in uppercase without unshifting). However, ASCII split the ;: pair (dating to No. 2), and rearranged mathematical symbols (varied conventions, commonly -* =+) to :* ;+ -=. Some then-common typewriter characters were not included, notably ½ ¼ ¢, while ^ ` ~ were included as diacritics for international use, and < > for mathematical use, together with the simple line characters \ | (in addition to common /). The @ symbol was not used in continental Europe and the committee expected it would be replaced by an accented À in the French variation, so the @ was placed in position 40hex, right before the letter A. The control codes felt essential for data transmission were the start of message (SOM), end of address (EOA), end of message (EOM), end of transmission (EOT), "who are you?" (WRU), "are you?" (RU), a reserved device control (DC0), synchronous idle (SYNC), and acknowledge (ACK). These were positioned to maximize the Hamming distance between their bit patterns. Character order ASCII-code order is also called ASCIIbetical order. Collation of data is sometimes done in this order rather than "standard" alphabetical order (collating sequence). The main deviations in ASCII order are: All uppercase come before lowercase letters; for example, "Z" precedes "a" Digits and many punctuation marks come before letters An intermediate order converts uppercase letters to lowercase before comparing ASCII values. Character groups Control characters ASCII reserves the first 32 codes (numbers 0–31 decimal) for control characters: codes originally intended not to represent printable information, but rather to control devices (such as printers) that make use of ASCII, or to provide meta-information about data streams such as those stored on magnetic tape. For example, character 10 represents the "line feed" function (which causes a printer to advance its paper), and character 8 represents "backspace". refers to control characters that do not include carriage return, line feed or white space as non-whitespace control characters. Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing the structure or appearance of text within a document. Other schemes, such as markup languages, address page and document layout and formatting. The original ASCII standard used only short descriptive phrases for each control character. The ambiguity this caused was sometimes intentional, for example where a character would be used slightly differently on a terminal link than on a data stream, and sometimes accidental, for example with the meaning of "delete". Probably the most influential single device affecting the interpretation of these characters was the Teletype Model 33 ASR, which was a printing terminal with an available paper tape reader/punch option. Paper tape was a very popular medium for long-term program storage until the 1980s, less costly and in some ways less fragile than magnetic tape. In particular, the Teletype Model 33 machine assignments for codes 17 (Control-Q, DC1, also known as XON), 19 (Control-S, DC3, also known as XOFF), and 127 (Delete) became de facto standards. The Model 33 was also notable for taking the description of Control-G (code 7, BEL, meaning audibly alert the operator) literally, as the unit contained an actual bell which it rang when it received a BEL character. Because the keytop for the O key also showed a left-arrow symbol (from ASCII-1963, which had this character instead of underscore), a noncompliant use of code 15 (Control-O, Shift In) interpreted as "delete previous character" was also adopted by many early timesharing systems but eventually became neglected. When a Teletype 33 ASR equipped with the automatic paper tape reader received a Control-S (XOFF, an abbreviation for transmit off), it caused the tape reader to stop; receiving Control-Q (XON, "transmit on") caused the tape reader to resume. This so-called flow control technique became adopted by several early computer operating systems as a "handshaking" signal warning a sender to stop transmission because of impending buffer overflow; it persists to this day in many systems as a manual output control technique. On some systems, Control-S retains its meaning but Control-Q is replaced by a second Control-S to resume output. The 33 ASR also could be configured to employ Control-R (DC2) and Control-T (DC4) to start and stop the tape punch; on some units equipped with this function, the corresponding control character lettering on the keycap above the letter was TAPE and TAPE respectively. Delete vs Backspace The Teletype could not move its typehead backwards, so it did not have a key on its keyboard to send a BS (backspace). Instead, there was a key marked that sent code 127 (DEL). The purpose of this key was to erase mistakes in a manually-input paper tape: the operator had to push a button on the tape punch to back it up, then type the rubout, which punched all holes and replaced the mistake with a character that was intended to be ignored. Teletypes were commonly used with the less-expensive computers from Digital Equipment Corporation; these systems had to use what keys were available, and thus the DEL code was assigned to erase the previous character. Because of this, DEC video terminals (by default) sent the DEL code for the key marked "Backspace" while the separate key marked "Delete" sent an escape sequence; many other competing terminals sent a BS code for the Backspace key. The Unix terminal driver could only use one code to erase the previous character, this could be set to BS or DEL, but not both, resulting in recurring situations of ambiguity where users had to decide depending on what terminal they were using (shells that allow line editing, such as ksh, bash, and zsh, understand both). The assumption that no key sent a BS code allowed Control+H to be used for other purposes, such as the "help" prefix command in GNU Emacs. Escape Many more of the control codes have been assigned meanings quite different from their original ones. The "escape" character (ESC, code 27), for example, was intended originally to allow sending of other control characters as literals instead of invoking their meaning, a so-called "escape sequence". This is the same meaning of "escape" encountered in URL encodings, C language strings, and other systems where certain characters have a reserved meaning. Over time this interpretation has been co-opted and has eventually been changed. In modern usage, an ESC sent to the terminal usually indicates the start of a command sequence usually in the form of a so-called "ANSI escape code" (or, more properly, a "Control Sequence Introducer") from ECMA-48 (1972) and its successors, beginning with ESC followed by a "[" (left-bracket) character. In contrast, an ESC sent from the terminal is most often used as an out-of-band character used to terminate an operation or special mode, as in the TECO and vi text editors. In graphical user interface (GUI) and windowing systems, ESC generally causes an application to abort its current operation or to exit (terminate) altogether. End of Line The inherent ambiguity of many control characters, combined with their historical usage, created problems when transferring "plain text" files between systems. The best example of this is the newline problem on various operating systems. Teletype machines required that a line of text be terminated with both "Carriage Return" (which moves the printhead to the beginning of the line) and "Line Feed" (which advances the paper one line without moving the printhead). The name "Carriage Return" comes from the fact that on a manual typewriter the carriage holding the paper moved while the position where the typebars struck the ribbon remained stationary. The entire carriage had to be pushed (returned) to the right in order to position the left margin of the paper for the next line. DEC operating systems (OS/8, RT-11, RSX-11, RSTS, TOPS-10, etc.) used both characters to mark the end of a line so that the console device (originally Teletype machines) would work. By the time so-called "glass TTYs" (later called CRTs or "dumb terminals") came along, the convention was so well established that backward compatibility necessitated continuing to follow it. When Gary Kildall created CP/M, he was inspired by some of the command line interface conventions used in DEC's RT-11 operating system. Until the introduction of PC DOS in 1981, IBM had no influence in this because their 1970s operating systems used EBCDIC encoding instead of ASCII, and they were oriented toward punch-card input and line printer output on which the concept of "carriage return" was meaningless. IBM's PC DOS (also marketed as MS-DOS by Microsoft) inherited the convention by virtue of being loosely based on CP/M, and Windows in turn inherited it from MS-DOS. Unfortunately, requiring two characters to mark the end of a line introduces unnecessary complexity and ambiguity as to how to interpret each character when encountered by itself. To simplify matters, plain text data streams, including files, on Multics used line feed (LF) alone as a line terminator. Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. On the other hand, the original Macintosh OS, Apple DOS, and ProDOS used carriage return (CR) alone as a line terminator; however, since Apple has now replaced these obsolete operating systems with the Unix-based macOS operating system, they now use line feed (LF) as well. The Radio Shack TRS-80 also used a lone CR to terminate lines. Computers attached to the ARPANET included machines running operating systems such as TOPS-10 and TENEX using CR-LF line endings; machines running operating systems such as Multics using LF line endings; and machines running operating systems such as OS/360 that represented lines as a character count followed by the characters of the line and which used EBCDIC rather than ASCII encoding. The Telnet protocol defined an ASCII "Network Virtual Terminal" (NVT), so that connections between hosts with different line-ending conventions and character sets could be supported by transmitting a standard text format over the network. Telnet used ASCII along with CR-LF line endings, and software using other conventions would translate between the local conventions and the NVT. The File Transfer Protocol adopted the Telnet protocol, including use of the Network Virtual Terminal, for use when transmitting commands and transferring data in the default ASCII mode. This adds complexity to implementations of those protocols, and to other network protocols, such as those used for E-mail and the World Wide Web, on systems not using the NVT's CR-LF line-ending convention. End of File/Stream The PDP-6 monitor, and its PDP-10 successor TOPS-10, used Control-Z (SUB) as an end-of-file indication for input from a terminal. Some operating systems such as CP/M tracked file length only in units of disk blocks, and used Control-Z to mark the end of the actual text in the file. For these reasons, EOF, or end-of-file, was used colloquially and conventionally as a three-letter acronym for Control-Z instead of SUBstitute. The end-of-text code (ETX), also known as Control-C, was inappropriate for a variety of reasons, while using Z as the control code to end a file is analogous to its position at the end of the alphabet, and serves as a very convenient mnemonic aid. A historically common and still prevalent convention uses the ETX code convention to interrupt and halt a program via an input data stream, usually from a keyboard. In C library and Unix conventions, the null character is used to terminate text strings; such null-terminated strings can be known in abbreviation as ASCIZ or ASCIIZ, where here Z stands for "zero". Control code chart Other representations might be used by specialist equipment, for example ISO 2047 graphics or hexadecimal numbers. Printable characters Codes 20hex to 7Ehex, known as the printable characters, represent letters, digits, punctuation marks, and a few miscellaneous symbols. There are 95 printable characters in total. Code 20hex, the "space" character, denotes the space between words, as produced by the space bar of a keyboard. Since the space character is considered an invisible graphic (rather than a control character) it is listed in the table below instead of in the previous section. Code 7Fhex corresponds to the non-printable "delete" (DEL) control character and is therefore omitted from this chart; it is covered in the previous section's chart. Earlier versions of ASCII used the up arrow instead of the caret (5Ehex) and the left arrow instead of the underscore (5Fhex). Character set Usage ASCII was first used commercially during 1963 as a seven-bit teleprinter code for American Telephone & Telegraph's TWX (TeletypeWriter eXchange) network. TWX originally used the earlier five-bit ITA2, which was also used by the competing Telex teleprinter system. Bob Bemer introduced features such as the escape sequence. His British colleague Hugh McGregor Ross helped to popularize this work according to Bemer, "so much so that the code that was to become ASCII was first called the Bemer–Ross Code in Europe". Because of his extensive work on ASCII, Bemer has been called "the father of ASCII". On March 11, 1968, US President Lyndon B. Johnson mandated that all computers purchased by the United States Federal Government support ASCII, stating: I have also approved recommendations of the Secretary of Commerce [Luther H. Hodges] regarding standards for recording the Standard Code for Information Interchange on magnetic tapes and paper tapes when they are used in computer operations. All computers and related equipment configurations brought into the Federal Government inventory on and after July 1, 1969, must have the capability to use the Standard Code for Information Interchange and the formats prescribed by the magnetic tape and paper tape standards when these media are used. ASCII was the most common character encoding on the World Wide Web until December 2007, when UTF-8 encoding surpassed it; UTF-8 is backward compatible with ASCII. Variants and derivations As computer technology spread throughout the world, different standards bodies and corporations developed many variations of ASCII to facilitate the expression of non-English languages that used Roman-based alphabets. One could class some of these variations as "ASCII extensions", although some misuse that term to represent all variants, including those that do not preserve ASCII's character-map in the 7-bit range. Furthermore, the ASCII extensions have also been mislabelled as ASCII. 7-bit codes From early in its development, ASCII was intended to be just one of several national variants of an international character code standard. Other international standards bodies have ratified character encodings such as ISO 646 (1967) that are identical or nearly identical to ASCII, with extensions for characters outside the English alphabet and symbols used outside the United States, such as the symbol for the United Kingdom's pound sterling (£); e.g. with code page 1104. Almost every country needed an adapted version of ASCII, since ASCII suited the needs of only the US and a few other countries. For example, Canada had its own version that supported French characters. Many other countries developed variants of ASCII to include non-English letters (e.g. é, ñ, ß, Ł), currency symbols (e.g. £, ¥), etc. See also YUSCII (Yugoslavia). It would share most characters in common, but assign other locally useful characters to several code points reserved for "national use". However, the four years that elapsed between the publication of ASCII-1963 and ISO's first acceptance of an international recommendation during 1967 caused ASCII's choices for the national use characters to seem to be de facto standards for the world, causing confusion and incompatibility once other countries did begin to make their own assignments to these code points. ISO/IEC 646, like ASCII, is a 7-bit character set. It does not make any additional codes available, so the same code points encoded different characters in different countries. Escape codes were defined to indicate which national variant applied to a piece of text, but they were rarely used, so it was often impossible to know what variant to work with and, therefore, which character a code represented, and in general, text-processing systems could cope with only one variant anyway. Because the bracket and brace characters of ASCII were assigned to "national use" code points that were used for accented letters in other national variants of ISO/IEC 646, a German, French, or Swedish, etc. programmer using their national variant of ISO/IEC 646, rather than ASCII, had to write, and, thus, read, something such as ä aÄiÜ = 'Ön'; ü instead of { a[i] = '\n'; } C trigraphs were created to solve this problem for ANSI C, although their late introduction and inconsistent implementation in compilers limited their use. Many programmers kept their computers on US-ASCII, so plain-text in Swedish, German etc. (for example, in e-mail or Usenet) contained "{, }" and similar variants in the middle of words, something those programmers got used to. For example, a Swedish programmer mailing another programmer asking if they should go for lunch, could get "N{ jag har sm|rg}sar" as the answer, which should be "Nä jag har smörgåsar" meaning "No I've got sandwiches". In Japan and Korea, still a variation of ASCII is used, in which the backslash (5C hex) is rendered as ¥ (a Yen sign, in Japan) or ₩ (a Won sign, in Korea). This means that, for example, the file path C:\Users\Smith is shown as C:¥Users¥Smith (in Japan) or C:₩Users₩Smith (in Korea). 8-bit codes Eventually, as 8-, 16-, and 32-bit (and later 64-bit) computers began to replace 12-, 18-, and 36-bit computers as the norm, it became common to use an 8-bit byte to store each character in memory, providing an opportunity for extended, 8-bit relatives of ASCII. In most cases these developed as true extensions of ASCII, leaving the original character-mapping intact, but adding additional character definitions after the first 128 (i.e., 7-bit) characters. Encodings include ISCII (India), VISCII (Vietnam). Although these encodings are sometimes referred to as ASCII, true ASCII is defined strictly only by the ANSI standard. Most early home computer systems developed their own 8-bit character sets containing line-drawing and game glyphs, and often filled in some or all of the control characters from 0 to 31 with more graphics. Kaypro CP/M computers used the "upper" 128 characters for the Greek alphabet. The PETSCII code Commodore International used for their 8-bit systems is probably unique among post-1970 codes in being based on ASCII-1963, instead of the more common ASCII-1967, such as found on the ZX Spectrum computer. Atari 8-bit computers and Galaksija computers also used ASCII variants. The IBM PC defined code page 437, which replaced the control characters with graphic symbols such as smiley faces, and mapped additional graphic characters to the upper 128 positions. Operating systems such as DOS supported these code pages, and manufacturers of IBM PCs supported them in hardware. Digital Equipment Corporation developed the Multinational Character Set (DEC-MCS) for use in the popular VT220 terminal as one of the first extensions designed more for international languages than for block graphics. The Macintosh defined Mac OS Roman and Postscript also defined a set, both of these contained both international letters and typographic punctuation marks instead of graphics, more like modern character sets. The ISO/IEC 8859 standard (derived from the DEC-MCS) finally provided a standard that most systems copied (at least as accurately as they copied ASCII, but with many substitutions). A popular further extension designed by Microsoft, Windows-1252 (often mislabeled as ISO-8859-1), added the typographic punctuation marks needed for traditional text printing. ISO-8859-1, Windows-1252, and the original 7-bit ASCII were the most common character encodings until 2008 when UTF-8 became more common. ISO/IEC 4873 introduced 32 additional control codes defined in the 80–9F hexadecimal range, as part of extending the 7-bit ASCII encoding to become an 8-bit system. Unicode Unicode and the ISO/IEC 10646 Universal Character Set (UCS) have a much wider array of characters and their various encoding forms have begun to supplant ISO/IEC 8859 and ASCII rapidly in many environments. While ASCII is limited to 128 characters, Unicode and the UCS support more characters by separating the concepts of unique identification (using natural numbers called code points) and encoding (to 8-, 16-, or 32-bit binary formats, called UTF-8, UTF-16, and UTF-32, respectively). ASCII was incorporated into the Unicode (1991) character set as the first 128 symbols, so the 7-bit ASCII characters have the same numeric codes in both sets. This allows UTF-8 to be backward compatible with 7-bit ASCII, as a UTF-8 file containing only ASCII characters is identical to an ASCII file containing the same sequence of characters. Even more importantly, forward compatibility is ensured as software that recognizes only 7-bit ASCII characters as special and does not alter bytes with the highest bit set (as is often done to support 8-bit ASCII extensions such as ISO-8859-1) will preserve UTF-8 data unchanged. See also 3568 ASCII, an asteroid named after the character encoding Alt codes Ascii85 ASCII art ASCII Ribbon Campaign Basic Latin (Unicode block) (ASCII as a subset of Unicode) Extended ASCII HTML decimal character rendering Jargon File, a glossary of computer programmer slang which includes a list of common slang names for ASCII characters List of computer character sets List of Unicode characters Notes References Further reading from: External links Computer-related introductions in 1963 Character sets Character encoding Latin-script representations Presentation layer protocols

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

593

https://en.wikipedia.org/wiki/Animation

Animation

Animation is a method in which figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most animations are made with computer-generated imagery (CGI). Computer animation can be very detailed 3D animation, while 2D computer animation (which may have the look of traditional animation) can be used for stylistic reasons, low bandwidth, or faster real-time renderings. Other common animation methods apply a stop motion technique to two- and three-dimensional objects like paper cutouts, puppets, or clay figures. An animated cartoon is an animated film, usually a short film aimed at children and featuring an exaggerated visual style. The style takes inspiration from comic strips, often featuring anthropomorphic animals, superheroes, or the adventures of child protagonists. Especially with animals that form a natural predator/prey relationship (e.g. cats and mice, coyotes and birds) the action often centers around violent pratfalls such as falls, collisions and explosions that would be lethal in real life. Commonly, animators achieved the effect by a rapid succession of images that minimally differ from each other. The illusion—as in motion pictures in general—is thought to rely on the phi phenomenon and beta movement, but the exact causes are still uncertain. Analog mechanical animation media that rely on the rapid display of sequential images include the phénakisticope, zoetrope, flip book, praxinoscope, and film. Television and video are popular electronic animation media that originally were analog and now operate digitally. For display on computers, technology such as the animated GIF and Flash animation were developed. In addition to short films, feature films, television series, animated GIFs, and other media dedicated to the display of moving images, animation is also prevalent in video games, motion graphics, user interfaces, and visual effects. The physical movement of image parts through simple mechanics—for instance moving images in magic lantern shows—can also be considered animation. The mechanical manipulation of three-dimensional puppets and objects to emulate living beings has a very long history in automata. Electronic automata were popularized by Disney as animatronics. Etymology The word "animation" stems from the Latin "animātiōn", stem of "animātiō", meaning "a bestowing of life". The primary meaning of the English word is "liveliness" and has been in use much longer than the meaning of "moving image medium". History Before cinematography Hundreds of years before the introduction of true animation, people all over the world enjoyed shows with moving figures that were created and manipulated manually in puppetry, automata, shadow play, and the magic lantern. The multi-media phantasmagoria shows that were very popular in European theatres from the late 18th century through the first half of the 19th century, featured lifelike projections of moving ghosts and other frightful imagery in motion. In 1833, the stroboscopic disc (better known as the phénakisticope) introduced the principle of modern animation with sequential images that were shown one by one in quick succession to form an optical illusion of motion pictures. Series of sequential images had occasionally been made over thousands of years, but the stroboscopic disc provided the first method to represent such images in fluent motion and for the first time had artists creating series with a proper systematic breakdown of movements. The stroboscopic animation principle was also applied in the zoetrope (1866), the flip book (1868) and the praxinoscope (1877). A typical 19th-century animation contained about 12 images that were displayed as a continuous loop by spinning a device manually. The flip book often contained more pictures and had a beginning and end, but its animation would not last longer than a few seconds. The first to create much longer sequences seems to have been Charles-Émile Reynaud, who between 1892 and 1900 had much success with his 10- to 15-minute-long Pantomimes Lumineuses. Silent era When cinematography eventually broke through in 1895 after animated pictures had been known for decades, the wonder of the realistic details in the new medium was seen as its biggest accomplishment. Animation on film was not commercialized until a few years later by manufacturers of optical toys, with chromolithography film loops (often traced from live-action footage) for adapted toy magic lanterns intended for kids to use at home. It would take some more years before animation reached movie theaters. After earlier experiments by movie pioneers J. Stuart Blackton, Arthur Melbourne-Cooper, Segundo de Chomón, and Edwin S. Porter (among others), Blackton's The Haunted Hotel (1907) was the first huge stop motion success, baffling audiences by showing objects that apparently moved by themselves in full photographic detail, without signs of any known stage trick. Émile Cohl's Fantasmagorie (1908) is the oldest known example of what became known as traditional (hand-drawn) animation. Other great artistic and very influential short films were created by Ladislas Starevich with his puppet animations since 1910 and by Winsor McCay with detailed drawn animation in films such as Little Nemo (1911) and Gertie the Dinosaur (1914). During the 1910s, the production of animated "cartoons" became an industry in the US. Successful producer John Randolph Bray and animator Earl Hurd, patented the cel animation process that dominated the animation industry for the rest of the century. Felix the Cat, who debuted in 1919, became the first animated superstar. American golden age In 1928, Steamboat Willie, featuring Mickey Mouse and Minnie Mouse, popularized film with synchronized sound and put Walt Disney's studio at the forefront of the animation industry. The enormous success of Mickey Mouse is seen as the start of the golden age of American animation that would last until the 1960s. The United States dominated the world market of animation with a plethora of cel-animated theatrical shorts. Several studios would introduce characters that would become very popular and would have long-lasting careers, including Maria Butinova Studios' Mapmo (1924), The Leo King Knott (1931), Walt Disney Productions' Goofy (1932) and Donald Duck (1934), Warner Bros. Cartoons' Looney Tunes characters like Porky Pig (1935), Daffy Duck (1937), Bugs Bunny (1938–1940), Tweety (1941–1942), Sylvester the Cat (1945), Wile E. Coyote and Road Runner (1949), Fleischer Studios/Paramount Cartoon Studios' Betty Boop (1930), Popeye (1933), Superman (1941) and Casper (1945), MGM cartoon studio's Tom and Jerry (1940) and Droopy, Walter Lantz Productions/Universal Studio Cartoons' Woody Woodpecker (1940), Terrytoons/20th Century Fox's Dinky Duck (1939), Mighty Mouse (1942) and Heckle and Jeckle (1946) and United Artists' Pink Panther (1963). Features before CGI In 1917, Italian-Argentine director Quirino Cristiani made the first feature-length film El Apóstol (now lost), which became a critical and commercial success. It was followed by Cristiani's Sin dejar rastros in 1918, but one day after its premiere, the film was confiscated by the government. After working on it for three years, Lotte Reiniger released the German feature-length silhouette animation Die Abenteuer des Prinzen Achmed in 1926, the oldest extant animated feature. In 1937, Walt Disney Studios premiered their first animated feature, Snow White and the Seven Dwarfs, still one of the highest-grossing traditional animation features . The Fleischer studios followed this example in 1939 with Gulliver's Travels with some success. Partly due to foreign markets being cut off by the Second World War, Disney's next features Pinocchio, Fantasia (both 1940) and Fleischer Studios' second animated feature Mr. Bug Goes to Town (1941–1942) failed at the box office. For decades afterward, Disney would be the only American studio to regularly produce animated features, until Ralph Bakshi became the first to also release more than a handful features. Sullivan-Bluth Studios began to regularly produce animated features starting with An American Tail in 1986. Although relatively few titles became as successful as Disney's features, other countries developed their own animation industries that produced both short and feature theatrical animations in a wide variety of styles, relatively often including stop motion and cutout animation techniques. Russia's Soyuzmultfilm animation studio, founded in 1936, produced 20 films (including shorts) per year on average and reached 1,582 titles in 2018. China, Czechoslovakia / Czech Republic, Italy, France, and Belgium were other countries that more than occasionally released feature films, while Japan became a true powerhouse of animation production, with its own recognizable and influential anime style of effective limited animation. Television Animation became very popular on television since the 1950s, when television sets started to become common in most developed countries. Cartoons were mainly programmed for children, on convenient time slots, and especially US youth spent many hours watching Saturday-morning cartoons. Many classic cartoons found a new life on the small screen and by the end of the 1950s, the production of new animated cartoons started to shift from theatrical releases to TV series. Hanna-Barbera Productions was especially prolific and had huge hit series, such as The Flintstones (1960–1966) (the first prime time animated series), Scooby-Doo (since 1969) and Belgian co-production The Smurfs (1981–1989). The constraints of American television programming and the demand for an enormous quantity resulted in cheaper and quicker limited animation methods and much more formulaic scripts. Quality dwindled until more daring animation surfaced in the late 1980s and in the early 1990s with hit series such as The Simpsons (since 1989) as part of a "renaissance" of American animation. While US animated series also spawned successes internationally, many other countries produced their own child-oriented programming, relatively often preferring stop motion and puppetry over cel animation. Japanese anime TV series became very successful internationally since the 1960s, and European producers looking for affordable cel animators relatively often started co-productions with Japanese studios, resulting in hit series such as Barbapapa (The Netherlands/Japan/France 1973–1977), Wickie und die starken Männer/小さなバイキング ビッケ (Vicky the Viking) (Austria/Germany/Japan 1974), and The Jungle Book (Italy/Japan 1989). Switch from cels to computers Computer animation was gradually developed since the 1940s. 3D wireframe animation started popping up in the mainstream in the 1970s, with an early (short) appearance in the sci-fi thriller Futureworld (1976). The Rescuers Down Under was the first feature film to be completely created digitally without a camera. It was produced in a style that's very similar to traditional cel animation on the Computer Animation Production System (CAPS), developed by The Walt Disney Company in collaboration with Pixar in the late 1980s. The so-called 3D style, more often associated with computer animation, has become extremely popular since Pixar's Toy Story (1995), the first computer-animated feature in this style. Most of the cel animation studios switched to producing mostly computer animated films around the 1990s, as it proved cheaper and more profitable. Not only the very popular 3D animation style was generated with computers, but also most of the films and series with a more traditional hand-crafted appearance, in which the charming characteristics of cel animation could be emulated with software, while new digital tools helped developing new styles and effects. Economic status In 2008, the animation market was worth US$68.4 billion. Animated feature-length films returned the highest gross margins (around 52%) of all film genres between 2004 and 2013. Animation as an art and industry continues to thrive as of the early 2020s. Education, propaganda and commercials The clarity of animation makes it a powerful tool for instruction, while its total malleability also allows exaggeration that can be employed to convey strong emotions and to thwart reality. It has therefore been widely used for other purposes than mere entertainment. During World War II, animation was widely exploited for propaganda. Many American studios, including Warner Bros. and Disney, lent their talents and their cartoon characters to convey to the public certain war values. Some countries, including China, Japan and the United Kingdom, produced their first feature-length animation for their war efforts. Animation has been very popular in television commercials, both due to its graphic appeal, and the humour it can provide. Some animated characters in commercials have survived for decades, such as Snap, Crackle and Pop in advertisements for Kellogg's cereals. The legendary animation director Tex Avery was the producer of the first Raid "Kills Bugs Dead" commercials in 1966, which were very successful for the company. Other media, merchandise and theme parks Apart from their success in movie theaters and television series, many cartoon characters would also prove extremely lucrative when licensed for all kinds of merchandise and for other media. Animation has traditionally been very closely related to comic books. While many comic book characters found their way to the screen (which is often the case in Japan, where many manga are adapted into anime), original animated characters also commonly appear in comic books and magazines. Somewhat similarly, characters and plots for video games (an interactive animation medium) have been derived from films and vice versa. Some of the original content produced for the screen can be used and marketed in other media. Stories and images can easily be adapted into children's books and other printed media. Songs and music have appeared on records and as streaming media. While very many animation companies commercially exploit their creations outside moving image media, The Walt Disney Company is the best known and most extreme example. Since first being licensed for a children's writing tablet in 1929, their Mickey Mouse mascot has been depicted on an enormous amount of products, as have many other Disney characters. This may have influenced some pejorative use of Mickey's name, but licensed Disney products sell well, and the so-called Disneyana has many avid collectors, and even a dedicated Disneyana fanclub (since 1984). Disneyland opened in 1955 and features many attractions that were based on Disney's cartoon characters. Its enormous success spawned several other Disney theme parks and resorts. Disney's earnings from the theme parks have relatively often been higher than those from their movies. Criticism Criticism of animation has been common in media and cinema since its inception. With its popularity, a large amount of criticism has arisen, especially animated feature-length films. Many concerns of cultural representation, psychological effects on children have been brought up around the animation industry, which has remained rather politically unchanged and stagnant since its inception into mainstream culture. Awards As with any other form of media, animation has instituted awards for excellence in the field. The original awards for animation were presented by the Academy of Motion Picture Arts and Sciences for animated shorts from the year 1932, during the 5th Academy Awards function. The first winner of the Academy Award was the short Flowers and Trees, a production by Walt Disney Productions. The Academy Award for a feature-length animated motion picture was only instituted for the year 2001, and awarded during the 74th Academy Awards in 2002. It was won by the film Shrek, produced by DreamWorks and Pacific Data Images. Disney Animation and Pixar has produced the most films either to win or be nominated for the award. Beauty and the Beast was the first animated film nominated for Best Picture. Up and Toy Story 3 also received Best Picture nominations after the Academy expanded the number of nominees from five to ten. Academy Award for Best Animated Feature Academy Award for Best Animated Short Film Several other countries have instituted an award for the best-animated feature film as part of their national film awards: Africa Movie Academy Award for Best Animation (since 2008), BAFTA Award for Best Animated Film (since 2006), César Award for Best Animated Film (since 2011), Golden Rooster Award for Best Animation (since 1981), Goya Award for Best Animated Film (since 1989), Japan Academy Prize for Animation of the Year (since 2007), National Film Award for Best Animated Film (since 2006). Also since 2007, the Asia Pacific Screen Award for Best Animated Feature Film has been awarded at the Asia Pacific Screen Awards. Since 2009, the European Film Awards have awarded the European Film Award for Best Animated Film. The Annie Award is another award presented for excellence in the field of animation. Unlike the Academy Awards, the Annie Awards are only received for achievements in the field of animation and not for any other field of technical and artistic endeavour. They were re-organized in 1992 to create a new field for Best Animated Feature. The 1990s winners were dominated by Walt Disney; however, newer studios, led by Pixar & DreamWorks, have now begun to consistently vie for this award. The list of awardees is as follows: Annie Award for Best Animated Feature Annie Award for Best Animated Short Subject Annie Award for Best Animated Television Production Production The creation of non-trivial animation works (i.e., longer than a few seconds) has developed as a form of filmmaking, with certain unique aspects. Traits common to both live-action and animated feature-length films are labor intensity and high production costs. The most important difference is that once a film is in the production phase, the marginal cost of one more shot is higher for animated films than live-action films. It is relatively easy for a director to ask for one more take during principal photography of a live-action film, but every take on an animated film must be manually rendered by animators (although the task of rendering slightly different takes has been made less tedious by modern computer animation). It is pointless for a studio to pay the salaries of dozens of animators to spend weeks creating a visually dazzling five-minute scene if that scene fails to effectively advance the plot of the film. Thus, animation studios starting with Disney began the practice in the 1930s of maintaining story departments where storyboard artists develop every single scene through storyboards, then handing the film over to the animators only after the production team is satisfied that all the scenes make sense as a whole. While live-action films are now also storyboarded, they enjoy more latitude to depart from storyboards (i.e., real-time improvisation). Another problem unique to animation is the requirement to maintain a film's consistency from start to finish, even as films have grown longer and teams have grown larger. Animators, like all artists, necessarily have individual styles, but must subordinate their individuality in a consistent way to whatever style is employed on a particular film. Since the early 1980s, teams of about 500 to 600 people, of whom 50 to 70 are animators, typically have created feature-length animated films. It is relatively easy for two or three artists to match their styles; synchronizing those of dozens of artists is more difficult. This problem is usually solved by having a separate group of visual development artists develop an overall look and palette for each film before the animation begins. Character designers on the visual development team draw model sheets to show how each character should look like with different facial expressions, posed in different positions, and viewed from different angles. On traditionally animated projects, maquettes were often sculpted to further help the animators see how characters would look from different angles. Unlike live-action films, animated films were traditionally developed beyond the synopsis stage through the storyboard format; the storyboard artists would then receive credit for writing the film. In the early 1960s, animation studios began hiring professional screenwriters to write screenplays (while also continuing to use story departments) and screenplays had become commonplace for animated films by the late 1980s. Techniques Traditional Traditional animation (also called cel animation or hand-drawn animation) was the process used for most animated films of the 20th century. The individual frames of a traditionally animated film are photographs of drawings, first drawn on paper. To create the illusion of movement, each drawing differs slightly from the one before it. The animators' drawings are traced or photocopied onto transparent acetate sheets called cels, which are filled in with paints in assigned colors or tones on the side opposite the line drawings. The completed character cels are photographed one-by-one against a painted background by a rostrum camera onto motion picture film. The traditional cel animation process became obsolete by the beginning of the 21st century. Today, animators' drawings and the backgrounds are either scanned into or drawn directly into a computer system. Various software programs are used to color the drawings and simulate camera movement and effects. The final animated piece is output to one of several delivery media, including traditional 35 mm film and newer media with digital video. The "look" of traditional cel animation is still preserved, and the character animators' work has remained essentially the same over the past 70 years. Some animation producers have used the term "tradigital" (a play on the words "traditional" and "digital") to describe cel animation that uses significant computer technology. Examples of traditionally animated feature films include Pinocchio (United States, 1940), Animal Farm (United Kingdom, 1954), Lucky and Zorba (Italy, 1998), and The Illusionist (British-French, 2010). Traditionally animated films produced with the aid of computer technology include The Lion King (US, 1994), The Prince of Egypt (US, 1998), Akira (Japan, 1988), Spirited Away (Japan, 2001), The Triplets of Belleville (France, 2003), and The Secret of Kells (Irish-French-Belgian, 2009). Full Full animation refers to the process of producing high-quality traditionally animated films that regularly use detailed drawings and plausible movement, having a smooth animation. Fully animated films can be made in a variety of styles, from more realistically animated works like those produced by the Walt Disney studio (The Little Mermaid, Beauty and the Beast, Aladdin, The Lion King) to the more 'cartoon' styles of the Warner Bros. animation studio. Many of the Disney animated features are examples of full animation, as are non-Disney works, The Secret of NIMH (US, 1982), The Iron Giant (US, 1999), and Nocturna (Spain, 2007). Fully animated films are animated at 24 frames per second, with a combination of animation on ones and twos, meaning that drawings can be held for one frame out of 24 or two frames out of 24. Limited Limited animation involves the use of less detailed or more stylized drawings and methods of movement usually a choppy or "skippy" movement animation. Limited animation uses fewer drawings per second, thereby limiting the fluidity of the animation. This is a more economic technique. Pioneered by the artists at the American studio United Productions of America, limited animation can be used as a method of stylized artistic expression, as in Gerald McBoing-Boing (US, 1951), Yellow Submarine (UK, 1968), and certain anime produced in Japan. Its primary use, however, has been in producing cost-effective animated content for media for television (the work of Hanna-Barbera, Filmation, and other TV animation studios) and later the Internet (web cartoons). Rotoscoping Rotoscoping is a technique patented by Max Fleischer in 1917 where animators trace live-action movement, frame by frame. The source film can be directly copied from actors' outlines into animated drawings, as in The Lord of the Rings (US, 1978), or used in a stylized and expressive manner, as in Waking Life (US, 2001) and A Scanner Darkly (US, 2006). Some other examples are Fire and Ice (US, 1983), Heavy Metal (1981), and Aku no Hana (Japan, 2013). Live-action blending Live-action/animation is a technique combining hand-drawn characters into live action shots or live-action actors into animated shots. One of the earlier uses was in Koko the Clown when Koko was drawn over live-action footage. Walt Disney and Ub Iwerks created a series of Alice Comedies (1923–1927), in which a live-action girl enters an animated world. Other examples include Allegro Non Troppo (Italy, 1976), Who Framed Roger Rabbit (US, 1988), Volere volare (Italy 1991), Space Jam (US, 1996) and Osmosis Jones (US, 2001). Stop motion Stop-motion animation is used to describe animation created by physically manipulating real-world objects and photographing them one frame of film at a time to create the illusion of movement. There are many different types of stop-motion animation, usually named after the medium used to create the animation. Computer software is widely available to create this type of animation; traditional stop-motion animation is usually less expensive but more time-consuming to produce than current computer animation. Puppet animation Typically involves stop-motion puppet figures interacting in a constructed environment, in contrast to real-world interaction in model animation. The puppets generally have an armature inside of them to keep them still and steady to constrain their motion to particular joints. Examples include The Tale of the Fox (France, 1937), The Nightmare Before Christmas (US, 1993), Corpse Bride (US, 2005), Coraline (US, 2009), the films of Jiří Trnka and the adult animated sketch-comedy television series Robot Chicken (US, 2005–present). Puppetoon Created using techniques developed by George Pal, are puppet-animated films that typically use a different version of a puppet for different frames, rather than simply manipulating one existing puppet. Clay animation or Plasticine animation (Often called claymation, which, however, is a trademarked name). It uses figures made of clay or a similar malleable material to create stop-motion animation. The figures may have an armature or wire frame inside, similar to the related puppet animation (below), that can be manipulated to pose the figures. Alternatively, the figures may be made entirely of clay, in the films of Bruce Bickford, where clay creatures morph into a variety of different shapes. Examples of clay-animated works include The Gumby Show (US, 1957–1967), Mio Mao (Italy, 1974–2005), Morph shorts (UK, 1977–2000), Wallace and Gromit shorts (UK, as of 1989), Jan Švankmajer's Dimensions of Dialogue (Czechoslovakia, 1982), The Trap Door (UK, 1984). Films include Wallace & Gromit: The Curse of the Were-Rabbit, Chicken Run and The Adventures of Mark Twain. Strata-cut animation Most commonly a form of clay animation in which a long bread-like "loaf" of clay, internally packed tight and loaded with varying imagery, is sliced into thin sheets, with the animation camera taking a frame of the end of the loaf for each cut, eventually revealing the movement of the internal images within. Cutout animation A type of stop-motion animation produced by moving two-dimensional pieces of material paper or cloth. Examples include Terry Gilliam's animated sequences from Monty Python's Flying Circus (UK, 1969–1974); Fantastic Planet (France/Czechoslovakia, 1973); Tale of Tales (Russia, 1979), The pilot episode of the adult television sitcom series (and sometimes in episodes) of South Park (US, 1997) and the music video Live for the moment, from Verona Riots band (produced by Alberto Serrano and Nívola Uyá, Spain 2014). Silhouette animation A variant of cutout animation in which the characters are backlit and only visible as silhouettes. Examples include The Adventures of Prince Achmed (Weimar Republic, 1926) and Princes et Princesses (France, 2000). Model animation Refers to stop-motion animation created to interact with and exist as a part of a live-action world. Intercutting, matte effects and split screens are often employed to blend stop-motion characters or objects with live actors and settings. Examples include the work of Ray Harryhausen, as seen in films, Jason and the Argonauts (1963), and the work of Willis H. O'Brien on films, King Kong (1933). Go motion A variant of model animation that uses various techniques to create motion blur between frames of film, which is not present in traditional stop motion. The technique was invented by Industrial Light & Magic and Phil Tippett to create special effect scenes for the film The Empire Strikes Back (1980). Another example is the dragon named "Vermithrax" from the 1981 film Dragonslayer. Object animation Refers to the use of regular inanimate objects in stop-motion animation, as opposed to specially created items. Graphic animation Uses non-drawn flat visual graphic material (photographs, newspaper clippings, magazines, etc.), which are sometimes manipulated frame by frame to create movement. At other times, the graphics remain stationary, while the stop-motion camera is moved to create on-screen action. Brickfilm A subgenre of object animation involving using Lego or other similar brick toys to make an animation. These have had a recent boost in popularity with the advent of video sharing sites, YouTube and the availability of cheap cameras and animation software. Pixilation Involves the use of live humans as stop-motion characters. This allows for a number of surreal effects, including disappearances and reappearances, allowing people to appear to slide across the ground, and other effects. Examples of pixilation include The Secret Adventures of Tom Thumb and Angry Kid shorts, and the Academy Award-winning Neighbours by Norman McLaren. Computer Computer animation encompasses a variety of techniques, the unifying factor being that the animation is created digitally on a computer. 2D animation techniques tend to focus on image manipulation while 3D techniques usually build virtual worlds in which characters and objects move and interact. 3D animation can create images that seem real to the viewer. 2D 2D animation figures are created or edited on the computer using 2D bitmap graphics and 2D vector graphics. This includes automated computerized versions of traditional animation techniques, interpolated morphing, onion skinning and interpolated rotoscoping. 2D animation has many applications, including analog computer animation, Flash animation, and PowerPoint animation. Cinemagraphs are still photographs in the form of an animated GIF file of which part is animated. Final line advection animation is a technique used in 2D animation, to give artists and animators more influence and control over the final product as everything is done within the same department. Speaking about using this approach in Paperman, John Kahrs said that "Our animators can change things, actually erase away the CG underlayer if they want, and change the profile of the arm." 3D 3D animation is digitally modeled and manipulated by an animator. The 3D model maker usually starts by creating a 3D polygon mesh for the animator to manipulate. A mesh typically includes many vertices that are connected by edges and faces, which give the visual appearance of form to a 3D object or 3D environment. Sometimes, the mesh is given an internal digital skeletal structure called an armature that can be used to control the mesh by weighting the vertices. This process is called rigging and can be used in conjunction with key frames to create movement. Other techniques can be applied, mathematical functions (e.g., gravity, particle simulations), simulated fur or hair, and effects, fire and water simulations. These techniques fall under the category of 3D dynamics. Terms Cel-shaded animation is used to mimic traditional animation using computer software. The shading looks stark, with less blending of colors. Examples include Skyland (2007, France), The Iron Giant (1999, United States), Futurama (1999, United States) Appleseed Ex Machina (2007, Japan), The Legend of Zelda: The Wind Waker (2002, Japan), The Legend of Zelda: Breath of the Wild (2017, Japan) Machinima – Films created by screen capturing in video games and virtual worlds. The term originated from the software introduction in the 1980s demoscene, as well as the 1990s recordings of the first-person shooter video game Quake. Motion capture is used when live-action actors wear special suits that allow computers to copy their movements into CG characters. Examples include Polar Express (2004, US), Beowulf (2007, US), A Christmas Carol (2009, US), The Adventures of Tintin (2011, US) kochadiiyan (2014, India) Computer animation is used primarily for animation that attempts to resemble real life, using advanced rendering that mimics in detail skin, plants, water, fire, clouds, etc. Examples include Up (2009, US), How to Train Your Dragon (2010, US) Physically based animation is animation using computer simulations. Mechanical Animatronics is the use of mechatronics to create machines that seem animate rather than robotic. Audio-Animatronics and Autonomatronics is a form of robotics animation, combined with 3-D animation, created by Walt Disney Imagineering for shows and attractions at Disney theme parks move and make noise (generally a recorded speech or song). They are fixed to whatever supports them. They can sit and stand, and they cannot walk. An Audio-Animatron is different from an android-type robot in that it uses prerecorded movements and sounds, rather than responding to external stimuli. In 2009, Disney created an interactive version of the technology called Autonomatronics. Linear Animation Generator is a form of animation by using static picture frames installed in a tunnel or a shaft. The animation illusion is created by putting the viewer in a linear motion, parallel to the installed picture frames. The concept and the technical solution were invented in 2007 by Mihai Girlovan in Romania. Chuckimation is a type of animation created by the makers of the television series Action League Now! in which characters/props are thrown, or chucked from off camera or wiggled around to simulate talking by unseen hands. The magic lantern used mechanical slides to project moving images, probably since Christiaan Huygens invented this early image projector in 1659. Other Hydrotechnics: a technique that includes lights, water, fire, fog, and lasers, with high-definition projections on mist screens. Drawn on film animation: a technique where footage is produced by creating the images directly on film stock; for example, by Norman McLaren, Len Lye and Stan Brakhage. Paint-on-glass animation: a technique for making animated films by manipulating slow drying oil paints on sheets of glass, for example by Aleksandr Petrov. Erasure animation: a technique using traditional 2D media, photographed over time as the artist manipulates the image. For example, William Kentridge is famous for his charcoal erasure films, and Piotr Dumała for his auteur technique of animating scratches on plaster. Pinscreen animation: makes use of a screen filled with movable pins that can be moved in or out by pressing an object onto the screen. The screen is lit from the side so that the pins cast shadows. The technique has been used to create animated films with a range of textural effects difficult to achieve with traditional cel animation. Sand animation: sand is moved around on a back- or front-lighted piece of glass to create each frame for an animated film. This creates an interesting effect when animated because of the light contrast. Flip book: a flip book (sometimes, especially in British English, called a flick book) is a book with a series of pictures that vary gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate by simulating motion or some other change. Flip books are often illustrated books for children, they also are geared towards adults and employ a series of photographs rather than drawings. Flip books are not always separate books, they appear as an added feature in ordinary books or magazines, often in the page corners. Software packages and websites are also available that convert digital video files into custom-made flip books. Character animation Multi-sketching Special effects animation See also Twelve basic principles of animation Animated war film Animation department Animated series Architectural animation Avar Independent animation International Animation Day International Animated Film Association International Tournée of Animation List of film-related topics Motion graphic design Society for Animation Studies Wire-frame model References Citations Sources Journal articles Books Online sources External links The making of an 8-minute cartoon short "Animando", a 12-minute film demonstrating 10 different animation techniques (and teaching how to use them). Bibliography on animation – Websiite "Histoire de la télévision" Cartooning Articles containing video clips Film and video technology

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

594

https://en.wikipedia.org/wiki/Apollo

Apollo

Apollo is one of the Olympian deities in classical Greek and Roman religion and Greek and Roman mythology. The national divinity of the Greeks, Apollo has been recognized as a god of archery, music and dance, truth and prophecy, healing and diseases, the Sun and light, poetry, and more. One of the most important and complex of the Greek gods, he is the son of Zeus and Leto, and the twin brother of Artemis, goddess of the hunt. Seen as the most beautiful god and the ideal of the kouros (ephebe, or a beardless, athletic youth), Apollo is considered to be the most Greek of all the gods. Apollo is known in Greek-influenced Etruscan mythology as Apulu. As the patron deity of Delphi (Apollo Pythios), Apollo is an oracular god—the prophetic deity of the Delphic Oracle. Apollo is the god who affords help and wards off evil; various epithets call him the "averter of evil". Delphic Apollo is the patron of seafarers, foreigners and the protector of fugitives and refugees. Medicine and healing are associated with Apollo, whether through the god himself or mediated through his son Asclepius. Apollo delivered people from epidemics, yet he is also a god who could bring ill-health and deadly plague with his arrows. The invention of archery itself is credited to Apollo and his sister Artemis. Apollo is usually described as carrying a golden bow and a quiver of silver arrows. Apollo's capacity to make youths grow is one of the best attested facets of his panhellenic cult persona. As the protector of young (kourotrophos), Apollo is concerned with the health and education of children. He presided over their passage into adulthood. Long hair, which was the prerogative of boys, was cut at the coming of age (ephebeia) and dedicated to Apollo. Apollo is an important pastoral deity, and was the patron of herdsmen and shepherds. Protection of herds, flocks and crops from diseases, pests and predators were his primary duties. On the other hand, Apollo also encouraged founding new towns and establishment of civil constitution. He is associated with dominion over colonists. He was the giver of laws, and his oracles were consulted before setting laws in a city. As the god of mousike, Apollo presides over all music, songs, dance and poetry. He is the inventor of string-music, and the frequent companion of the Muses, functioning as their chorus leader in celebrations. The lyre is a common attribute of Apollo. In Hellenistic times, especially during the 5th century BCE, as Apollo Helios he became identified among Greeks with Helios, the personification of the sun. In Latin texts, however, there was no conflation of Apollo with Sol among the classical Latin poets until 1st century CE. Apollo and Helios/Sol remained separate beings in literary and mythological texts until the 5th century CE. Etymology Apollo (Attic, Ionic, and Homeric Greek: , Apollōn ( ); Doric: , Apellōn; Arcadocypriot: , Apeilōn; Aeolic: , Aploun; ) The name Apollo—unlike the related older name Paean—is generally not found in the Linear B (Mycenean Greek) texts, although there is a possible attestation in the lacunose form ]pe-rjo-[ (Linear B: ]-[) on the KN E 842 tablet, though it has also been suggested that the name might actually read "Hyperion" ([u]-pe-rjo-[ne]). The etymology of the name is uncertain. The spelling ( in Classical Attic) had almost superseded all other forms by the beginning of the common era, but the Doric form, Apellon (), is more archaic, as it is derived from an earlier . It probably is a cognate to the Doric month Apellaios (), and the offerings apellaia () at the initiation of the young men during the family-festival apellai (). According to some scholars, the words are derived from the Doric word apella (), which originally meant "wall," "fence for animals" and later "assembly within the limits of the square." Apella () is the name of the popular assembly in Sparta, corresponding to the ecclesia (). R. S. P. Beekes rejected the connection of the theonym with the noun apellai and suggested a Pre-Greek proto-form *Apalyun. Several instances of popular etymology are attested from ancient authors. Thus, the Greeks most often associated Apollo's name with the Greek verb (apollymi), "to destroy". Plato in Cratylus connects the name with (apolysis), "redemption", with (apolousis), "purification", and with ([h]aploun), "simple", in particular in reference to the Thessalian form of the name, , and finally with (aeiballon), "ever-shooting". Hesychius connects the name Apollo with the Doric (apella), which means "assembly", so that Apollo would be the god of political life, and he also gives the explanation (sekos), "fold", in which case Apollo would be the god of flocks and herds. In the ancient Macedonian language (pella) means "stone," and some toponyms may be derived from this word: (Pella, the capital of ancient Macedonia) and (Pellēnē/Pellene). A number of non-Greek etymologies have been suggested for the name, The Hittite form Apaliunas (d) is attested in the Manapa-Tarhunta letter. The Hittite testimony reflects an early form , which may also be surmised from comparison of Cypriot with Doric . The name of the Lydian god Qλdãns /kʷʎðãns/ may reflect an earlier /kʷalyán-/ before palatalization, syncope, and the pre-Lydian sound change *y > d. Note the labiovelar in place of the labial /p/ found in pre-Doric Ἀπέλjων and Hittite Apaliunas. A Luwian etymology suggested for Apaliunas makes Apollo "The One of Entrapment", perhaps in the sense of "Hunter". Greco-Roman epithets Apollo's chief epithet was Phoebus ( ; , Phoibos ), literally "bright". It was very commonly used by both the Greeks and Romans for Apollo's role as the god of light. Like other Greek deities, he had a number of others applied to him, reflecting the variety of roles, duties, and aspects ascribed to the god. However, while Apollo has a great number of appellations in Greek myth, only a few occur in Latin literature. Sun Aegletes ( ; Αἰγλήτης, Aiglētēs), from , "light of the sun" Helius ( ; , Helios), literally "sun" Lyceus ( ; , Lykeios, from Proto-Greek *), "light". The meaning of the epithet "Lyceus" later became associated with Apollo's mother Leto, who was the patron goddess of Lycia () and who was identified with the wolf (). Phanaeus ( ; , Phanaios), literally "giving or bringing light" Phoebus ( ; , Phoibos), literally "bright", his most commonly used epithet by both the Greeks and Romans Sol (Roman) (), "sun" in Latin Wolf Lycegenes ( ; , Lukēgenēs), literally "born of a wolf" or "born of Lycia" Lycoctonus ( ; , Lykoktonos), from , "wolf", and , "to kill" Origin and birth Apollo's birthplace was Mount Cynthus on the island of Delos. Cynthius ( ; , Kunthios), literally "Cynthian" Cynthogenes ( ; , Kynthogenēs), literally "born of Cynthus" Delius ( ; Δήλιος, Delios), literally "Delian" Didymaeus ( ; , Didymaios) from δίδυμος, "twin", as the twin of Artemis Place of worship Delphi and Actium were his primary places of worship. Acraephius ( ; , Akraiphios, literally "Acraephian") or Acraephiaeus ( ; , Akraiphiaios), "Acraephian", from the Boeotian town of Acraephia (), reputedly founded by his son Acraepheus. Actiacus ( ; , Aktiakos), literally "Actian", after Actium () Delphinius ( ; , Delphinios), literally "Delphic", after Delphi (Δελφοί). An etiology in the Homeric Hymns associated this with dolphins. Epactaeus, meaning "god worshipped on the coast", in Samos. Pythius ( ; , Puthios, from Πυθώ, Pythō), from the region around Delphi Smintheus ( ; , Smintheus), "Sminthian"—that is, "of the town of Sminthos or Sminthe" near the Troad town of Hamaxitus Napaian Apollo (Ἀπόλλων Ναπαῖος), from the city of Nape at the island of Lesbos Healing and disease Acesius ( ; , Akesios), from , "healing". Acesius was the epithet of Apollo worshipped in Elis, where he had a temple in the agora. Acestor ( ; , Akestōr), literally "healer" Culicarius (Roman) ( ), from Latin culicārius, "of midges" Iatrus ( ; , Iātros), literally "physician" Medicus (Roman) ( ), "physician" in Latin. A temple was dedicated to Apollo Medicus at Rome, probably next to the temple of Bellona. Paean ( ; , Paiān), physician, healer Parnopius ( ; , Parnopios), from , "locust" Founder and protector Agyieus ( ; , Aguīeus), from , "street", for his role in protecting roads and homes Alexicacus ( ; , Alexikakos), literally "warding off evil" Apotropaeus ( ; , Apotropaios), from , "to avert" Archegetes ( ; , Arkhēgetēs), literally "founder" Averruncus (Roman) ( ; from Latin āverruncare), "to avert" Clarius ( ; , Klārios), from Doric , "allotted lot" Epicurius ( ; , Epikourios), from , "to aid" Genetor ( ; , Genetōr), literally "ancestor" Nomius ( ; , Nomios), literally "pastoral" Nymphegetes ( ; , Numphēgetēs), from , "Nymph", and , "leader", for his role as a protector of shepherds and pastoral life Patroos from , "related to one's father," for his role as father of Ion and founder of the Ionians, as worshipped at the Temple of Apollo Patroos in Athens Sauroctunos, “lizard killer”, possibly a reference to his killing of Python Prophecy and truth Coelispex (Roman) ( ), from Latin coelum, "sky", and specere "to look at" Iatromantis ( ; , Iātromantis,) from , "physician", and , "prophet", referring to his role as a god both of healing and of prophecy Leschenorius ( ; , Leskhēnorios), from , "converser" Loxias ( ; , Loxias), from , "to say", historically associated with , "ambiguous" Manticus ( ; , Mantikos), literally "prophetic" Proopsios (), meaning "foreseer" or "first seen" Music and arts Musagetes ( ; Doric , Mousāgetās), from , "Muse", and "leader" Musegetes ( ; , Mousēgetēs), as the preceding Archery Aphetor ( ; , Aphētōr), from , "to let loose" Aphetorus ( ; , Aphētoros), as the preceding Arcitenens (Roman) ( ), literally "bow-carrying" Argyrotoxus ( ; , Argyrotoxos), literally "with silver bow" Clytotoxus ( ; , Klytótoxos), "he who is famous for his bow", the renowned archer. Hecaërgus ( ; , Hekaergos), literally "far-shooting" Hecebolus ( ; , Hekēbolos), "far-shooting" Ismenius ( ; , Ismēnios), literally "of Ismenus", after Ismenus, the son of Amphion and Niobe, whom he struck with an arrow Amazons Amazonius (), Pausanias at the Description of Greece writes that near Pyrrhichus there was a sanctuary of Apollo, called Amazonius () with image of the god said to have been dedicated by the Amazons. Celtic epithets and cult titles Apollo was worshipped throughout the Roman Empire. In the traditionally Celtic lands, he was most often seen as a healing and sun god. He was often equated with Celtic gods of similar character. Apollo Atepomarus ("the great horseman" or "possessing a great horse"). Apollo was worshipped at Mauvières (Indre). Horses were, in the Celtic world, closely linked to the sun. Apollo Belenus ("bright" or "brilliant"). This epithet was given to Apollo in parts of Gaul, Northern Italy and Noricum (part of modern Austria). Apollo Belenus was a healing and sun god. Apollo Cunomaglus ("hound lord"). A title given to Apollo at a shrine at Nettleton Shrub, Wiltshire. May have been a god of healing. Cunomaglus himself may originally have been an independent healing god. Apollo Grannus. Grannus was a healing spring god, later equated with Apollo. Apollo Maponus. A god known from inscriptions in Britain. This may be a local fusion of Apollo and Maponus. Apollo Moritasgus ("masses of sea water"). An epithet for Apollo at Alesia, where he was worshipped as god of healing and, possibly, of physicians. Apollo Vindonnus ("clear light"). Apollo Vindonnus had a temple at Essarois, near Châtillon-sur-Seine in present-day Burgundy. He was a god of healing, especially of the eyes. Apollo Virotutis ("benefactor of mankind"). Apollo Virotutis was worshipped, among other places, at Fins d'Annecy (Haute-Savoie) and at Jublains (Maine-et-Loire). Origins The cult centers of Apollo in Greece, Delphi and Delos, date from the 8th century BCE. The Delos sanctuary was primarily dedicated to Artemis, Apollo's twin sister. At Delphi, Apollo was venerated as the slayer of the monstrous serpent Python. For the Greeks, Apollo was the most Greek of all the gods, and through the centuries he acquired different functions. In Archaic Greece he was the prophet, the oracular god who in older times was connected with "healing". In Classical Greece he was the god of light and of music, but in popular religion he had a strong function to keep away evil. Walter Burkert discerned three components in the prehistory of Apollo worship, which he termed "a Dorian-northwest Greek component, a Cretan-Minoan component, and a Syro-Hittite component." Healer and god-protector from evil In classical times, his major function in popular religion was to keep away evil, and he was therefore called "apotropaios" (, "averting evil") and "alexikakos" ( "keeping off ill"; from v. + n. ). Apollo also had many epithets relating to his function as a healer. Some commonly-used examples are "paion" ( literally "healer" or "helper") "epikourios" (, "succouring"), "oulios" (, "healer, baleful") and "loimios" (, "of the plague"). In later writers, the word, "paion", usually spelled "Paean", becomes a mere epithet of Apollo in his capacity as a god of healing. Apollo in his aspect of "healer" has a connection to the primitive god Paean (), who did not have a cult of his own. Paean serves as the healer of the gods in the Iliad, and seems to have originated in a pre-Greek religion. It is suggested, though unconfirmed, that he is connected to the Mycenaean figure pa-ja-wo-ne (Linear B: ). Paean was the personification of holy songs sung by "seer-doctors" (), which were supposed to cure disease. Homer illustrated Paeon the god and the song both of apotropaic thanksgiving or triumph. Such songs were originally addressed to Apollo and afterwards to other gods: to Dionysus, to Apollo Helios, to Apollo's son Asclepius the healer. About the 4th century BCE, the paean became merely a formula of adulation; its object was either to implore protection against disease and misfortune or to offer thanks after such protection had been rendered. It was in this way that Apollo had become recognized as the god of music. Apollo's role as the slayer of the Python led to his association with battle and victory; hence it became the Roman custom for a paean to be sung by an army on the march and before entering into battle, when a fleet left the harbour, and also after a victory had been won. In the Iliad, Apollo is the healer under the gods, but he is also the bringer of disease and death with his arrows, similar to the function of the Vedic god of disease Rudra. He sends a plague () to the Achaeans. Knowing that Apollo can prevent a recurrence of the plague he sent, they purify themselves in a ritual and offer him a large sacrifice of cows, called a hecatomb. Dorian origin The Homeric Hymn to Apollo depicts Apollo as an intruder from the north. The connection with the northern-dwelling Dorians and their initiation festival apellai is reinforced by the month Apellaios in northwest Greek calendars. The family-festival was dedicated to Apollo (Doric: ). Apellaios is the month of these rites, and Apellon is the "megistos kouros" (the great Kouros). However it can explain only the Doric type of the name, which is connected with the Ancient Macedonian word "pella" (Pella), stone. Stones played an important part in the cult of the god, especially in the oracular shrine of Delphi (Omphalos). Minoan origin George Huxley regarded the identification of Apollo with the Minoan deity Paiawon, worshipped in Crete, to have originated at Delphi. In the Homeric Hymn, Apollo appeared as a dolphin and carried Cretan priests to Delphi, where they evidently transferred their religious practices. Apollo Delphinios or Delphidios was a sea-god especially worshipped in Crete and in the islands. Apollo's sister Artemis, who was the Greek goddess of hunting, is identified with Britomartis (Diktynna), the Minoan "Mistress of the animals". In her earliest depictions she was accompanied by the "Master of the animals", a bow-wielding god of hunting whose name has been lost; aspects of this figure may have been absorbed into the more popular Apollo. Anatolian origin A non-Greek origin of Apollo has long been assumed in scholarship. The name of Apollo's mother Leto has Lydian origin, and she was worshipped on the coasts of Asia Minor. The inspiration oracular cult was probably introduced into Greece from Anatolia, which is the origin of Sibyl, and where some of the oldest oracular shrines originated. Omens, symbols, purifications, and exorcisms appear in old Assyro-Babylonian texts. These rituals were spread into the empire of the Hittites, and from there into Greece. Homer pictures Apollo on the side of the Trojans, fighting against the Achaeans, during the Trojan War. He is pictured as a terrible god, less trusted by the Greeks than other gods. The god seems to be related to Appaliunas, a tutelary god of Wilusa (Troy) in Asia Minor, but the word is not complete. The stones found in front of the gates of Homeric Troy were the symbols of Apollo. A western Anatolian origin may also be bolstered by references to the parallel worship of Artimus (Artemis) and Qλdãns, whose name may be cognate with the Hittite and Doric forms, in surviving Lydian texts. However, recent scholars have cast doubt on the identification of Qλdãns with Apollo. The Greeks gave to him the name agyieus as the protector god of public places and houses who wards off evil and his symbol was a tapered stone or column. However, while usually Greek festivals were celebrated at the full moon, all the feasts of Apollo were celebrated at the seventh day of the month, and the emphasis given to that day (sibutu) indicates a Babylonian origin. The Late Bronze Age (from 1700 to 1200 BCE) Hittite and Hurrian Aplu was a god of plague, invoked during plague years. Here we have an apotropaic situation, where a god originally bringing the plague was invoked to end it. Aplu, meaning the son of, was a title given to the god Nergal, who was linked to the Babylonian god of the sun Shamash. Homer interprets Apollo as a terrible god () who brings death and disease with his arrows, but who can also heal, possessing a magic art that separates him from the other Greek gods. In Iliad, his priest prays to Apollo Smintheus, the mouse god who retains an older agricultural function as the protector from field rats. All these functions, including the function of the healer-god Paean, who seems to have Mycenean origin, are fused in the cult of Apollo. Proto-Indo-European The Vedic Rudra has some similar functions with Apollo. The terrible god is called "the archer" and the bow is also an attribute of Shiva. Rudra could bring diseases with his arrows, but he was able to free people of them and his alternative Shiva is a healer physician god. However the Indo-European component of Apollo does not explain his strong relation with omens, exorcisms, and with the oracular cult. Oracular cult Unusually among the Olympic deities, Apollo had two cult sites that had widespread influence: Delos and Delphi. In cult practice, Delian Apollo and Pythian Apollo (the Apollo of Delphi) were so distinct that they might both have shrines in the same locality. Lycia was sacred to the god, for this Apollo was also called Lycian. Apollo's cult was already fully established when written sources commenced, about 650 BCE. Apollo became extremely important to the Greek world as an oracular deity in the archaic period, and the frequency of theophoric names such as Apollodorus or Apollonios and cities named Apollonia testify to his popularity. Oracular sanctuaries to Apollo were established in other sites. In the 2nd and 3rd century CE, those at Didyma and Claros pronounced the so-called "theological oracles", in which Apollo confirms that all deities are aspects or servants of an all-encompassing, highest deity. "In the 3rd century, Apollo fell silent. Julian the Apostate (359–361) tried to revive the Delphic oracle, but failed." Oracular shrines Apollo had a famous oracle in Delphi, and other notable ones in Claros and Didyma. His oracular shrine in Abae in Phocis, where he bore the toponymic epithet Abaeus (, Apollon Abaios), was important enough to be consulted by Croesus. His oracular shrines include: Abae in Phocis. Bassae in the Peloponnese. At Clarus, on the west coast of Asia Minor; as at Delphi a holy spring which gave off a pneuma, from which the priests drank. In Corinth, the Oracle of Corinth came from the town of Tenea, from prisoners supposedly taken in the Trojan War. At Khyrse, in Troad, the temple was built for Apollo Smintheus. In Delos, there was an oracle to the Delian Apollo, during summer. The Hieron (Sanctuary) of Apollo adjacent to the Sacred Lake, was the place where the god was said to have been born. In Delphi, the Pythia became filled with the pneuma of Apollo, said to come from a spring inside the Adyton. In Didyma, an oracle on the coast of Anatolia, south west of Lydian (Luwian) Sardis, in which priests from the lineage of the Branchidae received inspiration by drinking from a healing spring located in the temple. Was believed to have been founded by Branchus, son or lover of Apollo. In Hierapolis Bambyce, Syria (modern Manbij), according to the treatise De Dea Syria, the sanctuary of the Syrian Goddess contained a robed and bearded image of Apollo. Divination was based on spontaneous movements of this image. At Patara, in Lycia, there was a seasonal winter oracle of Apollo, said to have been the place where the god went from Delos. As at Delphi the oracle at Patara was a woman. In Segesta in Sicily. Oracles were also given by sons of Apollo. In Oropus, north of Athens, the oracle Amphiaraus, was said to be the son of Apollo; Oropus also had a sacred spring. in Labadea, east of Delphi, Trophonius, another son of Apollo, killed his brother and fled to the cave where he was also afterwards consulted as an oracle. Temples of Apollo Many temples were dedicated to Apollo in Greece and the Greek colonies. They show the spread of the cult of Apollo and the evolution of the Greek architecture, which was mostly based on the rightness of form and on mathematical relations. Some of the earliest temples, especially in Crete, do not belong to any Greek order. It seems that the first peripteral temples were rectangular wooden structures. The different wooden elements were considered divine, and their forms were preserved in the marble or stone elements of the temples of Doric order. The Greeks used standard types because they believed that the world of objects was a series of typical forms which could be represented in several instances. The temples should be canonic, and the architects were trying to achieve this esthetic perfection. From the earliest times there were certain rules strictly observed in rectangular peripteral and prostyle buildings. The first buildings were built narrowly in order to hold the roof, and when the dimensions changed some mathematical relations became necessary in order to keep the original forms. This probably influenced the theory of numbers of Pythagoras, who believed that behind the appearance of things there was the permanent principle of mathematics. The Doric order dominated during the 6th and the 5th century BC but there was a mathematical problem regarding the position of the triglyphs, which couldn't be solved without changing the original forms. The order was almost abandoned for the Ionic order, but the Ionic capital also posed an insoluble problem at the corner of a temple. Both orders were abandoned for the Corinthian order gradually during the Hellenistic age and under Rome. The most important temples are: Greek temples Thebes, Greece: The oldest temple probably dedicated to Apollo Ismenius was built in the 9th century B.C. It seems that it was a curvilinear building. The Doric temple was built in the early 7th century B.C., but only some small parts have been found A festival called Daphnephoria was celebrated every ninth year in honour of Apollo Ismenius (or Galaxius). The people held laurel branches (daphnai), and at the head of the procession walked a youth (chosen priest of Apollo), who was called "daphnephoros". Eretria: According to the Homeric hymn to Apollo, the god arrived to the plain, seeking for a location to establish its oracle. The first temple of Apollo Daphnephoros, "Apollo, laurel-bearer", or "carrying off Daphne", is dated to 800 B.C. The temple was curvilinear hecatombedon (a hundred feet). In a smaller building were kept the bases of the laurel branches which were used for the first building. Another temple probably peripteral was built in the 7th century B.C., with an inner row of wooden columns over its Geometric predecessor. It was rebuilt peripteral around 510 B.C., with the stylobate measuring 21,00 x 43,00 m. The number of pteron column was 6 x 14. Dreros (Crete). The temple of Apollo Delphinios dates from the 7th century B.C., or probably from the middle of the 8th century B.C. According to the legend, Apollo appeared as a dolphin, and carried Cretan priests to the port of Delphi. The dimensions of the plan are 10,70 x 24,00 m and the building was not peripteral. It contains column-bases of the Minoan type, which may be considered as the predecessors of the Doric columns. Gortyn (Crete). A temple of Pythian Apollo, was built in the 7th century B.C. The plan measured 19,00 x 16,70 m and it was not peripteral. The walls were solid, made from limestone, and there was single door on the east side. Thermon (West Greece): The Doric temple of Apollo Thermios, was built in the middle of the 7th century B.C. It was built on an older curvilinear building dating perhaps from the 10th century B.C., on which a peristyle was added. The temple was narrow, and the number of pteron columns (probably wooden) was 5 x 15. There was a single row of inner columns. It measures 12.13 x 38.23 m at the stylobate, which was made from stones. Corinth: A Doric temple was built in the 6th century B.C. The temple's stylobate measures 21.36 x 53.30 m, and the number of pteron columns was 6 x 15. There was a double row of inner columns. The style is similar with the Temple of Alcmeonidae at Delphi. The Corinthians were considered to be the inventors of the Doric order. Napes (Lesbos): An Aeolic temple probably of Apollo Napaios was built in the 7th century B.C. Some special capitals with floral ornament have been found, which are called Aeolic, and it seems that they were borrowed from the East. Cyrene, Libya: The oldest Doric temple of Apollo was built in c. 600 B.C. The number of pteron columns was 6 x 11, and it measures 16.75 x 30.05 m at the stylobate. There was a double row of sixteen inner columns on stylobates. The capitals were made from stone. Naukratis: An Ionic temple was built in the early 6th century B.C. Only some fragments have been found and the earlier, made from limestone, are identified among the oldest of the Ionic order. Syracuse, Sicily: A Doric temple was built at the beginning of the 6th century B.C. The temple's stylobate measures 21.47 x 55.36 m and the number of pteron columns was 6 x 17. It was the first temple in Greek west built completely out of stone. A second row of columns were added, obtaining the effect of an inner porch. Selinus (Sicily):The Doric Temple C dates from 550 B.C., and it was probably dedicated to Apollo. The temple's stylobate measures 10.48 x 41.63 m and the number of pteron columns was 6 x 17. There was portico with a second row of columns, which is also attested for the temple at Syracuse. Delphi: The first temple dedicated to Apollo, was built in the 7th century B.C. According to the legend, it was wooden made of laurel branches. The "Temple of Alcmeonidae" was built in c. 513 B.C. and it is the oldest Doric temple with significant marble elements. The temple's stylobate measures 21.65 x 58.00 m, and the number of pteron columns as 6 x 15. A fest similar with Apollo's fest at Thebes, Greece was celebrated every nine years. A boy was sent to the temple, who walked on the sacred road and returned carrying a laurel branch (dopnephoros). The maidens participated with joyful songs. Chios: An Ionic temple of Apollo Phanaios was built at the end of the 6th century B.C. Only some small parts have been found and the capitals had floral ornament. Abae (Phocis). The temple was destroyed by the Persians in the invasion of Xerxes in 480 B.C., and later by the Boeotians. It was rebuilt by Hadrian. The oracle was in use from early Mycenaean times to the Roman period, and shows the continuity of Mycenaean and Classical Greek religion. Bassae (Peloponnesus):A temple dedicated to Apollo Epikourios ("Apollo the helper"), was built in 430 B.C. and it was designed by Iktinos.It combined Doric and Ionic elements, and the earliest use of column with a Corinthian capital in the middle. The temple is of a relatively modest size, with the stylobate measuring 14.5 x 38.3 metres containing a Doric peristyle of 6 x 15 columns. The roof left a central space open to admit light and air. Delos: A temple probably dedicated to Apollo and not peripteral, was built in the late 7th century B.C., with a plan measuring 10,00 x 15,60 m. The Doric Great temple of Apollo, was built in c. 475 B.C. The temple's stylobate measures 13.72 x 29.78 m, and the number of pteron columns as 6 x 13. Marble was extensively used. Ambracia: A Doric peripteral temple dedicated to Apollo Pythios Sotir was built in 500 B.C., and It is lying at the centre of the Greek city Arta. Only some parts have been found, and it seems that the temple was built on earlier sanctuaries dedicated to Apollo. The temple measures 20,75 x 44,00 m at the stylobate. The foundation which supported the statue of the god, still exists. Didyma (near Miletus): The gigantic Ionic temple of Apollo Didymaios started around 540 B.C. The construction ceased and then it was restarted in 330 B.C. The temple is dipteral, with an outer row of 10 x 21 columns, and it measures 28.90 x 80.75 m at the stylobate. Clarus (near ancient Colophon): According to the legend, the famous seer Calchas, on his return from Troy, came to Clarus. He challenged the seer Mopsus, and died when he lost. The Doric temple of Apollo Clarius was probably built in the 3rd century B.C., and it was peripteral with 6 x 11 columns. It was reconstructed at the end of the Hellenistic period, and later from the emperor Hadrian but Pausanias claims that it was still incomplete in the 2nd century B.C. Hamaxitus (Troad): In Iliad, Chryses the priest of Apollo, addresses the god with the epithet Smintheus (Lord of Mice), related with the god's ancient role as bringer of the disease (plague). Recent excavations indicate that the Hellenistic temple of Apollo Smintheus was constructed at 150–125 B.C., but the symbol of the mouse god was used on coinage probably from the 4th century B.C. The temple measures 40,00 x 23,00 m at the stylobate, and the number of pteron columns was 8 x 14. Pythion (), this was the name of a shrine of Apollo at Athens near the Ilisos river. It was created by Peisistratos, and tripods placed there by those who had won in the cyclic chorus at the Thargelia. Setae (Lydia): The temple of Apollo Aksyros located in the city. Apollonia Pontica: There were two temples of Apollo Healer in the city. One from the Late Archaic period and the other from the Early Classical period. Ikaros island in the Persian Gulf (modern Failaka Island): There was a temple of Apollo on the island. Etruscan and Roman temples Veii (Etruria): The temple of Apollo was built in the late 6th century B.C. and it indicates the spread of Apollo's culture (Aplu) in Etruria. There was a prostyle porch, which is called Tuscan, and a triple cella 18,50 m wide. Falerii Veteres (Etruria): A temple of Apollo was built probably in the 4th-3rd century B.C. Parts of a teraccotta capital, and a teraccotta base have been found. It seems that the Etruscan columns were derived from the archaic Doric. A cult of Apollo Soranus is attested by one inscription found near Falerii. Pompeii (Italy): The cult of Apollo was widespread in the region of Campania since the 6th century B.C. The temple was built in 120 B.V, but its beginnings lie in the 6th century B.C. It was reconstructed after an earthquake in A.D. 63. It demonstrates a mixing of styles which formed the basis of Roman architecture. The columns in front of the cella formed a Tuscan prostyle porch, and the cella is situated unusually far back. The peripteral colonnade of 48 Ionic columns was placed in such a way that the emphasis was given to the front side. Rome: The temple of Apollo Sosianus and the temple of Apollo Medicus. The first temple building dates to 431 B.C., and was dedicated to Apollo Medicus (the doctor), after a plague of 433 B.C. It was rebuilt by Gaius Sosius, probably in 34 B.C. Only three columns with Corinthian capitals exist today. It seems that the cult of Apollo had existed in this area since at least to the mid-5th century B.C. Rome:The temple of Apollo Palatinus was located on the Palatine hill within the sacred boundary of the city. It was dedicated by Augustus on 28 B.C. The façade of the original temple was Ionic and it was constructed from solid blocks of marble. Many famous statues by Greek masters were on display in and around the temple, including a marble statue of the god at the entrance and a statue of Apollo in the cella. Melite (modern Mdina, Malta): A Temple of Apollo was built in the city in the 2nd century A.D. Its remains were discovered in the 18th century, and many of its architectural fragments were dispersed among private collections or reworked into new sculptures. Parts of the temple's podium were rediscovered in 2002. Mythology Apollo appears often in the myths, plays and hymns. As Zeus' favorite son, Apollo had direct access to the mind of Zeus and was willing to reveal this knowledge to humans. A divinity beyond human comprehension, he appears both as a beneficial and a wrathful god. Birth Apollo was the son of Zeus, the king of the gods, and Leto, his previous wife or one of his mistresses. Growing up, Apollo was nursed by the nymphs Korythalia and Aletheia, the personification of truth. When Zeus' wife Hera discovered that Leto was pregnant, she banned Leto from giving birth on terra firma. Leto sought shelter in many lands, only to be rejected by them. Finally, the voice of unborn Apollo informed his mother about a floating island named Delos that had once been Asteria, Leto's own sister. Since it was neither a mainland nor an island, Leto was readily welcomed there and gave birth to her children under a palm tree. All the goddesses except Hera were present to witness the event. It is also stated that Hera kidnapped Eileithyia, the goddess of childbirth, to prevent Leto from going into labor. The other gods tricked Hera into letting her go by offering her a necklace of amber 9 yards (8.2 m) long. When Apollo was born, clutching a golden sword, everything on Delos turned into gold and the island was filled with ambrosial fragrance. Swans circled the island seven times and the nymphs sang in delight. He was washed clean by the goddesses who then covered him in white garment and fastened golden bands around him. Since Leto was unable to feed him, Themis, the goddess of divine law, fed him with nectar, or ambrosia. Upon tasting the divine food, Apollo broke free of the bands fastened onto him and declared that he would be the master of lyre and archery, and interpret the will of Zeus to humankind. Zeus, who had calmed Hera by then, came and adorned his son with a golden headband. Apollo's birth fixed the floating Delos to the earth. Leto promised that her son would be always favorable towards the Delians. According to some, Apollo secured Delos to the bottom of the ocean after some time. This island became sacred to Apollo and was one of the major cult centres of the god. Apollo was born on the seventh day (, hebdomagenes) of the month Thargelion—according to Delian tradition—or of the month Bysios—according to Delphian tradition. The seventh and twentieth, the days of the new and full moon, were ever afterwards held sacred to him. Mythographers agree that Artemis was born first and subsequently assisted with the birth of Apollo or was born on the island of Ortygia then helped Leto cross the sea to Delos the next day to give birth to Apollo. Hyperborea Hyperborea, the mystical land of eternal spring, venerated Apollo above all the gods. The Hyperboreans always sang and danced in his honor and hosted Pythian games. There, a vast forest of beautiful trees was called "the garden of Apollo". Apollo spent the winter months among the Hyperboreans. His absence from the world caused coldness and this was marked as his annual death. No prophecies were issued during this time. He returned to the world during the beginning of the spring. The Theophania festival was held in Delphi to celebrate his return. It is said that Leto came to Delos from Hyperborea accompanied by a pack of wolves. Henceforth, Hyperborea became Apollo's winter home and wolves became sacred to him. His intimate connection to wolves is evident from his epithet Lyceus, meaning wolf-like. But Apollo was also the wolf-slayer in his role as the god who protected flocks from predators. The Hyperborean worship of Apollo bears the strongest marks of Apollo being worshipped as the sun god. Shamanistic elements in Apollo's cult are often liked to his Hyperborean origin, and he is likewise speculated to have originated as a solar shaman. Shamans like Abaris and Aristeas were also the followers of Apollo, who hailed from Hyperborea. In myths, the tears of amber Apollo shed when his son Asclepius died became the waters of the river Eridanos, which surrounded Hyperborea. Apollo also buried in Hyperborea the arrow which he had used to kill the Cyclopes. He later gave this arrow to Abaris. Childhood and youth As a child, Apollo is said to have built a foundation and an altar on Delos using the horns of the goats that his sister Artemis hunted. Since he learnt the art of building when young, he later came to be known as Archegetes, the founder (of towns) and god who guided men to build new cities. From his father Zeus, Apollo had also received a golden chariot drawn by swans. In his early years when Apollo spent his time herding cows, he was reared by Thriae, the bee nymphs, who trained him and enhanced his prophetic skills. Apollo is also said to have invented the lyre, and along with Artemis, the art of archery. He then taught to the humans the art of healing and archery. Phoebe, his grandmother, gave the oracular shrine of Delphi to Apollo as a birthday gift. Themis inspired him to be the oracular voice of Delphi thereon. Python Python, a chthonic serpent-dragon, was a child of Gaia and the guardian of the Delphic Oracle, whose death was foretold by Apollo when he was still in Leto's womb. Python was the nurse of the giant Typhon. In most of the traditions, Apollo was still a child when he killed Python. Python was sent by Hera to hunt the pregnant Leto to death, and had assaulted her. To avenge the trouble given to his mother, Apollo went in search of Python and killed it in the sacred cave at Delphi with the bow and arrows that he had received from Hephaestus. The Delphian nymphs who were present encouraged Apollo during the battle with the cry "Hie Paean". After Apollo was victorious, they also brought him gifts and gave the Corycian cave to him. According to Homer, Apollo had encountered and killed the Python when he was looking for a place to establish his shrine. According to another version, when Leto was in Delphi, Python had attacked her. Apollo defended his mother and killed Python. Euripides in his Iphigenia in Aulis gives an account of his fight with Python and the event's aftermath. You killed him, o Phoebus, while still a baby, still leaping in the arms of your dear mother, and you entered the holy shrine, and sat on the golden tripod, on your truthful throne distributing prophecies from the gods to mortals. A detailed account of Apollo's conflict with Gaia and Zeus' intervention on behalf of his young son is also given. But when Apollo came and sent Themis, the child of Earth, away from the holy oracle of Pytho, Earth gave birth to dream visions of the night; and they told to the cities of men the present, and what will happen in the future, through dark beds of sleep on the ground; and so Earth took the office of prophecy away from Phoebus, in envy, because of her daughter. The lord made his swift way to Olympus and wound his baby hands around Zeus, asking him to take the wrath of the earth goddess from the Pythian home. Zeus smiled, that the child so quickly came to ask for worship that pays in gold. He shook his locks of hair, put an end to the night voices, and took away from mortals the truth that appears in darkness, and gave the privilege back again to Loxias. Apollo also demanded that all other methods of divination be made inferior to his, a wish that Zeus granted him readily. Because of this, Athena, who had been practicing divination by throwing pebbles, cast her pebbles away in displeasure. However, Apollo had committed a blood murder and had to be purified. Because Python was a child of Gaia, Gaia wanted Apollo to be banished to Tartarus as a punishment. Zeus didn't agree and instead exiled his son from Olympus, and instructed him to get purified. Apollo had to serve as a slave for nine years. After the servitude was over, as per his father's order, he travelled to the Vale of Tempe to bath in waters of Peneus. There Zeus himself performed purificatory rites on Apollo. Purified, Apollo was escorted by his half sister Athena to Delphi where the oracular shrine was finally handed over to him by Gaia. According to a variation, Apollo had also travelled to Crete, where Carmanor purified him. Apollo later established the Pythian games to appropriate Gaia. Henceforth, Apollo became the god who cleansed himself from the sin of murder and, made men aware of their guilt and purified them. Soon after, Zeus instructed Apollo to go to Delphi and establish his law. But Apollo, disobeying his father, went to the land of Hyperborea and stayed there for a year. He returned only after the Delphians sang hymns to him and pleaded him to come back. Zeus, pleased with his son's integrity, gave Apollo the seat next to him on his right side. He also gave to Apollo various gifts, like a golden tripod, a golden bow and arrows, a golden chariot and the city of Delphi. Soon after his return, Apollo needed to recruit people to Delphi. So, when he spotted a ship sailing from Crete, he sprang aboard in the form of a dolphin. The crew was awed into submission and followed a course that led the ship to Delphi. There Apollo revealed himself as a god. Initiating them to his service, he instructed them to keep righteousness in their hearts. The Pythia was Apollo's high priestess and his mouthpiece through whom he gave prophecies. Pythia is arguably the constant favorite of Apollo among the mortals. Tityos Hera once again sent another giant, Tityos to rape Leto. This time Apollo shot him with his arrows and attacked him with his golden sword. According to other version, Artemis also aided him in protecting their mother by attacking Tityos with her arrows. After the battle Zeus finally relented his aid and hurled Tityos down to Tartarus. There, he was pegged to the rock floor, covering an area of , where a pair of vultures feasted daily on his liver. Admetus Admetus was the king of Pherae, who was known for his hospitality. When Apollo was exiled from Olympus for killing Python, he served as a herdsman under Admetus, who was then young and unmarried. Apollo is said to have shared a romantic relationship with Admetus during his stay. After completing his years of servitude, Apollo went back to Olympus as a god. Because Admetus had treated Apollo well, the god conferred great benefits on him in return. Apollo's mere presence is said to have made the cattle give birth to twins. Apollo helped Admetus win the hand of Alcestis, the daughter of King Pelias, by taming a lion and a boar to draw Admetus' chariot. He was present during their wedding to give his blessings. When Admetus angered the goddess Artemis by forgetting to give her the due offerings, Apollo came to the rescue and calmed his sister. When Apollo learnt of Admetus' untimely death, he convinced or tricked the Fates into letting Admetus live past his time. According to another version, or perhaps some years later, when Zeus struck down Apollo's son Asclepius with a lightning bolt for resurrecting the dead, Apollo in revenge killed the Cyclopes, who had fashioned the bolt for Zeus. Apollo would have been banished to Tartarus for this, but his mother Leto intervened, and reminding Zeus of their old love, pleaded him not to kill their son. Zeus obliged and sentenced Apollo to one year of hard labor once again under Admetus. The love between Apollo and Admetus was a favored topic of Roman poets like Ovid and Servius. Niobe The fate of Niobe was prophesied by Apollo while he was still in Leto's womb. Niobe was the queen of Thebes and wife of Amphion. She displayed hubris when she boasted that she was superior to Leto because she had fourteen children (Niobids), seven male and seven female, while Leto had only two. She further mocked Apollo's effeminate appearance and Artemis' manly appearance. Leto, insulted by this, told her children to punish Niobe. Accordingly, Apollo killed Niobe's sons, and Artemis her daughters. According to some versions of the myth, among the Niobids, Chloris and her brother Amyclas were not killed because they prayed to Leto. Amphion, at the sight of his dead sons, either killed himself or was killed by Apollo after swearing revenge. A devastated Niobe fled to Mount Sipylos in Asia Minor and turned into stone as she wept. Her tears formed the river Achelous. Zeus had turned all the people of Thebes to stone and so no one buried the Niobids until the ninth day after their death, when the gods themselves entombed them. When Chloris married and had children, Apollo granted her son Nestor the years he had taken away from the Niobids. Hence, Nestor was able to live for 3 generations. Building the walls of Troy Once Apollo and Poseidon served under the Trojan king Laomedon in accordance to Zeus' words. Apollodorus states that the gods willingly went to the king disguised as humans in order to check his hubris. Apollo guarded the cattle of Laomedon in the valleys of mount Ida, while Poseidon built the walls of Troy. Other versions make both Apollo and Poseidon the builders of the wall. In Ovid's account, Apollo completes his task by playing his tunes on his lyre. In Pindar's odes, the gods took a mortal named Aeacus as their assistant. When the work was completed, three snakes rushed against the wall, and though the two that attacked the sections of the wall built by the gods fell down dead, the third forced its way into the city through the portion of the wall built by Aeacus. Apollo immediately prophesied that Troy would fall at the hands of Aeacus's descendants, the Aeacidae (i.e. his son Telamon joined Heracles when he sieged the city during Laomedon's rule. Later, his great grandson Neoptolemus was present in the wooden horse that lead to the downfall of Troy). However, the king not only refused to give the gods the wages he had promised, but also threatened to bind their feet and hands, and sell them as slaves. Angered by the unpaid labour and the insults, Apollo infected the city with a pestilence and Posedion sent the sea monster Cetus. To deliver the city from it, Laomedon had to sacrifice his daughter Hesione (who would later be saved by Heracles). During his stay in Troy, Apollo had a lover named Ourea, who was a nymph and daughter of Poseidon. Together they had a son named Ileus, whom Apollo loved dearly. Trojan War Apollo sided with the Trojans during the Trojan War waged by the Greeks against the Trojans. During the war, the Greek king Agamemnon captured Chryseis, the daughter of Apollo's priest Chryses, and refused to return her. Angered by this, Apollo shot arrows infected with the plague into the Greek encampment. He demanded that they return the girl, and the Achaeans (Greeks) complied, indirectly causing the anger of Achilles, which is the theme of the Iliad. Receiving the aegis from Zeus, Apollo entered the battlefield as per his father's command, causing great terror to the enemy with his war cry. He pushed the Greeks back and destroyed many of the soldiers. He is described as "the rouser of armies" because he rallied the Trojan army when they were falling apart. When Zeus allowed the other gods to get involved in the war, Apollo was provoked by Poseidon to a duel. However, Apollo declined to fight him, saying that he wouldn't fight his uncle for the sake of mortals. When the Greek hero Diomedes injured the Trojan hero Aeneas, Aphrodite tried to rescue him, but Diomedes injured her as well. Apollo then enveloped Aeneas in a cloud to protect him. He repelled the attacks Diomedes made on him and gave the hero a stern warning to abstain himself from attacking a god. Aeneas was then taken to Pergamos, a sacred spot in Troy, where he was healed. After the death of Sarpedon, a son of Zeus, Apollo rescued the corpse from the battlefield as per his father's wish and cleaned it. He then gave it to Sleep (Hypnos) and Death (Thanatos). Apollo had also once convinced Athena to stop the war for that day, so that the warriors can relieve themselves for a while. The Trojan hero Hector (who, according to some, was the god's own son by Hecuba) was favored by Apollo. When he got severely injured, Apollo healed him and encouraged him to take up his arms. During a duel with Achilles, when Hector was about to lose, Apollo hid Hector in a cloud of mist to save him. When the Greek warrior Patroclus tried to get into the fort of Troy, he was stopped by Apollo. Encouraging Hector to attack Patroclus, Apollo stripped the armour of the Greek warrior and broke his weapons. Patroclus was eventually killed by Hector. At last, after Hector's fated death, Apollo protected his corpse from Achilles' attempt to mutilate it by creating a magical cloud over the corpse. Apollo held a grudge against Achilles throughout the war because Achilles had murdered his son Tenes before the war began and brutally assassinated his son Troilus in his own temple. Not only did Apollo save Hector from Achilles, he also tricked Achilles by disguising himself as a Trojan warrior and driving him away from the gates. He foiled Achilles' attempt to mutilate Hector's dead body. Finally, Apollo caused Achilles' death by guiding an arrow shot by Paris into Achilles' heel. In some versions, Apollo himself killed Achilles by taking the disguise of Paris. Apollo helped many Trojan warriors, including Agenor, Polydamas, Glaucus in the battlefield. Though he greatly favored the Trojans, Apollo was bound to follow the orders of Zeus and served his father loyally during the war. Heracles After Heracles (then named Alcides) was struck with madness and killed his family, he sought to purify himself and consulted the oracle of Apollo. Apollo, through the Pythia, commanded him to serve king Eurystheus for twelve years and complete the ten tasks the king would give him. Only then would Alcides be absolved of his sin. Apollo also renamed him as Heracles. To complete his third task, Heracles had to capture the Ceryneian Hind, a hind sacred to Artemis, and bring back it alive. After chasing the hind for one year, the animal eventually got tired, and when it tried crossing the river Ladon, Heracles captured it. While he was taking it back, he was confronted by Apollo and Artemis, who were angered at Heracles for this act. However, Heracles soothed the goddess and explained his situation to her. After much pleading, Artemis permitted him to take the hind and told him to return it later. After he was freed from his servitude to Eurystheus, Heracles fell in conflict with Iphytus, a prince of Oechalia, and murdered him. Soon after, he contracted a terrible disease. He consulted the oracle of Apollo once again, in hope of ridding himself of the disease. The Pythia, however, denied to give any prophesy. In anger, Heracles snatched the sacred tripod and started walking away, intending to start his own oracle. However, Apollo did not tolerate this and stopped Heracles; a duel ensued between them. Artemis rushed to support Apollo, while Athena supported Heracles. Soon, Zeus threw his thunderbolt between the fighting brothers and separated them. He reprimanded Heracles for this act of violation and asked Apollo to give a solution to Heracles. Apollo then ordered the hero to serve under Omphale, queen of Lydia for one year in order to purify himself. Periphas Periphas was an Attican king and a priest of Apollo. He was noble, just and rich. He did all his duties justly. Because of this people were very fond of him and started honouring him to the same extent as Zeus. At one point, they worshipped Periphas in place of Zeus and set up shrines and temples for him. This annoyed Zeus, who decided to annihilate the entire family of Periphas. But because he was a just king and a good devotee, Apollo intervened and requested his father to spare Periphas. Zeus considered Apollo's words and agreed to let him live. But he metamorphosed Periphas into an eagle and made the eagle the king of birds. When Periphas' wife requested Zeus to let her stay with her husband, Zeus turned her into a vulture and fulfilled her wish. Plato's concept of soulmates A long time ago, there were three kinds of human beings: male, descended from the sun; female, descended from the earth; and androgynous, descended from the moon. Each human being was completely round, with four arms and fours legs, two identical faces on opposite sides of a head with four ears, and all else to match. They were powerful and unruly. Otis and Ephialtes even dared to scale Mount Olympus. To check their insolence, Zeus devised a plan to humble them and improve their manners instead of completely destroying them. He cut them all in two and asked Apollo to make necessary repairs, giving humans the individual shape they still have now. Apollo turned their heads and necks around towards their wounds, he pulled together their skin at the abdomen, and sewed the skin together at the middle of it. This is what we call navel today. He smoothened the wrinkles and shaped the chest. But he made sure to leave a few wrinkles on the abdomen and around the navel so that they might be reminded of their punishment. "As he [Zeus] cut them one after another, he bade Apollo give the face and the half of the neck a turn... Apollo was also bidden to heal their wounds and compose their forms. So Apollo gave a turn to the face and pulled the skin from the sides all over that which in our language is called the belly, like the purses which draw in, and he made one mouth at the centre [of the belly] which he fastened in a knot (the same which is called the navel); he also moulded the breast and took out most of the wrinkles, much as a shoemaker might smooth leather upon a last; he left a few wrinkles, however, in the region of the belly and navel, as a memorial of the primeval state. Nurturer of the young Apollo Kourotrophos is the god who nurtures and protects children and the young, especially boys. He oversees their education and their passage into adulthood. Education is said to have originated from Apollo and the Muses. Many myths have him train his children. It was a custom for boys to cut and dedicate their long hair to Apollo after reaching adulthood. Chiron, the abandoned centaur, was fostered by Apollo, who instructed him in medicine, prophecy, archery and more. Chiron would later become a great teacher himself. Asclepius in his childhood gained much knowledge pertaining to medicinal arts by his father. However, he was later entrusted to Chiron for further education. Anius, Apollo's son by Rhoeo, was abandoned by his mother soon after his birth. Apollo brought him up and educated him in mantic arts. Anius later became the priest of Apollo and the king of Delos. Iamus was the son of Apollo and Evadne. When Evadne went into labour, Apollo sent the Moirai to assist his lover. After the child was born, Apollo sent snakes to feed the child some honey. When Iamus reached the age of education, Apollo took him to Olympia and taught him many arts, including the ability to understand and explain the languages of birds. Idmon was educated by Apollo to be a seer. Even though he foresaw his death that would happen in his journey with the Argonauts, he embraced his destiny and died a brave death. To commemorate his son's bravery, Apollo commanded Boeotians to build a town around the tomb of the hero, and to honor him. Apollo adopted Carnus, the abandoned son of Zeus and Europa. He reared the child with the help of his mother Leto and educated him to be a seer. When his son Melaneus reached the age of marriage, Apollo asked the princess Stratonice to be his son's bride and carried her away from her home when she agreed. Apollo saved a shepherd boy (name unknown) from death in a large deep cave, by the means of vultures. To thank him, the shepherd built Apollo a temple under the name Vulturius. God of music Immediately after his birth, Apollo demanded a lyre and invented the paean, thus becoming the god of music. As the divine singer, he is the patron of poets, singers and musicians. The invention of string music is attributed to him. Plato said that the innate ability of humans to take delight in music, rhythm and harmony is the gift of Apollo and the Muses. According to Socrates, ancient Greeks believed that Apollo is the god who directs the harmony and makes all things move together, both for the gods and the humans. For this reason, he was called Homopolon before the Homo was replaced by A. Apollo's harmonious music delivered people from their pain, and hence, like Dionysus, he is also called the liberator. The swans, which were considered to be the most musical among the birds, were believed to be the "singers of Apollo". They are Apollo's sacred birds and acted as his vehicle during his travel to Hyperborea. Aelian says that when the singers would sing hymns to Apollo, the swans would join the chant in unison. Among the Pythagoreans, the study of mathematics and music were connected to the worship of Apollo, their principal deity. Their belief was that the music purifies the soul, just as medicine purifies the body. They also believed that music was delegated to the same mathematical laws of harmony as the mechanics of the cosmos, evolving into an idea known as the music of the spheres. Apollo appears as the companion of the Muses, and as Musagetes ("leader of Muses") he leads them in dance. They spend their time on Parnassus, which is one of their sacred places. Apollo is also the lover of the Muses and by them he became the father of famous musicians like Orpheus and Linus. Apollo is often found delighting the immortal gods with his songs and music on the lyre. In his role as the god of banquets, he was always present to play music in weddings of the gods, like the marriage of Eros and Psyche, Peleus and Thetis. He is a frequent guest of the Bacchanalia, and many ancient ceramics depict him being at ease amidst the maenads and satyrs. Apollo also participated in musical contests when challenged by others. He was the victor in all those contests, but he tended to punish his opponents severely for their hubris. Apollo's lyre The invention of lyre is attributed either to Hermes or to Apollo himself. Distinctions have been made that Hermes invented lyre made of tortoise shell, whereas the lyre Apollo invented was a regular lyre. Myths tell that the infant Hermes stole a number of Apollo's cows and took them to a cave in the woods near Pylos, covering their tracks. In the cave, he found a tortoise and killed it, then removed the insides. He used one of the cow's intestines and the tortoise shell and made his lyre. Upon discovering the theft, Apollo confronted Hermes and asked him to return his cattle. When Hermes acted innocent, Apollo took the matter to Zeus. Zeus, having seen the events, sided with Apollo, and ordered Hermes to return the cattle. Hermes then began to play music on the lyre he had invented. Apollo fell in love with the instrument and offered to exchange the cattle for the lyre. Hence, Apollo then became the master of the lyre. According to other versions, Apollo had invented the lyre himself, whose strings he tore in repenting of the excess punishment he had given to Marsyas. Hermes' lyre, therefore, would be a reinvention. Contest with Pan Once Pan had the audacity to compare his music with that of Apollo and to challenge the god of music to a contest. The mountain-god Tmolus was chosen to umpire. Pan blew on his pipes, and with his rustic melody gave great satisfaction to himself and his faithful follower, Midas, who happened to be present. Then, Apollo struck the strings of his lyre. It was so beautiful that Tmolus at once awarded the victory to Apollo, and everyone was pleased with the judgement. Only Midas dissented and questioned the justice of the award. Apollo did not want to suffer such a depraved pair of ears any longer, and caused them to become the ears of a donkey. Contest with Marsyas Marsyas was a satyr who was punished by Apollo for his hubris. He had found an aulos on the ground, tossed away after being invented by Athena because it made her cheeks puffy. Athena had also placed a curse upon the instrument, that whoever would pick it up would be severely punished. When Marsyas played the flute, everyone became frenzied with joy. This led Marsyas to think that he was better than Apollo, and he challenged the god to a musical contest. The contest was judged by the Muses, or the nymphs of Nysa. Athena was also present to witness the contest. Marsyas taunted Apollo for "wearing his hair long, for having a fair face and smooth body, for his skill in so many arts". He also further said, 'His [Apollo] hair is smooth and made into tufts and curls that fall about his brow and hang before his face. His body is fair from head to foot, his limbs shine bright, his tongue gives oracles, and he is equally eloquent in prose or verse, propose which you will. What of his robes so fine in texture, so soft to the touch, aglow with purple? What of his lyre that flashes gold, gleams white with ivory, and shimmers with rainbow gems? What of his song, so cunning and so sweet? Nay, all these allurements suit with naught save luxury. To virtue they bring shame alone!' The Muses and Athena sniggered at this comment. The contestants agreed to take turns displaying their skills and the rule was that the victor could "do whatever he wanted" to the loser. According to one account, after the first round, they both were deemed equal by the Nysiads. But in the next round, Apollo decided to play on his lyre and add his melodious voice to his performance. Marsyas argued against this, saying that Apollo would have an advantage and accused Apollo of cheating. But Apollo replied that since Marsyas played the flute, which needed air blown from the throat, it was similar to singing, and that either they both should get an equal chance to combine their skills or none of them should use their mouths at all. The nymphs decided that Apollo's argument was just. Apollo then played his lyre and sang at the same time, mesmerising the audience. Marsyas could not do this. Apollo was declared the winner and, angered with Marsyas' haughtiness and his accusations, decided to flay the satyr. According to another account, Marsyas played his flute out of tune at one point and accepted his defeat. Out of shame, he assigned to himself the punishment of being skinned for a wine sack. Another variation is that Apollo played his instrument upside down. Marsyas could not do this with his instrument. So the Muses who were the judges declared Apollo the winner. Apollo hung Marsyas from a tree to flay him. Apollo flayed the limbs of Marsyas alive in a cave near Celaenae in Phrygia for his hubris to challenge a god. He then gave the rest of his body for proper burial and nailed Marsyas' flayed skin to a nearby pine-tree as a lesson to the others. Marsyas' blood turned into the river Marsyas. But Apollo soon repented and being distressed at what he had done, he tore the strings of his lyre and threw it away. The lyre was later discovered by the Muses and Apollo's sons Linus and Orpheus. The Muses fixed the middle string, Linus the string struck with the forefinger, and Orpheus the lowest string and the one next to it. They took it back to Apollo, but the god, who had decided to stay away from music for a while, laid away both the lyre and the pipes at Delphi and joined Cybele in her wanderings to as far as Hyperborea. Contest with Cinyras Cinyras was a ruler of Cyprus, who was a friend of Agamemnon. Cinyras promised to assist Agamemnon in the Trojan war, but did not keep his promise. Agamemnon cursed Cinyras. He invoked Apollo and asked the god to avenge the broken promise. Apollo then had a lyre-playing contest with Cinyras, and defeated him. Either Cinyras committed suicide when he lost, or was killed by Apollo. Patron of sailors Apollo functions as the patron and protector of sailors, one of the duties he shares with Poseidon. In the myths, he is seen helping heroes who pray to him for safe journey. When Apollo spotted a ship of Cretan sailors that was caught in a storm, he quickly assumed the shape of a dolphin and guided their ship safely to Delphi. When the Argonauts faced a terrible storm, Jason prayed to his patron, Apollo, to help them. Apollo used his bow and golden arrow to shed light upon an island, where the Argonauts soon took shelter. This island was renamed "Anaphe", which means "He revealed it". Apollo helped the Greek hero Diomedes, to escape from a great tempest during his journey homeward. As a token of gratitude, Diomedes built a temple in honor of Apollo under the epithet Epibaterius ("the embarker"). During the Trojan War, Odysseus came to the Trojan camp to return Chriseis, the daughter of Apollo's priest Chryses, and brought many offerings to Apollo. Pleased with this, Apollo sent gentle breezes that helped Odysseus return safely to the Greek camp. Arion was a poet who was kidnapped by some sailors for the rich prizes he possessed. Arion requested them to let him sing for the last time, to which the sailors consented. Arion began singing a song in praise of Apollo, seeking the god's help. Consequently, numerous dolphins surrounded the ship and when Arion jumped into the water, the dolphins carried him away safely. Wars Titanomachy Once Hera, out of spite, aroused the Titans to war against Zeus and take away his throne. Accordingly, when the Titans tried to climb Mount Olympus, Zeus with the help of Apollo, Artemis and Athena, defeated them and cast them into tartarus. Trojan War Apollo played a pivotal role in the entire Trojan War. He sided with the Trojans, and sent a terrible plague to the Greek camp, which indirectly led to the conflict between Achilles and Agamemnon. He killed the Greek heroes Patroclus, Achilles, and numerous Greek soldiers. He also helped many Trojan heroes, the most important one being Hector. After the end of the war, Apollo and Poseidon together cleaned the remains of the city and the camps. Telegony war A war broke out between the Brygoi and the Thesprotians, who had the support of Odysseus. The gods Athena and Ares came to the battlefield and took sides. Athena helped the hero Odysseus while Ares fought alongside of the Brygoi. When Odysseus lost, Athena and Ares came into a direct duel. To stop the battling gods and the terror created by their battle, Apollo intervened and stopped the duel between them . Indian war When Zeus suggested that Dionysus defeat the Indians in order to earn a place among the gods, Dionysus declared war against the Indians and travelled to India along with his army of Bacchantes and satyrs. Among the warriors was Aristaeus, Apollo's son. Apollo armed his son with his own hands and gave him a bow and arrows and fitted a strong shield to his arm. After Zeus urged Apollo to join the war, he went to the battlefield. Seeing several of his nymphs and Aristaeus drowning in a river, he took them to safety and healed them. He taught Aristaeus more useful healing arts and sent him back to help the army of Dionysus. Theban war During the war between the sons of Oedipus, Apollo favored Amphiaraus, a seer and one of the leaders in the war. Though saddened that the seer was fated to be doomed in the war, Apollo made Amphiaraus' last hours glorious by "lighting his shield and his helm with starry gleam". When Hypseus tried to kill the hero by a spear, Apollo directed the spear towards the charioteer of Amphiaraus instead. Then Apollo himself replaced the charioteer and took the reins in his hands. He deflected many spears and arrows away them. He also killed many of the enemy warriors like Melaneus, Antiphus, Aetion, Polites and Lampus. At last when the moment of departure came, Apollo expressed his grief with tears in his eyes and bid farewell to Amphiaraus, who was soon engulfed by the Earth. Slaying of giants Apollo killed the giants Python and Tityos, who had assaulted his mother Leto. Gigantomachy During the gigantomachy, Apollo and Heracles blinded the giant Ephialtes by shooting him in his eyes, Apollo shooting his left and Heracles his right. He also killed Porphyrion, the king of giants, using his bow and arrows. Aloadae The Aloadae, namely Otis and Ephialtes, were twin giants who decided to wage war upon the gods. They attempted to storm Mt. Olympus by piling up mountains, and threatened to fill the sea with mountains and inundate dry land. They even dared to seek the hand of Hera and Artemis in marriage. Angered by this, Apollo killed them by shooting them with arrows. According to another tale, Apollo killed them by sending a deer between them; as they tried to kill it with their javelins, they accidentally stabbed each other and died. Phorbas Phorbas was a savage giant king of Phlegyas who was described as having swine like features. He wished to plunder Delphi for its wealth. He seized the roads to Delphi and started harassing the pilgrims. He captured the old people and children and sent them to his army to hold them for ransom. And he challenged the young and sturdy men to a match of boxing, only to cut their heads off when they would get defeated by him. He hung the chopped off heads to an oak tree. Finally, Apollo came to put an end to this cruelty. He entered a boxing contest with Phorbas and killed him with a single blow. Other stories In the first Olympic games, Apollo defeated Ares and became the victor in wrestling. He outran Hermes in the race and won first place. Apollo divides months into summer and winter. He rides on the back of a swan to the land of the Hyperboreans during the winter months, and the absence of warmth in winters is due to his departure. During his absence, Delphi was under the care of Dionysus, and no prophecies were given during winters. Molpadia and Parthenos Molpadia and Parthenos were the sisters of Rhoeo, a former lover of Apollo. One day, they were put in charge of watching their father's ancestral wine jar but they fell asleep while performing this duty. While they were asleep, the wine jar was broken by the swines their family kept. When the sisters woke up and saw what had happened, they threw themselves off a cliff in fear of their father's wrath. Apollo, who was passing by, caught them and carried them to two different cities in Chersonesus, Molpadia to Castabus and Parthenos to Bubastus. He turned them into goddesses and they both received divine honors. Molpadia's name was changed to Hemithea upon her deification. Prometheus Prometheus was the titan who was punished by Zeus for stealing fire. He was bound to a rock, where each day an eagle was sent to eat Prometheus' liver, which would then grow back overnight to be eaten again the next day. Seeing his plight, Apollo pleaded Zeus to release the kind Titan, while Artemis and Leto stood behind him with tears in their eyes. Zeus, moved by Apollo's words and the tears of the goddesses, finally sent Heracles to free Prometheus. The rock of Leukas Leukatas was believed to be a white colored rock jutting out from the island of Leukas into the sea. It was present in the sanctuary of Apollo Leukates. A leap from this rock was believed to have put an end to the longings of love. Once, Aphrodite fell deeply in love with Adonis, a young man of great beauty who was later accidentally killed by a boar. Heartbroken, Aphrodite wandered looking for the rock of Leukas. When she reached the sanctuary of Apollo in Argos, she confided in him her love and sorrow. Apollo then brought her to the rock of Leukas and asked her to throw herself from the top of the rock. She did so and was freed from her love. When she sought for the reason behind this, Apollo told her that Zeus, before taking another lover, would sit on this rock to free himself from his love to Hera. Another tale relates that a man named Nireus, who fell in love with the cult statue of Athena, came to the rock and jumped in order relieve himself. After jumping, he fell into the net of a fisherman in which, when he was pulled out, he found a box filled with gold. He fought with the fisherman and took the gold, but Apollo appeared to him in the night in a dream and warned him not to appropriate gold which belonged to others. It was an ancestral custom among the Leukadians to fling a criminal from this rock every year at the sacrifice performed in honor of Apollo for the sake of averting evil. However, a number of men would be stationed all around below rock to catch the criminal and take him out of the borders in order to exile him from the island. This was the same rock from which, according to a legend, Sappho took her suicidal leap. Female lovers Love affairs ascribed to Apollo are a late development in Greek mythology. Their vivid anecdotal qualities have made some of them favorites of painters since the Renaissance, the result being that they stand out more prominently in the modern imagination. Daphne was a nymph who scorned Apollo's advances and ran away from him. When Apollo chased her in order to persuade her, she changed herself into a laurel tree. According to other versions, she cried for help during the chase, and Gaia helped her by taking her in and placing a laurel tree in her place. According to Roman poet Ovid, the chase was brought about by Cupid, who hit Apollo with golden arrow of love and Daphne with leaden arrow of hatred. The myth explains the origin of the laurel and connection of Apollo with the laurel and its leaves, which his priestess employed at Delphi. The leaves became the symbol of victory and laurel wreaths were given to the victors of the Pythian games. Apollo is said to have been the lover of all nine Muses, and not being able to choose one of them, decided to remain unwed. He fathered the Corybantes by the Muse Thalia, Orpheus by Calliope, Linus of Thrace by Calliope or Urania and Hymenaios (Hymen) by one of the Muses. Cyrene was a Thessalian princess whom Apollo loved. In her honor, he built the city Cyrene and made her its ruler. She was later granted longevity by Apollo who turned her into a nymph. The couple had two sons, Aristaeus, and Idmon. Evadne was a nymph daughter of Poseidon and a lover of Apollo. She bore him a son, Iamos. During the time of the childbirth, Apollo sent Eileithyia, the goddess of childbirth to assist her. Rhoeo, a princess of the island of Naxos was loved by Apollo. Out of affection for her, Apollo turned her sisters into goddesses. On the island Delos she bore Apollo a son named Anius. Not wanting to have the child, she entrusted the infant to Apollo and left. Apollo raised and educated the child on his own. Ourea, a daughter of Poseidon, fell in love with Apollo when he and Poseidon were serving the Trojan king Laomedon. They both united on the day the walls of Troy were built. She bore to Apollo a son, whom Apollo named Ileus, after the city of his birth, Ilion (Troy). Ileus was very dear to Apollo. Thero, daughter of Phylas, a maiden as beautiful as the moonbeams, was loved by the radiant Apollo, and she loved him in return. By their union, she became mother of Chaeron, who was famed as "the tamer of horses". He later built the city Chaeronea. Hyrie or Thyrie was the mother of Cycnus. Apollo turned both the mother and son into swans when they jumped into a lake and tried to kill themselves. Hecuba was the wife of King Priam of Troy, and Apollo had a son with her named Troilus. An oracle prophesied that Troy would not be defeated as long as Troilus reached the age of twenty alive. He was ambushed and killed by Achilleus, and Apollo avenged his death by killing Achilles. After the sack of Troy, Hecuba was taken to Lycia by Apollo. Coronis was daughter of Phlegyas, King of the Lapiths. While pregnant with Asclepius, Coronis fell in love with Ischys, son of Elatus and slept with him. When Apollo found out about her infidelity through his prophetic powers, he sent his sister, Artemis, to kill Coronis. Apollo rescued the baby by cutting open Koronis' belly and gave it to the centaur Chiron to raise. Dryope, the daughter of Dryops, was impregnated by Apollo in the form of a snake. She gave birth to a son named Amphissus. In Euripides' play Ion, Apollo fathered Ion by Creusa, wife of Xuthus. He used his powers to conceal her pregnancy from her father. Later, when Creusa left Ion to die in the wild, Apollo asked Hermes to save the child and bring him to the oracle at Delphi, where he was raised by a priestess. Male lovers Hyacinth (or Hyacinthus), a beautiful and athletic Spartan prince, was one of Apollo's favourite lovers. The pair was practicing throwing the discus when a discus thrown by Apollo was blown off course by the jealous Zephyrus and struck Hyacinthus in the head, killing him instantly. Apollo is said to be filled with grief. Out of Hyacinthus' blood, Apollo created a flower named after him as a memorial to his death, and his tears stained the flower petals with the interjection , meaning alas. He was later resurrected and taken to heaven. The festival Hyacinthia was a national celebration of Sparta, which commemorated the death and rebirth of Hyacinthus. Another male lover was Cyparissus, a descendant of Heracles. Apollo gave him a tame deer as a companion but Cyparissus accidentally killed it with a javelin as it lay asleep in the undergrowth. Cyparissus was so saddened by its death that he asked Apollo to let his tears fall forever. Apollo granted the request by turning him into the Cypress named after him, which was said to be a sad tree because the sap forms droplets like tears on the trunk. Admetus, the king of Pherae, was also Apollo's lover. During his exile, which lasted either for one year or nine years, Apollo served Admetus as a herdsman. The romantic nature of their relationship was first described by Callimachus of Alexandria, who wrote that Apollo was "fired with love" for Admetus. Plutarch lists Admetus as one of Apollo's lovers and says that Apollo served Admetus because he doted upon him. Latin poet Ovid in his Ars Amatoria said that even though he was a god, Apollo forsook his pride and stayed in as a servant for the sake of Admetus. Tibullus desrcibes Apollo's love to the king as servitium amoris (slavery of love) and asserts that Apollo became his servant not by force but by choice. He would also make cheese and serve it to Admetus. His domestic actions caused embarrassment to his family. When Admetus wanted to marry princess Alcestis, Apollo provided a chariot pulled by a lion and a boar he had tamed. This satisfied Alcestis' father and he let Admetus marry his daughter. Further, Apollo saved the king from Artemis' wrath and also convinced the Moirai to postpone Admetus' death once. Branchus, a shepherd, one day came across Apollo in the woods. Captivated by the god's beauty, he kissed Apollo. Apollo requited his affections and wanting to reward him, bestowed prophetic skills on him. His descendants, the Branchides, were an influential clan of prophets. Other male lovers of Apollo include: Adonis, who is said to have been the lover of both Apollo and Aphrodite. He behaved as a man with Aphrodite and as a woman with Apollo. Atymnius, otherwise known as a beloved of Sarpedon Boreas, the god of North winds Helenus, the son of Priam and a Trojan Prince, was a lover of Apollo and received from him an ivory bow with which he later wounded Achilles in the hand. Hippolytus of Sicyon (not the same as Hippolytus, the son of Theseus) Hymenaios, the son of Magnes Iapis, to whom Apollo taught the art of healing Phorbas, the dragon slayer (probably the son of Triopas) Children Apollo sired many children, from mortal women and nymphs as well as the goddesses. His children grew up to be physicians, musicians, poets, seers or archers. Many of his sons founded new cities and became kings. They were all usually very beautiful. Asclepius is the most famous son of Apollo. His skills as a physician surpassed that of Apollo's. Zeus killed him for bringing back the dead, but upon Apollo's request, he was resurrected as a god. Aristaeus was placed under the care of Chiron after his birth. He became the god of beekeeping, cheese making, animal husbandry and more. He was ultimately given immortality for the benefits he bestowed upon the humanity. The Corybantes were spear-clashing, dancing demigods. The sons of Apollo who participated in the Trojan War include the Trojan princes Hector and Troilus, as well as Tenes, the king of Tenedos, all three of whom were killed by Achilles over the course of the war. Apollo's children who became musicians and bards include Orpheus, Linus, Ialemus, Hymenaeus, Philammon, Eumolpus and Eleuther. Apollo fathered 3 daughters, Apollonis, Borysthenis and Cephisso, who formed a group of minor Muses, the "Musa Apollonides". They were nicknamed Nete, Mese and Hypate after the highest, middle and lowest strings of his lyre. Phemonoe was a seer and a poetess who was the inventor of Hexameter. Apis, Idmon, Iamus, Tenerus, Mopsus, Galeus, Telmessus and others were gifted seers. Anius, Pythaeus and Ismenus lived as high priests. Most of them were trained by Apollo himself. Arabus, Delphos, Dryops, Miletos, Tenes, Epidaurus, Ceos, Lycoras, Syrus, Pisus, Marathus, Megarus, Patarus, Acraepheus, Cicon, Chaeron and many other sons of Apollo, under the guidance of his words, founded eponymous cities. He also had a son named Chrysorrhoas who was a mechanic artist. His other daughters include Eurynome, Chariclo wife of Chiron, Eurydice the wife of Orpheus, Eriopis, famous for her beautiful hair, Melite the heroine, Pamphile the silk weaver, Parthenos, and by some accounts, Phoebe, Hilyra and Scylla. Apollo turned Parthenos into a constellation after her early death. Additionally, Apollo fostered and educated Chiron, the centaur who later became the greatest teacher and educated many demigods, including Apollo's sons. Apollo also fostered Carnus, the son of Zeus and Europa. Failed love attempts Marpessa was kidnapped by Idas but was loved by Apollo as well. Zeus made her choose between them, and she chose Idas on the grounds that Apollo, being immortal, would tire of her when she grew old. Sinope, a nymph, was approached by the amorous Apollo. She made him promise that he would grant to her whatever she would ask for, and then cleverly asked him to let her stay a virgin. Apollo kept his promise and went back. Bolina was admired by Apollo but she refused him and jumped into the sea. To avoid her death, Apollo turned her into a nymph and let her go. Castalia was a nymph whom Apollo loved. She fled from him and dove into the spring at Delphi, at the base of Mt. Parnassos, which was then named after her. Water from this spring was sacred; it was used to clean the Delphian temples and inspire the priestesses. Cassandra, was a daughter of Hecuba and Priam. Apollo wished to court her. Cassandra promised to return his love on one condition - he should give her the power to see the future. Apollo fulfilled her wish, but she went back on her word and rejected him soon after. Angered that she broke her promise, Apollo cursed her that even though she would see the future, no one would ever believe her prophecies. Hestia, the goddess of the hearth, rejected both Apollo's and Poseidon's marriage proposals and swore that she would always stay unmarried. Female counterparts Artemis Artemis as the sister of Apollo, is thea apollousa, that is, she as a female divinity represented the same idea that Apollo did as a male divinity. In the pre-Hellenic period, their relationship was described as the one between husband and wife, and there seems to have been a tradition which actually described Artemis as the wife of Apollo. However, this relationship was never sexual but spiritual, which is why they both are seen being unmarried in the Hellenic period. Artemis, like her brother, is armed with a bow and arrows. She is the cause of sudden deaths of women. She also is the protector of the young, especially girls. Though she has nothing to do with oracles, music or poetry, she sometimes led the female chorus on Olympus while Apollo sang. The laurel (daphne) was sacred to both. Artemis Daphnaia had her temple among the Lacedemonians, at a place called Hypsoi. Apollo Daphnephoros had a temple in Eretria, a "place where the citizens are to take the oaths". In later times when Apollo was regarded as identical with the sun or Helios, Artemis was naturally regarded as Selene or the moon. Hecate Hecate, the goddess of witchcraft and magic, is the chthonic counterpart of Apollo. They both are cousins, since their mothers - Leto and Asteria - are sisters. One of Apollo's epithets, Hecatos, is the masculine form of Hecate, and both the names mean "working from afar". While Apollo presided over the prophetic powers and magic of light and heaven, Hecate presided over the prophetic powers and magic of night and chthonian darkness. If Hecate is the "gate-keeper", Apollo Agyieus is the "door-keeper". Hecate is the goddess of crossroads and Apollo is the god and protector of streets. The oldest evidence found for Hecate's worship is at Apollo's temple in Miletos. There, Hecate was taken to be Apollo's sister counterpart in the absence of Artemis. Hecate's lunar nature makes her the goddess of the waning moon and contrasts and complements, at the same time, Apollo's solar nature. Athena As a deity of knowledge and great power, Apollo was seen being the male counterpart of Athena. Being Zeus' favorite children, they were given more powers and duties. Apollo and Athena often took up the role as protectors of cities, and were patrons of some of the important cities. Athena was the principle goddess of Athens, Apollo was the principle god of Sparta. As patrons of arts, Apollo and Athena were companions of the Muses, the former a much more frequent companion than the latter. Apollo was sometimes called the son of Athena and Hephaestus. In the Trojan war, as Zeus' executive, Apollo is seen holding the aegis like Athena usually does. Apollo's decisions were usually approved by his sister Athena, and they both worked to establish the law and order set forth by Zeus. Apollo in the Oresteia In Aeschylus' Oresteia trilogy, Clytemnestra kills her husband, King Agamemnon because he had sacrificed their daughter Iphigenia to proceed forward with the Trojan war. Apollo gives an order through the Oracle at Delphi that Agamemnon's son, Orestes, is to kill Clytemnestra and Aegisthus, her lover. Orestes and Pylades carry out the revenge, and consequently Orestes is pursued by the Erinyes or Furies (female personifications of vengeance). Apollo and the Furies argue about whether the matricide was justified; Apollo holds that the bond of marriage is sacred and Orestes was avenging his father, whereas the Erinyes say that the bond of blood between mother and son is more meaningful than the bond of marriage. They invade his temple, and he drives them away. He says that the matter should be brought before Athena. Apollo promises to protect Orestes, as Orestes has become Apollo's supplicant. Apollo advocates Orestes at the trial, and ultimately Athena rules in favor of Apollo. Roman Apollo The Roman worship of Apollo was adopted from the Greeks. As a quintessentially Greek god, Apollo had no direct Roman equivalent, although later Roman poets often referred to him as Phoebus. There was a tradition that the Delphic oracle was consulted as early as the period of the kings of Rome during the reign of Tarquinius Superbus. On the occasion of a pestilence in the 430s BCE, Apollo's first temple at Rome was established in the Flaminian fields, replacing an older cult site there known as the "Apollinare". During the Second Punic War in 212 BCE, the Ludi Apollinares ("Apollonian Games") were instituted in his honor, on the instructions of a prophecy attributed to one Marcius. In the time of Augustus, who considered himself under the special protection of Apollo and was even said to be his son, his worship developed and he became one of the chief gods of Rome. After the battle of Actium, which was fought near a sanctuary of Apollo, Augustus enlarged Apollo's temple, dedicated a portion of the spoils to him, and instituted quinquennial games in his honour. He also erected a new temple to the god on the Palatine hill. Sacrifices and prayers on the Palatine to Apollo and Diana formed the culmination of the Secular Games, held in 17 BCE to celebrate the dawn of a new era. Festivals The chief Apollonian festival was the Pythian Games held every four years at Delphi and was one of the four great Panhellenic Games. Also of major importance was the Delia held every four years on Delos. Athenian annual festivals included the Boedromia, Metageitnia, Pyanepsia, and Thargelia. Spartan annual festivals were the Carneia and the Hyacinthia. Thebes every nine years held the Daphnephoria. Attributes and symbols Apollo's most common attributes were the bow and arrow. Other attributes of his included the kithara (an advanced version of the common lyre), the plectrum and the sword. Another common emblem was the sacrificial tripod, representing his prophetic powers. The Pythian Games were held in Apollo's honor every four years at Delphi. The bay laurel plant was used in expiatory sacrifices and in making the crown of victory at these games. The palm tree was also sacred to Apollo because he had been born under one in Delos. Animals sacred to Apollo included wolves, dolphins, roe deer, swans, cicadas (symbolizing music and song), ravens, hawks, crows (Apollo had hawks and crows as his messengers), snakes (referencing Apollo's function as the god of prophecy), mice and griffins, mythical eagle–lion hybrids of Eastern origin. Homer and Porphyry wrote that Apollo had a hawk as his messenger. In many myths Apollo is transformed into a hawk. In addition, Claudius Aelianus wrote that in Ancient Egypt people believed that hawks were sacred to the god and that according to the ministers of Apollo in Egypt there were certain men called "hawk-keepers" (ἱερακοβοσκοί) who fed and tended the hawks belonging to the god. Eusebius wrote that the second appearance of the moon is held sacred in the city of Apollo in Egypt and that the city's symbol is a man with a hawklike face (Horus). Claudius Aelianus wrote that Egyptians called Apollo Horus in their own language. As god of colonization, Apollo gave oracular guidance on colonies, especially during the height of colonization, 750–550 BCE. According to Greek tradition, he helped Cretan or Arcadian colonists found the city of Troy. However, this story may reflect a cultural influence which had the reverse direction: Hittite cuneiform texts mention an Asia Minor god called Appaliunas or Apalunas in connection with the city of Wilusa attested in Hittite inscriptions, which is now generally regarded as being identical with the Greek Ilion by most scholars. In this interpretation, Apollo's title of Lykegenes can simply be read as "born in Lycia", which effectively severs the god's supposed link with wolves (possibly a folk etymology). In literary contexts, Apollo represents harmony, order, and reason—characteristics contrasted with those of Dionysus, god of wine, who represents ecstasy and disorder. The contrast between the roles of these gods is reflected in the adjectives Apollonian and Dionysian. However, the Greeks thought of the two qualities as complementary: the two gods are brothers, and when Apollo at winter left for Hyperborea, he would leave the Delphic oracle to Dionysus. This contrast appears to be shown on the two sides of the Borghese Vase. Apollo is often associated with the Golden Mean. This is the Greek ideal of moderation and a virtue that opposes gluttony. Apollo in the arts Apollo is a common theme in Greek and Roman art and also in the art of the Renaissance. The earliest Greek word for a statue is "delight" (, agalma), and the sculptors tried to create forms which would inspire such guiding vision. Greek art puts into Apollo the highest degree of power and beauty that can be imagined. The sculptors derived this from observations on human beings, but they also embodied in concrete form, issues beyond the reach of ordinary thought. The naked bodies of the statues are associated with the cult of the body that was essentially a religious activity. The muscular frames and limbs combined with slim waists indicate the Greek desire for health, and the physical capacity which was necessary in the hard Greek environment. The statues of Apollo embody beauty, balance and inspire awe before the beauty of the world. Archaic sculpture Numerous free-standing statues of male youths from Archaic Greece exist, and were once thought to be representations of Apollo, though later discoveries indicated that many represented mortals. In 1895, V. I. Leonardos proposed the term kouros ("male youth") to refer to those from Keratea; this usage was later expanded by Henri Lechat in 1904 to cover all statues of this format. The earliest examples of life-sized statues of Apollo may be two figures from the Ionic sanctuary on the island of Delos. Such statues were found across the Greek speaking world, the preponderance of these were found at the sanctuaries of Apollo with more than one hundred from the sanctuary of Apollo Ptoios, Boeotia alone. Significantly more rare are the life-sized bronze statues. One of the few originals which survived into the present day—so rare that its discovery in 1959 was described as "a miracle" by Ernst Homann-Wedeking—is the masterpiece bronze, Piraeus Apollo. It was found in Piraeus, a port city close to Athens, and is believed to have come from north-eastern Peloponnesus. It is the only surviving large-scale Peloponnesian statue. Classical sculpture The famous Apollo of Mantua and its variants are early forms of the Apollo Citharoedus statue type, in which the god holds the cithara, a sophisticated seven-stringed variant of the lyre, in his left arm. While none of the Greek originals have survived, several Roman copies from approximately the late 1st or early 2nd century exist. Other notable forms are the Apollo Citharoedus and the Apollo Barberini. Hellenistic Greece-Rome Apollo as a handsome beardless young man, is often depicted with a cithara (as Apollo Citharoedus) or bow in his hand, or reclining on a tree (the Apollo Lykeios and Apollo Sauroctonos types). The Apollo Belvedere is a marble sculpture that was rediscovered in the late 15th century; for centuries it epitomized the ideals of Classical Antiquity for Europeans, from the Renaissance through the 19th century. The marble is a Hellenistic or Roman copy of a bronze original by the Greek sculptor Leochares, made between 350 and 325 BCE. The life-size so-called "Adonis" found in 1780 on the site of a villa suburbana near the Via Labicana in the Roman suburb of Centocelle is identified as an Apollo by modern scholars. In the late 2nd century CE floor mosaic from El Djem, Roman Thysdrus, he is identifiable as Apollo Helios by his effulgent halo, though now even a god's divine nakedness is concealed by his cloak, a mark of increasing conventions of modesty in the later Empire. Another haloed Apollo in mosaic, from Hadrumentum, is in the museum at Sousse. The conventions of this representation, head tilted, lips slightly parted, large-eyed, curling hair cut in locks grazing the neck, were developed in the 3rd century BCE to depict Alexander the Great. Some time after this mosaic was executed, the earliest depictions of Christ would also be beardless and haloed. Modern reception Apollo often appears in modern and popular culture due to his status as the god of music, dance and poetry. Postclassical art and literature Dance and music Apollo has featured in dance and music in modern culture. Percy Bysshe Shelley composed a "Hymn of Apollo" (1820), and the god's instruction of the Muses formed the subject of Igor Stravinsky's Apollon musagète (1927–1928). In 1978, the Canadian band Rush released an album with songs "Apollo: Bringer of Wisdom"/"Dionysus: Bringer of Love". Books Apollo been portrayed in modern literature, such as when Charles Handy, in Gods of Management (1978) uses Greek gods as a metaphor to portray various types of organizational culture. Apollo represents a 'role' culture where order, reason, and bureaucracy prevail. In 2016, author Rick Riordan published the first book in the Trials of Apollo series, publishing four other books in the series in 2017, 2018, 2019 and 2020. Film Apollo has been depicted in modern films—for instance, by Keith David in the 1997 animated feature film Hercules, by Luke Evans in the 2010 action film Clash of the Titans, and by Dimitri Lekkos in the 2010 film Percy Jackson & the Olympians: The Lightning Thief. Video games Apollo has appeared in many modern video games. Apollo appears as a minor character in Santa Monica Studio's 2010 action-adventure game God of War III with his bow being used by Peirithous. He also appears in the 2014 Hi-Rez Studios Multiplayer Online Battle Arena game Smite as a playable character. Psychology and philosophy In philosophical discussion of the arts, a distinction is sometimes made between the Apollonian and Dionysian impulses where the former is concerned with imposing intellectual order and the latter with chaotic creativity. Friedrich Nietzsche argued that a fusion of the two was most desirable. Psychologist Carl Jung's Apollo archetype represents what he saw as the disposition in people to over-intellectualise and maintain emotional distance. Spaceflight In spaceflight, the 1960s and 1970s NASA program for orbiting and landing astronauts on the Moon was named after Apollo, by NASA manager Abe Silverstein: "Apollo riding his chariot across the Sun was appropriate to the grand scale of the proposed program." Genealogy See also Family tree of the Greek gods Dryad Epirus Phoebus (disambiguation) Sibylline oracles Tegyra Temple of Apollo (disambiguation) Notes References Sources Primary sources Aelian, On Animals, Volume II: Books 6-11. Translated by A. F. Scholfield. Loeb Classical Library 447. Cambridge, MA: Harvard University Press, 1958. Aeschylus, The Eumenides in Aeschylus, with an English translation by Herbert Weir Smyth, Ph. D. in two volumes, Vol 2, Cambridge, Massachusetts, Harvard University Press, 1926, Online version at the Perseus Digital Library. Antoninus Liberalis, The Metamorphoses of Antoninus Liberalis translated by Francis Celoria (Routledge 1992). Online version at the Topos Text Project. Apollodorus, Apollodorus, The Library, with an English Translation by Sir James George Frazer, F.B.A., F.R.S. in 2 Volumes. Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1921. Online version at the Perseus Digital Library. Apollonius of Rhodes, Apollonius Rhodius: the Argonautica, translated by Robert Cooper Seaton, W. Heinemann, 1912. Internet Archive. Callimachus, Callimachus and Lycophron with an English Translation by A. W. Mair; Aratus, with an English Translation by G. R. Mair, London: W. Heinemann, New York: G. P. Putnam 1921. Online version at Harvard University Press. Internet Archive. Cicero, Marcus Tullius, De Natura Deorum in Cicero in Twenty-eight Volumes, XIX De Natura Deorum; Academica, with an english translation by H. Rackham, Cambridge, Massachusetts: Harvard University Press; London: William Heinemann, Ltd, 1967. Internet Archive. Diodorus Siculus, Library of History, Volume III: Books 4.59-8, translated by C. H. Oldfather, Loeb Classical Library No. 340. Cambridge, Massachusetts, Harvard University Press, 1939. . Online version at Harvard University Press. Online version by Bill Thayer. Herodotus, Herodotus, with an English translation by A. D. Godley. Cambridge. Harvard University Press. 1920. Online version available at The Perseus Digital Library. Hesiod, Theogony, in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, MA., Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library. Homeric Hymn 3 to Apollo in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, MA., Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library. Homeric Hymn 4 to Hermes, in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library. Homer, The Iliad with an English Translation by A.T. Murray, PhD in two volumes. Cambridge, MA., Harvard University Press; London, William Heinemann, Ltd. 1924. Online version at the Perseus Digital Library. Homer; The Odyssey with an English Translation by A.T. Murray, PH.D. in two volumes. Cambridge, MA., Harvard University Press; London, William Heinemann, Ltd. 1919. Online version at the Perseus Digital Library. Hyginus, Gaius Julius, De Astronomica, in The Myths of Hyginus, edited and translated by Mary A. Grant, Lawrence: University of Kansas Press, 1960. Online version at ToposText. Hyginus, Gaius Julius, Fabulae, in The Myths of Hyginus, edited and translated by Mary A. Grant, Lawrence: University of Kansas Press, 1960. Online version at ToposText. Livy, The History of Rome, Books I and II With An English Translation. Cambridge. Cambridge, Mass., Harvard University Press; London, William Heinemann, Ltd. 1919. Nonnus, Dionysiaca; translated by Rouse, W H D, I Books I-XV. Loeb Classical Library No. 344, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1940. Internet Archive Nonnus, Dionysiaca; translated by Rouse, W H D, II Books XVI-XXXV. Loeb Classical Library No. 345, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1940. Internet Archive Statius, Thebaid. Translated by Mozley, J H. Loeb Classical Library Volumes. Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1928. Strabo, The Geography of Strabo. Edition by H.L. Jones. Cambridge, Mass.: Harvard University Press; London: William Heinemann, Ltd. 1924. Online version at the Perseus Digital Library. Sophocles, Oedipus Rex Palaephatus, On Unbelievable Tales 46. Hyacinthus (330 BCE) Ovid, Metamorphoses, Brookes More, Boston, Cornhill Publishing Co. 1922. Online version at the Perseus Digital Library. 10. 162–219 (1–8 CE) Pausanias, Pausanias Description of Greece with an English Translation by W.H.S. Jones, Litt.D., and H.A. Ormerod, M.A., in 4 Volumes. Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1918. Online version at the Perseus Digital Library. Philostratus the Elder, Imagines, in Philostratus the Elder, Imagines. Philostratus the Younger, Imagines. Callistratus, Descriptions. Translated by Arthur Fairbanks. Loeb Classical Library No. 256. Cambridge, Massachusetts: Harvard University Press, 1931. . Online version at Harvard University Press. Internet Archive 1926 edition. i.24 Hyacinthus (170–245 CE) Philostratus the Younger, Imagines, in Philostratus the Elder, Imagines. Philostratus the Younger, Imagines. Callistratus, Descriptions. Translated by Arthur Fairbanks. Loeb Classical Library No. 256. Cambridge, Massachusetts: Harvard University Press, 1931. . Online version at Harvard University Press. Internet Archive 1926 edition. 14. Hyacinthus (170–245 CE) Pindar, Odes, Diane Arnson Svarlien. 1990. Online version at the Perseus Digital Library. Plutarch. Lives, Volume I: Theseus and Romulus. Lycurgus and Numa. Solon and Publicola. Translated by Bernadotte Perrin. Loeb Classical Library No. 46. Cambridge, Massachusetts: Harvard University Press, 1914. . Online version at Harvard University Press. Numa at the Perseus Digital Library. Pseudo-Plutarch, De fluviis, in Plutarch's morals, Volume V, edited and translated by William Watson Goodwin, Boston: Little, Brown & Co., 1874. Online version at the Perseus Digital Library. Lucian, Dialogues of the Dead. Dialogues of the Sea-Gods. Dialogues of the Gods. Dialogues of the Courtesans, translated by M. D. MacLeod, Loeb Classical Library No. 431, Cambridge, Massachusetts, Harvard University Press, 1961. . Online version at Harvard University Press. Internet Archive. First Vatican Mythographer, 197. Thamyris et Musae Tzetzes, John, Chiliades, editor Gottlieb Kiessling, F.C.G. Vogel, 1826. Google Books. (English translation: Book I by Ana Untila; Books II–IV, by Gary Berkowitz; Books V–VI by Konstantino Ramiotis; Books VII–VIII by Vasiliki Dogani; Books IX–X by Jonathan Alexander; Books XII–XIII by Nikolaos Giallousis. Internet Archive). Valerius Flaccus, Argonautica, translated by J. H. Mozley, Loeb Classical Library No. 286. Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1928. . Online version at Harvard University Press. Online translated text available at theoi.com. Vergil, Aeneid. Theodore C. Williams. trans. Boston. Houghton Mifflin Co. 1910. Online version at the Perseus Digital Library. Secondary sources Athanassakis, Apostolos N., and Benjamin M. Wolkow, The Orphic Hymns, Johns Hopkins University Press; owlerirst Printing edition (May 29, 2013). . Google Books. M. Bieber, 1964. Alexander the Great in Greek and Roman Art. Chicago. Hugh Bowden, 2005. Classical Athens and the Delphic Oracle: Divination and Democracy. Cambridge University Press. Walter Burkert, 1985. Greek Religion (Harvard University Press) III.2.5 passim Fontenrose, Joseph Eddy, Python: A Study of Delphic Myth and Its Origins, University of California Press, 1959. . Gantz, Timothy, Early Greek Myth: A Guide to Literary and Artistic Sources, Johns Hopkins University Press, 1996, Two volumes: (Vol. 1), (Vol. 2). Miranda J. Green, 1997. Dictionary of Celtic Myth and Legend, Thames and Hudson. Grimal, Pierre, The Dictionary of Classical Mythology, Wiley-Blackwell, 1996. . Hard, Robin, The Routledge Handbook of Greek Mythology: Based on H.J. Rose's "Handbook of Greek Mythology", Psychology Press, 2004, . Google Books. Karl Kerenyi, 1953. Apollon: Studien über Antiken Religion und Humanität revised edition. Kerényi, Karl 1951, The Gods of the Greeks, Thames and Hudson, London. Mertens, Dieter; Schutzenberger, Margareta. Città e monumenti dei Greci d'Occidente: dalla colonizzazione alla crisi di fine V secolo a.C.. Roma L'Erma di Bretschneider, 2006. . Martin Nilsson, 1955. Die Geschichte der Griechische Religion, vol. I. C.H. Beck. Parada, Carlos, Genealogical Guide to Greek Mythology, Jonsered, Paul Åströms Förlag, 1993. . Pauly–Wissowa, Realencyclopädie der klassischen Altertumswissenschaft: II, "Apollon". The best repertory of cult sites (Burkert). Peck, Harry Thurston, Harpers Dictionary of Classical Antiquities, New York. Harper and Brothers. 1898. Online version at the Perseus Digital Library. Pfeiff, K.A., 1943. Apollon: Wandlung seines Bildes in der griechischen Kunst. Traces the changing iconography of Apollo. D.S.Robertson (1945) A handbook of Greek and Roman Architecture Cambridge University Press Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Apollo" Smith, William, A Dictionary of Greek and Roman Antiquities. William Smith, LLD. William Wayte. G. E. Marindin. Albemarle Street, London. John Murray. 1890. Online version at the Perseus Digital Library. Spivey Nigel (1997) Greek art Phaedon Press Ltd. External links Apollo at the Greek Mythology Link, by Carlos Parada The Warburg Institute Iconographic Database: ca 1650 images of Apollo Beauty gods Health gods Knowledge gods Light deities Maintenance deities Music and singing gods Oracular gods Solar gods Greek gods Roman gods Dragonslayers Mythological Greek archers Mythological rapists Homosexuality and bisexuality deities Divine twins Deities in the Iliad Metamorphoses characters Characters in Greek mythology LGBT themes in Greek mythology Children of Zeus Characters in the Odyssey Characters in the Argonautica

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

600

https://en.wikipedia.org/wiki/Andorra

Andorra

Andorra, officially the Principality of Andorra, is a sovereign landlocked microstate on the Iberian Peninsula, in the eastern Pyrenees, bordered by France to the north and Spain to the south. Believed to have been created by Charlemagne, Andorra was ruled by the count of Urgell until 988, when it was transferred to the Roman Catholic Diocese of Urgell. The present principality was formed by a charter in 1278. It is headed by two co-princes: the Bishop of Urgell in Catalonia, Spain and the President of France. Its capital and largest city is Andorra la Vella. Andorra is the sixth-smallest state in Europe, with an area of and a population of approximately . The Andorran people are a Romance ethnic group of originally Catalan descent. Andorra is the world's 16th-smallest country by land and 11th-smallest by population. Its capital, Andorra la Vella, is the highest capital city in Europe, at an elevation of above sea level. The official language is Catalan, but Spanish, Portuguese, and French are also commonly spoken. Tourism in Andorra sees an estimated 10.2 million visitors annually. Andorra is not a member state of the European Union, but the euro is its official currency. It has been a member of the United Nations since 1993. In 2013, Andorra had the highest life expectancy in the world at 81 years, according to the Global Burden of Disease Study; in 2019, it had the 23rd-highest at 81.9 years, according to the United Nations Development Programme. Etymology The origin of the word Andorra is unknown, although several hypotheses have been formulated. The oldest derivation is from the Greek historian Polybius (The Histories III, 35, 1), who describes the Andosins, an Iberian Pre-Roman tribe, as historically located in the valleys of Andorra and facing the Carthaginian army in its passage through the Pyrenees during the Punic Wars. The word Andosini or Andosins () may derive from the Basque , meaning "big" or "giant". The Andorran toponymy shows evidence of Basque language in the area. Another theory suggests that the word Andorra may derive from the old word Anorra that contains the Basque word (water). Another theory suggests that Andorra may derive from , meaning "the thickly wooded place". When the Arabs and Moors conquered the Iberian Peninsula, the valleys of the High Pyrenees were covered by large tracts of forest. These regions were not administered by Muslims, because of the geographic difficulty of direct rule. Other theories suggest that the term derives from the Navarro-Aragonese "andurrial", which means "land covered with bushes" or "scrubland". The folk etymology holds that Charlemagne had named the region as a reference to the Biblical Canaanite valley of Endor or Andor (where the Midianites had been defeated), a name bestowed by his heir and son Louis the Pious after defeating the Moors in the "wild valleys of Hell". History Prehistory La Balma de la Margineda, found by archaeologists at Sant Julià de Lòria, was settled in 9,500 BC as a passing place between the two sides of the Pyrenees. The seasonal camp was perfectly located for hunting and fishing by the groups of hunter-gatherers from Ariege and Segre. During the Neolithic Age, a group of people moved to the Valley of Madriu (the present-day Natural Parc located in Escaldes-Engordany declared UNESCO World Heritage Site) as a permanent camp in 6640 BC. The population of the valley grew cereals, raised domestic livestock, and developed a commercial trade with people from the Segre and Occitania. Other archaeological deposits include the Tombs of Segudet (Ordino) and Feixa del Moro (Sant Julià de Lòria), both dated in 4900–4300 BC as an example of the Urn culture in Andorra. The model of small settlements began to evolve to a complex urbanism during the Bronze Age. Metallurgical items of iron, ancient coins, and relicaries can be found in the ancient sanctuaries scattered around the country. The sanctuary of Roc de les Bruixes (Stone of the Witches) is perhaps the most important archeological complex of this age in Andorra, located in the parish of Canillo, about the rituals of funerals, ancient scripture and engraved stone murals. Iberian and Roman Andorra The inhabitants of the valleys were traditionally associated with the Iberians and historically located in Andorra as the Iberian tribe Andosins or Andosini () during the 7th and 2nd centuries BC. Influenced by the Aquitanian, Basque and Iberian languages, the locals developed some current toponyms. Early writings and documents relating to this group of people goes back to the second century BC by the Greek writer Polybius in his Histories during the Punic Wars. Some of the most significant remains of this era are the Castle of the Roc d'Enclar (part of the early Marca Hispanica), l'Anxiu in Les Escaldes and Roc de L'Oral in Encamp. The presence of Roman influence is recorded from the 2nd century BC to the 5th century AD. The places with the most Roman presence are in Camp Vermell (Red Field) in Sant Julià de Lòria, and in some places in Encamp, as well as in the Roc d'Enclar. People continued trading, mainly with wine and cereals, with the Roman cities of Urgellet (the present-day La Seu d'Urgell) and all across Segre through the via romana Strata Ceretana (also known as Strata Confluetana). Visigoths and Carolingians: the legend of Charlemagne After the fall of the Roman Empire, Andorra came under the influence of the Visigoths, the Kingdom of Toledo, and the Diocese of Urgell. The Visigoths remained in the valleys for 200 years, during which time Christianity spread. When the Muslim Empire of Al-Andalus replaced the ruling Visigoths in most of the Iberian Peninsula, Andorra was sheltered from these invaders by the Franks. Tradition holds that Charles the Great (Charlemagne) granted a charter to the Andorran people for a contingent of 5,000 soldiers under the command of Marc Almugaver, in return for fighting against the Moors near Porté-Puymorens (Cerdanya). Andorra remained part of the Frankish Marca Hispanica, the buffer zone between the Frankish Empire and the Muslim territories, Andorra being part of the territory ruled by the Count of Urgell and eventually the bishop of the Diocese of Urgell. Tradition also holds that it was guaranteed by the son of Charlemagne, Louis the Pious, writing the Carta de Poblament or a local municipal charter circa 805. In 988, Borrell II, Count of Urgell, gave the Andorran valleys to the Diocese of Urgell in exchange for land in Cerdanya. Since then, the Bishop of Urgell, based in Seu d'Urgell, has been co-prince of Andorra. The first document that mentions Andorra as a territory is the Acta de Consagració i Dotació de la Catedral de la Seu d'Urgell (Deed of Consecration and Endowment of the Cathedral of La Seu d'Urgell). The document, dated 839, depicts the six old parishes of the Andorran valleys that made up the country's administrative division. Medieval Age: The Paréages and the founding of the Co-Principality Before 1095, Andorra had no military protection, and the Bishop of Urgell, who knew that the count of Urgell wanted to reclaim the Andorran valleys, asked the lord of Caboet for help and protection. In 1095, the Lord of Caboet and the bishop of Urgell signed under oath a declaration of their co-sovereignty over Andorra. Arnalda, daughter of Arnau of Caboet, married the viscount of Castellbò. Their daughter, Ermessenda, married the count of Foix, Roger-Bernard II. Roger-Bernard II and Ermessenda shared rule over Andorra with the bishop of Urgell. In the 13th century, a military dispute arose between the bishop of Urgell and the count of Foix as aftermath of the Cathar Crusade. The conflict was resolved in 1278 with the mediation of the king of Aragon, Peter III, between the bishop and the count, by the signing of the first paréage, which provided that Andorra's sovereignty be shared between the count of Foix (whose title would ultimately transfer to the French head of state) and the bishop of Urgell, in Catalonia. This gave the principality its territory and political form. A second paréage was signed in 1288 after a dispute when the count of Foix ordered the construction of a castle in Roc d'Enclar. The document was ratified by the noble notary Jaume Orig of Puigcerdà, and construction of military structures in the country was prohibited. In 1364, the political organization of the country named the figure of the syndic (now spokesman and president of the parliament) as representative of the Andorrans to their co-princes, making possible the creation of local departments (comuns, quarts and veïnats). After being ratified by Bishop Francesc Tovia and Count John I, the Consell de la Terra or Consell General de les Valls (General Council of the Valleys) was founded in 1419, the second oldest parliament in Europe. The syndic Andreu d'Alàs and the General Council organized the creation of the Justice Courts (La Cort de Justicia) in 1433 with the co-princes and the collection of taxes like foc i lloc (literally "fire and site", a national tax active since then). Although there are remains of ecclesiastical works dating before the 9th century (Sant Vicenç d'Enclar or Església de Santa Coloma), Andorra developed exquisite Romanesque Art during the 9th through 14th centuries, particularly in the construction of churches, bridges, religious murals and statues of the Virgin and Child (Our Lady of Meritxell being the most important). Nowadays, the Romanesque buildings that form part of Andorra's cultural heritage stand out in a remarkable way, with an emphasis on Església de Sant Esteve, Sant Joan de Caselles, Església de Sant Miquel d'Engolasters, Sant Martí de la Cortinada and the medieval bridges of Margineda and Escalls among many others. The Catalan Pyrenees were embryonic of the Catalan language at the end of the 11th century. Andorra was influenced by this language, which was adopted locally decades before it expanded to the rest of the Crown of Aragon. The local economy during the Middle Ages was based on livestock, agriculture, furs and weavers. Later, at the end of the 11th century, the first iron foundries began to appear in Northern Parishes like Ordino, much appreciated by the master artisans who developed the art of the forges, an important economic activity in the country from the 15th century. 16th to 18th centuries In 1601, the Tribunal de Corts (High Court of Justice) was created as a result of Huguenot rebellions in France, Inquisition courts coming from Spain and witchcraft-related beliefs native to the area, in the context of the Reformation and Counter-Reformation. With the passage of time, the co-title to Andorra passed to the kings of Navarre. After Henry III of Navarre became king of France, he issued an edict in 1607 that established the head of the French state and the bishop of Urgell as co-princes of Andorra, a political arrangement that still holds. During 1617, communal councils form the sometent (popular militia or army) to deal with the rise of bandolerisme (brigandage) and the Consell de la Terra was defined and structured in terms of its composition, organization and competences current today. Andorra continued with the same economic system that it had during the 12th–14th centuries with a large production of metallurgy (fargues, a system similar to Farga Catalana) and with the introduction of tobacco circa 1692 and import trade. In 1371, and 1448, the co-princes ratified the fair of Andorra la Vella, the most important annual national festival commercially ever since. The country had a unique and experienced guild of weavers, Confraria de Paraires i Teixidors, in Escaldes-Engordany. Founded in 1604, it took advantage of the local thermal waters. By this time, the country was characterized by the social system of prohoms (wealthy society) and casalers (rest of the population with smaller economic acquisition), deriving from the tradition of pubilla and hereu. Three centuries after its foundation, the Consell de la Terra located its headquarters and the Tribunal de Corts in Casa de la Vall in 1702. The manor house built in 1580 served as a noble fortress of the Busquets family. Inside the parliament was placed the Closet of the six keys (Armari de les sis claus), representative of each Andorran parish, where the Andorran constitution and other documents and laws were later kept. In both the Reapers' War and the War of the Spanish Succession, the Andorran people (while professing to be a neutral country) supported the Catalans who saw their rights reduced in 1716. The reaction was the promotion of Catalan writings in Andorra, with cultural works such as the Book of Privileges (Llibre de Privilegis de 1674), Manual Digest (1748) by Antoni Fiter i Rossell or the Polità andorrà (1763) by Antoni Puig. 19th century: the New Reform and the Andorran Question After the French Revolution, Napoleon I reestablished the Co-Principate in 1809 and removed the French medieval title. In 1812–1813, the First French Empire annexed Catalonia during the Peninsular War () and divided the region into four départements, with Andorra as a part of the district of Puigcerdà. In 1814, an imperial decree reestablished the independence and economy of Andorra. During this period, Andorra's late medieval institutions and rural culture remained largely unchanged. In 1866, the syndic Guillem d'Areny-Plandolit led the reformist group in a Council General of 24 members elected by suffrage limited to heads of families. The Council General replaced the aristocratic oligarchy that previously ruled the state. The New Reform () began after ratification by both Co-Princes and established the basis of the constitution and symbolssuch as the tricolour flagof Andorra. A new service economy arose as a demand of the valley inhabitants and began to build infrastructure such as hotels, spa resorts, roads and telegraph lines. The authorities of the Co-Princes banned casinos and betting houses throughout the country. The ban resulted in an economic conflict and the Revolution of 1881, which began when revolutionaries assaulted the house of the syndic on 8 December 1880, and established the Provisional Revolutionary Council led by Joan Pla i Calvo and Pere Baró i Mas. The Provisional Revolutionary Council allowed for the construction of casinos and spas by foreign companies. From 7 to 9 June 1881, the loyalists of Canillo and Encamp reconquered the parishes of Ordino and La Massana by establishing contact with the revolutionary forces in Escaldes-Engordany. After a day of combat the Treaty of the Bridge of Escalls was signed on 10 June. The council was replaced and new elections were held. The economic situation worsened, as the populace was divided over the  – the "Andorran Question" in relation to the Eastern Question. The struggles continued between pro-bishops, pro-French, and nationalists based on the troubles of Canillo in 1882 and 1885. Andorra participated in the cultural movement of the Catalan Renaixença. Between 1882 and 1887, the first academic schools were formed where trilingualism coexisted with the official language, Catalan. Romantic authors from France and Spain reported the awakening of the national consciousness of the country. Jacint Verdaguer lived in Ordino during the 1880s where he wrote and shared works related to the Renaixença with writer and photographer, Joaquim de Riba. In 1848, Fromental Halévy had premiered the opera Le Val d'Andorre to great success in Europe, where the national consciousness of the valleys was exposed in the romantic work during the Peninsular War. 20th and 21st century: Modernisation of the country and the Constitutional Andorra In 1933, France occupied Andorra following social unrest which occurred before elections due to the Revolution of 1933 and the FHASA strikes (Vagues de FHASA); the revolt led by Joves Andorrans (a labour union group related to the Spanish CNT and FAI) called for political reforms, the universal suffrage vote of all Andorrans and acted in defense of the rights of local and foreign workers during the construction of FHASA's hydroelectric power station in Encamp. On 5 April 1933 Joves Andorrans seized the Andorran Parliament. These actions were preceded by the arrival of Colonel René-Jules Baulard with 50 gendarmes and the mobilization of 200 local militias or sometent led by the Síndic Francesc Cairat. On 6 July 1934, adventurer and nobleman Boris Skossyreff, with his promise of freedoms and modernization of the country and wealth through the establishment of a tax haven and foreign investments, received the support of the members of the General Council to proclaim himself the sovereign of Andorra. On 8 July 1934 Boris issued a proclamation in Urgell, declaring himself Boris I, King of Andorra, simultaneously declaring war on the Bishop of Urgell and approving the King's constitution on 10 July. He was arrested by the Co-Prince and Bishop Justí Guitart i Vilardebó and their authorities on 20 July and ultimately expelled from Spain. From 1936 until 1940, a French military detachment of Garde Mobile led by well-known Colonel René-Jules Baulard was garrisoned in Andorra to secure the principality against disruption from the Spanish Civil War and Francoist Spain and also face the rise of Republicanism in the aftermath of the 1933 Revolution. During the Spanish Civil War, the inhabitants of Andorra welcomed refugees from both sides, and many of them settled permanently in the country thus contributing to the subsequent economic boom and the entry into the capitalist era of Andorra. Francoist troops reached the Andorran border in the later stages of the war. During World War II, Andorra remained neutral and was an important smuggling route between Vichy France and Francoist Spain, two fascist states. Many Andorrans criticized the passivity of the General Council for impeding both the entry and expulsion of foreigners and refugees, committing economic crimes, reducing the rights of citizens and sympathy with Francoism. General Council members justified the council's political and diplomatic actions as necessary for Andorra's survival and the protection of its sovereignty. Andorra was relatively unscathed by the two world wars and the Spanish Civil War. Certain groups formed to help victims of oppression in Nazi-occupied countries, while participating in smuggling to help Andorra survive. Among the most prominent was the Hostal Palanques Evasion Network Command, which, in contact with the British Mi6, helped almost 400 fugitives, among whom were Allied military personnel. The Command remained active between 1941 and 1944, although there were struggles with pro-Axis informers and Gestapo agents in Andorra. In the capital city there was a smuggling black market of propaganda, culture and cinematic art not favorable to totalitarian regimes, promulgated in such places as the Hotel Mirador or the Casino Hotel, as a meeting place for people of ideologies close to Andorran and Spanish Republicanism and Free France. The network was maintained after the war, when film societies were formed, where movies, music and books censored in Franco's Spain were imported, becoming an anti-censorship attraction for the Catalan or foreign public even within Andorra. Andorran Group (Agrupament Andorrà), an anti-fascist organization linked to the Occitanie's French Resistance, accused the French representative (veguer) of collaboration with Nazism. The Andorran opening to the capitalist economy resulted in two axes: mass tourism and the country's tax exemption. The first steps toward the capitalist boom date from the 1930s, with the construction of FHASA and the creation of professional banking with Banc Agrícol (1930) and Crèdit Andorrà (1949), later with Banca Mora (1952), Banca Cassany (1958) and SOBANCA (1960). Shortly after activities such as skiing and shopping become a tourist attraction, with the inauguration of ski resorts and cultural entities in the late 1930s. All in all, a renovated hotel industry has developed. In April 1968 a social health insurance system was created (CASS). The Andorran government necessarily involved planning, projection and forecasts for the future: with the official visit of the French co-prince Charles de Gaulle in 1967 and 1969, it was given approval for the economic boom and national demands within the framework of human rights and international openness. Andorra lived an era commonly known as "Andorran dream" (in relation to the American dream) along with the Trente Glorieuses: the mass culture rooted the country experiencing radical changes in the economy and culture. Proof of this was Ràdio Andorra, the top musical radio station in Europe in this period, with guests and speakers of great importance promoting musical hits of chanson française, swing, rhythm & blues, jazz, rock and roll and American country music. During this period Andorra achieved a GDP per capita and a life expectancy higher than the most standard countries of the current economy. Given its relative isolation, Andorra has existed outside the mainstream of European history, with few ties to countries other than France, Spain and Portugal. But in recent times its thriving tourist industry along with developments in transport and communications have removed the country from its isolation. Since 1976 the country has seen the need to reform Andorran institutions due to anachronisms in sovereignty, human rights and the balance of powers as well as the need to adapt legislation to modern demands. In 1982, a first separation of powers took place when instituting the Govern d'Andorra, under the name of Executive Board (Consell Executiu), chaired by the first prime minister Òscar Ribas Reig with the co-princes' approval. In 1989, the Principality signed an agreement with the European Economic Community to regularize trade relations. Its political system was modernized in 1993 after the Andorran constitutional referendum, when the constitution was drafted by the co-princes and the General Council and approved on 14 March by 74.2% of voters, with a 76% turnout. The first elections under the new constitution were held later in the year. The same year, Andorra became a member of the United Nations and the Council of Europe. Andorra formalized diplomatic relations with the United States in 1996, participating in the 51st UN General Assembly. First General Syndic Marc Forné took part on a speech in Catalan in the General Assembly to defend the reform of the organization, and after three days he took part in the parliamentary assembly of the Council of Europe to defend Andorra's linguistic rights and economy. In 2006, a monetary agreement with the European Union was formalized that allows Andorra to use the euro in an official way, as well as coin its own euro currency. Politics Andorra is a parliamentary co-principality with the president of France and the Catholic bishop of Urgell (Catalonia, Spain) as co-princes. This peculiarity makes the president of France, in his capacity as prince of Andorra, an elected monarch, although he is not elected by a popular vote of the Andorran people. The politics of Andorra take place in a framework of a parliamentary representative democracy with a unicameral legislature, and of a pluriform multi-party system. The head of government is the prime minister. The current head of government is Xavier Espot Zamora of the Democrats for Andorra (DA). Executive power is exercised by the government. Legislative power is vested in both government and parliament. The Parliament of Andorra is known as the General Council. The General Council consists of between 28 and 42 councillors. The councillors serve for four-year terms, and elections are held between the 30th and 40th days following the dissolution of the previous Council. Half are elected in equal numbers by each of the seven administrative parishes, and the other half of the councillors are elected in a single national constituency. Fifteen days after the election, the councillors hold their inauguration. During this session, the Syndic General, who is the head of the General Council, and the Subsyndic General, his assistant, are elected. Eight days later, the Council convenes once more. During this session the head of government is chosen from among the councillors. Candidates can be proposed by a minimum of one-fifth of the councillors. The Council then elects the candidate with the absolute majority of votes to be head of government. The Syndic General then notifies the co-princes, who in turn appoint the elected candidate as the head of government of Andorra. The General Council is also responsible for proposing and passing laws. Bills may be presented to the council as Private Members' Bills by three of the local Parish Councils jointly or by at least one tenth of the citizens of Andorra. The council also approves the annual budget of the principality. The government must submit the proposed budget for parliamentary approval at least two months before the previous budget expires. If the budget is not approved by the first day of the next year, the previous budget is extended until a new one is approved. Once any bill is approved, the Syndic General is responsible for presenting it to the Co-Princes so that they may sign and enact it. If the head of government is not satisfied with the council, he may request that the co-princes dissolve the council and order new elections. In turn, the councillors have the power to remove the head of government from office. After a motion of censure is approved by at least one-fifth of the councillors, the council will vote and if it receives the absolute majority of votes, the head of government is removed. Law and criminal justice The judiciary is composed of the Magistrates Court, the Criminal Law Court, the High Court of Andorra, and the Constitutional Court. The High Court of Justice is composed of five judges: one appointed by the head of government, one each by the co-princes, one by the Syndic General, and one by the judges and magistrates. It is presided over by the member appointed by the Syndic General and the judges hold office for six-year terms. The magistrates and judges are appointed by the High Court, as is the president of the Criminal Law Court. The High Court also appoints members of the Office of the Attorney General. The Constitutional Court is responsible for interpreting the Constitution and reviewing all appeals of unconstitutionality against laws and treaties. It is composed of four judges, one appointed by each of the co-princes and two by the General Council. They serve eight-year terms. The Court is presided over by one of the judges on a two-year rotation so that each judge at one point will preside over the Court. Foreign relations, defence and security Andorra does not have its own armed forces, although there is a small ceremonial army. Responsibility for defending the nation rests primarily with France and Spain. However, in case of emergencies or natural disasters, the Sometent (an alarm) is called and all able-bodied men between 21 and 60 of Andorran nationality must serve. This is why all Andorrans, and especially the head of each house (usually the eldest able-bodied man of a house) should, by law, keep a rifle, even though the law also states that the police will offer a firearm in case of need. Andorra is a full member of the United Nations (UN), the Organization for Security and Co-operation in Europe (OSCE), and has a special agreement with the European Union (EU), it also has observer status at the World Trade Organization (WTO). On 16 October 2020, Andorra became the 190th member of the International Monetary Fund (IMF), during the COVID-19 pandemic. Military Andorra has a small army, which has historically been raised or reconstituted at various dates, but has never in modern times amounted to a standing army. The basic principle of Andorran defence is that all able-bodied men are available to fight if called upon by the sounding of the Sometent. Being a landlocked country, Andorra has no navy. Before World War I, Andorra maintained an armed force of about 600 part-time militiamen under the supervision of a Captain (Capità or Cap de Sometent) and a Lieutenant (Desener or Lloctinent del Capità). This body was not liable for service outside the principality and was commanded by two officials (veguers) appointed by France and the Bishop of Urgell. In the modern era, the army has consisted of a very small body of volunteers willing to undertake ceremonial duties. Uniforms and weaponry were handed down from generation to generation within families and communities. The army's role in internal security was largely taken over by the formation of the Police Corps of Andorra in 1931. Brief civil disorder associated with the elections of 1933 led to assistance being sought from the French National Gendarmerie, with a detachment resident in Andorra for two months under the command of René-Jules Baulard. The Andorran Police was reformed in the following year, with eleven soldiers appointed to supervisory roles. The force consisted of six Corporals, one for each parish (although there are currently seven parishes, there were only six until 1978), plus four junior staff officers to co-ordinate action, and a commander with the rank of major. It was the responsibility of the six corporals, each in his own parish, to be able to raise a fighting force from among the able-bodied men of the parish. Today a small, twelve-man ceremonial unit remains the only permanent section of the Sometent, but all able-bodied men remain technically available for military service, with a requirement for each family to have access to a firearm. A shotgun per household is unregulated. Rifles and pistols require a license. The army has not fought for more than 700 years, and its main responsibility is to present the flag of Andorra at official ceremonial functions. According to Marc Forné Molné, Andorra's military budget is strictly from voluntary donations, and the availability of full-time volunteers. In more recent times there has only been a general emergency call to the popular army of Sometent during the floods of 1982 in the Catalan Pyrenees, where 12 citizens perished in Andorra, to help the population and establish a public order along with the Local Police units. Police Corps Andorra maintains a small but modern and well-equipped internal police force, with around 240 police officers supported by civilian assistants. The principal services supplied by the corps are uniformed community policing, criminal detection, border control, and traffic policing. There are also small specialist units including police dogs, mountain rescue, and a bomb disposal team. GIPA The Grup d'Intervenció Policia d'Andorra (GIPA) is a small special forces unit trained in counter-terrorism, and hostage recovery tasks. Although it is the closest in style to an active military force, it is part of the Police Corps, and not the army. As terrorist and hostage situations are a rare threat to the country, the GIPA is commonly assigned to prisoner escort duties, and at other times to routine policing. Fire brigade The Andorran Fire Brigade, with headquarters at Santa Coloma, operates from four modern fire stations, and has a staff of around 120 firefighters. The service is equipped with 16 heavy appliances (fire tenders, turntable ladders, and specialist four-wheel drive vehicles), four light support vehicles (cars and vans) and four ambulances. Historically, the families of the six ancient parishes of Andorra maintained local arrangements to assist each other in fighting fires. The first fire pump purchased by the government was acquired in 1943. Serious fires which lasted for two days in December 1959 led to calls for a permanent fire service, and the Andorran Fire Brigade was formed on 21 April 1961. The fire service maintains full-time cover with five fire crews on duty at any time: two at the brigade's headquarters in Santa Coloma, and one crew at each of the other three fire stations. Geography Parishes Andorra consists of seven parishes: Andorra la Vella Canillo Encamp Escaldes-Engordany La Massana Ordino Sant Julià de Lòria Physical geography Due to its location in the eastern Pyrenees mountain range, Andorra consists predominantly of rugged mountains, the highest being the Coma Pedrosa at , and the average elevation of Andorra is . These are dissected by three narrow valleys in a Y shape that combine into one as the main stream, the Gran Valira river, leaves the country for Spain (at Andorra's lowest point of ). Andorra's land area is . Environment Phytogeographically, Andorra belongs to the Atlantic European province of the Circumboreal Region within the Boreal Kingdom. According to the WWF, the territory of Andorra belongs to the ecoregion of Pyrenees conifer and mixed forests. Andorra had a 2018 Forest Landscape Integrity Index mean score of 4.45/10, ranking it 127th globally out of 172 countries. Important Bird Area The whole country has been recognised as a single Important Bird Area (IBA) by BirdLife International, because it is important for forest and mountain birds and supports populations of red-billed choughs, citril finches and rock buntings. Climate Andorra has alpine, continental and oceanic climates, depending on altitude. Its higher elevation means there is, on average, more snow in winter and it is slightly cooler in summer. The diversity of landmarks, the different orientation of the valleys and the irregularity relief typical of the Mediterranean climates make the country have a great diversity of microclimates that hinder the general dominance of the high mountain climate. The great differences of altitude in the minimum and maximum points, together with the influence of a Mediterranean climate, develop the climate of the Andorran Pyrenees. When in precipitation, a global model characterized by convective and abundant rains can be defined during spring and summer, which can last until autumn (May, June and August are usually the rainiest months). In winter, however, it is less rainy, except in the highlands, subject to the influence of fronts from the Atlantic, which explains the great amount of snowfall in the Andorran mountains. The temperature regime is characterized, broadly, by a temperate summer and a long and cold winter, in accordance with the mountainous condition of the Principality. Economy Tourism, the mainstay of Andorra's tiny, well-to-do economy, accounts for roughly 80% of GDP. An estimated 10.2 million tourists visit annually, attracted by Andorra's duty-free status and by its summer and winter resorts. One of the main sources of income in Andorra is tourism from ski resorts which total over of ski ground. The sport brings in over 7 million visitors annually and an estimated 340 million euros per year, sustaining 2,000 direct and 10,000 indirect jobs at present since 2007. The banking sector, with its tax haven status, also contributes substantially to the economy with revenues raised exclusively through import tariffs (the financial and insurance sector accounts for approximately 19% of GDP). However, during the European sovereign-debt crisis of the 21st century, the tourist industry suffered a decline, partly caused by a drop in the prices of goods in Spain, undercutting duty-free shopping and increasing unemployment. On 1 January 2012, a business tax of 10% was introduced, followed by a sales tax of 2% a year later, which raised just over 14 million euros in its first quarter. Agricultural production is limited; only 1.7% of the land is arable, and most food has to be imported. Some tobacco is grown locally. The principal livestock activity is domestic sheep raising. Manufacturing output consists mainly of cigarettes, cigars, and furniture. Andorra's natural resources include hydroelectric power, mineral water, timber, iron ore, and lead. Andorra is not a member of the European Union, but enjoys a special relationship with it, such as being treated as an EU member for trade in manufactured goods (no tariffs) and as a non-EU member for agricultural products. Andorra lacked a currency of its own and used both the French franc and the Spanish peseta in banking transactions until 31 December 1999, when both currencies were replaced by the EU's single currency, the euro. Coins and notes of both the franc and the peseta remained legal tender in Andorra until 31 December 2002. Andorra negotiated to issue its own euro coins, beginning in 2014. Andorra has historically had one of the world's lowest unemployment rates. In 2019, it stood at 2%. On 31 May 2013, it was announced that Andorra intended to legislate for the introduction of an income tax by the end of June, against a background of increasing dissatisfaction with the existence of tax havens among EU members. The announcement was made following a meeting in Paris between the Head of Government Antoni Martí and the French President and Prince of Andorra François Hollande. Hollande welcomed the move as part of a process of Andorra "bringing its taxation in line with international standards". By the mid-2010s, the financial system comprised five banking groups, one specialised credit entity, eight investment undertaking management entities, three asset management companies, and 29 insurance companies, 14 of which are branches of foreign insurance companies authorised to operate in the principality. Demographics Population The population of Andorra is estimated at (). The Andorrans are a Romance ethnic group of originally Catalan descent. The population has grown from 5,000 in 1900. Two-thirds of residents lack Andorran nationality and do not have the right to vote in communal elections. Moreover, they are not allowed to be elected as prime minister or to own more than 33% of the capital stock of a privately held company. Languages The historic and official language is Catalan, a Romance language. The Andorran government encourages the use of Catalan. It funds a Commission for Catalan Toponymy in Andorra (Catalan: ), and provides free Catalan classes to assist immigrants. Andorran television and radio stations use Catalan. Because of immigration, historical links, and close geographic proximity, Spanish, Portuguese and French are commonly spoken. Most Andorran residents can speak one or more of these, in addition to Catalan. English is less commonly spoken among the general population, though it is understood to varying degrees in the major tourist resorts. Andorra is one of only four European countries (together with France, Monaco, and Turkey) that have never signed the Council of Europe Framework Convention on National Minorities. According to mother tongue percentage statistics by the Andorran Government released in 2018 the principality has the following: Religion The population of Andorra is predominantly (88.2%) Catholic. Their patron saint is Our Lady of Meritxell. There are also members of various Protestant denominations. There are also small numbers of Muslims, Hindus, and Bahá'ís, and roughly 100 Jews. (See History of the Jews in Andorra.) Largest cities Education Schools Children between the ages of 6 and 16 are required by law to have full-time education. Education up to secondary level is provided free of charge by the government. There are three systems of school, Andorran, French and Spanish, which use Catalan, French and Spanish languages respectively, as the main language of instruction. Parents may choose which system their children attend. All schools are built and maintained by Andorran authorities, but teachers in the French and Spanish schools are paid for the most part by France and Spain. 39% of Andorran children attend Andorran schools, 33% attend French schools, and 28% Spanish schools. University of Andorra The Universitat d'Andorra (UdA) is the state public university and is the only university in Andorra. It was established in 1997. The university provides first-level degrees in nursing, computer science, business administration, and educational sciences, in addition to higher professional education courses. The only two graduate schools in Andorra are the Nursing School and the School of Computer Science, the latter having a PhD programme. Virtual Studies Centre The geographical complexity of the country as well as the small number of students prevents the University of Andorra from developing a full academic programme, and it serves principally as a centre for virtual studies, connected to Spanish and French universities. The Virtual Studies Centre (Centre d'Estudis Virtuals) at the university runs approximately 20 different academic degrees at both undergraduate and postgraduate levels in fields including tourism, law, Catalan philology, humanities, psychology, political sciences, audiovisual communication, telecommunications engineering, and East Asia studies. The centre also runs various postgraduate programmes and continuing-education courses for professionals. Transport Until the 20th century, Andorra had very limited transport links to the outside world, and development of the country was affected by its physical isolation. Even now, the nearest major airports at Toulouse and Barcelona are both three hours' drive from Andorra. Andorra has a road network of , of which is unpaved. The two main roads out of Andorra la Vella are the CG-1 to the Spanish border near Sant Julià de Lòria, and the CG-2 to the French border via the Envalira Tunnel near El Pas de la Casa. Bus services cover all metropolitan areas and many rural communities, with services on most major routes running half-hourly or more frequently during peak travel times. There are frequent long-distance bus services from Andorra to Barcelona and Toulouse, plus a daily tour from the former city. Bus services mostly are run by private companies, but some local ones are operated by the government. There are no airports for fixed-wing aircraft within Andorra's borders but there are, however, heliports in La Massana (Camí Heliport), Arinsal and Escaldes-Engordany with commercial helicopter services and an airport located in the neighbouring Spanish comarca of Alt Urgell, south of the Andorran-Spanish border. Since July 2015, Andorra–La Seu d'Urgell Airport has operated commercial flights to Madrid and Palma de Mallorca, and is the main hub for Air Andorra and Andorra Airlines. As of 11 July 2018, there are no regular commercial flights at the airport. Nearby airports located in Spain and France provide access to international flights for the principality. The nearest airports are at Perpignan, France ( from Andorra) and Lleida, Spain ( from Andorra). The largest nearby airports are at Toulouse, France ( from Andorra) and Barcelona, Spain ( from Andorra). There are hourly bus services from both Barcelona and Toulouse airports to Andorra. The nearest railway station is Andorre-L'Hospitalet station east of Andorra which is on the -gauge line from Latour-de-Carol () southeast of Andorra, to Toulouse and on to Paris by the French high-speed trains. This line is operated by the SNCF. Latour-de-Carol has a scenic trainline to Villefranche-de-Conflent, as well as the SNCF's gauge line connecting to Perpignan, and the Renfe's -gauge line to Barcelona. There are also direct Intercités de Nuit trains between L'Hospitalet-près-l'Andorre and Paris on certain dates. Media and telecommunications In Andorra, mobile and fixed telephone and internet services are operated exclusively by the Andorran national telecommunications company, Andorra Telecom. The same company also manages the technical infrastructure for national broadcasting of digital television and radio. In 2010, Andorra became the first country to provide a direct optical fiber link to all homes (FTTH) and businesses. The first commercial radio station to broadcast was Radio Andorra, which was active from 1939 to 1981. On 12 October 1989, the General Council established radio and television as essential public services creating and managing the entity ORTA, becoming on 13 April 2000, in the public company Ràdio i Televisió d'Andorra (RTVA). In 1990, the public radio was founded on the Radio Nacional d'Andorra. As an autochthonous television channel, there is only the national public television network Andorra Televisió, created in 1995. Additional TV and radio stations from Spain and France are available via digital terrestrial television and IPTV. There are three national newspapers, Diari d'Andorra, El Periòdic d'Andorra, and Bondia as well as several local newspapers. The history of the Andorran press begins in the period between 1917 and 1937 with the appearance of several periodicals papers such as Les Valls d'Andorra (1917), Nova Andorra (1932) and Andorra Agrícola (1933). In 1974, the Poble Andorrà became the first regular newspaper in Andorra. There is also an amateur radio society and news agency ANA with independent management. Culture Andorra is home to folk dances like the contrapàs and marratxa, which survive in Sant Julià de Lòria especially. Andorran folk music has similarities to the music of its neighbours, but is especially Catalan in character, especially in the presence of dances such as the sardana. Other Andorran folk dances include contrapàs in Andorra la Vella and Saint Anne's dance in Escaldes-Engordany. Andorra's national holiday is Our Lady of Meritxell Day, 8 September. Among the more important festivals and traditions are the Canólich Gathering in May, the Roser d'Ordino in July, the Meritxell Day (National Day of Andorra), the Andorra la Vella Fair, the Sant Jordi Day, the Santa Llúcia Fair, the Festivity from La Candelera to Canillo, the Carnival of Encamp, the sung of caramelles, the Festivity of Sant Esteve and the Festa del Poble. Andorra participated regularly in the Eurovision Song Contest between 2004 and 2009, being the only participating country presenting songs in Catalan. In popular folklore, the best-known Andorran legends are the legend of Charlemagne, according to which this Frankish King would have founded the country, the White Lady of Auvinyà, the Buner d'Ordino, the legend of Engolasters Lake and the legend of Our Lady of Meritxell. Andorran gastronomy is mainly Catalan, although it has also adopted other elements of French and Italian cuisines. The cuisine of the country has similar characteristics with the neighbours of the Cerdanya and the Alt Urgell, with whom it has a strong cultural ties. Andorra's cuisine is marked by its nature as mountain valleys. Typical dishes of the country are the quince all-i-oli, the duck with winter pear, the lamb in the oven with nuts, pork civet, the massegada cake, the escarole with pear trees, duck confit and mushrooms, escudella, spinach with raisins and pine nuts, jelly marmalade, stuffed murgues (mushrooms) with pork, dandelion salad and the Andorran trout of river. To drink, the mulled wine and beer are also popular. Some of the dishes are very common in the mountainous regions of Catalonia, such as trinxat, embotits, cooked snails, rice with mushrooms, mountain rice and mató. Pre-Romanesque and Romanesque art are one of the most important artistic manifestations and characteristics of the Principality. The Romanesque one allows to know the formation of the parochial communities, the relations of (social and political) power and the national culture. There are a total of forty Romanesque churches that stand out as being small austere ornamentation constructions, as well as bridges, fortresses and manor houses of the same period. Summer solstice fire festivals in the Pyrenees was included as UNESCO Intangible cultural heritage in 2015. Also the Madriu-Perafita-Claror Valley became Andorra's first, and to date its only, UNESCO World Heritage Site in 2004, with a small extension in 2006. Sports Andorra is famous for the practice of winter sports. Andorra has the largest territory of ski slopes in the Pyrenees (3100 hectares and about 350 km of slopes) and two ski resorts. Grandvalira is the largest and most popular resort. Other popular sports played in Andorra include football, rugby union, basketball, and roller hockey. For roller hockey, Andorra usually plays in CERH Euro Cup and in FIRS Roller Hockey World Cup. In 2011, Andorra was the host country to the 2011 European League Final Eight. The country is represented in association football by the Andorra national football team. The team gained its first competitive win in a European Championship qualifier on 11 October 2019, against Moldova. Football is governed in Andorra by the Andorran Football Federation – founded in 1994, it organizes the national competitions of association football (Primera Divisió, Copa Constitució and Supercopa) and futsal. Andorra was admitted to UEFA and FIFA in the same year, 1996. FC Andorra, a club based in Andorra la Vella founded in 1942, compete in the Spanish football league system. Rugby is a traditional sport in Andorra, mainly influenced by the popularity in southern France. The Andorra national rugby union team, nicknamed Els Isards, plays on the international stage in rugby union and rugby sevens. VPC Andorra XV is a rugby team based in Andorra la Vella, which actually plays in the French championship. Basketball popularity has increased in the country since the 1990s, when the Andorran team BC Andorra played in the top league of Spain (Liga ACB). After 18 years the club returned to the top league in 2014. Other sports practised in Andorra include cycling, volleyball, judo, Australian Rules football, handball, swimming, gymnastics, tennis, and motorsports. In 2012, Andorra raised its first national cricket team and played a home match against the Dutch Fellowship of Fairly Odd Places Cricket Club, the first match played in the history of Andorra at an altitude of . Andorra first participated at the Olympic Games in 1976. The country has appeared in every Winter Olympic Games since 1976. Andorra competes in the Games of the Small States of Europe, being twice the host country, in 1991 and 2005. As one of the Catalan Countries, Andorra is home to a team of castellers, or Catalan human tower builders. The , based in the town of Santa Coloma d'Andorra, are recognized by the , the governing body of castells. See also Index of Andorra-related articles Outline of Andorra Bibliography of Andorra Explanatory notes Citations General bibliography Further reading Berthet, Elie, The Valley of Andorra. Bristol, UK: J. W. Arrowsmith, 1886. Butler, Michael, Frisch: Andorra. Carrick, Noel, Let's Visit Andorra. London: Macmillan, 1988. Deane, Shirley, The Road to Andorra. London: John Murray, 1960. Duursma, John C., Fragmentation and the International Relations of Micro-States. Cambridge University Press, 1996. Jenner, Paul & Christine Smith, Landscapes of the Pyrenees. London: Sunflower Books, 1990. Johnson, Virginia W., Two Quaint Republics: Andorra and San Marino. Leary, Lewis Gaston, Andorra the Hidden Republic. London: T. Fisher Unwin, 1912. Mackintosh, May, Assignment in Andorra. London: Pan, 1976. Murray, James Erskine, A Summer in the Pyrenees. London: John Macrone, 1837. Newman, Bernard, Round About Andorra. London: George Allen & Unwin, 1928. Piesold, Werner, Andorra. Reichert, Thomas, Andorra: A Country Survey. Nuremberg, 1986. Spender, Harold & H. Llewellyn Smith, Through the High Pyrenees. London: A. D. Innes, 1898. Vila, Linda Armengol, Approach to the History of Andorra. Perpignan: Institut d'Estudis Andorrans, 1989. Vilajoana, Ricard Fiter & M. Marti Rebols, All Andorra. Barcelona: Escudo de Oro, 1979. Waagenaar, Sam, The Little Five. London: Andre Deutsch, 1960. External links Govern d'Andorra Official governmental site Andorra. The World Factbook. Central Intelligence Agency. Portals to the World from the United States Library of Congress Andorra from UCB Libraries GovPubs Andorra from the BBC News Andorra – Guía, turismo y de viajes History of Andorra: Primary Documents from EuroDocs A New Path for Andorra – slideshow by The New York Times 1278 establishments in Europe Catalan Countries Christian states Countries in Europe Diarchies Duty-free zones of Europe French-speaking countries and territories Iberian Peninsula Important Bird Areas of Andorra Landlocked countries Member states of the Council of Europe Member states of the Organisation internationale de la Francophonie Current member states of the United Nations Monarchies of Europe Prince-bishoprics Principalities Pyrenees Southern European countries Southwestern European countries Spanish-speaking countries and territories Special economic zones States and territories established in 1278

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

612

https://en.wikipedia.org/wiki/Arithmetic%20mean

Arithmetic mean

In mathematics and statistics, the arithmetic mean ( ) or arithmetic average, or simply just the mean or the average (when the context is clear), is the sum of a collection of numbers divided by the count of numbers in the collection. The collection is often a set of results of an experiment or an observational study, or frequently a set of results from a survey. The term "arithmetic mean" is preferred in some contexts in mathematics and statistics, because it helps distinguish it from other means, such as the geometric mean and the harmonic mean. In addition to mathematics and statistics, the arithmetic mean is used frequently in many diverse fields such as economics, anthropology and history, and it is used in almost every academic field to some extent. For example, per capita income is the arithmetic average income of a nation's population. While the arithmetic mean is often used to report central tendencies, it is not a robust statistic, meaning that it is greatly influenced by outliers (values that are very much larger or smaller than most of the values). For skewed distributions, such as the distribution of income for which a few people's incomes are substantially greater than most people's, the arithmetic mean may not coincide with one's notion of "middle", and robust statistics, such as the median, may provide better description of central tendency. Definition Given a data set , the arithmetic mean (or mean or average), denoted (read bar), is the mean of the values . The arithmetic mean is the most commonly used and readily understood measure of central tendency in a data set. In statistics, the term average refers to any of the measures of central tendency. The arithmetic mean of a set of observed data is defined as being equal to the sum of the numerical values of each and every observation, divided by the total number of observations. Symbolically, if we have a data set consisting of the values , then the arithmetic mean is defined by the formula: (for an explanation of the summation operator, see summation.) For example, consider the monthly salary of 10 employees of a firm: 2500, 2700, 2400, 2300, 2550, 2650, 2750, 2450, 2600, 2400. The arithmetic mean is If the data set is a statistical population (i.e., consists of every possible observation and not just a subset of them), then the mean of that population is called the population mean, and denoted by the Greek letter . If the data set is a statistical sample (a subset of the population), then we call the statistic resulting from this calculation a sample mean (which for a data set is denoted as ). The arithmetic mean can be similarly defined for vectors in multiple dimension, not only scalar values; this is often referred to as a centroid. More generally, because the arithmetic mean is a convex combination (coefficients sum to 1), it can be defined on a convex space, not only a vector space. Motivating properties The arithmetic mean has several properties that make it useful, especially as a measure of central tendency. These include: If numbers have mean , then . Since is the distance from a given number to the mean, one way to interpret this property is as saying that the numbers to the left of the mean are balanced by the numbers to the right of the mean. The mean is the only single number for which the residuals (deviations from the estimate) sum to zero. If it is required to use a single number as a "typical" value for a set of known numbers , then the arithmetic mean of the numbers does this best, in the sense of minimizing the sum of squared deviations from the typical value: the sum of . (It follows that the sample mean is also the best single predictor in the sense of having the lowest root mean squared error.) If the arithmetic mean of a population of numbers is desired, then the estimate of it that is unbiased is the arithmetic mean of a sample drawn from the population. Contrast with median The arithmetic mean may be contrasted with the median. The median is defined such that no more than half the values are larger than, and no more than half are smaller than, the median. If elements in the data increase arithmetically, when placed in some order, then the median and arithmetic average are equal. For example, consider the data sample . The average is , as is the median. However, when we consider a sample that cannot be arranged so as to increase arithmetically, such as , the median and arithmetic average can differ significantly. In this case, the arithmetic average is 6.2, while the median is 4. In general, the average value can vary significantly from most values in the sample, and can be larger or smaller than most of them. There are applications of this phenomenon in many fields. For example, since the 1980s, the median income in the United States has increased more slowly than the arithmetic average of income. Generalizations Weighted average A weighted average, or weighted mean, is an average in which some data points count more heavily than others, in that they are given more weight in the calculation. For example, the arithmetic mean of and is , or equivalently . In contrast, a weighted mean in which the first number receives, for example, twice as much weight as the second (perhaps because it is assumed to appear twice as often in the general population from which these numbers were sampled) would be calculated as . Here the weights, which necessarily sum to the value one, are and , the former being twice the latter. The arithmetic mean (sometimes called the "unweighted average" or "equally weighted average") can be interpreted as a special case of a weighted average in which all the weights are equal to each other (equal to in the above example, and equal to in a situation with numbers being averaged). Continuous probability distributions If a numerical property, and any sample of data from it, could take on any value from a continuous range, instead of, for example, just integers, then the probability of a number falling into some range of possible values can be described by integrating a continuous probability distribution across this range, even when the naive probability for a sample number taking one certain value from infinitely many is zero. The analog of a weighted average in this context, in which there are an infinite number of possibilities for the precise value of the variable in each range, is called the mean of the probability distribution. A most widely encountered probability distribution is called the normal distribution; it has the property that all measures of its central tendency, including not just the mean but also the aforementioned median and the mode (the three M's), are equal to each other. This equality does not hold for other probability distributions, as illustrated for the log-normal distribution here. Angles Particular care must be taken when using cyclic data, such as phases or angles. Naively taking the arithmetic mean of 1° and 359° yields a result of 180°. This is incorrect for two reasons: Firstly, angle measurements are only defined up to an additive constant of 360° (or 2π, if measuring in radians). Thus one could as easily call these 1° and −1°, or 361° and 719°, since each one of them gives a different average. Secondly, in this situation, 0° (equivalently, 360°) is geometrically a better average value: there is lower dispersion about it (the points are both 1° from it, and 179° from 180°, the putative average). In general application, such an oversight will lead to the average value artificially moving towards the middle of the numerical range. A solution to this problem is to use the optimization formulation (viz., define the mean as the central point: the point about which one has the lowest dispersion), and redefine the difference as a modular distance (i.e., the distance on the circle: so the modular distance between 1° and 359° is 2°, not 358°). Symbols and encoding The arithmetic mean is often denoted by a bar, (a.k.a vinculum or macron), for example as in (read bar). Some software (text processors, web browsers) may not display the x̄ symbol properly. For example, the x̄ symbol in HTML is actually a combination of two codes - the base letter x plus a code for the line above (&#772; or ¯). In some texts, such as pdfs, the x̄ symbol may be replaced by a cent (¢) symbol (Unicode &#162), when copied to text processor such as Microsoft Word. See also Fréchet mean Generalized mean Geometric mean Harmonic mean Inequality of arithmetic and geometric means Mode Sample mean and covariance Standard deviation Standard error of the mean Summary statistics References Further reading External links Calculations and comparisons between arithmetic mean and geometric mean of two numbers Calculate the arithmetic mean of a series of numbers on fxSolver Means

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

630

https://en.wikipedia.org/wiki/Ada

Ada

Ada may refer to: Places Africa Ada Foah or Ada, Ghana, a town Ada (Ghana parliament constituency) Ada, Osun, a town in Osun State, Nigeria Asia Adeh, Urmia, also known as Ada, a village in West Azerbaijan Province Ada, Karaman, a village in Karaman Province, Turkey Australia and New Zealand Ada River (disambiguation), three rivers Europe Ada, Bosnia and Herzegovina, a village Ada, Croatia, a village Ada, Serbia, a town and municipality Ada Ciganlija or Ada, a river island artificially turned into a peninsula in Belgrade, Serbia North America United States Ada, Alabama, an unincorporated community Ada County, Idaho Ada, Kansas, an unincorporated community Ada Township, Michigan Ada, Minnesota, a city Ada Township, Dickey County, North Dakota Ada, Ohio, a village Ada, Oklahoma, a city Ada, Oregon, an unincorporated community Ada Township, Perkins County, South Dakota Ada, West Virginia, an unincorporated community Ada, Wisconsin, an unincorporated community Outer space 523 Ada, an asteroid Film and television Ada TV, a television channel in the Turkish Republic of Northern Cyprus Ada (1961 film), a 1961 film by Daniel Mann Ada (2019 film), a short biopic about Ada Lovelace Ada... A Way of Life, a 2008 Bollywood musical by Tanvir Ahmed Ada (dog actor), a dog that played Colin on the sitcom Spaced Ada, one of the main characters in 1991 movie Armour of God II: Operation Condor Biology Ada (plant), a genus of orchids Adenosine deaminase, an enzyme involved in purine metabolism Ada (protein), an enzyme induced by treatment of bacterial cells Computer science Ada (programming language), programming language based on Pascal Ada (computer virus) Air travel Ada Air, a regional airline based in Tirana, Albania Ada International Airport or Saipan International Airport, Saipan Island, Northern Mariana Islands Aerolínea de Antioquia, a Colombian airline Airline Deregulation Act, a 1978 US bill removing governmental control from commercial aviation Schools Ada, the National College for Digital Skills, a further education college in Tottenham Hale, London Ada High School (Ohio), Ada, Ohio Ada High School (Oklahoma), Ada, Oklahoma People Ada (name), a feminine given name and a surname, including a list of people and fictional characters Ada Lovelace (1815–1852), computer scientist sometimes regarded as the first computer programmer Other uses List of tropical storms named Ada Ada (food), a traditional Kerala delicacy Ada, the cryptocurrency of the Cardano blockchain platform Ada Bridge, Belgrade, Serbia , a cargo vessel built for the London and South Western Railway Ada (ship), a wooden ketch, wrecked near Newcastle, New South Wales, Australia Ada or Ardor: A Family Chronicle, novel by Vladimir Nabokov Dangme language, spoken in Ghana (ISO 639-2 and 639-3 code "ada") Ada Health GmbH, a symptom checker app See also ADA (disambiguation) Ada regulon, an Escherichia coli adaptive response protein Adah (disambiguation) Adha (disambiguation) Ada'a, a woreda in the Oromia Region of Ethiopia Ade (disambiguation) USS Little Ada (1864), a steamer captured by the Union Navy during the American Civil War

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

632

https://en.wikipedia.org/wiki/Aberdeen%20%28disambiguation%29

Aberdeen (disambiguation)

Aberdeen is a city in Scotland, United Kingdom. Aberdeen may also refer to: Places Africa Aberdeen, Sierra Leone Aberdeen, Eastern Cape, South Africa Asia Hong Kong Aberdeen, Hong Kong, an area and town on southwest Hong Kong Island Aberdeen Channel, a channel between Ap Lei Chau (Aberdeen Island) and Nam Long Shan on the Hong Kong Island in Hong Kong Aberdeen Country Park, a country park in Hong Kong Island Aberdeen floating village, at Aberdeen Harbour, containing approximately 600 junks, which house an estimated 6,000 people Aberdeen Harbour, a harbour between Aberdeen, Hong Kong and Ap Lei Chau (Aberdeen Island) Aberdeen Tunnel, a tunnel in Hong Kong Island Aberdeen Tunnel Underground Laboratory, an underground particle physics laboratory in Hong Kong Island Ap Lei Chau or Aberdeen Island, an island of Hong Kong Aberdeen (constituency), a constituency of Southern District Council India Aberdeen Bazaar, a shopping centre in Port Blair, South Andaman Island Sri Lanka Aberdeen Falls, a waterfall in Sri Lanka Australia Aberdeen, New South Wales Aberdeen, South Australia, one of the early townships that merged in 1940 to create the town of Burra Aberdeen, Tasmania, a suburb of the City of Devonport Caribbean Aberdeen, Jamaica, a town in Saint Elizabeth, Jamaica Europe Aberdeen (Parliament of Scotland constituency) Aberdeen (UK Parliament constituency) 1832-1885 Aberdeen Burghs (UK Parliament constituency) 1801-1832 Aberdeen Central (Scottish Parliament constituency) Aberdeen Central (UK Parliament constituency) Aberdeen Donside (Scottish Parliament constituency) County of Aberdeen, a historic county of Scotland whose county town was Aberdeen Old Aberdeen, a part of the city of Aberdeen in Scotland North America Canada Aberdeen, community in the township of Champlain, Prescott and Russell County, Ontario Aberdeen, Abbotsford, a neighbourhood in the City of Abbotsford, British Columbia Aberdeen Centre, a shopping mall in Richmond, British Columbia Aberdeen, Grey County, Ontario Aberdeen, Kamloops, an area in the City of Kamloops, British Columbia Aberdeen Lake (Nunavut), a lake in Kivalliq Region, Nunavut, Canada Aberdeen, Nova Scotia, part of the Municipality of Inverness County, Nova Scotia Aberdeen Parish, New Brunswick Rural Municipality of Aberdeen No. 373, Saskatchewan Aberdeen, Saskatchewan Aberdeen Bay, a bay between southern Baffin Island and north-eastern Hector Island in the Nunavut territory Aberdeen Township, Quebec, until 1960 part of Sheen-Esher-Aberdeen-et-Malakoff, now part of Rapides-des-Joachims, Quebec Aberdeen River, a tributary of rivière aux Castors Noirs in Mauricie, Québec New Aberdeen, Nova Scotia United States Aberdeen, Arkansas Aberdeen, Florida Aberdeen, Georgia Aberdeen, Idaho Aberdeen, Ohio County, Indiana Aberdeen, Porter County, Indiana Aberdeen, Kentucky Aberdeen, Maryland Aberdeen Proving Ground, a United States Army facility located near Aberdeen, Maryland Aberdeen, Massachusetts, a neighborhood of Brighton, Boston Aberdeen, Mississippi Aberdeen Lake (Mississippi), a lake in northeast Mississippi on the Tennessee-Tombigbee Waterway, close to Aberdeen, Mississippi Aberdeen Township, New Jersey Aberdeen, North Carolina Aberdeen Historic District (Aberdeen, North Carolina) Aberdeen, Ohio Aberdeen, South Dakota Aberdeen Historic District (Aberdeen, South Dakota) Aberdeen, Texas Aberdeen (Disputanta, Virginia) Aberdeen Gardens (Hampton, Virginia) Aberdeen, Washington Aberdeen Gardens, Washington Aberdeen, West Virginia Business Abrdn, formerly Standard Life Aberdeen Aberdeen Asset Management Education Aberdeen Business School Aberdeen College, formerly one of the largest further education colleges in Scotland, merged with Banff & Buchan College to form North East Scotland College Aberdeen Grammar School, Aberdeen, Scotland Aberdeen Hall, a university-preparatory school in Kelowna, British Columbia, Canada Aberdeen High School (disambiguation) King's College, Aberdeen University of Aberdeen, a public research university in the city of Aberdeen Entertainment Aberdeen (2000 film), a 2000 Norwegian-British film directed by Hans Petter Moland, starring Stellan Skarsgård and Lena Headey Aberdeen (2014 film), a 2014 Hong Kong film starring Louis Koo Aberdeen (band), an American rock band Aberdeen (song), a song by Cage The Elephant Aberdeen City (band), Boston based indie/alternative rock band Other transportation Aberdeen Airport (disambiguation) Aberdeen Lock and Dam, one of four lock and dam structures on the Tennessee-Tombigbee Waterway Rail Aberdeen, Carolina and Western Railway, a short-line railroad operating in North Carolina Aberdeen and Rockfish Railroad, a short-line railroad operating in North Carolina Aberdeen Corporation Tramways Aberdeen Line (disambiguation) Aberdeen station (disambiguation) Dundee and Perth and Aberdeen Junction Railway, a later name of the Dundee and Perth Railway Shipping Aberdeen Line, a British shipping company founded in 1825 , one of several ships by that name , a sloop of the British Royal Navy that served between 1936 and 1948 , a merchant ship operated during the latter stages of World War II, later commissioned as the USS Altair Sports Aberdeen Dad Vail Regatta, the largest regular intercollegiate rowing event in the United States, named after its sponsor, Aberdeen Asset Management Aberdeen F.C. (disambiguation) Aberdeen GSFP RFC, an amateur rugby union club based in Aberdeen Aberdeen IronBirds, a minor league baseball team affiliated with the Baltimore Orioles Aberdeen L.F.C., a women's football team affiliated with Aberdeen F.C. See also Aberdeen Act Aberdeen Angus, a Scottish breed of small beef cattle Aberdeen Central (disambiguation) Aberdeen Gardens (disambiguation) Aberdeen Historic District (disambiguation) Aberdeen Hospital (disambiguation) Aberdeen Quarry, a granite quarry in Colorado Battle of Aberdeen (disambiguation) Diocese of Aberdeen and Orkney, one of the seven dioceses of the Scottish Episcopal Church Etymology of Aberdeen Marquess of Aberdeen and Temair, a title in the Peerage of the United Kingdom

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

653

https://en.wikipedia.org/wiki/Assistive%20technology

Assistive technology

Assistive technology (AT) is a term for assistive, adaptive, and rehabilitative devices for people with disabilities and the elderly. People with disabilities often have difficulty performing activities of daily living (ADLs) independently, or even with assistance. ADLs are self-care activities that include toileting, mobility (ambulation), eating, bathing, dressing, grooming, and personal device care. Assistive technology can ameliorate the effects of disabilities that limit the ability to perform ADLs. Assistive technology promotes greater independence by enabling people to perform tasks they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to, or changing methods of interacting with, the technology needed to accomplish such tasks. For example, wheelchairs provide independent mobility for those who cannot walk, while assistive eating devices can enable people who cannot feed themselves to do so. Due to assistive technology, people with disability have an opportunity of a more positive and easygoing lifestyle, with an increase in "social participation," "security and control," and a greater chance to "reduce institutional costs without significantly increasing household expenses." In schools, assistive technology can be critical in allowing students with disabilities access the general education curriculum. Students who experience challenges writing or keyboarding, for example, can use voice recognition software instead. Adaptive technology Adaptive technology and assistive technology are different. Assistive technology is something that is used to help disabled people, while adaptive technology covers items that are specifically designed for disabled people and would seldom be used by a non-disabled person. In other words, assistive technology is any object or system that helps people with disabilities, while adaptive technology is specifically designed for disabled people. Consequently, adaptive technology is a subset of assistive technology. Adaptive technology often refers specifically to electronic and information technology access. Occupational therapy Occupational therapy (OT) is a healthcare profession that specializes in maintaining or improving the quality of life for individuals that experience challenges when independently performing life's occupations. According to the Occupational Therapy Practice Framework: Domain and Process (3rd ed.; AOTA, 2014), occupations include areas related to all basic and instrumental activities of daily living (ADLs), rest and sleep, education, work, play, leisure and social participation. Occupational therapists have the specialized skill of employing assistive technology (AT) in the improvement and maintenance of optimal, functional participation in occupations. The application of AT enables an individual to adapt aspects of the environment, that may otherwise be challenging, to the user in order to optimize functional participation in those occupations. As a result, occupational therapists may educate, recommend, and promote the use of AT to improve the quality of life for their clients. Mobility impairments Wheelchairs Wheelchairs are devices that can be manually propelled or electrically propelled, and that include a seating system and are designed to be a substitute for the normal mobility that most people have. Wheelchairs and other mobility devices allow people to perform mobility-related activities of daily living which include feeding, toileting, dressing, grooming, and bathing. The devices come in a number of variations where they can be propelled either by hand or by motors where the occupant uses electrical controls to manage motors and seating control actuators through a joystick, sip-and-puff control, head switches or other input devices. Often there are handles behind the seat for someone else to do the pushing or input devices for caregivers. Wheelchairs are used by people for whom walking is difficult or impossible due to illness, injury, or disability. People with both sitting and walking disability often need to use a wheelchair or walker. Newer advancements in wheelchair design enable wheelchairs to climb stairs, go off-road or propel using segway technology or additional add-ons like handbikes or power assists. Transfer devices Patient transfer devices generally allow patients with impaired mobility to be moved by caregivers between beds, wheelchairs, commodes, toilets, chairs, stretchers, shower benches, automobiles, swimming pools, and other patient support systems (i.e., radiology, surgical, or examining tables). The most common devices are transfer benches, stretcher or convertible chairs (for lateral, supine transfer), sit-to-stand lifts (for moving patients from one seated position to another i.e., from wheelchairs to commodes), air bearing inflatable mattresses (for supine transfer i.e., transfer from a gurney to an operating room table), gait belts (or transfer belt) and a slider board (or transfer board), usually used for transfer from a bed to a wheelchair or from a bed to an operating table. Highly dependent patients who cannot assist their caregiver in moving them often require a patient lift (a floor or ceiling-suspended sling lift) which though invented in 1955 and in common use since the early 1960s is still considered the state-of-the-art transfer device by OSHA and the American Nursing Association. Walkers A walker or walking frame or Rollator is a tool for disabled people who need additional support to maintain balance or stability while walking. It consists of a frame that is about waist high, approximately twelve inches deep and slightly wider than the user. Walkers are also available in other sizes, such as for children, or for heavy people. Modern walkers are height-adjustable. The front two legs of the walker may or may not have wheels attached depending on the strength and abilities of the person using it. It is also common to see caster wheels or glides on the back legs of a walker with wheels on the front. Prosthesis A prosthesis, prosthetic, or prosthetic limb is a device that replaces a missing body part. It is part of the field of biomechatronics, the science of using mechanical devices with human muscular, musculoskeletal, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. Prostheses are typically used to replace parts lost by injury (traumatic) or missing from birth (congenital) or to supplement defective body parts. Inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. Other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. Prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. Prostheses are technically the complete finished item. For instance, a C-Leg knee alone is not a prosthesis, but only a prosthetic component. The complete prosthesis would consist of the attachment system  to the residual limb — usually a "socket", and all the attachment hardware components all the way down to and including the terminal device. Despite the technical difference, the terms are often used interchangeably. The terms "prosthetic" and "orthotic" are adjectives used to describe devices such as a prosthetic knee. The terms "prosthetics" and "orthotics" are used to describe the respective allied health fields. An Occupational Therapist's role in prosthetics include therapy, training and evaluations. Prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. Exoskeletons A powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. Its design aims to provide back support, sense the user's motion, and send a signal to motors which manage the gears. The exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. Adaptive seating and positioning People with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. This equipment is frequently specialized for specific settings such as in a classroom or nursing home.  Positioning is often important in seating arrangements to ensure that user's body pressure is distributed equally without inhibiting movement in a desired way. Positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.  These standers are generally grouped into two categories based on the position of the occupant.  Prone standers distribute the body weight to the front of the individual and usually have a tray in front of them.  This makes them good for users who are actively trying to carry out some task.  Supine standers distribute the body weight to the back and are good for cases where the user has more limited mobility or is recovering from injury. Visual impairments Many people with serious visual impairments live independently, using a wide range of tools and techniques. Examples of assistive technology for visually impairment include screen readers, screen magnifiers, Braille embossers, desktop video magnifiers, and voice recorders. Screen readers Screen readers are used to help the visually impaired to easily access electronic information. These software programs run on a computer in order to convey the displayed information through voice (text-to-speech) or braille (refreshable braille displays) in combination with magnification for low vision users in some cases. There are a variety of platforms and applications available for a variety of costs with differing feature sets. Some example of screen readers are Apple VoiceOver, Google TalkBack and Microsoft Narrator. This software is provided free of charge on all Apple devices. Apple VoiceOver includes the option to magnify the screen, control the keyboard, and provide verbal descriptions to describe what is happening on the screen. There are thirty languages to select from. It also has the capacity to read aloud file content, as well as web pages, E-mail messages, and word processing files. As mentioned above, screen readers may rely on the assistance of text-to-speech tools. To use the text-to-speech tools, the documents must in an electronic form, that is uploaded as the digital format. However, people usually will use the hard copy documents scanned into the computer, which cannot be recognized by the text-to-speech software. To solve this issue, people always use Optical Character Recognition technology accompanied with text-to-speech software. Braille and braille embossers Braille is a system of raised dots formed into units called braille cells. A full braille cell is made up of six dots, with two parallel rows of three dots, but other combinations and quantities of dots represent other letters, numbers, punctuation marks, or words. People can then use their fingers to read the code of raised dots. A braille embosser is, simply put, a printer for braille. Instead of a standard printer adding ink onto a page, the braille embosser imprints the raised dots of braille onto a page. Some braille embossers combine both braille and ink so the documents can be read with either sight or touch. Refreshable braille display A refreshable braille display or braille terminal is an electro-mechanical device for displaying braille characters, usually by means of round-tipped pins raised through holes in a flat surface. Computer users who cannot use a computer monitor use it to read a braille output version of the displayed text. Desktop video magnifier Desktop video magnifiers are electronic devices that use a camera and a display screen to perform digital magnification of printed materials. They enlarge printed pages for those with low vision. A camera connects to a monitor that displays real-time images, and the user can control settings such as magnification, focus, contrast, underlining, highlighting, and other screen preferences. They come in a variety of sizes and styles; some are small and portable with handheld cameras, while others are much larger and mounted on a fixed stand. Screen magnification software A screen magnifier is software that interfaces with a computer's graphical output to present enlarged screen content. It allows users to enlarge the texts and graphics on their computer screens for easier viewing. Similar to desktop video magnifiers, this technology assists people with low vision. After the user loads the software into their computer's memory, it serves as a kind of "computer magnifying glass." Wherever the computer cursor moves, it enlarges the area around it. This allows greater computer accessibility for a wide range of visual abilities. Large-print and tactile keyboards A large-print keyboard has large letters printed on the keys. On the keyboard shown, the round buttons at the top control software which can magnify the screen (zoom in), change the background color of the screen, or make the mouse cursor on the screen larger. The "bump dots" on the keys, installed in this case by the organization using the keyboards, help the user find the right keys in a tactile way. Navigation assistance Assistive technology for navigation has exploded on the IEEE Xplore database since 2000, with over 7,500 engineering articles written on assistive technologies and visual impairment in the past 25 years, and over 1,300 articles on solving the problem of navigation for people who are blind or visually impaired. As well, over 600 articles on augmented reality and visual impairment have appeared in the engineering literature since 2000. Most of these articles were published within the past 5 years, and the number of articles in this area is increasing every year. GPS, accelerometers, gyroscopes, and cameras can pinpoint the exact location of the user and provide information on what is in the immediate vicinity, and assistance in getting to a destination. Wearable technology Wearable technology are smart electronic devices that can be worn on the body as an implant or an accessory. New technologies are exploring how the visually impaired can receive visual information through wearable devices. Some wearable devices for visual impairment include: OrCam device eSight Brainport Personal emergency response systems Personal emergency response systems (PERS), or Telecare (UK term), are a particular sort of assistive technology that use electronic sensors connected to an alarm system to help caregivers manage risk and help vulnerable people stay independent at home longer. An example would be the systems being put in place for senior people such as fall detectors, thermometers (for hypothermia risk), flooding and unlit gas sensors (for people with mild dementia). Notably, these alerts can be customized to the particular person's risks. When the alert is triggered, a message is sent to a caregiver or contact center who can respond appropriately. Accessibility software In human–computer interaction, computer accessibility (also known as accessible computing) refers to the accessibility of a computer system to all people, regardless of disability or severity of impairment, examples include web accessibility guidelines. Another approach is for the user to present a token to the computer terminal, such as a smart card, that has configuration information to adjust the computer speed, text size, etc. to their particular needs. This is useful where users want to access public computer based terminals in Libraries, ATM, Information kiosks etc. The concept is encompassed by the CEN EN 1332-4 Identification Card Systems – Man-Machine Interface. This development of this standard has been supported in Europe by SNAPI and has been successfully incorporated into the Lasseo specifications, but with limited success due to the lack of interest from public computer terminal suppliers. Hearing impairments People in the d/Deaf and hard of hearing community have a more difficult time receiving auditory information as compared to hearing individuals. These individuals often rely on visual and tactile mediums for receiving and communicating information. The use of assistive technology and devices provides this community with various solutions to auditory communication needs by providing higher sound (for those who are hard of hearing), tactile feedback, visual cues and improved technology access. Individuals who are deaf or hard of hearing utilize a variety of assistive technologies that provide them with different access to information in numerous environments. Most devices either provide amplified sound or alternate ways to access information through vision and/or vibration. These technologies can be grouped into three general categories: Hearing Technology, alerting devices, and communication support. Hearing aids A hearing aid or deaf aid is an electro-acoustic device which is designed to amplify sound for the wearer, usually with the aim of making speech more intelligible, and to correct impaired hearing as measured by audiometry. This type of assistive technology helps people with hearing loss participate more fully in their hearing communities by allowing them to hear more clearly. They amplify any and all sound waves through use of a microphone, amplifier, and speaker. There is a wide variety of hearing aids available, including digital, in-the-ear, in-the-canal, behind-the-ear, and on-the-body aids. Assistive listening devices Assistive listening devices include FM, infrared, and loop assistive listening devices. This type of technology allows people with hearing difficulties to focus on a speaker or subject by getting rid of extra background noises and distractions, making places like auditoriums, classrooms, and meetings much easier to participate in. The assistive listening device usually uses a microphone to capture an audio source near to its origin and broadcast it wirelessly over an FM (Frequency Modulation) transmission, IR (Infra Red) transmission, IL (Induction Loop) transmission, or other transmission methods. The person who is listening may use an FM/IR/IL Receiver to tune into the signal and listen at his/her preferred volume. Amplified telephone equipment This type of assistive technology allows users to amplify the volume and clarity of their phone calls so that they can easily partake in this medium of communication. There are also options to adjust the frequency and tone of a call to suit their individual hearing needs. Additionally, there is a wide variety of amplified telephones to choose from, with different degrees of amplification. For example, a phone with 26 to 40 decibel is generally sufficient for mild hearing loss, while a phone with 71 to 90 decibel is better for more severe hearing loss. Augmentative and alternative communication Augmentative and alternative communication (AAC) is an umbrella term that encompasses methods of communication for those with impairments or restrictions on the production or comprehension of spoken or written language. AAC systems are extremely diverse and depend on the capabilities of the user. They may be as basic as pictures on a board that are used to request food, drink, or other care; or they can be advanced speech generating devices, based on speech synthesis, that are capable of storing hundreds of phrases and words. Cognitive impairments Assistive Technology for Cognition (ATC) is the use of technology (usually high tech) to augment and assist cognitive processes such as attention, memory, self-regulation, navigation, emotion recognition and management, planning, and sequencing activity. Systematic reviews of the field have found that the number of ATC are growing rapidly, but have focused on memory and planning, that there is emerging evidence for efficacy, that a lot of scope exists to develop new ATC. Examples of ATC include: NeuroPage which prompts users about meetings, Wakamaru, which provides companionship and reminds users to take medicine and calls for help if something is wrong, and telephone Reassurance systems. Memory aids Memory aids are any type of assistive technology that helps a user learn and remember certain information. Many memory aids are used for cognitive impairments such as reading, writing, or organizational difficulties. For example, a Smartpen records handwritten notes by creating both a digital copy and an audio recording of the text. Users simply tap certain parts of their notes, the pen saves it, and reads it back to them. From there, the user can also download their notes onto a computer for increased accessibility. Digital voice recorders are also used to record "in the moment" information for fast and easy recall at a later time. Educational software Educational software is software that assists people with reading, learning, comprehension, and organizational difficulties. Any accommodation software such as text readers, notetakers, text enlargers, organization tools, word predictions, and talking word processors falls under the category of educational software. Eating impairments Adaptive eating devices include items commonly used by the general population like spoons and forks and plates. However they become assistive technology when they are modified to accommodate the needs of people who have difficulty using standard cutlery due to a disabling condition. Common modifications include increasing the size of the utensil handle to make it easier to grasp. Plates and bowls may have a guard on the edge that stops food being pushed off of the dish when it is being scooped. More sophisticated equipment for eating includes manual and powered feeding devices. These devices support those who have little or no hand and arm function and enable them to eat independently. In sports Assistive technology in sports is an area of technology design that is growing. Assistive technology is the array of new devices created to enable sports enthusiasts who have disabilities to play. Assistive technology may be used in adaptive sports, where an existing sport is modified to enable players with a disability to participate; or, assistive technology may be used to invent completely new sports with athletes with disabilities exclusively in mind. An increasing number of people with disabilities are participating in sports, leading to the development of new assistive technology. Assistive technology devices can be simple, or "low-technology", or they may use highly advanced technology. "Low-tech" devices can include velcro gloves and adaptive bands and tubes. "High-tech" devices can include all-terrain wheelchairs and adaptive bicycles. Accordingly, assistive technology can be found in sports ranging from local community recreation to the elite Paralympic Games. More complex assistive technology devices have been developed over time, and as a result, sports for people with disabilities "have changed from being a clinical therapeutic tool to an increasingly competition-oriented activity". In education In the United States there are two major pieces of legislation that govern the use of assistive technology within the school system. The first is Section 504 of the Rehabilitation Act of 1973 and the second being the Individuals with Disabilities Education Act (IDEA) which was first enacted in 1975 under the name The Education for All Handicapped Children Act. In 2004, during the reauthorization period for IDEA, the National Instructional Material Access Center (NIMAC) was created which provided a repository of accessible text including publisher's textbooks to students with a qualifying disability. Files provided are in XML format and used as a starting platform for braille readers, screen readers, and other digital text software. IDEA defines assistive technology as follows: "any item, piece of equipment, or product system, whether acquired commercially off the shelf, modified, or customized, that is used to increase, maintain, or improve functional capabilities of a child with a disability. (B) Exception.--The term does not include a medical device that is surgically implanted, or the replacement of such device." Assistive technology listed is a student's IEP is not only recommended, it is required (Koch, 2017). These devices help students both with and without disabilities access the curriculum in a way they were previously unable to (Koch, 2017). Occupational therapists play an important role in educating students, parents and teachers about the assistive technology they may interact with (Koch, 2017). Assistive technology in this area is broken down into low, mid, and high tech categories. Low tech encompasses equipment that is often low cost and does not include batteries or requires charging. Examples include adapted paper and pencil grips for writing or masks and color overlays for reading. Mid tech supports used in the school setting include the use of handheld spelling dictionaries and portable word processors used to keyboard writing. High tech supports involve the use of tablet devices and computers with accompanying software. Software supports for writing include the use of auditory feedback while keyboarding, word prediction for spelling, and speech to text. Supports for reading include the use of text to speech (TTS) software and font modification via access to digital text. Limited supports are available for math instruction and mostly consist of grid based software to allow younger students to keyboard equations and auditory feedback of more complex equations using MathML and Daisy. Dementia care Assistive technology for memory support A 2017 Cochrane Review highlighted the current lack of high-quality evidence to determine whether assistive technology effectively supports people with dementia to manage memory issues. Thus, it is not presently sure whether or not assistive technology is beneficial for memory problems. Computer accessibility One of the largest problems that affect disabled people is discomfort with prostheses. An experiment performed in Massachusetts utilized 20 people with various sensors attached to their arms. The subjects tried different arm exercises, and the sensors recorded their movements. All of the data helped engineers develop new engineering concepts for prosthetics. Assistive technology may attempt to improve the ergonomics of the devices themselves such as Dvorak and other alternative keyboard layouts, which offer more ergonomic layouts of the keys. Assistive technology devices have been created to enable disabled people to use modern touch screen mobile computers such as the iPad, iPhone and iPod touch. The Pererro is a plug and play adapter for iOS devices which uses the built in Apple VoiceOver feature in combination with a basic switch. This brings touch screen technology to those who were previously unable to use it. Apple, with the release of iOS 7 had introduced the ability to navigate apps using switch control. Switch access could be activated either through an external bluetooth connected switch, single touch of the screen, or use of right and left head turns using the device's camera. Additional accessibility features include the use of Assistive Touch which allows a user to access multi-touch gestures through pre-programmed onscreen buttons. For users with physical disabilities a large variety of switches are available and customizable to the user's needs varying in size, shape, or amount of pressure required for activation. Switch access may be placed near any area of the body which has consistent and reliable mobility and less subject to fatigue. Common sites include the hands, head, and feet. Eye gaze and head mouse systems can also be used as an alternative mouse navigation. A user may utilize single or multiple switch sites and the process often involves a scanning through items on a screen and activating the switch once the desired object is highlighted. Home automation The form of home automation called assistive domotics focuses on making it possible for elderly and disabled people to live independently. Home automation is becoming a viable option for the elderly and disabled who would prefer to stay in their own homes rather than move to a healthcare facility. This field uses much of the same technology and equipment as home automation for security, entertainment, and energy conservation but tailors it towards elderly and disabled users. For example, automated prompts and reminders utilize motion sensors and pre-recorded audio messages; an automated prompt in the kitchen may remind the resident to turn off the oven, and one by the front door may remind the resident to lock the door. Impacts Overall, assistive technology aims to allow disabled people to "participate more fully in all aspects of life (home, school, and community)" and increases their opportunities for "education, social interactions, and potential for meaningful employment". It creates greater independence and control for disabled individuals. For example, in one study of 1,342 infants, toddlers and preschoolers, all with some kind of developmental, physical, sensory, or cognitive disability, the use of assistive technology created improvements in child development. These included improvements in "cognitive, social, communication, literacy, motor, adaptive, and increases in engagement in learning activities". Additionally, it has been found to lighten caregiver load. Both family and professional caregivers benefit from assistive technology. Through its use, the time that a family member or friend would need to care for a patient significantly decreases. However, studies show that care time for a professional caregiver increases when assistive technology is used. Nonetheless, their work load is significantly easier as the assistive technology frees them of having to perform certain tasks. There are several platforms that use machine learning to identify the appropriate assistive device to suggest to patients, making assistive devices more accessible. See also Accessibility Assisted Living Augmentative and alternative communication Braille technology Design for All (in ICT) Disability Flag Durable medical equipment Matching person and technology model OATS: Open Source Assistive Technology Software Occupational Therapy Transgenerational design Universal access to education References Bibliography Educational technology Web accessibility

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

655

https://en.wikipedia.org/wiki/Abacus

Abacus

The abacus (plural abaci or abacuses), also called a counting frame, is a calculating tool which has been used since ancient times. It was used in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the Hindu-Arabic numeral system. The exact origin of the abacus has not yet emerged. It consists of rows of movable beads, or similar objects, strung on a wire. They represent digits. One of the two numbers is set up, and the beads are manipulated to perform an operation such as addition, or even a square or cubic root. In their earliest designs, the rows of beads could be loose on a flat surface or sliding in grooves. Later the beads were made to slide on rods and built into a frame, allowing faster manipulation. Abacuses are still made, often as a bamboo frame with beads sliding on wires. In the ancient world, particularly before the introduction of positional notation, abacuses were a practical calculating tool. The abacus is still used to teach the fundamentals of mathematics to some children, e.g., in post-Soviet states. Designs such as the Japanese soroban have been used for practical calculations of up to multi-digit numbers. Any particular abacus design supports multiple methods to perform calculations, including the four basic operations and square and cube roots. Some of these methods work with non-natural numbers (numbers such as and ). Although calculators and computers are commonly used today instead of abacuses, abacuses remain in everyday use in some countries. Merchants, traders, and clerks in some parts of Eastern Europe, Russia, China, and Africa use abacuses. The abacus remains in common use as a scoring system in non-electronic table games. Others may use an abacus due to visual impairment that prevents the use of a calculator. Etymology The word abacus dates to at least AD 1387 when a Middle English work borrowed the word from Latin that described a sandboard abacus. The Latin word is derived from ancient Greek (abax) which means something without a base, and colloquially, any piece of rectangular material. Alternatively, without reference to ancient texts on etymology, it has been suggested that it means "a square tablet strewn with dust", or "drawing-board covered with dust (for the use of mathematics)" (the exact shape of the Latin perhaps reflects the genitive form of the Greek word, (abakos). While the table strewn with dust definition is popular, some argue evidence is insufficient for that conclusion. Greek probably borrowed from a Northwest Semitic language like Phoenician, evidenced by a cognate with the Hebrew word ʾābāq (), or “dust” (in the post-Biblical sense "sand used as a writing surface"). Both abacuses and abaci (soft or hard "c") are used as plurals. The user of an abacus is called an abacist. History Mesopotamia The Sumerian abacus appeared between 2700–2300 BC. It held a table of successive columns which delimited the successive orders of magnitude of their sexagesimal (base 60) number system. Some scholars point to a character in Babylonian cuneiform that may have been derived from a representation of the abacus. It is the belief of Old Babylonian scholars, such as Ettore Carruccio, that Old Babylonians "may have used the abacus for the operations of addition and subtraction; however, this primitive device proved difficult to use for more complex calculations". Egypt Greek historian Herodotus mentioned the abacus in Ancient Egypt. He wrote that the Egyptians manipulated the pebbles from right to left, opposite in direction to the Greek left-to-right method. Archaeologists have found ancient disks of various sizes that are thought to have been used as counters. However, wall depictions of this instrument are yet to be discovered. Persia At around 600 BC, Persians first began to use the abacus, during the Achaemenid Empire. Under the Parthian, Sassanian, and Iranian empires, scholars concentrated on exchanging knowledge and inventions with the countries around them – India, China, and the Roman Empire- which is how the abacus may have been exported to other countries. Greece The earliest archaeological evidence for the use of the Greek abacus dates to the 5th century BC. Demosthenes (384 BC–322 BC) complained that the need to use pebbles for calculations was too difficult. A play by Alexis from the 4th century BC mentions an abacus and pebbles for accounting, and both Diogenes and Polybius use the abacus as a metaphor for human behavior, stating "that men that sometimes stood for more and sometimes for less" like the pebbles on an abacus. The Greek abacus was a table of wood or marble, pre-set with small counters in wood or metal for mathematical calculations. This Greek abacus saw use in Achaemenid Persia, the Etruscan civilization, Ancient Rome, and the Western Christian world until the French Revolution. A tablet found on the Greek island Salamis in 1846 AD (the Salamis Tablet) dates to 300 BC, making it the oldest counting board discovered so far. It is a slab of white marble in length, wide, and thick, on which are 5 groups of markings. In the tablet's center is a set of 5 parallel lines equally divided by a vertical line, capped with a semicircle at the intersection of the bottom-most horizontal line and the single vertical line. Below these lines is a wide space with a horizontal crack dividing it. Below this crack is another group of eleven parallel lines, again divided into two sections by a line perpendicular to them, but with the semicircle at the top of the intersection; the third, sixth and ninth of these lines are marked with a cross where they intersect with the vertical line. Also from this time frame, the Darius Vase was unearthed in 1851. It was covered with pictures, including a "treasurer" holding a wax tablet in one hand while manipulating counters on a table with the other. China The earliest known written documentation of the Chinese abacus dates to the 2nd century BC. The Chinese abacus, also known as the suanpan (算盤/算盘, lit. "calculating tray"), is typically tall and comes in various widths, depending on the operator. It usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom one. The beads are usually rounded and made of hardwood. The beads are counted by moving them up or down towards the beam; beads moved toward the beam are counted, while those moved away from it are not. One of the top beads is 5, while one of the bottom beads is 1. Each rod has a number under it, showing the place value. The suanpan can be reset to the starting position instantly by a quick movement along the horizontal axis to spin all the beads away from the horizontal beam at the center. The prototype of the Chinese abacus appeared during the Han Dynasty, and the beads are oval. The Song Dynasty and earlier used the 1:4 type or four-beads abacus similar to the modern abacus including the shape of the beads commonly known as Japanese-style abacus. In the early Ming Dynasty, the abacus began to appear in a 1:5 ratio. The upper deck had one bead and the bottom had five beads. In the late Ming Dynasty, the abacus styles appeared in a 2:5 ratio. The upper deck had two beads, and the bottom had five. Various calculation techniques were devised for Suanpan enabling efficient calculations. Some schools teach students how to use it. In the long scroll Along the River During the Qingming Festival painted by Zhang Zeduan during the Song dynasty (960–1297), a suanpan is clearly visible beside an account book and doctor's prescriptions on the counter of an apothecary's (Feibao). The similarity of the Roman abacus to the Chinese one suggests that one could have inspired the other, given evidence of a trade relationship between the Roman Empire and China. However, no direct connection has been demonstrated, and the similarity of the abacuses may be coincidental, both ultimately arising from counting with five fingers per hand. Where the Roman model (like most modern Korean and Japanese) has 4 plus 1 bead per decimal place, the standard suanpan has 5 plus 2. Incidentally, this allows use with a hexadecimal numeral system (or any base up to 18) which may have been used for traditional Chinese measures of weight. (Instead of running on wires as in the Chinese, Korean, and Japanese models, the Roman model used grooves, presumably making arithmetic calculations much slower.) Another possible source of the suanpan is Chinese counting rods, which operated with a decimal system but lacked the concept of zero as a placeholder. The zero was probably introduced to the Chinese in the Tang dynasty (618–907) when travel in the Indian Ocean and the Middle East would have provided direct contact with India, allowing them to acquire the concept of zero and the decimal point from Indian merchants and mathematicians. Rome The normal method of calculation in ancient Rome, as in Greece, was by moving counters on a smooth table. Originally pebbles (calculi) were used. Later, and in medieval Europe, jetons were manufactured. Marked lines indicated units, fives, tens, etc. as in the Roman numeral system. This system of 'counter casting' continued into the late Roman empire and in medieval Europe and persisted in limited use into the nineteenth century. Due to Pope Sylvester II's reintroduction of the abacus with modifications, it became widely used in Europe again during the 11th century This abacus used beads on wires, unlike the traditional Roman counting boards, which meant the abacus could be used much faster and was more easily moved. Writing in the 1st century BC, Horace refers to the wax abacus, a board covered with a thin layer of black wax on which columns and figures were inscribed using a stylus. One example of archaeological evidence of the Roman abacus, shown nearby in reconstruction, dates to the 1st century AD. It has eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each. The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives –five units, five tens, etc., essentially in a bi-quinary coded decimal system, related to the Roman numerals. The short grooves on the right may have been used for marking Roman "ounces" (i.e. fractions). India The Abhidharmakośabhāṣya of Vasubandhu (316-396), a Sanskrit work on Buddhist philosophy, says that the second-century CE philosopher Vasumitra said that "placing a wick (Sanskrit vartikā) on the number one (ekāṅka) means it is a one while placing the wick on the number hundred means it is called a hundred, and on the number one thousand means it is a thousand". It is unclear exactly what this arrangement may have been. Around the 5th century, Indian clerks were already finding new ways of recording the contents of the abacus. Hindu texts used the term śūnya (zero) to indicate the empty column on the abacus. Japan In Japan, the abacus is called soroban (, lit. "counting tray"). It was imported from China in the 14th century. It was probably in use by the working class a century or more before the ruling class adopted it, as the class structure obstructed such changes. The 1:4 abacus, which removes the seldom-used second and fifth bead became popular in the 1940s. Today's Japanese abacus is a 1:4 type, four-bead abacus, introduced from China in the Muromachi era. It adopts the form of the upper deck one bead and the bottom four beads. The top bead on the upper deck was equal to five and the bottom one is similar to the Chinese or Korean abacus, and the decimal number can be expressed, so the abacus is designed as a one:four device. The beads are always in the shape of a diamond. The quotient division is generally used instead of the division method; at the same time, in order to make the multiplication and division digits consistently use the division multiplication. Later, Japan had a 3:5 abacus called 天三算盤, which is now in the Ize Rongji collection of Shansi Village in Yamagata City. Japan also used a 2:5 type abacus. The four-bead abacus spread, and became common around the world. Improvements to the Japanese abacus arose in various places. In China an aluminium frame plastic bead abacus was used. The file is next to the four beads, and pressing the "clearing" button put the upper bead in the upper position, and the lower bead in the lower position. The abacus is still manufactured in Japan even with the proliferation, practicality, and affordability of pocket electronic calculators. The use of the soroban is still taught in Japanese primary schools as part of mathematics, primarily as an aid to faster mental calculation. Using visual imagery can complete a calculation as quickly as a physical instrument. Korea The Chinese abacus migrated from China to Korea around 1400 AD. Koreans call it jupan (주판), supan (수판) or jusan (주산). The four-beads abacus (1:4) was introduced during the Goryeo Dynasty. The 5:1 abacus was introduced to Korea from China during the Ming Dynasty. Native America Some sources mention the use of an abacus called a nepohualtzintzin in ancient Aztec culture. This Mesoamerican abacus used a 5-digit base-20 system. The word Nepōhualtzintzin comes from Nahuatl, formed by the roots; Ne – personal -; pōhual or pōhualli – the account -; and tzintzin – small similar elements. Its complete meaning was taken as: counting with small similar elements. Its use was taught in the Calmecac to the temalpouhqueh , who were students dedicated to taking the accounts of skies, from childhood. The Nepōhualtzintzin was divided into two main parts separated by a bar or intermediate cord. In the left part were four beads. Beads in the first row have unitary values (1, 2, 3, and 4), and on the right side, three beads had values of 5, 10, and 15, respectively. In order to know the value of the respective beads of the upper rows, it is enough to multiply by 20 (by each row), the value of the corresponding count in the first row. The device featured 13 rows with 7 beads, 91 in total. This was a basic number for this culture. It had a close relation to natural phenomena, the underworld, and the cycles of the heavens. One Nepōhualtzintzin (91) represented the number of days that a season of the year lasts, two Nepōhualtzitzin (182) is the number of days of the corn's cycle, from its sowing to its harvest, three Nepōhualtzintzin (273) is the number of days of a baby's gestation, and four Nepōhualtzintzin (364) completed a cycle and approximated one year. When translated into modern computer arithmetic, the Nepōhualtzintzin amounted to the rank from 10 to 18 in floating point, which precisely calculated large and small amounts, although round off was not allowed. The rediscovery of the Nepōhualtzintzin was due to the Mexican engineer David Esparza Hidalgo, who in his travels throughout Mexico found diverse engravings and paintings of this instrument and reconstructed several of them in gold, jade, encrustations of shell, etc. Very old Nepōhualtzintzin are attributed to the Olmec culture, and some bracelets of Mayan origin, as well as a diversity of forms and materials in other cultures. Sanchez wrote in Arithmetic in Maya that another base 5, base 4 abacus had been found in the Yucatán Peninsula that also computed calendar data. This was a finger abacus, on one hand, 0, 1, 2, 3, and 4 were used; and on the other hand 0, 1, 2, and 3 were used. Note the use of zero at the beginning and end of the two cycles. The quipu of the Incas was a system of colored knotted cords used to record numerical data, like advanced tally sticks – but not used to perform calculations. Calculations were carried out using a yupana (Quechua for "counting tool"; see figure) which was still in use after the conquest of Peru. The working principle of a yupana is unknown, but in 2001 Italian mathematician De Pasquale proposed an explanation. By comparing the form of several yupanas, researchers found that calculations were based using the Fibonacci sequence 1, 1, 2, 3, 5 and powers of 10, 20, and 40 as place values for the different fields in the instrument. Using the Fibonacci sequence would keep the number of grains within any one field at a minimum. Russia The Russian abacus, the schoty (, plural from , counting), usually has a single slanted deck, with ten beads on each wire (except one wire with four beads for quarter-ruble fractions). Older models have another 4-bead wire for quarter-kopeks, which were minted until 1916. The Russian abacus is often used vertically, with each wire running horizontally. The wires are usually bowed upward in the center, to keep the beads pinned to either side. It is cleared when all the beads are moved to the right. During manipulation, beads are moved to the left. For easy viewing, the middle 2 beads on each wire (the 5th and 6th bead) usually are of a different color from the other eight. Likewise, the left bead of the thousands wire (and the million wire, if present) may have a different color. The Russian abacus was in use in shops and markets throughout the former Soviet Union, and its usage was taught in most schools until the 1990s. Even the 1874 invention of mechanical calculator, Odhner arithmometer, had not replaced them in Russia; according to Yakov Perelman. Some businessmen attempting to import calculators into the Russian Empire were known to leave in despair after watching a skilled abacus operator. Likewise, the mass production of Felix arithmometers since 1924 did not significantly reduce abacus use in the Soviet Union. The Russian abacus began to lose popularity only after the mass production of domestic microcalculators in 1974. The Russian abacus was brought to France around 1820 by mathematician Jean-Victor Poncelet, who had served in Napoleon's army and had been a prisoner of war in Russia. The abacus had fallen out of use in western Europe in the 16th century with the rise of decimal notation and algorismic methods. To Poncelet's French contemporaries, it was something new. Poncelet used it, not for any applied purpose, but as a teaching and demonstration aid. The Turks and the Armenian people used abacuses similar to the Russian schoty. It was named a coulba by the Turks and a choreb by the Armenians. School abacus Around the world, abacuses have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic. In Western countries, a bead frame similar to the Russian abacus but with straight wires and a vertical frame is common (see image). The wireframe may be used either with positional notation like other abacuses (thus the 10-wire version may represent numbers up to 9,999,999,999), or each bead may represent one unit (e.g. 74 can be represented by shifting all beads on 7 wires and 4 beads on the 8th wire, so numbers up to 100 may be represented). In the bead frame shown, the gap between the 5th and 6th wire, corresponding to the color change between the 5th and the 6th bead on each wire, suggests the latter use. Teaching multiplication, e.g. 6 times 7, may be represented by shifting 7 beads on 6 wires. The red-and-white abacus is used in contemporary primary schools for a wide range of number-related lessons. The twenty bead version, referred to by its Dutch name rekenrek ("calculating frame"), is often used, either on a string of beads or on a rigid framework. Feynman vs the abacus Physicist Richard Feynman was noted for facility in mathematical calculations. He wrote about an encounter in Brazil with a Japanese abacus expert, who challenged him to speed contests between Feynman's pen and paper, and the abacus. The abacus was much faster for addition, somewhat faster for multiplication, but Feynman was faster at division. When the abacus was used for a really difficult challenge, i.e. cube roots, Feynman won easily. However, the number chosen at random was close to a number Feynman happened to know was an exact cube, allowing him to use approximate methods. Neurological analysis Learning how to calculate with the abacus may improve capacity for mental calculation. Abacus-based mental calculation (AMC), which was derived from the abacus, is the act of performing calculations, including addition, subtraction, multiplication, and division, in the mind by manipulating an imagined abacus. It is a high-level cognitive skill that runs calculations with an effective algorithm. People doing long-term AMC training show higher numerical memory capacity and experience more effectively connected neural pathways. They are able to retrieve memory to deal with complex processes. AMC involves both visuospatial and visuomotor processing that generate the visual abacus and move the imaginary beads. Since it only requires that the final position of beads be remembered, it takes less memory and less computation time. Renaissance abacuses Binary abacus The binary abacus is used to explain how computers manipulate numbers. The abacus shows how numbers, letters, and signs can be stored in a binary system on a computer, or via ASCII. The device consists of a series of beads on parallel wires arranged in three separate rows. The beads represent a switch on the computer in either an "on" or "off" position. Visually impaired users An adapted abacus, invented by Tim Cranmer, and called a Cranmer abacus is commonly used by visually impaired users. A piece of soft fabric or rubber is placed behind the beads, keeping them in place while the users manipulate them. The device is then used to perform the mathematical functions of multiplication, division, addition, subtraction, square root, and cube root. Although blind students have benefited from talking calculators, the abacus is often taught to these students in early grades. Blind students can also complete mathematical assignments using a braille-writer and Nemeth code (a type of braille code for mathematics) but large multiplication and long division problems are tedious. The abacus gives these students a tool to compute mathematical problems that equals the speed and mathematical knowledge required by their sighted peers using pencil and paper. Many blind people find this number machine a useful tool throughout life. See also Chinese Zhusuan Chisanbop Logical abacus Mental abacus Napier's bones Sand table Slide rule Soroban Suanpan Notes Footnotes References Reading External links Tutorials Min Multimedia Abacus curiosities Abacus in Various Number Systems at cut-the-knot Java applet of Chinese, Japanese and Russian abaci An atomic-scale abacus Examples of Abaci Aztex Abacus Indian Abacus Mathematical tools Chinese mathematics Egyptian mathematics Greek mathematics Indian mathematics Japanese mathematics Roman mathematics

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

661

https://en.wikipedia.org/wiki/Argument%20%28disambiguation%29

Argument (disambiguation)

In logic and philosophy, an argument is an attempt to persuade someone of something, or give evidence or reasons for accepting a particular conclusion. Argument may also refer to: Mathematics and computer science Argument (complex analysis), a function which returns the polar angle of a complex number Command-line argument, an item of information provided to a program when it is started Parameter (computer programming), a piece of data provided as input to a subroutine Argument principle, a theorem in complex analysis An argument of a function, also known as an independent variable Language and rhetoric Argument (literature), a brief summary, often in prose, of a poem or section of a poem or other work Argument (linguistics), a phrase that appears in a syntactic relationship with the verb in a clause Oral argument in the United States, a spoken presentation to a judge or appellate court by a lawyer (or parties when representing themselves) of the legal reasons why they should prevail Closing argument, in law, the concluding statement of each party's counsel reiterating the important arguments in a court case Other uses Musical argument, a concept in the theory of musical form Argument (ship), an Australian sloop wrecked in 1809 Das Argument, a German academic journal Argument Clinic, a Monty Python sketch A disagreement between two or more parties or the discussion of the disagreement Argument (horse) See also The Argument (disambiguation)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

664

https://en.wikipedia.org/wiki/Astronaut

Astronaut

An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the term is sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists. "Astronaut" technically applies to all human space travelers regardless of nationality or allegiance; however, astronauts fielded by Russia or the Soviet Union are typically known instead as cosmonauts (from the Russian "kosmos" (космос), meaning "space", also borrowed from Greek) in order to distinguish them from American or otherwise NATO-oriented space travellers. Comparatively recent developments in crewed spaceflight made by China have led to the rise of the term taikonaut (from the Mandarin "tàikōng" (), meaning "space"), although its use is somewhat informal and its origin is unclear. In China, the People's Liberation Army Astronaut Corps astronauts and their foreign counterparts are all officially called hángtiānyuán (, meaning "heaven navigator" or literally "heaven-sailing staff"). Since 1961, 600 astronauts have flown in space. Until 2002, astronauts were sponsored and trained exclusively by governments, either by the military or by civilian space agencies. With the suborbital flight of the privately funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut. Definition The criteria for what constitutes human spaceflight vary, with some focus on the point where the atmosphere becomes so thin that centrifugal force, rather than aerodynamic force, carries a significant portion of the weight of the flight object. The Fédération Aéronautique Internationale (FAI) Sporting Code for astronautics recognizes only flights that exceed the Kármán line, at an altitude of . In the United States, professional, military, and commercial astronauts who travel above an altitude of are awarded astronaut wings. , 552 people from 36 countries have reached or more in altitude, of whom 549 reached low Earth orbit or beyond. Of these, 24 people have traveled beyond low Earth orbit, either to lunar orbit, the lunar surface, or, in one case, a loop around the Moon. Three of the 24—Jim Lovell, John Young and Eugene Cernan—did so twice. , under the U.S. definition, 558 people qualify as having reached space, above altitude. Of eight X-15 pilots who exceeded in altitude, only one, Joseph A. Walker, exceeded 100 kilometers (about 62.1 miles) and he did it two times, becoming the first person in space twice. Space travelers have spent over 41,790 man-days (114.5 man-years) in space, including over 100 astronaut-days of spacewalks. , the man with the longest cumulative time in space is Gennady Padalka, who has spent 879 days in space. Peggy A. Whitson holds the record for the most time in space by a woman, 377 days. Terminology In 1959, when both the United States and Soviet Union were planning, but had yet to launch humans into space, NASA Administrator T. Keith Glennan and his Deputy Administrator, Hugh Dryden, discussed whether spacecraft crew members should be called astronauts or cosmonauts. Dryden preferred "cosmonaut", on the grounds that flights would occur in and to the broader cosmos, while the "astro" prefix suggested flight specifically to the stars. Most NASA Space Task Group members preferred "astronaut", which survived by common usage as the preferred American term. When the Soviet Union launched the first man into space, Yuri Gagarin in 1961, they chose a term which anglicizes to "cosmonaut". Astronaut A professional space traveler is called an astronaut. The first known use of the term "astronaut" in the modern sense was by Neil R. Jones in his 1930 short story "The Death's Head Meteor". The word itself had been known earlier; for example, in Percy Greg's 1880 book Across the Zodiac, "astronaut" referred to a spacecraft. In Les Navigateurs de l'Infini (1925) by J.-H. Rosny aîné, the word astronautique (astronautic) was used. The word may have been inspired by "aeronaut", an older term for an air traveler first applied in 1784 to balloonists. An early use of "astronaut" in a non-fiction publication is Eric Frank Russell's poem "The Astronaut", appearing in the November 1934 Bulletin of the British Interplanetary Society. The first known formal use of the term astronautics in the scientific community was the establishment of the annual International Astronautical Congress in 1950, and the subsequent founding of the International Astronautical Federation the following year. NASA applies the term astronaut to any crew member aboard NASA spacecraft bound for Earth orbit or beyond. NASA also uses the term as a title for those selected to join its Astronaut Corps. The European Space Agency similarly uses the term astronaut for members of its Astronaut Corps. Cosmonaut By convention, an astronaut employed by the Russian Federal Space Agency (or its Soviet predecessor) is called a cosmonaut in English texts. The word is an Anglicization of kosmonavt ( ). Other countries of the former Eastern Bloc use variations of the Russian kosmonavt, such as the (although Polish also uses , and the two words are considered synonyms). Coinage of the term has been credited to Soviet aeronautics (or "cosmonautics") pioneer Mikhail Tikhonravov (1900–1974). The first cosmonaut was Soviet Air Force pilot Yuri Gagarin, also the first person in space. He was part of the first six Russians, with German Titov, Yevgeny Khrunov, Andriyan Nikolayev, Pavel Popovich, and Grigoriy Nelyubov, who were given the title of pilot-cosmonaut in January 1961. Valentina Tereshkova was the first female cosmonaut and the first and youngest woman to have flown in space with a solo mission on the Vostok 6 in 1963. On 14 March 1995, Norman Thagard became the first American to ride to space on board a Russian launch vehicle, and thus became the first "American cosmonaut". Taikonaut In Chinese, the term (, "cosmos navigating personnel") is used for astronauts and cosmonauts in general, while (, "navigating celestial-heaven personnel") is used for Chinese astronauts. Here, (, literally "heaven-navigating", or spaceflight) is strictly defined as the navigation of outer space within the local star system, i.e. Solar System. The phrase (, "spaceman") is often used in Hong Kong and Taiwan. The term taikonaut is used by some English-language news media organizations for professional space travelers from China. The word has featured in the Longman and Oxford English dictionaries, and the term became more common in 2003 when China sent its first astronaut Yang Liwei into space aboard the Shenzhou 5 spacecraft. This is the term used by Xinhua News Agency in the English version of the Chinese People's Daily since the advent of the Chinese space program. The origin of the term is unclear; as early as May 1998, Chiew Lee Yih () from Malaysia, used it in newsgroups. Parastronaut For its 2022 Astronaut Group, ESA envisions recruiting an astronaut with a physical disability, a category they called "parastronauts", with the intention but not guarantee of spaceflight. The categories of disability considered for the program were individuals with lower limb deficiency (either through amputation or congenital), leg length difference, or a short stature (less than ). Other terms With the rise of space tourism, NASA and the Russian Federal Space Agency agreed to use the term "spaceflight participant" to distinguish those space travelers from professional astronauts on missions coordinated by those two agencies. While no nation other than Russia (and previously the Soviet Union), the United States, and China have launched a crewed spacecraft, several other nations have sent people into space in cooperation with one of these countries, e.g. the Soviet-led Interkosmos program. Inspired partly by these missions, other synonyms for astronaut have entered occasional English usage. For example, the term spationaut () is sometimes used to describe French space travelers, from the Latin word for "space"; the Malay term (deriving from angkasa meaning 'space') was used to describe participants in the Angkasawan program (note its similarity with the Indonesian term antariksawan). Plans of the Indian Space Research Organisation to launch its crewed Gaganyaan spacecraft have spurred at times public discussion if another term than astronaut should be used for the crew members, suggesting vyomanaut (from the Sanskrit word / meaning 'sky' or 'space') or gagannaut (from the Sanskrit word for 'sky'). In Finland, the NASA astronaut Timothy Kopra, a Finnish American, has sometimes been referred to as , from the Finnish word . Across Germanic languages, "astronaut" is used in conjunction with locally derived words like German's Raumfahrer, Dutch's ruimtevaarder, Swedish's rymdfarare and Norwegian's romfarer. As of 2021 in the United States, astronaut status is conferred on a person depending on the authorizing agency: one who flies in a vehicle above for NASA or the military is considered an astronaut (with no qualifier) one who flies in a vehicle to the International Space Station in a mission coordinated by NASA and Roscosmos is a spaceflight participant one who flies above in a non-NASA vehicle as a crewmember and demonstrates activities during flight that are essential to public safety, or contribute to human space flight safety, is considered a commercial astronaut by the Federal Aviation Administration one who flies to the International Space Station as part of a "privately funded, dedicated commercial spaceflight on a commercial launch vehicle dedicated to the mission ... to conduct approved commercial and marketing activities on the space station (or in a commercial segment attached to the station)" is considered a private astronaut by NASA (as of 2020, nobody has yet qualified for this status) a generally-accepted but unofficial term for a paying non-crew passenger who flies a private non-NASA or military vehicles above is a space tourist (as of 2020, nobody has yet qualified for this status) On July 20, 2021, the FAA issued an order redefining the eligibility criteria to be an astronaut in response to the private suborbital spaceflights of Jeff Bezos and Richard Branson. The new criteria states that one must have "[d]emonstrated activities during flight that were essential to public safety, or contributed to human space flight safety" in order to qualify as an astronaut. This new definition excludes Bezos and Branson. Space travel milestones The first human in space was Soviet Yuri Gagarin, who was launched on 12 April 1961, aboard Vostok 1 and orbited around the Earth for 108 minutes. The first woman in space was Soviet Valentina Tereshkova, who launched on 16 June 1963, aboard Vostok 6 and orbited Earth for almost three days. Alan Shepard became the first American and second person in space on 5 May 1961, on a 15-minute sub-orbital flight aboard Freedom 7. The first American to orbit the Earth was John Glenn, aboard Friendship 7 on 20 February 1962. The first American woman in space was Sally Ride, during Space Shuttle Challenger's mission STS-7, on 18 June 1983. In 1992, Mae Jemison became the first African American woman to travel in space aboard STS-47. Cosmonaut Alexei Leonov was the first person to conduct an extravehicular activity (EVA), (commonly called a "spacewalk"), on 18 March 1965, on the Soviet Union's Voskhod 2 mission. This was followed two and a half months later by astronaut Ed White who made the first American EVA on NASA's Gemini 4 mission. The first crewed mission to orbit the Moon, Apollo 8, included American William Anders who was born in Hong Kong, making him the first Asian-born astronaut in 1968. The Soviet Union, through its Intercosmos program, allowed people from other "socialist" (i.e. Warsaw Pact and other Soviet-allied) countries to fly on its missions, with the notable exceptions of France and Austria participating in Soyuz TM-7 and Soyuz TM-13, respectively. An example is Czechoslovak Vladimír Remek, the first cosmonaut from a country other than the Soviet Union or the United States, who flew to space in 1978 on a Soyuz-U rocket. Rakesh Sharma became the first Indian citizen to travel to space. He was launched aboard Soyuz T-11, on 2 April 1984. On 23 July 1980, Pham Tuan of Vietnam became the first Asian in space when he flew aboard Soyuz 37. Also in 1980, Cuban Arnaldo Tamayo Méndez became the first person of Hispanic and black African descent to fly in space, and in 1983, Guion Bluford became the first African American to fly into space. In April 1985, Taylor Wang became the first ethnic Chinese person in space. The first person born in Africa to fly in space was Patrick Baudry (France), in 1985. In 1985, Saudi Arabian Prince Sultan Bin Salman Bin AbdulAziz Al-Saud became the first Arab Muslim astronaut in space. In 1988, Abdul Ahad Mohmand became the first Afghan to reach space, spending nine days aboard the Mir space station. With the increase of seats on the Space Shuttle, the U.S. began taking international astronauts. In 1983, Ulf Merbold of West Germany became the first non-US citizen to fly in a US spacecraft. In 1984, Marc Garneau became the first of eight Canadian astronauts to fly in space (through 2010). In 1985, Rodolfo Neri Vela became the first Mexican-born person in space. In 1991, Helen Sharman became the first Briton to fly in space. In 2002, Mark Shuttleworth became the first citizen of an African country to fly in space, as a paying spaceflight participant. In 2003, Ilan Ramon became the first Israeli to fly in space, although he died during a re-entry accident. On 15 October 2003, Yang Liwei became China's first astronaut on the Shenzhou 5 spacecraft. On 30 May 2020, Doug Hurley and Bob Behnken became the first astronauts to launch on a private crewed spacecraft, Crew Dragon. Age milestones The youngest person to reach space is Oliver Daemen, who was 18 years and 11 months old when he made a suborbital spaceflight lasting 7 minutes on July 20, 2021. Daemen, who was a commercial passenger aboard the New Shepard, broke the record of Soviet cosmonaut Gherman Titov, who was 25 years old when he flew Vostok 2. Titov remains the youngest human to reach orbit; he rounded the planet 17 times. Titov was also the first person to suffer space sickness and the first person to sleep in space, twice. On the same flight as Daemen was 82 year, 6-month-old Wally Funk, one of the women dubbed the Mercury 13, and now the oldest person in space. She is the first of the Mercury 13 to reach space, although the group was trained concurrently with the all-male Mercury 7, who would all engage in space travel. The oldest person to reach orbit is John Glenn, one of the Mercury 7, who was 77 when he flew on STS-95. For suborbital age records, see . Duration and distance milestones 438 days is the longest time spent in space, by Russian Valeri Polyakov. As of 2006, the most spaceflights by an individual astronaut is seven, a record held by both Jerry L. Ross and Franklin Chang-Diaz. The farthest distance from Earth an astronaut has traveled was , when Jim Lovell, Jack Swigert, and Fred Haise went around the Moon during the Apollo 13 emergency. Civilian and non-government milestones The first civilian in space was Valentina Tereshkova aboard Vostok 6 (she also became the first woman in space on that mission). Tereshkova was only honorarily inducted into the USSR's Air Force, which did not accept female pilots at that time. A month later, Joseph Albert Walker became the first American civilian in space when his X-15 Flight 90 crossed the line, qualifying him by the international definition of spaceflight. Walker had joined the US Army Air Force but was not a member during his flight. The first people in space who had never been a member of any country's armed forces were both Konstantin Feoktistov and Boris Yegorov aboard Voskhod 1. The first non-governmental space traveler was Byron K. Lichtenberg, a researcher from the Massachusetts Institute of Technology who flew on STS-9 in 1983. In December 1990, Toyohiro Akiyama became the first paying space traveler and the first journalist in space for Tokyo Broadcasting System, a visit to Mir as part of an estimated $12 million (USD) deal with a Japanese TV station, although at the time, the term used to refer to Akiyama was "Research Cosmonaut". Akiyama suffered severe space sickness during his mission, which affected his productivity. The first self-funded space tourist was Dennis Tito on board the Russian spacecraft Soyuz TM-3 on 28 April 2001. Self-funded travelers The first person to fly on an entirely privately funded mission was Mike Melvill, piloting SpaceShipOne flight 15P on a suborbital journey, although he was a test pilot employed by Scaled Composites and not an actual paying space tourist. Seven others have paid the Russian Space Agency to fly into space: Dennis Tito (American): 28 April – 6 May 2001 (ISS) Mark Shuttleworth (South African): 25 April – 5 May 2002 (ISS) Gregory Olsen (American): 1–11 October 2005 (ISS) Anousheh Ansari (Iranian / American): 18–29 September 2006 (ISS) Charles Simonyi (Hungarian / American): 7–21 April 2007 (ISS), 26 March – 8 April 2009 (ISS) Richard Garriott (British / American): 12–24 October 2008 (ISS) Guy Laliberté (Canadian): 30 September 2009 – 11 October 2009 (ISS) Jared Isaacman (American): 15–18 September 2021 (Free Flier) Yusaku Maezawa (Japanese): 8 – 24 December 2021 (ISS) Training The first NASA astronauts were selected for training in 1959. Early in the space program, military jet test piloting and engineering training were often cited as prerequisites for selection as an astronaut at NASA, although neither John Glenn nor Scott Carpenter (of the Mercury Seven) had any university degree, in engineering or any other discipline at the time of their selection. Selection was initially limited to military pilots. The earliest astronauts for both the US and the USSR tended to be jet fighter pilots, and were often test pilots. Once selected, NASA astronauts go through twenty months of training in a variety of areas, including training for extravehicular activity in a facility such as NASA's Neutral Buoyancy Laboratory. Astronauts-in-training (astronaut candidates) may also experience short periods of weightlessness (microgravity) in an aircraft called the "Vomit Comet," the nickname given to a pair of modified KC-135s (retired in 2000 and 2004, respectively, and replaced in 2005 with a C-9) which perform parabolic flights. Astronauts are also required to accumulate a number of flight hours in high-performance jet aircraft. This is mostly done in T-38 jet aircraft out of Ellington Field, due to its proximity to the Johnson Space Center. Ellington Field is also where the Shuttle Training Aircraft is maintained and developed, although most flights of the aircraft are conducted from Edwards Air Force Base. Astronauts in training must learn how to control and fly the Space Shuttle and, it is vital that they are familiar with the International Space Station so they know what they must do when they get there. NASA candidacy requirements The candidate must be a citizen of the United States. The candidate must complete a master's degree in a STEM field, including engineering, biological science, physical science, computer science or mathematics. The candidate must have at least two years of related professional experience obtained after degree completion or at least 1,000 hours pilot-in-command time on jet aircraft. The candidate must be able to pass the NASA long-duration flight astronaut physical. The candidate must also have skills in leadership, teamwork and communications. The master's degree requirement can also be met by: Two years of work toward a doctoral program in a related science, technology, engineering or math field. A completed Doctor of Medicine or Doctor of Osteopathic Medicine degree. Completion of a nationally recognized test pilot school program. Mission Specialist Educator Applicants must have a bachelor's degree with teaching experience, including work at the kindergarten through twelfth grade level. An advanced degree, such as a master's degree or a doctoral degree, is not required, but is strongly desired. Mission Specialist Educators, or "Educator Astronauts", were first selected in 2004, and as of 2007, there are three NASA Educator astronauts: Joseph M. Acaba, Richard R. Arnold, and Dorothy Metcalf-Lindenburger. Barbara Morgan, selected as back-up teacher to Christa McAuliffe in 1985, is considered to be the first Educator astronaut by the media, but she trained as a mission specialist. The Educator Astronaut program is a successor to the Teacher in Space program from the 1980s. Health risks of space travel Astronauts are susceptible to a variety of health risks including decompression sickness, barotrauma, immunodeficiencies, loss of bone and muscle, loss of eyesight, orthostatic intolerance, sleep disturbances, and radiation injury. A variety of large scale medical studies are being conducted in space via the National Space Biomedical Research Institute (NSBRI) to address these issues. Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity Study in which astronauts (including former ISS commanders Leroy Chiao and Gennady Padalka) perform ultrasound scans under the guidance of remote experts to diagnose and potentially treat hundreds of medical conditions in space. This study's techniques are now being applied to cover professional and Olympic sports injuries as well as ultrasound performed by non-expert operators in medical and high school students. It is anticipated that remote guided ultrasound will have application on Earth in emergency and rural care situations, where access to a trained physician is often rare. A 2006 Space Shuttle experiment found that Salmonella typhimurium, a bacterium that can cause food poisoning, became more virulent when cultivated in space. More recently, in 2017, bacteria were found to be more resistant to antibiotics and to thrive in the near-weightlessness of space. Microorganisms have been observed to survive the vacuum of outer space. On 31 December 2012, a NASA-supported study reported that human spaceflight may harm the brain and accelerate the onset of Alzheimer's disease. In October 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, including a human mission to Mars. Over the last decade, flight surgeons and scientists at NASA have seen a pattern of vision problems in astronauts on long-duration space missions. The syndrome, known as visual impairment intracranial pressure (VIIP), has been reported in nearly two-thirds of space explorers after long periods spent aboard the International Space Station (ISS). On 2 November 2017, scientists reported that significant changes in the position and structure of the brain have been found in astronauts who have taken trips in space, based on MRI studies. Astronauts who took longer space trips were associated with greater brain changes. Being in space can be physiologically deconditioning on the body. It can affect the otolith organs and adaptive capabilities of the central nervous system. Zero gravity and cosmic rays can cause many implications for astronauts. In October 2018, NASA-funded researchers found that lengthy journeys into outer space, including travel to the planet Mars, may substantially damage the gastrointestinal tissues of astronauts. The studies support earlier work that found such journeys could significantly damage the brains of astronauts, and age them prematurely. Researchers in 2018 reported, after detecting the presence on the International Space Station (ISS) of five Enterobacter bugandensis bacterial strains, none pathogenic to humans, that microorganisms on ISS should be carefully monitored to continue assuring a medically healthy environment for astronauts. A study by Russian scientists published in April 2019 stated that astronauts facing space radiation could face temporary hindrance of their memory centers. While this does not affect their intellectual capabilities, it temporarily hinders formation of new cells in brain's memory centers. The study conducted by Moscow Institute of Physics and Technology (MIPT) concluded this after they observed that mice exposed to neutron and gamma radiation did not impact the rodents' intellectual capabilities. A 2020 study conducted on the brains of eight male Russian cosmonauts after they returned from long stays aboard the International Space Station showed that long-duration spaceflight causes many physiological adaptions, including macro- and microstructural changes. While scientists still know little about the effects of spaceflight on brain structure, this study showed that space travel can lead to new motor skills (dexterity), but also slightly weaker vision, both of which could possibly be long lasting. It was the first study to provide clear evidence of sensorimotor neuroplasticity, which is the brain's ability to change through growth and reorganization. Food and drink An astronaut on the International Space Station requires about mass of food per meal each day (inclusive of about packaging mass per meal). Space Shuttle astronauts worked with nutritionists to select menus that appealed to their individual tastes. Five months before flight, menus were selected and analyzed for nutritional content by the shuttle dietician. Foods are tested to see how they will react in a reduced gravity environment. Caloric requirements are determined using a basal energy expenditure (BEE) formula. On Earth, the average American uses about of water every day. On board the ISS astronauts limit water use to only about per day. Insignia In Russia, cosmonauts are awarded Pilot-Cosmonaut of the Russian Federation upon completion of their missions, often accompanied with the award of Hero of the Russian Federation. This follows the practice established in the USSR where cosmonauts were usually awarded the title Hero of the Soviet Union. At NASA, those who complete astronaut candidate training receive a silver lapel pin. Once they have flown in space, they receive a gold pin. U.S. astronauts who also have active-duty military status receive a special qualification badge, known as the Astronaut Badge, after participation on a spaceflight. The United States Air Force also presents an Astronaut Badge to its pilots who exceed in altitude. Deaths , eighteen astronauts (fourteen men and four women) have lost their lives during four space flights. By nationality, thirteen were American, four were Russian (Soviet Union), and one was Israeli. , eleven people (all men) have lost their lives training for spaceflight: eight Americans and three Russians. Six of these were in crashes of training jet aircraft, one drowned during water recovery training, and four were due to fires in pure oxygen environments. Astronaut David Scott left a memorial consisting of a statuette titled Fallen Astronaut on the surface of the Moon during his 1971 Apollo 15 mission, along with a list of the names of eight of the astronauts and six cosmonauts known at the time to have died in service. The Space Mirror Memorial, which stands on the grounds of the Kennedy Space Center Visitor Complex, is maintained by the Astronauts Memorial Foundation and commemorates the lives of the men and women who have died during spaceflight and during training in the space programs of the United States. In addition to twenty NASA career astronauts, the memorial includes the names of an X-15 test pilot, a U.S. Air Force officer who died while training for a then-classified military space program, and a civilian spaceflight participant. See also Notes References External links NASA: How to become an astronaut 101 List of International partnership organizations Encyclopedia Astronautica: Phantom cosmonauts collectSPACE: Astronaut appearances calendar spacefacts Spacefacts.de Manned astronautics: facts and figures Astronaut Candidate Brochure online Science occupations 1959 introductions

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

673

https://en.wikipedia.org/wiki/Atomic%20number

Atomic number

The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of every atom of that element. The atomic number uniquely identifies a chemical element. It is identical to the charge number of the nucleus. In an uncharged atom, the atomic number is also equal to the number of electrons. The sum of the atomic number Z and the number of neutrons N gives the mass number A of an atom. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number A. Atoms with the same atomic number but different neutron numbers, and hence different mass numbers, are known as isotopes. A little more than three-quarters of naturally occurring elements exist as a mixture of isotopes (see monoisotopic elements), and the average isotopic mass of an isotopic mixture for an element (called the relative atomic mass) in a defined environment on Earth, determines the element's standard atomic weight. Historically, it was these atomic weights of elements (in comparison to hydrogen) that were the quantities measurable by chemists in the 19th century. The conventional symbol Z comes from the German word 'number', which, before the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table, whose order was then approximately, but not completely, consistent with the order of the elements by atomic weights. Only after 1915, with the suggestion and evidence that this Z number was also the nuclear charge and a physical characteristic of atoms, did the word (and its English equivalent atomic number) come into common use in this context. History The periodic table and a natural number for each element Loosely speaking, the existence or construction of a periodic table of elements creates an ordering of the elements, and so they can be numbered in order. Dmitri Mendeleev claimed that he arranged his first periodic tables (first published on March 6, 1869) in order of atomic weight ("Atomgewicht"). However, in consideration of the elements' observed chemical properties, he changed the order slightly and placed tellurium (atomic weight 127.6) ahead of iodine (atomic weight 126.9). This placement is consistent with the modern practice of ordering the elements by proton number, Z, but that number was not known or suspected at the time. A simple numbering based on periodic table position was never entirely satisfactory, however. Besides the case of iodine and tellurium, later several other pairs of elements (such as argon and potassium, cobalt and nickel) were known to have nearly identical or reversed atomic weights, thus requiring their placement in the periodic table to be determined by their chemical properties. However the gradual identification of more and more chemically similar lanthanide elements, whose atomic number was not obvious, led to inconsistency and uncertainty in the periodic numbering of elements at least from lutetium (element 71) onward (hafnium was not known at this time). The Rutherford-Bohr model and van den Broek In 1911, Ernest Rutherford gave a model of the atom in which a central nucleus held most of the atom's mass and a positive charge which, in units of the electron's charge, was to be approximately equal to half of the atom's atomic weight, expressed in numbers of hydrogen atoms. This central charge would thus be approximately half the atomic weight (though it was almost 25% different from the atomic number of gold , ), the single element from which Rutherford made his guess). Nevertheless, in spite of Rutherford's estimation that gold had a central charge of about 100 (but was element on the periodic table), a month after Rutherford's paper appeared, Antonius van den Broek first formally suggested that the central charge and number of electrons in an atom was exactly equal to its place in the periodic table (also known as element number, atomic number, and symbolized Z). This proved eventually to be the case. Moseley's 1913 experiment The experimental position improved dramatically after research by Henry Moseley in 1913. Moseley, after discussions with Bohr who was at the same lab (and who had used Van den Broek's hypothesis in his Bohr model of the atom), decided to test Van den Broek's and Bohr's hypothesis directly, by seeing if spectral lines emitted from excited atoms fitted the Bohr theory's postulation that the frequency of the spectral lines be proportional to the square of Z. To do this, Moseley measured the wavelengths of the innermost photon transitions (K and L lines) produced by the elements from aluminum (Z = 13) to gold (Z = 79) used as a series of movable anodic targets inside an x-ray tube. The square root of the frequency of these photons increased from one target to the next in an arithmetic progression. This led to the conclusion (Moseley's law) that the atomic number does closely correspond (with an offset of one unit for K-lines, in Moseley's work) to the calculated electric charge of the nucleus, i.e. the element number Z. Among other things, Moseley demonstrated that the lanthanide series (from lanthanum to lutetium inclusive) must have 15 members—no fewer and no more—which was far from obvious from known chemistry at that time. Missing elements After Moseley's death in 1915, the atomic numbers of all known elements from hydrogen to uranium (Z = 92) were examined by his method. There were seven elements (with Z < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time, the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium (Z = 96). The proton and the idea of nuclear electrons In 1915, the reason for nuclear charge being quantized in units of Z, which were now recognized to be the same as the element number, was not understood. An old idea called Prout's hypothesis had postulated that the elements were all made of residues (or "protyles") of the lightest element hydrogen, which in the Bohr-Rutherford model had a single electron and a nuclear charge of one. However, as early as 1907, Rutherford and Thomas Royds had shown that alpha particles, which had a charge of +2, were the nuclei of helium atoms, which had a mass four times that of hydrogen, not two times. If Prout's hypothesis were true, something had to be neutralizing some of the charge of the hydrogen nuclei present in the nuclei of heavier atoms. In 1917, Rutherford succeeded in generating hydrogen nuclei from a nuclear reaction between alpha particles and nitrogen gas, and believed he had proven Prout's law. He called the new heavy nuclear particles protons in 1920 (alternate names being proutons and protyles). It had been immediately apparent from the work of Moseley that the nuclei of heavy atoms have more than twice as much mass as would be expected from their being made of hydrogen nuclei, and thus there was required a hypothesis for the neutralization of the extra protons presumed present in all heavy nuclei. A helium nucleus was presumed to be composed of four protons plus two "nuclear electrons" (electrons bound inside the nucleus) to cancel two of the charges. At the other end of the periodic table, a nucleus of gold with a mass 197 times that of hydrogen was thought to contain 118 nuclear electrons in the nucleus to give it a residual charge of +79, consistent with its atomic number. The discovery of the neutron makes Z the proton number All consideration of nuclear electrons ended with James Chadwick's discovery of the neutron in 1932. An atom of gold now was seen as containing 118 neutrons rather than 118 nuclear electrons, and its positive charge now was realized to come entirely from a content of 79 protons. After 1932, therefore, an element's atomic number Z was also realized to be identical to the proton number of its nuclei. Chemical properties Each element has a specific set of chemical properties as a consequence of the number of electrons present in the neutral atom, which is Z (the atomic number). The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element's electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. Hence, it is the atomic number alone that determines the chemical properties of an element; and it is for this reason that an element can be defined as consisting of any mixture of atoms with a given atomic number. New elements The quest for new elements is usually described using atomic numbers. As of , all elements with atomic numbers 1 to 118 have been observed. Synthesis of new elements is accomplished by bombarding target atoms of heavy elements with ions, such that the sum of the atomic numbers of the target and ion elements equals the atomic number of the element being created. In general, the half-life of a nuclide becomes shorter as atomic number increases, though undiscovered nuclides with certain "magic" numbers of protons and neutrons may have relatively longer half-lives and comprise an island of stability. A hypothetical element composed only of neutrons has also been proposed and would have atomic number 0. See also Effective atomic number Mass number Neutron number Atomic theory Chemical element History of the periodic table List of elements by atomic number Prout's hypothesis References Chemical properties Nuclear physics Atoms Dimensionless numbers of chemistry Numbers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

677

https://en.wikipedia.org/wiki/Ambiguity

Ambiguity

Ambiguity is a type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement whose intended meaning cannot be definitively resolved according to a rule or process with a finite number of steps. (The ambi- part of the term reflects an idea of "two", as in "two meanings".) The concept of ambiguity is generally contrasted with vagueness. In ambiguity, specific and distinct interpretations are permitted (although some may not be immediately obvious), whereas with information that is vague, it is difficult to form any interpretation at the desired level of specificity. Linguistic forms Lexical ambiguity is contrasted with semantic ambiguity. The former represents a choice between a finite number of known and meaningful context-dependent interpretations. The latter represents a choice between any number of possible interpretations, none of which may have a standard agreed-upon meaning. This form of ambiguity is closely related to vagueness. Linguistic ambiguity can be a problem in law, because the interpretation of written documents and oral agreements is often of paramount importance. Lexical ambiguity The lexical ambiguity of a word or phrase pertains to its having more than one meaning in the language to which the word belongs. "Meaning" here refers to whatever should be captured by a good dictionary. For instance, the word "bank" has several distinct lexical definitions, including "financial institution" and "edge of a river". Or consider "apothecary". One could say "I bought herbs from the apothecary". This could mean one actually spoke to the apothecary (pharmacist) or went to the apothecary (pharmacy). The context in which an ambiguous word is used often makes it evident which of the meanings is intended. If, for instance, someone says "I buried $100 in the bank", most people would not think someone used a shovel to dig in the mud. However, some linguistic contexts do not provide sufficient information to disambiguate a used word. Lexical ambiguity can be addressed by algorithmic methods that automatically associate the appropriate meaning with a word in context, a task referred to as word sense disambiguation. The use of multi-defined words requires the author or speaker to clarify their context, and sometimes elaborate on their specific intended meaning (in which case, a less ambiguous term should have been used). The goal of clear concise communication is that the receiver(s) have no misunderstanding about what was meant to be conveyed. An exception to this could include a politician whose "weasel words" and obfuscation are necessary to gain support from multiple constituents with mutually exclusive conflicting desires from their candidate of choice. Ambiguity is a powerful tool of political science. More problematic are words whose senses express closely related concepts. "Good", for example, can mean "useful" or "functional" (That's a good hammer), "exemplary" (She's a good student), "pleasing" (This is good soup), "moral" (a good person versus the lesson to be learned from a story), "righteous", etc. "I have a good daughter" is not clear about which sense is intended. The various ways to apply prefixes and suffixes can also create ambiguity ("unlockable" can mean "capable of being unlocked" or "impossible to lock"). Semantic and syntactic ambiguity Semantic ambiguity occurs when a word, phrase or sentence, taken out of context, has more than one interpretation. In "We saw her duck" (example due to Richard Nordquist), the words "her duck" can refer either to the person's bird (the noun "duck", modified by the possessive pronoun "her"), or to a motion she made (the verb "duck", the subject of which is the objective pronoun "her", object of the verb "saw"). Syntactic ambiguity arises when a sentence can have two (or more) different meanings because of the structure of the sentence—its syntax. This is often due to a modifying expression, such as a prepositional phrase, the application of which is unclear. "He ate the cookies on the couch", for example, could mean that he ate those cookies that were on the couch (as opposed to those that were on the table), or it could mean that he was sitting on the couch when he ate the cookies. "To get in, you will need an entrance fee of $10 or your voucher and your drivers' license." This could mean that you need EITHER ten dollars OR BOTH your voucher and your license. Or it could mean that you need your license AND you need EITHER ten dollars OR a voucher. Only rewriting the sentence, or placing appropriate punctuation can resolve a syntactic ambiguity. For the notion of, and theoretic results about, syntactic ambiguity in artificial, formal languages (such as computer programming languages), see Ambiguous grammar. Usually, semantic and syntactic ambiguity go hand in hand. The sentence "We saw her duck" is also syntactically ambiguous. Conversely, a sentence like "He ate the cookies on the couch" is also semantically ambiguous. Rarely, but occasionally, the different parsings of a syntactically ambiguous phrase result in the same meaning. For example, the command "Cook, cook!" can be parsed as "Cook (noun used as vocative), cook (imperative verb form)!", but also as "Cook (imperative verb form), cook (noun used as vocative)!". It is more common that a syntactically unambiguous phrase has a semantic ambiguity; for example, the lexical ambiguity in "Your boss is a funny man" is purely semantic, leading to the response "Funny ha-ha or funny peculiar?" Spoken language can contain many more types of ambiguities which are called phonological ambiguities, where there is more than one way to compose a set of sounds into words. For example, "ice cream" and "I scream". Such ambiguity is generally resolved according to the context. A mishearing of such, based on incorrectly resolved ambiguity, is called a mondegreen. Metonymy involves referring to one entity by the name of a different but closely related entity (for example, using "wheels" to refer to a car, or "Wall Street" to refer to the stock exchanges located on that street or even the entire US financial sector). In the modern vocabulary of critical semiotics, metonymy encompasses any potentially ambiguous word substitution that is based on contextual contiguity (located close together), or a function or process that an object performs, such as "sweet ride" to refer to a nice car. Metonym miscommunication is considered a primary mechanism of linguistic humor. Philosophy Philosophers (and other users of logic) spend a lot of time and effort searching for and removing (or intentionally adding) ambiguity in arguments because it can lead to incorrect conclusions and can be used to deliberately conceal bad arguments. For example, a politician might say, "I oppose taxes which hinder economic growth", an example of a glittering generality. Some will think they oppose taxes in general because they hinder economic growth. Others may think they oppose only those taxes that they believe will hinder economic growth. In writing, the sentence can be rewritten to reduce possible misinterpretation, either by adding a comma after "taxes" (to convey the first sense) or by changing "which" to "that" (to convey the second sense) or by rewriting it in other ways. The devious politician hopes that each constituent will interpret the statement in the most desirable way, and think the politician supports everyone's opinion. However, the opposite can also be true—an opponent can turn a positive statement into a bad one if the speaker uses ambiguity (intentionally or not). The logical fallacies of amphiboly and equivocation rely heavily on the use of ambiguous words and phrases. In continental philosophy (particularly phenomenology and existentialism), there is much greater tolerance of ambiguity, as it is generally seen as an integral part of the human condition. Martin Heidegger argued that the relation between the subject and object is ambiguous, as is the relation of mind and body, and part and whole. In Heidegger's phenomenology, Dasein is always in a meaningful world, but there is always an underlying background for every instance of signification. Thus, although some things may be certain, they have little to do with Dasein's sense of care and existential anxiety, e.g., in the face of death. In calling his work Being and Nothingness an "essay in phenomenological ontology" Jean-Paul Sartre follows Heidegger in defining the human essence as ambiguous, or relating fundamentally to such ambiguity. Simone de Beauvoir tries to base an ethics on Heidegger's and Sartre's writings (The Ethics of Ambiguity), where she highlights the need to grapple with ambiguity: "as long as there have been philosophers and they have thought, most of them have tried to mask it... And the ethics which they have proposed to their disciples has always pursued the same goal. It has been a matter of eliminating the ambiguity by making oneself pure inwardness or pure externality, by escaping from the sensible world or being engulfed by it, by yielding to eternity or enclosing oneself in the pure moment." Ethics cannot be based on the authoritative certainty given by mathematics and logic, or prescribed directly from the empirical findings of science. She states: "Since we do not succeed in fleeing it, let us, therefore, try to look the truth in the face. Let us try to assume our fundamental ambiguity. It is in the knowledge of the genuine conditions of our life that we must draw our strength to live and our reason for acting". Other continental philosophers suggest that concepts such as life, nature, and sex are ambiguous. Corey Anton has argued that we cannot be certain what is separate from or unified with something else: language, he asserts, divides what is not, in fact, separate. Following Ernest Becker, he argues that the desire to 'authoritatively disambiguate' the world and existence has led to numerous ideologies and historical events such as genocide. On this basis, he argues that ethics must focus on 'dialectically integrating opposites' and balancing tension, rather than seeking a priori validation or certainty. Like the existentialists and phenomenologists, he sees the ambiguity of life as the basis of creativity. Literature and rhetoric In literature and rhetoric, ambiguity can be a useful tool. Groucho Marx's classic joke depends on a grammatical ambiguity for its humor, for example: "Last night I shot an elephant in my pajamas. How he got in my pajamas, I'll never know". Songs and poetry often rely on ambiguous words for artistic effect, as in the song title "Don't It Make My Brown Eyes Blue" (where "blue" can refer to the color, or to sadness). In the narrative, ambiguity can be introduced in several ways: motive, plot, character. F. Scott Fitzgerald uses the latter type of ambiguity with notable effect in his novel The Great Gatsby. Mathematical notation Mathematical notation, widely used in physics and other sciences, avoids many ambiguities compared to expression in natural language. However, for various reasons, several lexical, syntactic and semantic ambiguities remain. Names of functions The ambiguity in the style of writing a function should not be confused with a multivalued function, which can (and should) be defined in a deterministic and unambiguous way. Several special functions still do not have established notations. Usually, the conversion to another notation requires to scale the argument or the resulting value; sometimes, the same name of the function is used, causing confusions. Examples of such underestablished functions: Sinc function Elliptic integral of the third kind; translating elliptic integral form MAPLE to Mathematica, one should replace the second argument to its square, see Talk:Elliptic integral#List of notations; dealing with complex values, this may cause problems. Exponential integral Hermite polynomial Expressions Ambiguous expressions often appear in physical and mathematical texts. It is common practice to omit multiplication signs in mathematical expressions. Also, it is common to give the same name to a variable and a function, for example, . Then, if one sees , there is no way to distinguish whether it means multiplied by , or function evaluated at argument equal to . In each case of use of such notations, the reader is supposed to be able to perform the deduction and reveal the true meaning. Creators of algorithmic languages try to avoid ambiguities. Many algorithmic languages (C++ and Fortran) require the character * as symbol of multiplication. The Wolfram Language used in Mathematica allows the user to omit the multiplication symbol, but requires square brackets to indicate the argument of a function; square brackets are not allowed for grouping of expressions. Fortran, in addition, does not allow use of the same name (identifier) for different objects, for example, function and variable; in particular, the expression f=f(x) is qualified as an error. The order of operations may depend on the context. In most programming languages, the operations of division and multiplication have equal priority and are executed from left to right. Until the last century, many editorials assumed that multiplication is performed first, for example, is interpreted as ; in this case, the insertion of parentheses is required when translating the formulas to an algorithmic language. In addition, it is common to write an argument of a function without parenthesis, which also may lead to ambiguity. In the scientific journal style, one uses roman letters to denote elementary functions, whereas variables are written using italics. For example, in mathematical journals the expression does not denote the sine function, but the product of the three variables , , , although in the informal notation of a slide presentation it may stand for . Commas in multi-component subscripts and superscripts are sometimes omitted; this is also potentially ambiguous notation. For example, in the notation , the reader can only infer from the context whether it means a single-index object, taken with the subscript equal to product of variables , and , or it is an indication to a trivalent tensor. Examples of potentially confusing ambiguous mathematical expressions An expression such as can be understood to mean either or . Often the author's intention can be understood from the context, in cases where only one of the two makes sense, but an ambiguity like this should be avoided, for example by writing or . The expression means in several texts, though it might be thought to mean , since commonly means . Conversely, might seem to mean , as this exponentiation notation usually denotes function iteration: in general, means . However, for trigonometric and hyperbolic functions, this notation conventionally means exponentiation of the result of function application. The expression can be interpreted as meaning ; however, it is more commonly understood to mean . Notations in quantum optics and quantum mechanics It is common to define the coherent states in quantum optics with and states with fixed number of photons with . Then, there is an "unwritten rule": the state is coherent if there are more Greek characters than Latin characters in the argument, and photon state if the Latin characters dominate. The ambiguity becomes even worse, if is used for the states with certain value of the coordinate, and means the state with certain value of the momentum, which may be used in books on quantum mechanics. Such ambiguities easily lead to confusions, especially if some normalized adimensional, dimensionless variables are used. Expression may mean a state with single photon, or the coherent state with mean amplitude equal to 1, or state with momentum equal to unity, and so on. The reader is supposed to guess from the context. Ambiguous terms in physics and mathematics Some physical quantities do not yet have established notations; their value (and sometimes even dimension, as in the case of the Einstein coefficients), depends on the system of notations. Many terms are ambiguous. Each use of an ambiguous term should be preceded by the definition, suitable for a specific case. Just like Ludwig Wittgenstein states in Tractatus Logico-Philosophicus: "...Only in the context of a proposition has a name meaning." A highly confusing term is gain. For example, the sentence "the gain of a system should be doubled", without context, means close to nothing. It may mean that the ratio of the output voltage of an electric circuit to the input voltage should be doubled. It may mean that the ratio of the output power of an electric or optical circuit to the input power should be doubled. It may mean that the gain of the laser medium should be doubled, for example, doubling the population of the upper laser level in a quasi-two level system (assuming negligible absorption of the ground-state). The term intensity is ambiguous when applied to light. The term can refer to any of irradiance, luminous intensity, radiant intensity, or radiance, depending on the background of the person using the term. Also, confusions may be related with the use of atomic percent as measure of concentration of a dopant, or resolution of an imaging system, as measure of the size of the smallest detail which still can be resolved at the background of statistical noise. See also Accuracy and precision and its talk. The Berry paradox arises as a result of systematic ambiguity in the meaning of terms such as "definable" or "nameable". Terms of this kind give rise to vicious circle fallacies. Other terms with this type of ambiguity are: satisfiable, true, false, function, property, class, relation, cardinal, and ordinal. Mathematical interpretation of ambiguity In mathematics and logic, ambiguity can be considered to be an instance of the logical concept of underdetermination—for example, leaves open what the value of X is—while its opposite is a self-contradiction, also called inconsistency, paradoxicalness, or oxymoron, or in mathematics an inconsistent system—such as , which has no solution. Logical ambiguity and self-contradiction is analogous to visual ambiguity and impossible objects, such as the Necker cube and impossible cube, or many of the drawings of M. C. Escher. Constructed language Some languages have been created with the intention of avoiding ambiguity, especially lexical ambiguity. Lojban and Loglan are two related languages which have been created for this, focusing chiefly on syntactic ambiguity as well. The languages can be both spoken and written. These languages are intended to provide a greater technical precision over big natural languages, although historically, such attempts at language improvement have been criticized. Languages composed from many diverse sources contain much ambiguity and inconsistency. The many exceptions to syntax and semantic rules are time-consuming and difficult to learn. Biology In structural biology, ambiguity has been recognized as a problem for studying protein conformations. The analysis of a protein three-dimensional structure consists in dividing the macromolecule into subunits called domains. The difficulty of this task arises from the fact that different definitions of what a domain is can be used (e.g. folding autonomy, function, thermodynamic stability, or domain motions), which sometimes results in a single protein having different—yet equally valid—domain assignments. Christianity and Judaism Christianity and Judaism employ the concept of paradox synonymously with "ambiguity". Many Christians and Jews endorse Rudolf Otto's description of the sacred as 'mysterium tremendum et fascinans', the awe-inspiring mystery which fascinates humans. The orthodox Catholic writer G. K. Chesterton regularly employed paradox to tease out the meanings in common concepts which he found ambiguous or to reveal meaning often overlooked or forgotten in common phrases. (The title of one of his most famous books, Orthodoxy, itself employing such a paradox.) Music In music, pieces or sections which confound expectations and may be or are interpreted simultaneously in different ways are ambiguous, such as some polytonality, polymeter, other ambiguous meters or rhythms, and ambiguous phrasing, or (Stein 2005, p.79) any aspect of music. The music of Africa is often purposely ambiguous. To quote Sir Donald Francis Tovey (1935, p.195), "Theorists are apt to vex themselves with vain efforts to remove uncertainty just where it has a high aesthetic value." Visual art In visual art, certain images are visually ambiguous, such as the Necker cube, which can be interpreted in two ways. Perceptions of such objects remain stable for a time, then may flip, a phenomenon called multistable perception. The opposite of such ambiguous images are impossible objects. Pictures or photographs may also be ambiguous at the semantic level: the visual image is unambiguous, but the meaning and narrative may be ambiguous: is a certain facial expression one of excitement or fear, for instance? Social psychology and the bystander effect In social psychology, ambiguity is a factor used in determining peoples' responses to various situations. High levels of ambiguity in an emergency (e.g. an unconscious man lying on a park bench) make witnesses less likely to offer any sort of assistance, due to the fear that they may have misinterpreted the situation and acted unnecessarily. Alternately, non-ambiguous emergencies (e.g. an injured person verbally asking for help) illicit more consistent intervention and assistance. With regard to the bystander effect, studies have shown that emergencies deemed ambiguous trigger the appearance of the classic bystander effect (wherein more witnesses decrease the likelihood of any of them helping) far more than non-ambiguous emergencies. Computer science In computer science, the SI prefixes kilo-, mega- and giga- were historically used in certain contexts to mean either the first three powers of 1024 (1024, 10242 and 10243) contrary to the metric system in which these units unambiguously mean one thousand, one million, and one billion. This usage is particularly prevalent with electronic memory devices (e.g. DRAM) addressed directly by a binary machine register where a decimal interpretation makes no practical sense. Subsequently, the Ki, Mi, and Gi prefixes were introduced so that binary prefixes could be written explicitly, also rendering k, M, and G unambiguous in texts conforming to the new standard—this led to a new ambiguity in engineering documents lacking outward trace of the binary prefixes (necessarily indicating the new style) as to whether the usage of k, M, and G remains ambiguous (old style) or not (new style). 1 M (where M is ambiguously 1,000,000 or 1,048,576) is less uncertain than the engineering value 1.0e6 (defined to designate the interval 950,000 to 1,050,000). As non-volatile storage devices begin to exceed 1 GB in capacity (where the ambiguity begins to routinely impact the second significant digit), GB and TB almost always mean 109 and 1012 bytes. See also References External links Collection of Ambiguous or Inconsistent/Incomplete Statements Leaving out ambiguities when writing Semantics Mathematical notation Concepts in epistemology Barriers to critical thinking Formal semantics (natural language)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

689

https://en.wikipedia.org/wiki/Asia

Asia

Asia () is Earth's largest and most populous continent, located primarily in the Eastern and Northern Hemispheres. It shares the continental landmass of Eurasia with the continent of Europe, and the continental landmass of Afro-Eurasia with Africa and Europe. Asia covers an area of , about 30% of Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Its 4.7 billion people constituting roughly 60% of the world's population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean. The border of Asia with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. It is somewhat arbitrary and has moved since its first conception in classical antiquity. The division of Eurasia into two continents reflects East–West cultural, linguistic, and ethnic differences, some of which vary on a spectrum rather than with a sharp dividing line. The most commonly accepted boundaries place Asia to the east of the Suez Canal separating it from Africa; and to the east of the Turkish Straits, the Ural Mountains and Ural River, and to the south of the Caucasus Mountains and the Caspian and Black Seas, separating it from Europe. China and India alternated in being the largest economies in the world from 1 to 1800 CE. China was a major economic power and attracted many to the east, and for many the legendary wealth and prosperity of the ancient culture of India personified Asia, attracting European commerce, exploration and colonialism. The accidental discovery of a trans-Atlantic route from Europe to America by Columbus while in search for a route to India demonstrates this deep fascination. The Silk Road became the main east–west trading route in the Asian hinterlands while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism (particularly East Asia) as well as robust population growth during the 20th century, but overall population growth has since fallen. Asia was the birthplace of most of the world's mainstream religions including Hinduism, Zoroastrianism, Judaism, Jainism, Buddhism, Confucianism, Taoism, Christianity, Islam, Sikhism, as well as many other religions. Given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may actually have more to do with human geography than physical geography. Asia varies greatly across and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties and government systems. It also has a mix of many different climates ranging from the equatorial south via the hot desert in the Middle East, temperate areas in the east and the continental centre to vast subarctic and polar areas in Siberia. Definition and boundaries Asia–Africa boundary The boundary between Asia and Africa is the Red Sea, the Gulf of Suez, and the Suez Canal. This makes Egypt a transcontinental country, with the Sinai peninsula in Asia and the remainder of the country in Africa. Asia–Europe boundary The threefold division of the Old World into Europe, Asia and Africa has been in use since the 6th century BC, due to Greek geographers such as Anaximander and Hecataeus. Anaximander placed the boundary between Asia and Europe along the Phasis River (the modern Rioni river) in Georgia of Caucasus (from its mouth by Poti on the Black Sea coast, through the Surami Pass and along the Kura River to the Caspian Sea), a convention still followed by Herodotus in the 5th century BC. During the Hellenistic period, this convention was revised, and the boundary between Europe and Asia was now considered to be the Tanais (the modern Don River). This is the convention used by Roman era authors such as Posidonius, Strabo and Ptolemy. The border between Asia and Europe was historically defined by European academics. The Don River became unsatisfactory to northern Europeans when Peter the Great, king of the Tsardom of Russia, defeating rival claims of Sweden and the Ottoman Empire to the eastern lands, and armed resistance by the tribes of Siberia, synthesized a new Russian Empire extending to the Ural Mountains and beyond, founded in 1721. The major geographical theorist of the empire was a former Swedish prisoner-of-war, taken at the Battle of Poltava in 1709 and assigned to Tobolsk, where he associated with Peter's Siberian official, Vasily Tatishchev, and was allowed freedom to conduct geographical and anthropological studies in preparation for a future book. In Sweden, five years after Peter's death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Ural Mountains as the border of Asia. Tatishchev announced that he had proposed the idea to von Strahlenberg. The latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century. The border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is usually placed along the crest of the Caucasus Mountains, although it is sometimes placed further north. Asia–Oceania boundary The border between Asia and the region of Oceania is usually placed somewhere in the Malay Archipelago. The Maluku Islands in Indonesia are often considered to lie on the border of southeast Asia, with New Guinea, to the east of the islands, being wholly part of Oceania. The terms Southeast Asia and Oceania, devised in the 19th century, have had several vastly different geographic meanings since their inception. The chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the colonial possessions of the various empires there (not all European). Lewis and Wigen assert, "The narrowing of 'Southeast Asia' to its present boundaries was thus a gradual process." Ongoing definition Geographical Asia is a cultural artifact of European conceptions of the world, beginning with the Ancient Greeks, being imposed onto other cultures, an imprecise concept causing endemic contention about what it means. Asia does not exactly correspond to the cultural borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system (Europe, Africa, Asia) on the grounds that there is no substantial physical separation between them. For example, Sir Barry Cunliffe, the emeritus professor of European archeology at Oxford, argues that Europe has been geographically and culturally merely "the western excrescence of the continent of Asia". Geographically, Asia is the major eastern constituent of the continent of Eurasia with Europe being a northwestern peninsula of the landmass. Asia, Europe and Africa make up a single continuous landmass—Afro-Eurasia (except for the Suez Canal)—and share a common continental shelf. Almost all of Europe and a major part of Asia sit atop the Eurasian Plate, adjoined on the south by the Arabian and Indian Plate and with the easternmost part of Siberia (east of the Chersky Range) on the North American Plate. Etymology The idea of a place called "Asia" was originally a concept of Greek civilization, though this might not correspond to the entire continent currently known by that name. The English word comes from Latin literature, where it has the same form, "Asia". Whether "Asia" in other languages comes from Latin of the Roman Empire is much less certain, and the ultimate source of the Latin word is uncertain, though several theories have been published. One of the first classical writers to use Asia as a name of the whole continent was Pliny. This metonymical change in meaning is common and can be observed in some other geographical names, such as Scandinavia (from Scania). Bronze Age Before Greek poetry, the Aegean Sea area was in a Greek Dark Age, at the beginning of which syllabic writing was lost and alphabetic writing had not begun. Prior to then in the Bronze Age the records of the Assyrian Empire, the Hittite Empire and the various Mycenaean states of Greece mention a region undoubtedly Asia, certainly in Anatolia, including if not identical to Lydia. These records are administrative and do not include poetry. The Mycenaean states were destroyed about 1200 BCE by unknown agents, though one school of thought assigns the Dorian invasion to this time. The burning of the palaces caused the clay tablets holding the Mycenaean administrative records to be preserved by baking. These tablets were written in a Greek syllabic script called Linear B. This script was deciphered by a number of interested parties, most notably by a young World War II cryptographer, Michael Ventris, subsequently assisted by the scholar, John Chadwick. A major cache discovered by Carl Blegen at the site of ancient Pylos included hundreds of male and female names formed by different methods. Some of these are of women held in servitude (as study of the society implied by the content reveals). They were used in trades, such as cloth-making, and usually came with children. The epithet lawiaiai, "captives", associated with some of them identifies their origin. Some are ethnic names. One in particular, aswiai, identifies "women of Asia". Perhaps they were captured in Asia, but some others, Milatiai, appear to have been of Miletus, a Greek colony, which would not have been raided for slaves by Greeks. Chadwick suggests that the names record the locations where these foreign women were purchased. The name is also in the singular, Aswia, which refers both to the name of a country and to a female from there. There is a masculine form, . This Aswia appears to have been a remnant of a region known to the Hittites as Assuwa, centered on Lydia, or "Roman Asia". This name, Assuwa, has been suggested as the origin for the name of the continent "Asia". The Assuwa league was a confederation of states in western Anatolia, defeated by the Hittites under Tudhaliya I around 1400 BCE. Classical antiquity Latin Asia and Greek Ἀσία appear to be the same word. Roman authors translated Ἀσία as Asia. The Romans named a province Asia, located in western Anatolia (in modern-day Turkey). There was an Asia Minor and an Asia Major located in modern-day Iraq. As the earliest evidence of the name is Greek, it is likely circumstantially that Asia came from Ἀσία, but ancient transitions, due to the lack of literary contexts, are difficult to catch in the act. The most likely vehicles were the ancient geographers and historians, such as Herodotus, who were all Greek. Ancient Greek certainly evidences early and rich uses of the name. The first continental use of Asia is attributed to Herodotus (about 440 BCE), not because he innovated it, but because his Histories are the earliest surviving prose to describe it in any detail. He defines it carefully, mentioning the previous geographers whom he had read, but whose works are now missing. By it he means Anatolia and the Persian Empire, in contrast to Greece and Egypt. Herodotus comments that he is puzzled as to why three women's names were "given to a tract which is in reality one" (Europa, Asia, and Libya, referring to Africa), stating that most Greeks assumed that Asia was named after the wife of Prometheus (i.e. Hesione), but that the Lydians say it was named after Asies, son of Cotys, who passed the name on to a tribe at Sardis. In Greek mythology, "Asia" (Ἀσία) or "Asie" (Ἀσίη) was the name of a "Nymph or Titan goddess of Lydia". In ancient Greek religion, places were under the care of female divinities, parallel to guardian angels. The poets detailed their doings and generations in allegoric language salted with entertaining stories, which subsequently playwrights transformed into classical Greek drama and became "Greek mythology". For example, Hesiod mentions the daughters of Tethys and Ocean, among whom are a "holy company", "who with the Lord Apollo and the Rivers have youths in their keeping". Many of these are geographic: Doris, Rhodea, Europa, Asia. Hesiod explains: The Iliad (attributed by the ancient Greeks to Homer) mentions two Phrygians (the tribe that replaced the Luvians in Lydia) in the Trojan War named Asios (an adjective meaning "Asian"); and also a marsh or lowland containing a marsh in Lydia as . According to many Muslims, the term came from Ancient Egypt's Queen Asiya, the adoptive mother of Moses. History The history of Asia can be seen as the distinct histories of several peripheral coastal regions: East Asia, South Asia, Southeast Asia and the Middle East, linked by the interior mass of the Central Asian steppes. The coastal periphery was home to some of the world's earliest known civilizations, each of them developing around fertile river valleys. The civilizations in Mesopotamia, the Indus Valley and the Yellow River shared many similarities. These civilizations may well have exchanged technologies and ideas such as mathematics and the wheel. Other innovations, such as writing, seem to have been developed individually in each area. Cities, states and empires developed in these lowlands. The central steppe region had long been inhabited by horse-mounted nomads who could reach all areas of Asia from the steppes. The earliest postulated expansion out of the steppe is that of the Indo-Europeans, who spread their languages into the Middle East, South Asia, and the borders of China, where the Tocharians resided. The northernmost part of Asia, including much of Siberia, was largely inaccessible to the steppe nomads, owing to the dense forests, climate and tundra. These areas remained very sparsely populated. The center and the peripheries were mostly kept separated by mountains and deserts. The Caucasus and Himalaya mountains and the Karakum and Gobi deserts formed barriers that the steppe horsemen could cross only with difficulty. While the urban city dwellers were more advanced technologically and socially, in many cases they could do little in a military aspect to defend against the mounted hordes of the steppe. However, the lowlands did not have enough open grasslands to support a large horsebound force; for this and other reasons, the nomads who conquered states in China, India, and the Middle East often found themselves adapting to the local, more affluent societies. The Islamic Caliphate's defeats of the Byzantine and Persian empires led to West Asia and southern parts of Central Asia and western parts of South Asia under its control during its conquests of the 7th century. The Mongol Empire conquered a large part of Asia in the 13th century, an area extending from China to Europe. Before the Mongol invasion, Song dynasty reportedly had approximately 120 million citizens; the 1300 census which followed the invasion reported roughly 60 million people. The Black Death, one of the most devastating pandemics in human history, is thought to have originated in the arid plains of central Asia, where it then travelled along the Silk Road. The Russian Empire began to expand into Asia from the 17th century, and would eventually take control of all of Siberia and most of Central Asia by the end of the 19th century. The Ottoman Empire controlled Anatolia, most of the Middle East, North Africa and the Balkans from the mid 16th century onwards. In the 17th century, the Manchu conquered China and established the Qing dynasty. The Islamic Mughal Empire and the Hindu Maratha Empire controlled much of India in the 16th and 18th centuries respectively. The Empire of Japan controlled most of East Asia and much of Southeast Asia, New Guinea and the Pacific islands until the end of World War II. Geography and climate Asia is the largest continent on Earth. It covers 9% of the Earth's total surface area (or 30% of its land area), and has the longest coastline, at . Asia is generally defined as comprising the eastern four-fifths of Eurasia. It is located to the east of the Suez Canal and the Ural Mountains, and south of the Caucasus Mountains (or the Kuma–Manych Depression) and the Caspian and Black Seas. It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean and on the north by the Arctic Ocean. Asia is subdivided into 49 countries, five of them (Georgia, Azerbaijan, Russia, Kazakhstan and Turkey) are transcontinental countries lying partly in Europe. Geographically, Russia is partly in Asia, but is considered a European nation, both culturally and politically. The Gobi Desert is in Mongolia and the Arabian Desert stretches across much of the Middle East. The Yangtze River in China is the longest river in the continent. The Himalayas between Nepal and China is the tallest mountain range in the world. Tropical rainforests stretch across much of southern Asia and coniferous and deciduous forests lie farther north. Main regions There are various approaches to the regional division of Asia. The following subdivision into regions is used, among others, by the UN statistics agency UNSD. This division of Asia into regions by the United Nations is done solely for statistical reasons and does not imply any assumption about political or other affiliations of countries and territories. North Asia (Siberia) Central Asia (The 'stans) Western Asia (The Middle East or Near East) South Asia (Indian subcontinent) East Asia (Far East) Southeast Asia (East Indies and Indochina) Climate Asia has extremely diverse climate features. Climates range from arctic and subarctic in Siberia to tropical in southern India and Southeast Asia. It is moist across southeast sections, and dry across much of the interior. Some of the largest daily temperature ranges on Earth occur in western sections of Asia. The monsoon circulation dominates across southern and eastern sections, due to the presence of the Himalayas forcing the formation of a thermal low which draws in moisture during the summer. Southwestern sections of the continent are hot. Siberia is one of the coldest places in the Northern Hemisphere, and can act as a source of arctic air masses for North America. The most active place on Earth for tropical cyclone activity lies northeast of the Philippines and south of Japan. A survey carried out in 2010 by global risk analysis farm Maplecroft identified 16 countries that are extremely vulnerable to climate change. Each nation's vulnerability was calculated using 42 socio, economic and environmental indicators, which identified the likely climate change impacts during the next 30 years. The Asian countries of Bangladesh, India, the Philippines, Vietnam, Thailand, Pakistan, China and Sri Lanka were among the 16 countries facing extreme risk from climate change. Some shifts are already occurring. For example, in tropical parts of India with a semi-arid climate, the temperature increased by 0.4 °C between 1901 and 2003. A 2013 study by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) aimed to find science-based, pro-poor approaches and techniques that would enable Asia's agricultural systems to cope with climate change, while benefitting poor and vulnerable farmers. The study's recommendations ranged from improving the use of climate information in local planning and strengthening weather-based agro-advisory services, to stimulating diversification of rural household incomes and providing incentives to farmers to adopt natural resource conservation measures to enhance forest cover, replenish groundwater and use renewable energy. The ten countries of the Association of Southeast Asian Nations (ASEAN) - Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam - are among the most vulnerable to the effects of climate change in the world, however, ASEAN's climate mitigation efforts are not commensurate with the climate threats and risks it faces. Economy Asia has the largest continental economy by both GDP Nominal and PPP in the world, and is the fastest growing economic region. , the largest economies in Asia are China, Japan, India, South Korea, Indonesia and Turkey based on GDP in both nominal and PPP. Based on Global Office Locations 2011, Asia dominated the office locations with 4 of the top 5 being in Asia: Hong Kong, Singapore, Tokyo and Seoul. Around 68 percent of international firms have an office in Hong Kong. In the late 1990s and early 2000s, the economies of China and India have been growing rapidly, both with an average annual growth rate of more than 8%. Other recent very-high-growth nations in Asia include Israel, Malaysia, Indonesia, Bangladesh, Thailand, Vietnam, and the Philippines, and mineral-rich nations such as Kazakhstan, Turkmenistan, Iran, Brunei, the United Arab Emirates, Qatar, Kuwait, Saudi Arabia, Bahrain and Oman. According to economic historian Angus Maddison in his book The World Economy: A Millennial Perspective, India had the world's largest economy during 0 BCE and 1000 BCE. Historically, India was the largest economy in the world for most of the two millennia from the 1st until 19th century, contributing 25% of the world's industrial output. China was the largest and most advanced economy on earth for much of recorded history and shared the mantle with India. For several decades in the late twentieth century Japan was the largest economy in Asia and second-largest of any single nation in the world, after surpassing the Soviet Union (measured in net material product) in 1990 and Germany in 1968. (NB: A number of supernational economies are larger, such as the European Union (EU), the North American Free Trade Agreement (NAFTA) or APEC). This ended in 2010 when China overtook Japan to become the world's second largest economy. In the late 1980s and early 1990s, Japan's GDP was almost as large (current exchange rate method) as that of the rest of Asia combined. In 1995, Japan's economy nearly equaled that of the US as the largest economy in the world for a day, after the Japanese currency reached a record high of 79 yen/US$. Economic growth in Asia since World War II to the 1990s had been concentrated in Japan as well as the four regions of South Korea, Taiwan, Hong Kong and Singapore located in the Pacific Rim, known as the Asian tigers, which have now all received developed country status, having the highest GDP per capita in Asia. It is forecasted that India will overtake Japan in terms of nominal GDP by 2025. By 2027, according to Goldman Sachs, China will have the largest economy in the world. Several trade blocs exist, with the most developed being the Association of Southeast Asian Nations. Asia is the largest continent in the world by a considerable margin, and it is rich in natural resources, such as petroleum, forests, fish, water, rice, copper and silver. Manufacturing in Asia has traditionally been strongest in East and Southeast Asia, particularly in China, Taiwan, South Korea, Japan, India, the Philippines, and Singapore. Japan and South Korea continue to dominate in the area of multinational corporations, but increasingly the PRC and India are making significant inroads. Many companies from Europe, North America, South Korea and Japan have operations in Asia's developing countries to take advantage of its abundant supply of cheap labour and relatively developed infrastructure. According to Citigroup 9 of 11 Global Growth Generators countries came from Asia driven by population and income growth. They are Bangladesh, China, India, Indonesia, Iraq, Mongolia, the Philippines, Sri Lanka and Vietnam. Asia has three main financial centers: Hong Kong, Tokyo and Singapore. Call centers and business process outsourcing (BPOs) are becoming major employers in India and the Philippines due to the availability of a large pool of highly skilled, English-speaking workers. The increased use of outsourcing has assisted the rise of India and the China as financial centers. Due to its large and extremely competitive information technology industry, India has become a major hub for outsourcing. Trade between Asian countries and countries on other continents is largely carried out on the sea routes that are important for Asia. Individual main routes have emerged from this. The main route leads from the Chinese coast south via Hanoi to Jakarta, Singapore and Kuala Lumpur through the Strait of Malacca via the Sri Lankan Colombo to the southern tip of India via Malé to East Africa Mombasa, from there to Djibouti, then through the Red Sea over the Suez Canal into Mediterranean, there via Haifa, Istanbul and Athens to the upper Adriatic to the northern Italian hub of Trieste with its rail connections to Central and Eastern Europe or further to Barcelona and around Spain and France to the European northern ports. A far smaller part of the goods traffic runs via South Africa to Europe. A particularly significant part of the Asian goods traffic is carried out across the Pacific towards Los Angeles and Long Beach. In contrast to the sea routes, the Silk Road via the land route to Europe is on the one hand still under construction and on the other hand is much smaller in terms of scope. Intra-Asian trade, including sea trade, is growing rapidly. In 2010, Asia had 3.3 million millionaires (people with net worth over US$1 million excluding their homes), slightly below North America with 3.4 million millionaires. Last year Asia had toppled Europe. Citigroup in The Wealth Report 2012 stated that Asian centa-millionaire overtook North America's wealth for the first time as the world's "economic center of gravity" continued moving east. At the end of 2011, there were 18,000 Asian people mainly in Southeast Asia, China and Japan who have at least $100 million in disposable assets, while North America with 17,000 people and Western Europe with 14,000 people. Tourism With growing Regional Tourism with domination of Chinese visitors, MasterCard has released Global Destination Cities Index 2013 with 10 of 20 are dominated by Asia and Pacific Region Cities and also for the first time a city of a country from Asia (Bangkok) set in the top-ranked with 15.98 international visitors. Demographics East Asia had by far the strongest overall Human Development Index (HDI) improvement of any region in the world, nearly doubling average HDI attainment over the past 40 years, according to the report's analysis of health, education and income data. China, the second highest achiever in the world in terms of HDI improvement since 1970, is the only country on the "Top 10 Movers" list due to income rather than health or education achievements. Its per capita income increased a stunning 21-fold over the last four decades, also lifting hundreds of millions out of income poverty. Yet it was not among the region's top performers in improving school enrollment and life expectancy. Nepal, a South Asian country, emerges as one of the world's fastest movers since 1970 mainly due to health and education achievements. Its present life expectancy is 25 years longer than in the 1970s. More than four of every five children of school age in Nepal now attend primary school, compared to just one in five 40 years ago. Hong Kong ranked highest among the countries grouped on the HDI (number 7 in the world, which is in the "very high human development" category), followed by Singapore (9), Japan (19) and South Korea (22). Afghanistan (155) ranked lowest amongst Asian countries out of the 169 countries assessed. Languages Asia is home to several language families and many language isolates. Most Asian countries have more than one language that is natively spoken. For instance, according to Ethnologue, more than 600 languages are spoken in Indonesia, more than 800 languages spoken in India, and more than 100 are spoken in the Philippines. China has many languages and dialects in different provinces. Religions Many of the world's major religions have their origins in Asia, including the five most practiced in the world (excluding irreligion), which are Christianity, Islam, Hinduism, Chinese folk religion (classified as Confucianism and Taoism), and Buddhism respectively. Asian mythology is complex and diverse. The story of the Great Flood for example, as presented to Jews in the Hebrew Bible in the narrative of Noah—and later to Christians in the Old Testament, and to Muslims in the Quran—is earliest found in Mesopotamian mythology, in the Enûma Eliš and Epic of Gilgamesh. Hindu mythology similarly tells about an avatar of Vishnu in the form of a fish who warned Manu of a terrible flood. Ancient Chinese mythology also tells of a Great Flood spanning generations, one that required the combined efforts of emperors and divinities to control. Abrahamic The Abrahamic religions including Judaism, Christianity, Islam, Druze faith, and Baháʼí Faith originated in West Asia. Judaism, the oldest of the Abrahamic faiths, is practiced primarily in Israel, the indigenous homeland and historical birthplace of the Hebrew nation: which today consists both of those Jews who remained in the Middle East and those who returned from diaspora in Europe, North America, and other regions; though various diaspora communities persist worldwide. Jews are the predominant ethnic group in Israel (75.6%) numbering at about 6.1 million, although the levels of adherence to Jewish religion vary. Outside of Israel there are small ancient Jewish communities in Turkey (17,400), Azerbaijan (9,100), Iran (8,756), India (5,000) and Uzbekistan (4,000), among many other places. In total, there are 14.4–17.5 million (2016, est.) Jews alive in the world today, making them one of the smallest Asian minorities, at roughly 0.3 to 0.4 percent of the total population of the continent. Christianity is a widespread religion in Asia with more than 286 million adherents according to Pew Research Center in 2010, and nearly 364 million according to Britannica Book of the Year 2014. Constituting around 12.6% of the total population of Asia. In the Philippines and East Timor, Roman Catholicism is the predominant religion; it was introduced by the Spaniards and the Portuguese, respectively. In Armenia and Georgia, Eastern Orthodoxy is the predominant religion. In the Middle East, such as in the Levant, Anatolia and Fars, Syriac Christianity (Church of the East) and Oriental Orthodoxy are prevalent minority denominations, which are both Eastern Christian sects mainly adhered to Assyrian people or Syriac Christians. Vibrant indigenous minorities in Western Asia are adhering to the Eastern Catholic Churches and Eastern Orthodoxy. Saint Thomas Christians in India trace their origins to the evangelistic activity of Thomas the Apostle in the 1st century. Significant Christian communities also found in Central Asia, South Asia, Southeast Asia and East Asia. Islam, which originated in the Hejaz located in modern-day Saudi Arabia, is the second largest and most widely-spread religion in Asia with at least 1 billion Muslims constituting around 23.8% of the total population of Asia. With 12.7% of the world Muslim population, the country currently with the largest Muslim population in the world is Indonesia, followed by Pakistan (11.5%), India (10%), Bangladesh, Iran and Turkey. Mecca, Medina and Jerusalem are the three holiest cities for Islam in all the world. The Hajj and Umrah attract large numbers of Muslim devotees from all over the world to Mecca and Medina. Iran is the largest Shi'a country. The Druze Faith or Druzism originated in Western Asia, is a monotheistic religion based on the teachings of figures like Hamza ibn-'Ali ibn-Ahmad and Al-Hakim bi-Amr Allah, and Greek philosophers such as Plato and Aristotle. The number of Druze people worldwide is around one million, with about 45% to 50% live in Syria, 35% to 40% live in Lebanon, and less than 10% live in Israel, with recently there has been a growing Druze diaspora. The Baháʼí Faith originated in Asia, in Iran (Persia), and spread from there to the Ottoman Empire, Central Asia, India, and Burma during the lifetime of Bahá'u'lláh. Since the middle of the 20th century, growth has particularly occurred in other Asian countries, because Baháʼí activities in many Muslim countries has been severely suppressed by authorities. Lotus Temple is a big Baháʼí Temple in India. Indian and East Asian religions Almost all Asian religions have philosophical character and Asian philosophical traditions cover a large spectrum of philosophical thoughts and writings. Indian philosophy includes Hindu philosophy and Buddhist philosophy. They include elements of nonmaterial pursuits, whereas another school of thought from India, Cārvāka, preached the enjoyment of the material world. The religions of Hinduism, Buddhism, Jainism and Sikhism originated in India, South Asia. In East Asia, particularly in China and Japan, Confucianism, Taoism and Zen Buddhism took shape. , Hinduism has around 1.1 billion adherents. The faith represents around 25% of Asia's population and is the largest religion in Asia. However, it is mostly concentrated in South Asia. Over 80% of the populations of both India and Nepal adhere to Hinduism, alongside significant communities in Bangladesh, Pakistan, Bhutan, Sri Lanka and Bali, Indonesia. Many overseas Indians in countries such as Burma, Singapore and Malaysia also adhere to Hinduism. Buddhism has a great following in mainland Southeast Asia and East Asia. Buddhism is the religion of the majority of the populations of Cambodia (96%), Thailand (95%), Burma (80–89%), Japan (36–96%), Bhutan (75–84%), Sri Lanka (70%), Laos (60–67%) and Mongolia (53–93%). Large Buddhist populations also exist in Singapore (33–51%), Taiwan (35–93%), South Korea (23–50%), Malaysia (19–21%), Nepal (9–11%), Vietnam (10–75%), China (20–50%), North Korea (2–14%), and small communities in India and Bangladesh. The Communist-governed countries of China, Vietnam and North Korea are officially atheist, thus the number of Buddhists and other religious adherents may be under-reported. Jainism is found mainly in India and in overseas Indian communities such as the United States and Malaysia. Sikhism is found in Northern India and amongst overseas Indian communities in other parts of Asia, especially Southeast Asia. Confucianism is found predominantly in Mainland China, South Korea, Taiwan and in overseas Chinese populations. Taoism is found mainly in Mainland China, Taiwan, Malaysia and Singapore. In many Chinese communities, Taoism is easily syncretized with Mahayana Buddhism, thus exact religious statistics are difficult to obtain and may be understated or overstated. Modern conflicts Some of the events pivotal in the Asia territory related to the relationship with the outside world in the post-Second World War were: The Partition of India The Chinese Civil War The Kashmir conflict The Balochistan Conflict The Naxalite–Maoist insurgency in India The Korean War The French-Indochina War The Vietnam War The Indonesia–Malaysia confrontation The 1959 Tibetan uprising The Sino-Vietnamese War The Bangladesh Liberation War The Yom Kippur War The Xinjiang conflict The Iranian Revolution The Soviet–Afghan War The Iran–Iraq War The Cambodian Killing Fields The Insurgency in Laos The Lebanese Civil War The Sri Lankan Civil War The 1988 Maldives coup d'état The Dissolution of the Soviet Union The Gulf War The Nepalese Civil War The Indo-Pakistani wars and conflicts The West Papua conflict The First Nagorno-Karabakh War The 1989 Tiananmen Square protests The Indonesian occupation of East Timor The 1999 Pakistani coup d'état The War in Afghanistan The Iraq War The South Thailand insurgency The 2006 Thai coup d'état The Burmese Civil War The Saffron Revolution The Kurdish-Turkish conflict The Arab Spring The Arab–Israeli conflict The Syrian Civil War The Sino-Indian War The 2014 Thai coup d'état The Moro conflict in the Philippines The Islamic State of Iraq and the Levant The Turkish invasion of Syria The Rohingya crisis in Myanmar The Saudi Arabian-led intervention in Yemen The Hong Kong protests The 2020 China–India skirmishes The 1969 inter-ethnic violence in Kuala Lumpur Culture Nobel prizes The polymath Rabindranath Tagore, a Bengali poet, dramatist, and writer from Santiniketan, now in West Bengal, India, became in 1913 the first Asian Nobel laureate. He won his Nobel Prize in Literature for notable impact his prose works and poetic thought had on English, French, and other national literatures of Europe and the Americas. He is also the writer of the national anthems of Bangladesh and India. Other Asian writers who won Nobel Prize for literature include Yasunari Kawabata (Japan, 1968), Kenzaburō Ōe (Japan, 1994), Gao Xingjian (China, 2000), Orhan Pamuk (Turkey, 2006), and Mo Yan (China, 2012). Some may consider the American writer, Pearl S. Buck, an honorary Asian Nobel laureate, having spent considerable time in China as the daughter of missionaries, and based many of her novels, namely The Good Earth (1931) and The Mother (1933), as well as the biographies of her parents for their time in China, The Exile and Fighting Angel, all of which earned her the Literature prize in 1938. Also, Mother Teresa of India and Shirin Ebadi of Iran were awarded the Nobel Peace Prize for their significant and pioneering efforts for democracy and human rights, especially for the rights of women and children. Ebadi is the first Iranian and the first Muslim woman to receive the prize. Another Nobel Peace Prize winner is Aung San Suu Kyi from Burma for her peaceful and non-violent struggle under a military dictatorship in Burma. She is a nonviolent pro-democracy activist and leader of the National League for Democracy in Burma (Myanmar) and a noted prisoner of conscience. She is a Buddhist and was awarded the Nobel Peace Prize in 1991. Chinese dissident Liu Xiaobo was awarded the Nobel Peace Prize for "his long and non-violent struggle for fundamental human rights in China" on 8 October 2010. He is the first Chinese citizen to be awarded a Nobel Prize of any kind while residing in China. In 2014, Kailash Satyarthi from India and Malala Yousafzai from Pakistan were awarded the Nobel Peace Prize "for their struggle against the suppression of children and young people and for the right of all children to education". Sir C.V. Raman is the first Asian to get a Nobel prize in Sciences. He won the Nobel Prize in Physics "for his work on the scattering of light and for the discovery of the effect named after him". Japan has won the most Nobel Prizes of any Asian nation with 24 followed by India which has won 13. Amartya Sen, (born 3 November 1933) is an Indian economist who was awarded the 1998 Nobel Memorial Prize in Economic Sciences for his contributions to welfare economics and social choice theory, and for his interest in the problems of society's poorest members. Other Asian Nobel Prize winners include Subrahmanyan Chandrasekhar, Abdus Salam, Malala Yousafzai, Robert Aumann, Menachem Begin, Aaron Ciechanover, Avram Hershko, Daniel Kahneman, Shimon Peres, Yitzhak Rabin, Ada Yonath, Yasser Arafat, José Ramos-Horta and Bishop Carlos Filipe Ximenes Belo of Timor Leste, Kim Dae-jung, and 13 Japanese scientists. Most of the said awardees are from Japan and Israel except for Chandrasekhar and Raman (India), Abdus Salam and Malala Yousafzai, (Pakistan), Arafat (Palestinian Territories), Kim (South Korea), and Horta and Belo (Timor Leste). In 2006, Dr. Muhammad Yunus of Bangladesh was awarded the Nobel Peace Prize for the establishment of Grameen Bank, a community development bank that lends money to poor people, especially women in Bangladesh. Dr. Yunus received his PhD in economics from Vanderbilt University, United States. He is internationally known for the concept of micro credit which allows poor and destitute people with little or no collateral to borrow money. The borrowers typically pay back money within the specified period and the incidence of default is very low. The Dalai Lama has received approximately eighty-four awards over his spiritual and political career. On 22 June 2006, he became one of only four people ever to be recognized with Honorary Citizenship by the Governor General of Canada. On 28 May 2005, he received the Christmas Humphreys Award from the Buddhist Society in the United Kingdom. Most notable was the Nobel Peace Prize, presented in Oslo, Norway on 10 December 1989. Political geography Within the above-mentioned states are several partially recognized countries with limited to no international recognition. None of them are members of the UN: See also References to articles: Subregions of Asia Special topics: Asian Century Asian cuisine Asian furniture Asian Games Asia-Pacific Asian Para Games Asian Monetary Unit Asian people Eastern world Eurasia Far East East Asia Southeast Asia South Asia Central Asia Western Asia North Asia Fauna of Asia Flags of Asia Middle East Eastern Mediterranean Levant Near East Pan-Asianism Lists: List of cities in Asia List of metropolitan areas in Asia by population List of sovereign states and dependent territories in Asia Projects Asian Highway Network Trans-Asian Railway Notes References Bibliography Further reading Embree, Ainslie T., ed. Encyclopedia of Asian history (1988) vol. 1 online; vol 2 online; vol 3 online; vol 4 online Higham, Charles. Encyclopedia of Ancient Asian Civilizations. Facts on File library of world history. New York: Facts On File, 2004. Kamal, Niraj. "Arise Asia: Respond to White Peril". New Delhi: Wordsmith, 2002, Kapadia, Feroz, and Mandira Mukherjee. Encyclopaedia of Asian Culture and Society. New Delhi: Anmol Publications, 1999. Levinson, David, and Karen Christensen, eds. Encyclopedia of Modern Asia. (6 vol. Charles Scribner's Sons, 2002). External links Continents

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

700

https://en.wikipedia.org/wiki/Arthur%20Schopenhauer

Arthur Schopenhauer

Arthur Schopenhauer ( , ; 22 February 1788 – 21 September 1860) was a German philosopher. He is best known for his 1818 work The World as Will and Representation (expanded in 1844), which characterizes the phenomenal world as the product of a blind noumenal will. Building on the transcendental idealism of Immanuel Kant, Schopenhauer developed an atheistic metaphysical and ethical system that rejected the contemporaneous ideas of German idealism. He was among the first thinkers in Western philosophy to share and affirm significant tenets of Indian philosophy, such as asceticism, denial of the self, and the notion of the world-as-appearance. His work has been described as an exemplary manifestation of philosophical pessimism. Though his work failed to garner substantial attention during his lifetime, Schopenhauer had a posthumous impact across various disciplines, including philosophy, literature, and science. His writing on aesthetics, morality, and psychology have influenced many thinkers and artists. Those who have cited his influence include philosophers Emil Cioran, Friedrich Nietzsche and Ludwig Wittgenstein, scientists Erwin Schrödinger and Albert Einstein, psychoanalysts Sigmund Freud and Carl Jung, writers Leo Tolstoy, Herman Melville, Thomas Mann, Hermann Hesse, Machado de Assis, Jorge Luis Borges, Marcel Proust and Samuel Beckett, and composers Richard Wagner, Johannes Brahms, Arnold Schoenberg and Gustav Mahler. Life Early life Arthur Schopenhauer was born on February 22, 1788, in Danzig (then part of the Polish–Lithuanian Commonwealth; present-day Gdańsk, Poland) on Heiligegeistgasse (present day Św. Ducha 47), the son of Johanna Schopenhauer (née Trosiener; 1766–1838) and Heinrich Floris Schopenhauer (1747–1805), both descendants of wealthy German-Dutch patrician families. Neither of them was very religious; both supported the French Revolution, and were republicans, cosmopolitans and Anglophiles. When Danzig became part of Prussia in 1793, Heinrich moved to Hamburg—a free city with a republican constitution. His firm continued trading in Danzig where most of their extended families remained. Adele, Arthur's only sibling, was born on July 12, 1797. In 1797, Arthur was sent to Le Havre to live with the family of his father's business associate, Grégoire de Blésimaire. He seemed to enjoy his two-year stay there, learning to speak French and fostering a life-long friendship with Jean Anthime Grégoire de Blésimaire. As early as 1799, Arthur started playing the flute. In 1803, he accompanied his parents on a European tour of Holland, Britain, France, Switzerland, Austria and Prussia. Viewed as primarily a pleasure tour, Heinrich used the opportunity to visit some of his business associates abroad. Heinrich offered Arthur a choice: he could stay at home and start preparations for university, or he could travel with them and continue his merchant education. Arthur chose to travel with them. He deeply regretted his choice later because the merchant training was very tedious. He spent twelve weeks of the tour attending school in Wimbledon, where he was disillusioned by strict and intellectually shallow Anglican religiosity. He continued to sharply criticize Anglican religiosity later in life despite his general Anglophilia. He was also under pressure from his father, who became very critical of his educational results. In 1805, Heinrich drowned in a canal near their home in Hamburg. Although it was possible that his death was accidental, his wife and son believed that it was suicide. He was prone to anxiety and depression; each becoming more pronounced later in his life. Heinrich had become so fussy, even his wife started to doubt his mental health. "There was, in the father's life, some dark and vague source of fear which later made him hurl himself to his death from the attic of his house in Hamburg." Arthur showed similar moodiness during his youth and often acknowledged that he inherited it from his father. There were other instances of serious mental health history on his father's side of the family. Despite his hardship, Schopenhauer liked his father and later referred to him in a positive light. Heinrich Schopenhauer left the family with a significant inheritance that was split in three among Johanna and the children. Arthur Schopenhauer was entitled to control of his part when he reached the age of majority. He invested it conservatively in government bonds and earned annual interest that was more than double the salary of a university professor. After quitting his merchant apprenticeship, with some encouragement from his mother, he dedicated himself to studies at the Ernestine Gymnasium, Gotha, in Saxe-Gotha-Altenburg. While there, he also enjoyed social life among the local nobility, spending large amounts of money, which deeply concerned his frugal mother. He left the Gymnasium after writing a satirical poem about one of the schoolmasters. Although Arthur claimed that he left voluntarily, his mother's letter indicates that he may have been expelled. Arthur spent two years as a merchant in honor of his dead father. During this time, he had doubts about being able to start a new life as a scholar. Most of his prior education was as a practical merchant and he had trouble learning Latin; a prerequisite for an academic career. His mother moved away, with her daughter Adele, to Weimar—the then centre of German literature—to enjoy social life among writers and artists. Arthur and his mother did not part on good terms. In one letter, she wrote: "You are unbearable and burdensome, and very hard to live with; all your good qualities are overshadowed by your conceit, and made useless to the world simply because you cannot restrain your propensity to pick holes in other people." His mother, Johanna, was generally described as vivacious and sociable. After they split, they did not meet again. She died 24 years later. Some of Arthur's negative opinions about women may be rooted in his troubled relationship with his mother. Arthur moved to Hamburg to live with his friend Jean Anthime, who was also studying to become a merchant. Education He moved to Weimar but did not live with his mother, who even tried to discourage him from coming by explaining that they would not get along very well. Their relationship deteriorated even further due to their temperamental differences. He accused his mother of being financially irresponsible, flirtatious and seeking to remarry, which he considered an insult to his father's memory. His mother, while professing her love to him, criticized him sharply for being moody, tactless, and argumentative, and urged him to improve his behavior so that he would not alienate people. Arthur concentrated on his studies, which were now going very well, and he also enjoyed the usual social life such as balls, parties and theater. By that time Johanna's famous salon was well established among local intellectuals and dignitaries, the most celebrated of them being Goethe. Arthur attended her parties, usually when he knew that Goethe would be there—although the famous writer and statesman seemed not even to notice the young and unknown student. It is possible that Goethe kept a distance because Johanna warned him about her son's depressive and combative nature, or because Goethe was then on bad terms with Arthur's language instructor and roommate, Franz Passow. Schopenhauer was also captivated by the beautiful Karoline Jagemann, mistress of Karl August, Grand Duke of Saxe-Weimar-Eisenach, and he wrote to her his only known love poem. Despite his later celebration of asceticism and negative views of sexuality, Schopenhauer occasionally had sexual affairs—usually with women of lower social status, such as servants, actresses, and sometimes even paid prostitutes. In a letter to his friend Anthime he claims that such affairs continued even in his mature age and admits that he had two out-of-wedlock daughters (born in 1819 and 1836), both of whom died in infancy. In their youthful correspondence Arthur and Anthime were somewhat boastful and competitive about their sexual exploits—but Schopenhauer seemed aware that women usually did not find him very charming or physically attractive, and his desires often remained unfulfilled. He left Weimar to become a student at the University of Göttingen in 1809. There are no written reasons about why Schopenhauer chose that university instead of the then more famous University of Jena, but Göttingen was known as more modern and scientifically oriented, with less attention given to theology. Law or medicine were usual choices for young men of Schopenhauer's status who also needed career and income; he chose medicine due to his scientific interests. Among his notable professors were Bernhard Friedrich Thibaut, Arnold Hermann Ludwig Heeren, Johann Friedrich Blumenbach, Friedrich Stromeyer, Heinrich Adolf Schrader, Johann Tobias Mayer and Konrad Johann Martin Langenbeck. He studied metaphysics, psychology and logic under Gottlob Ernst Schulze, the author of Aenesidemus, who made a strong impression and advised him to concentrate on Plato and Immanuel Kant. He decided to switch from medicine to philosophy around 1810–11 and he left Göttingen, which did not have a strong philosophy program: besides Schulze, the only other philosophy professor was Friedrich Bouterwek, whom Schopenhauer disliked. He did not regret his medicinal and scientific studies; he claimed that they were necessary for a philosopher, and even in Berlin he attended more lectures in sciences than in philosophy. During his days at Göttingen, he spent considerable time studying, but also continued his flute playing and social life. His friends included Friedrich Gotthilf Osann, Karl Witte, Christian Charles Josias von Bunsen, and William Backhouse Astor Sr. He arrived at the newly founded University of Berlin for the winter semester of 1811–12. At the same time, his mother had just begun her literary career; she published her first book in 1810, a biography of her friend Karl Ludwig Fernow, which was a critical success. Arthur attended lectures by the prominent post-Kantian philosopher Johann Gottlieb Fichte, but quickly found many points of disagreement with his ; he also found Fichte's lectures tedious and hard to understand. He later mentioned Fichte only in critical, negative terms—seeing his philosophy as a lower-quality version of Kant's and considering it useful only because Fichte's poor arguments unintentionally highlighted some failings of Kantianism. He also attended the lectures of the famous Protestant theologian Friedrich Schleiermacher, whom he also quickly came to dislike. His notes and comments on Schleiermacher's lectures show that Schopenhauer was becoming very critical of religion and moving towards atheism. He learned by self-directed reading; besides Plato, Kant and Fichte he also read the works of Schelling, Fries, Jacobi, Bacon, Locke, and much current scientific literature. He attended philological courses by August Böckh and Friedrich August Wolf and continued his naturalistic interests with courses by Martin Heinrich Klaproth, Paul Erman, Johann Elert Bode, Ernst Gottfried Fischer, Johann Horkel, Friedrich Christian Rosenthal and Hinrich Lichtenstein (Lichtenstein was also a friend whom he met at one of his mother's parties in Weimar). Early work Schopenhauer left Berlin in a rush in 1813, fearing that the city could be attacked and that he could be pressed into military service as Prussia had just joined the war against France. He returned to Weimar but left after less than a month, disgusted by the fact that his mother was now living with her supposed lover, Georg Friedrich Konrad Ludwig Müller von Gerstenbergk (1778–1838), a civil servant twelve years younger than her; he considered the relationship an act of infidelity to his father's memory. He settled for a while in Rudolstadt, hoping that no army would pass through the small town. He spent his time in solitude, hiking in the mountains and the Thuringian forest and writing his dissertation, On the Fourfold Root of the Principle of Sufficient Reason. He completed his dissertation at about the same time as the French army was defeated at the Battle of Leipzig. He became irritated by the arrival of soldiers in the town and accepted his mother's invitation to visit her in Weimar. She tried to convince him that her relationship with Gerstenbergk was platonic and that she had no intention of remarrying. But Schopenhauer remained suspicious and often came in conflict with Gerstenbergk because he considered him untalented, pretentious, and nationalistic. His mother had just published her second book, Reminiscences of a Journey in the Years 1803, 1804, and 1805, a description of their family tour of Europe, which quickly became a hit. She found his dissertation incomprehensible and said it was unlikely that anyone would ever buy a copy. In a fit of temper Arthur told her that people would read his work long after the "rubbish" she wrote was totally forgotten. In fact, although they considered her novels of dubious quality, the Brockhaus publishing firm held her in high esteem because they consistently sold well. Hans Brockhaus (1888–1965) later claimed that his predecessors "saw nothing in this manuscript, but wanted to please one of our best-selling authors by publishing her son's work. We published more and more of her son Arthur's work and today nobody remembers Johanna, but her son's works are in steady demand and contribute to Brockhaus'[s] reputation." He kept large portraits of the pair in his office in Leipzig for the edification of his new editors. Also contrary to his mother's prediction, Schopenhauer's dissertation made an impression on Goethe, to whom he sent it as a gift. Although it is doubtful that Goethe agreed with Schopenhauer's philosophical positions, he was impressed by his intellect and extensive scientific education. Their subsequent meetings and correspondence were a great honor to a young philosopher, who was finally acknowledged by his intellectual hero. They mostly discussed Goethe's newly published (and somewhat lukewarmly received) work on color theory. Schopenhauer soon started writing his own treatise on the subject, On Vision and Colors, which in many points differed from his teacher's. Although they remained polite towards each other, their growing theoretical disagreements—and especially Schopenhauer's extreme self-confidence and tactless criticisms—soon made Goethe become distant again and after 1816 their correspondence became less frequent. Schopenhauer later admitted that he was greatly hurt by this rejection, but he continued to praise Goethe, and considered his color theory a great introduction to his own. Another important experience during his stay in Weimar was his acquaintance with Friedrich Majer—a historian of religion, orientalist and disciple of Herder—who introduced him to Eastern philosophy (see also Indology). Schopenhauer was immediately impressed by the Upanishads (he called them "the production of the highest human wisdom", and believed that they contained superhuman concepts) and the Buddha, and put them on a par with Plato and Kant. He continued his studies by reading the Bhagavad Gita, an amateurish German journal Asiatisches Magazin and Asiatick Researches by the Asiatic Society. Schopenhauer held a profound respect for Indian philosophy; although he loved Hindu texts, he was more interested in Buddhism, which he came to regard as the best religion. His studies on Hindu and Buddhist texts were constrained by the lack of adequate literature, and the latter were mostly restricted to Early Buddhism. He also claimed that he formulated most of his ideas independently, and only later realized the similarities with Buddhism. Schopenhauer read the Latin translation and praised the Upanishads in his main work, The World as Will and Representation (1819), as well as in his Parerga and Paralipomena (1851), and commented,In the whole world there is no study so beneficial and so elevating as that of the Upanishads. It has been the solace of my life, it will be the solace of my death. As the relationship with his mother fell to a new low, in May 1814 he left Weimar and moved to Dresden. He continued his philosophical studies, enjoyed the cultural life, socialized with intellectuals and engaged in sexual affairs. His friends in Dresden were Johann Gottlob von Quandt, Friedrich Laun, Karl Christian Friedrich Krause and Ludwig Sigismund Ruhl, a young painter who made a romanticized portrait of him in which he improved some of Schopenhauer's unattractive physical features. His criticisms of local artists occasionally caused public quarrels when he ran into them in public. Schopenhauer's main occupation during his stay in Dresden was his seminal philosophical work, The World as Will and Representation, which he started writing in 1814 and finished in 1818. He was recommended to the publisher Friedrich Arnold Brockhaus by Baron Ferdinand von Biedenfeld, an acquaintance of his mother. Although Brockhaus accepted his manuscript, Schopenhauer made a poor impression because of his quarrelsome and fussy attitude, as well as very poor sales of the book after it was published in December 1818. In September 1818, while waiting for his book to be published and conveniently escaping an affair with a maid that caused an unwanted pregnancy, Schopenhauer left Dresden for a year-long vacation in Italy. He visited Venice, Bologna, Florence, Naples and Milan, travelling alone or accompanied by mostly English tourists he met. He spent the winter months in Rome, where he accidentally met his acquaintance Karl Witte and engaged in numerous quarrels with German tourists in the Caffè Greco, among them Johann Friedrich Böhmer, who also mentioned his insulting remarks and unpleasant character. He enjoyed art, architecture, and ancient ruins, attended plays and operas, and continued his philosophical contemplation and love affairs. One of his affairs supposedly became serious, and for a while he contemplated marriage to a rich Italian noblewoman—but, despite his mentioning this several times, no details are known and it may have been Schopenhauer exaggerating. He corresponded regularly with his sister Adele and became close to her as her relationship with Johanna and Gerstenbergk also deteriorated. She informed him about their financial troubles as the banking house of A. L. Muhl in Danzig—in which her mother invested their whole savings and Arthur a third of his—was near bankruptcy. Arthur offered to share his assets, but his mother refused and became further enraged by his insulting comments. The women managed to receive only thirty percent of their savings while Arthur, using his business knowledge, took a suspicious and aggressive stance towards the banker and eventually received his part in full. The affair additionally worsened the relationships among all three members of the Schopenhauer family. He shortened his stay in Italy because of the trouble with Muhl and returned to Dresden. Disturbed by the financial risk and the lack of responses to his book he decided to take an academic position since it provided him with both income and an opportunity to promote his views. He contacted his friends at universities in Heidelberg, Göttingen and Berlin and found Berlin most attractive. He scheduled his lectures to coincide with those of the famous philosopher G. W. F. Hegel, whom Schopenhauer described as a "clumsy charlatan". He was especially appalled by Hegel's supposedly poor knowledge of natural sciences and tried to engage him in a quarrel about it already at his test lecture in March 1820. Hegel was also facing political suspicions at the time, when many progressive professors were fired, while Schopenhauer carefully mentioned in his application that he had no interest in politics. Despite their differences and the arrogant request to schedule lectures at the same time as his own, Hegel still voted to accept Schopenhauer to the university. Only five students turned up to Schopenhauer's lectures, and he dropped out of academia. A late essay, "On University Philosophy", expressed his resentment towards the work conducted in academies. Later life After his tenure in academia, he continued to travel extensively, visiting Leipzig, Nuremberg, Stuttgart, Schaffhausen, Vevey, Milan and spending eight months in Florence. Before he left for his three-year travel, Schopenhauer had an incident with his Berlin neighbor, 47-year-old seamstress Caroline Louise Marquet. The details of the August 1821 incident are unknown. He claimed that he had just pushed her from his entrance after she had rudely refused to leave, and that she had purposely fallen to the ground so that she could sue him. She claimed that he had attacked her so violently that she had become paralyzed on her right side and unable to work. She immediately sued him, and the process lasted until May 1827, when a court found Schopenhauer guilty and forced him to pay her an annual pension until her death in 1842. Schopenhauer enjoyed Italy, where he studied art and socialized with Italian and English nobles. It was his last visit to the country. He left for Munich and stayed there for a year, mostly recuperating from various health issues, some of them possibly caused by venereal diseases (the treatment his doctor used suggests syphilis). He contacted publishers, offering to translate Hume into German and Kant into English, but his proposals were declined. Returning to Berlin, he began to study Spanish so he could read some of his favorite authors in their original language. He liked Pedro Calderón de la Barca, Lope de Vega, Miguel de Cervantes, and especially Baltasar Gracián. He also made failed attempts to publish his translations of their works. Few attempts to revive his lectures—again scheduled at the same time as Hegel's—also failed, as did his inquiries about relocating to other universities. During his Berlin years, Schopenhauer occasionally mentioned his desire to marry and have a family. For a while he was unsuccessfully courting 17-year-old Flora Weiss, who was 22 years younger than himself. His unpublished writings from that time show that he was already very critical of monogamy but still not advocating polygyny—instead musing about a polyamorous relationship that he called "tetragamy". He had an on-and-off relationship with a young dancer, Caroline Richter (she also used the surname Medon after one of her ex-lovers). They met when he was 33 and she was 19 and working at the Berlin Opera. She had already had numerous lovers and a son out of wedlock, and later gave birth to another son, this time to an unnamed foreign diplomat (she soon had another pregnancy but the child was stillborn). As Schopenhauer was preparing to escape from Berlin in 1831, due to a cholera epidemic, he offered to take her with him on the condition that she left her young son behind. She refused and he went alone; in his will he left her a significant sum of money, but insisted that it should not be spent in any way on her second son. Schopenhauer claimed that, in his last year in Berlin, he had a prophetic dream that urged him to escape from the city. As he arrived in his new home in Frankfurt, he supposedly had another supernatural experience, an apparition of his dead father and his mother, who was still alive. This experience led him to spend some time investigating paranormal phenomena and magic. He was quite critical of the available studies and claimed that they were mostly ignorant or fraudulent, but he did believe that there are authentic cases of such phenomena and tried to explain them through his metaphysics as manifestations of the will. Upon his arrival in Frankfurt, he experienced a period of depression and declining health. He renewed his correspondence with his mother, and she seemed concerned that he might commit suicide like his father. By now Johanna and Adele were living very modestly. Johanna's writing did not bring her much income, and her popularity was waning. Their correspondence remained reserved, and Arthur seemed undisturbed by her death in 1838. His relationship with his sister grew closer and he corresponded with her until she died in 1849. In July 1832 Schopenhauer left Frankfurt for Mannheim but returned in July 1833 to remain there for the rest of his life, except for a few short journeys. He lived alone except for a succession of pet poodles named Atman and Butz. In 1836, he published On the Will in Nature. In 1836, he sent his essay "On the Freedom of the Will" to the contest of the Royal Norwegian Society of Sciences and won the prize for the following year. He sent another essay, "On the Basis of Morality", to the Royal Danish Society for Scientific Studies, but did not win the prize despite being the only contestant. The Society was appalled that several distinguished contemporary philosophers were mentioned in a very offensive manner, and claimed that the essay missed the point of the set topic and that the arguments were inadequate. Schopenhauer, who had been very confident that he would win, was enraged by this rejection. He published both essays as The Two Basic Problems of Ethics. The first edition, published in 1841, again failed to draw attention to his philosophy. In the preface to the second edition, in 1860, he was still pouring insults on the Royal Danish Society. Two years later, after some negotiations, he managed to convince his publisher, Brockhaus, to print the second, updated edition of The World as Will and Representation. That book was again mostly ignored and the few reviews were mixed or negative. Schopenhauer began to attract some followers, mostly outside academia, among practical professionals (several of them were lawyers) who pursued private philosophical studies. He jokingly referred to them as "evangelists" and "apostles". One of the most active early followers was Julius Frauenstädt, who wrote numerous articles promoting Schopenhauer's philosophy. He was also instrumental in finding another publisher after Brockhaus declined to publish Parerga and Paralipomena, believing that it would be another failure. Though Schopenhauer later stopped corresponding with him, claiming that he did not adhere closely enough to his ideas, Frauenstädt continued to promote Schopenhauer's work. They renewed their communication in 1859 and Schopenhauer named him heir for his literary estate. Frauenstädt also became the editor of the first collected works of Schopenhauer. In 1848, Schopenhauer witnessed violent upheaval in Frankfurt after General Hans Adolf Erdmann von Auerswald and Prince Felix Lichnowsky were murdered. He became worried for his own safety and property. Even earlier in life he had had such worries and kept a sword and loaded pistols near his bed to defend himself from thieves. He gave a friendly welcome to Austrian soldiers who wanted to shoot revolutionaries from his window and as they were leaving he gave one of the officers his opera glasses to help him monitor rebels. The rebellion passed without any loss to Schopenhauer and he later praised Alfred I, Prince of Windisch-Grätz for restoring order. He even modified his will, leaving a large part of his property to a Prussian fund that helped soldiers who became invalids while fighting rebellion in 1848 or the families of soldiers who died in battle. As Young Hegelians were advocating change and progress, Schopenhauer claimed that misery is natural for humans and that, even if some utopian society were established, people would still fight each other out of boredom, or would starve due to overpopulation. In 1851, Schopenhauer published Parerga and Paralipomena, which, as the title says, contains essays that are supplementary to his main work. It was his first successful, widely read book, partly due to the work of his disciples who wrote praising reviews. The essays that proved most popular were the ones that actually did not contain the basic philosophical ideas of his system. Many academic philosophers considered him a great stylist and cultural critic but did not take his philosophy seriously. His early critics liked to point out similarities of his ideas to those Fichte and Schelling, or to claim that there were numerous contradictions in his philosophy. Both criticisms enraged Schopenhauer. He was becoming less interested in intellectual fights, but encouraged his disciples to do so. His private notes and correspondence show that he acknowledged some of the criticisms regarding contradictions, inconsistencies, and vagueness in his philosophy, but claimed that he was not concerned about harmony and agreement in his propositions and that some of his ideas should not be taken literally but instead as metaphors. Academic philosophers were also starting to notice his work. In 1856, the University of Leipzig sponsored an essay contest about Schopenhauer's philosophy, which was won by Rudolf Seydel's very critical essay. Schopenhauer's friend Jules Lunteschütz made the first of his four portraits of him—which Schopenhauer did not particularly like—which was soon sold to a wealthy landowner, Carl Ferdinand Wiesike, who built a house to display it. Schopenhauer seemed flattered and amused by this, and would claim that it was his first chapel. As his fame increased, copies of paintings and photographs of him were being sold and admirers were visiting the places where he had lived and written his works. People visited Frankfurt's Englischer Hof to observe him dining. Admirers gave him gifts and asked for autographs. He complained that he still felt isolated due to his not very social nature and the fact that many of his good friends had already died from old age. He remained healthy in his own old age, which he attributed to regular walks no matter the weather and always getting enough sleep. He had a great appetite and could read without glasses, but his hearing had been declining since his youth and he developed problems with rheumatism. He remained active and lucid, continued his reading, writing and correspondence until his death. The numerous notes that he made during these years, amongst others on aging, were published posthumously under the title Senilia. In the spring of 1860 his health began to decline, and he experienced shortness of breath and heart palpitations; in September he suffered inflammation of the lungs and, although he was starting to recover, he remained very weak. The last friend to visit him was Wilhelm Gwinner; according to him, Schopenhauer was concerned that he would not be able to finish his planned additions to Parerga and Paralipomena but was at peace with dying. He died of pulmonary-respiratory failure on 21 September 1860 while sitting at home on his couch. He died at the age of 72 and had a funeral conducted by a Lutheran minister. Philosophy The world as representation Schopenhauer saw his philosophy as an extension of Kant's, and used the results of Kantian epistemological investigation (transcendental idealism) as starting point for his own. Kant had argued that the empirical world is merely a complex of appearances whose existence and connection occur only in our mental representations. Schopenhauer did not deny that the external world existed empirically but followed Kant in claiming that our knowledge and experience of the world is always indirect. Schopenhauer reiterates this in the first sentence of his main work: "The world is my representation (Die Welt ist meine Vorstellung)". Everything that there is for cognition (the entire world) exists simply as an object in relation to a subject—a 'representation' to a subject. Everything that belongs to the world is, therefore, 'subject-dependent'. In Book One of The World as Will and Representation, Schopenhauer considers the world from this angle—that is, insofar as it is representation. Theory of perception In November 1813 Goethe invited Schopenhauer to help him on his Theory of Colours. Although Schopenhauer considered colour theory a minor matter, he accepted the invitation out of admiration for Goethe. Nevertheless, these investigations led him to his most important discovery in epistemology: finding a demonstration for the a priori nature of causality. Kant openly admitted that it was Hume's skeptical assault on causality that motivated the critical investigations in his Critique of Pure Reason and gave an elaborate proof to show that causality is a priori. After G. E. Schulze had made it plausible that Kant had not disproven Hume's skepticism, it was up to those loyal to Kant's project to prove this important matter. The difference between the approaches of Kant and Schopenhauer was this: Kant simply declared that the empirical content of perception is "given" to us from outside, an expression with which Schopenhauer often expressed his dissatisfaction. He, on the other hand, was occupied with the questions: how do we get this empirical content of perception; how is it possible to comprehend subjective sensations "limited to my skin" as the objective perception of things that lie "outside" of me? Causality is therefore not an empirical concept drawn from objective perceptions, as Hume had maintained; instead, as Kant had said, objective perception presupposes knowledge of causality. By this intellectual operation, comprehending every effect in our sensory organs as having an external cause, the external world arises. With vision, finding the cause is essentially simplified due to light acting in straight lines. We are seldom conscious of the process that interprets the double sensation in both eyes as coming from one object, that inverts the impressions on the retinas, and that uses the change in the apparent position of an object relative to more distant objects provided by binocular vision to perceive depth and distance. Schopenhauer stresses the importance of the intellectual nature of perception; the senses furnish the raw material by which the intellect produces the world as representation. He set out his theory of perception for the first time in On Vision and Colors, and, in the subsequent editions of Fourfold Root, an extensive exposition is given in § 21. The world as will In Book Two of The World as Will and Representation, Schopenhauer considers what the world is beyond the aspect of it that appears to us—that is, the aspect of the world beyond representation, the world considered "in-itself" or "noumena", its inner essence. The very being in-itself of all things, Schopenhauer argues, is will (Wille). The empirical world that appears to us as representation has plurality and is ordered in a spatio-temporal framework. The world as thing in-itself must exist outside the subjective forms of space and time. Although the world manifests itself to our experience as a multiplicity of objects (the "objectivation" of the will), each element of this multiplicity has the same blind essence striving towards existence and life. Human rationality is merely a secondary phenomenon that does not distinguish humanity from the rest of nature at the fundamental, essential level. The advanced cognitive abilities of human beings, Schopenhauer argues, serve the ends of willing—an illogical, directionless, ceaseless striving that condemns the human individual to a life of suffering unredeemed by any final purpose. Schopenhauer's philosophy of the will as the essential reality behind the world as representation is often called metaphysical voluntarism. For Schopenhauer, understanding the world as will leads to ethical concerns (see the ethics section below for further detail), which he explores in the Fourth Book of The World as Will and Representation and again in his two prize essays on ethics, On the Freedom of the Will and On the Basis of Morality. No individual human actions are free, Schopenhauer argues, because they are events in the world of appearance and thus are subject to the principle of sufficient reason: a person's actions are a necessary consequence of motives and the given character of the individual human. Necessity extends to the actions of human beings just as it does to every other appearance, and thus we cannot speak of freedom of individual willing. Albert Einstein quoted the Schopenhauerian idea that "a man can do as he will, but not will as he will." Yet the will as thing in-itself is free, as it exists beyond the realm of representation and thus is not constrained by any of the forms of necessity that are part of the principle of sufficient reason. According to Schopenhauer, salvation from our miserable existence can come through the will's being "tranquillized" by the metaphysical insight that reveals individuality to be merely an illusion. The saint or 'great soul' intuitively "recognizes the whole, comprehends its essence, and finds that it is constantly passing away, caught up in vain strivings, inner conflict, and perpetual suffering". The negation of the will, in other words, stems from the insight that the world in-itself (free from the forms of space and time) is one. Ascetic practices, Schopenhauer remarks, are used to aid the will's "self-abolition", which brings about a blissful, redemptive "will-less" state of emptiness that is free from striving or suffering. Art and aesthetics For Schopenhauer, human "willing"—desiring, craving, etc.—is at the root of suffering. A temporary way to escape this pain is through aesthetic contemplation. Here one moves away from ordinary cognizance of individual things to cognizance of eternal Platonic Ideas—in other words, cognizance that is free from the service of will. In aesthetic contemplation, one no longer perceives an object of perception as something from which one is separated; rather "it is as if the object alone existed without anyone perceiving it, and one can thus no longer separate the perceiver from the perception, but the two have become one, the entirety of consciousness entirely filled and occupied by a single perceptual image". Subject and object are no longer distinguishable, and the Idea comes to the fore. From this aesthetic immersion, one is no longer an individual who suffers as a result of servitude to one's individual will but, rather, becomes a "pure, will-less, painless, timeless, subject of cognition". The pure, will-less subject of cognition is cognizant only of Ideas, not individual things: this is a kind of cognition that is unconcerned with relations between objects according to the Principle of Sufficient Reason (time, space, cause and effect) and instead involves complete absorption in the object. Art is the practical consequence of this brief aesthetic contemplation, since it attempts to depict the essence/pure Ideas of the world. Music, for Schopenhauer, is the purest form of art because it is the one that depicts the will itself without it appearing as subject to the Principle of Sufficient Reason, therefore as an individual object. According to Daniel Albright, "Schopenhauer thought that music was the only art that did not merely copy ideas, but actually embodied the will itself". He deemed music a timeless, universal language comprehended everywhere, that can imbue global enthusiasm, if in possession of a significant melody. Mathematics Schopenhauer's realist views on mathematics are evident in his criticism of contemporaneous attempts to prove the parallel postulate in Euclidean geometry. Writing shortly before the discovery of hyperbolic geometry demonstrated the logical independence of the axiom—and long before the general theory of relativity revealed that it does not necessarily express a property of physical space—Schopenhauer criticized mathematicians for trying to use indirect concepts to prove what he held was directly evident from intuitive perception. Throughout his writings, Schopenhauer criticized the logical derivation of philosophies and mathematics from mere concepts, instead of from intuitive perceptions. Although Schopenhauer could see no justification for trying to prove Euclid's parallel postulate, he did see a reason for examining another of Euclid's axioms. This follows Kant's reasoning. Ethics Schopenhauer asserts that the task of ethics is not to prescribe moral actions that ought to be done, but to investigate moral actions. As such, he states that philosophy is always theoretical: its task to explain what is given. According to Kant's transcendental idealism, space and time are forms of our sensibility in which phenomena appear in multiplicity. Reality in itself is free from multiplicity, not in the sense that an object is one, but that it is outside the possibility of multiplicity. Two individuals, though they appear distinct, are in-themselves not distinct. Appearances are entirely subordinated to the principle of sufficient reason. The egoistic individual who focuses his aims on his own interests has to deal with empirical laws as well as he can. What is relevant for ethics are individuals who can act against their own self-interest. If we take a man who suffers when he sees his fellow men living in poverty and consequently uses a significant part of his income to support their needs instead of his own pleasures, then the simplest way to describe this is that he makes less distinction between himself and others than is usually made. Regarding how things appear to us, the egoist asserts a gap between two individuals, but the altruist experiences the sufferings of others as his own. In the same way a compassionate man cannot hurt animals, though they appear as distinct from himself. What motivates the altruist is compassion. The suffering of others is for him not a cold matter to which he is indifferent, but he feels connectiveness to all beings. Compassion is thus the basis of morality. Eternal justice Schopenhauer calls the principle through which multiplicity appears the principium individuationis. When we behold nature we see that it is a cruel battle for existence. Individual manifestations of the will can maintain themselves only at the expense of others—the will, as the only thing that exists, has no other option but to devour itself to experience pleasure. This is a fundamental characteristic of the will, and cannot be circumvented. Unlike temporal or human justice, which requires time to repay an evil deed and "has its seat in the state, as requiting and punishing", eternal justice "rules not the state but the world, is not dependent upon human institutions, is not subject to chance and deception, is not uncertain, wavering, and erring, but infallible, fixed, and sure". Eternal justice is not retributive, because retribution requires time. There are no delays or reprieves. Instead, punishment is tied to the offence, "to the point where the two become one. ... Tormenter and tormented are one. The [Tormenter] errs in that he believes he is not a partaker in the suffering; the [tormented], in that he believes he is not a partaker in the guilt." Suffering is the moral outcome of our attachment to pleasure. Schopenhauer deemed that this truth was expressed by the Christian dogma of original sin and, in Eastern religions, by the dogma of rebirth. Quietism He who sees through the principium individuationis and comprehends suffering in general as his own will see suffering everywhere and, instead of fighting for the happiness of his individual manifestation, will abhor life itself since he knows that it is inseparably connected with suffering. For him, a happy individual life in a world of suffering is like a beggar who dreams one night that he is a king. Those who have experienced this intuitive knowledge cannot affirm life, but exhibit asceticism and quietism, meaning that they are no longer sensitive to motives, are not concerned about their individual welfare, and accept without resistance the evil that others inflict on them. They welcome poverty and neither seek nor flee death. Schopenhauer referred to asceticism as the denial of the will to live. Human life is a ceaseless struggle for satisfaction and, instead of continuing their struggle, ascetics break it. It does not matter if these ascetics adhere to the dogmata of Christianity or to Dharmic religions, since their way of living is the result of intuitive knowledge. Psychology Philosophers have not traditionally been impressed by the necessity of sex, but Schopenhauer addressed sex and related concepts forthrightly: He named a force within man that he felt took invariable precedence over reason: the Will to Live or Will to Life (Wille zum Leben), defined as an inherent drive within human beings, and all creatures, to stay alive; a force that inveigles us into reproducing. Schopenhauer refused to conceive of love as either trifling or accidental, but rather understood it as an immensely powerful force that lay unseen within man's psyche, guaranteeing the quality of the human race: It has often been argued that Schopenhauer's thoughts on sexuality foreshadowed the theory of evolution, a claim met with satisfaction by Darwin as he included a quotation from Schopenhauer in his Descent of Man. This has also been noted about Freud's concepts of the libido and the unconscious mind, and evolutionary psychology in general. Political and social thought Politics Schopenhauer's politics were an echo of his system of ethics, which he elucidated in detail in his Die beiden Grundprobleme der Ethik (the two essays On the Freedom of the Will and On the Basis of Morality). In occasional political comments in his Parerga and Paralipomena and Manuscript Remains, Schopenhauer described himself as a proponent of limited government. Schopenhauer shared the view of Thomas Hobbes on the necessity of the state and state action to check the innate destructive tendencies of our species. He also defended the independence of the legislative, judicial and executive branches of power, and a monarch as an impartial element able to practise justice (in a practical and everyday sense, not a cosmological one). He declared that monarchy is "natural to man in almost the same way as it is to bees and ants, to cranes in flight, to wandering elephants, to wolves in a pack in search of prey, and to other animals". Intellect in monarchies, he writes, always has "much better chances against stupidity, its implacable and ever-present foe, than it has in republics; but this is a great advantage." On the other hand, Schopenhauer disparaged republicanism as being "as unnatural to man as it is unfavorable to higher intellectual life and thus to the arts and sciences". By his own admission, Schopenhauer did not give much thought to politics, and several times he wrote proudly of how little attention he paid "to political affairs of [his] day". In a life that spanned several revolutions in French and German government, and a few continent-shaking wars, he maintained his position of "minding not the times but the eternities". He wrote many disparaging remarks about Germany and the Germans. A typical example is: "For a German it is even good to have somewhat lengthy words in his mouth, for he thinks slowly, and they give him time to reflect." Punishment The State, Schopenhauer claimed, punishes criminals to prevent future crimes. It places "beside every possible motive for committing a wrong a more powerful motive for leaving it undone, in the inescapable punishment. Accordingly, the criminal code is as complete a register as possible of counter-motives to all criminal actions that can possibly be imagined ..." He claimed that this doctrine was not original to him but had appeared in the writings of Plato, Seneca, Hobbes, Pufendorf, and Anselm Feuerbach. Races and religions Schopenhauer attributed civilizational primacy to the northern "white races" due to their sensitivity and creativity (except for the ancient Egyptians and Hindus, whom he saw as equal): The highest civilization and culture, apart from the ancient Hindus and Egyptians, are found exclusively among the white races; and even with many dark peoples, the ruling caste or race is fairer in colour than the rest and has, therefore, evidently immigrated, for example, the Brahmans, the Incas, and the rulers of the South Sea Islands. All this is due to the fact that necessity is the mother of invention because those tribes that emigrated early to the north, and there gradually became white, had to develop all their intellectual powers and invent and perfect all the arts in their struggle with need, want and misery, which in their many forms were brought about by the climate. This they had to do in order to make up for the parsimony of nature and out of it all came their high civilization. Schopenhauer was fervently opposed to slavery. Speaking of the treatment of slaves in the slave-holding states of the United States, he condemned "those devils in human form, those bigoted, church-going, strict sabbath-observing scoundrels, especially the Anglican parsons among them" for how they "treat their innocent black brothers who through violence and injustice have fallen into their devil's claws". The slave-holding states of North America, Schopenhauer writes, are a "disgrace to the whole of humanity". In his Metaphysics of Sexual Love, Schopenhauer wrote: Further, the consideration as to the complexion is very decided. Blondes prefer dark persons, or brunettes; but the latter seldom prefer the former. The reason is, that fair hair and blue eyes are in themselves a variation from the type, almost an abnormity, analogous to white mice, or at least to grey horses. In no part of the world, not even in the vicinity of the pole, are they indigenous, except in Europe, and are clearly of Scandinavian origin. I may here express my opinion in passing that the white colour of the skin is not natural to man, but that by nature he has a black or brown skin, like our forefathers the Hindus; that consequently a white man has never originally sprung from the womb of nature, and that thus there is no such thing as a white race, much as this is talked of, but every white man is a faded or bleached one. Forced into the strange world, where he only exists like an exotic plant, and like this requires in winter the hothouse, in the course of thousands of years man became white. The gipsies, an Indian race which immigrated only about four centuries ago, show the transition from the complexion of the Hindu to our own. Therefore in sexual love nature strives to return to dark hair and brown eyes as the primitive type; but the white colour of the skin has become a second nature, though not so that the brown of the Hindu repels us. Finally, each one also seeks in the particular parts of the body the corrective of his own defects and aberrations, and does so the more decidedly the more important the part is. Schopenhauer also maintained a marked metaphysical and political anti-Judaism. He argued that Christianity constituted a revolt against what he styled the materialistic basis of Judaism, exhibiting an Indian-influenced ethics reflecting the Aryan-Vedic theme of spiritual self-conquest. He saw this as opposed to the ignorant drive toward earthly utopianism and superficiality of a worldly "Jewish" spirit: [Judaism] is, therefore, the crudest and poorest of all religions and consists merely in an absurd and revolting theism. It amounts to this that the κύριος ['Lord'], who has created the world, desires to be worshipped and adored; and so above all he is jealous, is envious of his colleagues, of all the other gods; if sacrifices are made to them he is furious and his Jews have a bad time ... It is most deplorable that this religion has become the basis of the prevailing religion of Europe; for it is a religion without any metaphysical tendency. While all other religions endeavor to explain to the people by symbols the metaphysical significance of life, the religion of the Jews is entirely immanent and furnishes nothing but a mere war-cry in the struggle with other nations. Women In his 1851 essay "On Women", Schopenhauer expressed opposition to what he called "Teutonico-Christian stupidity" of "reflexive, unexamined reverence for the female (abgeschmackten Weiberveneration)". He wrote: "Women are directly fitted for acting as the nurses and teachers of our early childhood by the fact that they are themselves childish, frivolous and short-sighted." He opined that women are deficient in artistic faculties and sense of justice, and expressed his opposition to monogamy. He claimed that "woman is by nature meant to obey". The essay does give some compliments: "women are decidedly more sober in their judgment than [men] are", and are more sympathetic to the suffering of others. Schopenhauer's writings influenced many, from Friedrich Nietzsche to nineteenth-century feminists. His biological analysis of the difference between the sexes, and their separate roles in the struggle for survival and reproduction, anticipates some of the claims that were later ventured by sociobiologists and evolutionary psychologists. When the elderly Schopenhauer sat for a sculpture portrait by the Prussian sculptor Elisabet Ney in 1859, he was much impressed by the young woman's wit and independence, as well as by her skill as a visual artist. After his time with Ney, he told Richard Wagner's friend Malwida von Meysenbug: "I have not yet spoken my last word about women. I believe that if a woman succeeds in withdrawing from the mass, or rather raising herself above the mass, she grows ceaselessly and more than a man." Pederasty In the third, expanded edition of The World as Will and Representation (1859), Schopenhauer added an appendix to his chapter on the Metaphysics of Sexual Love. He wrote that pederasty has the benefit of preventing ill-begotten children. Concerning this, he stated that "the vice we are considering appears to work directly against the aims and ends of nature, and that in a matter that is all important and of the greatest concern to her it must in fact serve these very aims, although only indirectly, as a means for preventing greater evils". Schopenhauer ends the appendix with the statement that "by expounding these paradoxical ideas, I wanted to grant to the professors of philosophy a small favour. I have done so by giving them the opportunity of slandering me by saying that I defend and commend pederasty." Heredity and eugenics Schopenhauer viewed personality and intellect as inherited. He quotes Horace's saying, "From the brave and good are the brave descended" (Odes, iv, 4, 29) and Shakespeare's line from Cymbeline, "Cowards father cowards, and base things sire base" (IV, 2) to reinforce his hereditarian argument. Mechanistically, Schopenhauer believed that a person inherits his intellect through his mother, and personal character through the father. This belief in heritability of traits informed Schopenhauer's view of love—placing it at the highest level of importance. For Schopenhauer the "final aim of all love intrigues, be they comic or tragic, is really of more importance than all other ends in human life. What it all turns upon is nothing less than the composition of the next generation. ... It is not the weal or woe of any one individual, but that of the human race to come, which is here at stake." This view of the importance for the species of whom we choose to love was reflected in his views on eugenics or good breeding. Here Schopenhauer wrote: With our knowledge of the complete unalterability both of character and of mental faculties, we are led to the view that a real and thorough improvement of the human race might be reached not so much from outside as from within, not so much by theory and instruction as rather by the path of generation. Plato had something of the kind in mind when, in the fifth book of his Republic, he explained his plan for increasing and improving his warrior caste. If we could castrate all scoundrels and stick all stupid geese in a convent, and give men of noble character a whole harem, and procure men, and indeed thorough men, for all girls of intellect and understanding, then a generation would soon arise which would produce a better age than that of Pericles. In another context, Schopenhauer reiterated his eugenic thesis: "If you want Utopian plans, I would say: the only solution to the problem is the despotism of the wise and noble members of a genuine aristocracy, a genuine nobility, achieved by mating the most magnanimous men with the cleverest and most gifted women. This proposal constitutes my Utopia and my Platonic Republic." Analysts (e.g., Keith Ansell-Pearson) have suggested that Schopenhauer's anti-egalitarianist sentiment and his support for eugenics influenced the neo-aristocratic philosophy of Friedrich Nietzsche, who initially considered Schopenhauer his mentor. Animal welfare As a consequence of his monistic philosophy, Schopenhauer was very concerned about animal welfare. For him, all individual animals, including humans, are essentially phenomenal manifestations of the one underlying Will. For him the word "will" designates force, power, impulse, energy, and desire; it is the closest word we have that can signify both the essence of all external things and our own direct, inner experience. Since every living thing possesses will, humans and animals are fundamentally the same and can recognize themselves in each other. For this reason, he claimed that a good person would have sympathy for animals, who are our fellow sufferers. In 1841, he praised the establishment in London of the Society for the Prevention of Cruelty to Animals, and in Philadelphia of the Animals' Friends Society. Schopenhauer went so far as to protest using the pronoun "it" in reference to animals because that led to treatment of them as though they were inanimate things. To reinforce his points, Schopenhauer referred to anecdotal reports of the look in the eyes of a monkey who had been shot and also the grief of a baby elephant whose mother had been killed by a hunter. Schopenhauer was very attached to his succession of pet poodles. He criticized Spinoza's belief that animals are a mere means for the satisfaction of humans. Intellectual interests and affinities Indology Schopenhauer read the Latin translation of the ancient Hindu texts, the Upanishads, translated by French writer Anquetil du Perron from the Persian translation of Prince Dara Shukoh entitled Sirre-Akbar ("The Great Secret"). He was so impressed by its philosophy that he called it "the production of the highest human wisdom", and believed it contained superhuman concepts. Schopenhauer considered India as "the land of the most ancient and most pristine wisdom, the place from which Europeans could trace their descent and the tradition by which they had been influenced in so many decisive ways", and regarded the Upanishads as "the most profitable and elevating reading which [...] is possible in the world. It has been the solace of my life, and will be the solace of my death." Schopenhauer was first introduced to Anquetil du Perron's translation by Friedrich Majer in 1814. They met during the winter of 1813–1814 in Weimar at the home of Schopenhauer's mother, according to the biographer Safranski. Majer was a follower of Herder, and an early Indologist. Schopenhauer did not begin serious study of the Indic texts until the summer of 1814. Safranski maintains that, between 1815 and 1817, Schopenhauer had another important cross-pollination with Indian thought in Dresden. This was through his neighbor of two years, Karl Christian Friedrich Krause. Krause was then a minor and rather unorthodox philosopher who attempted to mix his own ideas with ancient Indian wisdom. Krause had also mastered Sanskrit, unlike Schopenhauer, and they developed a professional relationship. It was from Krause that Schopenhauer learned meditation and received the closest thing to expert advice concerning Indian thought. The book Oupnekhat (Upanishad) always lay open on his table, and he invariably studied it before going to bed. He called the opening up of Sanskrit literature "the greatest gift of our century", and predicted that the philosophy and knowledge of the Upanishads would become the cherished faith of the West. Most noticeable, in the case of Schopenhauer's work, was the significance of the Chandogya Upanishad, whose Mahāvākya, Tat Tvam Asi, is mentioned throughout The World as Will and Representation. Buddhism Schopenhauer noted a correspondence between his doctrines and the Four Noble Truths of Buddhism. Similarities centered on the principles that life involves suffering, that suffering is caused by desire (taṇhā), and that the extinction of desire leads to liberation. Thus three of the four "truths of the Buddha" correspond to Schopenhauer's doctrine of the will. In Buddhism, while greed and lust are always unskillful, desire is ethically variable – it can be skillful, unskillful, or neutral. For Schopenhauer, will had ontological primacy over the intellect; desire is prior to thought. Schopenhauer felt this was similar to notions of puruṣārtha or goals of life in Vedānta Hinduism. In Schopenhauer's philosophy, denial of the will is attained by: personal experience of an extremely great suffering that leads to loss of the will to live; or knowledge of the essential nature of life in the world through observation of the suffering of other people. Buddhist nirvāṇa is not equivalent to the condition that Schopenhauer described as denial of the will. Nirvāṇa is not the extinguishing of the person as some Western scholars have thought, but only the "extinguishing" (the literal meaning of nirvana) of the flames of greed, hatred, and delusion that assail a person's character. Schopenhauer made the following statement in his discussion of religions: If I wished to take the results of my philosophy as the standard of truth, I should have to concede to Buddhism pre-eminence over the others. In any case, it must be a pleasure to me to see my doctrine in such close agreement with a religion that the majority of men on earth hold as their own, for this numbers far more followers than any other. And this agreement must be yet the more pleasing to me, inasmuch as in my philosophizing I have certainly not been under its influence [emphasis added]. For up till 1818, when my work appeared, there was to be found in Europe only a very few accounts of Buddhism. Buddhist philosopher Keiji Nishitani sought to distance Buddhism from Schopenhauer. While Schopenhauer's philosophy may sound rather mystical in such a summary, his methodology was resolutely empirical, rather than speculative or transcendental: Philosophy ... is a science, and as such has no articles of faith; accordingly, in it nothing can be assumed as existing except what is either positively given empirically, or demonstrated through indubitable conclusions. Also note: This actual world of what is knowable, in which we are and which is in us, remains both the material and the limit of our consideration. The argument that Buddhism affected Schopenhauer's philosophy more than any other Dharmic faith loses credence since he did not begin a serious study of Buddhism until after the publication of The World as Will and Representation in 1818. Scholars have started to revise earlier views about Schopenhauer's discovery of Buddhism. Proof of early interest and influence appears in Schopenhauer's 1815–16 notes (transcribed and translated by Urs App) about Buddhism. They are included in a recent case study that traces Schopenhauer's interest in Buddhism and documents its influence. Other scholarly work questions how similar Schopenhauer's philosophy actually is to Buddhism. Magic and occultism Some traditions in Western esotericism and parapsychology interested Schopenhauer and influenced his philosophical theories. He praised animal magnetism as evidence for the reality of magic in his On the Will in Nature, and went so far as to accept the division of magic into left-hand and right-hand magic, although he doubted the existence of demons. Schopenhauer grounded magic in the Will and claimed all forms of magical transformation depended on the human Will, not on ritual. This theory notably parallels Aleister Crowley's system of magick and its emphasis on human will. Given the importance of the Will to Schopenhauer's overarching system, this amounts to "suggesting his whole philosophical system had magical powers." Schopenhauer rejected the theory of disenchantment and claimed philosophy should synthesize itself with magic, which he believed amount to "practical metaphysics." Neoplatonism, including the traditions of Plotinus and to a lesser extent Marsilio Ficino, has also been cited as an influence on Schopenhauer. Interests Schopenhauer had a wide range of interests, from science and opera to occultism and literature. In his student years, Schopenhauer went more often to lectures in the sciences than philosophy. He kept a strong interest as his personal library contained near to 200 books of scientific literature at his death, and his works refer to scientific titles not found in the library. Many evenings were spent in the theatre, opera and ballet; Schopenhauer especially liked the operas of Mozart, Rossini and Bellini. Schopenhauer considered music the highest art, and played the flute during his whole life. As a polyglot, he knew German, Italian, Spanish, French, English, Latin and ancient Greek, and was an avid reader of poetry and literature. He particularly revered Goethe, Petrarch, Calderón and Shakespeare. If Goethe had not been sent into the world simultaneously with Kant in order to counterbalance him, so to speak, in the spirit of the age, the latter would have been haunted like a nightmare many an aspiring mind and would have oppressed it with great affliction. But now the two have an infinitely wholesome effect from opposite directions and will probably raise the German spirit to a height surpassing even that of antiquity. In philosophy, his most important influences were, according to himself, Kant, Plato and the Upanishads. Concerning the Upanishads and Vedas, he writes in The World as Will and Representation: If the reader has also received the benefit of the Vedas, the access to which by means of the Upanishads is in my eyes the greatest privilege which this still young century (1818) may claim before all previous centuries, if then the reader, I say, has received his initiation in primeval Indian wisdom, and received it with an open heart, he will be prepared in the very best way for hearing what I have to tell him. It will not sound to him strange, as to many others, much less disagreeable; for I might, if it did not sound conceited, contend that every one of the detached statements which constitute the Upanishads, may be deduced as a necessary result from the fundamental thoughts which I have to enunciate, though those deductions themselves are by no means to be found there. Thoughts on other philosophers Giordano Bruno and Spinoza Schopenhauer saw Bruno and Spinoza as philosophers not bound to their age or nation. "Both were fulfilled by the thought, that as manifold the appearances of the world may be, it is still one being, that appears in all of them. ... Consequently, there is no place for God as creator of the world in their philosophy, but God is the world itself." Schopenhauer expressed regret that Spinoza stuck for the presentation of his philosophy with the concepts of scholasticism and Cartesian philosophy, and tried to use geometrical proofs that do not hold because of vague and overly broad definitions. Bruno on the other hand, who knew much about nature and ancient literature, presented his ideas with Italian vividness, and is amongst philosophers the only one who comes near Plato's poetic and dramatic power of exposition. Schopenhauer noted that their philosophies do not provide any ethics, and it is therefore very remarkable that Spinoza called his main work Ethics. In fact, it could be considered complete from the standpoint of life-affirmation, if one completely ignores morality and self-denial. It is yet even more remarkable that Schopenhauer mentions Spinoza as an example of the denial of the will, if one uses the French biography by Jean Maximilien Lucas as the key to Tractatus de Intellectus Emendatione. Immanuel Kant The importance of Kant for Schopenhauer, in philosophy as well as on a personal level, cannot be overstated. Kant's philosophy was the foundation of Schopenhauer's, and he had high praise for the Transcendental Aesthetic section of Kant's Critique of Pure Reason. Schopenhauer maintained that Kant stands in the same relation to philosophers such as Berkeley and Plato, as Copernicus to Hicetas, Philolaus, and Aristarchus: Kant succeeded in demonstrating what previous philosophers merely asserted. Schopenhauer writes about Kant's influence on his work in the preface to the second edition of The World as Will and Representation: In his study room, one bust was of Buddha, the other was of Kant. The bond which Schopenhauer felt with the philosopher of Königsberg is demonstrated in an unfinished poem he dedicated to Kant (included in volume 2 of the Parerga): Schopenhauer dedicated one fifth of his main work, The World as Will and Representation, to a detailed criticism of the Kantian philosophy. Schopenhauer praised Kant for his distinction between appearance and the thing-in-itself, whereas the general consensus in German idealism was that this was the weakest spot of Kant's theory, since, according to Kant, causality can find application on objects of experience only, and consequently, things-in-themselves cannot be the cause of appearances. The inadmissibility of this reasoning was also acknowledged by Schopenhauer. He insisted that this was a true conclusion, drawn from false premises. Post-Kantian school The leading figures of post-Kantian philosophy—Johann Gottlieb Fichte, F. W. J. Schelling and G. W. F. Hegel—were not respected by Schopenhauer. He argued that they were not philosophers at all, for they lacked "the first requirement of a philosopher, namely a seriousness and honesty of inquiry." Rather, they were merely sophists who, excelling in the art of beguiling the public, pursued their own selfish interests (such as professional advancement within the university system). Diatribes against the vacuity, dishonesty, pomposity, and self-interest of these contemporaries are to be found throughout Schopenhauer's published writings. The following passage is an example: Schopenhauer deemed Schelling the most talented of the three and wrote that he would recommend his "elucidatory paraphrase of the highly important doctrine of Kant" concerning the intelligible character, if he had been honest enough to admit he was parroting Kant, instead of hiding this relation in a cunning manner. Schopenhauer reserved his most unqualified damning condemnation for Hegel, whom he considered less worthy than Fichte or Schelling. Whereas Fichte was merely a windbag (Windbeutel), Hegel was a "commonplace, inane, loathsome, repulsive, and ignorant charlatan." The philosophers Karl Popper and Mario Bunge agreed with this distinction. Hegel, Schopenhauer wrote in the preface to his Two Fundamental Problems of Ethics, not only "performed no service to philosophy, but he has had a detrimental influence on philosophy, and thereby on German literature in general, really a downright stupefying, or we could even say a pestilential influence, which it is therefore the duty of everyone capable of thinking for himself and judging for himself to counteract in the most express terms at every opportunity." Influence and legacy Schopenhauer remained the most influential German philosopher until the First World War. His philosophy was a starting point for a new generation of philosophers including Julius Bahnsen, Paul Deussen, Lazar von Hellenbach, Karl Robert Eduard von Hartmann, Ernst Otto Lindner, Philipp Mainländer, Friedrich Nietzsche, Olga Plümacher and Agnes Taubert. His legacy shaped the intellectual debate, and forced movements that were utterly opposed to him, neo-Kantianism and positivism, to address issues they would otherwise have completely ignored, and in doing so he changed them markedly. The French writer Maupassant commented that "to-day even those who execrate him seem to carry in their own souls particles of his thought". Other philosophers of the 19th century who cited his influence include Hans Vaihinger, Volkelt, Solovyov and Weininger. Schopenhauer was well read by physicists, most notably Einstein, Schrödinger, Wolfgang Pauli, and Majorana. Einstein described Schopenhauer's thoughts as a "continual consolation" and called him a genius. In his Berlin study three figures hung on the wall: Faraday, Maxwell, Schopenhauer. Konrad Wachsmann recalled: "He often sat with one of the well-worn Schopenhauer volumes, and as he sat there, he seemed so pleased, as if he were engaged with a serene and cheerful work." When Erwin Schrödinger discovered Schopenhauer ("the greatest savant of the West") he considered switching his study of physics to philosophy. He maintained the idealistic views during the rest of his life. Wolfgang Pauli accepted the main tenet of Schopenhauer's metaphysics, that the thing-in-itself is will. But most of all Schopenhauer is famous for his influence on artists. Richard Wagner became one of the earliest and most famous adherents of the Schopenhauerian philosophy. The admiration was not mutual, and Schopenhauer proclaimed: "I remain faithful to Rossini and Mozart!" So he has been nicknamed "the artist's philosopher". See also Influence of Schopenhauer on Tristan und Isolde. Under the influence of Schopenhauer, Leo Tolstoy became convinced that the truth of all religions lies in self-renunciation. When he read Schopenhauer's philosophy, Tolstoy exclaimed "at present I am convinced that Schopenhauer is the greatest genius among men. ... It is the whole world in an incomparably beautiful and clear reflection." He said that what he has written in War and Peace is also said by Schopenhauer in The World as Will and Representation. Jorge Luis Borges remarked that the reason he had never attempted to write a systematic account of his world view, despite his penchant for philosophy and metaphysics in particular, was because Schopenhauer had already written it for him. Other figures in literature who were strongly influenced by Schopenhauer were Thomas Mann, Thomas Hardy, Afanasy Fet, J.-K. Huysmans and George Santayana. In Herman Melville's final years, while he wrote Billy Budd, he read Schopenhauer's essays and marked them heavily. Scholar Brian Yothers notes that Melville "marked numerous misanthropic and even suicidal remarks, suggesting an attraction to the most extreme sorts of solitude, but he also made note of Schopenhauer's reflection on the moral ambiguities of genius." Schopenhauer's attraction to and discussions of both Eastern and Western religions in conjunction with each other made an impression on Melville in his final years. Sergei Prokofiev, although initially reluctant to engage with works noted for their pessimism, became fascinated with Schopenhauer after reading Aphorisms on the Wisdom of Life in Parerga and Paralipomena. "With his truths Schopenhauer gave me a spiritual world and an awareness of happiness." Friedrich Nietzsche owed the awakening of his philosophical interest to reading The World as Will and Representation and admitted that he was one of the few philosophers that he respected, dedicating to him his essay "Schopenhauer als Erzieher" one of his Untimely Meditations. Early in his career, Ludwig Wittgenstein adopted Schopenhauer's epistemological idealism, and some traits of Schopenhauer's influence (particularly Schopenhauerian transcendentalism) can be observed in the Tractatus Logico-Philosophicus. Later on, Wittgenstein rejected epistemological transcendental idealism for Gottlob Frege's conceptual realism. In later years, Wittgenstein became highly dismissive of Schopenhauer, describing him as an ultimately shallow thinker. His friend Bertrand Russell had a low opinion on the philosopher, and even came to attack him in his History of Western Philosophy for hypocritically praising asceticism yet not acting upon it. Opposite to Russell on the foundations of mathematics, the Dutch mathematician L. E. J. Brouwer incorporated Kant's and Schopenhauer's ideas in the philosophical school of intuitionism, where mathematics is considered as a purely mental activity instead of an analytic activity wherein objective properties of reality are revealed. Brouwer was also influenced by Schopenhauer's metaphysics, and wrote an essay on mysticism. Schopenhauer's philosophy has made its way into a novel, The Schopenhauer Cure, by American existential psychiatrist and emeritus professor of psychiatry Irvin Yalom. Schopenhauer's philosophy, and the discussions on philosophical pessimism it has engendered, has been the focus of contemporary thinkers such as David Benatar, Thomas Ligotti, and Eugene Thacker. Their work also served as an inspiration for the popular HBO TV series True Detective. Selected bibliography On the Fourfold Root of the Principle of Sufficient Reason (Ueber die vierfache Wurzel des Satzes vom zureichenden Grunde), 1813 On Vision and Colors (Ueber das Sehn und die Farben), 1816 Theory of Colors (Theoria colorum), 1830. The World as Will and Representation (alternatively translated in English as The World as Will and Idea; original German is Die Welt als Wille und Vorstellung): vol. 1818–1819, vol. 2, 1844 Vol. 1 Dover edition 1966, Vol. 2 Dover edition 1966, Peter Smith Publisher hardcover set 1969, Everyman Paperback combined abridged edition (290 pp.) The Art of Being Right (Eristische Dialektik: Die Kunst, Recht zu Behalten), 1831 On the Will in Nature (Ueber den Willen in der Natur), 1836 On the Freedom of the Will (Ueber die Freiheit des menschlichen Willens), 1839 On the Basis of Morality (Ueber die Grundlage der Moral), 1840 The Two Basic Problems of Ethics: On the Freedom of the Will, On the Basis of Morality (Die beiden Grundprobleme der Ethik: Ueber die Freiheit des menschlichen Willens, Ueber das Fundament der Moral), 1841. Parerga and Paralipomena (2 vols., 1851) – Reprint: (Oxford: Clarendon Press) (2 vols., 1974) (English translation by E. F. J. Payne) Printings: 1974 Hardcover, by ISBN Vols. 1 and 2, , Vol. 1, ISBN Vol. 2, , 1974–1980 Paperback, Vol. 1, , Vol. 2, , 2001 Paperback, Vol. 1, , Vol. 2, Essays and Aphorisms, being excerpts from Volume 2 of Parerga und Paralipomena, selected and translated by R. J. Hollingdale, with Introduction by R J Hollingdale, Penguin Classics, 1970, Paperback 1973: An Enquiry concerning Ghost-seeing, and what is connected therewith (Versuch über das Geistersehn und was damit zusammenhangt), 1851 Arthur Schopenhauer, Manuscript Remains, Volume II, Berg Publishers Ltd., Online The Art Of Controversy (Die Kunst, Recht zu behalten). (bilingual) [The Art of Being Right] Studies in Pessimism – audiobook from LibriVox The World as Will and Idea at Internet Archive: Volume I Volume II Volume III On the fourfold root of the principle of sufficient reason and On the will in nature. Two essays: Internet Archive. Translated by Mrs. Karl Hillebrand (1903). Cornell University Library Historical Monographs Collection. Reprinted by Cornell University Library Digital Collections Facsimile edition of Schopenhauer's manuscripts in SchopenhauerSource Essays of Schopenhauer See also Antinatalism Existential nihilism Eye of a needle God in Buddhism Massacre of the Innocents (Guido Reni) Misotheism Mortal coil Nihilism Post-Schopenhauerian pessimism References Sources Albright, Daniel (2004) Modernism and Music: An Anthology of Sources. University of Chicago Press. Beiser, Frederick C., Weltschmerz: Pessimism in German Philosophy, 1860-1900 (Oxford: Oxford University Press, 2016). Hannan, Barbara, The Riddle of the World: A Reconsideration of Schopenhauer's Philosophy (Oxford: Oxford University Press, 2009). Magee, Bryan, Confessions of a Philosopher, Random House, 1998, . Chapters 20, 21. Safranski, Rüdiger (1990) Schopenhauer and the Wild Years of Philosophy. Harvard University Press, ; orig. German Schopenhauer und Die wilden Jahre der Philosophie, Carl Hanser Verlag (1987) Thomas Mann editor, The Living Thoughts of Schopenhauer, Longmans Green & Co., 1939 Further reading Biographies Cartwright, David. Schopenhauer: A Biography, Cambridge University Press, 2010. Frederick Copleston, Arthur Schopenhauer, philosopher of pessimism (Burns, Oates & Washbourne, 1946) O. F. Damm, Arthur Schopenhauer – eine Biographie (Reclam, 1912) Kuno Fischer, Arthur Schopenhauer (Heidelberg: Winter, 1893); revised as Schopenhauers Leben, Werke und Lehre (Heidelberg: Winter, 1898). Eduard Grisebach, Schopenhauer – Geschichte seines Lebens (Berlin: Hofmann, 1876). D. W. Hamlyn, Schopenhauer, London: Routledge & Kegan Paul (1980, 1985) Heinrich Hasse, Schopenhauer. (Reinhardt, 1926) Arthur Hübscher, Arthur Schopenhauer – Ein Lebensbild (Leipzig: Brockhaus, 1938). Thomas Mann, Schopenhauer (Bermann-Fischer, 1938) Matthews, Jack, Schopenhauer's Will: Das Testament, Nine Point Publishing, 2015. . A recent creative biography by philosophical novelist Jack Matthews. Rüdiger Safranski, Schopenhauer und die wilden Jahre der Philosophie – Eine Biographie, hard cover Carl Hanser Verlag, München 1987, , pocket edition Fischer: . Rüdiger Safranski, Schopenhauer and the Wild Years of Philosophy, trans. Ewald Osers (London: Weidenfeld and Nicolson, 1989) Walther Schneider, Schopenhauer – Eine Biographie (Vienna: Bermann-Fischer, 1937). William Wallace, Life of Arthur Schopenhauer (London: Scott, 1890; repr., St. Clair Shores, Mich.: Scholarly Press, 1970) Helen Zimmern, Arthur Schopenhauer: His Life and His Philosophy (London: Longmans, Green & Co, 1876) Other books App, Urs. Arthur Schopenhauer and China. Sino-Platonic Papers Nr. 200 (April 2010) (PDF, 8.7 Mb PDF, 164 p.). Contains extensive appendixes with transcriptions and English translations of Schopenhauer's early notes about Buddhism and Indian philosophy. Atwell, John. Schopenhauer on the Character of the World, The Metaphysics of Will. --------, Schopenhauer, The Human Character. Edwards, Anthony. An Evolutionary Epistemological Critique of Schopenhauer's Metaphysics. 123 Books, 2011. Copleston, Frederick, Schopenhauer: Philosopher of Pessimism, 1946 (reprinted London: Search Press, 1975). Gardiner, Patrick, 1963. Schopenhauer. Penguin Books. --------, Schopenhauer: A Very Short introduction. Janaway, Christopher, 2003. Self and World in Schopenhauer's Philosophy. Oxford University Press. Magee, Bryan, The Philosophy of Schopenhauer, Oxford University Press (1988, reprint 1997). Mannion, Gerard, "Schopenhauer, Religion and Morality – The Humble Path to Ethics", Ashgate Press, New Critical Thinking in Philosophy Series, 2003, 314pp. Trottier, Danick. L’influence de la philosophie schopenhauerienne dans la vie et l’oeuvre de Richard Wagner; et, Qu’est-ce qui séduit, obsède, magnétise le philosophe dans l’art des sons? deux études en esthétique musicale, Université du Québec à Montréal, Département de musique, 2000. Zimmern, Helen, Arthur Schopenhauer, his Life and Philosophy, London, Longman, and Co., 1876. Articles Jiménez, Camilo, 2006, "Tagebuch eines Ehrgeizigen: Arthur Schopenhauers Studienjahre in Berlin," Avinus Magazin (in German). Luchte, James, 2009, "The Body of Sublime Knowledge: The Aesthetic Phenomenology of Arthur Schopenhauer," Heythrop Journal, Volume 50, Number 2, pp. 228–242. Mazard, Eisel, 2005, "Schopenhauer and the Empirical Critique of Idealism in the History of Ideas." On Schopenhauer's (debated) place in the history of European philosophy and his relation to his predecessors. Moges, Awet, 2006, "Schopenhauer's Philosophy." Galileian Library. Sangharakshita, 2004, "Schopenhauer and aesthetic appreciation." Oxenford's "Iconoclasm in German Philosophy," (See p. 388) Thacker, Eugene, 2020. "A Philosophy in Ruins, An Unquiet Void." Introduction to Arthur Schopenhauer, On the Suffering of the World. Repeater Books. External links Arthur Schopenhauer an article by Mary Troxell in Internet Encyclopedia of Philosophy 2011 Schopenhauersource: Reproductions of Schopenhauer's manuscripts Kant's philosophy as rectified by Schopenhauer Timeline of German Philosophers A Quick Introduction to Schopenhauer Ross, Kelley L., 1998, "Arthur Schopenhauer (1788–1860)." Two short essays, on Schopenhauer's life and work, and on his dim view of academia. More Than 100 Years Later: A Schopenhauerian Revision of Breuer's Anna O 1788 births 1860 deaths 19th-century atheists 19th-century essayists 19th-century German male writers 19th-century German non-fiction writers 19th-century German philosophers 19th-century German writers 19th-century philosophers Aesthetics Animal rights scholars Anti-natalists Aphorists Atheist philosophers Burials at Frankfurt Main Cemetery Continental philosophers Critical theorists Critics of Christianity Critics of Judaism Critics of religions Cultural critics Epistemologists Flautists German atheist writers German Buddhists German scholars of Buddhism German ethicists German eugenicists German flautists German logicians German male essayists German male non-fiction writers German monarchists German people of Dutch descent German philologists Humboldt University of Berlin faculty Idealists Kantian philosophers Logicians Metaphilosophers Metaphysicians Monism Moral philosophers Ontologists Phenomenologists Philosophers of art Philosophers of culture Philosophers of education Philosophers of ethics and morality Philosophers of history Philosophers of language Philosophers of literature Philosophers of logic Philosophers of love Philosophers of mind Philosophers of pessimism Philosophers of psychology Philosophers of religion Philosophers of science Philosophy writers Political philosophers Simple living advocates German social commentators Social critics Social philosophers Theorists on Western civilization University of Göttingen alumni Writers from Gdańsk

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

713

https://en.wikipedia.org/wiki/Android%20%28robot%29

Android (robot)

An android is a humanoid robot or other artificial being often made from a flesh-like material. Historically, androids were completely within the domain of science fiction and frequently seen in film and television, but recent advances in robot technology now allow the design of functional and realistic humanoid robots. While the term "android" is used in reference to human-looking robots in general (not necessarily male-looking humanoid robots), a robot with a female appearance can also be referred to as a gynoid. Besides one can refer to robots without alluding to their sexual appearance by calling them anthrobots (merging the radical anthrōpos and the word robot; see anthrobotics) or anthropoids (short for anthropoid robots; the term humanoids is not appropriate because it is already commonly used to refer to human-like organic species in the context of scientific fiction, futurism and speculative astrobiology). Etymology The Oxford English Dictionary traces the earliest use (as "Androides") to Ephraim Chambers' 1728 Cyclopaedia, in reference to an automaton that St. Albertus Magnus allegedly created. By the late 1700s, "androides", elaborate mechanical devices resembling humans performing human activities, were displayed in exhibit halls. The term "android" appears in US patents as early as 1863 in reference to miniature human-like toy automatons. The term android was used in a more modern sense by the French author Auguste Villiers de l'Isle-Adam in his work Tomorrow's Eve (1886). This story features an artificial humanlike robot named Hadaly. As said by the officer in the story, "In this age of Realien advancement, who knows what goes on in the mind of those responsible for these mechanical dolls." The term made an impact into English pulp science fiction starting from Jack Williamson's The Cometeers (1936) and the distinction between mechanical robots and fleshy androids was popularized by Edmond Hamilton's Captain Future stories (1940–1944). Although Karel Čapek's robots in R.U.R. (Rossum's Universal Robots) (1921)—the play that introduced the word robot to the world—were organic artificial humans, the word "robot" has come to primarily refer to mechanical humans, animals, and other beings. The term "android" can mean either one of these, while a cyborg ("cybernetic organism" or "bionic man") would be a creature that is a combination of organic and mechanical parts. The term "droid", popularized by George Lucas in the original Star Wars film and now used widely within science fiction, originated as an abridgment of "android", but has been used by Lucas and others to mean any robot, including distinctly non-human form machines like R2-D2. The word "android" was used in Star Trek: The Original Series episode "What Are Little Girls Made Of?" The abbreviation "andy", coined as a pejorative by writer Philip K. Dick in his novel Do Androids Dream of Electric Sheep?, has seen some further usage, such as within the TV series Total Recall 2070. Authors have used the term android in more diverse ways than robot or cyborg. In some fictional works, the difference between a robot and android is only superficial, with androids being made to look like humans on the outside but with robot-like internal mechanics. In other stories, authors have used the word "android" to mean a wholly organic, yet artificial, creation. Other fictional depictions of androids fall somewhere in between. Eric G. Wilson, who defines an android as a "synthetic human being", distinguishes between three types of android, based on their body's composition: the mummy type – made of "dead things" or "stiff, inanimate, natural material", such as mummies, puppets, dolls and statues the golem type – made from flexible, possibly organic material, including golems and homunculi the automaton type – made from a mix of dead and living parts, including automatons and robots Although human morphology is not necessarily the ideal form for working robots, the fascination in developing robots that can mimic it can be found historically in the assimilation of two concepts: simulacra (devices that exhibit likeness) and automata (devices that have independence). Projects Several projects aiming to create androids that look, and, to a certain degree, speak or act like a human being have been launched or are underway. Japan Japanese robotics have been leading the field since the 1970s. Waseda University initiated the WABOT project in 1967, and in 1972 completed the WABOT-1, the first android, a full-scale humanoid intelligent robot. Its limb control system allowed it to walk with the lower limbs, and to grip and transport objects with hands, using tactile sensors. Its vision system allowed it to measure distances and directions to objects using external receptors, artificial eyes and ears. And its conversation system allowed it to communicate with a person in Japanese, with an artificial mouth. In 1984, WABOT-2 was revealed, and made a number of improvements. It was capable of playing the organ. Wabot-2 had ten fingers and two feet, and was able to read a score of music. It was also able to accompany a person. In 1986, Honda began its humanoid research and development program, to create humanoid robots capable of interacting successfully with humans. The Intelligent Robotics Lab, directed by Hiroshi Ishiguro at Osaka University, and the Kokoro company demonstrated the Actroid at Expo 2005 in Aichi Prefecture, Japan and released the Telenoid R1 in 2010. In 2006, Kokoro developed a new DER 2 android. The height of the human body part of DER2 is 165 cm. There are 47 mobile points. DER2 can not only change its expression but also move its hands and feet and twist its body. The "air servosystem" which Kokoro developed originally is used for the actuator. As a result of having an actuator controlled precisely with air pressure via a servosystem, the movement is very fluid and there is very little noise. DER2 realized a slimmer body than that of the former version by using a smaller cylinder. Outwardly DER2 has a more beautiful proportion. Compared to the previous model, DER2 has thinner arms and a wider repertoire of expressions. Once programmed, it is able to choreograph its motions and gestures with its voice. The Intelligent Mechatronics Lab, directed by Hiroshi Kobayashi at the Tokyo University of Science, has developed an android head called Saya, which was exhibited at Robodex 2002 in Yokohama, Japan. There are several other initiatives around the world involving humanoid research and development at this time, which will hopefully introduce a broader spectrum of realized technology in the near future. Now Saya is working at the Science University of Tokyo as a guide. The Waseda University (Japan) and NTT Docomo's manufacturers have succeeded in creating a shape-shifting robot WD-2. It is capable of changing its face. At first, the creators decided the positions of the necessary points to express the outline, eyes, nose, and so on of a certain person. The robot expresses its face by moving all points to the decided positions, they say. The first version of the robot was first developed back in 2003. After that, a year later, they made a couple of major improvements to the design. The robot features an elastic mask made from the average head dummy. It uses a driving system with a 3DOF unit. The WD-2 robot can change its facial features by activating specific facial points on a mask, with each point possessing three degrees of freedom. This one has 17 facial points, for a total of 56 degrees of freedom. As for the materials they used, the WD-2's mask is fabricated with a highly elastic material called Septom, with bits of steel wool mixed in for added strength. Other technical features reveal a shaft driven behind the mask at the desired facial point, driven by a DC motor with a simple pulley and a slide screw. Apparently, the researchers can also modify the shape of the mask based on actual human faces. To "copy" a face, they need only a 3D scanner to determine the locations of an individual's 17 facial points. After that, they are then driven into position using a laptop and 56 motor control boards. In addition, the researchers also mention that the shifting robot can even display an individual's hair style and skin color if a photo of their face is projected onto the 3D Mask. Singapore Prof Nadia Thalmann, a Nanyang Technological University scientist, directed efforts of the Institute for Media Innovation along with the School of Computer Engineering in the development of a social robot, Nadine. Nadine is powered by software similar to Apple's Siri or Microsoft's Cortana. Nadine may become a personal assistant in offices and homes in future, or she may become a companion for the young and the elderly. Assoc Prof Gerald Seet from the School of Mechanical & Aerospace Engineering and the BeingThere Centre led a three-year R&D development in tele-presence robotics, creating EDGAR. A remote user can control EDGAR with the user's face and expressions displayed on the robot's face in real time. The robot also mimics their upper body movements. South Korea KITECH researched and developed EveR-1, an android interpersonal communications model capable of emulating human emotional expression via facial "musculature" and capable of rudimentary conversation, having a vocabulary of around 400 words. She is tall and weighs , matching the average figure of a Korean woman in her twenties. EveR-1's name derives from the Biblical Eve, plus the letter r for robot. EveR-1's advanced computing processing power enables speech recognition and vocal synthesis, at the same time processing lip synchronization and visual recognition by 90-degree micro-CCD cameras with face recognition technology. An independent microchip inside her artificial brain handles gesture expression, body coordination, and emotion expression. Her whole body is made of highly advanced synthetic jelly silicon and with 60 artificial joints in her face, neck, and lower body; she is able to demonstrate realistic facial expressions and sing while simultaneously dancing. In South Korea, the Ministry of Information and Communication has an ambitious plan to put a robot in every household by 2020. Several robot cities have been planned for the country: the first will be built in 2016 at a cost of 500 billion won (US$440 million), of which 50 billion is direct government investment. The new robot city will feature research and development centers for manufacturers and part suppliers, as well as exhibition halls and a stadium for robot competitions. The country's new Robotics Ethics Charter will establish ground rules and laws for human interaction with robots in the future, setting standards for robotics users and manufacturers, as well as guidelines on ethical standards to be programmed into robots to prevent human abuse of robots and vice versa. United States Walt Disney and a staff of Imagineers created Great Moments with Mr. Lincoln that debuted at the 1964 New York World's Fair. Dr. William Barry, an Education Futurist and former visiting West Point Professor of Philosophy and Ethical Reasoning at the United States Military Academy, created an AI android character named "Maria Bot". This Interface AI android was named after the infamous fictional robot Maria in the 1927 film Metropolis, as a well-behaved distant relative. Maria Bot is the first AI Android Teaching Assistant at the university level. Maria Bot has appeared as a keynote speaker as a duo with Barry for a TEDx talk in Everett, Washington in February 2020. Resembling a human from the shoulders up, Maria Bot is a virtual being android that has complex facial expressions and head movement and engages in conversation about a variety of subjects. She uses AI to process and synthesize information to make her own decisions on how to talk and engage. She collects data through conversations, direct data inputs such as books or articles, and through internet sources. Maria Bot was built by an international high-tech company for Barry to help improve education quality and eliminate education poverty. Maria Bot is designed to create new ways for students to engage and discuss ethical issues raised by the increasing presence of robots and artificial intelligence. Barry also uses Maria Bot to demonstrate that programming a robot with life-affirming, ethical framework makes them more likely to help humans to do the same. Maria Bot is an ambassador robot for good and ethical AI technology. Hanson Robotics, Inc., of Texas and KAIST produced an android portrait of Albert Einstein, using Hanson's facial android technology mounted on KAIST's life-size walking bipedal robot body. This Einstein android, also called "Albert Hubo", thus represents the first full-body walking android in history. Hanson Robotics, the FedEx Institute of Technology, and the University of Texas at Arlington also developed the android portrait of sci-fi author Philip K. Dick (creator of Do Androids Dream of Electric Sheep?, the basis for the film Blade Runner), with full conversational capabilities that incorporated thousands of pages of the author's works. In 2005, the PKD android won a first-place artificial intelligence award from AAAI. Use in fiction Androids are a staple of science fiction. Isaac Asimov pioneered the fictionalization of the science of robotics and artificial intelligence, notably in his 1950s series I, Robot. One thing common to most fictional androids is that the real-life technological challenges associated with creating thoroughly human-like robots—such as the creation of strong artificial intelligence—are assumed to have been solved. Fictional androids are often depicted as mentally and physically equal or superior to humans—moving, thinking and speaking as fluidly as them. The tension between the nonhuman substance and the human appearance—or even human ambitions—of androids is the dramatic impetus behind most of their fictional depictions. Some android heroes seek, like Pinocchio, to become human, as in the film Bicentennial Man, or Data in Star Trek: The Next Generation. Others, as in the film Westworld, rebel against abuse by careless humans. Android hunter Deckard in Do Androids Dream of Electric Sheep? and its film adaptation Blade Runner discovers that his targets appear to be, in some ways, more "human" than he is. Android stories, therefore, are not essentially stories "about" androids; they are stories about the human condition and what it means to be human. One aspect of writing about the meaning of humanity is to use discrimination against androids as a mechanism for exploring racism in society, as in Blade Runner. Perhaps the clearest example of this is John Brunner's 1968 novel Into the Slave Nebula, where the blue-skinned android slaves are explicitly shown to be fully human. More recently, the androids Bishop and Annalee Call in the films Aliens and Alien Resurrection are used as vehicles for exploring how humans deal with the presence of an "Other". The 2018 video game Detroit: Become Human also explores how androids are treated as second class citizens in a near future society. Female androids, or "gynoids", are often seen in science fiction, and can be viewed as a continuation of the long tradition of men attempting to create the stereotypical "perfect woman". Examples include the Greek myth of Pygmalion and the female robot Maria in Fritz Lang's Metropolis. Some gynoids, like Pris in Blade Runner, are designed as sex-objects, with the intent of "pleasing men's violent sexual desires", or as submissive, servile companions, such as in The Stepford Wives. Fiction about gynoids has therefore been described as reinforcing "essentialist ideas of femininity", although others have suggested that the treatment of androids is a way of exploring racism and misogyny in society. The 2015 Japanese film Sayonara, starring Geminoid F, was promoted as "the first movie to feature an android performing opposite a human actor". See also References Further reading Kerman, Judith B. (1991). Retrofitting Blade Runner: Issues in Ridley Scott's Blade Runner and Philip K. Dick's Do Androids Dream of Electric Sheep? Bowling Green, OH: Bowling Green State University Popular Press. . Perkowitz, Sidney (2004). Digital People: From Bionic Humans to Androids. Joseph Henry Press. . Shelde, Per (1993). Androids, Humanoids, and Other Science Fiction Monsters: Science and Soul in Science Fiction Films. New York: New York University Press. . Ishiguro, Hiroshi. "Android science." Cognitive Science Society. 2005. Glaser, Horst Albert and Rossbach, Sabine: The Artificial Human, Frankfurt/M., Bern, New York 2011 "The Artificial Human" TechCast Article Series, Jason Rupinski and Richard Mix, "Public Attitudes to Androids: Robot Gender, Tasks, & Pricing" An-droid, "Similar to the Android name" Carpenter, J. (2009). Why send the Terminator to do R2D2s job?: Designing androids as rhetorical phenomena. Proceedings of HCI 2009: Beyond Gray Droids: Domestic Robot Design for the 21st Century. Cambridge, UK. 1 September. Telotte, J.P. Replications: A Robotic History of the Science Fiction Film. University of Illinois Press, 1995. External links Japanese inventions South Korean inventions Osaka University research Science fiction themes Human–machine interaction Robots

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

736

https://en.wikipedia.org/wiki/Albert%20Einstein

Albert Einstein

Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest physicists of all time. Einstein is best known for developing the theory of relativity, but he also made important contributions to the development of the theory of quantum mechanics. Relativity and quantum mechanics are together the two pillars of modern physics. His mass–energy equivalence formula , which arises from relativity theory, has been dubbed "the world's most famous equation". His work is also known for its influence on the philosophy of science. He received the 1921 Nobel Prize in Physics "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect", a pivotal step in the development of quantum theory. His intellectual achievements and originality resulted in "Einstein" becoming synonymous with "genius". In 1905, a year sometimes described as his annus mirabilis ('miracle year'), Einstein published four groundbreaking papers. These outlined the theory of the photoelectric effect, explained Brownian motion, introduced special relativity, and demonstrated mass-energy equivalence. Einstein thought that the laws of classical mechanics could no longer be reconciled with those of the electromagnetic field, which led him to develop his special theory of relativity. He then extended the theory to gravitational fields; he published a paper on general relativity in 1916, introducing his theory of gravitation. In 1917, he applied the general theory of relativity to model the structure of the universe. He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules. He also investigated the thermal properties of light and the quantum theory of radiation, which laid the foundation of the photon theory of light. However, for much of the later part of his career, he worked on two ultimately unsuccessful endeavors. First, despite his great contributions to quantum mechanics, he opposed what it evolved into, objecting that nature "does not play dice". Second, he attempted to devise a unified field theory by generalizing his geometric theory of gravitation to include electromagnetism. As a result, he became increasingly isolated from the mainstream of modern physics. Einstein was born in the German Empire, but moved to Switzerland in 1895, forsaking his German citizenship (as a subject of the Kingdom of Württemberg) the following year. In 1897, at the age of 17, he enrolled in the mathematics and physics teaching diploma program at the Swiss Federal polytechnic school in Zürich, graduating in 1900. In 1901, he acquired Swiss citizenship, which he kept for the rest of his life, and in 1903 he secured a permanent position at the Swiss Patent Office in Bern. In 1905, he was awarded a PhD by the University of Zurich. In 1914, Einstein moved to Berlin in order to join the Prussian Academy of Sciences and the Humboldt University of Berlin. In 1917, Einstein became director of the Kaiser Wilhelm Institute for Physics; he also became a German citizen again, this time Prussian. In 1933, while Einstein was visiting the United States, Adolf Hitler came to power in Germany. Einstein, of Jewish origin, objected to the policies of the newly elected Nazi government; he settled in the United States and became an American citizen in 1940. On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential German nuclear weapons program and recommending that the US begin similar research. Einstein supported the Allies but generally denounced the idea of nuclear weapons. Life and career Early life and education Albert Einstein was born in Ulm, in the Kingdom of Württemberg in the German Empire, on 14 March 1879 into a family of secular Ashkenazi Jews. His parents were Hermann Einstein, a salesman and engineer, and Pauline Koch. In 1880, the family moved to Munich, where Einstein's father and his uncle Jakob founded Elektrotechnische Fabrik J. Einstein & Cie, a company that manufactured electrical equipment based on direct current. Albert attended a Catholic elementary school in Munich, from the age of five, for three years. At the age of eight, he was transferred to the Luitpold Gymnasium (now known as the Albert Einstein Gymnasium), where he received advanced primary and secondary school education until he left the German Empire seven years later. In 1894, Hermann and Jakob's company lost a bid to supply the city of Munich with electrical lighting because they lacked the capital to convert their equipment from the direct current (DC) standard to the more efficient alternating current (AC) standard. The loss forced the sale of the Munich factory. In search of business, the Einstein family moved to Italy, first to Milan and a few months later to Pavia. When the family moved to Pavia, Einstein, then 15, stayed in Munich to finish his studies at the Luitpold Gymnasium. His father intended for him to pursue electrical engineering, but Einstein clashed with the authorities and resented the school's regimen and teaching method. He later wrote that the spirit of learning and creative thought was lost in strict rote learning. At the end of December 1894, he traveled to Italy to join his family in Pavia, convincing the school to let him go by using a doctor's note. During his time in Italy he wrote a short essay with the title "On the Investigation of the State of the Ether in a Magnetic Field". Einstein excelled at math and physics from a young age, reaching a mathematical level years ahead of his peers. The 12-year-old Einstein taught himself algebra and Euclidean geometry over a single summer. Einstein also independently discovered his own original proof of the Pythagorean theorem at age 12. A family tutor Max Talmud says that after he had given the 12-year-old Einstein a geometry textbook, after a short time "[Einstein] had worked through the whole book. He thereupon devoted himself to higher mathematics... Soon the flight of his mathematical genius was so high I could not follow." His passion for geometry and algebra led the 12-year-old to become convinced that nature could be understood as a "mathematical structure". Einstein started teaching himself calculus at 12, and as a 14-year-old he says he had "mastered integral and differential calculus". At age 13, when he had become more seriously interested in philosophy (and music), Einstein was introduced to Kant's Critique of Pure Reason. Kant became his favorite philosopher, his tutor stating: "At the time he was still a child, only thirteen years old, yet Kant's works, incomprehensible to ordinary mortals, seemed to be clear to him." In 1895, at the age of 16, Einstein took the entrance examinations for the Swiss Federal polytechnic school in Zürich (later the Eidgenössische Technische Hochschule, ETH). He failed to reach the required standard in the general part of the examination, but obtained exceptional grades in physics and mathematics. On the advice of the principal of the polytechnic school, he attended the Argovian cantonal school (gymnasium) in Aarau, Switzerland, in 1895 and 1896 to complete his secondary schooling. While lodging with the family of Professor Jost Winteler, he fell in love with Winteler's daughter, Marie. Albert's sister Maja later married Winteler's son Paul. In January 1896, with his father's approval, Einstein renounced his citizenship in the German Kingdom of Württemberg to avoid military service. In September 1896 he passed the Swiss Matura with mostly good grades, including a top grade of 6 in physics and mathematical subjects, on a scale of 1–6. At 17, he enrolled in the four-year mathematics and physics teaching diploma program at the Federal polytechnic school. Marie Winteler, who was a year older, moved to Olsberg, Switzerland, for a teaching post. Einstein's future wife, a 20-year-old Serbian named Mileva Marić, also enrolled at the polytechnic school that year. She was the only woman among the six students in the mathematics and physics section of the teaching diploma course. Over the next few years, Einstein's and Marić's friendship developed into a romance, and they spent countless hours debating and reading books together on extra-curricular physics in which they were both interested. Einstein wrote in his letters to Marić that he preferred studying alongside her. In 1900, Einstein passed the exams in Maths and Physics and was awarded a Federal teaching diploma. There is eyewitness evidence and several letters over many years that indicate Marić might have collaborated with Einstein prior to his landmark 1905 papers, known as the Annus Mirabilis papers, and that they developed some of the concepts together during their studies, although some historians of physics who have studied the issue disagree that she made any substantive contributions. Marriages and children Early correspondence between Einstein and Marić was discovered and published in 1987 which revealed that the couple had a daughter named "Lieserl", born in early 1902 in Novi Sad where Marić was staying with her parents. Marić returned to Switzerland without the child, whose real name and fate are unknown. The contents of Einstein's letter in September 1903 suggest that the girl was either given up for adoption or died of scarlet fever in infancy. Einstein and Marić married in January 1903. In May 1904, their son Hans Albert Einstein was born in Bern, Switzerland. Their son Eduard was born in Zürich in July 1910. The couple moved to Berlin in April 1914, but Marić returned to Zürich with their sons after learning that, despite their close relationship before, Einstein's chief romantic attraction was now his cousin Elsa Löwenthal; she was his first cousin maternally and second cousin paternally. Einstein and Marić divorced on 14 February 1919, having lived apart for five years. As part of the divorce settlement, Einstein agreed to give Marić his future (in the event, 1921) Nobel Prize money. In letters revealed in 2015, Einstein wrote to his early love Marie Winteler about his marriage and his strong feelings for her. He wrote in 1910, while his wife was pregnant with their second child: "I think of you in heartfelt love every spare minute and am so unhappy as only a man can be." He spoke about a "misguided love" and a "missed life" regarding his love for Marie. Einstein married Löwenthal in 1919, after having had a relationship with her since 1912. They emigrated to the United States in 1933. Elsa was diagnosed with heart and kidney problems in 1935 and died in December 1936. In 1923, Einstein fell in love with a secretary named Betty Neumann, the niece of a close friend, Hans Mühsam. In a volume of letters released by Hebrew University of Jerusalem in 2006, Einstein described about six women, including Margarete Lebach (a blonde Austrian), Estella Katzenellenbogen (the rich owner of a florist business), Toni Mendel (a wealthy Jewish widow) and Ethel Michanowski (a Berlin socialite), with whom he spent time and from whom he received gifts while being married to Elsa. Later, after the death of his second wife Elsa, Einstein was briefly in a relationship with Margarita Konenkova. Konenkova was a Russian spy who was married to the noted Russian sculptor Sergei Konenkov (who created the bronze bust of Einstein at the Institute for Advanced Study at Princeton). Einstein's son Eduard had a breakdown at about age 20 and was diagnosed with schizophrenia. His mother cared for him and he was also committed to asylums for several periods, finally being committed permanently after her death. Patent office After graduating in 1900, Einstein spent almost two frustrating years searching for a teaching post. He acquired Swiss citizenship in February 1901, but was not conscripted for medical reasons. With the help of Marcel Grossmann's father, he secured a job in Bern at the Swiss Patent Office, as an assistant examiner – level III. Einstein evaluated patent applications for a variety of devices including a gravel sorter and an electromechanical typewriter. In 1903, his position at the Swiss Patent Office became permanent, although he was passed over for promotion until he "fully mastered machine technology". Much of his work at the patent office related to questions about transmission of electric signals and electrical-mechanical synchronization of time, two technical problems that show up conspicuously in the thought experiments that eventually led Einstein to his radical conclusions about the nature of light and the fundamental connection between space and time. With a few friends he had met in Bern, Einstein started a small discussion group in 1902, self-mockingly named "The Olympia Academy", which met regularly to discuss science and philosophy. Sometimes they were joined by Mileva who attentively listened but did not participate. Their readings included the works of Henri Poincaré, Ernst Mach, and David Hume, which influenced his scientific and philosophical outlook. First scientific papers In 1900, Einstein's paper "Folgerungen aus den Capillaritätserscheinungen" ("Conclusions from the Capillarity Phenomena") was published in the journal Annalen der Physik. On 30 April 1905, Einstein completed his dissertation, A New Determination of Molecular Dimensions with Alfred Kleiner, Professor of Experimental Physics at the University of Zürich, serving as pro-forma advisor. His work was accepted in July, and Einstein was awarded a Ph.D. Also in 1905, which has been called Einstein's annus mirabilis (amazing year), he published four groundbreaking papers, on the photoelectric effect, Brownian motion, special relativity, and the equivalence of mass and energy, which were to bring him to the notice of the academic world, at the age of 26. Academic career By 1908, he was recognized as a leading scientist and was appointed lecturer at the University of Bern. The following year, after he gave a lecture on electrodynamics and the relativity principle at the University of Zurich, Alfred Kleiner recommended him to the faculty for a newly created professorship in theoretical physics. Einstein was appointed associate professor in 1909. Einstein became a full professor at the German Charles-Ferdinand University in Prague in April 1911, accepting Austrian citizenship in the Austro-Hungarian Empire to do so. During his Prague stay, he wrote 11 scientific works, five of them on radiation mathematics and on the quantum theory of solids. In July 1912, he returned to his alma mater in Zürich. From 1912 until 1914, he was a professor of theoretical physics at the ETH Zurich, where he taught analytical mechanics and thermodynamics. He also studied continuum mechanics, the molecular theory of heat, and the problem of gravitation, on which he worked with mathematician and friend Marcel Grossmann. When the "Manifesto of the Ninety-Three" was published in October 1914—a document signed by a host of prominent German intellectuals that justified Germany's militarism and position during the First World War—Einstein was one of the few German intellectuals to rebut its contents and sign the pacifistic "Manifesto to the Europeans". In the spring of 1913, Einstein was enticed to move to Berlin with an offer that included membership in the Prussian Academy of Sciences, and a linked University of Berlin professorship, enabling him to concentrate exclusively on research. On 3 July 1913, he became a member of the Prussian Academy of Sciences in Berlin. Max Planck and Walther Nernst visited him the next week in Zurich to persuade him to join the academy, additionally offering him the post of director at the Kaiser Wilhelm Institute for Physics, which was soon to be established. Membership in the academy included paid salary and professorship without teaching duties at Humboldt University of Berlin. He was officially elected to the academy on 24 July, and he moved to Berlin the following year. His decision to move to Berlin was also influenced by the prospect of living near his cousin Elsa, with whom he had started a romantic affair. Einstein assumed his position with the academy, and Berlin University, after moving into his Dahlem apartment on 1 April 1914. As World War I broke out that year, the plan for Kaiser Wilhelm Institute for Physics was aborted. The institute was established on 1 October 1917, with Einstein as its director. In 1916, Einstein was elected president of the German Physical Society (1916–1918). In 1911, Einstein used his 1907 Equivalence principle to calculate the deflection of light from another star by the Sun's gravity. In 1913, Einstein improved upon those calculations by using Riemannian space-time to represent the gravity field. By the fall of 1915, Einstein had successfully completed his general theory of relativity, which he used to calculate that deflection, and the perihelion precession of Mercury. In 1919, that deflection prediction was confirmed by Sir Arthur Eddington during the solar eclipse of 29 May 1919. Those observations were published in the international media, making Einstein world-famous. On 7 November 1919, the leading British newspaper The Times printed a banner headline that read: "Revolution in Science – New Theory of the Universe – Newtonian Ideas Overthrown". In 1920, he became a Foreign Member of the Royal Netherlands Academy of Arts and Sciences. In 1922, he was awarded the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect". While the general theory of relativity was still considered somewhat controversial, the citation also does not treat even the cited photoelectric work as an explanation but merely as a discovery of the law, as the idea of photons was considered outlandish and did not receive universal acceptance until the 1924 derivation of the Planck spectrum by S. N. Bose. Einstein was elected a Foreign Member of the Royal Society (ForMemRS) in 1921. He also received the Copley Medal from the Royal Society in 1925. Einstein resigned from the Prussian Academy in March 1933. Einstein's scientific accomplishments while in Berlin, included finishing the general theory of relativity, proving the gyromagnetic effect, contributing to the quantum theory of radiation, and Bose–Einstein statistics. 1921–1922: Travels abroad Einstein visited New York City for the first time on 2 April 1921, where he received an official welcome by Mayor John Francis Hylan, followed by three weeks of lectures and receptions. He went on to deliver several lectures at Columbia University and Princeton University, and in Washington, he accompanied representatives of the National Academy of Sciences on a visit to the White House. On his return to Europe he was the guest of the British statesman and philosopher Viscount Haldane in London, where he met several renowned scientific, intellectual, and political figures, and delivered a lecture at King's College London. He also published an essay, "My First Impression of the U.S.A.", in July 1921, in which he tried briefly to describe some characteristics of Americans, much as had Alexis de Tocqueville, who published his own impressions in Democracy in America (1835). For some of his observations, Einstein was clearly surprised: "What strikes a visitor is the joyous, positive attitude to life ... The American is friendly, self-confident, optimistic, and without envy." In 1922, his travels took him to Asia and later to Palestine, as part of a six-month excursion and speaking tour, as he visited Singapore, Ceylon and Japan, where he gave a series of lectures to thousands of Japanese. After his first public lecture, he met the emperor and empress at the Imperial Palace, where thousands came to watch. In a letter to his sons, he described his impression of the Japanese as being modest, intelligent, considerate, and having a true feel for art. In his own travel diaries from his 1922–23 visit to Asia, he expresses some views on the Chinese, Japanese and Indian people, which have been described as xenophobic and racist judgments when they were rediscovered in 2018. Because of Einstein's travels to the Far East, he was unable to personally accept the Nobel Prize for Physics at the Stockholm award ceremony in December 1922. In his place, the banquet speech was made by a German diplomat, who praised Einstein not only as a scientist but also as an international peacemaker and activist. On his return voyage, he visited Palestine for 12 days, his only visit to that region. He was greeted as if he were a head of state, rather than a physicist, which included a cannon salute upon arriving at the home of the British high commissioner, Sir Herbert Samuel. During one reception, the building was stormed by people who wanted to see and hear him. In Einstein's talk to the audience, he expressed happiness that the Jewish people were beginning to be recognized as a force in the world. Einstein visited Spain for two weeks in 1923, where he briefly met Santiago Ramón y Cajal and also received a diploma from King Alfonso XIII naming him a member of the Spanish Academy of Sciences. From 1922 to 1932, Einstein was a member of the International Committee on Intellectual Cooperation of the League of Nations in Geneva (with a few months of interruption in 1923–1924), a body created to promote international exchange between scientists, researchers, teachers, artists, and intellectuals. Originally slated to serve as the Swiss delegate, Secretary-General Eric Drummond was persuaded by Catholic activists Oskar Halecki and Giuseppe Motta to instead have him become the German delegate, thus allowing Gonzague de Reynold to take the Swiss spot, from which he promoted traditionalist Catholic values. Einstein's former physics professor Hendrik Lorentz and the Polish chemist Marie Curie were also members of the committee. 1925: Visit to South America In the months of March and April 1925, Einstein visited South America, where he spent about a month in Argentina, a week in Uruguay, and a week in Rio de Janeiro, Brazil. Einstein's visit was initiated by Jorge Duclout (1856–1927) and Mauricio Nirenstein (1877–1935) with the support of several Argentine scholars, including Julio Rey Pastor, Jakob Laub, and Leopoldo Lugones. The visit by Einstein and his wife was financed primarily by the Council of the University of Buenos Aires and the Asociación Hebraica Argentina (Argentine Hebraic Association) with a smaller contribution from the Argentine-Germanic Cultural Institution. 1930–1931: Travel to the US In December 1930, Einstein visited America for the second time, originally intended as a two-month working visit as a research fellow at the California Institute of Technology. After the national attention, he received during his first trip to the US, he and his arrangers aimed to protect his privacy. Although swamped with telegrams and invitations to receive awards or speak publicly, he declined them all. After arriving in New York City, Einstein was taken to various places and events, including Chinatown, a lunch with the editors of The New York Times, and a performance of Carmen at the Metropolitan Opera, where he was cheered by the audience on his arrival. During the days following, he was given the keys to the city by Mayor Jimmy Walker and met the president of Columbia University, who described Einstein as "the ruling monarch of the mind". Harry Emerson Fosdick, pastor at New York's Riverside Church, gave Einstein a tour of the church and showed him a full-size statue that the church made of Einstein, standing at the entrance. Also during his stay in New York, he joined a crowd of 15,000 people at Madison Square Garden during a Hanukkah celebration. Einstein next traveled to California, where he met Caltech president and Nobel laureate Robert A. Millikan. His friendship with Millikan was "awkward", as Millikan "had a penchant for patriotic militarism", where Einstein was a pronounced pacifist. During an address to Caltech's students, Einstein noted that science was often inclined to do more harm than good. This aversion to war also led Einstein to befriend author Upton Sinclair and film star Charlie Chaplin, both noted for their pacifism. Carl Laemmle, head of Universal Studios, gave Einstein a tour of his studio and introduced him to Chaplin. They had an instant rapport, with Chaplin inviting Einstein and his wife, Elsa, to his home for dinner. Chaplin said Einstein's outward persona, calm and gentle, seemed to conceal a "highly emotional temperament", from which came his "extraordinary intellectual energy". Chaplin's film, City Lights, was to premiere a few days later in Hollywood, and Chaplin invited Einstein and Elsa to join him as his special guests. Walter Isaacson, Einstein's biographer, described this as "one of the most memorable scenes in the new era of celebrity". Chaplin visited Einstein at his home on a later trip to Berlin and recalled his "modest little flat" and the piano at which he had begun writing his theory. Chaplin speculated that it was "possibly used as kindling wood by the Nazis". 1933: Emigration to the US In February 1933, while on a visit to the United States, Einstein knew he could not return to Germany with the rise to power of the Nazis under Germany's new chancellor, Adolf Hitler. While at American universities in early 1933, he undertook his third two-month visiting professorship at the California Institute of Technology in Pasadena. In February and March 1933, the Gestapo repeatedly raided his family's apartment in Berlin. He and his wife Elsa returned to Europe in March, and during the trip, they learned that the German Reichstag had passed the Enabling Act on 23 March, transforming Hitler's government into a de facto legal dictatorship, and that they would not be able to proceed to Berlin. Later on, they heard that their cottage had been raided by the Nazis and Einstein's personal sailboat confiscated. Upon landing in Antwerp, Belgium on 28 March, Einstein immediately went to the German consulate and surrendered his passport, formally renouncing his German citizenship. The Nazis later sold his boat and converted his cottage into a Hitler Youth camp. Refugee status In April 1933, Einstein discovered that the new German government had passed laws barring Jews from holding any official positions, including teaching at universities. Historian Gerald Holton describes how, with "virtually no audible protest being raised by their colleagues", thousands of Jewish scientists were suddenly forced to give up their university positions and their names were removed from the rolls of institutions where they were employed. A month later, Einstein's works were among those targeted by the German Student Union in the Nazi book burnings, with Nazi propaganda minister Joseph Goebbels proclaiming, "Jewish intellectualism is dead." One German magazine included him in a list of enemies of the German regime with the phrase, "not yet hanged", offering a $5,000 bounty on his head. In a subsequent letter to physicist and friend Max Born, who had already emigrated from Germany to England, Einstein wrote, "... I must confess that the degree of their brutality and cowardice came as something of a surprise." After moving to the US, he described the book burnings as a "spontaneous emotional outburst" by those who "shun popular enlightenment", and "more than anything else in the world, fear the influence of men of intellectual independence". Einstein was now without a permanent home, unsure where he would live and work, and equally worried about the fate of countless other scientists still in Germany. He rented a house in De Haan, Belgium, where he lived for a few months. In late July 1933, he went to England for about six weeks at the personal invitation of British naval officer Commander Oliver Locker-Lampson, who had become friends with Einstein in the preceding years. Locker-Lampson invited him to stay near his home in a wooden cabin on Roughton Heath in the Parish of . To protect Einstein, Locker-Lampson had two bodyguards watch over him at his secluded cabin; a photo of them carrying shotguns and guarding Einstein was published in the Daily Herald on 24 July 1933. Locker-Lampson took Einstein to meet Winston Churchill at his home, and later, Austen Chamberlain and former Prime Minister Lloyd George. Einstein asked them to help bring Jewish scientists out of Germany. British historian Martin Gilbert notes that Churchill responded immediately, and sent his friend, physicist Frederick Lindemann, to Germany to seek out Jewish scientists and place them in British universities. Churchill later observed that as a result of Germany having driven the Jews out, they had lowered their "technical standards" and put the Allies' technology ahead of theirs. Einstein later contacted leaders of other nations, including Turkey's Prime Minister, İsmet İnönü, to whom he wrote in September 1933 requesting placement of unemployed German-Jewish scientists. As a result of Einstein's letter, Jewish invitees to Turkey eventually totaled over "1,000 saved individuals". Locker-Lampson also submitted a bill to parliament to extend British citizenship to Einstein, during which period Einstein made a number of public appearances describing the crisis brewing in Europe. In one of his speeches he denounced Germany's treatment of Jews, while at the same time he introduced a bill promoting Jewish citizenship in Palestine, as they were being denied citizenship elsewhere. In his speech he described Einstein as a "citizen of the world" who should be offered a temporary shelter in the UK. Both bills failed, however, and Einstein then accepted an earlier offer from the Institute for Advanced Study, in Princeton, New Jersey, US, to become a resident scholar. Resident scholar at the Institute for Advanced Study In October 1933, Einstein returned to the US and took up a position at the Institute for Advanced Study, noted for having become a refuge for scientists fleeing Nazi Germany. At the time, most American universities, including Harvard, Princeton and Yale, had minimal or no Jewish faculty or students, as a result of their Jewish quotas, which lasted until the late 1940s. Einstein was still undecided on his future. He had offers from several European universities, including Christ Church, Oxford, where he stayed for three short periods between May 1931 and June 1933 and was offered a five-year studentship, but in 1935, he arrived at the decision to remain permanently in the United States and apply for citizenship. Einstein's affiliation with the Institute for Advanced Study would last until his death in 1955. He was one of the four first selected (along with John von Neumann and Kurt Gödel) at the new Institute, where he soon developed a close friendship with Gödel. The two would take long walks together discussing their work. Bruria Kaufman, his assistant, later became a physicist. During this period, Einstein tried to develop a unified field theory and to refute the accepted interpretation of quantum physics, both unsuccessfully. World War II and the Manhattan Project In 1939, a group of Hungarian scientists that included émigré physicist Leó Szilárd attempted to alert Washington to ongoing Nazi atomic bomb research. The group's warnings were discounted. Einstein and Szilárd, along with other refugees such as Edward Teller and Eugene Wigner, "regarded it as their responsibility to alert Americans to the possibility that German scientists might win the race to build an atomic bomb, and to warn that Hitler would be more than willing to resort to such a weapon." To make certain the US was aware of the danger, in July 1939, a few months before the beginning of World War II in Europe, Szilárd and Wigner visited Einstein to explain the possibility of atomic bombs, which Einstein, a pacifist, said he had never considered. He was asked to lend his support by writing a letter, with Szilárd, to President Roosevelt, recommending the US pay attention and engage in its own nuclear weapons research. The letter is believed to be "arguably the key stimulus for the U.S. adoption of serious investigations into nuclear weapons on the eve of the U.S. entry into World War II". In addition to the letter, Einstein used his connections with the Belgian Royal Family and the Belgian queen mother to get access with a personal envoy to the White House's Oval Office. Some say that as a result of Einstein's letter and his meetings with Roosevelt, the US entered the "race" to develop the bomb, drawing on its "immense material, financial, and scientific resources" to initiate the Manhattan Project. For Einstein, "war was a disease ... [and] he called for resistance to war." By signing the letter to Roosevelt, some argue he went against his pacifist principles. In 1954, a year before his death, Einstein said to his old friend, Linus Pauling, "I made one great mistake in my life—when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification—the danger that the Germans would make them ..." In 1955, Einstein and ten other intellectuals and scientists, including British philosopher Bertrand Russell, signed a manifesto highlighting the danger of nuclear weapons. US citizenship Einstein became an American citizen in 1940. Not long after settling into his career at the Institute for Advanced Study in Princeton, New Jersey, he expressed his appreciation of the meritocracy in American culture when compared to Europe. He recognized the "right of individuals to say and think what they pleased", without social barriers, and as a result, individuals were encouraged, he said, to be more creative, a trait he valued from his own early education. Einstein joined the National Association for the Advancement of Colored People (NAACP) in Princeton, where he campaigned for the civil rights of African Americans. He considered racism America's "worst disease", seeing it as "handed down from one generation to the next". As part of his involvement, he corresponded with civil rights activist W. E. B. Du Bois and was prepared to testify on his behalf during his trial in 1951. When Einstein offered to be a character witness for Du Bois, the judge decided to drop the case. In 1946, Einstein visited Lincoln University in Pennsylvania, a historically black college, where he was awarded an honorary degree. Lincoln was the first university in the United States to grant college degrees to African Americans; alumni include Langston Hughes and Thurgood Marshall. Einstein gave a speech about racism in America, adding, "I do not intend to be quiet about it." A resident of Princeton recalls that Einstein had once paid the college tuition for a black student. Einstein has said "Being a Jew myself, perhaps I can understand and empathize with how black people feel as victims of discrimination". Personal life Assisting Zionist causes Einstein was a figurehead leader in helping establish the Hebrew University of Jerusalem, which opened in 1925 and was among its first Board of Governors. Earlier, in 1921, he was asked by the biochemist and president of the World Zionist Organization, Chaim Weizmann, to help raise funds for the planned university. He also submitted various suggestions as to its initial programs. Among those, he advised first creating an Institute of Agriculture in order to settle the undeveloped land. That should be followed, he suggested, by a Chemical Institute and an Institute of Microbiology, to fight the various ongoing epidemics such as malaria, which he called an "evil" that was undermining a third of the country's development. Establishing an Oriental Studies Institute, to include language courses given in both Hebrew and Arabic, for scientific exploration of the country and its historical monuments, was also important. Einstein was not a nationalist; he was against the creation of an independent Jewish state, which would be established without his help as Israel in 1948. Einstein felt that the waves of arriving Jews of the Aliyah could live alongside existing Arabs in Palestine. His views were not shared by the majority of Jews seeking to form a new country; as a result, Einstein was limited to a marginal role in the Zionist movement. Chaim Weizmann later became Israel's first president. Upon his death while in office in November 1952 and at the urging of Ezriel Carlebach, Prime Minister David Ben-Gurion offered Einstein the position of President of Israel, a mostly ceremonial post. The offer was presented by Israel's ambassador in Washington, Abba Eban, who explained that the offer "embodies the deepest respect which the Jewish people can repose in any of its sons". Einstein declined, and wrote in his response that he was "deeply moved", and "at once saddened and ashamed" that he could not accept it. Love of music Einstein developed an appreciation for music at an early age. In his late journals he wrote: "If I were not a physicist, I would probably be a musician. I often think in music. I live my daydreams in music. I see my life in terms of music... I get most joy in life out of music." His mother played the piano reasonably well and wanted her son to learn the violin, not only to instill in him a love of music but also to help him assimilate into German culture. According to conductor Leon Botstein, Einstein began playing when he was 5. However, he did not enjoy it at that age. When he turned 13, he discovered the violin sonatas of Mozart, whereupon he became enamored of Mozart's compositions and studied music more willingly. Einstein taught himself to play without "ever practicing systematically". He said that "love is a better teacher than a sense of duty." At age 17, he was heard by a school examiner in Aarau while playing Beethoven's violin sonatas. The examiner stated afterward that his playing was "remarkable and revealing of 'great insight. What struck the examiner, writes Botstein, was that Einstein "displayed a deep love of the music, a quality that was and remains in short supply. Music possessed an unusual meaning for this student." Music took on a pivotal and permanent role in Einstein's life from that period on. Although the idea of becoming a professional musician himself was not on his mind at any time, among those with whom Einstein played chamber music were a few professionals, and he performed for private audiences and friends. Chamber music had also become a regular part of his social life while living in Bern, Zürich, and Berlin, where he played with Max Planck and his son, among others. He is sometimes erroneously credited as the editor of the 1937 edition of the Köchel catalog of Mozart's work; that edition was prepared by Alfred Einstein, who may have been a distant relation. In 1931, while engaged in research at the California Institute of Technology, he visited the Zoellner family conservatory in Los Angeles, where he played some of Beethoven and Mozart's works with members of the Zoellner Quartet. Near the end of his life, when the young Juilliard Quartet visited him in Princeton, he played his violin with them, and the quartet was "impressed by Einstein's level of coordination and intonation". Political views In 1918, Einstein was one of the founding members of the German Democratic Party, a liberal party. Later in his life, Einstein's political view was in favor of socialism and critical of capitalism, which he detailed in his essays such as "Why Socialism?" His opinions on the Bolsheviks also changed with time. In 1925, he criticized them for not having a 'well-regulated system of government' and called their rule a 'regime of terror and a tragedy in human history'. He later adopted a more moderated view, criticizing their methods but praising them, which is shown by his 1929 remark on Vladimir Lenin: "In Lenin I honor a man, who in total sacrifice of his own person has committed his entire energy to realizing social justice. I do not find his methods advisable. One thing is certain, however: men like him are the guardians and renewers of mankind's conscience." Einstein offered and was called on to give judgments and opinions on matters often unrelated to theoretical physics or mathematics. He strongly advocated the idea of a democratic global government that would check the power of nation-states in the framework of a world federation. He wrote "I advocate world government because I am convinced that there is no other possible way of eliminating the most terrible danger in which man has ever found himself." The FBI created a secret dossier on Einstein in 1932, and by the time of his death his FBI file was 1,427 pages long. Einstein was deeply impressed by Mahatma Gandhi, with whom he exchanged written letters. He described Gandhi as "a role model for the generations to come". The initial connection was established on 27 September 1931, when Wilfrid Israel took his Indian guest V. A. Sundaram to meet his friend Einstein at his summer home in the town of Caputh. Sundaram was Gandhi's disciple and special envoy, whom Wilfrid Israel met while visiting India and visiting the Indian leader's home in 1925. During the visit, Einstein wrote a short letter to Gandhi that was delivered to him through his envoy, and Gandhi responded quickly with his own letter. Although in the end Einstein and Gandhi were unable to meet as they had hoped, the direct connection between them was established through Wilfrid Israel. Religious and philosophical views Einstein spoke of his spiritual outlook in a wide array of original writings and interviews. He said he had sympathy for the impersonal pantheistic God of Baruch Spinoza's philosophy. He did not believe in a personal god who concerns himself with fates and actions of human beings, a view which he described as naïve. He clarified, however, that "I am not an atheist", preferring to call himself an agnostic, or a "deeply religious nonbeliever". When asked if he believed in an afterlife, Einstein replied, "No. And one life is enough for me." Einstein was primarily affiliated with non-religious humanist and Ethical Culture groups in both the UK and US. He served on the advisory board of the First Humanist Society of New York, and was an honorary associate of the Rationalist Association, which publishes New Humanist in Britain. For the 75th anniversary of the New York Society for Ethical Culture, he stated that the idea of Ethical Culture embodied his personal conception of what is most valuable and enduring in religious idealism. He observed, "Without 'ethical culture' there is no salvation for humanity." In a German-language letter to philosopher Eric Gutkind, dated 3 January 1954, Einstein wrote:The word God is for me nothing more than the expression and product of human weaknesses, the Bible a collection of honorable, but still primitive legends which are nevertheless pretty childish. No interpretation no matter how subtle can (for me) change this. ... For me the Jewish religion like all other religions is an incarnation of the most childish superstitions. And the Jewish people to whom I gladly belong and with whose mentality I have a deep affinity have no different quality for me than all other people. ... I cannot see anything 'chosen' about them. Death On 17 April 1955, Einstein experienced internal bleeding caused by the rupture of an abdominal aortic aneurysm, which had previously been reinforced surgically by Rudolph Nissen in 1948. He took the draft of a speech he was preparing for a television appearance commemorating the state of Israel's seventh anniversary with him to the hospital, but he did not live to complete it. Einstein refused surgery, saying, "I want to go when I want. It is tasteless to prolong life artificially. I have done my share; it is time to go. I will do it elegantly." He died in Penn Medicine Princeton Medical Center early the next morning at the age of 76, having continued to work until near the end. During the autopsy, the pathologist Thomas Stoltz Harvey removed Einstein's brain for preservation without the permission of his family, in the hope that the neuroscience of the future would be able to discover what made Einstein so intelligent. Einstein's remains were cremated in Trenton, New Jersey, and his ashes were scattered at an undisclosed location. In a memorial lecture delivered on 13 December 1965 at UNESCO headquarters, nuclear physicist J. Robert Oppenheimer summarized his impression of Einstein as a person: "He was almost wholly without sophistication and wholly without worldliness ... There was always with him a wonderful purity at once childlike and profoundly stubborn." Einstein bequeathed his personal archives, library and intellectual assets to the Hebrew University of Jerusalem in Israel. Scientific career Throughout his life, Einstein published hundreds of books and articles. He published more than 300 scientific papers and 150 non-scientific ones. On 5 December 2014, universities and archives announced the release of Einstein's papers, comprising more than 30,000 unique documents. Einstein's intellectual achievements and originality have made the word "Einstein" synonymous with "genius". In addition to the work he did by himself he also collaborated with other scientists on additional projects including the Bose–Einstein statistics, the Einstein refrigerator and others. 1905 – Annus Mirabilis papers The Annus Mirabilis papers are four articles pertaining to the photoelectric effect (which gave rise to quantum theory), Brownian motion, the special theory of relativity, and E = mc2 that Einstein published in the Annalen der Physik scientific journal in 1905. These four works contributed substantially to the foundation of modern physics and changed views on space, time, and matter. The four papers are: Statistical mechanics Thermodynamic fluctuations and statistical physics Einstein's first paper submitted in 1900 to Annalen der Physik was on capillary attraction. It was published in 1901 with the title "Folgerungen aus den Capillaritätserscheinungen", which translates as "Conclusions from the capillarity phenomena". Two papers he published in 1902–1903 (thermodynamics) attempted to interpret atomic phenomena from a statistical point of view. These papers were the foundation for the 1905 paper on Brownian motion, which showed that Brownian movement can be construed as firm evidence that molecules exist. His research in 1903 and 1904 was mainly concerned with the effect of finite atomic size on diffusion phenomena. Theory of critical opalescence Einstein returned to the problem of thermodynamic fluctuations, giving a treatment of the density variations in a fluid at its critical point. Ordinarily the density fluctuations are controlled by the second derivative of the free energy with respect to the density. At the critical point, this derivative is zero, leading to large fluctuations. The effect of density fluctuations is that light of all wavelengths is scattered, making the fluid look milky white. Einstein relates this to Rayleigh scattering, which is what happens when the fluctuation size is much smaller than the wavelength, and which explains why the sky is blue. Einstein quantitatively derived critical opalescence from a treatment of density fluctuations, and demonstrated how both the effect and Rayleigh scattering originate from the atomistic constitution of matter. Special relativity Einstein's "Zur Elektrodynamik bewegter Körper" ("On the Electrodynamics of Moving Bodies") was received on 30 June 1905 and published 26 September of that same year. It reconciled conflicts between Maxwell's equations (the laws of electricity and magnetism) and the laws of Newtonian mechanics by introducing changes to the laws of mechanics. Observationally, the effects of these changes are most apparent at high speeds (where objects are moving at speeds close to the speed of light). The theory developed in this paper later became known as Einstein's special theory of relativity. There is evidence from Einstein's writings that he collaborated with his first wife, Mileva Marić, on this work. The decision to publish only under his name seems to have been mutual, but the exact reason is unknown. This paper predicted that, when measured in the frame of a relatively moving observer, a clock carried by a moving body would appear to slow down, and the body itself would contract in its direction of motion. This paper also argued that the idea of a luminiferous aether—one of the leading theoretical entities in physics at the time—was superfluous. In his paper on mass–energy equivalence, Einstein produced E = mc2 as a consequence of his special relativity equations. Einstein's 1905 work on relativity remained controversial for many years, but was accepted by leading physicists, starting with Max Planck. Einstein originally framed special relativity in terms of kinematics (the study of moving bodies). In 1908, Hermann Minkowski reinterpreted special relativity in geometric terms as a theory of spacetime. Einstein adopted Minkowski's formalism in his 1915 general theory of relativity. General relativity General relativity and the equivalence principle General relativity (GR) is a theory of gravitation that was developed by Einstein between 1907 and 1915. According to general relativity, the observed gravitational attraction between masses results from the warping of space and time by those masses. General relativity has developed into an essential tool in modern astrophysics. It provides the foundation for the current understanding of black holes, regions of space where gravitational attraction is so strong that not even light can escape. As Einstein later said, the reason for the development of general relativity was that the preference of inertial motions within special relativity was unsatisfactory, while a theory which from the outset prefers no state of motion (even accelerated ones) should appear more satisfactory. Consequently, in 1907 he published an article on acceleration under special relativity. In that article titled "On the Relativity Principle and the Conclusions Drawn from It", he argued that free fall is really inertial motion, and that for a free-falling observer the rules of special relativity must apply. This argument is called the equivalence principle. In the same article, Einstein also predicted the phenomena of gravitational time dilation, gravitational redshift and deflection of light. In 1911, Einstein published another article "On the Influence of Gravitation on the Propagation of Light" expanding on the 1907 article, in which he estimated the amount of deflection of light by massive bodies. Thus, the theoretical prediction of general relativity could for the first time be tested experimentally. Gravitational waves In 1916, Einstein predicted gravitational waves, ripples in the curvature of spacetime which propagate as waves, traveling outward from the source, transporting energy as gravitational radiation. The existence of gravitational waves is possible under general relativity due to its Lorentz invariance which brings the concept of a finite speed of propagation of the physical interactions of gravity with it. By contrast, gravitational waves cannot exist in the Newtonian theory of gravitation, which postulates that the physical interactions of gravity propagate at infinite speed. The first, indirect, detection of gravitational waves came in the 1970s through observation of a pair of closely orbiting neutron stars, PSR B1913+16. The explanation of the decay in their orbital period was that they were emitting gravitational waves. Einstein's prediction was confirmed on 11 February 2016, when researchers at LIGO published the first observation of gravitational waves, detected on Earth on 14 September 2015, nearly one hundred years after the prediction. Hole argument and Entwurf theory While developing general relativity, Einstein became confused about the gauge invariance in the theory. He formulated an argument that led him to conclude that a general relativistic field theory is impossible. He gave up looking for fully generally covariant tensor equations and searched for equations that would be invariant under general linear transformations only. In June 1913, the Entwurf ('draft') theory was the result of these investigations. As its name suggests, it was a sketch of a theory, less elegant and more difficult than general relativity, with the equations of motion supplemented by additional gauge fixing conditions. After more than two years of intensive work, Einstein realized that the hole argument was mistaken and abandoned the theory in November 1915. Physical cosmology In 1917, Einstein applied the general theory of relativity to the structure of the universe as a whole. He discovered that the general field equations predicted a universe that was dynamic, either contracting or expanding. As observational evidence for a dynamic universe was not known at the time, Einstein introduced a new term, the cosmological constant, to the field equations, in order to allow the theory to predict a static universe. The modified field equations predicted a static universe of closed curvature, in accordance with Einstein's understanding of Mach's principle in these years. This model became known as the Einstein World or Einstein's static universe. Following the discovery of the recession of the nebulae by Edwin Hubble in 1929, Einstein abandoned his static model of the universe, and proposed two dynamic models of the cosmos, The Friedmann-Einstein universe of 1931 and the Einstein–de Sitter universe of 1932. In each of these models, Einstein discarded the cosmological constant, claiming that it was "in any case theoretically unsatisfactory". In many Einstein biographies, it is claimed that Einstein referred to the cosmological constant in later years as his "biggest blunder". The astrophysicist Mario Livio has recently cast doubt on this claim, suggesting that it may be exaggerated. In late 2013, a team led by the Irish physicist Cormac O'Raifeartaigh discovered evidence that, shortly after learning of Hubble's observations of the recession of the nebulae, Einstein considered a steady-state model of the universe. In a hitherto overlooked manuscript, apparently written in early 1931, Einstein explored a model of the expanding universe in which the density of matter remains constant due to a continuous creation of matter, a process he associated with the cosmological constant. As he stated in the paper, "In what follows, I would like to draw attention to a solution to equation (1) that can account for Hubbel's [sic] facts, and in which the density is constant over time" ... "If one considers a physically bounded volume, particles of matter will be continually leaving it. For the density to remain constant, new particles of matter must be continually formed in the volume from space." It thus appears that Einstein considered a steady-state model of the expanding universe many years before Hoyle, Bondi and Gold. However, Einstein's steady-state model contained a fundamental flaw and he quickly abandoned the idea. Energy momentum pseudotensor General relativity includes a dynamical spacetime, so it is difficult to see how to identify the conserved energy and momentum. Noether's theorem allows these quantities to be determined from a Lagrangian with translation invariance, but general covariance makes translation invariance into something of a gauge symmetry. The energy and momentum derived within general relativity by Noether's prescriptions do not make a real tensor for this reason. Einstein argued that this is true for a fundamental reason: the gravitational field could be made to vanish by a choice of coordinates. He maintained that the non-covariant energy momentum pseudotensor was, in fact, the best description of the energy momentum distribution in a gravitational field. This approach has been echoed by Lev Landau and Evgeny Lifshitz, and others, and has become standard. The use of non-covariant objects like pseudotensors was heavily criticized in 1917 by Erwin Schrödinger and others. Wormholes In 1935, Einstein collaborated with Nathan Rosen to produce a model of a wormhole, often called Einstein–Rosen bridges. His motivation was to model elementary particles with charge as a solution of gravitational field equations, in line with the program outlined in the paper "Do Gravitational Fields play an Important Role in the Constitution of the Elementary Particles?". These solutions cut and pasted Schwarzschild black holes to make a bridge between two patches. If one end of a wormhole was positively charged, the other end would be negatively charged. These properties led Einstein to believe that pairs of particles and antiparticles could be described in this way. Einstein–Cartan theory In order to incorporate spinning point particles into general relativity, the affine connection needed to be generalized to include an antisymmetric part, called the torsion. This modification was made by Einstein and Cartan in the 1920s. Equations of motion The theory of general relativity has a fundamental lawthe Einstein field equations, which describe how space curves. The geodesic equation, which describes how particles move, may be derived from the Einstein field equations. Since the equations of general relativity are non-linear, a lump of energy made out of pure gravitational fields, like a black hole, would move on a trajectory which is determined by the Einstein field equations themselves, not by a new law. So Einstein proposed that the path of a singular solution, like a black hole, would be determined to be a geodesic from general relativity itself. This was established by Einstein, Infeld, and Hoffmann for pointlike objects without angular momentum, and by Roy Kerr for spinning objects. Old quantum theory Photons and energy quanta In a 1905 paper, Einstein postulated that light itself consists of localized particles (quanta). Einstein's light quanta were nearly universally rejected by all physicists, including Max Planck and Niels Bohr. This idea only became universally accepted in 1919, with Robert Millikan's detailed experiments on the photoelectric effect, and with the measurement of Compton scattering. Einstein concluded that each wave of frequency f is associated with a collection of photons with energy hf each, where h is Planck's constant. He does not say much more, because he is not sure how the particles are related to the wave. But he does suggest that this idea would explain certain experimental results, notably the photoelectric effect. Quantized atomic vibrations In 1907, Einstein proposed a model of matter where each atom in a lattice structure is an independent harmonic oscillator. In the Einstein model, each atom oscillates independently—a series of equally spaced quantized states for each oscillator. Einstein was aware that getting the frequency of the actual oscillations would be difficult, but he nevertheless proposed this theory because it was a particularly clear demonstration that quantum mechanics could solve the specific heat problem in classical mechanics. Peter Debye refined this model. Adiabatic principle and action-angle variables Throughout the 1910s, quantum mechanics expanded in scope to cover many different systems. After Ernest Rutherford discovered the nucleus and proposed that electrons orbit like planets, Niels Bohr was able to show that the same quantum mechanical postulates introduced by Planck and developed by Einstein would explain the discrete motion of electrons in atoms, and the periodic table of the elements. Einstein contributed to these developments by linking them with the 1898 arguments Wilhelm Wien had made. Wien had shown that the hypothesis of adiabatic invariance of a thermal equilibrium state allows all the blackbody curves at different temperature to be derived from one another by a simple shifting process. Einstein noted in 1911 that the same adiabatic principle shows that the quantity which is quantized in any mechanical motion must be an adiabatic invariant. Arnold Sommerfeld identified this adiabatic invariant as the action variable of classical mechanics. Bose–Einstein statistics In 1924, Einstein received a description of a statistical model from Indian physicist Satyendra Nath Bose, based on a counting method that assumed that light could be understood as a gas of indistinguishable particles. Einstein noted that Bose's statistics applied to some atoms as well as to the proposed light particles, and submitted his translation of Bose's paper to the Zeitschrift für Physik. Einstein also published his own articles describing the model and its implications, among them the Bose–Einstein condensate phenomenon that some particulates should appear at very low temperatures. It was not until 1995 that the first such condensate was produced experimentally by Eric Allin Cornell and Carl Wieman using ultra-cooling equipment built at the NIST–JILA laboratory at the University of Colorado at Boulder. Bose–Einstein statistics are now used to describe the behaviors of any assembly of bosons. Einstein's sketches for this project may be seen in the Einstein Archive in the library of the Leiden University. Wave–particle duality Although the patent office promoted Einstein to Technical Examiner Second Class in 1906, he had not given up on academia. In 1908, he became a Privatdozent at the University of Bern. In "Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung" ("The Development of our Views on the Composition and Essence of Radiation"), on the quantization of light, and in an earlier 1909 paper, Einstein showed that Max Planck's energy quanta must have well-defined momenta and act in some respects as independent, point-like particles. This paper introduced the photon concept (although the name photon was introduced later by Gilbert N. Lewis in 1926) and inspired the notion of wave–particle duality in quantum mechanics. Einstein saw this wave–particle duality in radiation as concrete evidence for his conviction that physics needed a new, unified foundation. Zero-point energy In a series of works completed from 1911 to 1913, Planck reformulated his 1900 quantum theory and introduced the idea of zero-point energy in his "second quantum theory". Soon, this idea attracted the attention of Einstein and his assistant Otto Stern. Assuming the energy of rotating diatomic molecules contains zero-point energy, they then compared the theoretical specific heat of hydrogen gas with the experimental data. The numbers matched nicely. However, after publishing the findings, they promptly withdrew their support, because they no longer had confidence in the correctness of the idea of zero-point energy. Stimulated emission In 1917, at the height of his work on relativity, Einstein published an article in Physikalische Zeitschrift that proposed the possibility of stimulated emission, the physical process that makes possible the maser and the laser. This article showed that the statistics of absorption and emission of light would only be consistent with Planck's distribution law if the emission of light into a mode with n photons would be enhanced statistically compared to the emission of light into an empty mode. This paper was enormously influential in the later development of quantum mechanics, because it was the first paper to show that the statistics of atomic transitions had simple laws. Matter waves Einstein discovered Louis de Broglie's work and supported his ideas, which were received skeptically at first. In another major paper from this era, Einstein gave a wave equation for de Broglie waves, which Einstein suggested was the Hamilton–Jacobi equation of mechanics. This paper would inspire Schrödinger's work of 1926. Quantum mechanics Einstein's objections to quantum mechanics Einstein played a major role in developing quantum theory, beginning with his 1905 paper on the photoelectric effect. However, he became displeased with modern quantum mechanics as it had evolved after 1925, despite its acceptance by other physicists. He was skeptical that the randomness of quantum mechanics was fundamental rather than the result of determinism, stating that God "is not playing at dice". Until the end of his life, he continued to maintain that quantum mechanics was incomplete. Bohr versus Einstein The Bohr–Einstein debates were a series of public disputes about quantum mechanics between Einstein and Niels Bohr, who were two of its founders. Their debates are remembered because of their importance to the philosophy of science. Their debates would influence later interpretations of quantum mechanics. Einstein–Podolsky–Rosen paradox In 1935, Einstein returned to quantum mechanics, in particular to the question of its completeness, in the "EPR paper". In a thought experiment, he considered two particles, which had interacted such that their properties were strongly correlated. No matter how far the two particles were separated, a precise position measurement on one particle would result in equally precise knowledge of the position of the other particle; likewise, a precise momentum measurement of one particle would result in equally precise knowledge of the momentum of the other particle, without needing to disturb the other particle in any way. Given Einstein's concept of local realism, there were two possibilities: (1) either the other particle had these properties already determined, or (2) the process of measuring the first particle instantaneously affected the reality of the position and momentum of the second particle. Einstein rejected this second possibility (popularly called "spooky action at a distance"). Einstein's belief in local realism led him to assert that, while the correctness of quantum mechanics was not in question, it must be incomplete. But as a physical principle, local realism was shown to be incorrect when the Aspect experiment of 1982 confirmed Bell's theorem, which J. S. Bell had delineated in 1964. The results of these and subsequent experiments demonstrate that quantum physics cannot be represented by any version of the picture of physics in which "particles are regarded as unconnected independent classical-like entities, each one being unable to communicate with the other after they have separated." Although Einstein was wrong about local realism, his clear prediction of the unusual properties of its opposite, entangled quantum states, has resulted in the EPR paper becoming among the top ten papers published in Physical Review. It is considered a centerpiece of the development of quantum information theory. Unified field theory Following his research on general relativity, Einstein attempted to generalize his theory of gravitation to include electromagnetism as aspects of a single entity. In 1950, he described his "unified field theory" in a Scientific American article titled "On the Generalized Theory of Gravitation". Although he was lauded for this work, his efforts were ultimately unsuccessful. Notably, Einstein's unification project did not accommodate the strong and weak nuclear forces, neither of which were well understood until many years after his death. Although mainstream physics long ignored Einstein's approaches to unification, Einstein's work has motivated modern quests for a theory of everything, in particular string theory, where geometrical fields emerge in a unified quantum-mechanical setting. Other investigations Einstein conducted other investigations that were unsuccessful and abandoned. These pertain to force, superconductivity, and other research. Collaboration with other scientists In addition to longtime collaborators Leopold Infeld, Nathan Rosen, Peter Bergmann and others, Einstein also had some one-shot collaborations with various scientists. Einstein–de Haas experiment Einstein and De Haas demonstrated that magnetization is due to the motion of electrons, nowadays known to be the spin. In order to show this, they reversed the magnetization in an iron bar suspended on a torsion pendulum. They confirmed that this leads the bar to rotate, because the electron's angular momentum changes as the magnetization changes. This experiment needed to be sensitive because the angular momentum associated with electrons is small, but it definitively established that electron motion of some kind is responsible for magnetization. Schrödinger gas model Einstein suggested to Erwin Schrödinger that he might be able to reproduce the statistics of a Bose–Einstein gas by considering a box. Then to each possible quantum motion of a particle in a box associate an independent harmonic oscillator. Quantizing these oscillators, each level will have an integer occupation number, which will be the number of particles in it. This formulation is a form of second quantization, but it predates modern quantum mechanics. Erwin Schrödinger applied this to derive the thermodynamic properties of a semiclassical ideal gas. Schrödinger urged Einstein to add his name as co-author, although Einstein declined the invitation. Einstein refrigerator In 1926, Einstein and his former student Leó Szilárd co-invented (and in 1930, patented) the Einstein refrigerator. This absorption refrigerator was then revolutionary for having no moving parts and using only heat as an input. On 11 November 1930, was awarded to Einstein and Leó Szilárd for the refrigerator. Their invention was not immediately put into commercial production, and the most promising of their patents were acquired by the Swedish company Electrolux. Non-scientific legacy While traveling, Einstein wrote daily to his wife Elsa and adopted stepdaughters Margot and Ilse. The letters were included in the papers bequeathed to the Hebrew University of Jerusalem. Margot Einstein permitted the personal letters to be made available to the public, but requested that it not be done until twenty years after her death (she died in 1986). Barbara Wolff, of the Hebrew University's Albert Einstein Archives, told the BBC that there are about 3,500 pages of private correspondence written between 1912 and 1955. Einstein's right of publicity was litigated in 2015 in a federal district court in California. Although the court initially held that the right had expired, that ruling was immediately appealed, and the decision was later vacated in its entirety. The underlying claims between the parties in that lawsuit were ultimately settled. The right is enforceable, and the Hebrew University of Jerusalem is the exclusive representative of that right. Corbis, successor to The Roger Richman Agency, licenses the use of his name and associated imagery, as agent for the university. In popular culture Einstein became one of the most famous scientific celebrities, beginning with the confirmation of his theory of general relativity in 1919. Despite the general public having little understanding of his work, he was widely recognized and received adulation and publicity. In the period before World War II, The New Yorker published a vignette in their "The Talk of the Town" feature saying that Einstein was so well known in America that he would be stopped on the street by people wanting him to explain "that theory". He finally figured out a way to handle the incessant inquiries. He told his inquirers "Pardon me, sorry! Always I am mistaken for Professor Einstein." Einstein has been the subject of or inspiration for many novels, films, plays, and works of music. He is a favorite model for depictions of absent-minded professors; his expressive face and distinctive hairstyle have been widely copied and exaggerated. Time magazine's Frederic Golden wrote that Einstein was "a cartoonist's dream come true". Many popular quotations are often misattributed to him. Awards and honors Einstein received numerous awards and honors, and in 1922, he was awarded the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect". None of the nominations in 1921 met the criteria set by Alfred Nobel, so the 1921 prize was carried forward and awarded to Einstein in 1922. Publications Scientific First of a series of papers on this topic. A reprint of this book was published by Edition Erbrich in 1982, . . Further information about the volumes published so far can be found on the webpages of the Einstein Papers Project and on the Princeton University Press Einstein Page Others . The chasing a light beam thought experiment is described on pages 48–51. See also Albert Einstein House in Princeton Einstein's thought experiments Einstein notation The Einstein Theory of Relativity, an educational film Frist Campus Center at Princeton University room 302 is associated with Einstein. (The center was once the Palmer Physical Laboratory.) Heinrich Burkhardt Bern Historical Museum (Einstein Museum) History of gravitational theory List of coupled cousins List of German inventors and discoverers Jewish Nobel laureates List of peace activists Relativity priority dispute Sticky bead argument Notes References Works cited Further reading , or External links Einstein's Personal Correspondence: Religion, Politics, The Holocaust, and Philosophy Shapell Manuscript Foundation Federal Bureau of Investigation file on Albert Einstein Einstein and his love of music, Physics World including the Nobel Lecture 11 July 1923 Fundamental ideas and problems of the theory of relativity Albert Einstein Archives Online (80,000+ Documents) (MSNBC, 19 March 2012) Einstein's declaration of intention for American citizenship on the World Digital Library Albert Einstein Collection at Brandeis University The Collected Papers of Albert Einstein "Digital Einstein" at Princeton University Home page of Albert Einstein at The Institute for Advanced Study Albert – The Digital Repository of the IAS, which contains many digitized original documents and photographs 1879 births 1955 deaths 20th-century American engineers 20th-century American physicists 20th-century American writers American agnostics American humanists American letter writers American Nobel laureates American pacifists American relativity theorists American science writers American Zionists American Ashkenazi Jews Charles University faculty Swiss cosmologists Deaths from abdominal aortic aneurysm Albert ETH Zurich alumni ETH Zurich faculty German agnostics German Ashkenazi Jews German emigrants to Switzerland German humanists 19th-century German Jews German Nobel laureates German relativity theorists Institute for Advanced Study faculty Jewish agnostics Jewish American physicists Jewish emigrants from Nazi Germany to the United States Jewish physicists Members of the Royal Netherlands Academy of Arts and Sciences Members of the United States National Academy of Sciences Naturalised citizens of Austria Naturalised citizens of Switzerland Naturalized citizens of the United States New Jersey Hall of Fame inductees Nobel laureates in Physics Pantheists Patent examiners People who lost German citizenship Philosophers of mathematics Philosophers of science Philosophy of science Quantum physicists Scientists from Munich Spinozists Stateless people Denaturalized citizens of Germany Swiss agnostics Swiss emigrants to the United States Swiss Ashkenazi Jews 20th-century Swiss inventors 20th-century American inventors Swiss physicists Winners of the Max Planck Medal Google Doodles University of Zurich alumni University of Bern faculty University of Zurich faculty Swiss Nobel laureates Pipe smokers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

742

https://en.wikipedia.org/wiki/Algorithms%20%28journal%29

Algorithms (journal)

Algorithms is a monthly peer-reviewed open-access scientific journal of mathematics, covering design, analysis, and experiments on algorithms. The journal is published by MDPI and was established in 2008. The founding editor-in-chief was Kazuo Iwama (Kyoto University). From May 2014 to September 2019, the editor-in-chief was Henning Fernau (Universität Trier). The current editor-in-chief is Frank Werner (Otto-von-Guericke-Universität Magdeburg). Abstracting and indexing The journal is abstracted and indexed in: See also Journals with similar scope include: ACM Transactions on Algorithms Algorithmica Journal of Algorithms (Elsevier) References External links Computer science journals Open access journals MDPI academic journals English-language journals Publications established in 2008 Mathematics journals Monthly journals

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

752

https://en.wikipedia.org/wiki/Art

Art

Art is a diverse range of human activity, and resulting product, that involves creative or imaginative talent expressive of technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of what constitutes art, and ideas have changed over time. The three classical branches of visual art are painting, sculpture, and architecture. Theatre, dance, and other performing arts, as well as literature, music, film and other media such as interactive media, are included in a broader definition of the arts. Until the 17th century, art referred to any skill or mastery and was not differentiated from crafts or sciences. In modern usage after the 17th century, where aesthetic considerations are paramount, the fine arts are separated and distinguished from acquired skills in general, such as the decorative or applied arts. The nature of art and related concepts, such as creativity and interpretation, are explored in a branch of philosophy known as aesthetics. The resulting artworks are studied in the professional fields of art criticism and the history of art. Overview In the perspective of the history of art, artistic works have existed for almost as long as humankind: from early pre-historic art to contemporary art; however, some theorists feel that the typical concept of "artistic works" fits less well outside modern Western societies. One early sense of the definition of art is closely related to the older Latin meaning, which roughly translates to "skill" or "craft", as associated with words such as "artisan". English words derived from this meaning include artifact, artificial, artifice, medical arts, and military arts. However, there are many other colloquial uses of the word, all with some relation to its etymology. Over time, philosophers like Plato, Aristotle, Socrates and Kant, among others, questioned the meaning of art. Several dialogues in Plato tackle questions about art: Socrates says that poetry is inspired by the muses, and is not rational. He speaks approvingly of this, and other forms of divine madness (drunkenness, eroticism, and dreaming) in the Phaedrus (265a–c), and yet in the Republic wants to outlaw Homer's great poetic art, and laughter as well. In Ion, Socrates gives no hint of the disapproval of Homer that he expresses in the Republic. The dialogue Ion suggests that Homer's Iliad functioned in the ancient Greek world as the Bible does today in the modern Christian world: as divinely inspired literary art that can provide moral guidance, if only it can be properly interpreted. With regards to the literary art and the musical arts, Aristotle considered epic poetry, tragedy, comedy, Dithyrambic poetry and music to be mimetic or imitative art, each varying in imitation by medium, object, and manner. For example, music imitates with the media of rhythm and harmony, whereas dance imitates with rhythm alone, and poetry with language. The forms also differ in their object of imitation. Comedy, for instance, is a dramatic imitation of men worse than average; whereas tragedy imitates men slightly better than average. Lastly, the forms differ in their manner of imitation—through narrative or character, through change or no change, and through drama or no drama. Aristotle believed that imitation is natural to mankind and constitutes one of mankind's advantages over animals. The more recent and specific sense of the word art as an abbreviation for creative art or fine art emerged in the early 17th century. Fine art refers to a skill used to express the artist's creativity, or to engage the audience's aesthetic sensibilities, or to draw the audience towards consideration of more refined or finer work of art. Within this latter sense, the word art may refer to several things: (i) a study of a creative skill, (ii) a process of using the creative skill, (iii) a product of the creative skill, or (iv) the audience's experience with the creative skill. The creative arts (art as discipline) are a collection of disciplines which produce artworks (art as objects) that are compelled by a personal drive (art as activity) and convey a message, mood, or symbolism for the perceiver to interpret (art as experience). Art is something that stimulates an individual's thoughts, emotions, beliefs, or ideas through the senses. Works of art can be explicitly made for this purpose or interpreted on the basis of images or objects. For some scholars, such as Kant, the sciences and the arts could be distinguished by taking science as representing the domain of knowledge and the arts as representing the domain of the freedom of artistic expression. Often, if the skill is being used in a common or practical way, people will consider it a craft instead of art. Likewise, if the skill is being used in a commercial or industrial way, it may be considered commercial art instead of fine art. On the other hand, crafts and design are sometimes considered applied art. Some art followers have argued that the difference between fine art and applied art has more to do with value judgments made about the art than any clear definitional difference. However, even fine art often has goals beyond pure creativity and self-expression. The purpose of works of art may be to communicate ideas, such as in politically, spiritually, or philosophically motivated art; to create a sense of beauty (see aesthetics); to explore the nature of perception; for pleasure; or to generate strong emotions. The purpose may also be seemingly nonexistent. The nature of art has been described by philosopher Richard Wollheim as "one of the most elusive of the traditional problems of human culture". Art has been defined as a vehicle for the expression or communication of emotions and ideas, a means for exploring and appreciating formal elements for their own sake, and as mimesis or representation. Art as mimesis has deep roots in the philosophy of Aristotle. Leo Tolstoy identified art as a use of indirect means to communicate from one person to another. Benedetto Croce and R. G. Collingwood advanced the idealist view that art expresses emotions, and that the work of art therefore essentially exists in the mind of the creator. The theory of art as form has its roots in the philosophy of Kant, and was developed in the early 20th century by Roger Fry and Clive Bell. More recently, thinkers influenced by Martin Heidegger have interpreted art as the means by which a community develops for itself a medium for self-expression and interpretation. George Dickie has offered an institutional theory of art that defines a work of art as any artifact upon which a qualified person or persons acting on behalf of the social institution commonly referred to as "the art world" has conferred "the status of candidate for appreciation". Larry Shiner has described fine art as "not an essence or a fate but something we have made. Art as we have generally understood it is a European invention barely two hundred years old." Art may be characterized in terms of mimesis (its representation of reality), narrative (storytelling), expression, communication of emotion, or other qualities. During the Romantic period, art came to be seen as "a special faculty of the human mind to be classified with religion and science". History A shell engraved by Homo erectus was determined to be between 430,000 and 540,000 years old. A set of eight 130,000 years old white-tailed eagle talons bear cut marks and abrasion that indicate manipulation by neanderthals, possibly for using it as jewelry. A series of tiny, drilled snail shells about 75,000 years old—were discovered in a South African cave. Containers that may have been used to hold paints have been found dating as far back as 100,000 years. Sculptures, cave paintings, rock paintings and petroglyphs from the Upper Paleolithic dating to roughly 40,000 years ago have been found, but the precise meaning of such art is often disputed because so little is known about the cultures that produced them. Many great traditions in art have a foundation in the art of one of the great ancient civilizations: Ancient Egypt, Mesopotamia, Persia, India, China, Ancient Greece, Rome, as well as Inca, Maya, and Olmec. Each of these centers of early civilization developed a unique and characteristic style in its art. Because of the size and duration of these civilizations, more of their art works have survived and more of their influence has been transmitted to other cultures and later times. Some also have provided the first records of how artists worked. For example, this period of Greek art saw a veneration of the human physical form and the development of equivalent skills to show musculature, poise, beauty, and anatomically correct proportions. In Byzantine and Medieval art of the Western Middle Ages, much art focused on the expression of subjects about Biblical and religious culture, and used styles that showed the higher glory of a heavenly world, such as the use of gold in the background of paintings, or glass in mosaics or windows, which also presented figures in idealized, patterned (flat) forms. Nevertheless, a classical realist tradition persisted in small Byzantine works, and realism steadily grew in the art of Catholic Europe. Renaissance art had a greatly increased emphasis on the realistic depiction of the material world, and the place of humans in it, reflected in the corporeality of the human body, and development of a systematic method of graphical perspective to depict recession in a three-dimensional picture space. In the east, Islamic art's rejection of iconography led to emphasis on geometric patterns, calligraphy, and architecture. Further east, religion dominated artistic styles and forms too. India and Tibet saw emphasis on painted sculptures and dance, while religious painting borrowed many conventions from sculpture and tended to bright contrasting colors with emphasis on outlines. China saw the flourishing of many art forms: jade carving, bronzework, pottery (including the stunning terracotta army of Emperor Qin), poetry, calligraphy, music, painting, drama, fiction, etc. Chinese styles vary greatly from era to era and each one is traditionally named after the ruling dynasty. So, for example, Tang dynasty paintings are monochromatic and sparse, emphasizing idealized landscapes, but Ming dynasty paintings are busy and colorful, and focus on telling stories via setting and composition. Japan names its styles after imperial dynasties too, and also saw much interplay between the styles of calligraphy and painting. Woodblock printing became important in Japan after the 17th century. The western Age of Enlightenment in the 18th century saw artistic depictions of physical and rational certainties of the clockwork universe, as well as politically revolutionary visions of a post-monarchist world, such as Blake's portrayal of Newton as a divine geometer, or David's propagandistic paintings. This led to Romantic rejections of this in favor of pictures of the emotional side and individuality of humans, exemplified in the novels of Goethe. The late 19th century then saw a host of artistic movements, such as academic art, Symbolism, impressionism and fauvism among others. The history of 20th-century art is a narrative of endless possibilities and the search for new standards, each being torn down in succession by the next. Thus the parameters of Impressionism, Expressionism, Fauvism, Cubism, Dadaism, Surrealism, etc. cannot be maintained very much beyond the time of their invention. Increasing global interaction during this time saw an equivalent influence of other cultures into Western art. Thus, Japanese woodblock prints (themselves influenced by Western Renaissance draftsmanship) had an immense influence on impressionism and subsequent development. Later, African sculptures were taken up by Picasso and to some extent by Matisse. Similarly, in the 19th and 20th centuries the West has had huge impacts on Eastern art with originally western ideas like Communism and Post-Modernism exerting a powerful influence. Modernism, the idealistic search for truth, gave way in the latter half of the 20th century to a realization of its unattainability. Theodor W. Adorno said in 1970, "It is now taken for granted that nothing which concerns art can be taken for granted any more: neither art itself, nor art in relationship to the whole, nor even the right of art to exist." Relativism was accepted as an unavoidable truth, which led to the period of contemporary art and postmodern criticism, where cultures of the world and of history are seen as changing forms, which can be appreciated and drawn from only with skepticism and irony. Furthermore, the separation of cultures is increasingly blurred and some argue it is now more appropriate to think in terms of a global culture, rather than of regional ones. In The Origin of the Work of Art, Martin Heidegger, a German philosopher and a seminal thinker, describes the essence of art in terms of the concepts of being and truth. He argues that art is not only a way of expressing the element of truth in a culture, but the means of creating it and providing a springboard from which "that which is" can be revealed. Works of art are not merely representations of the way things are, but actually produce a community's shared understanding. Each time a new artwork is added to any culture, the meaning of what it is to exist is inherently changed. Historically, art and artistic skills and ideas have often been spread through trade. An example of this is the Silk Road, where Hellenistic, Iranian, Indian and Chinese influences could mix. Greco Buddhist art is one of the most vivid examples of this interaction. The meeting of different cultures and worldviews also influenced artistic creation. An example of this is the multicultural port metropolis of Trieste at the beginning of the 20th century, where James Joyce met writers from Central Europe and the artistic development of New York City as a cultural melting pot. Forms, genres, media, and styles The creative arts are often divided into more specific categories, typically along perceptually distinguishable categories such as media, genre, styles, and form. Art form refers to the elements of art that are independent of its interpretation or significance. It covers the methods adopted by the artist and the physical composition of the artwork, primarily non-semantic aspects of the work (i.e., figurae), such as color, contour, dimension, medium, melody, space, texture, and value. Form may also include visual design principles, such as arrangement, balance, contrast, emphasis, harmony, proportion, proximity, and rhythm. In general there are three schools of philosophy regarding art, focusing respectively on form, content, and context. Extreme Formalism is the view that all aesthetic properties of art are formal (that is, part of the art form). Philosophers almost universally reject this view and hold that the properties and aesthetics of art extend beyond materials, techniques, and form. Unfortunately, there is little consensus on terminology for these informal properties. Some authors refer to subject matter and content – i.e., denotations and connotations – while others prefer terms like meaning and significance. Extreme Intentionalism holds that authorial intent plays a decisive role in the meaning of a work of art, conveying the content or essential main idea, while all other interpretations can be discarded. It defines the subject as the persons or idea represented, and the content as the artist's experience of that subject. For example, the composition of Napoleon I on his Imperial Throne is partly borrowed from the Statue of Zeus at Olympia. As evidenced by the title, the subject is Napoleon, and the content is Ingres's representation of Napoleon as "Emperor-God beyond time and space". Similarly to extreme formalism, philosophers typically reject extreme intentionalism, because art may have multiple ambiguous meanings and authorial intent may be unknowable and thus irrelevant. Its restrictive interpretation is "socially unhealthy, philosophically unreal, and politically unwise". Finally, the developing theory of post-structuralism studies art's significance in a cultural context, such as the ideas, emotions, and reactions prompted by a work. The cultural context often reduces to the artist's techniques and intentions, in which case analysis proceeds along lines similar to formalism and intentionalism. However, in other cases historical and material conditions may predominate, such as religious and philosophical convictions, sociopolitical and economic structures, or even climate and geography. Art criticism continues to grow and develop alongside art. Skill and craft Art can connote a sense of trained ability or mastery of a medium. Art can also simply refer to the developed and efficient use of a language to convey meaning with immediacy or depth. Art can be defined as an act of expressing feelings, thoughts, and observations. There is an understanding that is reached with the material as a result of handling it, which facilitates one's thought processes. A common view is that the epithet "art", particular in its elevated sense, requires a certain level of creative expertise by the artist, whether this be a demonstration of technical ability, an originality in stylistic approach, or a combination of these two. Traditionally skill of execution was viewed as a quality inseparable from art and thus necessary for its success; for Leonardo da Vinci, art, neither more nor less than his other endeavors, was a manifestation of skill. Rembrandt's work, now praised for its ephemeral virtues, was most admired by his contemporaries for its virtuosity. At the turn of the 20th century, the adroit performances of John Singer Sargent were alternately admired and viewed with skepticism for their manual fluency, yet at nearly the same time the artist who would become the era's most recognized and peripatetic iconoclast, Pablo Picasso, was completing a traditional academic training at which he excelled. A common contemporary criticism of some modern art occurs along the lines of objecting to the apparent lack of skill or ability required in the production of the artistic object. In conceptual art, Marcel Duchamp's "Fountain" is among the first examples of pieces wherein the artist used found objects ("ready-made") and exercised no traditionally recognised set of skills. Tracey Emin's My Bed, or Damien Hirst's The Physical Impossibility of Death in the Mind of Someone Living follow this example and also manipulate the mass media. Emin slept (and engaged in other activities) in her bed before placing the result in a gallery as work of art. Hirst came up with the conceptual design for the artwork but has left most of the eventual creation of many works to employed artisans. Hirst's celebrity is founded entirely on his ability to produce shocking concepts. The actual production in many conceptual and contemporary works of art is a matter of assembly of found objects. However, there are many modernist and contemporary artists who continue to excel in the skills of drawing and painting and in creating hands-on works of art. Purpose Art has had a great number of different functions throughout its history, making its purpose difficult to abstract or quantify to any single concept. This does not imply that the purpose of Art is "vague", but that it has had many unique, different reasons for being created. Some of these functions of Art are provided in the following outline. The different purposes of art may be grouped according to those that are non-motivated, and those that are motivated (Lévi-Strauss). Non-motivated functions The non-motivated purposes of art are those that are integral to being human, transcend the individual, or do not fulfill a specific external purpose. In this sense, Art, as creativity, is something humans must do by their very nature (i.e., no other species creates art), and is therefore beyond utility. Basic human instinct for harmony, balance, rhythm. Art at this level is not an action or an object, but an internal appreciation of balance and harmony (beauty), and therefore an aspect of being human beyond utility.Imitation, then, is one instinct of our nature. Next, there is the instinct for 'harmony' and rhythm, meters being manifestly sections of rhythm. Persons, therefore, starting with this natural gift developed by degrees their special aptitudes, till their rude improvisations gave birth to Poetry. – Aristotle Experience of the mysterious. Art provides a way to experience one's self in relation to the universe. This experience may often come unmotivated, as one appreciates art, music or poetry.The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. – Albert Einstein Expression of the imagination. Art provides a means to express the imagination in non-grammatic ways that are not tied to the formality of spoken or written language. Unlike words, which come in sequences and each of which have a definite meaning, art provides a range of forms, symbols and ideas with meanings that are malleable.Jupiter's eagle [as an example of art] is not, like logical (aesthetic) attributes of an object, the concept of the sublimity and majesty of creation, but rather something else—something that gives the imagination an incentive to spread its flight over a whole host of kindred representations that provoke more thought than admits of expression in a concept determined by words. They furnish an aesthetic idea, which serves the above rational idea as a substitute for logical presentation, but with the proper function, however, of animating the mind by opening out for it a prospect into a field of kindred representations stretching beyond its ken. – Immanuel Kant Ritualistic and symbolic functions. In many cultures, art is used in rituals, performances and dances as a decoration or symbol. While these often have no specific utilitarian (motivated) purpose, anthropologists know that they often serve a purpose at the level of meaning within a particular culture. This meaning is not furnished by any one individual, but is often the result of many generations of change, and of a cosmological relationship within the culture.Most scholars who deal with rock paintings or objects recovered from prehistoric contexts that cannot be explained in utilitarian terms and are thus categorized as decorative, ritual or symbolic, are aware of the trap posed by the term 'art'. – Silva Tomaskova Motivated functions Motivated purposes of art refer to intentional, conscious actions on the part of the artists or creator. These may be to bring about political change, to comment on an aspect of society, to convey a specific emotion or mood, to address personal psychology, to illustrate another discipline, to (with commercial arts) sell a product, or simply as a form of communication. Communication. Art, at its simplest, is a form of communication. As most forms of communication have an intent or goal directed toward another individual, this is a motivated purpose. Illustrative arts, such as scientific illustration, are a form of art as communication. Maps are another example. However, the content need not be scientific. Emotions, moods and feelings are also communicated through art.[Art is a set of] artefacts or images with symbolic meanings as a means of communication. – Steve Mithen Art as entertainment. Art may seek to bring about a particular emotion or mood, for the purpose of relaxing or entertaining the viewer. This is often the function of the art industries of Motion Pictures and Video Games. The Avant-Garde. Art for political change. One of the defining functions of early 20th-century art has been to use visual images to bring about political change. Art movements that had this goal—Dadaism, Surrealism, Russian constructivism, and Abstract Expressionism, among others—are collectively referred to as the avant-garde arts.By contrast, the realistic attitude, inspired by positivism, from Saint Thomas Aquinas to Anatole France, clearly seems to me to be hostile to any intellectual or moral advancement. I loathe it, for it is made up of mediocrity, hate, and dull conceit. It is this attitude which today gives birth to these ridiculous books, these insulting plays. It constantly feeds on and derives strength from the newspapers and stultifies both science and art by assiduously flattering the lowest of tastes; clarity bordering on stupidity, a dog's life. – André Breton (Surrealism) Art as a "free zone", removed from the action of the social censure. Unlike the avant-garde movements, which wanted to erase cultural differences in order to produce new universal values, contemporary art has enhanced its tolerance towards cultural differences as well as its critical and liberating functions (social inquiry, activism, subversion, deconstruction ...), becoming a more open place for research and experimentation. Art for social inquiry, subversion or anarchy. While similar to art for political change, subversive or deconstructivist art may seek to question aspects of society without any specific political goal. In this case, the function of art may be simply to criticize some aspect of society. Graffiti art and other types of street art are graphics and images that are spray-painted or stencilled on publicly viewable walls, buildings, buses, trains, and bridges, usually without permission. Certain art forms, such as graffiti, may also be illegal when they break laws (in this case vandalism). Art for social causes. Art can be used to raise awareness for a large variety of causes. A number of art activities were aimed at raising awareness of autism, cancer, human trafficking, and a variety of other topics, such as ocean conservation, human rights in Darfur, murdered and missing Aboriginal women, elder abuse, and pollution. Trashion, using trash to make fashion, practiced by artists such as Marina DeBris is one example of using art to raise awareness about pollution. Art for psychological and healing purposes. Art is also used by art therapists, psychotherapists and clinical psychologists as art therapy. The Diagnostic Drawing Series, for example, is used to determine the personality and emotional functioning of a patient. The end product is not the principal goal in this case, but rather a process of healing, through creative acts, is sought. The resultant piece of artwork may also offer insight into the troubles experienced by the subject and may suggest suitable approaches to be used in more conventional forms of psychiatric therapy. Art for propaganda, or commercialism. Art is often utilized as a form of propaganda, and thus can be used to subtly influence popular conceptions or mood. In a similar way, art that tries to sell a product also influences mood and emotion. In both cases, the purpose of art here is to subtly manipulate the viewer into a particular emotional or psychological response toward a particular idea or object. Art as a fitness indicator. It has been argued that the ability of the human brain by far exceeds what was needed for survival in the ancestral environment. One evolutionary psychology explanation for this is that the human brain and associated traits (such as artistic ability and creativity) are the human equivalent of the peacock's tail. The purpose of the male peacock's extravagant tail has been argued to be to attract females (see also Fisherian runaway and handicap principle). According to this theory superior execution of art was evolutionarily important because it attracted mates. The functions of art described above are not mutually exclusive, as many of them may overlap. For example, art for the purpose of entertainment may also seek to sell a product, i.e. the movie or video game. Public access Since ancient times, much of the finest art has represented a deliberate display of wealth or power, often achieved by using massive scale and expensive materials. Much art has been commissioned by political rulers or religious establishments, with more modest versions only available to the most wealthy in society. Nevertheless, there have been many periods where art of very high quality was available, in terms of ownership, across large parts of society, above all in cheap media such as pottery, which persists in the ground, and perishable media such as textiles and wood. In many different cultures, the ceramics of indigenous peoples of the Americas are found in such a wide range of graves that they were clearly not restricted to a social elite, though other forms of art may have been. Reproductive methods such as moulds made mass-production easier, and were used to bring high-quality Ancient Roman pottery and Greek Tanagra figurines to a very wide market. Cylinder seals were both artistic and practical, and very widely used by what can be loosely called the middle class in the Ancient Near East. Once coins were widely used, these also became an art form that reached the widest range of society. Another important innovation came in the 15th century in Europe, when printmaking began with small woodcuts, mostly religious, that were often very small and hand-colored, and affordable even by peasants who glued them to the walls of their homes. Printed books were initially very expensive, but fell steadily in price until by the 19th century even the poorest could afford some with printed illustrations. Popular prints of many different sorts have decorated homes and other places for centuries. In 1661, the city of Basel, in Switzerland, opened the first public museum of art in the world, the Kunstmuseum Basel. Today, its collection is distinguished by an impressively wide historic span, from the early 15th century up to the immediate present. Its various areas of emphasis give it international standing as one of the most significant museums of its kind. These encompass: paintings and drawings by artists active in the Upper Rhine region between 1400 and 1600, and on the art of the 19th to 21st centuries. Public buildings and monuments, secular and religious, by their nature normally address the whole of society, and visitors as viewers, and display to the general public has long been an important factor in their design. Egyptian temples are typical in that the most largest and most lavish decoration was placed on the parts that could be seen by the general public, rather than the areas seen only by the priests. Many areas of royal palaces, castles and the houses of the social elite were often generally accessible, and large parts of the art collections of such people could often be seen, either by anybody, or by those able to pay a small price, or those wearing the correct clothes, regardless of who they were, as at the Palace of Versailles, where the appropriate extra accessories (silver shoe buckles and a sword) could be hired from shops outside. Special arrangements were made to allow the public to see many royal or private collections placed in galleries, as with the Orleans Collection mostly housed in a wing of the Palais Royal in Paris, which could be visited for most of the 18th century. In Italy the art tourism of the Grand Tour became a major industry from the Renaissance onwards, and governments and cities made efforts to make their key works accessible. The British Royal Collection remains distinct, but large donations such as the Old Royal Library were made from it to the British Museum, established in 1753. The Uffizi in Florence opened entirely as a gallery in 1765, though this function had been gradually taking the building over from the original civil servants' offices for a long time before. The building now occupied by the Prado in Madrid was built before the French Revolution for the public display of parts of the royal art collection, and similar royal galleries open to the public existed in Vienna, Munich and other capitals. The opening of the Musée du Louvre during the French Revolution (in 1793) as a public museum for much of the former French royal collection certainly marked an important stage in the development of public access to art, transferring ownership to a republican state, but was a continuation of trends already well established. Most modern public museums and art education programs for children in schools can be traced back to this impulse to have art available to everyone. However, museums do not only provide availability to art, but do also influence the way art is being perceived by the audience, as studies found. Thus, the museum itself is not only a blunt stage for the presentation of art, but plays an active and vital role in the overall perception of art in modern society. Museums in the United States tend to be gifts from the very rich to the masses. (The Metropolitan Museum of Art in New York City, for example, was created by John Taylor Johnston, a railroad executive whose personal art collection seeded the museum.) But despite all this, at least one of the important functions of art in the 21st century remains as a marker of wealth and social status. There have been attempts by artists to create art that can not be bought by the wealthy as a status object. One of the prime original motivators of much of the art of the late 1960s and 1970s was to create art that could not be bought and sold. It is "necessary to present something more than mere objects" said the major post war German artist Joseph Beuys. This time period saw the rise of such things as performance art, video art, and conceptual art. The idea was that if the artwork was a performance that would leave nothing behind, or was simply an idea, it could not be bought and sold. "Democratic precepts revolving around the idea that a work of art is a commodity impelled the aesthetic innovation which germinated in the mid-1960s and was reaped throughout the 1970s. Artists broadly identified under the heading of Conceptual art ... substituting performance and publishing activities for engagement with both the material and materialistic concerns of painted or sculptural form ... [have] endeavored to undermine the art object qua object." In the decades since, these ideas have been somewhat lost as the art market has learned to sell limited edition DVDs of video works, invitations to exclusive performance art pieces, and the objects left over from conceptual pieces. Many of these performances create works that are only understood by the elite who have been educated as to why an idea or video or piece of apparent garbage may be considered art. The marker of status becomes understanding the work instead of necessarily owning it, and the artwork remains an upper-class activity. "With the widespread use of DVD recording technology in the early 2000s, artists, and the gallery system that derives its profits from the sale of artworks, gained an important means of controlling the sale of video and computer artworks in limited editions to collectors." Controversies Art has long been controversial, that is to say disliked by some viewers, for a wide variety of reasons, though most pre-modern controversies are dimly recorded, or completely lost to a modern view. Iconoclasm is the destruction of art that is disliked for a variety of reasons, including religious ones. Aniconism is a general dislike of either all figurative images, or often just religious ones, and has been a thread in many major religions. It has been a crucial factor in the history of Islamic art, where depictions of Muhammad remain especially controversial. Much art has been disliked purely because it depicted or otherwise stood for unpopular rulers, parties or other groups. Artistic conventions have often been conservative and taken very seriously by art critics, though often much less so by a wider public. The iconographic content of art could cause controversy, as with late medieval depictions of the new motif of the Swoon of the Virgin in scenes of the Crucifixion of Jesus. The Last Judgment by Michelangelo was controversial for various reasons, including breaches of decorum through nudity and the Apollo-like pose of Christ. The content of much formal art through history was dictated by the patron or commissioner rather than just the artist, but with the advent of Romanticism, and economic changes in the production of art, the artists' vision became the usual determinant of the content of his art, increasing the incidence of controversies, though often reducing their significance. Strong incentives for perceived originality and publicity also encouraged artists to court controversy. Théodore Géricault's Raft of the Medusa (c. 1820), was in part a political commentary on a recent event. Édouard Manet's Le Déjeuner sur l'Herbe (1863), was considered scandalous not because of the nude woman, but because she is seated next to men fully dressed in the clothing of the time, rather than in robes of the antique world. John Singer Sargent's Madame Pierre Gautreau (Madam X) (1884), caused a controversy over the reddish pink used to color the woman's ear lobe, considered far too suggestive and supposedly ruining the high-society model's reputation. The gradual abandonment of naturalism and the depiction of realistic representations of the visual appearance of subjects in the 19th and 20th centuries led to a rolling controversy lasting for over a century. In the 20th century, Pablo Picasso's Guernica (1937) used arresting cubist techniques and stark monochromatic oils, to depict the harrowing consequences of a contemporary bombing of a small, ancient Basque town. Leon Golub's Interrogation III (1981), depicts a female nude, hooded detainee strapped to a chair, her legs open to reveal her sexual organs, surrounded by two tormentors dressed in everyday clothing. Andres Serrano's Piss Christ (1989) is a photograph of a crucifix, sacred to the Christian religion and representing Christ's sacrifice and final suffering, submerged in a glass of the artist's own urine. The resulting uproar led to comments in the United States Senate about public funding of the arts. Theory Before Modernism, aesthetics in Western art was greatly concerned with achieving the appropriate balance between different aspects of realism or truth to nature and the ideal; ideas as to what the appropriate balance is have shifted to and fro over the centuries. This concern is largely absent in other traditions of art. The aesthetic theorist John Ruskin, who championed what he saw as the naturalism of J. M. W. Turner, saw art's role as the communication by artifice of an essential truth that could only be found in nature. The definition and evaluation of art has become especially problematic since the 20th century. Richard Wollheim distinguishes three approaches to assessing the aesthetic value of art: the Realist, whereby aesthetic quality is an absolute value independent of any human view; the Objectivist, whereby it is also an absolute value, but is dependent on general human experience; and the Relativist position, whereby it is not an absolute value, but depends on, and varies with, the human experience of different humans. Arrival of Modernism The arrival of Modernism in the late 19th century lead to a radical break in the conception of the function of art, and then again in the late 20th century with the advent of postmodernism. Clement Greenberg's 1960 article "Modernist Painting" defines modern art as "the use of characteristic methods of a discipline to criticize the discipline itself". Greenberg originally applied this idea to the Abstract Expressionist movement and used it as a way to understand and justify flat (non-illusionistic) abstract painting: After Greenberg, several important art theorists emerged, such as Michael Fried, T. J. Clark, Rosalind Krauss, Linda Nochlin and Griselda Pollock among others. Though only originally intended as a way of understanding a specific set of artists, Greenberg's definition of modern art is important to many of the ideas of art within the various art movements of the 20th century and early 21st century. Pop artists like Andy Warhol became both noteworthy and influential through work including and possibly critiquing popular culture, as well as the art world. Artists of the 1980s, 1990s, and 2000s expanded this technique of self-criticism beyond high art to all cultural image-making, including fashion images, comics, billboards and pornography. Duchamp once proposed that art is any activity of any kind-everything. However, the way that only certain activities are classified today as art is a social construction. There is evidence that there may be an element of truth to this. In The Invention of Art: A Cultural History, Larry Shiner examines the construction of the modern system of the arts, i.e. fine art. He finds evidence that the older system of the arts before our modern system (fine art) held art to be any skilled human activity; for example, Ancient Greek society did not possess the term art, but techne. Techne can be understood neither as art or craft, the reason being that the distinctions of art and craft are historical products that came later on in human history. Techne included painting, sculpting and music, but also cooking, medicine, horsemanship, geometry, carpentry, prophecy, and farming, etc. New Criticism and the "intentional fallacy" Following Duchamp during the first half of the 20th century, a significant shift to general aesthetic theory took place which attempted to apply aesthetic theory between various forms of art, including the literary arts and the visual arts, to each other. This resulted in the rise of the New Criticism school and debate concerning the intentional fallacy. At issue was the question of whether the aesthetic intentions of the artist in creating the work of art, whatever its specific form, should be associated with the criticism and evaluation of the final product of the work of art, or, if the work of art should be evaluated on its own merits independent of the intentions of the artist. In 1946, William K. Wimsatt and Monroe Beardsley published a classic and controversial New Critical essay entitled "The Intentional Fallacy", in which they argued strongly against the relevance of an author's intention, or "intended meaning" in the analysis of a literary work. For Wimsatt and Beardsley, the words on the page were all that mattered; importation of meanings from outside the text was considered irrelevant, and potentially distracting. In another essay, "The Affective Fallacy", which served as a kind of sister essay to "The Intentional Fallacy" Wimsatt and Beardsley also discounted the reader's personal/emotional reaction to a literary work as a valid means of analyzing a text. This fallacy would later be repudiated by theorists from the reader-response school of literary theory. Ironically, one of the leading theorists from this school, Stanley Fish, was himself trained by New Critics. Fish criticizes Wimsatt and Beardsley in his 1970 essay "Literature in the Reader". As summarized by Gaut and Livingston in their essay "The Creation of Art": "Structuralist and post-structuralists theorists and critics were sharply critical of many aspects of New Criticism, beginning with the emphasis on aesthetic appreciation and the so-called autonomy of art, but they reiterated the attack on biographical criticisms' assumption that the artist's activities and experience were a privileged critical topic." These authors contend that: "Anti-intentionalists, such as formalists, hold that the intentions involved in the making of art are irrelevant or peripheral to correctly interpreting art. So details of the act of creating a work, though possibly of interest in themselves, have no bearing on the correct interpretation of the work." Gaut and Livingston define the intentionalists as distinct from formalists stating that: "Intentionalists, unlike formalists, hold that reference to intentions is essential in fixing the correct interpretation of works." They quote Richard Wollheim as stating that, "The task of criticism is the reconstruction of the creative process, where the creative process must in turn be thought of as something not stopping short of, but terminating on, the work of art itself." "Linguistic turn" and its debate The end of the 20th century fostered an extensive debate known as the linguistic turn controversy, or the "innocent eye debate" in the philosophy of art. This debate discussed the encounter of the work of art as being determined by the relative extent to which the conceptual encounter with the work of art dominates over the perceptual encounter with the work of art. Decisive for the linguistic turn debate in art history and the humanities were the works of yet another tradition, namely the structuralism of Ferdinand de Saussure and the ensuing movement of poststructuralism. In 1981, the artist Mark Tansey created a work of art titled "The Innocent Eye" as a criticism of the prevailing climate of disagreement in the philosophy of art during the closing decades of the 20th century. Influential theorists include Judith Butler, Luce Irigaray, Julia Kristeva, Michel Foucault and Jacques Derrida. The power of language, more specifically of certain rhetorical tropes, in art history and historical discourse was explored by Hayden White. The fact that language is not a transparent medium of thought had been stressed by a very different form of philosophy of language which originated in the works of Johann Georg Hamann and Wilhelm von Humboldt. Ernst Gombrich and Nelson Goodman in his book Languages of Art: An Approach to a Theory of Symbols came to hold that the conceptual encounter with the work of art predominated exclusively over the perceptual and visual encounter with the work of art during the 1960s and 1970s. He was challenged on the basis of research done by the Nobel prize winning psychologist Roger Sperry who maintained that the human visual encounter was not limited to concepts represented in language alone (the linguistic turn) and that other forms of psychological representations of the work of art were equally defensible and demonstrable. Sperry's view eventually prevailed by the end of the 20th century with aesthetic philosophers such as Nick Zangwill strongly defending a return to moderate aesthetic formalism among other alternatives. Classification disputes Disputes as to whether or not to classify something as a work of art are referred to as classificatory disputes about art. Classificatory disputes in the 20th century have included cubist and impressionist paintings, Duchamp's Fountain, the movies, superlative imitations of banknotes, conceptual art, and video games. Philosopher David Novitz has argued that disagreement about the definition of art are rarely the heart of the problem. Rather, "the passionate concerns and interests that humans vest in their social life" are "so much a part of all classificatory disputes about art." According to Novitz, classificatory disputes are more often disputes about societal values and where society is trying to go than they are about theory proper. For example, when the Daily Mail criticized Hirst's and Emin's work by arguing "For 1,000 years art has been one of our great civilising forces. Today, pickled sheep and soiled beds threaten to make barbarians of us all" they are not advancing a definition or theory about art, but questioning the value of Hirst's and Emin's work. In 1998, Arthur Danto, suggested a thought experiment showing that "the status of an artifact as work of art results from the ideas a culture applies to it, rather than its inherent physical or perceptible qualities. Cultural interpretation (an art theory of some kind) is therefore constitutive of an object's arthood." Anti-art is a label for art that intentionally challenges the established parameters and values of art; it is term associated with Dadaism and attributed to Marcel Duchamp just before World War I, when he was making art from found objects. One of these, Fountain (1917), an ordinary urinal, has achieved considerable prominence and influence on art. Anti-art is a feature of work by Situationist International, the lo-fi Mail art movement, and the Young British Artists, though it is a form still rejected by the Stuckists, who describe themselves as anti-anti-art. Architecture is often included as one of the visual arts; however, like the decorative arts, or advertising, it involves the creation of objects where the practical considerations of use are essential in a way that they usually are not in a painting, for example. Value judgment Somewhat in relation to the above, the word art is also used to apply judgments of value, as in such expressions as "that meal was a work of art" (the cook is an artist), or "the art of deception" (the highly attained level of skill of the deceiver is praised). It is this use of the word as a measure of high quality and high value that gives the term its flavor of subjectivity. Making judgments of value requires a basis for criticism. At the simplest level, a way to determine whether the impact of the object on the senses meets the criteria to be considered art is whether it is perceived to be attractive or repulsive. Though perception is always colored by experience, and is necessarily subjective, it is commonly understood that what is not somehow aesthetically satisfying cannot be art. However, "good" art is not always or even regularly aesthetically appealing to a majority of viewers. In other words, an artist's prime motivation need not be the pursuit of the aesthetic. Also, art often depicts terrible images made for social, moral, or thought-provoking reasons. For example, Francisco Goya's painting depicting the Spanish shootings of 3 May 1808 is a graphic depiction of a firing squad executing several pleading civilians. Yet at the same time, the horrific imagery demonstrates Goya's keen artistic ability in composition and execution and produces fitting social and political outrage. Thus, the debate continues as to what mode of aesthetic satisfaction, if any, is required to define 'art'. The assumption of new values or the rebellion against accepted notions of what is aesthetically superior need not occur concurrently with a complete abandonment of the pursuit of what is aesthetically appealing. Indeed, the reverse is often true, that the revision of what is popularly conceived of as being aesthetically appealing allows for a re-invigoration of aesthetic sensibility, and a new appreciation for the standards of art itself. Countless schools have proposed their own ways to define quality, yet they all seem to agree in at least one point: once their aesthetic choices are accepted, the value of the work of art is determined by its capacity to transcend the limits of its chosen medium to strike some universal chord by the rarity of the skill of the artist or in its accurate reflection in what is termed the zeitgeist. Art is often intended to appeal to and connect with human emotion. It can arouse aesthetic or moral feelings, and can be understood as a way of communicating these feelings. Artists express something so that their audience is aroused to some extent, but they do not have to do so consciously. Art may be considered an exploration of the human condition; that is, what it is to be human. By extension, it has been argued by Emily L. Spratt that the development of artificial intelligence, especially in regard to its uses with images, necessitates a re-evaluation of aesthetic theory in art history today and a reconsideration of the limits of human creativity. Art and law An essential legal issue are art forgeries, plagiarism, replicas and works that are strongly based on other works of art. The trade in works of art or the export from a country may be subject to legal regulations. Internationally there are also extensive efforts to protect the works of art created. The UN, UNESCO and Blue Shield International try to ensure effective protection at the national level and to intervene directly in the event of armed conflicts or disasters. This can particularly affect museums, archives, art collections and excavation sites. This should also secure the economic basis of a country, especially because works of art are often of tourist importance. The founding president of Blue Shield International, Karl von Habsburg, explained an additional connection between the destruction of cultural property and the cause of flight during a mission in Lebanon in April 2019: “Cultural goods are part of the identity of the people who live in a certain place. If you destroy their culture, you also destroy their identity. Many people are uprooted, often no longer have any prospects and as a result flee from their homeland.” See also Applied arts Art movement Artist in residence Artistic freedom Cultural tourism Craftivism Formal analysis History of art List of artistic media List of art techniques Mathematics and art Street art (or "independent public art") Outline of the visual arts, a guide to the subject of art presented as a tree structured list of its subtopics. Visual impairment in art Notes Bibliography Oscar Wilde, Intentions, 1891 Stephen Davies, Definitions of Art, 1991 Nina Felshin, ed. But is it Art?, 1995 Catherine de Zegher (ed.). Inside the Visible. MIT Press, 1996 Evelyn Hatcher, ed. Art as Culture: An Introduction to the Anthropology of Art, 1999 Noel Carroll, Theories of Art Today, 2000 John Whitehead. Grasping for the Wind, 2001 Michael Ann Holly and Keith Moxey (eds.) Art History Aesthetics Visual Studies. New Haven: Yale University Press, 2002. Shiner, Larry. The Invention of Art: A Cultural History. Chicago: University of Chicago Press, 2003. Arthur Danto, The Abuse of Beauty: Aesthetics and the Concept of Art. 2003 Dana Arnold and Margaret Iverson, eds. Art and Thought. London: Blackwell, 2003. Jean Robertson and Craig McDaniel, Themes of Contemporary Art, Visual Art after 1980, 2005 Further reading Antony Briant and Griselda Pollock, eds. Digital and Other Virtualities: Renegotiating the image. London and NY: I.B.Tauris, 2010. Augros, Robert M., Stanciu, George N. The New Story of Science: mind and the universe, Lake Bluff, Ill.: Regnery Gateway, 1984. (this book has significant material on art and science) Benedetto Croce. Aesthetic as Science of Expression and General Linguistic, 2002 Botar, Oliver A.I. Technical Detours: The Early Moholy-Nagy Reconsidered. Art Gallery of The Graduate Center, The City University of New York and The Salgo Trust for Education, 2006. Burguete, Maria, and Lam, Lui, eds. (2011). Arts: A Science Matter. World Scientific: Singapore. Carol Armstrong and Catherine de Zegher, eds. Women Artists at the Millennium. Massachusetts: October Books/The MIT Press, 2006. Carl Jung, Man and His Symbols. London: Pan Books, 1978. E.H. Gombrich, The Story of Art. London: Phaidon Press, 1995. Florian Dombois, Ute Meta Bauer, Claudia Mareis and Michael Schwab, eds. Intellectual Birdhouse. Artistic Practice as Research. London: Koening Books, 2012. Katharine Everett Gilbert and Helmut Kuhn, A History of Esthetics. Edition 2, revised. Indiana: Indiana University Press, 1953. Kristine Stiles and Peter Selz, eds. Theories and Documents of Contemporary Art. Berkeley: University of California Press, 1986 Kleiner, Gardner, Mamiya and Tansey. Art Through the Ages, Twelfth Edition (2 volumes) Wadsworth, 2004. (vol 1) and (vol 2) Richard Wollheim, Art and its Objects: An introduction to aesthetics. New York: Harper & Row, 1968. Will Gompertz. What Are You Looking At?: 150 Years of Modern Art in the Blink of an Eye. New York: Viking, 2012. Władysław Tatarkiewicz, A History of Six Ideas: an Essay in Aesthetics, translated from the Polish by Christopher Kasparek, The Hague, Martinus Nijhoff, 1980 External links Art and Play from the Dictionary of the History of ideas In-depth directory of art Art and Artist Files in the Smithsonian Libraries Collection (2005) Smithsonian Digital Libraries Visual Arts Data Service (VADS) – online collections from UK museums, galleries, universities RevolutionArt – Art magazines with worldwide exhibitions, callings and competitions Aesthetics Visual arts

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

775

https://en.wikipedia.org/wiki/Algorithm

Algorithm

In mathematics and computer science, an algorithm () is a finite sequence of well-defined instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. By making use of artificial intelligence, algorithms can perform automated deductions (referred to as automated reasoning) and use mathematical and logical tests to divert the code through various routes (referred to as automated decision-making). Using human characteristics as descriptors of machines in metaphorical ways was already practiced by Alan Turing with terms such as "memory", "search" and "stimulus". In contrast, a heuristic is an approach to problem solving that may not be fully specified or may not guarantee correct or optimal results, especially in problem domains where there is no well-defined correct or optimal result. As an effective method, an algorithm can be expressed within a finite amount of space and time, and in a well-defined formal language for calculating a function. Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well-defined successive states, eventually producing "output" and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input. History The concept of algorithm has existed since antiquity. Arithmetic algorithms, such as a division algorithm, were used by ancient Babylonian mathematicians c. 2500 BC and Egyptian mathematicians c. 1550 BC. Greek mathematicians later used algorithms in 240 BC in the sieve of Eratosthenes for finding prime numbers, and the Euclidean algorithm for finding the greatest common divisor of two numbers. Arabic mathematicians such as al-Kindi in the 9th century used cryptographic algorithms for code-breaking, based on frequency analysis. The word algorithm is derived from the name of the 9th-century Persian mathematician Muḥammad ibn Mūsā al-Khwārizmī, whose nisba (identifying him as from Khwarazm) was Latinized as Algoritmi (Arabized Persian الخوارزمی c. 780–850). Muḥammad ibn Mūsā al-Khwārizmī was a mathematician, astronomer, geographer, and scholar in the House of Wisdom in Baghdad, whose name means 'the native of Khwarazm', a region that was part of Greater Iran and is now in Uzbekistan. About 825, al-Khwarizmi wrote an Arabic language treatise on the Hindu–Arabic numeral system, which was translated into Latin during the 12th century. The manuscript starts with the phrase Dixit Algorizmi ('Thus spake Al-Khwarizmi'), where "Algorizmi" was the translator's Latinization of Al-Khwarizmi's name. Al-Khwarizmi was the most widely read mathematician in Europe in the late Middle Ages, primarily through another of his books, the Algebra. In late medieval Latin, algorismus, English 'algorism', the corruption of his name, simply meant the "decimal number system". In the 15th century, under the influence of the Greek word ἀριθμός (arithmos), 'number' (cf. 'arithmetic'), the Latin word was altered to algorithmus, and the corresponding English term 'algorithm' is first attested in the 17th century; the modern sense was introduced in the 19th century. Indian mathematics was predominantly algorithmic. Algorithms that are representative of the Indian mathematical tradition range from the ancient Śulbasūtrās to the medieval texts of the Kerala School. In English, the word algorithm was first used in about 1230 and then by Chaucer in 1391. English adopted the French term, but it was not until the late 19th century that "algorithm" took on the meaning that it has in modern English. Another early use of the word is from 1240, in a manual titled Carmen de Algorismo composed by Alexandre de Villedieu. It begins with: which translates to: The poem is a few hundred lines long and summarizes the art of calculating with the new styled Indian dice (Tali Indorum), or Hindu numerals. A partial formalization of the modern concept of algorithm began with attempts to solve the Entscheidungsproblem (decision problem) posed by David Hilbert in 1928. Later formalizations were framed as attempts to define "effective calculability" or "effective method". Those formalizations included the Gödel–Herbrand–Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's Formulation 1 of 1936, and Alan Turing's Turing machines of 1936–37 and 1939. Informal definition An informal definition could be "a set of rules that precisely defines a sequence of operations", which would include all computer programs (including programs that do not perform numeric calculations), and (for example) any prescribed bureaucratic procedure or cook-book recipe. In general, a program is only an algorithm if it stops eventually—even though infinite loops may sometimes prove desirable. A prototypical example of an algorithm is the Euclidean algorithm, which is used to determine the maximum common divisor of two integers; an example (there are others) is described by the flowchart above and as an example in a later section. offer an informal meaning of the word "algorithm" in the following quotation: No human being can write fast enough, or long enough, or small enough† ( †"smaller and smaller without limit ... you'd be trying to write on molecules, on atoms, on electrons") to list all members of an enumerably infinite set by writing out their names, one after another, in some notation. But humans can do something equally useful, in the case of certain enumerably infinite sets: They can give explicit instructions for determining the nth member of the set, for arbitrary finite n. Such instructions are to be given quite explicitly, in a form in which they could be followed by a computing machine, or by a human who is capable of carrying out only very elementary operations on symbols. An "enumerably infinite set" is one whose elements can be put into one-to-one correspondence with the integers. Thus Boolos and Jeffrey are saying that an algorithm implies instructions for a process that "creates" output integers from an arbitrary "input" integer or integers that, in theory, can be arbitrarily large. For example, an algorithm can be an algebraic equation such as y = m + n (i.e., two arbitrary "input variables" m and n that produce an output y), but various authors' attempts to define the notion indicate that the word implies much more than this, something on the order of (for the addition example): Precise instructions (in a language understood by "the computer") for a fast, efficient, "good" process that specifies the "moves" of "the computer" (machine or human, equipped with the necessary internally contained information and capabilities) to find, decode, and then process arbitrary input integers/symbols m and n, symbols + and = ... and "effectively" produce, in a "reasonable" time, output-integer y at a specified place and in a specified format. The concept of algorithm is also used to define the notion of decidability—a notion that is central for explaining how formal systems come into being starting from a small set of axioms and rules. In logic, the time that an algorithm requires to complete cannot be measured, as it is not apparently related to the customary physical dimension. From such uncertainties, that characterize ongoing work, stems the unavailability of a definition of algorithm that suits both concrete (in some sense) and abstract usage of the term. Most algorithms are intended to be implemented as computer programs. However, algorithms are also implemented by other means, such as in a biological neural network (for example, the human brain implementing arithmetic or an insect looking for food), in an electrical circuit, or in a mechanical device. Formalization Algorithms are essential to the way computers process data. Many computer programs contain algorithms that detail the specific instructions a computer should perform—in a specific order—to carry out a specified task, such as calculating employees' paychecks or printing students' report cards. Thus, an algorithm can be considered to be any sequence of operations that can be simulated by a Turing-complete system. Authors who assert this thesis include Minsky (1967), Savage (1987) and Gurevich (2000): Minsky: "But we will also maintain, with Turing ... that any procedure which could "naturally" be called effective, can, in fact, be realized by a (simple) machine. Although this may seem extreme, the arguments ... in its favor are hard to refute". Gurevich: "… Turing's informal argument in favor of his thesis justifies a stronger thesis: every algorithm can be simulated by a Turing machine … according to Savage [1987], an algorithm is a computational process defined by a Turing machine".Turing machines can define computational processes that do not terminate. The informal definitions of algorithms generally require that the algorithm always terminates. This requirement renders the task of deciding whether a formal procedure is an algorithm impossible in the general case—due to a major theorem of computability theory known as the halting problem. Typically, when an algorithm is associated with processing information, data can be read from an input source, written to an output device and stored for further processing. Stored data are regarded as part of the internal state of the entity performing the algorithm. In practice, the state is stored in one or more data structures. For some of these computational processes, the algorithm must be rigorously defined: specified in the way it applies in all possible circumstances that could arise. This means that any conditional steps must be systematically dealt with, case-by-case; the criteria for each case must be clear (and computable). Because an algorithm is a precise list of precise steps, the order of computation is always crucial to the functioning of the algorithm. Instructions are usually assumed to be listed explicitly, and are described as starting "from the top" and going "down to the bottom"—an idea that is described more formally by flow of control. So far, the discussion on the formalization of an algorithm has assumed the premises of imperative programming. This is the most common conception—one which attempts to describe a task in discrete, "mechanical" means. Unique to this conception of formalized algorithms is the assignment operation, which sets the value of a variable. It derives from the intuition of "memory" as a scratchpad. An example of such an assignment can be found below. For some alternate conceptions of what constitutes an algorithm, see functional programming and logic programming. Expressing algorithms Algorithms can be expressed in many kinds of notation, including natural languages, pseudocode, flowcharts, drakon-charts, programming languages or control tables (processed by interpreters). Natural language expressions of algorithms tend to be verbose and ambiguous, and are rarely used for complex or technical algorithms. Pseudocode, flowcharts, drakon-charts and control tables are structured ways to express algorithms that avoid many of the ambiguities common in the statements based on natural language. Programming languages are primarily intended for expressing algorithms in a form that can be executed by a computer, but are also often used as a way to define or document algorithms. There is a wide variety of representations possible and one can express a given Turing machine program as a sequence of machine tables (see finite-state machine, state transition table and control table for more), as flowcharts and drakon-charts (see state diagram for more), or as a form of rudimentary machine code or assembly code called "sets of quadruples" (see Turing machine for more). Representations of algorithms can be classed into three accepted levels of Turing machine description, as follows: 1 High-level description "...prose to describe an algorithm, ignoring the implementation details. At this level, we do not need to mention how the machine manages its tape or head." 2 Implementation description "...prose used to define the way the Turing machine uses its head and the way that it stores data on its tape. At this level, we do not give details of states or transition function." 3 Formal description Most detailed, "lowest level", gives the Turing machine's "state table". For an example of the simple algorithm "Add m+n" described in all three levels, see Examples. Design Algorithm design refers to a method or a mathematical process for problem-solving and engineering algorithms. The design of algorithms is part of many solution theories of operation research, such as dynamic programming and divide-and-conquer. Techniques for designing and implementing algorithm designs are also called algorithm design patterns, with examples including the template method pattern and the decorator pattern. One of the most important aspects of algorithm design is resource (run-time, memory usage) efficiency; the big O notation is used to describe e.g. an algorithm's run-time growth as the size of its input increases. Typical steps in the development of algorithms: Problem definition Development of a model Specification of the algorithm Designing an algorithm Checking the correctness of the algorithm Analysis of algorithm Implementation of algorithm Program testing Documentation preparation Computer algorithms "Elegant" (compact) programs, "good" (fast) programs : The notion of "simplicity and elegance" appears informally in Knuth and precisely in Chaitin: Knuth: " ... we want good algorithms in some loosely defined aesthetic sense. One criterion ... is the length of time taken to perform the algorithm .... Other criteria are adaptability of the algorithm to computers, its simplicity and elegance, etc." Chaitin: " ... a program is 'elegant,' by which I mean that it's the smallest possible program for producing the output that it does" Chaitin prefaces his definition with: "I'll show you can't prove that a program is 'elegant—such a proof would solve the Halting problem (ibid). Algorithm versus function computable by an algorithm: For a given function multiple algorithms may exist. This is true, even without expanding the available instruction set available to the programmer. Rogers observes that "It is ... important to distinguish between the notion of algorithm, i.e. procedure and the notion of function computable by algorithm, i.e. mapping yielded by procedure. The same function may have several different algorithms". Unfortunately, there may be a tradeoff between goodness (speed) and elegance (compactness)—an elegant program may take more steps to complete a computation than one less elegant. An example that uses Euclid's algorithm appears below. Computers (and computors), models of computation: A computer (or human "computor") is a restricted type of machine, a "discrete deterministic mechanical device" that blindly follows its instructions. Melzak's and Lambek's primitive models reduced this notion to four elements: (i) discrete, distinguishable locations, (ii) discrete, indistinguishable counters (iii) an agent, and (iv) a list of instructions that are effective relative to the capability of the agent. Minsky describes a more congenial variation of Lambek's "abacus" model in his "Very Simple Bases for Computability". Minsky's machine proceeds sequentially through its five (or six, depending on how one counts) instructions unless either a conditional IF-THEN GOTO or an unconditional GOTO changes program flow out of sequence. Besides HALT, Minsky's machine includes three assignment (replacement, substitution) operations: ZERO (e.g. the contents of location replaced by 0: L ← 0), SUCCESSOR (e.g. L ← L+1), and DECREMENT (e.g. L ← L − 1). Rarely must a programmer write "code" with such a limited instruction set. But Minsky shows (as do Melzak and Lambek) that his machine is Turing complete with only four general types of instructions: conditional GOTO, unconditional GOTO, assignment/replacement/substitution, and HALT. However, a few different assignment instructions (e.g. DECREMENT, INCREMENT, and ZERO/CLEAR/EMPTY for a Minsky machine) are also required for Turing-completeness; their exact specification is somewhat up to the designer. The unconditional GOTO is a convenience; it can be constructed by initializing a dedicated location to zero e.g. the instruction " Z ← 0 "; thereafter the instruction IF Z=0 THEN GOTO xxx is unconditional. Simulation of an algorithm: computer (computor) language: Knuth advises the reader that "the best way to learn an algorithm is to try it . . . immediately take pen and paper and work through an example". But what about a simulation or execution of the real thing? The programmer must translate the algorithm into a language that the simulator/computer/computor can effectively execute. Stone gives an example of this: when computing the roots of a quadratic equation the computor must know how to take a square root. If they don't, then the algorithm, to be effective, must provide a set of rules for extracting a square root. This means that the programmer must know a "language" that is effective relative to the target computing agent (computer/computor). But what model should be used for the simulation? Van Emde Boas observes "even if we base complexity theory on abstract instead of concrete machines, arbitrariness of the choice of a model remains. It is at this point that the notion of simulation enters". When speed is being measured, the instruction set matters. For example, the subprogram in Euclid's algorithm to compute the remainder would execute much faster if the programmer had a "modulus" instruction available rather than just subtraction (or worse: just Minsky's "decrement"). Structured programming, canonical structures: Per the Church–Turing thesis, any algorithm can be computed by a model known to be Turing complete, and per Minsky's demonstrations, Turing completeness requires only four instruction types—conditional GOTO, unconditional GOTO, assignment, HALT. Kemeny and Kurtz observe that, while "undisciplined" use of unconditional GOTOs and conditional IF-THEN GOTOs can result in "spaghetti code", a programmer can write structured programs using only these instructions; on the other hand "it is also possible, and not too hard, to write badly structured programs in a structured language". Tausworthe augments the three Böhm-Jacopini canonical structures: SEQUENCE, IF-THEN-ELSE, and WHILE-DO, with two more: DO-WHILE and CASE. An additional benefit of a structured program is that it lends itself to proofs of correctness using mathematical induction. Canonical flowchart symbols: The graphical aide called a flowchart, offers a way to describe and document an algorithm (and a computer program of one). Like the program flow of a Minsky machine, a flowchart always starts at the top of a page and proceeds down. Its primary symbols are only four: the directed arrow showing program flow, the rectangle (SEQUENCE, GOTO), the diamond (IF-THEN-ELSE), and the dot (OR-tie). The Böhm–Jacopini canonical structures are made of these primitive shapes. Sub-structures can "nest" in rectangles, but only if a single exit occurs from the superstructure. The symbols, and their use to build the canonical structures are shown in the diagram. Examples Algorithm example One of the simplest algorithms is to find the largest number in a list of numbers of random order. Finding the solution requires looking at every number in the list. From this follows a simple algorithm, which can be stated in a high-level description in English prose, as: High-level description: If there are no numbers in the set then there is no highest number. Assume the first number in the set is the largest number in the set. For each remaining number in the set: if this number is larger than the current largest number, consider this number to be the largest number in the set. When there are no numbers left in the set to iterate over, consider the current largest number to be the largest number of the set. (Quasi-)formal description: Written in prose but much closer to the high-level language of a computer program, the following is the more formal coding of the algorithm in pseudocode or pidgin code: Input: A list of numbers L. Output: The largest number in the list L. if L.size = 0 return null largest ← L[0] for each item in L, do if item > largest, then largest ← item return largest Euclid's algorithm In mathematics, the Euclidean algorithm, or Euclid's algorithm, is an efficient method for computing the greatest common divisor (GCD) of two integers (numbers), the largest number that divides them both without a remainder. It is named after the ancient Greek mathematician Euclid, who first described it in his Elements (c. 300 BC). It is one of the oldest algorithms in common use. It can be used to reduce fractions to their simplest form, and is a part of many other number-theoretic and cryptographic calculations. Euclid poses the problem thus: "Given two numbers not prime to one another, to find their greatest common measure". He defines "A number [to be] a multitude composed of units": a counting number, a positive integer not including zero. To "measure" is to place a shorter measuring length s successively (q times) along longer length l until the remaining portion r is less than the shorter length s. In modern words, remainder r = l − q×s, q being the quotient, or remainder r is the "modulus", the integer-fractional part left over after the division. For Euclid's method to succeed, the starting lengths must satisfy two requirements: (i) the lengths must not be zero, AND (ii) the subtraction must be "proper"; i.e., a test must guarantee that the smaller of the two numbers is subtracted from the larger (or the two can be equal so their subtraction yields zero). Euclid's original proof adds a third requirement: the two lengths must not be prime to one another. Euclid stipulated this so that he could construct a reductio ad absurdum proof that the two numbers' common measure is in fact the greatest. While Nicomachus' algorithm is the same as Euclid's, when the numbers are prime to one another, it yields the number "1" for their common measure. So, to be precise, the following is really Nicomachus' algorithm. Computer language for Euclid's algorithm Only a few instruction types are required to execute Euclid's algorithm—some logical tests (conditional GOTO), unconditional GOTO, assignment (replacement), and subtraction. A location is symbolized by upper case letter(s), e.g. S, A, etc. The varying quantity (number) in a location is written in lower case letter(s) and (usually) associated with the location's name. For example, location L at the start might contain the number l = 3009. An inelegant program for Euclid's algorithm The following algorithm is framed as Knuth's four-step version of Euclid's and Nicomachus', but, rather than using division to find the remainder, it uses successive subtractions of the shorter length s from the remaining length r until r is less than s. The high-level description, shown in boldface, is adapted from Knuth 1973:2–4: INPUT: [Into two locations L and S put the numbers l and s that represent the two lengths]: INPUT L, S [Initialize R: make the remaining length r equal to the starting/initial/input length l]: R ← L E0: [Ensure r ≥ s.] [Ensure the smaller of the two numbers is in S and the larger in R]: IF R > S THEN the contents of L is the larger number so skip over the exchange-steps 4, 5 and 6: GOTO step 7 ELSE swap the contents of R and S. L ← R (this first step is redundant, but is useful for later discussion). R ← S S ← L E1: [Find remainder]: Until the remaining length r in R is less than the shorter length s in S, repeatedly subtract the measuring number s in S from the remaining length r in R. IF S > R THEN done measuring so GOTO 10 ELSE measure again, R ← R − S [Remainder-loop]: GOTO 7. E2: [Is the remainder zero?]: EITHER (i) the last measure was exact, the remainder in R is zero, and the program can halt, OR (ii) the algorithm must continue: the last measure left a remainder in R less than measuring number in S. IF R = 0 THEN done so GOTO step 15 ELSE CONTINUE TO step 11, E3: [Interchange s and r]: The nut of Euclid's algorithm. Use remainder r to measure what was previously smaller number s; L serves as a temporary location. L ← R R ← S S ← L [Repeat the measuring process]: GOTO 7 OUTPUT: [Done. S contains the greatest common divisor]: PRINT S DONE: HALT, END, STOP. An elegant program for Euclid's algorithm The flowchart of "Elegant" can be found at the top of this article. In the (unstructured) Basic language, the steps are numbered, and the instruction LET [] = [] is the assignment instruction symbolized by ←. 5 REM Euclid's algorithm for greatest common divisor 6 PRINT "Type two integers greater than 0" 10 INPUT A,B 20 IF B=0 THEN GOTO 80 30 IF A > B THEN GOTO 60 40 LET B=B-A 50 GOTO 20 60 LET A=A-B 70 GOTO 20 80 PRINT A 90 END How "Elegant" works: In place of an outer "Euclid loop", "Elegant" shifts back and forth between two "co-loops", an A > B loop that computes A ← A − B, and a B ≤ A loop that computes B ← B − A. This works because, when at last the minuend M is less than or equal to the subtrahend S (Difference = Minuend − Subtrahend), the minuend can become s (the new measuring length) and the subtrahend can become the new r (the length to be measured); in other words the "sense" of the subtraction reverses. The following version can be used with programming languages from the C-family: // Euclid's algorithm for greatest common divisor int euclidAlgorithm (int A, int B){ A=abs(A); B=abs(B); while (B!=0){ while (A>B) A=A-B; B=B-A; } return A; } Testing the Euclid algorithms Does an algorithm do what its author wants it to do? A few test cases usually give some confidence in the core functionality. But tests are not enough. For test cases, one source uses 3009 and 884. Knuth suggested 40902, 24140. Another interesting case is the two relatively prime numbers 14157 and 5950. But "exceptional cases" must be identified and tested. Will "Inelegant" perform properly when R > S, S > R, R = S? Ditto for "Elegant": B > A, A > B, A = B? (Yes to all). What happens when one number is zero, both numbers are zero? ("Inelegant" computes forever in all cases; "Elegant" computes forever when A = 0.) What happens if negative numbers are entered? Fractional numbers? If the input numbers, i.e. the domain of the function computed by the algorithm/program, is to include only positive integers including zero, then the failures at zero indicate that the algorithm (and the program that instantiates it) is a partial function rather than a total function. A notable failure due to exceptions is the Ariane 5 Flight 501 rocket failure (June 4, 1996). Proof of program correctness by use of mathematical induction: Knuth demonstrates the application of mathematical induction to an "extended" version of Euclid's algorithm, and he proposes "a general method applicable to proving the validity of any algorithm". Tausworthe proposes that a measure of the complexity of a program be the length of its correctness proof. Measuring and improving the Euclid algorithms Elegance (compactness) versus goodness (speed): With only six core instructions, "Elegant" is the clear winner, compared to "Inelegant" at thirteen instructions. However, "Inelegant" is faster (it arrives at HALT in fewer steps). Algorithm analysis indicates why this is the case: "Elegant" does two conditional tests in every subtraction loop, whereas "Inelegant" only does one. As the algorithm (usually) requires many loop-throughs, on average much time is wasted doing a "B = 0?" test that is needed only after the remainder is computed. Can the algorithms be improved?: Once the programmer judges a program "fit" and "effective"—that is, it computes the function intended by its author—then the question becomes, can it be improved? The compactness of "Inelegant" can be improved by the elimination of five steps. But Chaitin proved that compacting an algorithm cannot be automated by a generalized algorithm; rather, it can only be done heuristically; i.e., by exhaustive search (examples to be found at Busy beaver), trial and error, cleverness, insight, application of inductive reasoning, etc. Observe that steps 4, 5 and 6 are repeated in steps 11, 12 and 13. Comparison with "Elegant" provides a hint that these steps, together with steps 2 and 3, can be eliminated. This reduces the number of core instructions from thirteen to eight, which makes it "more elegant" than "Elegant", at nine steps. The speed of "Elegant" can be improved by moving the "B=0?" test outside of the two subtraction loops. This change calls for the addition of three instructions (B = 0?, A = 0?, GOTO). Now "Elegant" computes the example-numbers faster; whether this is always the case for any given A, B, and R, S would require a detailed analysis. Algorithmic analysis It is frequently important to know how much of a particular resource (such as time or storage) is theoretically required for a given algorithm. Methods have been developed for the analysis of algorithms to obtain such quantitative answers (estimates); for example, an algorithm which adds up the elements of a list of n numbers would have a time requirement of O(n), using big O notation. At all times the algorithm only needs to remember two values: the sum of all the elements so far, and its current position in the input list. Therefore, it is said to have a space requirement of O(1), if the space required to store the input numbers is not counted, or O(n) if it is counted. Different algorithms may complete the same task with a different set of instructions in less or more time, space, or 'effort' than others. For example, a binary search algorithm (with cost O(log n)) outperforms a sequential search (cost O(n) ) when used for table lookups on sorted lists or arrays. Formal versus empirical The analysis, and study of algorithms is a discipline of computer science, and is often practiced abstractly without the use of a specific programming language or implementation. In this sense, algorithm analysis resembles other mathematical disciplines in that it focuses on the underlying properties of the algorithm and not on the specifics of any particular implementation. Usually pseudocode is used for analysis as it is the simplest and most general representation. However, ultimately, most algorithms are usually implemented on particular hardware/software platforms and their algorithmic efficiency is eventually put to the test using real code. For the solution of a "one off" problem, the efficiency of a particular algorithm may not have significant consequences (unless n is extremely large) but for algorithms designed for fast interactive, commercial or long life scientific usage it may be critical. Scaling from small n to large n frequently exposes inefficient algorithms that are otherwise benign. Empirical testing is useful because it may uncover unexpected interactions that affect performance. Benchmarks may be used to compare before/after potential improvements to an algorithm after program optimization. Empirical tests cannot replace formal analysis, though, and are not trivial to perform in a fair manner. Execution efficiency To illustrate the potential improvements possible even in well-established algorithms, a recent significant innovation, relating to FFT algorithms (used heavily in the field of image processing), can decrease processing time up to 1,000 times for applications like medical imaging. In general, speed improvements depend on special properties of the problem, which are very common in practical applications. Speedups of this magnitude enable computing devices that make extensive use of image processing (like digital cameras and medical equipment) to consume less power. Classification There are various ways to classify algorithms, each with its own merits. By implementation One way to classify algorithms is by implementation means. Recursion A recursive algorithm is one that invokes (makes reference to) itself repeatedly until a certain condition (also known as termination condition) matches, which is a method common to functional programming. Iterative algorithms use repetitive constructs like loops and sometimes additional data structures like stacks to solve the given problems. Some problems are naturally suited for one implementation or the other. For example, towers of Hanoi is well understood using recursive implementation. Every recursive version has an equivalent (but possibly more or less complex) iterative version, and vice versa. Logical An algorithm may be viewed as controlled logical deduction. This notion may be expressed as: Algorithm = logic + control. The logic component expresses the axioms that may be used in the computation and the control component determines the way in which deduction is applied to the axioms. This is the basis for the logic programming paradigm. In pure logic programming languages, the control component is fixed and algorithms are specified by supplying only the logic component. The appeal of this approach is the elegant semantics: a change in the axioms produces a well-defined change in the algorithm. Serial, parallel or distributed Algorithms are usually discussed with the assumption that computers execute one instruction of an algorithm at a time. Those computers are sometimes called serial computers. An algorithm designed for such an environment is called a serial algorithm, as opposed to parallel algorithms or distributed algorithms. Parallel algorithms take advantage of computer architectures where several processors can work on a problem at the same time, whereas distributed algorithms utilize multiple machines connected with a computer network. Parallel or distributed algorithms divide the problem into more symmetrical or asymmetrical subproblems and collect the results back together. The resource consumption in such algorithms is not only processor cycles on each processor but also the communication overhead between the processors. Some sorting algorithms can be parallelized efficiently, but their communication overhead is expensive. Iterative algorithms are generally parallelizable. Some problems have no parallel algorithms and are called inherently serial problems. Deterministic or non-deterministic Deterministic algorithms solve the problem with exact decision at every step of the algorithm whereas non-deterministic algorithms solve problems via guessing although typical guesses are made more accurate through the use of heuristics. Exact or approximate While many algorithms reach an exact solution, approximation algorithms seek an approximation that is closer to the true solution. The approximation can be reached by either using a deterministic or a random strategy. Such algorithms have practical value for many hard problems. One of the examples of an approximate algorithm is the Knapsack problem, where there is a set of given items. Its goal is to pack the knapsack to get the maximum total value. Each item has some weight and some value. Total weight that can be carried is no more than some fixed number X. So, the solution must consider weights of items as well as their value. Quantum algorithm They run on a realistic model of quantum computation. The term is usually used for those algorithms which seem inherently quantum, or use some essential feature of Quantum computing such as quantum superposition or quantum entanglement. By design paradigm Another way of classifying algorithms is by their design methodology or paradigm. There is a certain number of paradigms, each different from the other. Furthermore, each of these categories includes many different types of algorithms. Some common paradigms are: Brute-force or exhaustive search This is the naive method of trying every possible solution to see which is best. Divide and conquer A divide and conquer algorithm repeatedly reduces an instance of a problem to one or more smaller instances of the same problem (usually recursively) until the instances are small enough to solve easily. One such example of divide and conquer is merge sorting. Sorting can be done on each segment of data after dividing data into segments and sorting of entire data can be obtained in the conquer phase by merging the segments. A simpler variant of divide and conquer is called a decrease and conquer algorithm, which solves an identical subproblem and uses the solution of this subproblem to solve the bigger problem. Divide and conquer divides the problem into multiple subproblems and so the conquer stage is more complex than decrease and conquer algorithms. An example of a decrease and conquer algorithm is the binary search algorithm. Search and enumeration Many problems (such as playing chess) can be modeled as problems on graphs. A graph exploration algorithm specifies rules for moving around a graph and is useful for such problems. This category also includes search algorithms, branch and bound enumeration and backtracking. Randomized algorithm Such algorithms make some choices randomly (or pseudo-randomly). They can be very useful in finding approximate solutions for problems where finding exact solutions can be impractical (see heuristic method below). For some of these problems, it is known that the fastest approximations must involve some randomness. Whether randomized algorithms with polynomial time complexity can be the fastest algorithms for some problems is an open question known as the P versus NP problem. There are two large classes of such algorithms: Monte Carlo algorithms return a correct answer with high-probability. E.g. RP is the subclass of these that run in polynomial time. Las Vegas algorithms always return the correct answer, but their running time is only probabilistically bound, e.g. ZPP. Reduction of complexity This technique involves solving a difficult problem by transforming it into a better-known problem for which we have (hopefully) asymptotically optimal algorithms. The goal is to find a reducing algorithm whose complexity is not dominated by the resulting reduced algorithm's. For example, one selection algorithm for finding the median in an unsorted list involves first sorting the list (the expensive portion) and then pulling out the middle element in the sorted list (the cheap portion). This technique is also known as transform and conquer. Back tracking In this approach, multiple solutions are built incrementally and abandoned when it is determined that they cannot lead to a valid full solution. Optimization problems For optimization problems there is a more specific classification of algorithms; an algorithm for such problems may fall into one or more of the general categories described above as well as into one of the following: Linear programming When searching for optimal solutions to a linear function bound to linear equality and inequality constraints, the constraints of the problem can be used directly in producing the optimal solutions. There are algorithms that can solve any problem in this category, such as the popular simplex algorithm. Problems that can be solved with linear programming include the maximum flow problem for directed graphs. If a problem additionally requires that one or more of the unknowns must be an integer then it is classified in integer programming. A linear programming algorithm can solve such a problem if it can be proved that all restrictions for integer values are superficial, i.e., the solutions satisfy these restrictions anyway. In the general case, a specialized algorithm or an algorithm that finds approximate solutions is used, depending on the difficulty of the problem. Dynamic programming When a problem shows optimal substructures—meaning the optimal solution to a problem can be constructed from optimal solutions to subproblems—and overlapping subproblems, meaning the same subproblems are used to solve many different problem instances, a quicker approach called dynamic programming avoids recomputing solutions that have already been computed. For example, Floyd–Warshall algorithm, the shortest path to a goal from a vertex in a weighted graph can be found by using the shortest path to the goal from all adjacent vertices. Dynamic programming and memoization go together. The main difference between dynamic programming and divide and conquer is that subproblems are more or less independent in divide and conquer, whereas subproblems overlap in dynamic programming. The difference between dynamic programming and straightforward recursion is in caching or memoization of recursive calls. When subproblems are independent and there is no repetition, memoization does not help; hence dynamic programming is not a solution for all complex problems. By using memoization or maintaining a table of subproblems already solved, dynamic programming reduces the exponential nature of many problems to polynomial complexity. The greedy method A greedy algorithm is similar to a dynamic programming algorithm in that it works by examining substructures, in this case not of the problem but of a given solution. Such algorithms start with some solution, which may be given or have been constructed in some way, and improve it by making small modifications. For some problems they can find the optimal solution while for others they stop at local optima, that is, at solutions that cannot be improved by the algorithm but are not optimum. The most popular use of greedy algorithms is for finding the minimal spanning tree where finding the optimal solution is possible with this method. Huffman Tree, Kruskal, Prim, Sollin are greedy algorithms that can solve this optimization problem. The heuristic method In optimization problems, heuristic algorithms can be used to find a solution close to the optimal solution in cases where finding the optimal solution is impractical. These algorithms work by getting closer and closer to the optimal solution as they progress. In principle, if run for an infinite amount of time, they will find the optimal solution. Their merit is that they can find a solution very close to the optimal solution in a relatively short time. Such algorithms include local search, tabu search, simulated annealing, and genetic algorithms. Some of them, like simulated annealing, are non-deterministic algorithms while others, like tabu search, are deterministic. When a bound on the error of the non-optimal solution is known, the algorithm is further categorized as an approximation algorithm. By field of study Every field of science has its own problems and needs efficient algorithms. Related problems in one field are often studied together. Some example classes are search algorithms, sorting algorithms, merge algorithms, numerical algorithms, graph algorithms, string algorithms, computational geometric algorithms, combinatorial algorithms, medical algorithms, machine learning, cryptography, data compression algorithms and parsing techniques. Fields tend to overlap with each other, and algorithm advances in one field may improve those of other, sometimes completely unrelated, fields. For example, dynamic programming was invented for optimization of resource consumption in industry but is now used in solving a broad range of problems in many fields. By complexity Algorithms can be classified by the amount of time they need to complete compared to their input size: Constant time: if the time needed by the algorithm is the same, regardless of the input size. E.g. an access to an array element. Logarithmic time: if the time is a logarithmic function of the input size. E.g. binary search algorithm. Linear time: if the time is proportional to the input size. E.g. the traverse of a list. Polynomial time: if the time is a power of the input size. E.g. the bubble sort algorithm has quadratic time complexity. Exponential time: if the time is an exponential function of the input size. E.g. Brute-force search. Some problems may have multiple algorithms of differing complexity, while other problems might have no algorithms or no known efficient algorithms. There are also mappings from some problems to other problems. Owing to this, it was found to be more suitable to classify the problems themselves instead of the algorithms into equivalence classes based on the complexity of the best possible algorithms for them. Continuous algorithms The adjective "continuous" when applied to the word "algorithm" can mean: An algorithm operating on data that represents continuous quantities, even though this data is represented by discrete approximations—such algorithms are studied in numerical analysis; or An algorithm in the form of a differential equation that operates continuously on the data, running on an analog computer. Legal issues Algorithms, by themselves, are not usually patentable. In the United States, a claim consisting solely of simple manipulations of abstract concepts, numbers, or signals does not constitute "processes" (USPTO 2006), and hence algorithms are not patentable (as in Gottschalk v. Benson). However practical applications of algorithms are sometimes patentable. For example, in Diamond v. Diehr, the application of a simple feedback algorithm to aid in the curing of synthetic rubber was deemed patentable. The patenting of software is highly controversial, and there are highly criticized patents involving algorithms, especially data compression algorithms, such as Unisys' LZW patent. Additionally, some cryptographic algorithms have export restrictions (see export of cryptography). History: Development of the notion of "algorithm" Ancient Near East The earliest evidence of algorithms is found in the Babylonian mathematics of ancient Mesopotamia (modern Iraq). A Sumerian clay tablet found in Shuruppak near Baghdad and dated to circa 2500 BC described the earliest division algorithm. During the Hammurabi dynasty circa 1800-1600 BC, Babylonian clay tablets described algorithms for computing formulas. Algorithms were also used in Babylonian astronomy. Babylonian clay tablets describe and employ algorithmic procedures to compute the time and place of significant astronomical events. Algorithms for arithmetic are also found in ancient Egyptian mathematics, dating back to the Rhind Mathematical Papyrus circa 1550 BC. Algorithms were later used in ancient Hellenistic mathematics. Two examples are the Sieve of Eratosthenes, which was described in the Introduction to Arithmetic by Nicomachus, and the Euclidean algorithm, which was first described in Euclid's Elements (c. 300 BC). Discrete and distinguishable symbols Tally-marks: To keep track of their flocks, their sacks of grain and their money the ancients used tallying: accumulating stones or marks scratched on sticks or making discrete symbols in clay. Through the Babylonian and Egyptian use of marks and symbols, eventually Roman numerals and the abacus evolved (Dilson, p. 16–41). Tally marks appear prominently in unary numeral system arithmetic used in Turing machine and Post–Turing machine computations. Manipulation of symbols as "place holders" for numbers: algebra Muhammad ibn Mūsā al-Khwārizmī, a Persian mathematician, wrote the Al-jabr in the 9th century. The terms "algorism" and "algorithm" are derived from the name al-Khwārizmī, while the term "algebra" is derived from the book Al-jabr. In Europe, the word "algorithm" was originally used to refer to the sets of rules and techniques used by Al-Khwarizmi to solve algebraic equations, before later being generalized to refer to any set of rules or techniques. This eventually culminated in Leibniz's notion of the calculus ratiocinator (ca 1680): Cryptographic algorithms The first cryptographic algorithm for deciphering encrypted code was developed by Al-Kindi, a 9th-century Arab mathematician, in A Manuscript On Deciphering Cryptographic Messages. He gave the first description of cryptanalysis by frequency analysis, the earliest codebreaking algorithm. Mechanical contrivances with discrete states The clock: Bolter credits the invention of the weight-driven clock as "The key invention [of Europe in the Middle Ages]", in particular, the verge escapement that provides us with the tick and tock of a mechanical clock. "The accurate automatic machine" led immediately to "mechanical automata" beginning in the 13th century and finally to "computational machines"—the difference engine and analytical engines of Charles Babbage and Countess Ada Lovelace, mid-19th century. Lovelace is credited with the first creation of an algorithm intended for processing on a computer—Babbage's analytical engine, the first device considered a real Turing-complete computer instead of just a calculator—and is sometimes called "history's first programmer" as a result, though a full implementation of Babbage's second device would not be realized until decades after her lifetime. Logical machines 1870 – Stanley Jevons' "logical abacus" and "logical machine": The technical problem was to reduce Boolean equations when presented in a form similar to what is now known as Karnaugh maps. Jevons (1880) describes first a simple "abacus" of "slips of wood furnished with pins, contrived so that any part or class of the [logical] combinations can be picked out mechanically ... More recently, however, I have reduced the system to a completely mechanical form, and have thus embodied the whole of the indirect process of inference in what may be called a Logical Machine" His machine came equipped with "certain moveable wooden rods" and "at the foot are 21 keys like those of a piano [etc.] ...". With this machine he could analyze a "syllogism or any other simple logical argument". This machine he displayed in 1870 before the Fellows of the Royal Society. Another logician John Venn, however, in his 1881 Symbolic Logic, turned a jaundiced eye to this effort: "I have no high estimate myself of the interest or importance of what are sometimes called logical machines ... it does not seem to me that any contrivances at present known or likely to be discovered really deserve the name of logical machines"; see more at Algorithm characterizations. But not to be outdone he too presented "a plan somewhat analogous, I apprehend, to Prof. Jevon's abacus ... [And] [a]gain, corresponding to Prof. Jevons's logical machine, the following contrivance may be described. I prefer to call it merely a logical-diagram machine ... but I suppose that it could do very completely all that can be rationally expected of any logical machine". Jacquard loom, Hollerith punch cards, telegraphy and telephony – the electromechanical relay: Bell and Newell (1971) indicate that the Jacquard loom (1801), precursor to Hollerith cards (punch cards, 1887), and "telephone switching technologies" were the roots of a tree leading to the development of the first computers. By the mid-19th century the telegraph, the precursor of the telephone, was in use throughout the world, its discrete and distinguishable encoding of letters as "dots and dashes" a common sound. By the late 19th century the ticker tape (ca 1870s) was in use, as was the use of Hollerith cards in the 1890 U.S. census. Then came the teleprinter (ca. 1910) with its punched-paper use of Baudot code on tape. Telephone-switching networks of electromechanical relays (invented 1835) was behind the work of George Stibitz (1937), the inventor of the digital adding device. As he worked in Bell Laboratories, he observed the "burdensome' use of mechanical calculators with gears. "He went home one evening in 1937 intending to test his idea... When the tinkering was over, Stibitz had constructed a binary adding device". Davis (2000) observes the particular importance of the electromechanical relay (with its two "binary states" open and closed): It was only with the development, beginning in the 1930s, of electromechanical calculators using electrical relays, that machines were built having the scope Babbage had envisioned." Mathematics during the 19th century up to the mid-20th century Symbols and rules: In rapid succession, the mathematics of George Boole (1847, 1854), Gottlob Frege (1879), and Giuseppe Peano (1888–1889) reduced arithmetic to a sequence of symbols manipulated by rules. Peano's The principles of arithmetic, presented by a new method (1888) was "the first attempt at an axiomatization of mathematics in a symbolic language". But Heijenoort gives Frege (1879) this kudos: Frege's is "perhaps the most important single work ever written in logic. ... in which we see a " 'formula language', that is a lingua characterica, a language written with special symbols, "for pure thought", that is, free from rhetorical embellishments ... constructed from specific symbols that are manipulated according to definite rules". The work of Frege was further simplified and amplified by Alfred North Whitehead and Bertrand Russell in their Principia Mathematica (1910–1913). The paradoxes: At the same time a number of disturbing paradoxes appeared in the literature, in particular, the Burali-Forti paradox (1897), the Russell paradox (1902–03), and the Richard Paradox. The resultant considerations led to Kurt Gödel's paper (1931)—he specifically cites the paradox of the liar—that completely reduces rules of recursion to numbers. Effective calculability: In an effort to solve the Entscheidungsproblem defined precisely by Hilbert in 1928, mathematicians first set about to define what was meant by an "effective method" or "effective calculation" or "effective calculability" (i.e., a calculation that would succeed). In rapid succession the following appeared: Alonzo Church, Stephen Kleene and J.B. Rosser's λ-calculus a finely honed definition of "general recursion" from the work of Gödel acting on suggestions of Jacques Herbrand (cf. Gödel's Princeton lectures of 1934) and subsequent simplifications by Kleene. Church's proof that the Entscheidungsproblem was unsolvable, Emil Post's definition of effective calculability as a worker mindlessly following a list of instructions to move left or right through a sequence of rooms and while there either mark or erase a paper or observe the paper and make a yes-no decision about the next instruction. Alan Turing's proof of that the Entscheidungsproblem was unsolvable by use of his "a- [automatic-] machine"—in effect almost identical to Post's "formulation", J. Barkley Rosser's definition of "effective method" in terms of "a machine". Kleene's proposal of a precursor to "Church thesis" that he called "Thesis I", and a few years later Kleene's renaming his Thesis "Church's Thesis" and proposing "Turing's Thesis". Emil Post (1936) and Alan Turing (1936–37, 1939) Emil Post (1936) described the actions of a "computer" (human being) as follows: "...two concepts are involved: that of a symbol space in which the work leading from problem to answer is to be carried out, and a fixed unalterable set of directions. His symbol space would be "a two-way infinite sequence of spaces or boxes... The problem solver or worker is to move and work in this symbol space, being capable of being in, and operating in but one box at a time.... a box is to admit of but two possible conditions, i.e., being empty or unmarked, and having a single mark in it, say a vertical stroke. "One box is to be singled out and called the starting point. ...a specific problem is to be given in symbolic form by a finite number of boxes [i.e., INPUT] being marked with a stroke. Likewise, the answer [i.e., OUTPUT] is to be given in symbolic form by such a configuration of marked boxes... "A set of directions applicable to a general problem sets up a deterministic process when applied to each specific problem. This process terminates only when it comes to the direction of type (C ) [i.e., STOP]". See more at Post–Turing machine Alan Turing's work preceded that of Stibitz (1937); it is unknown whether Stibitz knew of the work of Turing. Turing's biographer believed that Turing's use of a typewriter-like model derived from a youthful interest: "Alan had dreamt of inventing typewriters as a boy; Mrs. Turing had a typewriter, and he could well have begun by asking himself what was meant by calling a typewriter 'mechanical'". Given the prevalence of Morse code and telegraphy, ticker tape machines, and teletypewriters we might conjecture that all were influences. Turing—his model of computation is now called a Turing machine—begins, as did Post, with an analysis of a human computer that he whittles down to a simple set of basic motions and "states of mind". But he continues a step further and creates a machine as a model of computation of numbers. "Computing is normally done by writing certain symbols on paper. We may suppose this paper is divided into squares like a child's arithmetic book...I assume then that the computation is carried out on one-dimensional paper, i.e., on a tape divided into squares. I shall also suppose that the number of symbols which may be printed is finite... "The behavior of the computer at any moment is determined by the symbols which he is observing, and his "state of mind" at that moment. We may suppose that there is a bound B to the number of symbols or squares which the computer can observe at one moment. If he wishes to observe more, he must use successive observations. We will also suppose that the number of states of mind which need be taken into account is finite... "Let us imagine that the operations performed by the computer to be split up into 'simple operations' which are so elementary that it is not easy to imagine them further divided." Turing's reduction yields the following: "The simple operations must therefore include: "(a) Changes of the symbol on one of the observed squares "(b) Changes of one of the squares observed to another square within L squares of one of the previously observed squares. "It may be that some of these change necessarily invoke a change of state of mind. The most general single operation must, therefore, be taken to be one of the following: "(A) A possible change (a) of symbol together with a possible change of state of mind. "(B) A possible change (b) of observed squares, together with a possible change of state of mind" "We may now construct a machine to do the work of this computer." A few years later, Turing expanded his analysis (thesis, definition) with this forceful expression of it: "A function is said to be "effectively calculable" if its values can be found by some purely mechanical process. Though it is fairly easy to get an intuitive grasp of this idea, it is nevertheless desirable to have some more definite, mathematical expressible definition ... [he discusses the history of the definition pretty much as presented above with respect to Gödel, Herbrand, Kleene, Church, Turing, and Post] ... We may take this statement literally, understanding by a purely mechanical process one which could be carried out by a machine. It is possible to give a mathematical description, in a certain normal form, of the structures of these machines. The development of these ideas leads to the author's definition of a computable function, and to an identification of computability † with effective calculability ... . "† We shall use the expression "computable function" to mean a function calculable by a machine, and we let "effectively calculable" refer to the intuitive idea without particular identification with any one of these definitions". J.B. Rosser (1939) and S.C. Kleene (1943) J. Barkley Rosser defined an 'effective [mathematical] method' in the following manner (italicization added): "'Effective method' is used here in the rather special sense of a method each step of which is precisely determined and which is certain to produce the answer in a finite number of steps. With this special meaning, three different precise definitions have been given to date. [his footnote #5; see discussion immediately below]. The simplest of these to state (due to Post and Turing) says essentially that an effective method of solving certain sets of problems exists if one can build a machine which will then solve any problem of the set with no human intervention beyond inserting the question and (later) reading the answer. All three definitions are equivalent, so it doesn't matter which one is used. Moreover, the fact that all three are equivalent is a very strong argument for the correctness of any one." (Rosser 1939:225–226) Rosser's footnote No. 5 references the work of (1) Church and Kleene and their definition of λ-definability, in particular, Church's use of it in his An Unsolvable Problem of Elementary Number Theory (1936); (2) Herbrand and Gödel and their use of recursion, in particular, Gödel's use in his famous paper On Formally Undecidable Propositions of Principia Mathematica and Related Systems I (1931); and (3) Post (1936) and Turing (1936–37) in their mechanism-models of computation. Stephen C. Kleene defined as his now-famous "Thesis I" known as the Church–Turing thesis. But he did this in the following context (boldface in original): "12. Algorithmic theories... In setting up a complete algorithmic theory, what we do is to describe a procedure, performable for each set of values of the independent variables, which procedure necessarily terminates and in such manner that from the outcome we can read a definite answer, "yes" or "no," to the question, "is the predicate value true?"" (Kleene 1943:273) History after 1950 A number of efforts have been directed toward further refinement of the definition of "algorithm", and activity is on-going because of issues surrounding, in particular, foundations of mathematics (especially the Church–Turing thesis) and philosophy of mind (especially arguments about artificial intelligence). For more, see Algorithm characterizations. See also Abstract machine Algorithm engineering Algorithm characterizations Algorithmic bias Algorithmic composition Algorithmic entities Algorithmic synthesis Algorithmic technique Algorithmic topology Garbage in, garbage out Introduction to Algorithms (textbook) List of algorithms List of algorithm general topics List of important publications in theoretical computer science – Algorithms Regulation of algorithms Theory of computation Computability theory Computational complexity theory Notes Bibliography Bell, C. Gordon and Newell, Allen (1971), Computer Structures: Readings and Examples, McGraw–Hill Book Company, New York. . Includes an excellent bibliography of 56 references. , : cf. Chapter 3 Turing machines where they discuss "certain enumerable sets not effectively (mechanically) enumerable". Campagnolo, M.L., Moore, C., and Costa, J.F. (2000) An analog characterization of the subrecursive functions. In Proc. of the 4th Conference on Real Numbers and Computers, Odense University, pp. 91–109 Reprinted in The Undecidable, p. 89ff. The first expression of "Church's Thesis". See in particular page 100 (The Undecidable) where he defines the notion of "effective calculability" in terms of "an algorithm", and he uses the word "terminates", etc. Reprinted in The Undecidable, p. 110ff. Church shows that the Entscheidungsproblem is unsolvable in about 3 pages of text and 3 pages of footnotes. Davis gives commentary before each article. Papers of Gödel, Alonzo Church, Turing, Rosser, Kleene, and Emil Post are included; those cited in the article are listed here by author's name. Davis offers concise biographies of Leibniz, Boole, Frege, Cantor, Hilbert, Gödel and Turing with von Neumann as the show-stealing villain. Very brief bios of Joseph-Marie Jacquard, Babbage, Ada Lovelace, Claude Shannon, Howard Aiken, etc. , Yuri Gurevich, Sequential Abstract State Machines Capture Sequential Algorithms, ACM Transactions on Computational Logic, Vol 1, no 1 (July 2000), pp. 77–111. Includes bibliography of 33 sources. , 3rd edition 1976[?], (pbk.) , . Cf. Chapter "The Spirit of Truth" for a history leading to, and a discussion of, his proof. Presented to the American Mathematical Society, September 1935. Reprinted in The Undecidable, p. 237ff. Kleene's definition of "general recursion" (known now as mu-recursion) was used by Church in his 1935 paper An Unsolvable Problem of Elementary Number Theory that proved the "decision problem" to be "undecidable" (i.e., a negative result). Reprinted in The Undecidable, p. 255ff. Kleene refined his definition of "general recursion" and proceeded in his chapter "12. Algorithmic theories" to posit "Thesis I" (p. 274); he would later repeat this thesis (in Kleene 1952:300) and name it "Church's Thesis"(Kleene 1952:317) (i.e., the Church thesis). Kosovsky, N.K. Elements of Mathematical Logic and its Application to the theory of Subrecursive Algorithms, LSU Publ., Leningrad, 1981 A.A. Markov (1954) Theory of algorithms. [Translated by Jacques J. Schorr-Kon and PST staff] Imprint Moscow, Academy of Sciences of the USSR, 1954 [i.e., Jerusalem, Israel Program for Scientific Translations, 1961; available from the Office of Technical Services, U.S. Dept. of Commerce, Washington] Description 444 p. 28 cm. Added t.p. in Russian Translation of Works of the Mathematical Institute, Academy of Sciences of the USSR, v. 42. Original title: Teoriya algerifmov. [QA248.M2943 Dartmouth College library. U.S. Dept. of Commerce, Office of Technical Services, number OTS .] Minsky expands his "...idea of an algorithm – an effective procedure..." in chapter 5.1 Computability, Effective Procedures and Algorithms. Infinite machines. Reprinted in The Undecidable, pp. 289ff. Post defines a simple algorithmic-like process of a man writing marks or erasing marks and going from box to box and eventually halting, as he follows a list of simple instructions. This is cited by Kleene as one source of his "Thesis I", the so-called Church–Turing thesis. Reprinted in The Undecidable, p. 223ff. Herein is Rosser's famous definition of "effective method": "...a method each step of which is precisely predetermined and which is certain to produce the answer in a finite number of steps... a machine which will then solve any problem of the set with no human intervention beyond inserting the question and (later) reading the answer" (p. 225–226, The Undecidable) Cf. in particular the first chapter titled: Algorithms, Turing Machines, and Programs. His succinct informal definition: "...any sequence of instructions that can be obeyed by a robot, is called an algorithm" (p. 4). . Corrections, ibid, vol. 43(1937) pp. 544–546. Reprinted in The Undecidable, p. 116ff. Turing's famous paper completed as a Master's dissertation while at King's College Cambridge UK. Reprinted in The Undecidable, pp. 155ff. Turing's paper that defined "the oracle" was his PhD thesis while at Princeton. United States Patent and Trademark Office (2006), 2106.02 **>Mathematical Algorithms: 2100 Patentability, Manual of Patent Examining Procedure (MPEP). Latest revision August 2006 Further reading Knuth, Donald E. (2000). Selected Papers on Analysis of Algorithms. Stanford, California: Center for the Study of Language and Information. Knuth, Donald E. (2010). Selected Papers on Design of Algorithms. Stanford, California: Center for the Study of Language and Information. External links Dictionary of Algorithms and Data Structures – National Institute of Standards and Technology Algorithm repositories The Stony Brook Algorithm Repository – State University of New York at Stony Brook Collected Algorithms of the ACM – Association for Computing Machinery The Stanford GraphBase – Stanford University Articles with example pseudocode Mathematical logic Theoretical computer science

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

780

https://en.wikipedia.org/wiki/Atlas%20%28disambiguation%29

Atlas (disambiguation)

An atlas is a collection of maps, originally named after the Ancient Greek deity. Atlas may also refer to: Mythology Atlas (mythology), an Ancient Greek Titanic deity who held up the celestial sphere Atlas, the first legendary king of Atlantis and further variant of the mythical Titan Atlas of Mauretania, a legendary king of Mauretania and variant of the mythical Titan Places United States Atlas, California Atlas, Illinois Atlas, Texas Atlas, West Virginia Atlas, Wisconsin Atlas District, an area in Washington, D.C. Atlas Peak AVA, a California wine region Atlas Township, Michigan Other Atlas Cinema, a historic movie theatre in Istanbul, Turkey Atlas Mountains, a set of mountain ranges in northwestern Africa Atlas, Nilüfer, a village in Nilüfer district of Bursa Province, Turkey People with the name Atlas (graffiti artist), American graffiti artist Atlas DaBone, American wrestler and football player Charles Atlas (1892–1972), Italian-American bodybuilder Charles Atlas (artist) David Atlas (born 1924), American meteorologist who pioneered weather radar James Atlas (1949-2019), American writer, editor and publisher Meir Atlas (1848–1926), Lithuanian rabbi Natacha Atlas (born 1964), Belgian singer Nava Atlas, American book artist and author Omar Atlas (born 1938), former Venezuelan professional wrestler Scott Atlas (born 1955), American conservative health care policy advisor Teddy Atlas (born 1956), American boxing trainer and commentator Tony Atlas (born 1954), American wrestler and bodybuilder Arts, entertainment, and media Comics Atlas (Drawn and Quarterly), a comic book series by Dylan Horrocks Agents of Atlas, a Marvel Comics mini-series Atlas Comics (1950s), a publisher Atlas/Seaboard Comics, a 1970s line of comics Fictional characters Atlas (DC Comics), the name of several of DC Comics' fictional characters, comic book superheroes, and deities Atlas (Teen Titans), Teen Titans character Atlas, an Astro Boy character Atlas, a BioShock character Atlas, a BattleMech in the BattleTech universe Atlas, an antagonist in Mega Man ZX Advent Atlas, a Portal 2 character Atlas, a PS238 character Erik Josten, a.k.a. Atlas, a Marvel Comics supervillain The Atlas, a strong driving force from No Man's Sky Literature Atlas, a photography book by Gerhard Richter ATLAS of Finite Groups, a group theory book Atlas Shrugged, a novel by Ayn Rand The Atlas (novel), by William T. Vollmann Music Groups Atlas (band), a New Zealand rock band Atlas Sound, the solo musical project of Bradford Cox, lead singer and guitarist of the indie rock band Deerhunter Musicians Black Atlass, a Canadian musician Albums Atlas (Kinky album) Atlas (Parkway Drive album), Parkway Drive's fourth album Atlas (Real Estate album) Atlas (RÜFÜS album) Operas Atlas (opera), 1991 opera by Meredith Monk Atlas: An Opera in Three Parts, 1993 recording of Monk's opera Songs "Atlas" (Battles song), 2007 song by Battles on the album Mirrored "Atlas" (Coldplay song), 2013 song by Coldplay from The Hunger Games: Catching Fire soundtrack "Atlas", a song by Caligula's Horse from the album The Tide, the Thief & River's End "Atlas", the titular song from Parkway Drive's fourth album "Atlas", a song by Man Overboard from Man Overboard "Atlas", a song by Jake Chudnow used as main theme in the YouTube series Mind Field Periodicals Atlas (magazine) The Atlas, a newspaper published in England from 1826 to 1869 Other uses in arts, entertainment, and media Atlas (film) Atlas (statue), iconic statue by Lee Lawrie in Rockefeller Center Atlas, a book about flora and/or fauna of a region, such as atlases of the flora and fauna of Britain and Ireland Atlas Entertainment, a film production company Atlas folio, a book size Atlas Media Corp., a non-fiction entertainment company Atlas Press, a UK publisher RTV Atlas, a broadcaster in Montenegro Atlas Sound, a solo musical project by Bradford Cox The Atlas (video game), a 1991 multiplatform strategy video game Atlas (video game), an upcoming massively-multiplayer online video game Atlas Corporation, a fictional arms manufacturer in the video game series Borderlands (series) Brands and enterprises Atlas (appliance company), a Belarusian company Atlas Consortium, a group of technology companies Atlas Copco, Swedish company founded in 1873 Atlas Corporation, an investment company Atlas Elektronik, a German naval/marine electronics and systems business Atlas Group, a Pakistani business group Atlas Mara Limited, formerly Atlas Mara Co-Nvest Limited, a financial holding company that owns banks in Africa Atlas Model Railroad, American maker of model trains and accessories Atlas Network, formerly Atlas Economic Research Foundation Atlas Press (tool company) Atlas Solutions, a subsidiary of Facebook for digital online advertising, formerly owned by Microsoft Atlas Telecom, a worldwide communications company Atlas Van Lines, a moving company Atlas-Imperial, an American diesel engine manufacturer Dresser Atlas, a provider of oilfield and factory automation services Tele Atlas, a Dutch mapping company Western Atlas, an oilfield services company Computing and technology Atlas (computer), an early supercomputer, built in the 1960s Atlas (robot), a humanoid robot developed by Boston Dynamics and DARPA ATLAS (software), a software flagging naturalized American for denaturalization Atlas, a computer used at the Lawrence Livermore National Laboratory in 2006 Abbreviated Test Language for All Systems, or ATLAS, a MILSPEC language for avionics equipment testing Advanced Technology Leisure Application Simulator, or ATLAS, a hydraulic motion simulator used in theme parks ASP.NET AJAX (formerly "Atlas"), a set of ASP.NET extensions ATLAS Transformation Language, programming language Atlas.ti, a qualitative analysis program Automatically Tuned Linear Algebra Software, or ATLAS, Texture atlas, or image sprite sheet UNIVAC 1101, an early American computer, built in the 1950s Science Astronomy Atlas (comet) (C/2019 Y4) Atlas (crater) on the near side of the Moon Atlas (moon), a satellite of Saturn Atlas (star), also designated 27 Tauri, a triple star system in the constellation of Taurus and a member of the Pleiades Advanced Technology Large-Aperture Space Telescope (ATLAST) Advanced Topographic Laser Altimeter System (ATLAS), a space-based lidar instrument on ICESat-2 Asteroid Terrestrial-impact Last Alert System (ATLAS) Mathematics Atlas (manifolds), a set of smooth charts Atlas (topology), a set of charts Smooth atlas Physics Argonne Tandem Linear Accelerator System, or ATLAS, a linear accelerator at the Argonne National Laboratory ATLAS experiment, a particle detector for the Large Hadron Collider at CERN Atomic-terrace low-angle shadowing, or ATLAS, a nanofabrication technique Biology and healthcare Atlas (anatomy), part of the spine Atlas personality, a term used in psychology to describe the personality of someone whose childhood was characterized by excessive responsibilities Brain atlas, a neuroanatomical map of the brain of a human or other animal Animals and plants Atlas bear Atlas beetle Atlas cedar Atlas moth Atlas pied flycatcher, a bird Atlas turtle Sport Atlas Delmenhorst, a German association football club Atlas F.C., a Mexican professional football club Club Atlético Atlas, an Argentine amateur football club KK Atlas, a former men's professional basketball club based in Belgrade (today's Serbia) Transport Aerospace Atlas (rocket family) SM-65 Atlas intercontinental ballistic missile (ICBM) AeroVelo Atlas, a human-powered helicopter Airbus A400M Atlas, a military aircraft produced 2007–present Armstrong Whitworth Atlas, a British military aeroplane produced 1927–1933 Atlas Air, an American cargo airline Atlas Aircraft, a 1940s aircraft manufacturer Atlas Aircraft Corporation, a South African military aircraft manufacturer Atlas Aviation, an aircraft maintenance firm Atlas Blue, a Moroccan low-cost airline Atlasjet, a Turkish airline Birdman Atlas, an ultralight aircraft HMLAT-303, U.S. Marine Corps helicopter training squadron La Mouette Atlas, a French hang glider design Automotive Atlas (1951 automobile), a French mini-car Atlas (light trucks), a Greek motor vehicle manufacturer Atlas (Pittsburgh automobile), produced 1906–1907 Atlas (Springfield automobile), produced 1907–1913 Atlas, a British van by the Standard Motor Company produced 1958–1962 Atlas Drop Forge Company, a parts subsidiary of REO Motor Car Company Atlas Motor Buggy, an American highwheeler produced in 1909 General Motors Atlas engine Honda Atlas Cars Pakistan, a Pakistani car manufacturer Nissan Atlas, a Japanese light truck Volkswagen Atlas, a sport utility vehicle Geely Atlas, a sport utility vehicle Ships and boats Atlas Werke, a former German shipbuilding company , the name of several Royal Navy ships ST Atlas, a Swedish tugboat , the name of several U.S. Navy ships Trains Atlas, an 1863–1885 South Devon Railway Dido class locomotive Atlas, a 1927–1962 LMS Royal Scot Class locomotive Atlas Car and Manufacturing Company, a locomotive manufacturer Atlas Model Railroad Other uses Atlas (architecture) ATLAS (simulation) (Army Tactical Level Advanced Simulation), a Thai military system Atlas (storm), which hit the Midwestern United States in October 2013, named by The Weather Channel Agrupación de Trabajadores Latinoamericanos Sindicalistas, or ATLAS, a former Latin American trade union confederation in the early 1950s Atlas languages, Berber languages spoken in the Atlas Mountains of Morocco ATLAS Network, a network of European special police units Atlas Uranium Mill See also Altas (disambiguation)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

784

https://en.wikipedia.org/wiki/Alfred%20Korzybski

Alfred Korzybski

Alfred Habdank Skarbek Korzybski (, ; July 3, 1879 – March 1, 1950) was a Polish-American independent scholar who developed a field called general semantics, which he viewed as both distinct from, and more encompassing than, the field of semantics. He argued that human knowledge of the world is limited both by the human nervous system and the languages humans have developed, and thus no one can have direct access to reality, given that the most we can know is that which is filtered through the brain's responses to reality. His best known dictum is "The map is not the territory". Early life and career Born in Warsaw, Poland, then part of the Russian Empire, Korzybski belonged to an aristocratic Polish family whose members had worked as mathematicians, scientists, and engineers for generations. He learned the Polish language at home and the Russian language in schools; and having a French and German governess, he became fluent in four languages as a child. Korzybski studied engineering at the Warsaw University of Technology. During the First World War (1914–1918) Korzybski served as an intelligence officer in the Russian Army. After being wounded in a leg and suffering other injuries, he moved to North America in 1916 (first to Canada, then to the United States) to coordinate the shipment of artillery to Russia. He also lectured to Polish-American audiences about the conflict, promoting the sale of war bonds. After the war he decided to remain in the United States, becoming a naturalized citizen in 1940. He met Mira Edgerly, a painter of portraits on ivory, shortly after the 1918 Armistice; They married in January 1919; the marriage lasted until his death. E. P. Dutton published Korzybski's first book, Manhood of Humanity, in 1921. In this work he proposed and explained in detail a new theory of humankind: mankind as a "time-binding" class of life (humans perform time binding by the transmission of knowledge and abstractions through time which become accreted in cultures). General semantics Korzybski's work culminated in the initiation of a discipline that he named general semantics (GS). This should not be confused with semantics. The basic principles of general semantics, which include time-binding, are described in the publication Science and Sanity, published in 1933. In 1938, Korzybski founded the Institute of General Semantics in Chicago. The post-World War II housing shortage in Chicago cost him the institute's building lease, so in 1946 he moved the institute to Lakeville, Connecticut, U.S., where he directed it until his death in 1950. Korzybski maintained that humans are limited in what they know by (1) the structure of their nervous systems, and (2) the structure of their languages. Humans cannot experience the world directly, but only through their "abstractions" (nonverbal impressions or "gleanings" derived from the nervous system, and verbal indicators expressed and derived from language). These sometimes mislead us about what is the truth. Our understanding sometimes lacks similarity of structure with what is actually happening. He sought to train our awareness of abstracting, using techniques he had derived from his study of mathematics and science. He called this awareness, this goal of his system, "consciousness of abstracting". His system included the promotion of attitudes such as "I don't know; let's see," in order that we may better discover or reflect on its realities as revealed by modern science. Another technique involved becoming inwardly and outwardly quiet, an experience he termed, "silence on the objective levels". "To be" Many devotees and critics of Korzybski reduced his rather complex system to a simple matter of what he said about the verb form "is" of the general verb "to be." His system, however, is based primarily on such terminology as the different "orders of abstraction," and formulations such as "consciousness of abstracting." The contention that Korzybski opposed the use of the verb "to be" would be a profound exaggeration. He thought that certain uses of the verb "to be", called the "is of identity" and the "is of predication", were faulty in structure, e.g., a statement such as, "Elizabeth is a fool" (said of a person named "Elizabeth" who has done something that we regard as foolish). In Korzybski's system, one's assessment of Elizabeth belongs to a higher order of abstraction than Elizabeth herself. Korzybski's remedy was to deny identity; in this example, to be aware continually that "Elizabeth" is not what we call her. We find Elizabeth not in the verbal domain, the world of words, but the nonverbal domain (the two, he said, amount to different orders of abstraction). This was expressed by Korzybski's most famous premise, "the map is not the territory". Note that this premise uses the phrase "is not", a form of "to be"; this and many other examples show that he did not intend to abandon "to be" as such. In fact, he said explicitly that there were no structural problems with the verb "to be" when used as an auxiliary verb or when used to state existence or location. It was even acceptable at times to use the faulty forms of the verb "to be," as long as one was aware of their structural limitations. Anecdotes One day, Korzybski was giving a lecture to a group of students, and he interrupted the lesson suddenly in order to retrieve a packet of biscuits, wrapped in white paper, from his briefcase. He muttered that he just had to eat something, and he asked the students on the seats in the front row if they would also like a biscuit. A few students took a biscuit. "Nice biscuit, don't you think," said Korzybski, while he took a second one. The students were chewing vigorously. Then he tore the white paper from the biscuits, in order to reveal the original packaging. On it was a big picture of a dog's head and the words "Dog Cookies." The students looked at the package, and were shocked. Two of them wanted to vomit, put their hands in front of their mouths, and ran out of the lecture hall to the toilet. "You see," Korzybski remarked, "I have just demonstrated that people don't just eat food, but also words, and that the taste of the former is often outdone by the taste of the latter." William Burroughs went to a Korzybski workshop in the Autumn of 1939. He was 25 years old, and paid $40. His fellow students—there were 38 in all—included young Samuel I. Hayakawa (later to become a Republican member of the U.S. Senate) and Wendell Johnson (founder of the Monster Study). Influence Korzybski was well received in numerous disciplines, as evidenced by the positive reactions from leading figures in the sciences and humanities in the 1940s and 1950s. These include author Robert A. Heinlein naming a character after him in his 1940 short story "Blowups Happen", and science fiction writer A. E. van Vogt in his novel "The World of Null-A", published in 1948. Korzybski's ideas influenced philosopher Alan Watts who used his phrase "the map is not the territory" in lectures. Writer Robert Anton Wilson was also deeply influenced by Korzybski's ideas. As reported in the third edition of Science and Sanity, in World War II the US Army used Korzybski's system to treat battle fatigue in Europe, under the supervision of Dr. Douglas M. Kelley, who went on to become the psychiatrist in charge of the Nazi war criminals at Nuremberg. Some of the General Semantics tradition was continued by Samuel I. Hayakawa. See also Alfred Korzybski Memorial Lecture Concept and object E-Prime Institute of General Semantics Robert Pula Structural differential References Further reading Kodish, Bruce. 2011. Korzybski: A Biography. Pasadena, CA: Extensional Publishing. softcover, 978-09700664-28 hardcover. Kodish, Bruce and Susan Presby Kodish. 2011. Drive Yourself Sane: Using the Uncommon Sense of General Semantics, Third Edition. Pasadena, CA: Extensional Publishing. Alfred Korzybski, Manhood of Humanity, foreword by Edward Kasner, notes by M. Kendig, Institute of General Semantics, 1950, hardcover, 2nd edition, 391 pages, . (Copy of the first edition.) Science and Sanity: An Introduction to Non-Aristotelian Systems and General Semantics, Alfred Korzybski, preface by Robert P. Pula, Institute of General Semantics, 1994, hardcover, 5th edition, . (Full text online.) Alfred Korzybski, Collected Writings 1920-1950, Institute of General Semantics, 1990, hardcover, Montagu, M. F. A. (1953). Time-binding and the concept of culture. The Scientific Monthly, Vol. 77, No. 3 (Sep., 1953), pp. 148–155. Murray, E. (1950). In memoriam: Alfred H. Korzybski. Sociometry, Vol. 13, No. 1 (Feb., 1950), pp. 76–77. External links Alfred Korzybski and Gestalt Therapy Website Australian General Semantics Society Institute of General Semantics Finding aid to Alfred Korzybski papers at Columbia University. Rare Book & Manuscript Library. 1879 births 1950 deaths Writers from Warsaw Clan Abdank Polish emigrants to the United States Polish engineers 20th-century Polish philosophers Polish mathematicians Linguists from Poland General semantics People from Lakeville, Connecticut

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

785

https://en.wikipedia.org/wiki/Asteroids%20%28video%20game%29

Asteroids (video game)

Asteroids is a space-themed multidirectional shooter arcade game designed by Lyle Rains and Ed Logg released in November 1979 by Atari, Inc. The player controls a single spaceship in an asteroid field which is periodically traversed by flying saucers. The object of the game is to shoot and destroy the asteroids and saucers, while not colliding with either, or being hit by the saucers' counter-fire. The game becomes harder as the number of asteroids increases. Asteroids was one of the first major hits of the golden age of arcade games; the game sold over 70,000 arcade cabinets and proved both popular with players and influential with developers. In the 1980s it was ported to Atari's home systems, and the Atari VCS version sold over three million copies. The game was widely imitated, and it directly influenced Defender, Gravitar, and many other video games. Asteroids was conceived during a meeting between Logg and Rains, who decided to use hardware developed by Howard Delman previously used for Lunar Lander. Asteroids was based on an unfinished game titled Cosmos; its physics model, control scheme, and gameplay elements were derived from Spacewar!, Computer Space, and Space Invaders and refined through trial and error. The game is rendered on a vector display in a two-dimensional view that wraps around both screen axes. Gameplay The objective of Asteroids is to destroy asteroids and saucers. The player controls a triangular ship that can rotate left and right, fire shots straight forward, and thrust forward. Once the ship begins moving in a direction, it will continue in that direction for a time without player intervention unless the player applies thrust in a different direction. The ship eventually comes to a stop when not thrusting. The player can also send the ship into hyperspace, causing it to disappear and reappear in a random location on the screen, at the risk of self-destructing or appearing on top of an asteroid. Each level starts with a few large asteroids drifting in various directions on the screen. Objects wrap around screen edges – for instance, an asteroid that drifts off the top edge of the screen reappears at the bottom and continues moving in the same direction. As the player shoots asteroids, they break into smaller asteroids that move faster and are more difficult to hit. Smaller asteroids are also worth more points. Two flying saucers appear periodically on the screen; the "big saucer" shoots randomly and poorly, while the "small saucer" fires frequently at the ship. After reaching a score of 40,000, only the small saucer appears. As the player's score increases, the angle range of the shots from the small saucer diminishes until the saucer fires extremely accurately. Once the screen has been cleared of all asteroids and flying saucers, a new set of large asteroids appears, thus starting the next level. The game gets harder as the number of asteroids increases until after the score reaches a range between 40,000 and 60,000. The player starts with 3–5 lives upon game start and gains an extra life per 10,000 points. Play continues to the last ship lost, which ends the game. Machine "turns over" at 99,990 points, which is the maximum high score that can be achieved. Lurking exploit In the original game design, saucers were supposed to begin shooting as soon as they appeared, but this was changed. Additionally, saucers can only aim at the player's ship on-screen; they are not capable of aiming across a screen boundary. These behaviors allow a "lurking" strategy, in which the player stays near the edge of the screen opposite the saucer. By keeping just one or two rocks in play, a player can shoot across the boundary and destroy saucers to accumulate points indefinitely with little risk of being destroyed. Arcade operators began to complain about losing revenue due to this exploit. In response, Atari issued a patched EPROM and, due to the impact of this exploit, Atari (and other companies) changed their development and testing policies to try to prevent future games from having such exploits. Development Concept Asteroids was conceived by Lyle Rains and programmed by Ed Logg with collaborations from other Atari staff. Logg was impressed with the Atari Video Computer System (later called the Atari 2600), and he joined Atari's coin-op division to work on Dirt Bike, which was never released due to an unsuccessful field test. Paul Mancuso joined the development team as Asteroids technician and engineer Howard Delman contributed to the hardware. During a meeting in April 1979, Rains discussed Planet Grab, a multiplayer arcade game later renamed to Cosmos. Logg did not know the name of the game, thinking Computer Space as "the inspiration for the two-dimensional approach". Rains conceived of Asteroids as a mixture of Computer Space and Space Invaders, combining the two-dimensional approach of Computer Space with Space Invaders addictive gameplay of "completion" and "eliminate all threats". The unfinished game featured a giant, indestructible asteroid, so Rains asked Logg: "Well, why don’t we have a game where you shoot the rocks and blow them up?" In response, Logg described a similar concept where the player selectively shoots at rocks that break into smaller pieces. Both agreed on the concept. Hardware Asteroids was implemented on hardware developed by Delman and is a vector game, in which the graphics are composed of lines drawn on a vector monitor. Rains initially wanted the game done in raster graphics, but Logg, experienced in vector graphics, suggested an XY monitor because the high image quality would permit precise aiming. The hardware is chiefly a MOS 6502 executing the game program, and QuadraScan, a high-resolution vector graphics processor developed by Atari and referred to as an "XY display system" and the "Digital Vector Generator (DVG)". The original design concepts for QuadraScan came out of Cyan Engineering, Atari's off-campus research lab in Grass Valley, California, in 1978. Cyan gave it to Delman, who finished the design and first used it for Lunar Lander. Logg received Delman's modified board with five buttons, 13 sound effects, and additional RAM, and he used it to develop Asteroids. The size of the board was 4 by 4 inches, and it was "linked up" to a monitor. Implementation Logg modeled the player's ship, the five-button control scheme, and the game physics after Spacewar!, which he had played as a student at the University of California, Berkeley, but made several changes to improve playability. The ship was programmed into the hardware and rendered by the monitor, and it was configured to move with thrust and inertia. The hyperspace button was not placed near Logg's right thumb, which he was dissatisfied with, as he had a problem "tak[ing] his hand off the thrust button". Drawings of asteroids in various shapes were incorporated into the game. Logg copied the idea of a high score table with initials from Exidy's Star Fire. The two saucers were formulated to be different from each other. A steadily decreasing timer shortens intervals between saucer attacks to keep the player from not shooting asteroids and saucers. A "heartbeat" soundtrack quickens as the game progresses. The game does not have a sound chip. Delman created a hardware circuit for 13 sound effects by hand which was wired onto the board. A prototype of Asteroids was well received by several Atari staff and engineers, who "wander[ed] between labs, passing comment and stopping to play as they went". Logg was often asked when he would be leaving by employees eager to play the prototype, so he created a second prototype for staff to play. Atari tested the game in arcades in Sacramento, California, and also observed players during focus group sessions at Atari. Players used to Spacewar! struggled to maintain grip on the thrust button and requested a joystick; players accustomed to Space Invaders noted they get no break in the game. Logg and other engineers observed proceedings and documented comments in four pages. Asteroids slows down as the player gains 50–100 lives, because there is no limit to the number of lives displayed. The player can "lose" the game after more than 250 lives are collected. Ports Asteroids was released for the Atari VCS (later renamed the Atari 2600) and Atari 8-bit family in 1981, then the Atari 7800 in 1986. A port for the Atari 5200, identical to the Atari 8-bit computer version, was in development in 1982, but was not published. The Atari 7800 version was a launch title and includes cooperative play; the asteroids have colorful textures and the "heartbeat" sound effect remains intact. Programmers Brad Stewart and Bob Smith were unable to fit the Atari VCS port into a 4 KB cartridge. It became the first game for the console to use bank switching, a technique that increases ROM size from 4 KB to 8 KB. Reception Asteroids was immediately successful upon release. It displaced Space Invaders by popularity in the United States and became Atari's best selling arcade game of all time, with over 70,000 units sold. Atari earned an estimated $150 million in sales from the game, and arcade operators earned a further $500 million from coin drops. Atari had been in the process of manufacturing another vector game, Lunar Lander, but demand for Asteroids was so high "that several hundred Asteroids games were shipped in Lunar Lander cabinets". Asteroids was so popular that some video arcade operators had to install large boxes to hold the number of coins spent by players. It replaced Space Invaders at the top of the US RePlay amusement arcade charts in April 1980, though Space Invaders remained the top game at street locations. Asteroids went on to become the highest-grossing arcade video game of 1980 in the United States, dethroning Space Invaders. It shipped 70,000 arcade units worldwide in 1980, including over 60,000 sold in the United States that year, and grossed about worldwide ( adjusted for inflation) by 1980. The game remained at the top of the US RePlay charts through March 1981. However, the game did not perform as well overseas in Europe and Asia. It sold 30,000 arcade units overseas, for a total of 100,000 arcade units sold worldwide. Atari manufactured 76,312 units from its US and Ireland plants, including 21,394 Asteroids Deluxe units. It was a commercial failure in Japan when it released there in 1980, partly due to its complex controls and partly due to the Japanese market beginning to lose interest in space shoot 'em ups at the time. Asteroids received positive reviews from video game critics and has been regarded as Logg's magnum opus. Richard A. Edwards reviewed the 1981 Asteroids home cartridge in The Space Gamer No. 46. Edwards commented that "this home cartridge is a virtual duplicate of the ever-popular Atari arcade game. [...] If blasting asteroids is the thing you want to do then this is the game, but at this price I can't wholeheartedly recommend it". Video Games Player magazine reviewed the Atari VCS version, rating the graphics and sound a B, while giving the game an overall B+ rating. Electronic Fun with Computers & Games magazine gave the Atari VCS version an A rating. William Cassidy, writing for GameSpy's "Classic Gaming", noticed its innovations, including being one of the first video games to track initials and allow players to enter their initials for appearing in the top 10 high scores, and commented, "the vector graphics fit the futuristic outer space theme very well". In 1996, Next Generation listed it as number 39 on their "Top 100 Games of All Time", particularly lauding the control dynamics which require "the constant juggling of speed, positioning, and direction". In 1999, Next Generation listed Asteroids as number 29 on their "Top 50 Games of All Time", commenting that "Asteroid was a classic the day it was released, and it has never lost any of its appeal". Asteroids was ranked fourth on Retro Gamers list of "Top 25 Arcade Games"; the Retro Gamer staff cited its simplicity and the lack of a proper ending as allowances of revisiting the game. In 2012, Asteroids was listed on Time All-Time 100 greatest video games list. Entertainment Weekly named Asteroids one of the top ten games for the Atari 2600 in 2013. It was added to the Museum of Modern Art's collection of video games. In 2021, The Guardian listed Asteroids as the second greatest video game of the 1970s, just below Galaxian (1979). By contrast, in March 1983 the Atari 8-bit port of Asteroids won sixth place in Softlines Dog of the Year awards "for badness in computer games", Atari division, based on reader submissions. Usage of the names of Saturday Night Live characters "Mr. Bill" and "Sluggo" to refer to the saucers in an Esquire article about the game led to Logg receiving a cease and desist letter from a lawyer with the "Mr. Bill Trademark". Legacy Arcade sequels Released in 1981, Asteroids Deluxe was the first sequel to Asteroids. Dave Shepperd edited the code and made enhancements to the game without Logg's involvement. The onscreen objects are tinted blue, and hyperspace is replaced by a shield that depletes when used. The asteroids rotate, and new "killer satellite" enemies break into smaller ships that home in on the player's position. The arcade machine's monitor displays vector graphics overlaying a holographic backdrop. The game is more difficult than the original and enables saucers to shoot across the screen boundary, eliminating the lurking strategy for high scores in the original. It was followed by Owen Rubin's Space Duel in 1982, featuring colorful geometric shapes and co-op multiplayer gameplay. In 1987's Blasteroids, Ed Rotberg added "power-ups, ship morphing, branching levels, bosses, and the ability to dock your ships in multiplayer for added firepower". Blasteroids uses raster graphics instead of vectors. Re-releases The game is half of the Atari Lynx pairing Super Asteroids & Missile Command, and included in the 1993 Microsoft Arcade compilation. Activision published an enhanced version of Asteroids for the PlayStation (1998), Nintendo 64 (1999), Microsoft Windows (1998), Game Boy Color (1999), and Macintosh (2000). The Atari Flashback series of dedicated video game consoles have included both the 2600 and the arcade versions of Asteroids. Published by Crave Entertainment on December 14, 1999, Asteroids Hyper 64 made the ship and asteroids 3D and added new weapons and a multiplayer mode. A technical demo of Asteroids was developed by iThink for the Atari Jaguar but was never released. Unofficially referred to as Asteroids 2000, it was demonstrated at E-JagFest 2000. In 2001, Infogrames released Atari Anniversary Edition for the Dreamcast, PlayStation, and Microsoft Windows. Developed by Digital Eclipse, it includes emulated versions of Asteroids and other games. The arcade and Atari 2600 versions of Asteroids were included in Atari Anthology for both Xbox and PlayStation 2. Released on November 28, 2007, the Xbox Live Arcade port of Asteroids has revamped HD graphics along with an added intense "throttle monkey" mode. The arcade and 2600 versions were made available through Microsofts Game Room service in 2010. Glu Mobile released an enhanced mobile phone port. Asteroids is included on Atari Greatest Hits Volume 1 for the Nintendo DS. An updated version of the game was announced in 2018 for the Intellivision Amico. Both the Atari 2600 and Atari 7800 versions of the game was included on Atari Collection 1 and 2 in 2020 for the Evercade. Clones Quality Software's Asteroids in Space (1980) was one of the best selling games for the Apple II and voted one of the most popular software titles of 1978-80 by Softalk magazine. In December 1981, Byte reviewed eight Asteroids clones for home computers. Three other Apple II Asteroids clones were reviewed together in the 1982 Creative Computing Software Buyers Guide: The Asteroid Field, Asteron, and Apple-Oids. In the last of these, the asteroids are in the shape of apples. Two independent clones, Asteroid for the Apple II and Fasteroids for TRS-80, were renamed to Planetoids and sold by Adventure International. Others clones include Acornsoft's Meteors, Moons of Jupiter for the VIC-20, and MineStorm for the Vectrex. The Mattel Intellivision game Meteor! , an Asteroids clone, was cancelled to avoid a lawsuit, and was reworked as Astrosmash. The game borrows elements from Asteroids and Space Invaders. Elon Musk, when he was a 12 year-old child, programmed a space shoot 'em up game inspired by Space Invaders and Asteroids, called Blastar, which was published for the Commodore VIC-20 in 1984. World records On February 6, 1982, Leo Daniels of Carolina Beach, North Carolina, set a world record score of 40,101,910 points. On November 13 of the same year, 15-year-old Scott Safran of Cherry Hill, New Jersey, set a new record at 41,336,440 points. In 1998, to congratulate Safran on his accomplishment, the Twin Galaxies Intergalactic Scoreboard searched for him for four years until 2002, when it was discovered that he had died in an accident in 1989. In a ceremony in Philadelphia on April 27, 2002, Walter Day of Twin Galaxies presented an award to the surviving members of Safran's family, commemorating his achievement. On April 5, 2010, John McAllister broke Safran's record with a high score of 41,838,740 in a 58-hour Internet livestream. Some claim that the true world record for Asteroids was set in a laundromat in Hyde Park, New York, from June 30 to July 3, 1982, and that details of the score of over 48 million were published in the July 4th edition of the Poughkeepsie Journal. References External links at Atari 1979 video games Arcade video games Atari 2600 games Atari 7800 games Atari 8-bit family games Atari arcade games Atari Lynx games Cancelled Atari 5200 games Cancelled Atari Jaguar games Ed Logg games Game Boy games Game Boy Color games Multidirectional shooters Multiplayer and single-player video games Science fiction video games Sega arcade games Taito arcade games Xbox 360 games Xbox 360 Live Arcade games Vector arcade video games Video games developed in the United States

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

803

https://en.wikipedia.org/wiki/Arabic

Arabic

Arabic (, or , or ) is a Semitic language that first emerged in the 1st to 4th centuries CE. It is the lingua franca of the Arab world and the liturgical language of Islam. It is named after the Arabs, a term initially used to describe peoples living in the Arabian Peninsula bounded by eastern Egypt in the west, Mesopotamia in the east, and the Anti-Lebanon mountains and northern Syria in the north, as perceived by ancient Greek geographers. The ISO assigns language codes to 32 varieties of Arabic, including its standard form, Modern Standard Arabic, also referred to as Literary Arabic, which is modernized Classical Arabic. This distinction exists primarily among Western linguists; Arabic speakers themselves generally do not distinguish between Modern Standard Arabic and Classical Arabic, but rather refer to both as ( "the eloquent Arabic") or simply (). Arabic is widely taught in schools and universities around the world and is used to varying degrees in workplaces, governments and the media. Arabic, in its Modern Standard Arabic form, is an official language of 26 states and 1 disputed territory, the third most after English and French; it is also the liturgical language of the religion of Islam, since the Quran and the Hadiths were written in Classical Arabic. During the early Middle Ages, Arabic was a major vehicle of culture in the Mediterranean region, especially in science, mathematics and philosophy. As a result, many European languages have also borrowed many words from it. Arabic influence, mainly in vocabulary, is seen in European languages—mainly Spanish and to a lesser extent Portuguese, Catalan, and Sicilian—owing to both the proximity of Christian European and Muslim Arabized civilizations and the long-lasting Muslim culture and Arabic language presence, mainly in Southern Iberia, during the Al-Andalus era. The Maltese language is a Semitic language developed from a dialect of Arabic and written in the Latin alphabet. The Balkan languages, including Greek and Bulgarian, have also acquired a significant number of words of Arabic origin through contact with Ottoman Turkish. Arabic has influenced many other languages around the globe throughout its history especially languages of Muslim cultures and countries that were conquered by Muslims. Some of the most influenced languages are Persian, Turkish, Hindustani (Hindi and Urdu), Kashmiri, Kurdish, Bosnian, Kazakh, Bengali, Malay (Indonesian and Malaysian), Maldivian, Pashto, Punjabi, Albanian, Armenian, Azerbaijani, Sicilian, Spanish, Greek, Bulgarian, Tagalog, Sindhi, Odia Hebrew and Hausa and some languages in parts of Africa. Conversely, Arabic has borrowed words from other languages, including Aramaic as well as Hebrew, Latin, Greek, Persian and to a lesser extent Turkish (due to the Ottoman Empire), English and French (due to their colonization of the Levant) and other Semitic languages such as Abyssinian. Arabic is the liturgical language of 1.9 billion Muslims, and Arabic is one of six official languages of the United Nations. All varieties of Arabic combined are spoken by perhaps as many as 422 million speakers (native and non-native) in the Arab world, making it the fifth most spoken language in the world, and the fourth most used language on the internet in terms of users. In 2011, Bloomberg Businessweek ranked Arabic the fourth most useful language for business, after English, Standard Mandarin Chinese, and French. Arabic is written with the Arabic alphabet, which is an abjad script and is written from right to left, although the spoken varieties are sometimes written in ASCII Latin from left to right with no standardized orthography. Classification Arabic is usually, but not universally, classified as a Central Semitic language. It is related to languages in other subgroups of the Semitic language group (Northwest Semitic, South Semitic, East Semitic, West Semitic), such as Aramaic, Syriac, Hebrew, Ugaritic, Phoenician, Canaanite, Amorite, Ammonite, Eblaite, epigraphic Ancient North Arabian, epigraphic Ancient South Arabian, Ethiopic, Modern South Arabian, and numerous other dead and modern languages. Linguists still differ as to the best classification of Semitic language sub-groups. The Semitic languages changed a great deal between Proto-Semitic and the emergence of the Central Semitic languages, particularly in grammar. Innovations of the Central Semitic languages—all maintained in Arabic—include: The conversion of the suffix-conjugated stative formation (jalas-) into a past tense. The conversion of the prefix-conjugated preterite-tense formation (yajlis-) into a present tense. The elimination of other prefix-conjugated mood/aspect forms (e.g., a present tense formed by doubling the middle root, a perfect formed by infixing a after the first root consonant, probably a jussive formed by a stress shift) in favor of new moods formed by endings attached to the prefix-conjugation forms (e.g., -u for indicative, -a for subjunctive, no ending for jussive, -an or -anna for energetic). The development of an internal passive. There are several features which Classical Arabic, the modern Arabic varieties, as well as the Safaitic and Hismaic inscriptions share which are unattested in any other Central Semitic language variety, including the Dadanitic and Taymanitic languages of the northern Hejaz. These features are evidence of common descent from a hypothetical ancestor, Proto-Arabic. The following features can be reconstructed with confidence for Proto-Arabic: negative particles * ; * to Classical Arabic G-passive participle prepositions and adverbs , , , , a subjunctive in - -demonstratives leveling of the - allomorph of the feminine ending complementizer and subordinator the use of - to introduce modal clauses independent object pronoun in vestiges of nunation History Old Arabic Arabia boasted a wide variety of Semitic languages in antiquity. In the southwest, various Central Semitic languages both belonging to and outside of the Ancient South Arabian family (e.g. Southern Thamudic) were spoken. It is also believed that the ancestors of the Modern South Arabian languages (non-Central Semitic languages) were also spoken in southern Arabia at this time. To the north, in the oases of northern Hejaz, Dadanitic and Taymanitic held some prestige as inscriptional languages. In Najd and parts of western Arabia, a language known to scholars as Thamudic C is attested. In eastern Arabia, inscriptions in a script derived from ASA attest to a language known as Hasaitic. Finally, on the northwestern frontier of Arabia, various languages known to scholars as Thamudic B, Thamudic D, Safaitic, and Hismaic are attested. The last two share important isoglosses with later forms of Arabic, leading scholars to theorize that Safaitic and Hismaic are in fact early forms of Arabic and that they should be considered Old Arabic. Linguists generally believe that "Old Arabic" (a collection of related dialects that constitute the precursor of Arabic) first emerged around the 1st century CE. Previously, the earliest attestation of Old Arabic was thought to be a single 1st century CE inscription in Sabaic script at Qaryat Al-Faw, in southern present-day Saudi Arabia. However, this inscription does not participate in several of the key innovations of the Arabic language group, such as the conversion of Semitic mimation to nunation in the singular. It is best reassessed as a separate language on the Central Semitic dialect continuum. It was also thought that Old Arabic coexisted alongside—and then gradually displaced--epigraphic Ancient North Arabian (ANA), which was theorized to have been the regional tongue for many centuries. ANA, despite its name, was considered a very distinct language, and mutually unintelligible, from "Arabic". Scholars named its variant dialects after the towns where the inscriptions were discovered (Dadanitic, Taymanitic, Hismaic, Safaitic). However, most arguments for a single ANA language or language family were based on the shape of the definite article, a prefixed h-. It has been argued that the h- is an archaism and not a shared innovation, and thus unsuitable for language classification, rendering the hypothesis of an ANA language family untenable. Safaitic and Hismaic, previously considered ANA, should be considered Old Arabic due to the fact that they participate in the innovations common to all forms of Arabic.The earliest attestation of continuous Arabic text in an ancestor of the modern Arabic script are three lines of poetry by a man named Garm(')allāhe found in En Avdat, Israel, and dated to around 125 CE. This is followed by the Namara inscription, an epitaph of the Lakhmid king Imru' al-Qays bar 'Amro, dating to 328 CE, found at Namaraa, Syria. From the 4th to the 6th centuries, the Nabataean script evolves into the Arabic script recognizable from the early Islamic era. There are inscriptions in an undotted, 17-letter Arabic script dating to the 6th century CE, found at four locations in Syria (Zabad, Jabal 'Usays, Harran, Umm al-Jimaal). The oldest surviving papyrus in Arabic dates to 643 CE, and it uses dots to produce the modern 28-letter Arabic alphabet. The language of that papyrus and of the Qur'an are referred to by linguists as "Quranic Arabic", as distinct from its codification soon thereafter into "Classical Arabic". Old Hejazi and Classical Arabic In late pre-Islamic times, a transdialectal and transcommunal variety of Arabic emerged in the Hejaz which continued living its parallel life after literary Arabic had been institutionally standardized in the 2nd and 3rd century of the Hijra, most strongly in Judeo-Christian texts, keeping alive ancient features eliminated from the "learned" tradition (Classical Arabic). This variety and both its classicizing and "lay" iterations have been termed Middle Arabic in the past, but they are thought to continue an Old Higazi register. It is clear that the orthography of the Qur'an was not developed for the standardized form of Classical Arabic; rather, it shows the attempt on the part of writers to record an archaic form of Old Higazi. In the late 6th century AD, a relatively uniform intertribal "poetic koine" distinct from the spoken vernaculars developed based on the Bedouin dialects of Najd, probably in connection with the court of al-Ḥīra. During the first Islamic century, the majority of Arabic poets and Arabic-writing persons spoke Arabic as their mother tongue. Their texts, although mainly preserved in far later manuscripts, contain traces of non-standardized Classical Arabic elements in morphology and syntax. Standardization Abu al-Aswad al-Du'ali (c. 603–689) is credited with standardizing Arabic grammar, or an-naḥw ( "the way"), and pioneering a system of diacritics to differentiate consonants ( nuqat l-i'jām "pointing for non-Arabs") and indicate vocalization ( at-tashkil). Al-Khalil ibn Ahmad al-Farahidi (718 – 786) compiled the first Arabic dictionary, Kitāb al-'Ayn ( "The Book of the Letter ع"), and is credited with establishing the rules of Arabic prosody. Al-Jahiz (776-868) proposed to Al-Akhfash al-Akbar an overhaul of the grammar of Arabic, but it would not come to pass two centuries. The standardization of Arabic reached completion around the end of the 8th century. The first comprehensive description of the ʿarabiyya "Arabic", Sībawayhi's al-Kitāb, is based first of all upon a corpus of poetic texts, in addition to Qur'an usage and Bedouin informants whom he considered to be reliable speakers of the ʿarabiyya. Spread Arabic spread with the spread of Islam. Following the early Muslim conquests, Arabic gained vocabulary from Middle Persian and Turkish. In the early Abbasid period, many Classical Greek terms entered Arabic through translations carried out at Baghdad's House of Wisdom. By the 8th century, knowledge of Classical Arabic had become an essential prerequisite for rising into the higher classes throughout the Islamic world, both for Muslims and non-Muslims. For example, Maimonides, the Andalusi Jewish philosopher, authored works in Judeo-Arabic—Arabic written in Hebrew script—including his famous The Guide for the Perplexed ( Dalālat al-ḥāʾirīn). Development Ibn Jinni of Mosul, a pioneer in phonology, wrote prolifically in the 10th century on Arabic morphology and phonology in works such as Kitāb Al-Munṣif, Kitāb Al-Muḥtasab, and . Ibn Mada' of Cordoba (1116–1196) realized the overhaul of Arabic grammar first proposed by Al-Jahiz 200 years prior. The Maghrebi lexicographer Ibn Manzur compiled (لسان العرب, "Tongue of Arabs"), a major reference dictionary of Arabic, in 1290. Neo-Arabic Charles Ferguson's koine theory (Ferguson 1959) claims that the modern Arabic dialects collectively descend from a single military koine that sprang up during the Islamic conquests; this view has been challenged in recent times. Ahmad al-Jallad proposes that there were at least two considerably distinct types of Arabic on the eve of the conquests: Northern and Central (Al-Jallad 2009). The modern dialects emerged from a new contact situation produced following the conquests. Instead of the emergence of a single or multiple koines, the dialects contain several sedimentary layers of borrowed and areal features, which they absorbed at different points in their linguistic histories. According to Veersteegh and Bickerton, colloquial Arabic dialects arose from pidginized Arabic formed from contact between Arabs and conquered peoples. Pidginization and subsequent creolization among Arabs and arabized peoples could explain relative morphological and phonological simplicity of vernacular Arabic compared to Classical and MSA. In around the 11th and 12th centuries in al-Andalus, the zajal and muwashah poetry forms developed in the dialectical Arabic of Cordoba and the Maghreb. Nahda The Nahda was a cultural and especially literary renaissance of the 19th century in which writers sought "to fuse Arabic and European forms of expression." According to James L. Gelvin, "Nahda writers attempted to simplify the Arabic language and script so that it might be accessible to a wider audience." In the wake of the industrial revolution and European hegemony and colonialism, pioneering Arabic presses, such as the Amiri Press established by Muhammad Ali (1819), dramatically changed the diffusion and consumption of Arabic literature and publications. Rifa'a al-Tahtawi proposed the establishment of in 1836 and led a translation campaign that highlighted the need for a lexical injection in Arabic, to suit concepts of the industrial and post-industrial age. In response, a number of Arabic academies modeled after the Académie française were established with the aim of developing standardized additions to the Arabic lexicon to suit these transformations, first in Damascus (1919), then in Cairo (1932), Baghdad (1948), Rabat (1960), Amman (1977), (1993), and Tunis (1993). In 1997, a bureau of Arabization standardization was added to the Educational, Cultural, and Scientific Organization of the Arab League. These academies and organizations have worked toward the Arabization of the sciences, creating terms in Arabic to describe new concepts, toward the standardization of these new terms throughout the Arabic-speaking world, and toward the development of Arabic as a world language. This gave rise to what Western scholars call Modern Standard Arabic. From the 1950s, Arabization became a postcolonial nationalist policy in countries such as Tunisia, Algeria, Morocco, and Sudan. Classical, Modern Standard and spoken Arabic Arabic usually refers to Standard Arabic, which Western linguists divide into Classical Arabic and Modern Standard Arabic. It could also refer to any of a variety of regional vernacular Arabic dialects, which are not necessarily mutually intelligible. Classical Arabic is the language found in the Quran, used from the period of Pre-Islamic Arabia to that of the Abbasid Caliphate. Classical Arabic is prescriptive, according to the syntactic and grammatical norms laid down by classical grammarians (such as Sibawayh) and the vocabulary defined in classical dictionaries (such as the Lisān al-ʻArab). Modern Standard Arabic (MSA) largely follows the grammatical standards of Classical Arabic and uses much of the same vocabulary. However, it has discarded some grammatical constructions and vocabulary that no longer have any counterpart in the spoken varieties and has adopted certain new constructions and vocabulary from the spoken varieties. Much of the new vocabulary is used to denote concepts that have arisen in the industrial and post-industrial era, especially in modern times. Due to its grounding in Classical Arabic, Modern Standard Arabic is removed over a millennium from everyday speech, which is construed as a multitude of dialects of this language. These dialects and Modern Standard Arabic are described by some scholars as not mutually comprehensible. The former are usually acquired in families, while the latter is taught in formal education settings. However, there have been studies reporting some degree of comprehension of stories told in the standard variety among preschool-aged children. The relation between Modern Standard Arabic and these dialects is sometimes compared to that of Classical Latin and Vulgar Latin vernaculars (which became Romance languages) in medieval and early modern Europe. This view though does not take into account the widespread use of Modern Standard Arabic as a medium of audiovisual communication in today's mass media—a function Latin has never performed. MSA is the variety used in most current, printed Arabic publications, spoken by some of the Arabic media across North Africa and the Middle East, and understood by most educated Arabic speakers. "Literary Arabic" and "Standard Arabic" ( ) are less strictly defined terms that may refer to Modern Standard Arabic or Classical Arabic. Some of the differences between Classical Arabic (CA) and Modern Standard Arabic (MSA) are as follows: Certain grammatical constructions of CA that have no counterpart in any modern vernacular dialect (e.g., the energetic mood) are almost never used in Modern Standard Arabic. Case distinctions are very rare in Arabic vernaculars. As a result, MSA is generally composed without case distinctions in mind, and the proper cases are added after the fact, when necessary. Because most case endings are noted using final short vowels, which are normally left unwritten in the Arabic script, it is unnecessary to determine the proper case of most words. The practical result of this is that MSA, like English and Standard Chinese, is written in a strongly determined word order and alternative orders that were used in CA for emphasis are rare. In addition, because of the lack of case marking in the spoken varieties, most speakers cannot consistently use the correct endings in extemporaneous speech. As a result, spoken MSA tends to drop or regularize the endings except when reading from a prepared text. The numeral system in CA is complex and heavily tied in with the case system. This system is never used in MSA, even in the most formal of circumstances; instead, a significantly simplified system is used, approximating the system of the conservative spoken varieties. MSA uses much Classical vocabulary (e.g., 'to go') that is not present in the spoken varieties, but deletes Classical words that sound obsolete in MSA. In addition, MSA has borrowed or coined many terms for concepts that did not exist in Quranic times, and MSA continues to evolve. Some words have been borrowed from other languages—notice that transliteration mainly indicates spelling and not real pronunciation (e.g., 'film' or 'democracy'). However, the current preference is to avoid direct borrowings, preferring to either use loan translations (e.g., 'branch', also used for the branch of a company or organization; 'wing', is also used for the wing of an airplane, building, air force, etc.), or to coin new words using forms within existing roots ( 'apoptosis', using the root m/w/t 'death' put into the Xth form, or 'university', based on 'to gather, unite'; 'republic', based on 'multitude'). An earlier tendency was to redefine an older word although this has fallen into disuse (e.g., 'telephone' < 'invisible caller (in Sufism)'; 'newspaper' < 'palm-leaf stalk'). Colloquial or dialectal Arabic refers to the many national or regional varieties which constitute the everyday spoken language and evolved from Classical Arabic. Colloquial Arabic has many regional variants; geographically distant varieties usually differ enough to be mutually unintelligible, and some linguists consider them distinct languages. However, research indicates a high degree of mutual intelligibility between closely related Arabic variants for native speakers listening to words, sentences, and texts; and between more distantly related dialects in interactional situations. The varieties are typically unwritten. They are often used in informal spoken media, such as soap operas and talk shows, as well as occasionally in certain forms of written media such as poetry and printed advertising. The only variety of modern Arabic to have acquired official language status is Maltese, which is spoken in (predominantly Catholic) Malta and written with the Latin script. It is descended from Classical Arabic through Siculo-Arabic, but is not mutually intelligible with any other variety of Arabic. Most linguists list it as a separate language rather than as a dialect of Arabic. Even during Muhammad's lifetime, there were dialects of spoken Arabic. Muhammad spoke in the dialect of Mecca, in the western Arabian peninsula, and it was in this dialect that the Quran was written down. However, the dialects of the eastern Arabian peninsula were considered the most prestigious at the time, so the language of the Quran was ultimately converted to follow the eastern phonology. It is this phonology that underlies the modern pronunciation of Classical Arabic. The phonological differences between these two dialects account for some of the complexities of Arabic writing, most notably the writing of the glottal stop or hamzah (which was preserved in the eastern dialects but lost in western speech) and the use of (representing a sound preserved in the western dialects but merged with in eastern speech). Language and dialect The sociolinguistic situation of Arabic in modern times provides a prime example of the linguistic phenomenon of diglossia, which is the normal use of two separate varieties of the same language, usually in different social situations. Tawleed is the process of giving a new shade of meaning to an old classical word. For example, al-hatif lexicographically, means the one whose sound is heard but whose person remains unseen. Now the term al-hatif is used for a telephone. Therefore, the process of tawleed can express the needs of modern civilization in a manner that would appear to be originally Arabic. In the case of Arabic, educated Arabs of any nationality can be assumed to speak both their school-taught Standard Arabic as well as their native dialects, which depending on the region may be mutually unintelligible. Some of these dialects can be considered to constitute separate languages which may have “sub-dialects” of their own. When educated Arabs of different dialects engage in conversation (for example, a Moroccan speaking with a Lebanese), many speakers code-switch back and forth between the dialectal and standard varieties of the language, sometimes even within the same sentence. Arabic speakers often improve their familiarity with other dialects via music or film. The issue of whether Arabic is one language or many languages is politically charged, in the same way it is for the varieties of Chinese, Hindi and Urdu, Serbian and Croatian, Scots and English, etc. In contrast to speakers of Hindi and Urdu who claim they cannot understand each other even when they can, speakers of the varieties of Arabic will claim they can all understand each other even when they cannot. While there is a minimum level of comprehension between all Arabic dialects, this level can increase or decrease based on geographic proximity: for example, Levantine and Gulf speakers understand each other much better than they do speakers from the Maghreb. The issue of diglossia between spoken and written language is a significant complicating factor: A single written form, significantly different from any of the spoken varieties learned natively, unites a number of sometimes divergent spoken forms. For political reasons, Arabs mostly assert that they all speak a single language, despite significant issues of mutual incomprehensibility among differing spoken versions. From a linguistic standpoint, it is often said that the various spoken varieties of Arabic differ among each other collectively about as much as the Romance languages. This is an apt comparison in a number of ways. The period of divergence from a single spoken form is similar—perhaps 1500 years for Arabic, 2000 years for the Romance languages. Also, while it is comprehensible to people from the Maghreb, a linguistically innovative variety such as Moroccan Arabic is essentially incomprehensible to Arabs from the Mashriq, much as French is incomprehensible to Spanish or Italian speakers but relatively easily learned by them. This suggests that the spoken varieties may linguistically be considered separate languages. Influence of Arabic on other languages The influence of Arabic has been most important in Islamic countries, because it is the language of the Islamic sacred book, the Quran. Arabic is also an important source of vocabulary for languages such as Amharic, Azerbaijani, Baluchi, Bengali, Berber, Bosnian, Chaldean, Chechen, Chittagonian, Croatian, Dagestani, Dhivehi, English, German, Gujarati, Hausa, Hindi, Kazakh, Kurdish, Kutchi, Kyrgyz, Malay (Malaysian and Indonesian), Pashto, Persian, Punjabi, Rohingya, Romance languages (French, Catalan, Italian, Portuguese, Sicilian, Spanish, etc.) Saraiki, Sindhi, Somali, Sylheti, Swahili, Tagalog, Tigrinya, Turkish, Turkmen, Urdu, Uyghur, Uzbek, Visayan and Wolof, as well as other languages in countries where these languages are spoken.Modern Hebrew has been also influenced by Arabic especially during the process of revival, as MSA was used as a source for modern Hebrew vocabulary and roots, as well as much of Modern Hebrew's slang. The Education Minister of France Jean-Michel Blanquer has emphasized the learning and usage of Arabic in French schools. In addition, English has many Arabic loanwords, some directly, but most via other Mediterranean languages. Examples of such words include admiral, adobe, alchemy, alcohol, algebra, algorithm, alkaline, almanac, amber, arsenal, assassin, candy, carat, cipher, coffee, cotton, ghoul, hazard, jar, kismet, lemon, loofah, magazine, mattress, sherbet, sofa, sumac, tariff, and zenith. Other languages such as Maltese and Kinubi derive ultimately from Arabic, rather than merely borrowing vocabulary or grammatical rules. Terms borrowed range from religious terminology (like Berber taẓallit, "prayer", from salat ( )), academic terms (like Uyghur mentiq, "logic"), and economic items (like English coffee) to placeholders (like Spanish fulano, "so-and-so"), everyday terms (like Hindustani lekin, "but", or Spanish taza and French tasse, meaning "cup"), and expressions (like Catalan a betzef, "galore, in quantity"). Most Berber varieties (such as Kabyle), along with Swahili, borrow some numbers from Arabic. Most Islamic religious terms are direct borrowings from Arabic, such as (salat), "prayer", and (imam), "prayer leader." In languages not directly in contact with the Arab world, Arabic loanwords are often transferred indirectly via other languages rather than being transferred directly from Arabic. For example, most Arabic loanwords in Hindustani and Turkish entered through Persian. Older Arabic loanwords in Hausa were borrowed from Kanuri. Most Arabic loanwords in Yoruba entered through Hausa. Arabic words also made their way into several West African languages as Islam spread across the Sahara. Variants of Arabic words such as kitāb ("book") have spread to the languages of African groups who had no direct contact with Arab traders. Since, throughout the Islamic world, Arabic occupied a position similar to that of Latin in Europe, many of the Arabic concepts in the fields of science, philosophy, commerce, etc. were coined from Arabic roots by non-native Arabic speakers, notably by Aramaic and Persian translators, and then found their way into other languages. This process of using Arabic roots, especially in Kurdish and Persian, to translate foreign concepts continued through to the 18th and 19th centuries, when swaths of Arab-inhabited lands were under Ottoman rule. Influence of other languages on Arabic The most important sources of borrowings into (pre-Islamic) Arabic are from the related (Semitic) languages Aramaic, which used to be the principal, international language of communication throughout the ancient Near and Middle East, and Ethiopic. In addition, many cultural, religious and political terms have entered Arabic from Iranian languages, notably Middle Persian, Parthian, and (Classical) Persian, and Hellenistic Greek (kīmiyāʼ has as origin the Greek khymia, meaning in that language the melting of metals; see Roger Dachez, Histoire de la Médecine de l'Antiquité au XXe siècle, Tallandier, 2008, p. 251), alembic (distiller) from ambix (cup), almanac (climate) from almenichiakon (calendar). (For the origin of the last three borrowed words, see Alfred-Louis de Prémare, Foundations of Islam, Seuil, L'Univers Historique, 2002.) Some Arabic borrowings from Semitic or Persian languages are, as presented in De Prémare's above-cited book: madīnah/medina (مدينة, city or city square), a word of Aramaic origin “madenta” (in which it means "a state"). jazīrah (جزيرة), as in the well-known form الجزيرة "Al-Jazeera," means "island" and has its origin in the Syriac ܓܙܝܪܗ gazarta. lāzaward (لازورد) is taken from Persian لاژورد lājvard, the name of a blue stone, lapis lazuli. This word was borrowed in several European languages to mean (light) blue – azure in English, azur in French and azul in Portuguese and Spanish. A comprehensive overview of the influence of other languages on Arabic is found in Lucas & Manfredi (2020). Arabic alphabet and nationalism There have been many instances of national movements to convert Arabic script into Latin script or to Romanize the language. Currently, the only language derived from Classical Arabic to use Latin script is Maltese. Lebanon The Beirut newspaper La Syrie pushed for the change from Arabic script to Latin letters in 1922. The major head of this movement was Louis Massignon, a French Orientalist, who brought his concern before the Arabic Language Academy in Damascus in 1928. Massignon's attempt at Romanization failed as the Academy and population viewed the proposal as an attempt from the Western world to take over their country. Sa'id Afghani, a member of the Academy, mentioned that the movement to Romanize the script was a Zionist plan to dominate Lebanon. Said Akl created a Latin-based alphabet for Lebanese and used it in a newspaper he founded, Lebnaan, as well as in some books he wrote. Egypt After the period of colonialism in Egypt, Egyptians were looking for a way to reclaim and re-emphasize Egyptian culture. As a result, some Egyptians pushed for an Egyptianization of the Arabic language in which the formal Arabic and the colloquial Arabic would be combined into one language and the Latin alphabet would be used. There was also the idea of finding a way to use Hieroglyphics instead of the Latin alphabet, but this was seen as too complicated to use. A scholar, Salama Musa agreed with the idea of applying a Latin alphabet to Arabic, as he believed that would allow Egypt to have a closer relationship with the West. He also believed that Latin script was key to the success of Egypt as it would allow for more advances in science and technology. This change in alphabet, he believed, would solve the problems inherent with Arabic, such as a lack of written vowels and difficulties writing foreign words that made it difficult for non-native speakers to learn. Ahmad Lutfi As Sayid and Muhammad Azmi, two Egyptian intellectuals, agreed with Musa and supported the push for Romanization. The idea that Romanization was necessary for modernization and growth in Egypt continued with Abd Al-Aziz Fahmi in 1944. He was the chairman for the Writing and Grammar Committee for the Arabic Language Academy of Cairo. However, this effort failed as the Egyptian people felt a strong cultural tie to the Arabic alphabet. In particular, the older Egyptian generations believed that the Arabic alphabet had strong connections to Arab values and history, due to the long history of the Arabic alphabet (Shrivtiel, 189) in Muslim societies. The language of the Quran and its influence on poetry The Quran introduced a new way of writing to the world. People began studying and applying the unique styles they learned from the Quran to not only their own writing, but also their culture. Writers studied the unique structure and format of the Quran in order to identify and apply the figurative devices and their impact on the reader. Quran's figurative devices The Quran inspired musicality in poetry through the internal rhythm of the verses. The arrangement of words, how certain sounds create harmony, and the agreement of rhymes create the sense of rhythm within each verse. At times, the chapters of the Quran only have the rhythm in common. The repetition in the Quran introduced the true power and impact repetition can have in poetry. The repetition of certain words and phrases made them appear more firm and explicit in the Quran. The Quran uses constant metaphors of blindness and deafness to imply unbelief. Metaphors were not a new concept to poetry, however the strength of extended metaphors was. The explicit imagery in the Quran inspired many poets to include and focus on the feature in their own work. The poet ibn al-Mu'tazz wrote a book regarding the figures of speech inspired by his study of the Quran. Poet Badr Shakir al-Sayyab expresses his political opinion in his work through imagery inspired by the forms of more harsher imagery used in the Quran. The Quran uses figurative devices in order to express the meaning in the most beautiful form possible. The study of the pauses in the Quran as well as other rhetoric allow it to be approached in a multiple ways. Structure Although the Quran is known for its fluency and harmony, the structure can be best described as not always being inherently chronological, but can also flow thematically instead (the chapters in the Quran have segments that flow in chronological order, however segments can transition into other segments not related in chronology, but could be related in topic). The suras, also known as chapters of the Quran, are not placed in chronological order. The only constant in their structure is that the longest are placed first and shorter ones follow. The topics discussed in the chapters can also have no direct relation to each other (as seen in many suras) and can share in their sense of rhyme. The Quran introduces to poetry the idea of abandoning order and scattering narratives throughout the text. Harmony is also present in the sound of the Quran. The elongations and accents present in the Quran create a harmonious flow within the writing. Unique sound of the Quran recited, due to the accents, create a deeper level of understanding through a deeper emotional connection. The Quran is written in a language that is simple and understandable by people. The simplicity of the writing inspired later poets to write in a more clear and clear-cut style. The words of the Quran, although unchanged, are to this day understandable and frequently used in both formal and informal Arabic. The simplicity of the language makes memorizing and reciting the Quran a slightly easier task. Culture and the Quran The writer al-Khattabi explains how culture is a required element to create a sense of art in work as well as understand it. He believes that the fluency and harmony which the Quran possess are not the only elements that make it beautiful and create a bond between the reader and the text. While a lot of poetry was deemed comparable to the Quran in that it is equal to or better than the composition of the Quran, a debate rose that such statements are not possible because humans are incapable of composing work comparable to the Quran. Because the structure of the Quran made it difficult for a clear timeline to be seen, Hadith were the main source of chronological order. The Hadith were passed down from generation to generation and this tradition became a large resource for understanding the context. Poetry after the Quran began possessing this element of tradition by including ambiguity and background information to be required to understand the meaning. After the Quran came down to the people, the tradition of memorizing the verses became present. It is believed that the greater the amount of the Quran memorized, the greater the faith. As technology improved over time, hearing recitations of the Quran became more available as well as more tools to help memorize the verses. The tradition of Love Poetry served as a symbolic representation of a Muslim's desire for a closer contact with their Lord. While the influence of the Quran on Arabic poetry is explained and defended by numerous writers, some writers such as Al-Baqillani believe that poetry and the Quran are in no conceivable way related due to the uniqueness of the Quran. Poetry's imperfections prove his points that they cannot be compared with the fluency the Quran holds. Arabic and Islam Classical Arabic is the language of poetry and literature (including news); it is also mainly the language of the Quran. Classical Arabic is closely associated with the religion of Islam because the Quran was written in it. Most of the world's Muslims do not speak Classical Arabic as their native language, but many can read the Quranic script and recite the Quran. Among non-Arab Muslims, translations of the Quran are most often accompanied by the original text. At present, Modern Standard Arabic (MSA) is also used in modernized versions of literary forms of the Quran. Some Muslims present a monogenesis of languages and claim that the Arabic language was the language revealed by God for the benefit of mankind and the original language as a prototype system of symbolic communication, based upon its system of triconsonantal roots, spoken by man from which all other languages were derived, having first been corrupted. Judaism has a similar account with the Tower of Babel. Dialects and descendants Colloquial Arabic is a collective term for the spoken dialects of Arabic used throughout the Arab world, which differ radically from the literary language. The main dialectal division is between the varieties within and outside of the Arabian peninsula, followed by that between sedentary varieties and the much more conservative Bedouin varieties. All the varieties outside of the Arabian peninsula (which include the large majority of speakers) have many features in common with each other that are not found in Classical Arabic. This has led researchers to postulate the existence of a prestige koine dialect in the one or two centuries immediately following the Arab conquest, whose features eventually spread to all newly conquered areas. These features are present to varying degrees inside the Arabian peninsula. Generally, the Arabian peninsula varieties have much more diversity than the non-peninsula varieties, but these have been understudied. Within the non-peninsula varieties, the largest difference is between the non-Egyptian North African dialects (especially Moroccan Arabic) and the others. Moroccan Arabic in particular is hardly comprehensible to Arabic speakers east of Libya (although the converse is not true, in part due to the popularity of Egyptian films and other media). One factor in the differentiation of the dialects is influence from the languages previously spoken in the areas, which have typically provided a significant number of new words and have sometimes also influenced pronunciation or word order; however, a much more significant factor for most dialects is, as among Romance languages, retention (or change of meaning) of different classical forms. Thus Iraqi aku, Levantine fīh and North African kayən all mean 'there is', and all come from Classical Arabic forms (yakūn, fīhi, kā'in respectively), but now sound very different. Examples Transcription is a broad IPA transcription, so minor differences were ignored for easier comparison. Also, the pronunciation of Modern Standard Arabic differs significantly from region to region. Koiné According to Charles A. Ferguson, the following are some of the characteristic features of the koiné that underlies all the modern dialects outside the Arabian peninsula. Although many other features are common to most or all of these varieties, Ferguson believes that these features in particular are unlikely to have evolved independently more than once or twice and together suggest the existence of the koine: Loss of the dual number except on nouns, with consistent plural agreement (cf. feminine singular agreement in plural inanimates). Change of a to i in many affixes (e.g., non-past-tense prefixes ti- yi- ni-; wi- 'and'; il- 'the'; feminine -it in the construct state). Loss of third-weak verbs ending in w (which merge with verbs ending in y). Reformation of geminate verbs, e.g., 'I untied' → . Conversion of separate words lī 'to me', laka 'to you', etc. into indirect-object clitic suffixes. Certain changes in the cardinal number system, e.g., 'five days' → , where certain words have a special plural with prefixed t. Loss of the feminine elative (comparative). Adjective plurals of the form 'big' → . Change of nisba suffix > . Certain lexical items, e.g., 'bring' < 'come with'; 'see'; 'what' (or similar) < 'which thing'; (relative pronoun). Merger of and . Dialect groups Egyptian Arabic is spoken by around 53 million people in Egypt (55 million worldwide). It is one of the most understood varieties of Arabic, due in large part to the widespread distribution of Egyptian films and television shows throughout the Arabic-speaking world Levantine Arabic includes North Levantine Arabic, South Levantine Arabic and Cypriot Arabic. It is spoken by about 21 million people in Lebanon, Syria, Jordan, Palestine, Israel, Cyprus and Turkey. Lebanese Arabic is a variety of Levantine Arabic spoken primarily in Lebanon. Jordanian Arabic is a continuum of mutually intelligible varieties of Levantine Arabic spoken by the population of the Kingdom of Jordan. Palestinian Arabic is a name of several dialects of the subgroup of Levantine Arabic spoken by the Palestinians in Palestine, by Arab citizens of Israel and in most Palestinian populations around the world. Samaritan Arabic, spoken by only several hundred in the Nablus region Cypriot Maronite Arabic, spoken in Cyprus Maghrebi Arabic, also called "Darija" spoken by about 70 million people in Morocco, Algeria, Tunisia and Libya. It also forms the basis of Maltese via the extinct Sicilian Arabic dialect. Maghrebi Arabic is very hard to understand for Arabic speakers from the Mashriq or Mesopotamia, the most comprehensible being Libyan Arabic and the most difficult Moroccan Arabic. The others such as Algerian Arabic can be considered in between the two in terms of difficulty. Libyan Arabic spoken in Libya and neighboring countries. Tunisian Arabic spoken in Tunisia and North-eastern Algeria Algerian Arabic spoken in Algeria Judeo-Algerian Arabic was spoken by Jews in Algeria until 1962 Moroccan Arabic spoken in Morocco Hassaniya Arabic (3 million speakers), spoken in Mauritania, Western Sahara, some parts of the Azawad in northern Mali, southern Morocco and south-western Algeria. Andalusian Arabic, spoken in Spain until the 16th century. Siculo-Arabic (Sicilian Arabic), was spoken in Sicily and Malta between the end of the 9th century and the end of the 12th century and eventually evolved into the Maltese language. Maltese, spoken on the island of Malta, is the only fully separate standardized language to have originated from an Arabic dialect (the extinct Siculo-Arabic dialect), with independent literary norms. Maltese has evolved independently of Modern Standard Arabic and its varieties into a standardized language over the past 800 years in a gradual process of Latinisation. Maltese is therefore considered an exceptional descendant of Arabic that has no diglossic relationship with Standard Arabic or Classical Arabic. Maltese is also different from Arabic and other Semitic languages since its morphology has been deeply influenced by Romance languages, Italian and Sicilian. It is also the only Semitic language written in the Latin script. In terms of basic everyday language, speakers of Maltese are reported to be able to understand less than a third of what is said to them in Tunisian Arabic, which is related to Siculo-Arabic, whereas speakers of Tunisian are able to understand about 40% of what is said to them in Maltese. This asymmetric intelligibility is considerably lower than the mutual intelligibility found between Maghrebi Arabic dialects. Maltese has its own dialects, with urban varieties of Maltese being closer to Standard Maltese than rural varieties. Mesopotamian Arabic, spoken by about 41.2 million people in Iraq (where it is called "Aamiyah"), eastern Syria and southwestern Iran (Khuzestan) and in the southeastern of Turkey (in the eastern Mediterranean, Southeastern Anatolia Region) North Mesopotamian Arabic is a spoken north of the Hamrin Mountains in Iraq, in western Iran, northern Syria, and in southeastern Turkey (in the eastern Mediterranean Region, Southeastern Anatolia Region, and southern Eastern Anatolia Region). Judeo-Mesopotamian Arabic, also known as Iraqi Judeo Arabic and Yahudic, is a variety of Arabic spoken by Iraqi Jews of Mosul. Baghdad Arabic is the Arabic dialect spoken in Baghdad, and the surrounding cities and it is a subvariety of Mesopotamian Arabic. Baghdad Jewish Arabic is the dialect spoken by the Iraqi Jews of Baghdad. South Mesopotamian Arabic (Basrawi dialect) is the dialect spoken in southern Iraq, such as Basra, Dhi Qar and Najaf. Khuzestani Arabic is the dialect spoken in the Iranian province of Khuzestan. This dialect is a mix of Southen Mesopotamian Arabic and Gulf Arabic. Khorasani Arabic spoken in the Iranian province of Khorasan. Kuwaiti Arabic is a Gulf Arabic dialect spoken in Kuwait. Sudanese Arabic is spoken by 17 million people in Sudan and some parts of southern Egypt. Sudanese Arabic is quite distinct from the dialect of its neighbor to the north; rather, the Sudanese have a dialect similar to the Hejazi dialect. Juba Arabic spoken in South Sudan and southern Sudan Gulf Arabic, spoken by around four million people, predominantly in Kuwait, Bahrain, some parts of Oman, eastern Saudi Arabia coastal areas and some parts of UAE and Qatar. Also spoken in Iran's Bushehr and Hormozgan provinces. Although Gulf Arabic is spoken in Qatar, most Qatari citizens speak Najdi Arabic (Bedawi). Omani Arabic, distinct from the Gulf Arabic of Eastern Arabia and Bahrain, spoken in Central Oman. With recent oil wealth and mobility has spread over other parts of the Sultanate. Hadhrami Arabic, spoken by around 8 million people, predominantly in Hadhramaut, and in parts of the Arabian Peninsula, South and Southeast Asia, and East Africa by Hadhrami descendants. Yemeni Arabic spoken in Yemen, and southern Saudi Arabia by 15 million people. Similar to Gulf Arabic. Najdi Arabic, spoken by around 10 million people, mainly spoken in Najd, central and northern Saudi Arabia. Most Qatari citizens speak Najdi Arabic (Bedawi). Hejazi Arabic (6 million speakers), spoken in Hejaz, western Saudi Arabia Saharan Arabic spoken in some parts of Algeria, Niger and Mali Baharna Arabic (600,000 speakers), spoken by Bahrani Shiʻah in Bahrain and Qatif, the dialect exhibits many big differences from Gulf Arabic. It is also spoken to a lesser extent in Oman. Judeo-Arabic dialects – these are the dialects spoken by the Jews that had lived or continue to live in the Arab World. As Jewish migration to Israel took hold, the language did not thrive and is now considered endangered. So-called Qəltu Arabic. Chadian Arabic, spoken in Chad, Sudan, some parts of South Sudan, Central African Republic, Niger, Nigeria, Cameroon Central Asian Arabic, spoken in Uzbekistan, Tajikistan and Afghanistan, is highly endangered Shirvani Arabic, spoken in Azerbaijan and Dagestan until the 1930s, now extinct. Phonology History Of the 29 Proto-Semitic consonants, only one has been lost: , which merged with , while became (see Semitic languages). Various other consonants have changed their sound too, but have remained distinct. An original lenited to , and – consistently attested in pre-Islamic Greek transcription of Arabic languages – became palatalized to or by the time of the Quran and , , or after early Muslim conquests and in MSA (see Arabic phonology#Local variations for more detail). An original voiceless alveolar lateral fricative became . Its emphatic counterpart was considered by Arabs to be the most unusual sound in Arabic (Hence the Classical Arabic's appellation or "language of the "); for most modern dialects, it has become an emphatic stop with loss of the laterality or with complete loss of any pharyngealization or velarization, . (The classical pronunciation of pharyngealization still occurs in the Mehri language, and the similar sound without velarization, , exists in other Modern South Arabian languages.) Other changes may also have happened. Classical Arabic pronunciation is not thoroughly recorded and different reconstructions of the sound system of Proto-Semitic propose different phonetic values. One example is the emphatic consonants, which are pharyngealized in modern pronunciations but may have been velarized in the eighth century and glottalized in Proto-Semitic. Reduction of and between vowels occurs in a number of circumstances and is responsible for much of the complexity of third-weak ("defective") verbs. Early Akkadian transcriptions of Arabic names shows that this reduction had not yet occurred as of the early part of the 1st millennium BC. The Classical Arabic language as recorded was a poetic koine that reflected a consciously archaizing dialect, chosen based on the tribes of the western part of the Arabian Peninsula, who spoke the most conservative variants of Arabic. Even at the time of Muhammed and before, other dialects existed with many more changes, including the loss of most glottal stops, the loss of case endings, the reduction of the diphthongs and into monophthongs , etc. Most of these changes are present in most or all modern varieties of Arabic. An interesting feature of the writing system of the Quran (and hence of Classical Arabic) is that it contains certain features of Muhammad's native dialect of Mecca, corrected through diacritics into the forms of standard Classical Arabic. Among these features visible under the corrections are the loss of the glottal stop and a differing development of the reduction of certain final sequences containing : Evidently, final became as in the Classical language, but final became a different sound, possibly (rather than again in the Classical language). This is the apparent source of the alif maqṣūrah 'restricted alif' where a final is reconstructed: a letter that would normally indicate or some similar high-vowel sound, but is taken in this context to be a logical variant of alif and represent the sound . Although Classical Arabic was a unitary language and is now used in Quran, its pronunciation varies somewhat from country to country and from region to region within a country. It is influenced by colloquial dialects. Literary Arabic The "colloquial" spoken dialects of Arabic are learned at home and constitute the native languages of Arabic speakers. "Formal" Modern Standard Arabic is learned at school; although many speakers have a native-like command of the language, it is technically not the native language of any speakers. Both varieties can be both written and spoken, although the colloquial varieties are rarely written down and the formal variety is spoken mostly in formal circumstances, e.g., in radio and TV broadcasts, formal lectures, parliamentary discussions and to some extent between speakers of different colloquial dialects. Even when the literary language is spoken, however, it is normally only spoken in its pure form when reading a prepared text out loud and communication between speakers of different colloquial dialects. When speaking extemporaneously (i.e. making up the language on the spot, as in a normal discussion among people), speakers tend to deviate somewhat from the strict literary language in the direction of the colloquial varieties. In fact, there is a continuous range of "in-between" spoken varieties: from nearly pure Modern Standard Arabic (MSA), to a form that still uses MSA grammar and vocabulary but with significant colloquial influence, to a form of the colloquial language that imports a number of words and grammatical constructions in MSA, to a form that is close to pure colloquial but with the "rough edges" (the most noticeably "vulgar" or non-Classical aspects) smoothed out, to pure colloquial. The particular variant (or register) used depends on the social class and education level of the speakers involved and the level of formality of the speech situation. Often it will vary within a single encounter, e.g., moving from nearly pure MSA to a more mixed language in the process of a radio interview, as the interviewee becomes more comfortable with the interviewer. This type of variation is characteristic of the diglossia that exists throughout the Arabic-speaking world. Although Modern Standard Arabic (MSA) is a unitary language, its pronunciation varies somewhat from country to country and from region to region within a country. The variation in individual "accents" of MSA speakers tends to mirror corresponding variations in the colloquial speech of the speakers in question, but with the distinguishing characteristics moderated somewhat. It is important in descriptions of "Arabic" phonology to distinguish between pronunciation of a given colloquial (spoken) dialect and the pronunciation of MSA by these same speakers. Although they are related, they are not the same. For example, the phoneme that derives from Classical Arabic has many different pronunciations in the modern spoken varieties, e.g., including the proposed original . Speakers whose native variety has either or will use the same pronunciation when speaking MSA. Even speakers from Cairo, whose native Egyptian Arabic has , normally use when speaking MSA. The of Persian Gulf speakers is the only variant pronunciation which isn't found in MSA; is used instead, but may use [j] in MSA for comfortable pronunciation. Another reason of different pronunciations is influence of colloquial dialects. The differentiation of pronunciation of colloquial dialects is the influence from other languages previously spoken and some still presently spoken in the regions, such as Coptic in Egypt, Berber, Punic, or Phoenician in North Africa, Himyaritic, Modern South Arabian, and Old South Arabian in Yemen and Oman, and Aramaic and Canaanite languages (including Phoenician) in the Levant and Mesopotamia. Another example: Many colloquial varieties are known for a type of vowel harmony in which the presence of an "emphatic consonant" triggers backed allophones of nearby vowels (especially of the low vowels , which are backed to in these circumstances and very often fronted to in all other circumstances). In many spoken varieties, the backed or "emphatic" vowel allophones spread a fair distance in both directions from the triggering consonant; in some varieties (most notably Egyptian Arabic), the "emphatic" allophones spread throughout the entire word, usually including prefixes and suffixes, even at a distance of several syllables from the triggering consonant. Speakers of colloquial varieties with this vowel harmony tend to introduce it into their MSA pronunciation as well, but usually with a lesser degree of spreading than in the colloquial varieties. (For example, speakers of colloquial varieties with extremely long-distance harmony may allow a moderate, but not extreme, amount of spreading of the harmonic allophones in their MSA speech, while speakers of colloquial varieties with moderate-distance harmony may only harmonize immediately adjacent vowels in MSA.) Vowels Modern Standard Arabic has six pure vowels (while most modern dialects have eight pure vowels which includes the long vowels ), with short and corresponding long vowels . There are also two diphthongs: and . The pronunciation of the vowels differs from speaker to speaker, in a way that tends to reflect the pronunciation of the corresponding colloquial variety. Nonetheless, there are some common trends. Most noticeable is the differing pronunciation of and , which tend towards fronted , or in most situations, but a back in the neighborhood of emphatic consonants. Some accents and dialects, such as those of the Hejaz region, have an open or a central in all situations. The vowel varies towards too. Listen to the final vowel in the recording of at the beginning of this article, for example. The point is, Arabic has only three short vowel phonemes, so those phonemes can have a very wide range of allophones. The vowels and are often affected somewhat in emphatic neighborhoods as well, with generally more back or centralized allophones, but the differences are less great than for the low vowels. The pronunciation of short and tends towards and , respectively, in many dialects. The definition of both "emphatic" and "neighborhood" vary in ways that reflect (to some extent) corresponding variations in the spoken dialects. Generally, the consonants triggering "emphatic" allophones are the pharyngealized consonants ; ; and , if not followed immediately by . Frequently, the fricatives also trigger emphatic allophones; occasionally also the pharyngeal consonants (the former more than the latter). Many dialects have multiple emphatic allophones of each vowel, depending on the particular nearby consonants. In most MSA accents, emphatic coloring of vowels is limited to vowels immediately adjacent to a triggering consonant, although in some it spreads a bit farther: e.g., 'time'; 'homeland'; 'downtown' (sometimes or similar). In a non-emphatic environment, the vowel in the diphthong is pronounced or : hence 'sword' but 'summer'. However, in accents with no emphatic allophones of (e.g., in the Hejaz), the pronunciation or occurs in all situations. Consonants The phoneme is represented by the Arabic letter () and has many standard pronunciations. is characteristic of north Algeria, Iraq, and most of the Arabian peninsula but with an allophonic in some positions; occurs in most of the Levant and most of North Africa; and is used in most of Egypt and some regions in Yemen and Oman. Generally this corresponds with the pronunciation in the colloquial dialects. In some regions in Sudan and Yemen, as well as in some Sudanese and Yemeni dialects, it may be either or , representing the original pronunciation of Classical Arabic. Foreign words containing may be transcribed with , , , , , or , mainly depending on the regional spoken variety of Arabic or the commonly diacriticized Arabic letter. In northern Egypt, where the Arabic letter () is normally pronounced , a separate phoneme , which may be transcribed with , occurs in a small number of mostly non-Arabic loanwords, e.g., 'jacket'. () can be pronounced as . In some places of Maghreb it can be also pronounced as . and () are velar, post-velar, or uvular. In many varieties, () are epiglottal in Western Asia. is pronounced as velarized in الله , the name of God, q.e. Allah, when the word follows a, ā, u or ū (after i or ī it is unvelarized: bismi l–lāh ). Some speakers velarize other occurrences of in MSA, in imitation of their spoken dialects. The emphatic consonant was actually pronounced , or possibly —either way, a highly unusual sound. The medieval Arabs actually termed their language 'the language of the Ḍād' (the name of the letter used for this sound), since they thought the sound was unique to their language. (In fact, it also exists in a few other minority Semitic languages, e.g., Mehri.) Arabic has consonants traditionally termed "emphatic" (), which exhibit simultaneous pharyngealization as well as varying degrees of velarization (depending on the region), so they may be written with the "Velarized or pharyngealized" diacritic () as: . This simultaneous articulation is described as "Retracted Tongue Root" by phonologists. In some transcription systems, emphasis is shown by capitalizing the letter, for example, is written ; in others the letter is underlined or has a dot below it, for example, . Vowels and consonants can be phonologically short or long. Long (geminate) consonants are normally written doubled in Latin transcription (i.e. bb, dd, etc.), reflecting the presence of the Arabic diacritic mark , which indicates doubled consonants. In actual pronunciation, doubled consonants are held twice as long as short consonants. This consonant lengthening is phonemically contrastive: 'he accepted' vs. 'he kissed'. Syllable structure Arabic has two kinds of syllables: open syllables (CV) and (CVV)—and closed syllables (CVC), (CVVC) and (CVCC). The syllable types with two morae (units of time), i.e. CVC and CVV, are termed heavy syllables, while those with three morae, i.e. CVVC and CVCC, are superheavy syllables. Superheavy syllables in Classical Arabic occur in only two places: at the end of the sentence (due to pausal pronunciation) and in words such as 'hot', 'stuff, substance', 'they disputed with each other', where a long occurs before two identical consonants (a former short vowel between the consonants has been lost). (In less formal pronunciations of Modern Standard Arabic, superheavy syllables are common at the end of words or before clitic suffixes such as 'us, our', due to the deletion of final short vowels.) In surface pronunciation, every vowel must be preceded by a consonant (which may include the glottal stop ). There are no cases of hiatus within a word (where two vowels occur next to each other, without an intervening consonant). Some words do have an underlying vowel at the beginning, such as the definite article al- or words such as 'he bought', 'meeting'. When actually pronounced, one of three things happens: If the word occurs after another word ending in a consonant, there is a smooth transition from final consonant to initial vowel, e.g., 'meeting' . If the word occurs after another word ending in a vowel, the initial vowel of the word is elided, e.g., 'house of the director' . If the word occurs at the beginning of an utterance, a glottal stop is added onto the beginning, e.g., 'The house is ...' . Stress Word stress is not phonemically contrastive in Standard Arabic. It bears a strong relationship to vowel length. The basic rules for Modern Standard Arabic are: A final vowel, long or short, may not be stressed. Only one of the last three syllables may be stressed. Given this restriction, the last heavy syllable (containing a long vowel or ending in a consonant) is stressed, if it is not the final syllable. If the final syllable is super heavy and closed (of the form CVVC or CVCC) it receives stress. If no syllable is heavy or super heavy, the first possible syllable (i.e. third from end) is stressed. As a special exception, in Form VII and VIII verb forms stress may not be on the first syllable, despite the above rules: Hence 'he subscribed' (whether or not the final short vowel is pronounced), 'he subscribes' (whether or not the final short vowel is pronounced), 'he should subscribe (juss.)'. Likewise Form VIII 'he bought', 'he buys'. Examples: 'book', 'writer', 'desk', 'desks', 'library' (but 'library' in short pronunciation), (Modern Standard Arabic) 'they wrote' = (dialect), (Modern Standard Arabic) 'they wrote it' = (dialect), (Modern Standard Arabic) 'they (dual, fem) wrote', (Modern Standard Arabic) 'I wrote' = (short form or dialect). Doubled consonants count as two consonants: 'magazine', "place". These rules may result in differently stressed syllables when final case endings are pronounced, vs. the normal situation where they are not pronounced, as in the above example of 'library' in full pronunciation, but 'library' in short pronunciation. The restriction on final long vowels does not apply to the spoken dialects, where original final long vowels have been shortened and secondary final long vowels have arisen from loss of original final -hu/hi. Some dialects have different stress rules. In the Cairo (Egyptian Arabic) dialect a heavy syllable may not carry stress more than two syllables from the end of a word, hence 'school', 'Cairo'. This also affects the way that Modern Standard Arabic is pronounced in Egypt. In the Arabic of Sanaa, stress is often retracted: 'two houses', 'their table', 'desks', 'sometimes', 'their school'. (In this dialect, only syllables with long vowels or diphthongs are considered heavy; in a two-syllable word, the final syllable can be stressed only if the preceding syllable is light; and in longer words, the final syllable cannot be stressed.) Levels of pronunciation The final short vowels (e.g., the case endings -a -i -u and mood endings -u -a) are often not pronounced in this language, despite forming part of the formal paradigm of nouns and verbs. The following levels of pronunciation exist: Full pronunciation with pausa This is the most formal level actually used in speech. All endings are pronounced as written, except at the end of an utterance, where the following changes occur: Final short vowels are not pronounced. (But possibly an exception is made for feminine plural -na and shortened vowels in the jussive/imperative of defective verbs, e.g., irmi! 'throw!'".) The entire indefinite noun endings -in and -un (with nunation) are left off. The ending -an is left off of nouns preceded by a tāʾ marbūṭah ة (i.e. the -t in the ending -at- that typically marks feminine nouns), but pronounced as -ā in other nouns (hence its writing in this fashion in the Arabic script). The tāʼ marbūṭah itself (typically of feminine nouns) is pronounced as h. (At least, this is the case in extremely formal pronunciation, e.g., some Quranic recitations. In practice, this h is usually omitted.) Formal short pronunciation This is a formal level of pronunciation sometimes seen. It is somewhat like pronouncing all words as if they were in pausal position (with influence from the colloquial varieties). The following changes occur: Most final short vowels are not pronounced. However, the following short vowels are pronounced: feminine plural -na shortened vowels in the jussive/imperative of defective verbs, e.g., irmi! 'throw!' second-person singular feminine past-tense -ti and likewise anti 'you (fem. sg.)' sometimes, first-person singular past-tense -tu sometimes, second-person masculine past-tense -ta and likewise anta 'you (masc. sg.)' final -a in certain short words, e.g., laysa 'is not', sawfa (future-tense marker) The nunation endings -an -in -un are not pronounced. However, they are pronounced in adverbial accusative formations, e.g., تَقْرِيبًا 'almost, approximately', عَادَةً 'usually'. The tāʾ marbūṭah ending ة is unpronounced, except in construct state nouns, where it sounds as t (and in adverbial accusative constructions, e.g., عَادَةً 'usually', where the entire -tan is pronounced). The masculine singular nisbah ending is actually pronounced and is unstressed (but plural and feminine singular forms, i.e. when followed by a suffix, still sound as ). Full endings (including case endings) occur when a clitic object or possessive suffix is added (e.g., 'us/our'). Informal short pronunciation This is the pronunciation used by speakers of Modern Standard Arabic in extemporaneous speech, i.e. when producing new sentences rather than simply reading a prepared text. It is similar to formal short pronunciation except that the rules for dropping final vowels apply even when a clitic suffix is added. Basically, short-vowel case and mood endings are never pronounced and certain other changes occur that echo the corresponding colloquial pronunciations. Specifically: All the rules for formal short pronunciation apply, except as follows. The past tense singular endings written formally as -tu -ta -ti are pronounced -t -t -ti. But masculine is pronounced in full. Unlike in formal short pronunciation, the rules for dropping or modifying final endings are also applied when a clitic object or possessive suffix is added (e.g., 'us/our'). If this produces a sequence of three consonants, then one of the following happens, depending on the speaker's native colloquial variety: A short vowel (e.g., -i- or -ǝ-) is consistently added, either between the second and third or the first and second consonants. Or, a short vowel is added only if an otherwise unpronounceable sequence occurs, typically due to a violation of the sonority hierarchy (e.g., -rtn- is pronounced as a three-consonant cluster, but -trn- needs to be broken up). Or, a short vowel is never added, but consonants like r l m n occurring between two other consonants will be pronounced as a syllabic consonant (as in the English words "butter bottle bottom button"). When a doubled consonant occurs before another consonant (or finally), it is often shortened to a single consonant rather than a vowel added. (However, Moroccan Arabic never shortens doubled consonants or inserts short vowels to break up clusters, instead tolerating arbitrary-length series of arbitrary consonants and hence Moroccan Arabic speakers are likely to follow the same rules in their pronunciation of Modern Standard Arabic.) The clitic suffixes themselves tend also to be changed, in a way that avoids many possible occurrences of three-consonant clusters. In particular, -ka -ki -hu generally sound as -ak -ik -uh. Final long vowels are often shortened, merging with any short vowels that remain. Depending on the level of formality, the speaker's education level, etc., various grammatical changes may occur in ways that echo the colloquial variants: Any remaining case endings (e.g. masculine plural nominative -ūn vs. oblique -īn) will be leveled, with the oblique form used everywhere. (However, in words like 'father' and 'brother' with special long-vowel case endings in the construct state, the nominative is used everywhere, hence 'father of', 'brother of'.) Feminine plural endings in verbs and clitic suffixes will often drop out, with the masculine plural endings used instead. If the speaker's native variety has feminine plural endings, they may be preserved, but will often be modified in the direction of the forms used in the speaker's native variety, e.g. -an instead of -na. Dual endings will often drop out except on nouns and then used only for emphasis (similar to their use in the colloquial varieties); elsewhere, the plural endings are used (or feminine singular, if appropriate). Colloquial varieties Vowels As mentioned above, many spoken dialects have a process of emphasis spreading, where the "emphasis" (pharyngealization) of emphatic consonants spreads forward and back through adjacent syllables, pharyngealizing all nearby consonants and triggering the back allophone in all nearby low vowels. The extent of emphasis spreading varies. For example, in Moroccan Arabic, it spreads as far as the first full vowel (i.e. sound derived from a long vowel or diphthong) on either side; in many Levantine dialects, it spreads indefinitely, but is blocked by any or ; while in Egyptian Arabic, it usually spreads throughout the entire word, including prefixes and suffixes. In Moroccan Arabic, also have emphatic allophones and , respectively. Unstressed short vowels, especially , are deleted in many contexts. Many sporadic examples of short vowel change have occurred (especially → and interchange ↔). Most Levantine dialects merge short /i u/ into in most contexts (all except directly before a single final consonant). In Moroccan Arabic, on the other hand, short triggers labialization of nearby consonants (especially velar consonants and uvular consonants), and then short /a i u/ all merge into , which is deleted in many contexts. (The labialization plus is sometimes interpreted as an underlying phoneme .) This essentially causes the wholesale loss of the short-long vowel distinction, with the original long vowels remaining as half-long , phonemically , which are used to represent both short and long vowels in borrowings from Literary Arabic. Most spoken dialects have monophthongized original to in most circumstances, including adjacent to emphatic consonants, while keeping them as the original diphthongs in others e.g. . In most of the Moroccan, Algerian and Tunisian (except Sahel and Southeastern) Arabic dialects, they have subsequently merged into original . Consonants In most dialects, there may be more or fewer phonemes than those listed in the chart above. For example, is considered a native phoneme in most Arabic dialects except in Levantine dialects like Syrian or Lebanese where is pronounced and is pronounced . or () is considered a native phoneme in most dialects except in Egyptian and a number of Yemeni and Omani dialects where is pronounced . or and are distinguished in the dialects of Egypt, Sudan, the Levant and the Hejaz, but they have merged as in most dialects of the Arabian Peninsula, Iraq and Tunisia and have merged as in Morocco and Algeria. The usage of non-native and depends on the usage of each speaker but they might be more prevalent in some dialects than others. The Iraqi and Gulf Arabic also has the sound and writes it and with the Persian letters and , as in "plum"; "truffle". Early in the expansion of Arabic, the separate emphatic phonemes and coalesced into a single phoneme . Many dialects (such as Egyptian, Levantine, and much of the Maghreb) subsequently lost fricatives, converting into . Most dialects borrow "learned" words from the Standard language using the same pronunciation as for inherited words, but some dialects without interdental fricatives (particularly in Egypt and the Levant) render original in borrowed words as . Another key distinguishing mark of Arabic dialects is how they render the original velar and uvular plosives , (Proto-Semitic ), and : retains its original pronunciation in widely scattered regions such as Yemen, Morocco, and urban areas of the Maghreb. It is pronounced as a glottal stop in several prestige dialects, such as those spoken in Cairo, Beirut and Damascus. But it is rendered as a voiced velar plosive in Persian Gulf, Upper Egypt, parts of the Maghreb, and less urban parts of the Levant (e.g. Jordan). In Iraqi Arabic it sometimes retains its original pronunciation and is sometimes rendered as a voiced velar plosive, depending on the word. Some traditionally Christian villages in rural areas of the Levant render the sound as , as do Shiʻi Bahrainis. In some Gulf dialects, it is palatalized to or . It is pronounced as a voiced uvular constrictive in Sudanese Arabic. Many dialects with a modified pronunciation for maintain the pronunciation in certain words (often with religious or educational overtones) borrowed from the Classical language. is pronounced as an affricate in Iraq and much of the Arabian Peninsula but is pronounced in most of North Egypt and parts of Yemen and Oman, in Morocco, Tunisia, and the Levant, and , in most words in much of the Persian Gulf. usually retains its original pronunciation but is palatalized to in many words in Israel and the Palestinian Territories, Iraq, and countries in the eastern part of the Arabian Peninsula. Often a distinction is made between the suffixes ('you', masc.) and ('you', fem.), which become and , respectively. In Sana'a, Omani, and Bahrani is pronounced . Pharyngealization of the emphatic consonants tends to weaken in many of the spoken varieties, and to spread from emphatic consonants to nearby sounds. In addition, the "emphatic" allophone automatically triggers pharyngealization of adjacent sounds in many dialects. As a result, it may difficult or impossible to determine whether a given coronal consonant is phonemically emphatic or not, especially in dialects with long-distance emphasis spreading. (A notable exception is the sounds vs. in Moroccan Arabic, because the former is pronounced as an affricate but the latter is not.) Grammar Literary Arabic As in other Semitic languages, Arabic has a complex and unusual morphology (i.e. method of constructing words from a basic root). Arabic has a nonconcatenative "root-and-pattern" morphology: A root consists of a set of bare consonants (usually three), which are fitted into a discontinuous pattern to form words. For example, the word for 'I wrote' is constructed by combining the root 'write' with the pattern 'I Xed' to form 'I wrote'. Other verbs meaning 'I Xed' will typically have the same pattern but with different consonants, e.g. 'I read', 'I ate', 'I went', although other patterns are possible (e.g. 'I drank', 'I said', 'I spoke', where the subpattern used to signal the past tense may change but the suffix is always used). From a single root , numerous words can be formed by applying different patterns: كَتَبْتُ 'I wrote' كَتَّبْتُ 'I had (something) written' كَاتَبْتُ 'I corresponded (with someone)' أَكْتَبْتُ 'I dictated' اِكْتَتَبْتُ 'I subscribed' تَكَاتَبْنَا 'we corresponded with each other' أَكْتُبُ 'I write' أُكَتِّبُ 'I have (something) written' أُكَاتِبُ 'I correspond (with someone)' أُكْتِبُ 'I dictate' أَكْتَتِبُ 'I subscribe' نَتَكَتِبُ 'we correspond each other' كُتِبَ 'it was written' أُكْتِبَ 'it was dictated' مَكْتُوبٌ 'written' مُكْتَبٌ 'dictated' كِتَابٌ 'book' كُتُبٌ 'books' كَاتِبٌ 'writer' كُتَّابٌ 'writers' مَكْتَبٌ 'desk, office' مَكْتَبَةٌ 'library, bookshop' etc. Nouns and adjectives Nouns in Literary Arabic have three grammatical cases (nominative, accusative, and genitive [also used when the noun is governed by a preposition]); three numbers (singular, dual and plural); two genders (masculine and feminine); and three "states" (indefinite, definite, and construct). The cases of singular nouns (other than those that end in long ā) are indicated by suffixed short vowels (/-u/ for nominative, /-a/ for accusative, /-i/ for genitive). The feminine singular is often marked by ـَة /-at/, which is pronounced as /-ah/ before a pause. Plural is indicated either through endings (the sound plural) or internal modification (the broken plural). Definite nouns include all proper nouns, all nouns in "construct state" and all nouns which are prefixed by the definite article اَلْـ /al-/. Indefinite singular nouns (other than those that end in long ā) add a final /-n/ to the case-marking vowels, giving /-un/, /-an/ or /-in/ (which is also referred to as nunation or tanwīn). Adjectives in Literary Arabic are marked for case, number, gender and state, as for nouns. However, the plural of all non-human nouns is always combined with a singular feminine adjective, which takes the ـَة /-at/ suffix. Pronouns in Literary Arabic are marked for person, number and gender. There are two varieties, independent pronouns and enclitics. Enclitic pronouns are attached to the end of a verb, noun or preposition and indicate verbal and prepositional objects or possession of nouns. The first-person singular pronoun has a different enclitic form used for verbs (ـنِي /-nī/) and for nouns or prepositions (ـِي /-ī/ after consonants, ـيَ /-ya/ after vowels). Nouns, verbs, pronouns and adjectives agree with each other in all respects. However, non-human plural nouns are grammatically considered to be feminine singular. Furthermore, a verb in a verb-initial sentence is marked as singular regardless of its semantic number when the subject of the verb is explicitly mentioned as a noun. Numerals between three and ten show "chiasmic" agreement, in that grammatically masculine numerals have feminine marking and vice versa. Verbs Verbs in Literary Arabic are marked for person (first, second, or third), gender, and number. They are conjugated in two major paradigms (past and non-past); two voices (active and passive); and six moods (indicative, imperative, subjunctive, jussive, shorter energetic and longer energetic), the fifth and sixth moods, the energetics, exist only in Classical Arabic but not in MSA. There are also two participles (active and passive) and a verbal noun, but no infinitive. The past and non-past paradigms are sometimes also termed perfective and imperfective, indicating the fact that they actually represent a combination of tense and aspect. The moods other than the indicative occur only in the non-past, and the future tense is signaled by prefixing سَـ or سَوْفَ onto the non-past. The past and non-past differ in the form of the stem (e.g., past كَتَبـ vs. non-past ـكْتُبـ ), and also use completely different sets of affixes for indicating person, number and gender: In the past, the person, number and gender are fused into a single suffixal morpheme, while in the non-past, a combination of prefixes (primarily encoding person) and suffixes (primarily encoding gender and number) are used. The passive voice uses the same person/number/gender affixes but changes the vowels of the stem. The following shows a paradigm of a regular Arabic verb, كَتَبَ 'to write'. In Modern Standard, the energetic mood (in either long or short form, which have the same meaning) is almost never used. Derivation Like other Semitic languages, and unlike most other languages, Arabic makes much more use of nonconcatenative morphology (applying many templates applied roots) to derive words than adding prefixes or suffixes to words. For verbs, a given root can occur in many different derived verb stems (of which there are about fifteen), each with one or more characteristic meanings and each with its own templates for the past and non-past stems, active and passive participles, and verbal noun. These are referred to by Western scholars as "Form I", "Form II", and so on through "Form XV" (although Forms XI to XV are rare). These stems encode grammatical functions such as the causative, intensive and reflexive. Stems sharing the same root consonants represent separate verbs, albeit often semantically related, and each is the basis for its own conjugational paradigm. As a result, these derived stems are part of the system of derivational morphology, not part of the inflectional system. Examples of the different verbs formed from the root كتب 'write' (using حمر 'red' for Form IX, which is limited to colors and physical defects): Form II is sometimes used to create transitive denominative verbs (verbs built from nouns); Form V is the equivalent used for intransitive denominatives. The associated participles and verbal nouns of a verb are the primary means of forming new lexical nouns in Arabic. This is similar to the process by which, for example, the English gerund "meeting" (similar to a verbal noun) has turned into a noun referring to a particular type of social, often work-related event where people gather together to have a "discussion" (another lexicalized verbal noun). Another fairly common means of forming nouns is through one of a limited number of patterns that can be applied directly to roots, such as the "nouns of location" in ma- (e.g. 'desk, office' < 'write', 'kitchen' < 'cook'). The only three genuine suffixes are as follows: The feminine suffix -ah; variously derives terms for women from related terms for men, or more generally terms along the same lines as the corresponding masculine, e.g. 'library' (also a writing-related place, but different from , as above). The nisbah suffix -iyy-. This suffix is extremely productive, and forms adjectives meaning "related to X". It corresponds to English adjectives in -ic, -al, -an, -y, -ist, etc. The feminine nisbah suffix -iyyah. This is formed by adding the feminine suffix -ah onto nisba adjectives to form abstract nouns. For example, from the basic root 'share' can be derived the Form VIII verb 'to cooperate, participate', and in turn its verbal noun 'cooperation, participation' can be formed. This in turn can be made into a nisbah adjective 'socialist', from which an abstract noun 'socialism' can be derived. Other recent formations are 'republic' (lit. "public-ness", < 'multitude, general public'), and the Gaddafi-specific variation 'people's republic' (lit. "masses-ness", < 'the masses', pl. of , as above). Colloquial varieties The spoken dialects have lost the case distinctions and make only limited use of the dual (it occurs only on nouns and its use is no longer required in all circumstances). They have lost the mood distinctions other than imperative, but many have since gained new moods through the use of prefixes (most often /bi-/ for indicative vs. unmarked subjunctive). They have also mostly lost the indefinite "nunation" and the internal passive. The following is an example of a regular verb paradigm in Egyptian Arabic. Writing system The Arabic alphabet derives from the Aramaic through Nabatean, to which it bears a loose resemblance like that of Coptic or Cyrillic scripts to Greek script. Traditionally, there were several differences between the Western (North African) and Middle Eastern versions of the alphabet—in particular, the faʼ had a dot underneath and qaf a single dot above in the Maghreb, and the order of the letters was slightly different (at least when they were used as numerals). However, the old Maghrebi variant has been abandoned except for calligraphic purposes in the Maghreb itself, and remains in use mainly in the Quranic schools (zaouias) of West Africa. Arabic, like all other Semitic languages (except for the Latin-written Maltese, and the languages with the Ge'ez script), is written from right to left. There are several styles of scripts such as thuluth, muhaqqaq, tawqi, rayhan and notably naskh, which is used in print and by computers, and ruqʻah, which is commonly used for correspondence. Originally Arabic was made up of only rasm without diacritical marks Later diacritical points (which in Arabic are referred to as nuqaṯ) were added (which allowed readers to distinguish between letters such as b, t, th, n and y). Finally signs known as Tashkil were used for short vowels known as harakat and other uses such as final postnasalized or long vowels. Calligraphy After Khalil ibn Ahmad al Farahidi finally fixed the Arabic script around 786, many styles were developed, both for the writing down of the Quran and other books, and for inscriptions on monuments as decoration. Arabic calligraphy has not fallen out of use as calligraphy has in the Western world, and is still considered by Arabs as a major art form; calligraphers are held in great esteem. Being cursive by nature, unlike the Latin script, Arabic script is used to write down a verse of the Quran, a hadith, or simply a proverb. The composition is often abstract, but sometimes the writing is shaped into an actual form such as that of an animal. One of the current masters of the genre is Hassan Massoudy. In modern times the intrinsically calligraphic nature of the written Arabic form is haunted by the thought that a typographic approach to the language, necessary for digitized unification, will not always accurately maintain meanings conveyed through calligraphy. Romanization There are a number of different standards for the romanization of Arabic, i.e. methods of accurately and efficiently representing Arabic with the Latin script. There are various conflicting motivations involved, which leads to multiple systems. Some are interested in transliteration, i.e. representing the spelling of Arabic, while others focus on transcription, i.e. representing the pronunciation of Arabic. (They differ in that, for example, the same letter is used to represent both a consonant, as in "you" or "yet", and a vowel, as in "me" or "eat".) Some systems, e.g. for scholarly use, are intended to accurately and unambiguously represent the phonemes of Arabic, generally making the phonetics more explicit than the original word in the Arabic script. These systems are heavily reliant on diacritical marks such as "š" for the sound equivalently written sh in English. Other systems (e.g. the Bahá'í orthography) are intended to help readers who are neither Arabic speakers nor linguists with intuitive pronunciation of Arabic names and phrases. These less "scientific" systems tend to avoid diacritics and use digraphs (like sh and kh). These are usually simpler to read, but sacrifice the definiteness of the scientific systems, and may lead to ambiguities, e.g. whether to interpret sh as a single sound, as in gash, or a combination of two sounds, as in gashouse. The ALA-LC romanization solves this problem by separating the two sounds with a prime symbol ( ′ ); e.g., as′hal 'easier'. During the last few decades and especially since the 1990s, Western-invented text communication technologies have become prevalent in the Arab world, such as personal computers, the World Wide Web, email, bulletin board systems, IRC, instant messaging and mobile phone text messaging. Most of these technologies originally had the ability to communicate using the Latin script only, and some of them still do not have the Arabic script as an optional feature. As a result, Arabic speaking users communicated in these technologies by transliterating the Arabic text using the Latin script, sometimes known as IM Arabic. To handle those Arabic letters that cannot be accurately represented using the Latin script, numerals and other characters were appropriated. For example, the numeral "3" may be used to represent the Arabic letter . There is no universal name for this type of transliteration, but some have named it Arabic Chat Alphabet. Other systems of transliteration exist, such as using dots or capitalization to represent the "emphatic" counterparts of certain consonants. For instance, using capitalization, the letter , may be represented by d. Its emphatic counterpart, , may be written as D. Numerals In most of present-day North Africa, the Western Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) are used. However, in Egypt and Arabic-speaking countries to the east of it, the Eastern Arabic numerals ( – – – – – – – – – ) are in use. When representing a number in Arabic, the lowest-valued position is placed on the right, so the order of positions is the same as in left-to-right scripts. Sequences of digits such as telephone numbers are read from left to right, but numbers are spoken in the traditional Arabic fashion, with units and tens reversed from the modern English usage. For example, 24 is said "four and twenty" just like in the German language (vierundzwanzig) and Classical Hebrew, and 1975 is said "a thousand and nine-hundred and five and seventy" or, more eloquently, "a thousand and nine-hundred five seventy" Language-standards regulators Academy of the Arabic Language is the name of a number of language-regulation bodies formed in the Arab League. The most active are in Damascus and Cairo. They review language development, monitor new words and approve inclusion of new words into their published standard dictionaries. They also publish old and historical Arabic manuscripts. As a foreign language Arabic has been taught worldwide in many elementary and secondary schools, especially Muslim schools. Universities around the world have classes that teach Arabic as part of their foreign languages, Middle Eastern studies, and religious studies courses. Arabic language schools exist to assist students to learn Arabic outside the academic world. There are many Arabic language schools in the Arab world and other Muslim countries. Because the Quran is written in Arabic and all Islamic terms are in Arabic, millions of Muslims (both Arab and non-Arab) study the language. Software and books with tapes are also important part of Arabic learning, as many of Arabic learners may live in places where there are no academic or Arabic language school classes available. Radio series of Arabic language classes are also provided from some radio stations. A number of websites on the Internet provide online classes for all levels as a means of distance education; most teach Modern Standard Arabic, but some teach regional varieties from numerous countries. Status in the Arab world vs. other languages With the sole example of Medieval linguist Abu Hayyan al-Gharnati – who, while a scholar of the Arabic language, was not ethnically Arab – Medieval scholars of the Arabic language made no efforts at studying comparative linguistics, considering all other languages inferior. In modern times, the educated upper classes in the Arab world have taken a nearly opposite view. Yasir Suleiman wrote in 2011 that "studying and knowing English or French in most of the Middle East and North Africa have become a badge of sophistication and modernity and ... feigning, or asserting, weakness or lack of facility in Arabic is sometimes paraded as a sign of status, class, and perversely, even education through a mélange of code-switching practises." See also Arabic Ontology Arabic diglossia Arabic influence on the Spanish language Arabic Language International Council Arabic literature Arabic–English Lexicon Arabist Dictionary of Modern Written Arabic Glossary of Islam International Association of Arabic Dialectology List of Arab newspapers List of Arabic-language television channels List of Arabic given names List of arabophones List of countries where Arabic is an official language List of French words of Arabic origin List of replaced loanwords in Turkish References Citations Sources Suileman, Yasir. Arabic, Self and Identity: A Study in Conflict and Displacement. Oxford University Press, 2011. . External links Dr. Nizar Habash's, Columbia University, Introduction to Arabic Natural Language Processing Google Ta3reeb – Google Transliteration Transliteration Arabic language pronunciation applet Alexis Neme (2011), A lexicon of Arabic verbs constructed on the basis of Semitic taxonomy and using finite-state transducers Alexis Neme and Eric Laporte (2013), Pattern-and-root inflectional morphology: the Arabic broken plural Alexis Neme and Eric Laporte (2015), Do computer scientists deeply understand Arabic morphology? – , available also in Arabic, Indonesian, French Arabic manuscripts, UA 5572 at L. Tom Perry Special Collections, Brigham Young University Online Arabic Keyboard (Bilingual dictionary) Arabic Student's Dictionary Languages attested from the 9th century BC Articles containing video clips Central Semitic languages Fusional languages Languages of Algeria Languages of Bahrain Languages of Cameroon Languages of Chad Languages of the Comoros Languages of Djibouti Languages of Eritrea Languages of Gibraltar Languages of Israel Languages of Iran Languages of Iraq Languages of Jordan Languages of Kurdistan Languages of Kuwait Languages of Lebanon Languages of Libya Languages of Mali Languages of Mauritania Languages of Morocco Languages of Niger Languages of Oman Languages of the State of Palestine Languages of Qatar Languages of Saudi Arabia Languages of Senegal Languages of South Sudan Languages of Sicily Languages of Somalia Languages of Sudan Languages of Syria Languages of the United Arab Emirates Languages of Tunisia Languages of Yemen Stress-timed languages Subject–verb–object languages Verb–subject–object languages

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

840

https://en.wikipedia.org/wiki/Axiom%20of%20choice

Axiom of choice

In mathematics, the axiom of choice, or AC, is an axiom of set theory equivalent to the statement that a Cartesian product of a collection of non-empty sets is non-empty. Informally put, the axiom of choice says that given any collection of bins, each containing at least one object, it is possible to make a selection of exactly one object from each bin, even if the collection is infinite. Formally, it states that for every indexed family of nonempty sets there exists an indexed family of elements such that for every . The axiom of choice was formulated in 1904 by Ernst Zermelo in order to formalize his proof of the well-ordering theorem. In many cases, such a selection can be made without invoking the axiom of choice; this is in particular the case if the number of sets is finite, or if a selection rule is available – some distinguishing property that happens to hold for exactly one element in each set. An illustrative example is sets picked from the natural numbers. From such sets, one may always select the smallest number, e.g. given the sets {{4, 5, 6}, {10, 12}, {1, 400, 617, 8000}} the set containing each smallest element is {4, 10, 1}. In this case, "select the smallest number" is a choice function. Even if infinitely many sets were collected from the natural numbers, it will always be possible to choose the smallest element from each set to produce a set. That is, the choice function provides the set of chosen elements. However, no choice function is known for the collection of all non-empty subsets of the real numbers (if there are non-constructible reals). In that case, the axiom of choice must be invoked. Bertrand Russell coined an analogy: for any (even infinite) collection of pairs of shoes, one can pick out the left shoe from each pair to obtain an appropriate selection; this makes it possible to directly define a choice function. For an infinite collection of pairs of socks (assumed to have no distinguishing features), there is no obvious way to make a function that selects one sock from each pair, without invoking the axiom of choice. Although originally controversial, the axiom of choice is now used without reservation by most mathematicians, and it is included in the standard form of axiomatic set theory, Zermelo–Fraenkel set theory with the axiom of choice (ZFC). One motivation for this use is that a number of generally accepted mathematical results, such as Tychonoff's theorem, require the axiom of choice for their proofs. Contemporary set theorists also study axioms that are not compatible with the axiom of choice, such as the axiom of determinacy. The axiom of choice is avoided in some varieties of constructive mathematics, although there are varieties of constructive mathematics in which the axiom of choice is embraced. Statement A choice function (also called selector or selection) is a function f, defined on a collection X of nonempty sets, such that for every set A in X, f(A) is an element of A. With this concept, the axiom can be stated: Formally, this may be expressed as follows: Thus, the negation of the axiom of choice states that there exists a collection of nonempty sets that has no choice function. (, so where is negation.) Each choice function on a collection X of nonempty sets is an element of the Cartesian product of the sets in X. This is not the most general situation of a Cartesian product of a family of sets, where a given set can occur more than once as a factor; however, one can focus on elements of such a product that select the same element every time a given set appears as factor, and such elements correspond to an element of the Cartesian product of all distinct sets in the family. The axiom of choice asserts the existence of such elements; it is therefore equivalent to: Given any family of nonempty sets, their Cartesian product is a nonempty set. Nomenclature ZF, AC, and ZFC In this article and other discussions of the Axiom of Choice the following abbreviations are common: AC – the Axiom of Choice. ZF – Zermelo–Fraenkel set theory omitting the Axiom of Choice. ZFC – Zermelo–Fraenkel set theory, extended to include the Axiom of Choice. Variants There are many other equivalent statements of the axiom of choice. These are equivalent in the sense that, in the presence of other basic axioms of set theory, they imply the axiom of choice and are implied by it. One variation avoids the use of choice functions by, in effect, replacing each choice function with its range. Given any set X of pairwise disjoint non-empty sets, there exists at least one set C that contains exactly one element in common with each of the sets in X. This guarantees for any partition of a set X the existence of a subset C of X containing exactly one element from each part of the partition. Another equivalent axiom only considers collections X that are essentially powersets of other sets: For any set A, the power set of A (with the empty set removed) has a choice function. Authors who use this formulation often speak of the choice function on A, but this is a slightly different notion of choice function. Its domain is the power set of A (with the empty set removed), and so makes sense for any set A, whereas with the definition used elsewhere in this article, the domain of a choice function on a collection of sets is that collection, and so only makes sense for sets of sets. With this alternate notion of choice function, the axiom of choice can be compactly stated as Every set has a choice function. which is equivalent to For any set A there is a function f such that for any non-empty subset B of A, f(B) lies in B. The negation of the axiom can thus be expressed as: There is a set A such that for all functions f (on the set of non-empty subsets of A), there is a B such that f(B) does not lie in B. Restriction to finite sets The statement of the axiom of choice does not specify whether the collection of nonempty sets is finite or infinite, and thus implies that every finite collection of nonempty sets has a choice function. However, that particular case is a theorem of the Zermelo–Fraenkel set theory without the axiom of choice (ZF); it is easily proved by mathematical induction. In the even simpler case of a collection of one set, a choice function just corresponds to an element, so this instance of the axiom of choice says that every nonempty set has an element; this holds trivially. The axiom of choice can be seen as asserting the generalization of this property, already evident for finite collections, to arbitrary collections. Usage Until the late 19th century, the axiom of choice was often used implicitly, although it had not yet been formally stated. For example, after having established that the set X contains only non-empty sets, a mathematician might have said "let F(s) be one of the members of s for all s in X" to define a function F. In general, it is impossible to prove that F exists without the axiom of choice, but this seems to have gone unnoticed until Zermelo. Not every situation requires the axiom of choice. For finite sets X, the axiom of choice follows from the other axioms of set theory. In that case, it is equivalent to saying that if we have several (a finite number of) boxes, each containing at least one item, then we can choose exactly one item from each box. Clearly, we can do this: We start at the first box, choose an item; go to the second box, choose an item; and so on. The number of boxes is finite, so eventually, our choice procedure comes to an end. The result is an explicit choice function: a function that takes the first box to the first element we chose, the second box to the second element we chose, and so on. (A formal proof for all finite sets would use the principle of mathematical induction to prove "for every natural number k, every family of k nonempty sets has a choice function.") This method cannot, however, be used to show that every countable family of nonempty sets has a choice function, as is asserted by the axiom of countable choice. If the method is applied to an infinite sequence (Xi : i∈ω) of nonempty sets, a function is obtained at each finite stage, but there is no stage at which a choice function for the entire family is constructed, and no "limiting" choice function can be constructed, in general, in ZF without the axiom of choice. Examples The nature of the individual nonempty sets in the collection may make it possible to avoid the axiom of choice even for certain infinite collections. For example, suppose that each member of the collection X is a nonempty subset of the natural numbers. Every such subset has a smallest element, so to specify our choice function we can simply say that it maps each set to the least element of that set. This gives us a definite choice of an element from each set, and makes it unnecessary to apply the axiom of choice. The difficulty appears when there is no natural choice of elements from each set. If we cannot make explicit choices, how do we know that our set exists? For example, suppose that X is the set of all non-empty subsets of the real numbers. First we might try to proceed as if X were finite. If we try to choose an element from each set, then, because X is infinite, our choice procedure will never come to an end, and consequently, we shall never be able to produce a choice function for all of X. Next we might try specifying the least element from each set. But some subsets of the real numbers do not have least elements. For example, the open interval (0,1) does not have a least element: if x is in (0,1), then so is x/2, and x/2 is always strictly smaller than x. So this attempt also fails. Additionally, consider for instance the unit circle S, and the action on S by a group G consisting of all rational rotations. Namely, these are rotations by angles which are rational multiples of π. Here G is countable while S is uncountable. Hence S breaks up into uncountably many orbits under G. Using the axiom of choice, we could pick a single point from each orbit, obtaining an uncountable subset X of S with the property that all of its translates by G are disjoint from X. The set of those translates partitions the circle into a countable collection of disjoint sets, which are all pairwise congruent. Since X is not measurable for any rotation-invariant countably additive finite measure on S, finding an algorithm to select a point in each orbit requires the axiom of choice. See non-measurable set for more details. The reason that we are able to choose least elements from subsets of the natural numbers is the fact that the natural numbers are well-ordered: every nonempty subset of the natural numbers has a unique least element under the natural ordering. One might say, "Even though the usual ordering of the real numbers does not work, it may be possible to find a different ordering of the real numbers which is a well-ordering. Then our choice function can choose the least element of every set under our unusual ordering." The problem then becomes that of constructing a well-ordering, which turns out to require the axiom of choice for its existence; every set can be well-ordered if and only if the axiom of choice holds. Criticism and acceptance A proof requiring the axiom of choice may establish the existence of an object without explicitly defining the object in the language of set theory. For example, while the axiom of choice implies that there is a well-ordering of the real numbers, there are models of set theory with the axiom of choice in which no well-ordering of the reals is definable. Similarly, although a subset of the real numbers that is not Lebesgue measurable can be proved to exist using the axiom of choice, it is consistent that no such set is definable. The axiom of choice proves the existence of these intangibles (objects that are proved to exist, but which cannot be explicitly constructed), which may conflict with some philosophical principles. Because there is no canonical well-ordering of all sets, a construction that relies on a well-ordering may not produce a canonical result, even if a canonical result is desired (as is often the case in category theory). This has been used as an argument against the use of the axiom of choice. Another argument against the axiom of choice is that it implies the existence of objects that may seem counterintuitive. One example is the Banach–Tarski paradox which says that it is possible to decompose the 3-dimensional solid unit ball into finitely many pieces and, using only rotations and translations, reassemble the pieces into two solid balls each with the same volume as the original. The pieces in this decomposition, constructed using the axiom of choice, are non-measurable sets. Despite these seemingly paradoxical facts, most mathematicians accept the axiom of choice as a valid principle for proving new results in mathematics. The debate is interesting enough, however, that it is considered of note when a theorem in ZFC (ZF plus AC) is logically equivalent (with just the ZF axioms) to the axiom of choice, and mathematicians look for results that require the axiom of choice to be false, though this type of deduction is less common than the type which requires the axiom of choice to be true. It is possible to prove many theorems using neither the axiom of choice nor its negation; such statements will be true in any model of ZF, regardless of the truth or falsity of the axiom of choice in that particular model. The restriction to ZF renders any claim that relies on either the axiom of choice or its negation unprovable. For example, the Banach–Tarski paradox is neither provable nor disprovable from ZF alone: it is impossible to construct the required decomposition of the unit ball in ZF, but also impossible to prove there is no such decomposition. Similarly, all the statements listed below which require choice or some weaker version thereof for their proof are unprovable in ZF, but since each is provable in ZF plus the axiom of choice, there are models of ZF in which each statement is true. Statements such as the Banach–Tarski paradox can be rephrased as conditional statements, for example, "If AC holds, then the decomposition in the Banach–Tarski paradox exists." Such conditional statements are provable in ZF when the original statements are provable from ZF and the axiom of choice. In constructive mathematics As discussed above, in ZFC, the axiom of choice is able to provide "nonconstructive proofs" in which the existence of an object is proved although no explicit example is constructed. ZFC, however, is still formalized in classical logic. The axiom of choice has also been thoroughly studied in the context of constructive mathematics, where non-classical logic is employed. The status of the axiom of choice varies between different varieties of constructive mathematics. In Martin-Löf type theory and higher-order Heyting arithmetic, the appropriate statement of the axiom of choice is (depending on approach) included as an axiom or provable as a theorem. Errett Bishop argued that the axiom of choice was constructively acceptable, saying In constructive set theory, however, Diaconescu's theorem shows that the axiom of choice implies the law of excluded middle (unlike in Martin-Löf type theory, where it does not). Thus the axiom of choice is not generally available in constructive set theory. A cause for this difference is that the axiom of choice in type theory does not have the extensionality properties that the axiom of choice in constructive set theory does. Some results in constructive set theory use the axiom of countable choice or the axiom of dependent choice, which do not imply the law of the excluded middle in constructive set theory. Although the axiom of countable choice in particular is commonly used in constructive mathematics, its use has also been questioned. Independence In 1938, Kurt Gödel showed that the negation of the axiom of choice is not a theorem of ZF by constructing an inner model (the constructible universe) which satisfies ZFC and thus showing that ZFC is consistent if ZF itself is consistent. In 1963, Paul Cohen employed the technique of forcing, developed for this purpose, to show that, assuming ZF is consistent, the axiom of choice itself is not a theorem of ZF. He did this by constructing a much more complex model which satisfies ZF¬C (ZF with the negation of AC added as axiom) and thus showing that ZF¬C is consistent. Together these results establish that the axiom of choice is logically independent of ZF. The assumption that ZF is consistent is harmless because adding another axiom to an already inconsistent system cannot make the situation worse. Because of independence, the decision whether to use the axiom of choice (or its negation) in a proof cannot be made by appeal to other axioms of set theory. The decision must be made on other grounds. One argument given in favor of using the axiom of choice is that it is convenient to use it because it allows one to prove some simplifying propositions that otherwise could not be proved. Many theorems which are provable using choice are of an elegant general character: every ideal in a ring is contained in a maximal ideal, every vector space has a basis, and every product of compact spaces is compact. Without the axiom of choice, these theorems may not hold for mathematical objects of large cardinality. The proof of the independence result also shows that a wide class of mathematical statements, including all statements that can be phrased in the language of Peano arithmetic, are provable in ZF if and only if they are provable in ZFC. Statements in this class include the statement that P = NP, the Riemann hypothesis, and many other unsolved mathematical problems. When one attempts to solve problems in this class, it makes no difference whether ZF or ZFC is employed if the only question is the existence of a proof. It is possible, however, that there is a shorter proof of a theorem from ZFC than from ZF. The axiom of choice is not the only significant statement which is independent of ZF. For example, the generalized continuum hypothesis (GCH) is not only independent of ZF, but also independent of ZFC. However, ZF plus GCH implies AC, making GCH a strictly stronger claim than AC, even though they are both independent of ZF. Stronger axioms The axiom of constructibility and the generalized continuum hypothesis each imply the axiom of choice and so are strictly stronger than it. In class theories such as Von Neumann–Bernays–Gödel set theory and Morse–Kelley set theory, there is an axiom called the axiom of global choice that is stronger than the axiom of choice for sets because it also applies to proper classes. The axiom of global choice follows from the axiom of limitation of size. Tarski's axiom, which is used in Tarski–Grothendieck set theory and states (in the vernacular) that every set belongs to Grothendieck universe, is stronger than the axiom of choice. Equivalents There are important statements that, assuming the axioms of ZF but neither AC nor ¬AC, are equivalent to the axiom of choice. The most important among them are Zorn's lemma and the well-ordering theorem. In fact, Zermelo initially introduced the axiom of choice in order to formalize his proof of the well-ordering theorem. Set theory Well-ordering theorem: Every set can be well-ordered. Consequently, every cardinal has an initial ordinal. Tarski's theorem about choice: For every infinite set A, there is a bijective map between the sets A and A×A. Trichotomy: If two sets are given, then either they have the same cardinality, or one has a smaller cardinality than the other. Given two non-empty sets, one has a surjection to the other. The Cartesian product of any family of nonempty sets is nonempty. König's theorem: Colloquially, the sum of a sequence of cardinals is strictly less than the product of a sequence of larger cardinals. (The reason for the term "colloquially" is that the sum or product of a "sequence" of cardinals cannot be defined without some aspect of the axiom of choice.) Every surjective function has a right inverse. Order theory Zorn's lemma: Every non-empty partially ordered set in which every chain (i.e., totally ordered subset) has an upper bound contains at least one maximal element. Hausdorff maximal principle: In any partially ordered set, every totally ordered subset is contained in a maximal totally ordered subset. The restricted principle "Every partially ordered set has a maximal totally ordered subset" is also equivalent to AC over ZF. Tukey's lemma: Every non-empty collection of finite character has a maximal element with respect to inclusion. Antichain principle: Every partially ordered set has a maximal antichain. Abstract algebra Every vector space has a basis. Krull's theorem: Every unital ring other than the trivial ring contains a maximal ideal. For every non-empty set S there is a binary operation defined on S that gives it a group structure. (A cancellative binary operation is enough, see group structure and the axiom of choice.) Every free abelian group is projective. Baer's criterion: Every divisible abelian group is injective. Every set is a projective object in the category Set of sets. Functional analysis The closed unit ball of the dual of a normed vector space over the reals has an extreme point. Point-set topology Tychonoff's theorem: Every product of compact topological spaces is compact. In the product topology, the closure of a product of subsets is equal to the product of the closures. Mathematical logic If S is a set of sentences of first-order logic and B is a consistent subset of S, then B is included in a set that is maximal among consistent subsets of S. The special case where S is the set of all first-order sentences in a given signature is weaker, equivalent to the Boolean prime ideal theorem; see the section "Weaker forms" below. Graph theory Every connected graph has a spanning tree. Category theory There are several results in category theory which invoke the axiom of choice for their proof. These results might be weaker than, equivalent to, or stronger than the axiom of choice, depending on the strength of the technical foundations. For example, if one defines categories in terms of sets, that is, as sets of objects and morphisms (usually called a small category), or even locally small categories, whose hom-objects are sets, then there is no category of all sets, and so it is difficult for a category-theoretic formulation to apply to all sets. On the other hand, other foundational descriptions of category theory are considerably stronger, and an identical category-theoretic statement of choice may be stronger than the standard formulation, à la class theory, mentioned above. Examples of category-theoretic statements which require choice include: Every small category has a skeleton. If two small categories are weakly equivalent, then they are equivalent. Every continuous functor on a small-complete category which satisfies the appropriate solution set condition has a left-adjoint (the Freyd adjoint functor theorem). Weaker forms There are several weaker statements that are not equivalent to the axiom of choice, but are closely related. One example is the axiom of dependent choice (DC). A still weaker example is the axiom of countable choice (ACω or CC), which states that a choice function exists for any countable set of nonempty sets. These axioms are sufficient for many proofs in elementary mathematical analysis, and are consistent with some principles, such as the Lebesgue measurability of all sets of reals, that are disprovable from the full axiom of choice. Other choice axioms weaker than axiom of choice include the Boolean prime ideal theorem and the axiom of uniformization. The former is equivalent in ZF to Tarski's 1930 ultrafilter lemma: every filter is a subset of some ultrafilter. Results requiring AC (or weaker forms) but weaker than it One of the most interesting aspects of the axiom of choice is the large number of places in mathematics that it shows up. Here are some statements that require the axiom of choice in the sense that they are not provable from ZF but are provable from ZFC (ZF plus AC). Equivalently, these statements are true in all models of ZFC but false in some models of ZF. Set theory The ultrafilter lemma (with ZF) can be used to prove the Axiom of choice for finite sets: Given and a collection of non-empty sets, their product is not empty. Any union of countably many countable sets is itself countable (because it is necessary to choose a particular ordering for each of the countably many sets). If the set A is infinite, then there exists an injection from the natural numbers N to A (see Dedekind infinite). Eight definitions of a finite set are equivalent. Every infinite game in which is a Borel subset of Baire space is determined. Measure theory The Vitali theorem on the existence of non-measurable sets which states that there is a subset of the real numbers that is not Lebesgue measurable. The Hausdorff paradox. The Banach–Tarski paradox. Algebra Every field has an algebraic closure. Every field extension has a transcendence basis. Stone's representation theorem for Boolean algebras needs the Boolean prime ideal theorem. The Nielsen–Schreier theorem, that every subgroup of a free group is free. The additive groups of R and C are isomorphic. Functional analysis The Hahn–Banach theorem in functional analysis, allowing the extension of linear functionals The theorem that every Hilbert space has an orthonormal basis. The Banach–Alaoglu theorem about compactness of sets of functionals. The Baire category theorem about complete metric spaces, and its consequences, such as the open mapping theorem and the closed graph theorem. On every infinite-dimensional topological vector space there is a discontinuous linear map. General topology A uniform space is compact if and only if it is complete and totally bounded. Every Tychonoff space has a Stone–Čech compactification. Mathematical logic Gödel's completeness theorem for first-order logic: every consistent set of first-order sentences has a completion. That is, every consistent set of first-order sentences can be extended to a maximal consistent set. The compactness theorem: If is a set of first-order (or alternatively, zero-order) sentences such that every finite subset of has a model, then has a model. Possibly equivalent implications of AC There are several historically important set-theoretic statements implied by AC whose equivalence to AC is open. The partition principle, which was formulated before AC itself, was cited by Zermelo as a justification for believing AC. In 1906, Russell declared PP to be equivalent, but whether the partition principle implies AC is still the oldest open problem in set theory, and the equivalences of the other statements are similarly hard old open problems. In every known model of ZF where choice fails, these statements fail too, but it is unknown if they can hold without choice. Set theory Partition principle: if there is a surjection from A to B, there is an injection from B to A. Equivalently, every partition P of a set S is less than or equal to S in size. Converse Schröder–Bernstein theorem: if two sets have surjections to each other, they are equinumerous. Weak partition principle: A partition of a set S cannot be strictly larger than S. If WPP holds, this already implies the existence of a non-measurable set. Each of the previous three statements is implied by the preceding one, but it is unknown if any of these implications can be reversed. There is no infinite decreasing sequence of cardinals. The equivalence was conjectured by Schoenflies in 1905. Abstract algebra Hahn embedding theorem: Every ordered abelian group G order-embeds as a subgroup of the additive group endowed with a lexicographical order, where Ω is the set of Archimedean equivalence classes of G. This equivalence was conjectured by Hahn in 1907. Stronger forms of the negation of AC If we abbreviate by BP the claim that every set of real numbers has the property of Baire, then BP is stronger than ¬AC, which asserts the nonexistence of any choice function on perhaps only a single set of nonempty sets. Strengthened negations may be compatible with weakened forms of AC. For example, ZF + DC + BP is consistent, if ZF is. It is also consistent with ZF + DC that every set of reals is Lebesgue measurable; however, this consistency result, due to Robert M. Solovay, cannot be proved in ZFC itself, but requires a mild large cardinal assumption (the existence of an inaccessible cardinal). The much stronger axiom of determinacy, or AD, implies that every set of reals is Lebesgue measurable, has the property of Baire, and has the perfect set property (all three of these results are refuted by AC itself). ZF + DC + AD is consistent provided that a sufficiently strong large cardinal axiom is consistent (the existence of infinitely many Woodin cardinals). Quine's system of axiomatic set theory, "New Foundations" (NF), takes its name from the title ("New Foundations for Mathematical Logic") of the 1937 article which introduced it. In the NF axiomatic system, the axiom of choice can be disproved. Statements consistent with the negation of AC There are models of Zermelo-Fraenkel set theory in which the axiom of choice is false. We shall abbreviate "Zermelo-Fraenkel set theory plus the negation of the axiom of choice" by ZF¬C. For certain models of ZF¬C, it is possible to prove the negation of some standard facts. Any model of ZF¬C is also a model of ZF, so for each of the following statements, there exists a model of ZF in which that statement is true. In some model, there is a set that can be partitioned into strictly more equivalence classes than the original set has elements, and a function whose domain is strictly smaller than its range. In fact, this is the case in all known models. There is a function f from the real numbers to the real numbers such that f is not continuous at a, but f is sequentially continuous at a, i.e., for any sequence {xn} converging to a, limn f(xn)=f(a). In some model, there is an infinite set of real numbers without a countably infinite subset. In some model, the real numbers are a countable union of countable sets. This does not imply that the real numbers are countable: As pointed out above, to show that a countable union of countable sets is itself countable requires the Axiom of countable choice. In some model, there is a field with no algebraic closure. In all models of ZF¬C there is a vector space with no basis. In some model, there is a vector space with two bases of different cardinalities. In some model there is a free complete boolean algebra on countably many generators. In some model there is a set that cannot be linearly ordered. There exists a model of ZF¬C in which every set in Rn is measurable. Thus it is possible to exclude counterintuitive results like the Banach–Tarski paradox which are provable in ZFC. Furthermore, this is possible whilst assuming the Axiom of dependent choice, which is weaker than AC but sufficient to develop most of real analysis. In all models of ZF¬C, the generalized continuum hypothesis does not hold. For proofs, see . Additionally, by imposing definability conditions on sets (in the sense of descriptive set theory) one can often prove restricted versions of the axiom of choice from axioms incompatible with general choice. This appears, for example, in the Moschovakis coding lemma. Axiom of choice in type theory In type theory, a different kind of statement is known as the axiom of choice. This form begins with two types, σ and τ, and a relation R between objects of type σ and objects of type τ. The axiom of choice states that if for each x of type σ there exists a y of type τ such that R(x,y), then there is a function f from objects of type σ to objects of type τ such that R(x,f(x)) holds for all x of type σ: Unlike in set theory, the axiom of choice in type theory is typically stated as an axiom scheme, in which R varies over all formulas or over all formulas of a particular logical form. Quotes This is a joke: although the three are all mathematically equivalent, many mathematicians find the axiom of choice to be intuitive, the well-ordering principle to be counterintuitive, and Zorn's lemma to be too complex for any intuition. The observation here is that one can define a function to select from an infinite number of pairs of shoes by stating for example, to choose a left shoe. Without the axiom of choice, one cannot assert that such a function exists for pairs of socks, because left and right socks are (presumably) indistinguishable. Polish-American mathematician Jan Mycielski relates this anecdote in a 2006 article in the Notices of the AMS. This quote comes from the famous April Fools' Day article in the computer recreations column of the Scientific American, April 1989. Notes References Per Martin-Löf, "100 years of Zermelo's axiom of choice: What was the problem with it?", in Logicism, Intuitionism, and Formalism: What Has Become of Them?, Sten Lindström, Erik Palmgren, Krister Segerberg, and Viggo Stoltenberg-Hansen, editors (2008). , available as a Dover Publications reprint, 2013, . Herman Rubin, Jean E. Rubin: Equivalents of the axiom of choice. North Holland, 1963. Reissued by Elsevier, April 1970. . Herman Rubin, Jean E. Rubin: Equivalents of the Axiom of Choice II. North Holland/Elsevier, July 1985, . George Tourlakis, Lectures in Logic and Set Theory. Vol. II: Set Theory, Cambridge University Press, 2003. Ernst Zermelo, "Untersuchungen über die Grundlagen der Mengenlehre I," Mathematische Annalen 65: (1908) pp. 261–81. PDF download via digizeitschriften.de Translated in: Jean van Heijenoort, 2002. From Frege to Gödel: A Source Book in Mathematical Logic, 1879–1931. New edition. Harvard University Press. 1904. "Proof that every set can be well-ordered," 139-41. 1908. "Investigations in the foundations of set theory I," 199–215. External links Axiom of Choice entry in the Springer Encyclopedia of Mathematics. Axiom of Choice and Its Equivalents entry at ProvenMath. Includes formal statement of the Axiom of Choice, Hausdorff's Maximal Principle, Zorn's Lemma and formal proofs of their equivalence down to the finest detail. Consequences of the Axiom of Choice, based on the book by Paul Howard and Jean Rubin. .

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

851

https://en.wikipedia.org/wiki/Alfred%20Nobel

Alfred Nobel

Alfred Bernhard Nobel ( , ; 21 October 1833 – 10 December 1896) was a Swedish chemist, engineer, inventor, businessman, and philanthropist. He is best known for having bequeathed his fortune to establish the Nobel Prize, though he also made several important contributions to science, holding 355 patents in his lifetime. Nobel's most famous invention was dynamite, a safer and easier means of harnessing the explosive power of nitroglycerin; it was patented in 1867 and was soon used worldwide for mining and infrastructure development. Nobel displayed an early aptitude for science and learning, particularly in chemistry and languages; he became fluent in six languages and filed his first patent at age 24. He embarked on many business ventures with his family, most notably owning Bofors, an iron and steel producer that he developed into a major manufacturer of cannons and other armaments. After reading an erroneous obituary condemning him as a war profiteer, Nobel was inspired to bequeath his fortune to the Nobel Prize institution, which would annually recognize those who "conferred the greatest benefit to humankind". The synthetic element nobelium was named after him, and his name and legacy also survives in companies such as Dynamit Nobel and AkzoNobel, which descend from mergers with companies he founded. Nobel was elected a member of the Royal Swedish Academy of Sciences, which, pursuant to his will, would be responsible for choosing the Nobel laureates in physics and in chemistry. Personal life Early life and education Alfred Nobel was born in Stockholm, United Kingdoms of Sweden and Norway on 21 October 1833. He was the third son of Immanuel Nobel (1801–1872), an inventor and engineer, and Karolina Andriette Nobel (née Ahlsell 1805–1889). The couple married in 1827 and had eight children. The family was impoverished and only Alfred and his three brothers survived beyond childhood. Through his father, Alfred Nobel was a descendant of the Swedish scientist Olaus Rudbeck (1630–1702), and in his turn, the boy was interested in engineering, particularly explosives, learning the basic principles from his father at a young age. Alfred Nobel's interest in technology was inherited from his father, an alumnus of Royal Institute of Technology in Stockholm.Following various business failures, Nobel's father moved to Saint Petersburg, Russia and grew successful there as a manufacturer of machine tools and explosives. He invented the veneer lathe (which made possible the production of modern plywood) and started work on the torpedo. In 1842, the family joined him in the city. Now prosperous, his parents were able to send Nobel to private tutors and the boy excelled in his studies, particularly in chemistry and languages, achieving fluency in English, French, German and Russian. For 18 months, from 1841 to 1842, Nobel went to the only school he ever attended as a child, in Stockholm. Nobel gained proficiency in Swedish, French, Russian, English, German, and Italian. He also developed sufficient literary skill to write poetry in English. His Nemesis is a prose tragedy in four acts about Beatrice Cenci. It was printed while he was dying, but the entire stock was destroyed immediately after his death except for three copies, being regarded as scandalous and blasphemous. It was published in Sweden in 2003 and has been translated into Slovenian and French. Religion Nobel was Lutheran and regularly attended the Church of Sweden Abroad during his Paris years, led by pastor Nathan Söderblom who received the Nobel Peace Prize in 1930. He became an agnostic in youth and was an atheist later in life, though still donated generously to the Church. Health and relationships Nobel travelled for much of his business life, maintaining companies in Europe and America while keeping a home in Paris from 1873 to 1891. He remained a solitary character, given to periods of depression. He remained unmarried, although his biographers note that he had at least three loves, the first in Russia with a girl named Alexandra who rejected his proposal. In 1876, Austro-Bohemian Countess Bertha Kinsky became his secretary, but she left him after a brief stay to marry her previous lover Baron Arthur Gundaccar von Suttner. Her contact with Nobel was brief, yet she corresponded with him until his death in 1896, and probably influenced his decision to include a peace prize in his will. She was awarded the 1905 Nobel Peace prize "for her sincere peace activities". Nobel's longest-lasting relationship was with Sofija Hess from Celje whom he met in 1876. The liaison lasted for 18 years. Residences In the years of 1865 to 1873, Alfred Nobel had his home in Krümmel, Hamburg, he afterward moved to a house in the Avenue Malakoff in Paris that same year.In 1894, when he acquired Bofors-Gullspång, the Björkborn Manor was included, he stayed at his manor house in Sweden during the summers. The manor house became his very last residence in Sweden and has after his death functioned as a museum. Alfred Nobel died on 10 December 1896, in Sanremo, Italy, at his very last residence, Villa Nobel, overlooking the Mediterranean Sea. Scientific career As a young man, Nobel studied with chemist Nikolai Zinin; then, in 1850, went to Paris to further the work. There he met Ascanio Sobrero, who had invented nitroglycerin three years before. Sobrero strongly opposed the use of nitroglycerin because it was unpredictable, exploding when subjected to variable heat or pressure. But Nobel became interested in finding a way to control and use nitroglycerin as a commercially usable explosive; it had much more power than gunpowder. In 1851 at age 18, he went to the United States for one year to study, working for a short period under Swedish-American inventor John Ericsson, who designed the American Civil War ironclad, USS Monitor. Nobel filed his first patent, an English patent for a gas meter, in 1857, while his first Swedish patent, which he received in 1863, was on "ways to prepare gunpowder".The family factory produced armaments for the Crimean War (1853–1856), but had difficulty switching back to regular domestic production when the fighting ended and they filed for bankruptcy. In 1859, Nobel's father left his factory in the care of the second son, Ludvig Nobel (1831–1888), who greatly improved the business. Nobel and his parents returned to Sweden from Russia and Nobel devoted himself to the study of explosives, and especially to the safe manufacture and use of nitroglycerin. Nobel invented a detonator in 1863, and in 1865 designed the blasting cap. On 3 September 1864, a shed used for preparation of nitroglycerin exploded at the factory in Heleneborg, Stockholm, Sweden, killing five people, including Nobel's younger brother Emil. Fazed by the accident, Nobel founded the company Nitroglycerin Aktiebolaget AB in Vinterviken so that he could continue to work in a more isolated area. Nobel invented dynamite in 1867, a substance easier and safer to handle than the more unstable nitroglycerin. Dynamite was patented in the US and the UK and was used extensively in mining and the building of transport networks internationally. In 1875, Nobel invented gelignite, more stable and powerful than dynamite, and in 1887, patented ballistite, a predecessor of cordite. Nobel was elected a member of the Royal Swedish Academy of Sciences in 1884, the same institution that would later select laureates for two of the Nobel prizes, and he received an honorary doctorate from Uppsala University in 1893. Nobel's brothers Ludvig and Robert founded the oil company Branobel and became hugely rich in their own right. Nobel invested in these and amassed great wealth through the development of these new oil regions. During his life, Nobel was issued 355 patents internationally, and by his death, his business had established more than 90 armaments factories, despite his apparently pacifist character. Inventions Nobel found that when nitroglycerin was incorporated in an absorbent inert substance like kieselguhr (diatomaceous earth) it became safer and more convenient to handle, and this mixture he patented in 1867 as "dynamite". Nobel demonstrated his explosive for the first time that year, at a quarry in Redhill, Surrey, England. In order to help reestablish his name and improve the image of his business from the earlier controversies associated with dangerous explosives, Nobel had also considered naming the highly powerful substance "Nobel's Safety Powder", but settled with Dynamite instead, referring to the Greek word for "power" (). Nobel later combined nitroglycerin with various nitrocellulose compounds, similar to collodion, but settled on a more efficient recipe combining another nitrate explosive, and obtained a transparent, jelly-like substance, which was a more powerful explosive than dynamite. Gelignite, or blasting gelatine, as it was named, was patented in 1876; and was followed by a host of similar combinations, modified by the addition of potassium nitrate and various other substances. Gelignite was more stable, transportable and conveniently formed to fit into bored holes, like those used in drilling and mining, than the previously used compounds. It was adopted as the standard technology for mining in the "Age of Engineering", bringing Nobel a great amount of financial success, though at a cost to his health. An offshoot of this research resulted in Nobel's invention of ballistite, the precursor of many modern smokeless powder explosives and still used as a rocket propellant. Nobel Prize In 1888, the death of his brother Ludvig caused several newspapers to publish obituaries of Alfred in error. One French newspaper condemned him for his invention of military explosives—not, as is commonly quoted, dynamite, which was mainly used for civilian applications—and is said to have brought about his decision to leave a better legacy after his death. The obituary stated, ("The merchant of death is dead"), and went on to say, "Dr. Alfred Nobel, who became rich by finding ways to kill more people faster than ever before, died yesterday." Nobel read the obituary and was appalled at the idea that he would be remembered in this way. His decision to posthumously donate the majority of his wealth to found the Nobel Prize has been credited at least in part to him wanting to leave behind a better legacy. On 27 November 1895, at the Swedish-Norwegian Club in Paris, Nobel signed his last will and testament and set aside the bulk of his estate to establish the Nobel Prizes, to be awarded annually without distinction of nationality. After taxes and bequests to individuals, Nobel's will allocated 94% of his total assets, 31,225,000 Swedish kronor, to establish the five Nobel Prizes. This converted to £1,687,837 (GBP) at the time. In 2012, the capital was worth around SEK 3.1 billion (US$472 million, EUR 337 million), which is almost twice the amount of the initial capital, taking inflation into account. The first three of these prizes are awarded for eminence in physical science, in chemistry and in medical science or physiology; the fourth is for literary work "in an ideal direction" and the fifth prize is to be given to the person or society that renders the greatest service to the cause of international fraternity, in the suppression or reduction of standing armies, or in the establishment or furtherance of peace congresses. The formulation for the literary prize being given for a work "in an ideal direction" ( in Swedish), is cryptic and has caused much confusion. For many years, the Swedish Academy interpreted "ideal" as "idealistic" () and used it as a reason not to give the prize to important but less romantic authors, such as Henrik Ibsen and Leo Tolstoy. This interpretation has since been revised, and the prize has been awarded to, for example, Dario Fo and José Saramago, who do not belong to the camp of literary idealism. There was room for interpretation by the bodies he had named for deciding on the physical sciences and chemistry prizes, given that he had not consulted them before making the will. In his one-page testament, he stipulated that the money go to discoveries or inventions in the physical sciences and to discoveries or improvements in chemistry. He had opened the door to technological awards, but had not left instructions on how to deal with the distinction between science and technology. Since the deciding bodies he had chosen were more concerned with the former, the prizes went to scientists more often than engineers, technicians or other inventors. Sweden's central bank Sveriges Riksbank celebrated its 300th anniversary in 1968 by donating a large sum of money to the Nobel Foundation to be used to set up a sixth prize in the field of economics in honour of Alfred Nobel. In 2001, Alfred Nobel's great-great-nephew, Peter Nobel (born 1931), asked the Bank of Sweden to differentiate its award to economists given "in Alfred Nobel's memory" from the five other awards. This request added to the controversy over whether the Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel is actually a legitimate "Nobel Prize". Death Nobel was accused of high treason against France for selling Ballistite to Italy, so he moved from Paris to Sanremo, Italy in 1891. On 10 December 1896, he suffered a stroke and died. He had left most of his wealth in trust, unbeknownst to his family, in order to fund the Nobel Prize awards. He is buried in Norra begravningsplatsen in Stockholm. Monuments and legacy The Monument to Alfred Nobel (, ) in Saint Petersburg is located along the Bolshaya Nevka River on Petrogradskaya Embankment. It was dedicated in 1991 to mark the 90th anniversary of the first Nobel Prize presentation. Diplomat Thomas Bertelman and Professor Arkady Melua were initiators of the creation of the monument (1989). Professor A. Melua has provided funds for the establishment of the monument (J.S.Co. "Humanistica", 1990–1991). The abstract metal sculpture was designed by local artists Sergey Alipov and Pavel Shevchenko, and appears to be an explosion or branches of a tree. Petrogradskaya Embankment is the street where the Nobel's family lived until 1859. Criticism of Nobel focuses on his leading role in weapons manufacturing and sales, and some question his motives in creating his prizes, suggesting they are intended to improve his reputation. See also Nobel Foundation References Further reading Schück, H, and Sohlman, R., (1929). The Life of Alfred Nobel. London: William Heineman Ltd. Alfred Nobel US Patent No 78,317, dated 26 May 1868 Evlanoff, M. and Fluor, M. Alfred Nobel – The Loneliest Millionaire. Los Angeles, Ward Ritchie Press, 1969. Sohlman, R. The Legacy of Alfred Nobel, transl. Schubert E. London: The Bodley Head, 1983 (Swedish original, Ett Testamente, published in 1950). External links Alfred Nobel – Man behind the Prizes Biography at the Norwegian Nobel Institute Nobelprize.org Documents of Life and Activity of The Nobel Family. Under the editorship of Professor Arkady Melua. Series of books. "The Nobels in Baku" in Azerbaijan International, Vol 10.2 (Summer 2002), 56–59. The Nobel Prize in Postage Stamps A German branch or followup (German) Alfred Nobel and his unknown coworker 1833 births 1896 deaths Burials at Norra begravningsplatsen Members of the Royal Swedish Academy of Sciences Alfred Nobel Prize Engineers from Stockholm 19th-century Swedish businesspeople 19th-century Swedish scientists 19th-century Swedish engineers Swedish chemists Swedish philanthropists Explosives engineers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

856

https://en.wikipedia.org/wiki/Apple%20Inc.

Apple Inc.

Apple Inc. is an American multinational technology company that specializes in consumer electronics, software and online services. Apple is the largest information technology company by revenue (totaling in 2021) and, as of January 2021, it is the world's most valuable company, the fourth-largest personal computer vendor by unit sales and second-largest mobile phone manufacturer. It is one of the Big Five American information technology companies, alongside Alphabet, Amazon, Meta, and Microsoft. Apple was founded as Apple Computer Company on April 1, 1976, by Steve Jobs, Steve Wozniak and Ronald Wayne to develop and sell Wozniak's Apple I personal computer. It was incorporated by Jobs and Wozniak as Apple Computer, Inc. in 1977 and the company's next computer, the Apple II became a best seller. Apple went public in 1980, to instant financial success. The company went onto develop new computers featuring innovative graphical user interfaces, including the original Macintosh, announced in a critically acclaimed advertisement, "1984", directed by Ridley Scott. By 1985, the high cost of its products and power struggles between executives caused problems. Wozniak stepped back from Apple amicably, while Jobs resigned to found NeXT, taking some Apple employees with him. As the market for personal computers expanded and evolved throughout the 1990s, Apple lost considerable market share to the lower-priced duopoly of the Microsoft Windows operating system on Intel-powered PC clones (also known as "Wintel"). In 1997, weeks away from bankruptcy, the company bought NeXT to resolve Apple's unsuccessful operating system strategy and entice Jobs back to the company. Over the next decade, Jobs guided Apple back to profitability through a number of tactics including introducing the iMac, iPod, iPhone and iPad to critical acclaim, launching memorable advertising campaigns, opening the Apple Store retail chain, and acquiring numerous companies to broaden the company's product portfolio. Jobs resigned in 2011 for health reasons, and died two months later. He was succeeded as CEO by Tim Cook. Apple became the first publicly traded U.S. company to be valued at over $1 trillion in August 2018, then $2 trillion in August 2020, and most recently $3 trillion in January 2022. The company receives criticism regarding the labor practices of its contractors, its environmental practices, and its business ethics, including anti-competitive practices and materials sourcing. The company enjoys a high level of brand loyalty, and is ranked as one of the world's most valuable brands. History 1976–1980: Founding and incorporation Apple Computer Company was founded on April 1, 1976, by Steve Jobs, Steve Wozniak, and Ronald Wayne as a business partnership. The company's first product was the Apple I, a computer designed and hand-built entirely by Wozniak. To finance its creation, Jobs sold his only motorized means of transportation, a VW Bus, for a few hundred dollars, and Wozniak sold his HP-65 calculator for . Wozniak debuted the first prototype Apple I at the Homebrew Computer Club in July 1976. The Apple I was sold as a motherboard with CPU, RAM, and basic textual-video chips—a base kit concept which would not yet be marketed as a complete personal computer. It went on sale soon after debut for . Wozniak later said he was unaware of the coincidental mark of the beast in the number 666, and that he came up with the price because he liked "repeating digits". Apple Computer, Inc. was incorporated on January 3, 1977, without Wayne, who had left and sold his share of the company back to Jobs and Wozniak for $800 only twelve days after having co-founded Apple. Multimillionaire Mike Markkula provided essential business expertise and funding of to Jobs and Wozniak during the incorporation of Apple. During the first five years of operations, revenues grew exponentially, doubling about every four months. Between September 1977 and September 1980, yearly sales grew from $775,000 to $118 million, an average annual growth rate of 533%. The Apple II, also invented by Wozniak, was introduced on April 16, 1977, at the first West Coast Computer Faire. It differed from its major rivals, the TRS-80 and Commodore PET, because of its character cell-based color graphics and open architecture. While the Apple I and early Apple II models used ordinary audio cassette tapes as storage devices, they were superseded by the introduction of a -inch floppy disk drive and interface called the Disk II in 1978. The Apple II was chosen to be the desktop platform for the first "killer application" of the business world: VisiCalc, a spreadsheet program released in 1979. VisiCalc created a business market for the Apple II and gave home users an additional reason to buy an Apple II: compatibility with the office. Before VisiCalc, Apple had been a distant third place competitor to Commodore and Tandy. By the end of the 1970s, Apple had become the leading computer manufacturer in the United States. On December 12, 1980, Apple (ticker symbol "AAPL") went public selling 4.6 million shares at $22 per share ($.39 per share when adjusting for stock splits ), generating over $100 million, which was more capital than any IPO since Ford Motor Company in 1956. By the end of the day, 300 millionaires were created, from a stock price of $29 per share and a market cap of $1.778 billion. 1980–1990: Success with Macintosh A critical moment in the company's history came in December 1979 when Jobs and several Apple employees, including human–computer interface expert Jef Raskin, visited Xerox PARC in to see a demonstration of the Xerox Alto, a computer using a graphical user interface. Xerox granted Apple engineers three days of access to the PARC facilities in return for the option to buy 100,000 shares (5.6 million split-adjusted shares ) of Apple at the pre-IPO price of $10 a share. After the demonstration, Jobs was immediately convinced that all future computers would use a graphical user interface, and development of a GUI began for the Apple Lisa, named after Jobs's daughter. The Lisa division would be plagued by infighting, and in 1982 Jobs was pushed off the project. The Lisa launched in 1983 and became the first personal computer sold to the public with a GUI, but was a commercial failure due to its high price and limited software titles. Jobs, angered by being pushed off the Lisa team, took over the company's Macintosh division. Wozniak and Raskin had envisioned the Macintosh as low-cost-computer with a text-based interface like the Apple II, but a plane crash in 1981 forced Wozniak to step back from the project. Jobs quickly redefined the Macintosh as a graphical system that would be cheaper than the Lisa, undercutting his former division. Jobs was also hostile to the Apple II division, which at the time, generated most of the company's revenue. In 1984, Apple launched the Macintosh, the first personal computer to be sold without a programming language. Its debut was signified by "1984", a $1.5 million television advertisement directed by Ridley Scott that aired during the third quarter of Super Bowl XVIII on January 22, 1984. This is now hailed as a watershed event for Apple's success and was called a "masterpiece" by CNN and one of the greatest TV advertisements of all time by TV Guide. The advertisement created great interest in the original Macintosh, and sales were initially good, but began to taper off dramatically after the first three months as reviews started to come in. Jobs had made the decision to equip the original Macintosh with 128 kilobytes of RAM, attempting to reach a price point, which limited its speed and the software that could be used. The Macintosh would eventually ship for , a price panned by critics in light of its slow performance. In early 1985, this sales slump triggered a power struggle between Steve Jobs and CEO John Sculley, who had been hired away from Pepsi two years earlier by Jobs using the famous line, "Do you want to sell sugar water for the rest of your life or come with me and change the world?" Sculley decided to remove Jobs as the head of the Macintosh division, with unanimous support from the Apple board of directors. The board of directors instructed Sculley to contain Jobs and his ability to launch expensive forays into untested products. Rather than submit to Sculley's direction, Jobs attempted to oust him from his leadership role at Apple. Informed by Jean-Louis Gassée, Sculley found out that Jobs had been attempting to organize a boardroom coup and called an emergency meeting at which Apple's executive staff sided with Sculley and stripped Jobs of all operational duties. Jobs resigned from Apple in September 1985 and took a number of Apple employees with him to found NeXT. Wozniak had also quit his active employment at Apple earlier in 1985 to pursue other ventures, expressing his frustration with Apple's treatment of the Apple II division and stating that the company had "been going in the wrong direction for the last five years". Despite Wozniak's grievances, he officially remained employed by Apple, and to this day continues to work for the company as a representative, receiving a stipend estimated to be $120,000 per year for this role. Both Jobs and Wozniak remained Apple shareholders after their departures. After the departures of Jobs and Wozniak, Sculley worked to improve the Macintosh in 1985 by quadrupling the RAM and introducing the LaserWriter, the first reasonably priced PostScript laser printer. PageMaker, an early desktop publishing application taking advantage of the PostScript language, was also released by Aldus Corporation in July 1985. It has been suggested that the combination of Macintosh, LaserWriter and PageMaker was responsible for the creation of the desktop publishing market. This dominant position in the desktop publishing market allowed the company to focus on higher price points, the so-called "high-right policy" named for the position on a chart of price vs. profits. Newer models selling at higher price points offered higher profit margin, and appeared to have no effect on total sales as power users snapped up every increase in speed. Although some worried about pricing themselves out of the market, the high-right policy was in full force by the mid-1980s, notably due to Jean-Louis Gassée's mantra of "fifty-five or die", referring to the 55% profit margins of the Macintosh II. This policy began to backfire in the last years of the decade as desktop publishing programs appeared on PC clones that offered some or much of the same functionality of the Macintosh, but at far lower price points. The company lost its dominant position in the desktop publishing market and estranged many of its original consumer customer base who could no longer afford their high-priced products. The Christmas season of 1989 was the first in the company's history to have declining sales, which led to a 20% drop in Apple's stock price. During this period, the relationship between Sculley and Gassée deteriorated, leading Sculley to effectively demote Gassée in January 1990 by appointing Michael Spindler as the chief operating officer. Gassée left the company later that year. 1990–1997: Decline and restructuring The company pivoted strategy and in October 1990 introduced three lower-cost models, the Macintosh Classic, the Macintosh LC, and the Macintosh IIsi, all of which saw significant sales due to pent-up demand. In 1991, Apple introduced the hugely successful PowerBook with a design that set the current shape for almost all modern laptops. The same year, Apple introduced System 7, a major upgrade to the Macintosh operating system, adding color to the interface and introducing new networking capabilities. The success of the lower-cost Macs and PowerBook brought increasing revenue. For some time, Apple was doing incredibly well, introducing fresh new products and generating increasing profits in the process. The magazine MacAddict named the period between 1989 and 1991 as the "first golden age" of the Macintosh. The success of Apple's lower-cost consumer models, especially the LC, also led to the cannibalization of their higher-priced machines. To address this, management introduced several new brands, selling largely identical machines at different price points, aimed at different markets: the high-end Quadra models, the mid-range Centris line, and the consumer-marketed Performa series. This led to significant market confusion, as customers did not understand the difference between models. The early 1990s also saw the discontinuation of the Apple II series, which was expensive to produce, and the company felt was still taking sales away from lower-cost Macintosh models. After the launch of the LC, Apple began encouraging developers to create applications for Macintosh rather than Apple II, and authorized salespersons to direct consumers towards Macintosh and away from Apple II. The Apple IIe was discontinued in 1993. Throughout this period, Microsoft continued to gain market share with its Windows graphical user interface that it sold to manufacturers of generally less expensive PC clones. While the Macintosh was more expensive, it offered a more tightly integrated user experience, but the company struggled to make the case to consumers. Apple also experimented with a number of other unsuccessful consumer targeted products during the 1990s, including digital cameras, portable CD audio players, speakers, video game consoles, the eWorld online service, and TV appliances. Most notably, enormous resources were invested in the problem-plagued Newton tablet division, based on John Sculley's unrealistic market forecasts. personal computers, while Apple was delivering a richly engineered but expensive experience. Apple relied on high profit margins and never developed a clear response; instead, they sued Microsoft for using a GUI similar to the Apple Lisa in Apple Computer, Inc. v. Microsoft Corp. The lawsuit dragged on for years before it was finally dismissed. The major product flops and the rapid loss of market share to Windows sullied Apple's reputation, and in 1993 Sculley was replaced as CEO by Michael Spindler. With Spindler at the helm Apple, IBM, and Motorola formed the AIM alliance in 1994 with the goal of creating a new computing platform (the PowerPC Reference Platform; PReP), which would use IBM and Motorola hardware coupled with Apple software. The AIM alliance hoped that PReP's performance and Apple's software would leave the PC far behind and thus counter the dominance of Windows. The same year, Apple introduced the Power Macintosh, the first of many Apple computers to use Motorola's PowerPC processor. In the wake of the alliance, Apple opened up to the idea of allowing Motorola and other companies to build Macintosh clones. Over the next two years, 75 distinct Macintosh clone models were introduced. However, by 1996 Apple executives were worried that the clones were cannibalizing sales of their own high-end computers, where profit margins were highest. In 1996, Spindler was replaced by Gil Amelio as CEO. Hired for his reputation as a corporate rehabilitator, Amelio made deep changes, including extensive layoffs and cost-cutting. This period was also marked by numerous failed attempts to modernize the Macintosh operating system (MacOS). The original Macintosh operating system (System 1) was not built for multitasking (running several applications at once). The company attempted to correct this with by introducing cooperative multitasking in System 5, but the company still felt it needed a more modern approach. This led to the Pink project in 1988, A/UX that same year, Copland in 1994, and the attempted purchase of BeOS in 1996. Talks with Be stalled the CEO, former Apple executive Jean-Louis Gassée, demanded $300 million instead of the $125 million Apple wanted to pay. Only weeks away from bankruptcy, Apple's board decided NeXTSTEP was a better choice for its next operating system and purchased NeXT in late 1996 for $429 million, bringing back Apple co-founder Steve Jobs. 1997–2007: Return to profitability The NeXT acquisition was finalized on February 9, 1997, and the board brought Jobs back to Apple as an advisor. On July 9, 1997, Jobs staged a boardroom coup that resulted in Amelio's resignation after overseeing a three-year record-low stock price and crippling financial losses. The board named Jobs as interim CEO and he immediately began a review of the company's products. Jobs would order 70% of the company's products to be cancelled, resulting in the loss of 3,000 jobs, and taking Apple back to the core of its computer offerings. The next month, in August 1997, Steve Jobs convinced Microsoft to make a $150 million investment in Apple and a commitment to continue developing software for the Mac. The investment was seen as an "antitrust insurance policy" for Microsoft who had recently settled with the Department of Justice over anti-competitive practices. Jobs also ended the Mac clone deals and in September 1997, purchased the largest clone maker, Power Computing. On November 10, 1997, Apple introduced the Apple Store website, which was tied to a new build-to-order manufacturing that had been successfully used by PC manufacturer Dell. The moves paid off for Jobs, at the end of his first year as CEO, the company turned a $309 million profit. On May 6, 1998, Apple introduced a new all-in-one computer reminiscent of the original Macintosh: the iMac. The iMac was a huge success for Apple selling 800,000 units in its first five months and ushered in major shifts in the industry by abandoning legacy technologies like the 3½-inch diskette, being an early adopter of the USB connector, and coming pre-installed with internet connectivity (the "i" in iMac) via Ethernet and a dial-up modem. The device also had a striking eardrop shape and translucent materials, designed by Jonathan Ive, who although hired by Amelio, would go on to work collaboratively with Jobs for the next decade to chart a new course the design of Apple's products. A little more than a year later on July 21, 1999, Apple introduced the iBook, a laptop for consumers. It was the culmination of a strategy established by Jobs to produce only four products: refined versions of the Power Macintosh G3 desktop and PowerBook G3 laptop for professionals, along with the iMac desktop and iBook laptop for consumers. Jobs felt the small product line allowed for a greater focus on quality and innovation. At around the same time, Apple also completed numerous acquisitions to create a portfolio of digital media production software for both professionals and consumers. Apple acquired of Macromedia's Key Grip digital video editing software project which was renamed Final Cut Pro when it was launched on the retail market in April 1999. The development of Key Grip also led to Apple's release of the consumer video-editing product iMovie in October 1999. Next, Apple successfully acquired the German company Astarte in April 2000, which had developed the DVD authoring software DVDirector, which Apple would sell as the professional-oriented DVD Studio Pro software product, and used the same technology to create iDVD for the consumer market. In 2000, Apple purchased the SoundJam MP audio player software from Casady & Greene. Apple renamed the program iTunes, while simplifying the user interface and adding the ability to burn CDs. 2001 would be a pivotal year for the Apple with the company making three announcements that would change the course of the company. The first announcement came on March 24, 2001, that Apple was nearly ready to release a new modern operating system, Mac OS X. The announcement came after numerous failed attempts in the early 1990s, and several years of development. Mac OS X was based on NeXTSTEP, OPENSTEP, and BSD Unix, with Apple aiming to combine the stability, reliability, and security of Unix with the ease of use afforded by an overhauled user interface, heavily influenced by NeXTSTEP. To aid users in migrating from Mac OS 9, the new operating system allowed the use of OS 9 applications within Mac OS X via the Classic Environment. In May 2001 the company opened its first two Apple Store retail locations in Virginia and California, offering an improved presentation of the company's products. At the time, many speculated that the stores would fail, but they went on to become highly successful, and the first of more than 500 stores around the world. On October 23, 2001, Apple debuted the iPod portable digital audio player. The product, which was first sold on November 10, 2001, was phenomenally successful with over 100 million units sold within six years. In 2003, Apple's iTunes Store was introduced. The service offered music downloads for $0.99 a song and integration with the iPod. The iTunes Store quickly became the market leader in online music services, with over five billion downloads by June 19, 2008. Two years later, the iTunes Store was the world's largest music retailer. In 2002, Apple purchased Nothing Real for their advanced digital compositing application Shake, as well as Emagic for the music productivity application Logic. The purchase of Emagic made Apple the first computer manufacturer to own a music software company. The acquisition was followed by the development of Apple's consumer-level GarageBand application. The release of iPhoto in the same year completed the iLife suite. At the Worldwide Developers Conference keynote address on June 6, 2005, Jobs announced that Apple would move away from PowerPC processors, and the Mac would transition to Intel processors in 2006. On January 10, 2006, the new MacBook Pro and iMac became the first Apple computers to use Intel's Core Duo CPU. By August 7, 2006, Apple made the transition to Intel chips for the entire Mac product line—over one year sooner than announced. The Power Mac, iBook, and PowerBook brands were retired during the transition; the Mac Pro, MacBook, and MacBook Pro became their respective successors. On April 29, 2009, The Wall Street Journal reported that Apple was building its own team of engineers to design microchips. Apple also introduced Boot Camp in 2006 to help users install Windows XP or Windows Vista on their Intel Macs alongside Mac OS X. Apple's success during this period was evident in its stock price. Between early 2003 and 2006, the price of Apple's stock increased more than tenfold, from around $6 per share (split-adjusted) to over $80. When Apple surpassed Dell's market cap in January 2006, Jobs sent an email to Apple employees saying Dell's CEO Michael Dell should eat his words. Nine years prior, Dell had said that if he ran Apple he would "shut it down and give the money back to the shareholders". 2007–2011: Success with mobile devices During his keynote speech at the Macworld Expo on January 9, 2007, Jobs announced that Apple Computer, Inc. would thereafter be known as "Apple Inc.", because the company had shifted its emphasis from computers to consumer electronics. This event also saw the announcement of the iPhone and the Apple TV. The company sold 270,000 iPhone units during the first 30 hours of sales, and the device was called "a game changer for the industry". In an article posted on Apple's website on February 6, 2007, Jobs wrote that Apple would be willing to sell music on the iTunes Store without digital rights management (DRM) , thereby allowing tracks to be played on third-party players, if record labels would agree to drop the technology. On April 2, 2007, Apple and EMI jointly announced the removal of DRM technology from EMI's catalog in the iTunes Store, effective in May 2007. Other record labels eventually followed suit and Apple published a press release in January 2009 to announce that all songs on the iTunes Store are available without their FairPlay DRM. In July 2008, Apple launched the App Store to sell third-party applications for the iPhone and iPod Touch. Within a month, the store sold 60 million applications and registered an average daily revenue of $1 million, with Jobs speculating in August 2008 that the App Store could become a billion-dollar business for Apple. By October 2008, Apple was the third-largest mobile handset supplier in the world due to the popularity of the iPhone. On January 14, 2009, Jobs announced in an internal memo that he would be taking a six-month medical leave of absence from Apple until the end of June 2009 and would spend the time focusing on his health. In the email, Jobs stated that "the curiosity over my personal health continues to be a distraction not only for me and my family, but everyone else at Apple as well", and explained that the break would allow the company "to focus on delivering extraordinary products". Though Jobs was absent, Apple recorded its best non-holiday quarter (Q1 FY 2009) during the recession with revenue of $8.16 billion and profit of $1.21 billion. After years of speculation and multiple rumored "leaks", Apple unveiled a large screen, tablet-like media device known as the iPad on January 27, 2010. The iPad ran the same touch-based operating system as the iPhone, and all iPhone apps were compatible with the iPad. This gave the iPad a large app catalog on launch, though having very little development time before the release. Later that year on April 3, 2010, the iPad was launched in the US. It sold more than 300,000 units on its first day, and 500,000 by the end of the first week. In May of the same year, Apple's market cap exceeded that of competitor Microsoft for the first time since 1989. In June 2010, Apple released the iPhone 4, which introduced video calling using FaceTime, multitasking, and a new uninsulated stainless steel design that acted as the phone's antenna. Later that year, Apple again refreshed its iPod line of MP3 players by introducing a multi-touch iPod Nano, an iPod Touch with FaceTime, and an iPod Shuffle that brought back the clickwheel buttons of earlier generations. It also introduced the smaller, cheaper second generation Apple TV which allowed renting of movies and shows. On January 17, 2011, Jobs announced in an internal Apple memo that he would take another medical leave of absence for an indefinite period to allow him to focus on his health. Chief Operating Officer Tim Cook assumed Jobs's day-to-day operations at Apple, although Jobs would still remain "involved in major strategic decisions". Apple became the most valuable consumer-facing brand in the world. In June 2011, Jobs surprisingly took the stage and unveiled iCloud, an online storage and syncing service for music, photos, files, and software which replaced MobileMe, Apple's previous attempt at content syncing. This would be the last product launch Jobs would attend before his death. On August 24, 2011, Jobs resigned his position as CEO of Apple. He was replaced by Cook and Jobs became Apple's chairman. Apple did not have a chairman at the time and instead had two co-lead directors, Andrea Jung and Arthur D. Levinson, who continued with those titles until Levinson replaced Jobs as chairman of the board in November after Jobs' death. 2011–present: Post–Jobs era, Tim Cook's leadership On October 5, 2011, Steve Jobs died, marking the end of an era for Apple. The first major product announcement by Apple following Jobs's passing occurred on January 19, 2012, when Apple's Phil Schiller introduced iBook's Textbooks for iOS and iBook Author for Mac OS X in New York City. Jobs stated in the biography "Jobs" that he wanted to reinvent the textbook industry and education. From 2011 to 2012, Apple released the iPhone 4S and iPhone 5, which featured improved cameras, an intelligent software assistant named Siri, and cloud-synced data with iCloud; the third and fourth generation iPads, which featured Retina displays; and the iPad Mini, which featured a 7.9-inch screen in contrast to the iPad's 9.7-inch screen. These launches were successful, with the iPhone 5 (released September 21, 2012) becoming Apple's biggest iPhone launch with over two million pre-orders and sales of three million iPads in three days following the launch of the iPad Mini and fourth generation iPad (released November 3, 2012). Apple also released a third-generation 13-inch MacBook Pro with a Retina display and new iMac and Mac Mini computers. On August 20, 2012, Apple's rising stock price increased the company's market capitalization to a then-record $624 billion. This beat the non-inflation-adjusted record for market capitalization previously set by Microsoft in 1999. On August 24, 2012, a US jury ruled that Samsung should pay Apple $1.05 billion (£665m) in damages in an intellectual property lawsuit. Samsung appealed the damages award, which was reduced by $450 million and further granted Samsung's request for a new trial. On November 10, 2012, Apple confirmed a global settlement that dismissed all existing lawsuits between Apple and HTC up to that date, in favor of a ten-year license agreement for current and future patents between the two companies. It is predicted that Apple will make $280 million a year from this deal with HTC. In May 2014, the company confirmed its intent to acquire Dr. Dre and Jimmy Iovine's audio company Beats Electronics—producer of the "Beats by Dr. Dre" line of headphones and speaker products, and operator of the music streaming service Beats Music—for $3 billion, and to sell their products through Apple's retail outlets and resellers. Iovine believed that Beats had always "belonged" with Apple, as the company modeled itself after Apple's "unmatched ability to marry culture and technology." The acquisition was the largest purchase in Apple's history. During a press event on September 9, 2014, Apple introduced a smartwatch, the Apple Watch. Initially, Apple marketed the device as a fashion accessory and a complement to the iPhone, that would allow people to look at their smartphones less. Over time, the company has focused on developing health and fitness-oriented features on the watch, in an effort to compete with dedicated activity trackers. In January 2016, it was announced that one billion Apple devices were in active use worldwide. On June 6, 2016, Fortune released Fortune 500, their list of companies ranked on revenue generation. In the trailing fiscal year (2015), Apple appeared on the list as the top tech company. It ranked third, overall, with $233 billion in revenue. This represents a movement upward of two spots from the previous year's list. In June 2017, Apple announced the HomePod, its smart speaker aimed to compete against Sonos, Google Home, and Amazon Echo. Towards the end of the year, TechCrunch reported that Apple was acquiring Shazam, a company that introduced its products at WWDC and specializing in music, TV, film and advertising recognition. The acquisition was confirmed a few days later, reportedly costing Apple $400 million, with media reports noting that the purchase looked like a move to acquire data and tools bolstering the Apple Music streaming service. The purchase was approved by the European Union in September 2018. Also in June 2017, Apple appointed Jamie Erlicht and Zack Van Amburg to head the newly formed worldwide video unit. In November 2017, Apple announced it was branching out into original scripted programming: a drama series starring Jennifer Aniston and Reese Witherspoon, and a reboot of the anthology series Amazing Stories with Steven Spielberg. In June 2018, Apple signed the Writers Guild of America's minimum basic agreement and Oprah Winfrey to a multi-year content partnership. Additional partnerships for original series include Sesame Workshop and DHX Media and its subsidiary Peanuts Worldwide, as well as a partnership with A24 to create original films. On August 19, 2020, Apple's share price briefly topped $467.77, making Apple the first US company with a market capitalization of $2 trillion. During its annual WWDC keynote speech on June 22, 2020, Apple announced it would move away from Intel processors, and the Mac would transition to processors developed in-house. The announcement was expected by industry analysts, and it has been noted that Macs featuring Apple's processors would allow for big increases in performance over current Intel-based models. On November 10, 2020, the MacBook Air, MacBook Pro, and the Mac Mini became the first Mac devices powered by an Apple-designed processor, the Apple M1. Products Macintosh Macintosh, commonly known as Mac, is Apple's line of personal computers that use the company's proprietary macOS operating system. Personal computers were Apple's original business line, but they account for only about 10 percent of the company's revenue. The company is in the process of switching Mac computers from Intel processors to Apple silicon, a custom-designed system on a chip platform. , there are five Macintosh computer families in production: iMac: Consumer all-in-one desktop computer, introduced in 1998. Mac Mini: Consumer sub-desktop computer, introduced in 2005. MacBook Pro: Professional notebook, introduced in 2006. Mac Pro: Professional workstation, introduced in 2006. MacBook Air: Consumer ultra-thin notebook, introduced in 2008. Apple also sells a variety of accessories for Macs, including the Pro Display XDR, Magic Mouse, Magic Trackpad, and Magic Keyboard. The company also develops several pieces of software that are included in the purchase price of a Mac, including the Safari web browser, the iMovie video editor, the GarageBand audio editor and the iWork productivity suite. Additionally, the company sells several professional software applications including the Final Cut Pro video editor, Motion for video animations, the Logic Pro audio editor, MainStage for live audio production, and Compressor for media compression and encoding. iPhone iPhone is Apple's line of smartphones that use the company's proprietary iOS operating system, derived from macOS. The first-generation iPhone was announced by then-Apple CEO Steve Jobs on January 9, 2007. Since then, Apple has annually released new iPhone models and iOS updates. The iPhone has a user interface built around a multi-touch screen, which at the time of its introduction was described as "revolutionary" and a "game-changer" for the mobile phone industry. The device has been credited with popularizing the smartphone and slate form factor, and with creating a large market for smartphone apps, or "app economy". iOS is one of the two largest smartphone platforms in the world alongside Android. The iPhone has generated large profits for the company, and is credited with helping to make Apple one of the world's most valuable publicly traded companies. , the iPhone accounts for more than half of the company's revenue. , 33 iPhone models have been produced, with five smartphone families in production: iPhone 13 iPhone 13 Pro iPhone 12 iPhone SE (2nd generation) iPhone 11 iPad iPad is Apple's line of tablet computers that use the company's proprietary iPadOS operating system, derived from macOS and iOS. The first-generation iPad was announced on January 27, 2010. The iPad took the multi-touch user interface first introduced in the iPhone, and adapted it to a larger screen, marked for interaction with multimedia formats including newspapers, books, photos, videos, music, documents, video games, and most existing iPhone apps. Earlier generations of the iPad used the same iOS operating system as the company's smartphones before being split off in 2019. Apple has sold more than 500 million iPads, though sales peaked in 2013. However, the iPad remains the most popular tablet computer by sales , and accounted for nine percent of the company's revenue . In recent years, Apple has started offering more powerful versions of the device, with the current iPad Pro sharing the same Apple silicon as Macintosh computers, along with a smaller version of the device called iPad mini, and an upgraded version called iPad Air. , there are four iPad families in production: iPad (9th generation) iPad mini (6th generation) iPad Pro (5th generation) iPad Air (4th generation) Wearables, Home and Accessories Apple also makes several other products that it categorizes as "Wearables, Home and Accessories." These products include the AirPods line of wireless headphones, Apple TV digital media players, Apple Watch smartwatches, Beats headphones, HomePod Mini smart speakers, and the iPod touch, the last remaining device in Apple's successful line of iPod portable media players. , this broad line of products comprises about 11% of the company's revenues. Services Apple also offers a broad line of services that it earns revenue on, including advertising in the App Store and Apple News app, the AppleCare+ extended warranty plan, the iCloud+ cloud-based data storage service, payment services through the Apple Card credit card and the Apple Pay processing platform, a digital content services including Apple Books, Apple Fitness+, Apple Music, Apple News+, Apple TV+, and the iTunes Store. , services comprise about 19% of the company's revenue. Many of the services have been launched since 2019 when Apple announced it would be making a concerted effort to expand its service revenues. Corporate identity Logo According to Steve Jobs, the company's name was inspired by his visit to an apple farm while on a fruitarian diet. Jobs thought the name "Apple" was "fun, spirited and not intimidating". Apple's first logo, designed by Ron Wayne, depicts Sir Isaac Newton sitting under an apple tree. It was almost immediately replaced by Rob Janoff's "rainbow Apple", the now-familiar rainbow-colored silhouette of an apple with a bite taken out of it. Janoff presented Jobs with several different monochromatic themes for the "bitten" logo, and Jobs immediately took a liking to it. However, Jobs insisted that the logo be colorized to humanize the company. The logo was designed with a bite so that it would not be confused with a cherry. The colored stripes were conceived to make the logo more accessible, and to represent the fact the Apple II could generate graphics in color. This logo is often erroneously referred to as a tribute to Alan Turing, with the bite mark a reference to his method of suicide. Both Janoff and Apple deny any homage to Turing in the design of the logo. On August 27, 1999 (the year following the introduction of the iMac G3), Apple officially dropped the rainbow scheme and began to use monochromatic logos nearly identical in shape to the previous rainbow incarnation. An Aqua-themed version of the monochrome logo was used from 1998 to 2003, and a glass-themed version was used from 2007 to 2013. Steve Jobs and Steve Wozniak were fans of the Beatles, but Apple Inc. had name and logo trademark issues with Apple Corps Ltd., a multimedia company started by the Beatles in 1968. This resulted in a series of lawsuits and tension between the two companies. These issues ended with the settling of their lawsuit in 2007. Advertising Apple's first slogan, "Byte into an Apple", was coined in the late 1970s. From 1997 to 2002, the slogan "Think Different" was used in advertising campaigns, and is still closely associated with Apple. Apple also has slogans for specific product lines — for example, "iThink, therefore iMac" was used in 1998 to promote the iMac, and "Say hello to iPhone" has been used in iPhone advertisements. "Hello" was also used to introduce the original Macintosh, Newton, iMac ("hello (again)"), and iPod. From the introduction of the Macintosh in 1984, with the 1984 Super Bowl advertisement to the more modern Get a Mac adverts, Apple has been recognized for its efforts towards effective advertising and marketing for its products. However, claims made by later campaigns were criticized, particularly the 2005 Power Mac ads. Apple's product advertisements gained a lot of attention as a result of their eye-popping graphics and catchy tunes. Musicians who benefited from an improved profile as a result of their songs being included on Apple advertisements include Canadian singer Feist with the song "1234" and Yael Naïm with the song "New Soul". Brand loyalty Apple customers gained a reputation for devotion and loyalty early in the company's history. In 1984, BYTE stated that: Apple evangelists were actively engaged by the company at one time, but this was after the phenomenon had already been firmly established. Apple evangelist Guy Kawasaki has called the brand fanaticism "something that was stumbled upon," while Ive explained in 2014 that "People have an incredibly personal relationship" with Apple's products. Apple Store openings and new product releases can draw crowds of hundreds, with some waiting in line as much as a day before the opening. The opening of New York City's Apple Fifth Avenue store in 2006 was highly attended, and had visitors from Europe who flew in for the event. In June 2017, a newlywed couple took their wedding photos inside the then-recently opened Orchard Road Apple Store in Singapore. The high level of brand loyalty has been criticized and ridiculed, applying the epithet "Apple fanboy" and mocking the lengthy lines before a product launch. An internal memo leaked in 2015 suggested the company planned to discourage long lines and direct customers to purchase its products on its website. Fortune magazine named Apple the most admired company in the United States in 2008, and in the world from 2008 to 2012. On September 30, 2013, Apple surpassed Coca-Cola to become the world's most valuable brand in the Omnicom Group's "Best Global Brands" report. Boston Consulting Group has ranked Apple as the world's most innovative brand every year since 2005. The New York Times in 1985 stated that "Apple above all else is a marketing company". John Sculley agreed, telling The Guardian newspaper in 1997 that "People talk about technology, but Apple was a marketing company. It was the marketing company of the decade." Research in 2002 by NetRatings indicate that the average Apple consumer was usually more affluent and better educated than other PC company consumers. The research indicated that this correlation could stem from the fact that on average Apple Inc. products were more expensive than other PC products. In response to a query about the devotion of loyal Apple consumers, Jonathan Ive responded: there are 1.65 billion Apple products in active use. Headquarters and major facilities Apple Inc.'s world corporate headquarters are located in Cupertino, in the middle of California's Silicon Valley, at Apple Park, a massive circular groundscraper building with a circumference of . The building opened in April 2017 and houses more than 12,000 employees. Apple co-founder Steve Jobs wanted Apple Park to look less like a business park and more like a nature refuge, and personally appeared before the Cupertino City Council in June 2011 to make the proposal, in his final public appearance before his death. Apple also operates from the Apple Campus (also known by its address, 1 Infinite Loop), a grouping of six buildings in Cupertino that total located about to the west of Apple Park. The Apple Campus was the company's headquarters from its opening in 1993, until the opening of Apple Park in 2017. The buildings, located at 1–6 Infinite Loop, are arranged in a circular pattern around a central green space, in a design that has been compared to that of a university. In addition to Apple Park and the Apple Campus, Apple occupies an additional thirty office buildings scattered throughout the city of Cupertino, including three buildings that also served as prior headquarters: "Stephens Creek Three" (1977–1978), Bandley One" (1978–1982), and "Mariani One" (1982–1993). In total, Apple occupies almost 40% of the available office space in the city. Apple's headquarters for Europe, the Middle East and Africa (EMEA) are located in Cork in the south of Ireland, called the Hollyhill campus. The facility, which opened in 1980, houses 5,500 people and was Apple's first location outside of the United States. Apple's international sales and distribution arms operate out of the campus in Cork. Apple has two campuses near Austin, Texas: a campus opened in 2014 houses 500 engineers who work on Apple silicon and a campus opened in 2021 where 6,000 people to work in technical support, supply chain management, online store curation, and Apple Maps data management. The company, also has several other locations in Boulder, Colo., Culver City, Calif., Herzliya (Israel), London, New York, Pittsburgh, San Diego and Seattle that each employ hundreds of people. Stores The first Apple Stores were originally opened as two locations in May 2001 by then-CEO Steve Jobs, after years of attempting but failing store-within-a-store concepts. Seeing a need for improved retail presentation of the company's products, he began an effort in 1997 to revamp the retail program to get an improved relationship to consumers, and hired Ron Johnson in 2000. Jobs relaunched Apple's online store in 1997, and opened the first two physical stores in 2001. The media initially speculated that Apple would fail, but its stores were highly successful, bypassing the sales numbers of competing nearby stores and within three years reached US$1 billion in annual sales, becoming the fastest retailer in history to do so. Over the years, Apple has expanded the number of retail locations and its geographical coverage, with 499 stores across 22 countries worldwide . Strong product sales have placed Apple among the top-tier retail stores, with sales over $16 billion globally in 2011. In May 2016, Angela Ahrendts, Apple's then Senior Vice President of Retail, unveiled a significantly redesigned Apple Store in Union Square, San Francisco, featuring large glass doors for the entry, open spaces, and re-branded rooms. In addition to purchasing products, consumers can get advice and help from "Creative Pros" – individuals with specialized knowledge of creative arts; get product support in a tree-lined Genius Grove; and attend sessions, conferences and community events, with Ahrendts commenting that the goal is to make Apple Stores into "town squares", a place where people naturally meet up and spend time. The new design will be applied to all Apple Stores worldwide, a process that has seen stores temporarily relocate or close. Many Apple Stores are located inside shopping malls, but Apple has built several stand-alone "flagship" stores in high-profile locations. It has been granted design patents and received architectural awards for its stores' designs and construction, specifically for its use of glass staircases and cubes. The success of Apple Stores have had significant influence over other consumer electronics retailers, who have lost traffic, control and profits due to a perceived higher quality of service and products at Apple Stores. Apple's notable brand loyalty among consumers causes long lines of hundreds of people at new Apple Store openings or product releases. Due to the popularity of the brand, Apple receives a large number of job applications, many of which come from young workers. Although Apple Store employees receive above-average pay, are offered money toward education and health care, and receive product discounts, there are limited or no paths of career advancement. A May 2016 report with an anonymous retail employee highlighted a hostile work environment with harassment from customers, intense internal criticism, and a lack of significant bonuses for securing major business contracts. Due to the COVID-19 pandemic, Apple closed its stores outside China until March 27, 2020. Despite the stores being closed, hourly workers continue to be paid. Workers across the company are allowed to work remotely if their jobs permit it. On March 24, 2020, in a memo, Senior Vice President of People and Retail Deirdre O’Brien announced that some of its retail stores are expected to reopen at the beginning of April. Corporate affairs Corporate culture Apple is one of several highly successful companies founded in the 1970s that bucked the traditional notions of corporate culture. Jobs often walked around the office barefoot even after Apple became a Fortune 500 company. By the time of the "1984" television advertisement, Apple's informal culture had become a key trait that differentiated it from its competitors. According to a 2011 report in Fortune, this has resulted in a corporate culture more akin to a startup rather than a multinational corporation. In a 2017 interview, Wozniak credited watching Star Trek and attending Star Trek conventions while in his youth as a source of inspiration for his co-founding Apple. As the company has grown and been led by a series of differently opinionated chief executives, it has arguably lost some of its original character. Nonetheless, it has maintained a reputation for fostering individuality and excellence that reliably attracts talented workers, particularly after Jobs returned to the company. Numerous Apple employees have stated that projects without Jobs's involvement often took longer than projects with it. To recognize the best of its employees, Apple created the Apple Fellows program which awards individuals who make extraordinary technical or leadership contributions to personal computing while at the company. The Apple Fellowship has so far been awarded to individuals including Bill Atkinson, Steve Capps, Rod Holt, Alan Kay, Guy Kawasaki, Al Alcorn, Don Norman, Rich Page, Steve Wozniak, and Phil Schiller. At Apple, employees are intended to be specialists who are not exposed to functions outside their area of expertise. Jobs saw this as a means of having "best-in-class" employees in every role. For instance, Ron Johnson—Senior Vice President of Retail Operations until November 1, 2011—was responsible for site selection, in-store service, and store layout, yet had no control of the inventory in his stores. This was done by Tim Cook, who had a background in supply-chain management. Apple is known for strictly enforcing accountability. Each project has a "directly responsible individual" or "DRI" in Apple jargon. As an example, when iOS senior vice president Scott Forstall refused to sign Apple's official apology for numerous errors in the redesigned Maps app, he was forced to resign. Unlike other major U.S. companies, Apple provides a relatively simple compensation policy for executives that does not include perks enjoyed by other CEOs like country club fees or private use of company aircraft. The company typically grants stock options to executives every other year. In 2015, Apple had 110,000 full-time employees. This increased to 116,000 full-time employees the next year, a notable hiring decrease, largely due to its first revenue decline. Apple does not specify how many of its employees work in retail, though its 2014 SEC filing put the number at approximately half of its employee base. In September 2017, Apple announced that it had over 123,000 full-time employees. Apple has a strong culture of corporate secrecy, and has an anti-leak Global Security team that recruits from the National Security Agency, the Federal Bureau of Investigation, and the United States Secret Service. In December 2017, Glassdoor said Apple was the 48th best place to work, having originally entered at rank 19 in 2009, peaking at rank 10 in 2012, and falling down the ranks in subsequent years. Lack of innovation An editorial article in The Verge in September 2016 by technology journalist Thomas Ricker explored some of the public's perceived lack of innovation at Apple in recent years, specifically stating that Samsung has "matched and even surpassed Apple in terms of smartphone industrial design" and citing the belief that Apple is incapable of producing another breakthrough moment in technology with its products. He goes on to write that the criticism focuses on individual pieces of hardware rather than the ecosystem as a whole, stating "Yes, iteration is boring. But it's also how Apple does business. [...] It enters a new market and then refines and refines and continues refining until it yields a success". He acknowledges that people are wishing for the "excitement of revolution", but argues that people want "the comfort that comes with harmony". Furthermore, he writes that "a device is only the starting point of an experience that will ultimately be ruled by the ecosystem in which it was spawned", referring to how decent hardware products can still fail without a proper ecosystem (specifically mentioning that Walkman did not have an ecosystem to keep users from leaving once something better came along), but how Apple devices in different hardware segments are able to communicate and cooperate through the iCloud cloud service with features including Universal Clipboard (in which text copied on one device can be pasted on a different device) as well as inter-connected device functionality including Auto Unlock (in which an Apple Watch can unlock a Mac in close proximity). He argues that Apple's ecosystem is its greatest innovation. The Wall Street Journal reported in June 2017 that Apple's increased reliance on Siri, its virtual personal assistant, has raised questions about how much Apple can actually accomplish in terms of functionality. Whereas Google and Amazon make use of big data and analyze customer information to personalize results, Apple has a strong pro-privacy stance, intentionally not retaining user data. "Siri is a textbook of leading on something in tech and then losing an edge despite having all the money and the talent and sitting in Silicon Valley", Holger Mueller, a technology analyst, told the Journal. The report further claims that development on Siri has suffered due to team members and executives leaving the company for competitors, a lack of ambitious goals, and shifting strategies. Though switching Siri's functions to machine learning and algorithms, which dramatically cut its error rate, the company reportedly still failed to anticipate the popularity of Amazon's Echo, which features the Alexa personal assistant. Improvements to Siri stalled, executives clashed, and there were disagreements over the restrictions imposed on third-party app interactions. While Apple acquired an England-based startup specializing in conversational assistants, Google's Assistant had already become capable of helping users select Wi-Fi networks by voice, and Siri was lagging in functionality. In December 2017, two articles from The Verge and ZDNet debated what had been a particularly devastating week for Apple's macOS and iOS software platforms. The former had experienced a severe security vulnerability, in which Macs running the then-latest macOS High Sierra software were vulnerable to a bug that let anyone gain administrator privileges by entering "root" as the username in system prompts, leaving the password field empty and twice clicking "unlock", gaining full access. The bug was publicly disclosed on Twitter, rather than through proper bug bounty programs. Apple released a security fix within a day and issued an apology, stating that "regrettably we stumbled" in regards to the security of the latest updates. After installing the security patch, however, file sharing was broken for users, with Apple releasing a support document with instructions to separately fix that issue. Though Apple publicly stated the promise of "auditing our development processes to help prevent this from happening again", users who installed the security update while running the older 10.13.0 version of the High Sierra operating system rather than the then-newest 10.13.1 release experienced that the "root" security vulnerability was re-introduced, and persisted even after fully updating their systems. On iOS, a date bug caused iOS devices that received local app notifications at 12:15am on December 2, 2017, to repeatedly restart. Users were recommended to turn off notifications for their apps. Apple quickly released an update, done during the nighttime in Cupertino, California time and outside of their usual software release window, with one of the headlining features of the update needing to be delayed for a few days. The combined problems of the week on both macOS and iOS caused The Verges Tom Warren to call it a "nightmare" for Apple's software engineers and described it as a significant lapse in Apple's ability to protect its more than 1 billion devices. ZDNets Adrian Kingsley-Hughes wrote that "it's hard to not come away from the last week with the feeling that Apple is slipping". Kingsley-Hughes also concluded his piece by referencing an earlier article, in which he wrote that "As much as I don't want to bring up the tired old 'Apple wouldn't have done this under Steve Jobs's watch' trope, a lot of what's happening at Apple lately is different from what they came to expect under Jobs. Not to say that things didn't go wrong under his watch, but product announcements and launches felt a lot tighter for sure, as did the overall quality of what Apple was releasing." He did, however, also acknowledge that such failures "may indeed have happened" with Jobs in charge, though returning to the previous praise for his demands of quality, stating "it's almost guaranteed that given his personality that heads would have rolled, which limits future failures". Manufacturing and assembling The company's manufacturing, procurement, and logistics enable it to execute massive product launches without having to maintain large, profit-sapping inventories. In 2011, Apple's profit margins were 40 percent, compared with between 10 and 20 percent for most other hardware companies. Cook's catchphrase to describe his focus on the company's operational arm is: "Nobody wants to buy sour milk". In May 2017, the company announced a $1 billion funding project for "advanced manufacturing" in the United States, and subsequently invested $200 million in Corning Inc., a manufacturer of toughened Gorilla Glass technology used in its iPhone devices. The following December, Apple's chief operating officer, Jeff Williams, told CNBC that the "$1 billion" amount was "absolutely not" the final limit on its spending, elaborating that "We're not thinking in terms of a fund limit. ... We're thinking about, where are the opportunities across the U.S. to help nurture companies that are making the advanced technology — and the advanced manufacturing that goes with that — that quite frankly is essential to our innovation". As of 2021, Apple uses components from 43 different countries. The majority of assembling is done by Taiwanese original design manufacturer firms Foxconn, Pegatron, Wistron and Compal Electronics mostly in factories located inside China, but also Brazil, and India. During the Mac's early history Apple generally refused to adopt prevailing industry standards for hardware, instead creating their own. This trend was largely reversed in the late 1990s, beginning with Apple's adoption of the PCI bus in the 7500/8500/9500 Power Macs. Apple has since joined the industry standards groups to influence the future direction of technology standards such as USB, AGP, HyperTransport, Wi-Fi, NVMe, PCIe and others in its products. FireWire is an Apple-originated standard that was widely adopted across the industry after it was standardized as IEEE 1394 and is a legally mandated port in all Cable TV boxes in the United States. Apple has gradually expanded its efforts in getting its products into the Indian market. In July 2012, during a conference call with investors, CEO Tim Cook said that he "[loves] India", but that Apple saw larger opportunities outside the region. India's requirement that 30% of products sold be manufactured in the country was described as "really adds cost to getting product to market". In May 2016, Apple opened an iOS app development center in Bangalore and a maps development office for 4,000 staff in Hyderabad. In March, The Wall Street Journal reported that Apple would begin manufacturing iPhone models in India "over the next two months", and in May, the Journal wrote that an Apple manufacturer had begun production of iPhone SE in the country, while Apple told CNBC that the manufacturing was for a "small number" of units. In April 2019, Apple initiated manufacturing of iPhone 7 at its Bengaluru facility, keeping in mind demand from local customers even as they seek more incentives from the government of India. At the beginning of 2020, Tim Cook announced that Apple schedules the opening of its first physical outlet in India for 2021, while an online store is to be launched by the end of the year. Labor practices The company advertised its products as being made in America until the late 1990s; however, as a result of outsourcing initiatives in the 2000s, almost all of its manufacturing is now handled abroad. According to a report by The New York Times, Apple insiders "believe the vast scale of overseas factories, as well as the flexibility, diligence and industrial skills of foreign workers, have so outpaced their American counterparts that "Made in the USA" is no longer a viable option for most Apple products". In 2006, one complex of factories in Shenzhen, China that assembled the iPod and other items had over 200,000 workers living and working within it. Employees regularly worked more than 60 hours per week and made around $100 per month. A little over half of the workers' earnings was required to pay for rent and food from the company. Apple immediately launched an investigation after the 2006 media report, and worked with their manufacturers to ensure acceptable working conditions. In 2007, Apple started yearly audits of all its suppliers regarding worker's rights, slowly raising standards and pruning suppliers that did not comply. Yearly progress reports have been published since 2008. In 2011, Apple admitted that its suppliers' child labor practices in China had worsened. The Foxconn suicides occurred between January and November 2010, when 18 Foxconn (Chinese: 富士康) employees attempted suicide, resulting in 14 deaths—the company was the world's largest contract electronics manufacturer, for clients including Apple, at the time. The suicides drew media attention, and employment practices at Foxconn were investigated by Apple. Apple issued a public statement about the suicides, and company spokesperson Steven Dowling said: The statement was released after the results from the company's probe into its suppliers' labor practices were published in early 2010. Foxconn was not specifically named in the report, but Apple identified a series of serious labor violations of labor laws, including Apple's own rules, and some child labor existed in a number of factories. Apple committed to the implementation of changes following the suicides. Also in 2010, workers in China planned to sue iPhone contractors over poisoning by a cleaner used to clean LCD screens. One worker claimed that he and his coworkers had not been informed of possible occupational illnesses. After a high suicide rate in a Foxconn facility in China making iPads and iPhones, albeit a lower rate than that of China as a whole, workers were forced to sign a legally binding document guaranteeing that they would not kill themselves. Workers in factories producing Apple products have also been exposed to hexane, a neurotoxin that is a cheaper alternative than alcohol for cleaning the products. A 2014 BBC investigation found excessive hours and other problems persisted, despite Apple's promise to reform factory practice after the 2010 Foxconn suicides. The Pegatron factory was once again the subject of review, as reporters gained access to the working conditions inside through recruitment as employees. While the BBC maintained that the experiences of its reporters showed that labor violations were continuing since 2010, Apple publicly disagreed with the BBC and stated: "We are aware of no other company doing as much as Apple to ensure fair and safe working conditions". In December 2014, the Institute for Global Labour and Human Rights published a report which documented inhumane conditions for the 15,000 workers at a Zhen Ding Technology factory in Shenzhen, China, which serves as a major supplier of circuit boards for Apple's iPhone and iPad. According to the report, workers are pressured into 65-hour work weeks which leaves them so exhausted that they often sleep during lunch breaks. They are also made to reside in "primitive, dark and filthy dorms" where they sleep "on plywood, with six to ten workers in each crowded room." Omnipresent security personnel also routinely harass and beat the workers. In 2019, there were reports stating that some of Foxconn's managers had used rejected parts to build iPhones and that Apple was investigating the issue. Environmental practices and initiatives Apple Energy Apple Energy, LLC is a wholly owned subsidiary of Apple Inc. that sells solar energy. , Apple's solar farms in California and Nevada have been declared to provide 217.9 megawatts of solar generation capacity. In addition to the company's solar energy production, Apple has received regulatory approval to construct a landfill gas energy plant in North Carolina. Apple will use the methane emissions to generate electricity. Apple's North Carolina data center is already powered entirely with energy from renewable sources. Energy and resources Following a Greenpeace protest, Apple released a statement on April 17, 2012, committing to ending its use of coal and shifting to 100% renewable clean energy. By 2013, Apple was using 100% renewable energy to power their data centers. Overall, 75% of the company's power came from clean renewable sources. In 2010, Climate Counts, a nonprofit organization dedicated to directing consumers toward the greenest companies, gave Apple a score of 52 points out of a possible 100, which puts Apple in their top category "Striding". This was an increase from May 2008, when Climate Counts only gave Apple 11 points out of 100, which placed the company last among electronics companies, at which time Climate Counts also labeled Apple with a "stuck icon", adding that Apple at the time was "a choice to avoid for the climate-conscious consumer". In May 2015, Greenpeace evaluated the state of the Green Internet and commended Apple on their environmental practices saying, "Apple's commitment to renewable energy has helped set a new bar for the industry, illustrating in very concrete terms that a 100% renewable Internet is within its reach, and providing several models of intervention for other companies that want to build a sustainable Internet." , Apple states that 100% of its U.S. operations run on renewable energy, 100% of Apple's data centers run on renewable energy and 93% of Apple's global operations run on renewable energy. However, the facilities are connected to the local grid which usually contains a mix of fossil and renewable sources, so Apple carbon offsets its electricity use. The Electronic Product Environmental Assessment Tool (EPEAT) allows consumers to see the effect a product has on the environment. Each product receives a Gold, Silver, or Bronze rank depending on its efficiency and sustainability. Every Apple tablet, notebook, desktop computer, and display that EPEAT ranks achieves a Gold rating, the highest possible. Although Apple's data centers recycle water 35 times, the increased activity in retail, corporate and data centers also increase the amount of water use to in 2015. During an event on March 21, 2016, Apple provided a status update on its environmental initiative to be 100% renewable in all of its worldwide operations. Lisa P. Jackson, Apple's vice president of Environment, Policy and Social Initiatives who reports directly to CEO, Tim Cook, announced that , 93% of Apple's worldwide operations are powered with renewable energy. Also featured was the company's efforts to use sustainable paper in their product packaging; 99% of all paper used by Apple in the product packaging comes from post-consumer recycled paper or sustainably managed forests, as the company continues its move to all paper packaging for all of its products. Apple working in partnership with Conservation Fund, have preserved 36,000 acres of working forests in Maine and North Carolina. Another partnership announced is with the World Wildlife Fund to preserve up to of forests in China. Featured was the company's installation of a 40 MW solar power plant in the Sichuan province of China that was tailor-made to coexist with the indigenous yaks that eat hay produced on the land, by raising the panels to be several feet off of the ground so the yaks and their feed would be unharmed grazing beneath the array. This installation alone compensates for more than all of the energy used in Apple's Stores and Offices in the whole of China, negating the company's energy carbon footprint in the country. In Singapore, Apple has worked with the Singaporean government to cover the rooftops of 800 buildings in the city-state with solar panels allowing Apple's Singapore operations to be run on 100% renewable energy. Liam was introduced to the world, an advanced robotic disassembler and sorter designed by Apple Engineers in California specifically for recycling outdated or broken iPhones. Reuses and recycles parts from traded in products. Apple announced on August 16, 2016, that Lens Technology, one of its major suppliers in China, has committed to power all its glass production for Apple with 100 percent renewable energy by 2018. The commitment is a large step in Apple's efforts to help manufacturers lower their carbon footprint in China. Apple also announced that all 14 of its final assembly sites in China are now compliant with UL's Zero Waste to Landfill validation. The standard, which started in January 2015, certifies that all manufacturing waste is reused, recycled, composted, or converted into energy (when necessary). Since the program began, nearly, 140,000 metric tons of waste have been diverted from landfills. On July 21, 2020, Apple announced its plan to become carbon neutral across its entire business, manufacturing supply chain, and product life cycle by 2030. In the next 10 years, Apple will try to lower emissions with a series of innovative actions, including: low carbon product design, expanding energy efficiency, renewable energy, process and material innovations, and carbon removal. In April 2021, Apple said that it had started a $200 million fund in order to combat climate change by removing 1 million metric tons of carbon dioxide from the atmosphere each year. Toxins Following further campaigns by Greenpeace, in 2008, Apple became the first electronics manufacturer to fully eliminate all polyvinyl chloride (PVC) and brominated flame retardants (BFRs) in its complete product line. In June 2007, Apple began replacing the cold cathode fluorescent lamp (CCFL) backlit LCD displays in its computers with mercury-free LED-backlit LCD displays and arsenic-free glass, starting with the upgraded MacBook Pro. Apple offers comprehensive and transparent information about the CO2e, emissions, materials, and electrical usage concerning every product they currently produce or have sold in the past (and which they have enough data needed to produce the report), in their portfolio on their homepage. Allowing consumers to make informed purchasing decisions on the products they offer for sale. In June 2009, Apple's iPhone 3GS was free of PVC, arsenic, and BFRs. All Apple products now have mercury-free LED-backlit LCD displays, arsenic-free glass, and non-PVC cables. All Apple products have EPEAT Gold status and beat the latest Energy Star guidelines in each product's respective regulatory category. In November 2011, Apple was featured in Greenpeace's Guide to Greener Electronics, which ranks electronics manufacturers on sustainability, climate and energy policy, and how "green" their products are. The company ranked fourth of fifteen electronics companies (moving up five places from the previous year) with a score of 4.6/10. Greenpeace praises Apple's sustainability, noting that the company exceeded its 70% global recycling goal in 2010. It continues to score well on the products rating with all Apple products now being free of PVC plastic and BFRs. However, the guide criticizes Apple on the Energy criteria for not seeking external verification of its greenhouse gas emissions data and for not setting out any targets to reduce emissions. In January 2012, Apple requested that its cable maker, Volex, begin producing halogen-free USB and power cables. Green bonds In February 2016, Apple issued a US$1.5 billion green bond (climate bond), the first ever of its kind by a U.S. tech company. The green bond proceeds are dedicated to the financing of environmental projects. Racial Justice and Equality Initiatives In June 2020, Apple committed $100 million for its Racial Equity and Justice initiative (REJI) and in Jan 2021 announced various projects as part of the initiative. Finance Apple is the world's largest information technology company by revenue, the world's largest technology company by total assets, and the world's second-largest mobile phone manufacturer after Samsung. In its fiscal year ending in September 2011, Apple Inc. reported a total of $108 billion in annual revenues—a significant increase from its 2010 revenues of $65 billion—and nearly $82 billion in cash reserves. On March 19, 2012, Apple announced plans for a $2.65-per-share dividend beginning in fourth quarter of 2012, per approval by their board of directors. The company's worldwide annual revenue in 2013 totaled $170 billion. In May 2013, Apple entered the top ten of the Fortune 500 list of companies for the first time, rising 11 places above its 2012 ranking to take the sixth position. , Apple has around US$234 billion of cash and marketable securities, of which 90% is located outside the United States for tax purposes. Apple amassed 65% of all profits made by the eight largest worldwide smartphone manufacturers in quarter one of 2014, according to a report by Canaccord Genuity. In the first quarter of 2015, the company garnered 92% of all earnings. On April 30, 2017, The Wall Street Journal reported that Apple had cash reserves of $250 billion, officially confirmed by Apple as specifically $256.8 billion a few days later. , Apple was the largest publicly traded corporation in the world by market capitalization. On August 2, 2018, Apple became the first publicly traded U.S. company to reach a $1 trillion market value. Apple was ranked No. 4 on the 2018 Fortune 500 rankings of the largest United States corporations by total revenue. Tax practices Apple has created subsidiaries in low-tax places such as Ireland, the Netherlands, Luxembourg, and the British Virgin Islands to cut the taxes it pays around the world. According to The New York Times, in the 1980s Apple was among the first tech companies to designate overseas salespeople in high-tax countries in a manner that allowed the company to sell on behalf of low-tax subsidiaries on other continents, sidestepping income taxes. In the late 1980s, Apple was a pioneer of an accounting technique known as the "Double Irish with a Dutch sandwich," which reduces taxes by routing profits through Irish subsidiaries and the Netherlands and then to the Caribbean. British Conservative Party Member of Parliament Charlie Elphicke published research on October 30, 2012, which showed that some multinational companies, including Apple Inc., were making billions of pounds of profit in the UK, but were paying an effective tax rate to the UK Treasury of only 3 percent, well below standard corporation tax. He followed this research by calling on the Chancellor of the Exchequer George Osborne to force these multinationals, which also included Google and The Coca-Cola Company, to state the effective rate of tax they pay on their UK revenues. Elphicke also said that government contracts should be withheld from multinationals who do not pay their fair share of UK tax. Apple Inc. claims to be the single largest taxpayer to the Department of the Treasury of the United States of America with an effective tax rate of approximately of 26% as of the second quarter of the Apple fiscal year 2016. In an interview with the German newspaper FAZ in October 2017, Tim Cook stated, that Apple is the biggest taxpayer worldwide. In 2015, Reuters reported that Apple had earnings abroad of $54.4 billion which were untaxed by the IRS of the United States. Under U.S. tax law governed by the IRC, corporations don't pay income tax on overseas profits unless the profits are repatriated into the United States and as such Apple argues that to benefit its shareholders it will leave it overseas until a repatriation holiday or comprehensive tax reform takes place in the United States. On July 12, 2016, the Central Statistics Office of Ireland announced that 2015 Irish GDP had grown by 26.3%, and 2015 Irish GNP had grown by 18.7%. The figures attracted international scorn, and were labelled by Nobel-prize winning economist, Paul Krugman, as leprechaun economics. It was not until 2018 that Irish economists could definitively prove that the 2015 growth was due to Apple restructuring its controversial double Irish subsidiaries (Apple Sales International), which Apple converted into a new Irish capital allowances for intangible assets tax scheme (expires in January 2020). The affair required the Central Bank of Ireland to create a new measure of Irish economic growth, Modified GNI* to replace Irish GDP, given the distortion of Apple's tax schemes. Irish GDP is 143% of Irish Modified GNI*. On August 30, 2016, after a two-year investigation, the EU Competition Commissioner concluded Apple received "illegal state aid" from Ireland. The EU ordered Apple to pay 13 billion euros ($14.5 billion), plus interest, in unpaid Irish taxes for 2004–2014. It is the largest tax fine in history. The Commission found that Apple had benefited from a private Irish Revenue Commissioners tax ruling regarding its double Irish tax structure, Apple Sales International (ASI). Instead of using two companies for its double Irish structure, Apple was given a ruling to split ASI into two internal "branches". The Chancellor of Austria, Christian Kern, put this decision into perspective by stating that "every Viennese cafe, every sausage stand pays more tax in Austria than a multinational corporation". , Apple agreed to start paying €13 billion in back taxes to the Irish government, the repayments will be held in an escrow account while Apple and the Irish government continue their appeals in EU courts. On July 15, 2020, the EU General Court annuls the European Commission's decision in Apple State aid case: Apple will not have to repay €13 billion to Ireland. Board of directors the following individuals sit on the board of Apple Inc. Arthur D. Levinson (chairman) Tim Cook (executive director and CEO) James A. Bell (non-executive director) Al Gore (non-executive director) Andrea Jung (non-executive director) Ronald Sugar (non-executive director) Susan Wagner (non-executive director) Executive management the management of Apple Inc. includes: Tim Cook (chief executive officer) Jeff Williams (chief operating officer) Luca Maestri (senior vice president and chief financial officer) Katherine L. Adams (senior vice president and general counsel) Eddy Cue (senior vice president – Internet Software and Services) Craig Federighi (senior vice president – Software Engineering) John Giannandrea (senior vice president – Machine Learning and AI Strategy) Deirdre O'Brien (senior vice president – Retail + People) John Ternus (senior vice president – Hardware Engineering) Greg Josiwak (senior vice president – Worldwide Marketing) Johny Srouji (senior vice president – Hardware Technologies) Sabih Khan (senior vice president – Operations) Lisa P. Jackson (vice president – Environment, Policy, and Social Initiatives) Isabel Ge Mahe (vice president and managing director – Greater China) Tor Myhren (vice president – Marketing Communications) Adrian Perica (vice president – Corporate Development) List of chief executives Michael Scott (1977–1981) Mike Markkula (1981–1983) John Sculley (1983–1993) Michael Spindler (1993–1996) Gil Amelio (1996–1997) Steve Jobs (1997–2011) Tim Cook (2011–present) List of chairmen The role of chairman of the Board has not always been in use; notably, between 1981 to 1985, and 1997 to 2011. Mike Markkula (1977–1981) Steve Jobs (1985) Mike Markkula (1985–1993); second term John Sculley (1993) Mike Markkula (1993–1997); third term Steve Jobs (2011); second term Arthur D. Levinson (2011–present) Litigation Apple has been a participant in various legal proceedings and claims since it began operation. In particular, Apple is known for and promotes itself as actively and aggressively enforcing its intellectual property interests. Some litigation examples include Apple v. Samsung, Apple v. Microsoft, Motorola Mobility v. Apple Inc., and Apple Corps v. Apple Computer. Apple has also had to defend itself against charges on numerous occasions of violating intellectual property rights. Most have been dismissed in the courts as shell companies known as patent trolls, with no evidence of actual use of patents in question. On December 21, 2016, Nokia announced that in the U.S. and Germany, it has filed a suit against Apple, claiming that the latter's products infringe on Nokia's patents. Most recently, in November 2017, the United States International Trade Commission announced an investigation into allegations of patent infringement in regards to Apple's remote desktop technology; Aqua Connect, a company that builds remote desktop software, has claimed that Apple infringed on two of its patents. Privacy stance Apple has a notable pro-privacy stance, actively making privacy-conscious features and settings part of its conferences, promotional campaigns, and public image. With its iOS 8 mobile operating system in 2014, the company started encrypting all contents of iOS devices through users' passcodes, making it impossible at the time for the company to provide customer data to law enforcement requests seeking such information. With the popularity rise of cloud storage solutions, Apple began a technique in 2016 to do deep learning scans for facial data in photos on the user's local device and encrypting the content before uploading it to Apple's iCloud storage system. It also introduced "differential privacy", a way to collect crowdsourced data from many users, while keeping individual users anonymous, in a system that Wired described as "trying to learn as much as possible about a group while learning as little as possible about any individual in it". Users are explicitly asked if they want to participate, and can actively opt-in or opt-out. With Apple's release of an update to iOS 14, Apple required all developers of iPhone, iPad, and iPod touch applications to directly ask iPhone users permission to track them. The feature, titled "App Tracking Transparency", received heavy criticism from Facebook, whose primary business model revolves around the tracking of users' data and sharing such data with advertisers so users can see more relevant ads, a technique commonly known as targeted advertising. Despite Facebook's measures, including purchasing full-page newspaper advertisements protesting App Tracking Transparency, Apple released the update in mid-spring 2021. A study by Verizon subsidiary Flurry Analytics reported only 4% of iOS users in the United States and 12% worldwide have opted into tracking. However, Apple aids law enforcement in criminal investigations by providing iCloud backups of users' devices, and the company's commitment to privacy has been questioned by its efforts to promote biometric authentication technology in its newer iPhone models, which don't have the same level of constitutional privacy as a passcode in the United States. Prior to the release of iOS 15, Apple announced new efforts at combating child sexual abuse material on iOS and Mac platforms. Parents of minor iMessage users can now be alerted if their child sends or receives nude photographs. Additionally, on-device hashing would take place on media destined for upload to iCloud, and hashes would be compared to a list of known abusive images provided by law enforcement; if enough matches were found, Apple would be alerted and authorities informed. The new features received praise from law enforcement and victims rights advocates, however privacy advocates, including the Electronic Frontier Foundation, condemned the new features as invasive and highly prone to abuse by authoritarian governments. Charitable causes Apple is a partner of (PRODUCT)RED, a fundraising campaign for AIDS charity. In November 2014, Apple arranged for all App Store revenue in a two-week period to go to the fundraiser, generating more than US$20 million, and in March 2017, it released an iPhone 7 with a red color finish. Apple contributes financially to fundraisers in times of natural disasters. In November 2012, it donated $2.5 million to the American Red Cross to aid relief efforts after Hurricane Sandy, and in 2017 it donated $5 million to relief efforts for both Hurricane Irma and Hurricane Harvey, as well as for the 2017 Central Mexico earthquake. The company has also used its iTunes platform to encourage donations in the wake of environmental disasters and humanitarian crises, such as the 2010 Haiti earthquake, the 2011 Japan earthquake, Typhoon Haiyan in the Philippines in November 2013, and the 2015 European migrant crisis. Apple emphasizes that it does not incur any processing or other fees for iTunes donations, sending 100% of the payments directly to relief efforts, though it also acknowledges that the Red Cross does not receive any personal information on the users donating and that the payments may not be tax deductible. On April 14, 2016, Apple and the World Wide Fund for Nature (WWF) announced that they have engaged in a partnership to, "help protect life on our planet." Apple released a special page in the iTunes App Store, Apps for Earth. In the arrangement, Apple has committed that through April 24, WWF will receive 100% of the proceeds from the applications participating in the App Store via both the purchases of any paid apps and the In-App Purchases. Apple and WWF's Apps for Earth campaign raised more than $8 million in total proceeds to support WWF's conservation work. WWF announced the results at WWDC 2016 in San Francisco. During the COVID-19 pandemic, Apple's CEO Cook announced that the company will be donating "millions" of masks to health workers in the United States and Europe. On January 13, 2021, Apple announced a $100 million "Racial Equity and Justice Initiative" to help combat institutional racism worldwide. Criticism and controversies Apple has been criticized for alleged unethical business practices such as anti-competitive behavior, rash litigation, dubious tax tactics, production methods involving the use of sweatshop labor, customer service issues involving allegedly misleading warranties and insufficient data security, and its products' environmental footprint. Apple has also received criticism for its willingness to work and conduct business with nations such as China and Russia, engaging in practices that have been criticized by human rights groups. Critics have claimed that Apple products combine stolen or purchased designs that Apple claims are its original creations. It has been criticized for its alleged collaboration with the U.S. surveillance program PRISM. The company denied any collaboration. Products and services Apple's issues regarding music over the years include those with the European Union regarding iTunes, trouble over updating the Spotify app on Apple devices and collusion with record labels. In 2018–19, Apple faced criticism for its failure to approve NVIDIA web drivers for GPUs installed on legacy Mac Pro machines (up to mid 2012 5,1 running macOS Mojave 10.14). Without access to Apple-approved NVIDIA web drivers, Apple users faced replacing their NVIDIA cards with graphic cards produced by supported brands (such as the AMD Radeon), from a list of recommendations provided by Apple to its consumers. In June 2019, Apple issued a recall for its 2015 MacBook Pro Retina 15" following reports of batteries catching fire. The recall affected 432,000 units, and Apple was criticized for the long waiting periods consumers experienced, sometimes extending up to 3 weeks for replacements to arrive; the company also did not provide alternative replacements or repair options. In July 2019, following a campaign by the "right to repair" movement, challenging Apple's tech repair restrictions on devices, the FTC held a workshop to establish the framework of a future nationwide Right to Repair rule. The movement argues Apple is preventing consumers from legitimately fixing their devices at local repair shops which is having a negative impact on consumers. On November 19, 2020, it was announced that Apple will be paying out $113 million related to lawsuits stemming from their iPhone's battery problems and subsequent performance slow-downs. Apple continues to face litigation related to the performance throttling of iPhone 6 and 7 devices, an action that Apple argued was done in order to balance the functionality of the software with the impacts of a chemically aged battery. On January 25, 2021, Apple was hit with another lawsuit from an Italian consumer group, with more groups to follow, despite the rationale for the throttling. On November 30, 2020, the Italian antitrust authority AGCM fined Apple $12 million for misleading trade practices. AGCM stated that Apple's claims of the iPhone's water resistance weren't true as the phones could only resist water up to 4 meters deep in ideal laboratory conditions and not in regular circumstances. The authority added that Apple provided no assistance to customers with water-damaged phones, which it said constituted an aggressive trade practice. Privacy Ireland's Data Protection Commission also launched a privacy investigation to examine whether Apple complied with the EU's GDPR law following an investigation into how the company processes personal data with targeted ads on its platform. In December 2019, a report found that the iPhone 11 Pro continues tracking location and collecting user data even after users have disabled location services. In response, an Apple engineer said the Location Services icon "appears for system services that do not have a switch in settings." Antitrust The United States Department of Justice also began a review of Big Tech firms to establish whether they could be unlawfully stifling competition in a broad antitrust probe in 2019. On March 16, 2020, France fined Apple €1.1 billion for colluding with two wholesalers to stifle competition and keep prices high by handicapping independent resellers. The arrangement created aligned prices for Apple products such as iPads and personal computers for about half the French retail market. According to the French regulators, the abuses occurred between 2005 and 2017 but were first discovered after a complaint by an independent reseller, eBizcuss, in 2012. On August 13, 2020, Epic Games, the maker of the popular game Fortnite, sued Apple and Google after its hugely popular video game was removed from Apple and Google's App Store. The suits come after both Apple and Google blocked the game after it introduced a direct payment system, effectively shutting out the tech titans from collecting fees. In September 2020 Epic Games founded the Coalition for App Fairness together with other thirteen companies, which aims for better conditions for the inclusion of apps in the app stores. Later in December 2020, Facebook agreed to assist Epic in their legal game against Apple, planning to support the company by providing materials and documents to Epic. Facebook had, however, stated that the company will not participate directly with the lawsuit, although did commit to helping with the discovery of evidence relating to the trial of 2021. In the months prior to their agreement, Facebook had been dealing with feuds against Apple relating to the prices of paid apps as well as privacy rule changes. Head of ad products for Facebook Dan Levy commented, saying that "this is not really about privacy for them, this is about an attack on personalized ads and the consequences it's going to have on small-business owners," commenting on the full-page ads placed by Facebook in various newspapers in December 2020. Politics In January 2020, US President Donald Trump and attorney general William P. Barr criticized Apple for refusing to unlock two iPhones of a Saudi national, Mohammed Saeed Alshamrani, who shot and killed three American sailors and injured eight others in the Naval Air Station Pensacola. The shooting was declared an "act of terrorism" by the FBI, but Apple denied the request to crack the phones to reveal possible terrorist information citing its data privacy policy. Apple Inc., shareholders increased pressure on the company to publicly commit “to respect freedom of expression as a human right”, upon which Apple committed to freedom of expression and information in its human rights policy document. It said that the policy is based on the guidelines of the United Nations on business and human rights, in early September 2020. In 2021, Apple complied with a request by the Chinese government to ban a Quran app from its devices and platforms. The request occurred in the context of the Chinese government's ongoing mass repression of Muslims, particularly Uyghurs, in Xinjiang, which some have labeled a genocide. In December 2021, The Information reported that CEO Tim Cook had negotiated in 2016 a five-year agreement with the Chinese government, motivated in part to allay regulatory issues that had harmed the company's business in China. The agreement entailed promised investments totaling $275 billion. In September 2021, Apple removed an app from its App Store created by Alexei Navalny meant to coordinate protest voting during the 2021 Russian legislative election. The Russian government had threatened to arrest individual Apple employees working in the country unless Apple complied. Patents In January 2022, Ericsson sued Apple over payment of royalty of 5G technology. See also List of Apple Inc. media events Pixar References Bibliography Further reading External links 1976 establishments in California 1980s initial public offerings American brands Companies based in Cupertino, California Companies in the Dow Jones Industrial Average Companies in the PRISM network Companies listed on the Nasdaq Computer companies established in 1976 Computer companies of the United States Display technology companies Electronics companies of the United States Home computer hardware companies Mobile phone manufacturers Multinational companies headquartered in the United States Networking hardware companies Portable audio player manufacturers Retail companies of the United States Software companies based in the San Francisco Bay Area Software companies established in 1976 Steve Jobs Technology companies based in the San Francisco Bay Area Technology companies established in 1976 Technology companies of the United States

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

874

https://en.wikipedia.org/wiki/Ancient%20Egypt

Ancient Egypt

Ancient Egypt was a civilization of ancient Africa, concentrated along the lower reaches of the Nile River, situated in the place that is now the country Egypt. Ancient Egyptian civilization followed prehistoric Egypt and coalesced around 3100BC (according to conventional Egyptian chronology) with the political unification of Upper and Lower Egypt under Menes (often identified with Narmer). The history of ancient Egypt occurred as a series of stable kingdoms, separated by periods of relative instability known as Intermediate Periods: the Old Kingdom of the Early Bronze Age, the Middle Kingdom of the Middle Bronze Age and the New Kingdom of the Late Bronze Age. Egypt reached the pinnacle of its power in the New Kingdom, ruling much of Nubia and a sizable portion of the Near East, after which it entered a period of slow decline. During the course of its history Egypt was invaded or conquered by a number of foreign powers, including the Hyksos, the Libyans, the Nubians, the Assyrians, the Achaemenid Persians, and the Macedonians under the command of Alexander the Great. The Greek Ptolemaic Kingdom, formed in the aftermath of Alexander's death, ruled Egypt until 30BC, when, under Cleopatra, it fell to the Roman Empire and became a Roman province. The success of ancient Egyptian civilization came partly from its ability to adapt to the conditions of the Nile River valley for agriculture. The predictable flooding and controlled irrigation of the fertile valley produced surplus crops, which supported a more dense population, and social development and culture. With resources to spare, the administration sponsored mineral exploitation of the valley and surrounding desert regions, the early development of an independent writing system, the organization of collective construction and agricultural projects, trade with surrounding regions, and a military intended to assert Egyptian dominance. Motivating and organizing these activities was a bureaucracy of elite scribes, religious leaders, and administrators under the control of a pharaoh, who ensured the cooperation and unity of the Egyptian people in the context of an elaborate system of religious beliefs. The many achievements of the ancient Egyptians include the quarrying, surveying and construction techniques that supported the building of monumental pyramids, temples, and obelisks; a system of mathematics, a practical and effective system of medicine, irrigation systems and agricultural production techniques, the first known planked boats, Egyptian faience and glass technology, new forms of literature, and the earliest known peace treaty, made with the Hittites. Ancient Egypt has left a lasting legacy. Its art and architecture were widely copied, and its antiquities carried off to far corners of the world. Its monumental ruins have inspired the imaginations of travelers and writers for millennia. A newfound respect for antiquities and excavations in the early modern period by Europeans and Egyptians led to the scientific investigation of Egyptian civilization and a greater appreciation of its cultural legacy. History The Nile has been the lifeline of its region for much of human history. The fertile floodplain of the Nile gave humans the opportunity to develop a settled agricultural economy and a more sophisticated, centralized society that became a cornerstone in the history of human civilization. Nomadic modern human hunter-gatherers began living in the Nile valley through the end of the Middle Pleistocene some 120,000 years ago. By the late Paleolithic period, the arid climate of Northern Africa became increasingly hot and dry, forcing the populations of the area to concentrate along the river region. Predynastic period In Predynastic and Early Dynastic times, the Egyptian climate was much less arid than it is today. Large regions of Egypt were covered in treed savanna and traversed by herds of grazing ungulates. Foliage and fauna were far more prolific in all environs and the Nile region supported large populations of waterfowl. Hunting would have been common for Egyptians, and this is also the period when many animals were first domesticated. By about 5500 BC, small tribes living in the Nile valley had developed into a series of cultures demonstrating firm control of agriculture and animal husbandry, and identifiable by their pottery and personal items, such as combs, bracelets, and beads. The largest of these early cultures in upper (Southern) Egypt was the Badarian culture, which probably originated in the Western Desert; it was known for its high-quality ceramics, stone tools, and its use of copper. The Badari was followed by the Naqada culture: the Amratian (Naqada I), the Gerzeh (Naqada II), and Semainean (Naqada III). These brought a number of technological improvements. As early as the Naqada I Period, predynastic Egyptians imported obsidian from Ethiopia, used to shape blades and other objects from flakes. In Naqada II times, early evidence exists of contact with the Near East, particularly Canaan and the Byblos coast. Over a period of about 1,000 years, the Naqada culture developed from a few small farming communities into a powerful civilization whose leaders were in complete control of the people and resources of the Nile valley. Establishing a power center at Nekhen (in Greek, Hierakonpolis), and later at Abydos, Naqada III leaders expanded their control of Egypt northwards along the Nile. They also traded with Nubia to the south, the oases of the western desert to the west, and the cultures of the eastern Mediterranean and Near East to the east, initiating a period of Egypt-Mesopotamia relations. The Naqada culture manufactured a diverse selection of material goods, reflective of the increasing power and wealth of the elite, as well as societal personal-use items, which included combs, small statuary, painted pottery, high quality decorative stone vases, cosmetic palettes, and jewelry made of gold, lapis, and ivory. They also developed a ceramic glaze known as faience, which was used well into the Roman Period to decorate cups, amulets, and figurines. During the last predynastic phase, the Naqada culture began using written symbols that eventually were developed into a full system of hieroglyphs for writing the ancient Egyptian language. Early Dynastic Period (c. 3150–2686 BC) The Early Dynastic Period was approximately contemporary to the early Sumerian-Akkadian civilisation of Mesopotamia and of ancient Elam. The third-centuryBC Egyptian priest Manetho grouped the long line of kings from Menes to his own time into 30 dynasties, a system still used today. He began his official history with the king named "Meni" (or Menes in Greek), who was believed to have united the two kingdoms of Upper and Lower Egypt. The transition to a unified state happened more gradually than ancient Egyptian writers represented, and there is no contemporary record of Menes. Some scholars now believe, however, that the mythical Menes may have been the king Narmer, who is depicted wearing royal regalia on the ceremonial Narmer Palette, in a symbolic act of unification. In the Early Dynastic Period, which began about 3000BC, the first of the Dynastic kings solidified control over lower Egypt by establishing a capital at Memphis, from which he could control the labour force and agriculture of the fertile delta region, as well as the lucrative and critical trade routes to the Levant. The increasing power and wealth of the kings during the early dynastic period was reflected in their elaborate mastaba tombs and mortuary cult structures at Abydos, which were used to celebrate the deified king after his death. The strong institution of kingship developed by the kings served to legitimize state control over the land, labour, and resources that were essential to the survival and growth of ancient Egyptian civilization. Old Kingdom (2686–2181 BC) Major advances in architecture, art, and technology were made during the Old Kingdom, fueled by the increased agricultural productivity and resulting population, made possible by a well-developed central administration. Some of ancient Egypt's crowning achievements, the Giza pyramids and Great Sphinx, were constructed during the Old Kingdom. Under the direction of the vizier, state officials collected taxes, coordinated irrigation projects to improve crop yield, drafted peasants to work on construction projects, and established a justice system to maintain peace and order. With the rising importance of central administration in Egypt, a new class of educated scribes and officials arose who were granted estates by the king in payment for their services. Kings also made land grants to their mortuary cults and local temples, to ensure that these institutions had the resources to worship the king after his death. Scholars believe that five centuries of these practices slowly eroded the economic vitality of Egypt, and that the economy could no longer afford to support a large centralized administration. As the power of the kings diminished, regional governors called nomarchs began to challenge the supremacy of the office of king. This, coupled with severe droughts between 2200 and 2150BC, is believed to have caused the country to enter the 140-year period of famine and strife known as the First Intermediate Period. First Intermediate Period (2181–2055 BC) After Egypt's central government collapsed at the end of the Old Kingdom, the administration could no longer support or stabilize the country's economy. Regional governors could not rely on the king for help in times of crisis, and the ensuing food shortages and political disputes escalated into famines and small-scale civil wars. Yet despite difficult problems, local leaders, owing no tribute to the king, used their new-found independence to establish a thriving culture in the provinces. Once in control of their own resources, the provinces became economically richer—which was demonstrated by larger and better burials among all social classes. In bursts of creativity, provincial artisans adopted and adapted cultural motifs formerly restricted to the royalty of the Old Kingdom, and scribes developed literary styles that expressed the optimism and originality of the period. Free from their loyalties to the king, local rulers began competing with each other for territorial control and political power. By 2160BC, rulers in Herakleopolis controlled Lower Egypt in the north, while a rival clan based in Thebes, the Intef family, took control of Upper Egypt in the south. As the Intefs grew in power and expanded their control northward, a clash between the two rival dynasties became inevitable. Around 2055BC the northern Theban forces under Nebhepetre Mentuhotep II finally defeated the Herakleopolitan rulers, reuniting the Two Lands. They inaugurated a period of economic and cultural renaissance known as the Middle Kingdom. Middle Kingdom (2134–1690 BC) The kings of the Middle Kingdom restored the country's stability and prosperity, thereby stimulating a resurgence of art, literature, and monumental building projects. Mentuhotep II and his Eleventh Dynasty successors ruled from Thebes, but the vizier Amenemhat I, upon assuming the kingship at the beginning of the Twelfth Dynasty around 1985BC, shifted the kingdom's capital to the city of Itjtawy, located in Faiyum. From Itjtawy, the kings of the Twelfth Dynasty undertook a far-sighted land reclamation and irrigation scheme to increase agricultural output in the region. Moreover, the military reconquered territory in Nubia that was rich in quarries and gold mines, while laborers built a defensive structure in the Eastern Delta, called the "Walls of the Ruler", to defend against foreign attack. With the kings having secured the country militarily and politically and with vast agricultural and mineral wealth at their disposal, the nation's population, arts, and religion flourished. In contrast to elitist Old Kingdom attitudes towards the gods, the Middle Kingdom displayed an increase in expressions of personal piety. Middle Kingdom literature featured sophisticated themes and characters written in a confident, eloquent style. The relief and portrait sculpture of the period captured subtle, individual details that reached new heights of technical sophistication. The last great ruler of the Middle Kingdom, Amenemhat III, allowed Semitic-speaking Canaanite settlers from the Near East into the Delta region to provide a sufficient labour force for his especially active mining and building campaigns. These ambitious building and mining activities, however, combined with severe Nile floods later in his reign, strained the economy and precipitated the slow decline into the Second Intermediate Period during the later Thirteenth and Fourteenth dynasties. During this decline, the Canaanite settlers began to assume greater control of the Delta region, eventually coming to power in Egypt as the Hyksos. Second Intermediate Period (1674–1549 BC) and the Hyksos Around 1785BC, as the power of the Middle Kingdom kings weakened, a Western Asian people called the Hyksos, who had already settled in the Delta, seized control of Egypt and established their capital at Avaris, forcing the former central government to retreat to Thebes. The king was treated as a vassal and expected to pay tribute. The Hyksos ("foreign rulers") retained Egyptian models of government and identified as kings, thereby integrating Egyptian elements into their culture. They and other invaders introduced new tools of warfare into Egypt, most notably the composite bow and the horse-drawn chariot. After retreating south, the native Theban kings found themselves trapped between the Canaanite Hyksos ruling the north and the Hyksos' Nubian allies, the Kushites, to the south. After years of vassalage, Thebes gathered enough strength to challenge the Hyksos in a conflict that lasted more than 30 years, until 1555BC. The kings Seqenenre Tao II and Kamose were ultimately able to defeat the Nubians to the south of Egypt, but failed to defeat the Hyksos. That task fell to Kamose's successor, Ahmose I, who successfully waged a series of campaigns that permanently eradicated the Hyksos' presence in Egypt. He established a new dynasty and, in the New Kingdom that followed, the military became a central priority for the kings, who sought to expand Egypt's borders and attempted to gain mastery of the Near East. New Kingdom (1549–1069 BC) The New Kingdom pharaohs established a period of unprecedented prosperity by securing their borders and strengthening diplomatic ties with their neighbours, including the Mitanni Empire, Assyria, and Canaan. Military campaigns waged under Tuthmosis I and his grandson Tuthmosis III extended the influence of the pharaohs to the largest empire Egypt had ever seen. Beginning with Merneptah the rulers of Egypt adopted the title of pharaoh. Between their reigns, Hatshepsut, a queen who established herself as pharaoh, launched many building projects, including the restoration of temples damaged by the Hyksos, and sent trading expeditions to Punt and the Sinai. When Tuthmosis III died in 1425BC, Egypt had an empire extending from Niya in north west Syria to the Fourth Cataract of the Nile in Nubia, cementing loyalties and opening access to critical imports such as bronze and wood. The New Kingdom pharaohs began a large-scale building campaign to promote the god Amun, whose growing cult was based in Karnak. They also constructed monuments to glorify their own achievements, both real and imagined. The Karnak temple is the largest Egyptian temple ever built. Around 1350BC, the stability of the New Kingdom was threatened when Amenhotep IV ascended the throne and instituted a series of radical and chaotic reforms. Changing his name to Akhenaten, he touted the previously obscure sun deity Aten as the supreme deity, suppressed the worship of most other deities, and moved the capital to the new city of Akhetaten (modern-day Amarna). He was devoted to his new religion and artistic style. After his death, the cult of the Aten was quickly abandoned and the traditional religious order restored. The subsequent pharaohs, Tutankhamun, Ay, and Horemheb, worked to erase all mention of Akhenaten's heresy, now known as the Amarna Period. Around 1279BC, Ramesses II, also known as Ramesses the Great, ascended the throne, and went on to build more temples, erect more statues and obelisks, and sire more children than any other pharaoh in history. A bold military leader, Ramesses II led his army against the Hittites in the Battle of Kadesh (in modern Syria) and, after fighting to a stalemate, finally agreed to the first recorded peace treaty, around 1258BC. Egypt's wealth, however, made it a tempting target for invasion, particularly by the Libyan Berbers to the west, and the Sea Peoples, a conjectured confederation of seafarers from the Aegean Sea. Initially, the military was able to repel these invasions, but Egypt eventually lost control of its remaining territories in southern Canaan, much of it falling to the Assyrians. The effects of external threats were exacerbated by internal problems such as corruption, tomb robbery, and civil unrest. After regaining their power, the high priests at the temple of Amun in Thebes accumulated vast tracts of land and wealth, and their expanded power splintered the country during the Third Intermediate Period. Third Intermediate Period (1069–653 BC) Following the death of Ramesses XI in 1078BC, Smendes assumed authority over the northern part of Egypt, ruling from the city of Tanis. The south was effectively controlled by the High Priests of Amun at Thebes, who recognized Smendes in name only. During this time, Libyans had been settling in the western delta, and chieftains of these settlers began increasing their autonomy. Libyan princes took control of the delta under Shoshenq I in 945BC, founding the so-called Libyan or Bubastite dynasty that would rule for some 200 years. Shoshenq also gained control of southern Egypt by placing his family members in important priestly positions. Libyan control began to erode as a rival dynasty in the delta arose in Leontopolis, and Kushites threatened from the south. Around 727BC the Kushite king Piye invaded northward, seizing control of Thebes and eventually the Delta, which established the 25th Dynasty. During the 25th Dynasty, Pharaoh Taharqa created an empire nearly as large as the New Kingdom's. Twenty-fifth Dynasty pharaohs built, or restored, temples and monuments throughout the Nile valley, including at Memphis, Karnak, Kawa, and Jebel Barkal. During this period, the Nile valley saw the first widespread construction of pyramids (many in modern Sudan) since the Middle Kingdom. Egypt's far-reaching prestige declined considerably toward the end of the Third Intermediate Period. Its foreign allies had fallen under the Assyrian sphere of influence, and by 700BC war between the two states became inevitable. Between 671 and 667BC the Assyrians began the Assyrian conquest of Egypt. The reigns of both Taharqa and his successor, Tanutamun, were filled with constant conflict with the Assyrians, against whom Egypt enjoyed several victories. Ultimately, the Assyrians pushed the Kushites back into Nubia, occupied Memphis, and sacked the temples of Thebes. Late Period (653–332 BC) The Assyrians left control of Egypt to a series of vassals who became known as the Saite kings of the Twenty-Sixth Dynasty. By 653BC, the Saite king Psamtik I was able to oust the Assyrians with the help of Greek mercenaries, who were recruited to form Egypt's first navy. Greek influence expanded greatly as the city-state of Naukratis became the home of Greeks in the Nile Delta. The Saite kings based in the new capital of Sais witnessed a brief but spirited resurgence in the economy and culture, but in 525BC, the powerful Persians, led by Cambyses II, began their conquest of Egypt, eventually capturing the pharaoh Psamtik III at the Battle of Pelusium. Cambyses II then assumed the formal title of pharaoh, but ruled Egypt from Iran, leaving Egypt under the control of a satrap. A few successful revolts against the Persians marked the 5th centuryBC, but Egypt was never able to permanently overthrow the Persians. Following its annexation by Persia, Egypt was joined with Cyprus and Phoenicia in the sixth satrapy of the Achaemenid Persian Empire. This first period of Persian rule over Egypt, also known as the Twenty-Seventh Dynasty, ended in 402BC, when Egypt regained independence under a series of native dynasties. The last of these dynasties, the Thirtieth, proved to be the last native royal house of ancient Egypt, ending with the kingship of Nectanebo II. A brief restoration of Persian rule, sometimes known as the Thirty-First Dynasty, began in 343BC, but shortly after, in 332BC, the Persian ruler Mazaces handed Egypt over to Alexander the Great without a fight. Ptolemaic period (332–30 BC) In 332BC, Alexander the Great conquered Egypt with little resistance from the Persians and was welcomed by the Egyptians as a deliverer. The administration established by Alexander's successors, the Macedonian Ptolemaic Kingdom, was based on an Egyptian model and based in the new capital city of Alexandria. The city showcased the power and prestige of Hellenistic rule, and became a seat of learning and culture, centered at the famous Library of Alexandria. The Lighthouse of Alexandria lit the way for the many ships that kept trade flowing through the city—as the Ptolemies made commerce and revenue-generating enterprises, such as papyrus manufacturing, their top priority. Hellenistic culture did not supplant native Egyptian culture, as the Ptolemies supported time-honored traditions in an effort to secure the loyalty of the populace. They built new temples in Egyptian style, supported traditional cults, and portrayed themselves as pharaohs. Some traditions merged, as Greek and Egyptian gods were syncretized into composite deities, such as Serapis, and classical Greek forms of sculpture influenced traditional Egyptian motifs. Despite their efforts to appease the Egyptians, the Ptolemies were challenged by native rebellion, bitter family rivalries, and the powerful mob of Alexandria that formed after the death of Ptolemy IV. In addition, as Rome relied more heavily on imports of grain from Egypt, the Romans took great interest in the political situation in the country. Continued Egyptian revolts, ambitious politicians, and powerful opponents from the Near East made this situation unstable, leading Rome to send forces to secure the country as a province of its empire. Roman period (30 BC – AD 641) Egypt became a province of the Roman Empire in 30BC, following the defeat of Mark Antony and Ptolemaic Queen Cleopatra VII by Octavian (later Emperor Augustus) in the Battle of Actium. The Romans relied heavily on grain shipments from Egypt, and the Roman army, under the control of a prefect appointed by the emperor, quelled rebellions, strictly enforced the collection of heavy taxes, and prevented attacks by bandits, which had become a notorious problem during the period. Alexandria became an increasingly important center on the trade route with the orient, as exotic luxuries were in high demand in Rome. Although the Romans had a more hostile attitude than the Greeks towards the Egyptians, some traditions such as mummification and worship of the traditional gods continued. The art of mummy portraiture flourished, and some Roman emperors had themselves depicted as pharaohs, though not to the extent that the Ptolemies had. The former lived outside Egypt and did not perform the ceremonial functions of Egyptian kingship. Local administration became Roman in style and closed to native Egyptians. From the mid-first century AD, Christianity took root in Egypt and it was originally seen as another cult that could be accepted. However, it was an uncompromising religion that sought to win converts from the pagan Egyptian and Greco-Roman religions and threatened popular religious traditions. This led to the persecution of converts to Christianity, culminating in the great purges of Diocletian starting in 303, but eventually Christianity won out. In 391 the Christian emperor Theodosius introduced legislation that banned pagan rites and closed temples. Alexandria became the scene of great anti-pagan riots with public and private religious imagery destroyed. As a consequence, Egypt's native religious culture was continually in decline. While the native population continued to speak their language, the ability to read hieroglyphic writing slowly disappeared as the role of the Egyptian temple priests and priestesses diminished. The temples themselves were sometimes converted to churches or abandoned to the desert. In the fourth century, as the Roman Empire divided, Egypt found itself in the Eastern Empire with its capital at Constantinople. In the waning years of the Empire, Egypt fell to the Sasanian Persian army in the Sasanian conquest of Egypt (618–628). It was then recaptured by the Byzantine emperor Heraclius (629–639), and was finally captured by Muslim Rashidun army in 639–641, ending Byzantine rule. Government and economy Administration and commerce The pharaoh was the absolute monarch of the country and, at least in theory, wielded complete control of the land and its resources. The king was the supreme military commander and head of the government, who relied on a bureaucracy of officials to manage his affairs. In charge of the administration was his second in command, the vizier, who acted as the king's representative and coordinated land surveys, the treasury, building projects, the legal system, and the archives. At a regional level, the country was divided into as many as 42 administrative regions called nomes each governed by a nomarch, who was accountable to the vizier for his jurisdiction. The temples formed the backbone of the economy. Not only were they places of worship, but were also responsible for collecting and storing the kingdom's wealth in a system of granaries and treasuries administered by overseers, who redistributed grain and goods. Much of the economy was centrally organized and strictly controlled. Although the ancient Egyptians did not use coinage until the Late period, they did use a type of money-barter system, with standard sacks of grain and the deben, a weight of roughly of copper or silver, forming a common denominator. Workers were paid in grain; a simple laborer might earn 5 sacks (200 kg or 400 lb) of grain per month, while a foreman might earn 7 sacks (250 kg or 550 lb). Prices were fixed across the country and recorded in lists to facilitate trading; for example a shirt cost five copper deben, while a cow cost 140deben. Grain could be traded for other goods, according to the fixed price list. During the fifth centuryBC coined money was introduced into Egypt from abroad. At first the coins were used as standardized pieces of precious metal rather than true money, but in the following centuries international traders came to rely on coinage. Social status Egyptian society was highly stratified, and social status was expressly displayed. Farmers made up the bulk of the population, but agricultural produce was owned directly by the state, temple, or noble family that owned the land. Farmers were also subject to a labor tax and were required to work on irrigation or construction projects in a corvée system. Artists and craftsmen were of higher status than farmers, but they were also under state control, working in the shops attached to the temples and paid directly from the state treasury. Scribes and officials formed the upper class in ancient Egypt, known as the "white kilt class" in reference to the bleached linen garments that served as a mark of their rank. The upper class prominently displayed their social status in art and literature. Below the nobility were the priests, physicians, and engineers with specialized training in their field. It is unclear whether slavery as understood today existed in ancient Egypt; there is difference of opinions among authors. The ancient Egyptians viewed men and women, including people from all social classes, as essentially equal under the law, and even the lowliest peasant was entitled to petition the vizier and his court for redress. Although slaves were mostly used as indentured servants, they were able to buy and sell their servitude, work their way to freedom or nobility, and were usually treated by doctors in the workplace. Both men and women had the right to own and sell property, make contracts, marry and divorce, receive inheritance, and pursue legal disputes in court. Married couples could own property jointly and protect themselves from divorce by agreeing to marriage contracts, which stipulated the financial obligations of the husband to his wife and children should the marriage end. Compared with their counterparts in ancient Greece, Rome, and even more modern places around the world, ancient Egyptian women had a greater range of personal choices, legal rights, and opportunities for achievement. Women such as Hatshepsut and Cleopatra VII even became pharaohs, while others wielded power as Divine Wives of Amun. Despite these freedoms, ancient Egyptian women did not often take part in official roles in the administration, aside from the royal high priestesses, apparently served only secondary roles in the temples (not much data for many dynasties), and were not so likely to be as educated as men. Legal system The head of the legal system was officially the pharaoh, who was responsible for enacting laws, delivering justice, and maintaining law and order, a concept the ancient Egyptians referred to as Ma'at. Although no legal codes from ancient Egypt survive, court documents show that Egyptian law was based on a common-sense view of right and wrong that emphasized reaching agreements and resolving conflicts rather than strictly adhering to a complicated set of statutes. Local councils of elders, known as Kenbet in the New Kingdom, were responsible for ruling in court cases involving small claims and minor disputes. More serious cases involving murder, major land transactions, and tomb robbery were referred to the Great Kenbet, over which the vizier or pharaoh presided. Plaintiffs and defendants were expected to represent themselves and were required to swear an oath that they had told the truth. In some cases, the state took on both the role of prosecutor and judge, and it could torture the accused with beatings to obtain a confession and the names of any co-conspirators. Whether the charges were trivial or serious, court scribes documented the complaint, testimony, and verdict of the case for future reference. Punishment for minor crimes involved either imposition of fines, beatings, facial mutilation, or exile, depending on the severity of the offense. Serious crimes such as murder and tomb robbery were punished by execution, carried out by decapitation, drowning, or impaling the criminal on a stake. Punishment could also be extended to the criminal's family. Beginning in the New Kingdom, oracles played a major role in the legal system, dispensing justice in both civil and criminal cases. The procedure was to ask the god a "yes" or "no" question concerning the right or wrong of an issue. The god, carried by a number of priests, rendered judgement by choosing one or the other, moving forward or backward, or pointing to one of the answers written on a piece of papyrus or an ostracon. Agriculture A combination of favorable geographical features contributed to the success of ancient Egyptian culture, the most important of which was the rich fertile soil resulting from annual inundations of the Nile River. The ancient Egyptians were thus able to produce an abundance of food, allowing the population to devote more time and resources to cultural, technological, and artistic pursuits. Land management was crucial in ancient Egypt because taxes were assessed based on the amount of land a person owned. Farming in Egypt was dependent on the cycle of the Nile River. The Egyptians recognized three seasons: Akhet (flooding), Peret (planting), and Shemu (harvesting). The flooding season lasted from June to September, depositing on the river's banks a layer of mineral-rich silt ideal for growing crops. After the floodwaters had receded, the growing season lasted from October to February. Farmers plowed and planted seeds in the fields, which were irrigated with ditches and canals. Egypt received little rainfall, so farmers relied on the Nile to water their crops. From March to May, farmers used sickles to harvest their crops, which were then threshed with a flail to separate the straw from the grain. Winnowing removed the chaff from the grain, and the grain was then ground into flour, brewed to make beer, or stored for later use. The ancient Egyptians cultivated emmer and barley, and several other cereal grains, all of which were used to make the two main food staples of bread and beer. Flax plants, uprooted before they started flowering, were grown for the fibers of their stems. These fibers were split along their length and spun into thread, which was used to weave sheets of linen and to make clothing. Papyrus growing on the banks of the Nile River was used to make paper. Vegetables and fruits were grown in garden plots, close to habitations and on higher ground, and had to be watered by hand. Vegetables included leeks, garlic, melons, squashes, pulses, lettuce, and other crops, in addition to grapes that were made into wine. Animals The Egyptians believed that a balanced relationship between people and animals was an essential element of the cosmic order; thus humans, animals and plants were believed to be members of a single whole. Animals, both domesticated and wild, were therefore a critical source of spirituality, companionship, and sustenance to the ancient Egyptians. Cattle were the most important livestock; the administration collected taxes on livestock in regular censuses, and the size of a herd reflected the prestige and importance of the estate or temple that owned them. In addition to cattle, the ancient Egyptians kept sheep, goats, and pigs. Poultry, such as ducks, geese, and pigeons, were captured in nets and bred on farms, where they were force-fed with dough to fatten them. The Nile provided a plentiful source of fish. Bees were also domesticated from at least the Old Kingdom, and provided both honey and wax. The ancient Egyptians used donkeys and oxen as beasts of burden, and they were responsible for plowing the fields and trampling seed into the soil. The slaughter of a fattened ox was also a central part of an offering ritual. Horses were introduced by the Hyksos in the Second Intermediate Period. Camels, although known from the New Kingdom, were not used as beasts of burden until the Late Period. There is also evidence to suggest that elephants were briefly utilized in the Late Period but largely abandoned due to lack of grazing land. Cats, dogs, and monkeys were common family pets, while more exotic pets imported from the heart of Africa, such as Sub-Saharan African lions, were reserved for royalty. Herodotus observed that the Egyptians were the only people to keep their animals with them in their houses. During the Late Period, the worship of the gods in their animal form was extremely popular, such as the cat goddess Bastet and the ibis god Thoth, and these animals were kept in large numbers for the purpose of ritual sacrifice. Natural resources Egypt is rich in building and decorative stone, copper and lead ores, gold, and semiprecious stones. These natural resources allowed the ancient Egyptians to build monuments, sculpt statues, make tools, and fashion jewelry. Embalmers used salts from the Wadi Natrun for mummification, which also provided the gypsum needed to make plaster. Ore-bearing rock formations were found in distant, inhospitable wadis in the Eastern Desert and the Sinai, requiring large, state-controlled expeditions to obtain natural resources found there. There were extensive gold mines in Nubia, and one of the first maps known is of a gold mine in this region. The Wadi Hammamat was a notable source of granite, greywacke, and gold. Flint was the first mineral collected and used to make tools, and flint handaxes are the earliest pieces of evidence of habitation in the Nile valley. Nodules of the mineral were carefully flaked to make blades and arrowheads of moderate hardness and durability even after copper was adopted for this purpose. Ancient Egyptians were among the first to use minerals such as sulfur as cosmetic substances. The Egyptians worked deposits of the lead ore galena at Gebel Rosas to make net sinkers, plumb bobs, and small figurines. Copper was the most important metal for toolmaking in ancient Egypt and was smelted in furnaces from malachite ore mined in the Sinai. Workers collected gold by washing the nuggets out of sediment in alluvial deposits, or by the more labor-intensive process of grinding and washing gold-bearing quartzite. Iron deposits found in upper Egypt were utilized in the Late Period. High-quality building stones were abundant in Egypt; the ancient Egyptians quarried limestone all along the Nile valley, granite from Aswan, and basalt and sandstone from the wadis of the Eastern Desert. Deposits of decorative stones such as porphyry, greywacke, alabaster, and carnelian dotted the Eastern Desert and were collected even before the First Dynasty. In the Ptolemaic and Roman Periods, miners worked deposits of emeralds in Wadi Sikait and amethyst in Wadi el-Hudi. Trade The ancient Egyptians engaged in trade with their foreign neighbors to obtain rare, exotic goods not found in Egypt. In the Predynastic Period, they established trade with Nubia to obtain gold and incense. They also established trade with Palestine, as evidenced by Palestinian-style oil jugs found in the burials of the First Dynasty pharaohs. An Egyptian colony stationed in southern Canaan dates to slightly before the First Dynasty. Narmer had Egyptian pottery produced in Canaan and exported back to Egypt. By the Second Dynasty at latest, ancient Egyptian trade with Byblos yielded a critical source of quality timber not found in Egypt. By the Fifth Dynasty, trade with Punt provided gold, aromatic resins, ebony, ivory, and wild animals such as monkeys and baboons. Egypt relied on trade with Anatolia for essential quantities of tin as well as supplementary supplies of copper, both metals being necessary for the manufacture of bronze. The ancient Egyptians prized the blue stone lapis lazuli, which had to be imported from far-away Afghanistan. Egypt's Mediterranean trade partners also included Greece and Crete, which provided, among other goods, supplies of olive oil. Language Historical development The Egyptian language is a northern Afro-Asiatic language closely related to the Berber and Semitic languages. It has the second longest known history of any language (after Sumerian), having been written from c. 3200BC to the Middle Ages and remaining as a spoken language for longer. The phases of ancient Egyptian are Old Egyptian, Middle Egyptian (Classical Egyptian), Late Egyptian, Demotic and Coptic. Egyptian writings do not show dialect differences before Coptic, but it was probably spoken in regional dialects around Memphis and later Thebes. Ancient Egyptian was a synthetic language, but it became more analytic later on. Late Egyptian developed prefixal definite and indefinite articles, which replaced the older inflectional suffixes. There was a change from the older verb–subject–object word order to subject–verb–object. The Egyptian hieroglyphic, hieratic, and demotic scripts were eventually replaced by the more phonetic Coptic alphabet. Coptic is still used in the liturgy of the Egyptian Orthodox Church, and traces of it are found in modern Egyptian Arabic. Sounds and grammar Ancient Egyptian has 25 consonants similar to those of other Afro-Asiatic languages. These include pharyngeal and emphatic consonants, voiced and voiceless stops, voiceless fricatives and voiced and voiceless affricates. It has three long and three short vowels, which expanded in Late Egyptian to about nine. The basic word in Egyptian, similar to Semitic and Berber, is a triliteral or biliteral root of consonants and semiconsonants. Suffixes are added to form words. The verb conjugation corresponds to the person. For example, the triconsonantal skeleton is the semantic core of the word 'hear'; its basic conjugation is , 'he hears'. If the subject is a noun, suffixes are not added to the verb: , 'the woman hears'. Adjectives are derived from nouns through a process that Egyptologists call nisbation because of its similarity with Arabic. The word order is in verbal and adjectival sentences, and in nominal and adverbial sentences. The subject can be moved to the beginning of sentences if it is long and is followed by a resumptive pronoun. Verbs and nouns are negated by the particle n, but nn is used for adverbial and adjectival sentences. Stress falls on the ultimate or penultimate syllable, which can be open (CV) or closed (CVC). Writing Hieroglyphic writing dates from c. 3000BC, and is composed of hundreds of symbols. A hieroglyph can represent a word, a sound, or a silent determinative; and the same symbol can serve different purposes in different contexts. Hieroglyphs were a formal script, used on stone monuments and in tombs, that could be as detailed as individual works of art. In day-to-day writing, scribes used a cursive form of writing, called hieratic, which was quicker and easier. While formal hieroglyphs may be read in rows or columns in either direction (though typically written from right to left), hieratic was always written from right to left, usually in horizontal rows. A new form of writing, Demotic, became the prevalent writing style, and it is this form of writing—along with formal hieroglyphs—that accompany the Greek text on the Rosetta Stone. Around the first century AD, the Coptic alphabet started to be used alongside the Demotic script. Coptic is a modified Greek alphabet with the addition of some Demotic signs. Although formal hieroglyphs were used in a ceremonial role until the fourth century, towards the end only a small handful of priests could still read them. As the traditional religious establishments were disbanded, knowledge of hieroglyphic writing was mostly lost. Attempts to decipher them date to the Byzantine and Islamic periods in Egypt, but only in the 1820s, after the discovery of the Rosetta Stone and years of research by Thomas Young and Jean-François Champollion, were hieroglyphs substantially deciphered. Literature Writing first appeared in association with kingship on labels and tags for items found in royal tombs. It was primarily an occupation of the scribes, who worked out of the Per Ankh institution or the House of Life. The latter comprised offices, libraries (called House of Books), laboratories and observatories. Some of the best-known pieces of ancient Egyptian literature, such as the Pyramid and Coffin Texts, were written in Classical Egyptian, which continued to be the language of writing until about 1300BC. Late Egyptian was spoken from the New Kingdom onward and is represented in Ramesside administrative documents, love poetry and tales, as well as in Demotic and Coptic texts. During this period, the tradition of writing had evolved into the tomb autobiography, such as those of Harkhuf and Weni. The genre known as Sebayt ("instructions") was developed to communicate teachings and guidance from famous nobles; the Ipuwer papyrus, a poem of lamentations describing natural disasters and social upheaval, is a famous example. The Story of Sinuhe, written in Middle Egyptian, might be the classic of Egyptian literature. Also written at this time was the Westcar Papyrus, a set of stories told to Khufu by his sons relating the marvels performed by priests. The Instruction of Amenemope is considered a masterpiece of Near Eastern literature. Towards the end of the New Kingdom, the vernacular language was more often employed to write popular pieces like the Story of Wenamun and the Instruction of Any. The former tells the story of a noble who is robbed on his way to buy cedar from Lebanon and of his struggle to return to Egypt. From about 700BC, narrative stories and instructions, such as the popular Instructions of Onchsheshonqy, as well as personal and business documents were written in the demotic script and phase of Egyptian. Many stories written in demotic during the Greco-Roman period were set in previous historical eras, when Egypt was an independent nation ruled by great pharaohs such as Ramesses II. Culture Daily life Most ancient Egyptians were farmers tied to the land. Their dwellings were restricted to immediate family members, and were constructed of mudbrick designed to remain cool in the heat of the day. Each home had a kitchen with an open roof, which contained a grindstone for milling grain and a small oven for baking the bread. Ceramics served as household wares for the storage, preparation, transport, and consumption of food, drink, and raw materials. Walls were painted white and could be covered with dyed linen wall hangings. Floors were covered with reed mats, while wooden stools, beds raised from the floor and individual tables comprised the furniture. The ancient Egyptians placed a great value on hygiene and appearance. Most bathed in the Nile and used a pasty soap made from animal fat and chalk. Men shaved their entire bodies for cleanliness; perfumes and aromatic ointments covered bad odors and soothed skin. Clothing was made from simple linen sheets that were bleached white, and both men and women of the upper classes wore wigs, jewelry, and cosmetics. Children went without clothing until maturity, at about age 12, and at this age males were circumcised and had their heads shaved. Mothers were responsible for taking care of the children, while the father provided the family's income. Music and dance were popular entertainments for those who could afford them. Early instruments included flutes and harps, while instruments similar to trumpets, oboes, and pipes developed later and became popular. In the New Kingdom, the Egyptians played on bells, cymbals, tambourines, drums, and imported lutes and lyres from Asia. The sistrum was a rattle-like musical instrument that was especially important in religious ceremonies. The ancient Egyptians enjoyed a variety of leisure activities, including games and music. Senet, a board game where pieces moved according to random chance, was particularly popular from the earliest times; another similar game was mehen, which had a circular gaming board. “Hounds and Jackals” also known as 58 holes is another example of board games played in ancient Egypt. The first complete set of this game was discovered from a Theban tomb of the Egyptian pharaoh Amenemhat IV that dates to the 13th Dynasty. Juggling and ball games were popular with children, and wrestling is also documented in a tomb at Beni Hasan. The wealthy members of ancient Egyptian society enjoyed hunting, fishing, and boating as well. The excavation of the workers' village of Deir el-Medina has resulted in one of the most thoroughly documented accounts of community life in the ancient world, which spans almost four hundred years. There is no comparable site in which the organization, social interactions, and working and living conditions of a community have been studied in such detail. Cuisine Egyptian cuisine remained remarkably stable over time; indeed, the cuisine of modern Egypt retains some striking similarities to the cuisine of the ancients. The staple diet consisted of bread and beer, supplemented with vegetables such as onions and garlic, and fruit such as dates and figs. Wine and meat were enjoyed by all on feast days while the upper classes indulged on a more regular basis. Fish, meat, and fowl could be salted or dried, and could be cooked in stews or roasted on a grill. Architecture The architecture of ancient Egypt includes some of the most famous structures in the world: the Great Pyramids of Giza and the temples at Thebes. Building projects were organized and funded by the state for religious and commemorative purposes, but also to reinforce the wide-ranging power of the pharaoh. The ancient Egyptians were skilled builders; using only simple but effective tools and sighting instruments, architects could build large stone structures with great accuracy and precision that is still envied today. The domestic dwellings of elite and ordinary Egyptians alike were constructed from perishable materials such as mudbricks and wood, and have not survived. Peasants lived in simple homes, while the palaces of the elite and the pharaoh were more elaborate structures. A few surviving New Kingdom palaces, such as those in Malkata and Amarna, show richly decorated walls and floors with scenes of people, birds, water pools, deities and geometric designs. Important structures such as temples and tombs that were intended to last forever were constructed of stone instead of mudbricks. The architectural elements used in the world's first large-scale stone building, Djoser's mortuary complex, include post and lintel supports in the papyrus and lotus motif. The earliest preserved ancient Egyptian temples, such as those at Giza, consist of single, enclosed halls with roof slabs supported by columns. In the New Kingdom, architects added the pylon, the open courtyard, and the enclosed hypostyle hall to the front of the temple's sanctuary, a style that was standard until the Greco-Roman period. The earliest and most popular tomb architecture in the Old Kingdom was the mastaba, a flat-roofed rectangular structure of mudbrick or stone built over an underground burial chamber. The step pyramid of Djoser is a series of stone mastabas stacked on top of each other. Pyramids were built during the Old and Middle Kingdoms, but most later rulers abandoned them in favor of less conspicuous rock-cut tombs. The use of the pyramid form continued in private tomb chapels of the New Kingdom and in the royal pyramids of Nubia. Art The ancient Egyptians produced art to serve functional purposes. For over 3500 years, artists adhered to artistic forms and iconography that were developed during the Old Kingdom, following a strict set of principles that resisted foreign influence and internal change. These artistic standards—simple lines, shapes, and flat areas of color combined with the characteristic flat projection of figures with no indication of spatial depth—created a sense of order and balance within a composition. Images and text were intimately interwoven on tomb and temple walls, coffins, stelae, and even statues. The Narmer Palette, for example, displays figures that can also be read as hieroglyphs. Because of the rigid rules that governed its highly stylized and symbolic appearance, ancient Egyptian art served its political and religious purposes with precision and clarity. Ancient Egyptian artisans used stone as a medium for carving statues and fine reliefs, but used wood as a cheap and easily carved substitute. Paints were obtained from minerals such as iron ores (red and yellow ochres), copper ores (blue and green), soot or charcoal (black), and limestone (white). Paints could be mixed with gum arabic as a binder and pressed into cakes, which could be moistened with water when needed. Pharaohs used reliefs to record victories in battle, royal decrees, and religious scenes. Common citizens had access to pieces of funerary art, such as shabti statues and books of the dead, which they believed would protect them in the afterlife. During the Middle Kingdom, wooden or clay models depicting scenes from everyday life became popular additions to the tomb. In an attempt to duplicate the activities of the living in the afterlife, these models show laborers, houses, boats, and even military formations that are scale representations of the ideal ancient Egyptian afterlife. Despite the homogeneity of ancient Egyptian art, the styles of particular times and places sometimes reflected changing cultural or political attitudes. After the invasion of the Hyksos in the Second Intermediate Period, Minoan-style frescoes were found in Avaris. The most striking example of a politically driven change in artistic forms comes from the Amarna Period, where figures were radically altered to conform to Akhenaten's revolutionary religious ideas. This style, known as Amarna art, was quickly abandoned after Akhenaten's death and replaced by the traditional forms. Religious beliefs Beliefs in the divine and in the afterlife were ingrained in ancient Egyptian civilization from its inception; pharaonic rule was based on the divine right of kings. The Egyptian pantheon was populated by gods who had supernatural powers and were called on for help or protection. However, the gods were not always viewed as benevolent, and Egyptians believed they had to be appeased with offerings and prayers. The structure of this pantheon changed continually as new deities were promoted in the hierarchy, but priests made no effort to organize the diverse and sometimes conflicting myths and stories into a coherent system. These various conceptions of divinity were not considered contradictory but rather layers in the multiple facets of reality. Gods were worshiped in cult temples administered by priests acting on the king's behalf. At the center of the temple was the cult statue in a shrine. Temples were not places of public worship or congregation, and only on select feast days and celebrations was a shrine carrying the statue of the god brought out for public worship. Normally, the god's domain was sealed off from the outside world and was only accessible to temple officials. Common citizens could worship private statues in their homes, and amulets offered protection against the forces of chaos. After the New Kingdom, the pharaoh's role as a spiritual intermediary was de-emphasized as religious customs shifted to direct worship of the gods. As a result, priests developed a system of oracles to communicate the will of the gods directly to the people. The Egyptians believed that every human being was composed of physical and spiritual parts or aspects. In addition to the body, each person had a šwt (shadow), a ba (personality or soul), a ka (life-force), and a name. The heart, rather than the brain, was considered the seat of thoughts and emotions. After death, the spiritual aspects were released from the body and could move at will, but they required the physical remains (or a substitute, such as a statue) as a permanent home. The ultimate goal of the deceased was to rejoin his ka and ba and become one of the "blessed dead", living on as an akh, or "effective one". For this to happen, the deceased had to be judged worthy in a trial, in which the heart was weighed against a "feather of truth." If deemed worthy, the deceased could continue their existence on earth in spiritual form. If they were not deemed worthy, their heart was eaten by Ammit the Devourer and they were erased from the Universe. Burial customs The ancient Egyptians maintained an elaborate set of burial customs that they believed were necessary to ensure immortality after death. These customs involved preserving the body by mummification, performing burial ceremonies, and interring with the body goods the deceased would use in the afterlife. Before the Old Kingdom, bodies buried in desert pits were naturally preserved by desiccation. The arid, desert conditions were a boon throughout the history of ancient Egypt for burials of the poor, who could not afford the elaborate burial preparations available to the elite. Wealthier Egyptians began to bury their dead in stone tombs and use artificial mummification, which involved removing the internal organs, wrapping the body in linen, and burying it in a rectangular stone sarcophagus or wooden coffin. Beginning in the Fourth Dynasty, some parts were preserved separately in canopic jars. By the New Kingdom, the ancient Egyptians had perfected the art of mummification; the best technique took 70 days and involved removing the internal organs, removing the brain through the nose, and desiccating the body in a mixture of salts called natron. The body was then wrapped in linen with protective amulets inserted between layers and placed in a decorated anthropoid coffin. Mummies of the Late Period were also placed in painted cartonnage mummy cases. Actual preservation practices declined during the Ptolemaic and Roman eras, while greater emphasis was placed on the outer appearance of the mummy, which was decorated. Wealthy Egyptians were buried with larger quantities of luxury items, but all burials, regardless of social status, included goods for the deceased. Funerary texts were often included in the grave, and, beginning in the New Kingdom, so were shabti statues that were believed to perform manual labor for them in the afterlife. Rituals in which the deceased was magically re-animated accompanied burials. After burial, living relatives were expected to occasionally bring food to the tomb and recite prayers on behalf of the deceased. Military The ancient Egyptian military was responsible for defending Egypt against foreign invasion, and for maintaining Egypt's domination in the ancient Near East. The military protected mining expeditions to the Sinai during the Old Kingdom and fought civil wars during the First and Second Intermediate Periods. The military was responsible for maintaining fortifications along important trade routes, such as those found at the city of Buhen on the way to Nubia. Forts also were constructed to serve as military bases, such as the fortress at Sile, which was a base of operations for expeditions to the Levant. In the New Kingdom, a series of pharaohs used the standing Egyptian army to attack and conquer Kush and parts of the Levant. Typical military equipment included bows and arrows, spears, and round-topped shields made by stretching animal skin over a wooden frame. In the New Kingdom, the military began using chariots that had earlier been introduced by the Hyksos invaders. Weapons and armor continued to improve after the adoption of bronze: shields were now made from solid wood with a bronze buckle, spears were tipped with a bronze point, and the khopesh was adopted from Asiatic soldiers. The pharaoh was usually depicted in art and literature riding at the head of the army; it has been suggested that at least a few pharaohs, such as Seqenenre Tao II and his sons, did do so. However, it has also been argued that "kings of this period did not personally act as frontline war leaders, fighting alongside their troops." Soldiers were recruited from the general population, but during, and especially after, the New Kingdom, mercenaries from Nubia, Kush, and Libya were hired to fight for Egypt. Technology, medicine, and mathematics Technology In technology, medicine, and mathematics, ancient Egypt achieved a relatively high standard of productivity and sophistication. Traditional empiricism, as evidenced by the Edwin Smith and Ebers papyri (c. 1600BC), is first credited to Egypt. The Egyptians created their own alphabet and decimal system. Faience and glass Even before the Old Kingdom, the ancient Egyptians had developed a glassy material known as faience, which they treated as a type of artificial semi-precious stone. Faience is a non-clay ceramic made of silica, small amounts of lime and soda, and a colorant, typically copper. The material was used to make beads, tiles, figurines, and small wares. Several methods can be used to create faience, but typically production involved application of the powdered materials in the form of a paste over a clay core, which was then fired. By a related technique, the ancient Egyptians produced a pigment known as Egyptian blue, also called blue frit, which is produced by fusing (or sintering) silica, copper, lime, and an alkali such as natron. The product can be ground up and used as a pigment. The ancient Egyptians could fabricate a wide variety of objects from glass with great skill, but it is not clear whether they developed the process independently. It is also unclear whether they made their own raw glass or merely imported pre-made ingots, which they melted and finished. However, they did have technical expertise in making objects, as well as adding trace elements to control the color of the finished glass. A range of colors could be produced, including yellow, red, green, blue, purple, and white, and the glass could be made either transparent or opaque. Medicine The medical problems of the ancient Egyptians stemmed directly from their environment. Living and working close to the Nile brought hazards from malaria and debilitating schistosomiasis parasites, which caused liver and intestinal damage. Dangerous wildlife such as crocodiles and hippos were also a common threat. The lifelong labors of farming and building put stress on the spine and joints, and traumatic injuries from construction and warfare all took a significant toll on the body. The grit and sand from stone-ground flour abraded teeth, leaving them susceptible to abscesses (though caries were rare). The diets of the wealthy were rich in sugars, which promoted periodontal disease. Despite the flattering physiques portrayed on tomb walls, the overweight mummies of many of the upper class show the effects of a life of overindulgence. Adult life expectancy was about 35 for men and 30 for women, but reaching adulthood was difficult as about one-third of the population died in infancy. Ancient Egyptian physicians were renowned in the ancient Near East for their healing skills, and some, such as Imhotep, remained famous long after their deaths. Herodotus remarked that there was a high degree of specialization among Egyptian physicians, with some treating only the head or the stomach, while others were eye-doctors and dentists. Training of physicians took place at the Per Ankh or "House of Life" institution, most notably those headquartered in Per-Bastet during the New Kingdom and at Abydos and Saïs in the Late period. Medical papyri show empirical knowledge of anatomy, injuries, and practical treatments. Wounds were treated by bandaging with raw meat, white linen, sutures, nets, pads, and swabs soaked with honey to prevent infection, while opium, thyme, and belladona were used to relieve pain. The earliest records of burn treatment describe burn dressings that use the milk from mothers of male babies. Prayers were made to the goddess Isis. Moldy bread, honey, and copper salts were also used to prevent infection from dirt in burns. Garlic and onions were used regularly to promote good health and were thought to relieve asthma symptoms. Ancient Egyptian surgeons stitched wounds, set broken bones, and amputated diseased limbs, but they recognized that some injuries were so serious that they could only make the patient comfortable until death occurred. Maritime technology Early Egyptians knew how to assemble planks of wood into a ship hull and had mastered advanced forms of shipbuilding as early as 3000BC. The Archaeological Institute of America reports that the oldest planked ships known are the Abydos boats. A group of 14 discovered ships in Abydos were constructed of wooden planks "sewn" together. Discovered by Egyptologist David O'Connor of New York University, woven straps were found to have been used to lash the planks together, and reeds or grass stuffed between the planks helped to seal the seams. Because the ships are all buried together and near a mortuary belonging to Pharaoh Khasekhemwy, originally they were all thought to have belonged to him, but one of the 14 ships dates to 3000BC, and the associated pottery jars buried with the vessels also suggest earlier dating. The ship dating to 3000BC was long and is now thought to perhaps have belonged to an earlier pharaoh, perhaps one as early as Hor-Aha. Early Egyptians also knew how to assemble planks of wood with treenails to fasten them together, using pitch for caulking the seams. The "Khufu ship", a vessel sealed into a pit in the Giza pyramid complex at the foot of the Great Pyramid of Giza in the Fourth Dynasty around 2500BC, is a full-size surviving example that may have filled the symbolic function of a solar barque. Early Egyptians also knew how to fasten the planks of this ship together with mortise and tenon joints. Large seagoing ships are known to have been heavily used by the Egyptians in their trade with the city states of the eastern Mediterranean, especially Byblos (on the coast of modern-day Lebanon), and in several expeditions down the Red Sea to the Land of Punt. In fact one of the earliest Egyptian words for a seagoing ship is a "Byblos Ship", which originally defined a class of Egyptian seagoing ships used on the Byblos run; however, by the end of the Old Kingdom, the term had come to include large seagoing ships, whatever their destination. In 1977, an ancient north–south canal was discovered extending from Lake Timsah to the Ballah Lakes. It was dated to the Middle Kingdom of Egypt by extrapolating dates of ancient sites constructed along its course. In 2011, archaeologists from Italy, the United States, and Egypt excavating a dried-up lagoon known as Mersa Gawasis have unearthed traces of an ancient harbor that once launched early voyages like Hatshepsut's Punt expedition onto the open ocean. Some of the site's most evocative evidence for the ancient Egyptians' seafaring prowess include large ship timbers and hundreds of feet of ropes, made from papyrus, coiled in huge bundles. In 2013, a team of Franco-Egyptian archaeologists discovered what is believed to be the world's oldest port, dating back about 4500 years, from the time of King Cheops on the Red Sea coast near Wadi el-Jarf (about 110 miles south of Suez). Mathematics The earliest attested examples of mathematical calculations date to the predynastic Naqada period, and show a fully developed numeral system. The importance of mathematics to an educated Egyptian is suggested by a New Kingdom fictional letter in which the writer proposes a scholarly competition between himself and another scribe regarding everyday calculation tasks such as accounting of land, labor, and grain. Texts such as the Rhind Mathematical Papyrus and the Moscow Mathematical Papyrus show that the ancient Egyptians could perform the four basic mathematical operations—addition, subtraction, multiplication, and division—use fractions, calculate the areas of rectangles, triangles, and circles and compute the volumes of boxes, columns and pyramids. They understood basic concepts of algebra and geometry, and could solve simple sets of simultaneous equations. Mathematical notation was decimal, and based on hieroglyphic signs for each power of ten up to one million. Each of these could be written as many times as necessary to add up to the desired number; so to write the number eighty or eight hundred, the symbol for ten or one hundred was written eight times respectively. Because their methods of calculation could not handle most fractions with a numerator greater than one, they had to write fractions as the sum of several fractions. For example, they resolved the fraction two-fifths into the sum of one-third + one-fifteenth. Standard tables of values facilitated this. Some common fractions, however, were written with a special glyph—the equivalent of the modern two-thirds is shown on the right. Ancient Egyptian mathematicians knew the Pythagorean theorem as an empirical formula. They were aware, for example, that a triangle had a right angle opposite the hypotenuse when its sides were in a 3–4–5 ratio. They were able to estimate the area of a circle by subtracting one-ninth from its diameter and squaring the result: Area ≈ [()D]2 = ()r2 ≈ 3.16r2, a reasonable approximation of the formula . The golden ratio seems to be reflected in many Egyptian constructions, including the pyramids, but its use may have been an unintended consequence of the ancient Egyptian practice of combining the use of knotted ropes with an intuitive sense of proportion and harmony. Population Estimates of the size of the population range from 1-1.5 million in the 3rd millennium BCE to possibly 2-3 million by the 1st millennium BCE, before growing significantly towards the end of that millennium. DNA In 2012, the DNA of the 20th dynasty mummies of Ramesses III and another mummy believed to be Ramesses III's son Pentawer were analyzed by Albert Zink, Yehia Z Gad and a team of researchers under Zahi Hawass, then Secretary General of the Supreme Council of Antiquities, Egypt. Genetic kinship analyses revealed identical haplotypes in both mummies. Using the Whit Athey's haplogroup predictor, they identified the Y chromosomal haplogroup E1b1a (E-M2). In 2017, a team led by led by researchers from the University of Tuebingen and the Max Planck Institute for the Science of Human History in Jena tested the maternal DNA (mitochondrial) of 90 mummies from Abusir el-Meleq in northern Egypt (near Cairo), which was the first reliable data using high-throughput DNA sequencing methods. Additionally, three of the mummies were also analyzed for Y-DNA. Two were assigned to West Asian J and one to haplogroup E1b1b1 both common in North Africa. The researchers cautioned that the affinities of the examined ancient Egyptian specimens may not be representative of those of all ancient Egyptians since they were from a single archaeological site. Whilst not conclusive since the few relatively older mummies only go back to the 18th-19th dynasty, the rest being from then up to late Roman period, the authors of this study said the Abusir el-Meleq mummies "closely resembled ancient and modern Near Eastern populations, especially those in the Levant." The genetics of the mummies remained remarkably consistent within this range even as different powers—including Nubians, Greeks, and Romans—conquered the empire." A wide range of mtDNA haplogroups were found including clades of J, U, H, HV, M, R0, R2, K, T, L, I, N, X, W. The authors of the study noted that the mummies at Abusir el-Meleq have 6–15% maternal sub-Saharan DNA while modern Egyptians have a little more sub-Saharan ancestry, 15% to 20%, suggesting some degree of influx after the end of the empire. Other genetic studies show greater levels of sub-Saharan African ancestry in modern southern Egyptian populations and anticipate that mummies from southern Egypt would show greater levels of sub-Saharan African ancestry. In 2018, the 4000-year-old mummified head of Djehutynakht, a governor in the Middle Kingdom of the 11th or 12th dynasty, was analyzed for mitochondrial DNA. The sequence of the mummy most closely resembles a U5a lineage from sample JK2903, a much more recent 2000-year-old skeleton from the Abusir el-Meleq site in Egypt, although no direct matches to the Djehutynakht sequence have been reported. Haplogroup U5 is also found in modern-day Berbers from the Siwa Oasis in Egypt. A 2008 article by C. Coudray, "The complex and diversified mitochondrial gene pool of Berber populations", recorded haplogroup U5 at 16.7% for the Siwa whereas haplogroup U6 is more common in other Berber populations to the west of Egypt. In 2020, Yehia Z Gad and other researchers of the Hawass team published results of an analysis of the maternal and paternal haplogroups of several 18th dynasty mummies, including Tutankhamun. Genetic analysis indicated the following haplogroups: Tutankhamun YDNA R1b / mtDNA K Akhenaten YDNA R1b / mtDNA K Amenhotep III YDNA R1b / mtDNA K Yuya G2a / mtDNA K Tiye mtDNA K Thuya mtDNA K The clade of R1b was not determined. A high frequency of R1b1a2 (R-V88) (26.9%) was observed among the Berbers from the Siwa Oasis. This haplogroup reaches its highest frequency in northern Cameroon, northern Nigeria, Chad, and Niger. Legacy The culture and monuments of ancient Egypt have left a lasting legacy on the world. Egyptian civilization significantly influenced the Kingdom of Kush and Meroë with both adopting Egyptian religious and architectural norms (hundreds of pyramids (6–30 meters high) were built in Egypt/Sudan), as well as using Egyptian writing as the basis of the Meroitic script. Meroitic is the oldest written language in Africa, other than Egyptian, and was used from the 2nd century BC until the early 5th century AD. The cult of the goddess Isis, for example, became popular in the Roman Empire, as obelisks and other relics were transported back to Rome. The Romans also imported building materials from Egypt to erect Egyptian-style structures. Early historians such as Herodotus, Strabo, and Diodorus Siculus studied and wrote about the land, which Romans came to view as a place of mystery. During the Middle Ages and the Renaissance, Egyptian pagan culture was in decline after the rise of Christianity and later Islam, but interest in Egyptian antiquity continued in the writings of medieval scholars such as Dhul-Nun al-Misri and al-Maqrizi. In the seventeenth and eighteenth centuries, European travelers and tourists brought back antiquities and wrote stories of their journeys, leading to a wave of Egyptomania across Europe. This renewed interest sent collectors to Egypt, who took, purchased, or were given many important antiquities. Napoleon arranged the first studies in Egyptology when he brought some 150 scientists and artists to study and document Egypt's natural history, which was published in the Description de l'Égypte. In the 20th century, the Egyptian Government and archaeologists alike recognized the importance of cultural respect and integrity in excavations. The Ministry of Tourism and Antiquities (formerly Supreme Council of Antiquities) now approves and oversees all excavations, which are aimed at finding information rather than treasure. The council also supervises museums and monument reconstruction programs designed to preserve the historical legacy of Egypt. See also Glossary of ancient Egypt artifacts Index of ancient Egypt–related articles Outline of ancient Egypt List of ancient Egyptians List of Ancient Egyptian inventions and discoveries Archaeology of Ancient Egypt British school of diffusionism Notes Citation References Further reading :de:Lexikon der Ägyptologie External links BBC History: Egyptiansprovides a reliable general overview and further links World History Encyclopedia on Egypt Ancient Egyptian Science: A Source Book Door Marshall Clagett, 1989 Ancient Egyptian Metallurgy A site that shows the history of Egyptian metalworking Napoleon on the Nile: Soldiers, Artists, and the Rediscovery of Egypt, Art History. Digital Egypt for Universities. Scholarly treatment with broad coverage and cross references (internal and external). Artifacts used extensively to illustrate topics. Priests of Ancient Egypt In-depth-information about Ancient Egypt's priests, religious services and temples. Much picture material and bibliography. In English and German. Ancient Egypt at History.com UCLA Encyclopedia of Egyptology Ancient Egypt and the Role of Women by Dr Joann Fletcher Full-length account of Ancient Egypt as part of history of the world Ancient Egypt Civilizations Egypt Former empires in Asia Ancient peoples History of Egypt History of the Mediterranean

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

896

https://en.wikipedia.org/wiki/Argon

Argon

Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in the Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust. Nearly all of the argon in the Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas. The name "argon" is derived from the Greek word , neuter singular form of meaning 'lazy' or 'inactive', as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. Its triple point temperature of 83.8058 K is a defining fixed point in the International Temperature Scale of 1990. Argon is extracted industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters. Characteristics Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas. Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a noble gas, it can form some compounds under various extreme conditions. Argon fluorohydride (HArF), a compound of argon with fluorine and hydrogen that is stable below , has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form clathrates with water when atoms of argon are trapped in a lattice of water molecules. Ions, such as , and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized. History Argon (Greek , neuter singular form of meaning "lazy" or "inactive") is named in reference to its chemical inactivity. This chemical property of this first noble gas to be discovered impressed the namers. An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air. They first accomplished this by replicating an experiment of Henry Cavendish's. They trapped a mixture of atmospheric air with additional oxygen in a test-tube (A) upside-down over a large quantity of dilute alkali solution (B), which in Cavendish's original experiment was potassium hydroxide, and conveyed a current through wires insulated by U-shaped glass tubes (CC) which sealed around the platinum wire electrodes, leaving the ends of the wires (DD) exposed to the gas and insulated from the alkali solution. The arc was powered by a battery of five Grove cells and a Ruhmkorff coil of medium size. The alkali absorbed the oxides of nitrogen produced by the arc and also carbon dioxide. They operated the arc until no more reduction of volume of the gas could be seen for at least an hour or two and the spectral lines of nitrogen disappeared when the gas was examined. The remaining oxygen was reacted with alkaline pyrogallate to leave behind an apparently non-reactive gas which they called argon. Before isolating the gas, they had determined that nitrogen produced from chemical compounds was 0.5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley. Each observed new lines in the emission spectrum of air that did not match known elements. Until 1957, the symbol for argon was "A", but now it is "Ar". Occurrence Argon constitutes 0.934% by volume and 1.288% by mass of the Earth's atmosphere. Air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation, a process that also produces purified nitrogen, oxygen, neon, krypton and xenon. The Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively. Isotopes The main isotopes of argon found on Earth are (99.6%), (0.34%), and (0.06%). Naturally occurring , with a half-life of 1.25 years, decays to stable (11.2%) by electron capture or positron emission, and also to stable (88.8%) by beta decay. These properties and ratios are used to determine the age of rocks by K–Ar dating. In the Earth's atmosphere, is made by cosmic ray activity, primarily by neutron capture of followed by two-neutron emission. In the subsurface environment, it is also produced through neutron capture by , followed by proton emission. is created from the neutron capture by followed by an alpha particle emission as a result of subsurface nuclear explosions. It has a half-life of 35 days. Between locations in the Solar System, the isotopic composition of argon varies greatly. Where the major source of argon is the decay of in rocks, will be the dominant isotope, as it is on Earth. Argon produced directly by stellar nucleosynthesis is dominated by the alpha-process nuclide . Correspondingly, solar argon contains 84.6% (according to solar wind measurements), and the ratio of the three isotopes 36Ar : 38Ar : 40Ar in the atmospheres of the outer planets is 8400 : 1600 : 1. This contrasts with the low abundance of primordial in Earth's atmosphere, which is only 31.5 ppmv (= 9340 ppmv × 0.337%), comparable with that of neon (18.18 ppmv) on Earth and with interplanetary gasses, measured by probes. The atmospheres of Mars, Mercury and Titan (the largest moon of Saturn) contain argon, predominantly as , and its content may be as high as 1.93% (Mars). The predominance of radiogenic is the reason the standard atomic weight of terrestrial argon is greater than that of the next element, potassium, a fact that was puzzling when argon was discovered. Mendeleev positioned the elements on his periodic table in order of atomic weight, but the inertness of argon suggested a placement before the reactive alkali metal. Henry Moseley later solved this problem by showing that the periodic table is actually arranged in order of atomic number (see History of the periodic table). Compounds Argon's complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized. The first argon compound with tungsten pentacarbonyl, W(CO)5Ar, was isolated in 1975. However it was not widely recognised at that time. In August 2000, another argon compound, argon fluorohydride (HArF), was formed by researchers at the University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride with caesium iodide. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first. It is stable up to 17 kelvins (−256 °C). The metastable dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010. Argon-36, in the form of argon hydride (argonium) ions, has been detected in interstellar medium associated with the Crab Nebula supernova; this was the first noble-gas molecule detected in outer space. Solid argon hydride (Ar(H2)2) has the same crystal structure as the MgZn2 Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H2 molecules in Ar(H2)2 dissociate above 175 GPa. Production Industrial Argon is extracted industrially by the fractional distillation of liquid air in a cryogenic air separation unit; a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and liquid oxygen, which boils at 90.2 K. About 700,000 tonnes of argon are produced worldwide every year. In radioactive decays 40Ar, the most abundant isotope of argon, is produced by the decay of 40K with a half-life of 1.25 years by electron capture or positron emission. Because of this, it is used in potassium–argon dating to determine the age of rocks. Applications Argon has several desirable properties: Argon is a chemically inert gas. Argon is the cheapest alternative when nitrogen is not sufficiently inert. Argon has low thermal conductivity. Argon has electronic properties (ionization and/or the emission spectrum) desirable for some applications. Other noble gases would be equally suitable for most of these applications, but argon is by far the cheapest. Argon is inexpensive, since it occurs naturally in air and is readily obtained as a byproduct of cryogenic air separation in the production of liquid oxygen and liquid nitrogen: the primary constituents of air are used on a large industrial scale. The other noble gases (except helium) are produced this way as well, but argon is the most plentiful by far. The bulk of argon applications arise simply because it is inert and relatively cheap. Industrial processes Argon is used in some high-temperature industrial processes where ordinarily non-reactive substances become reactive. For example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. For some of these processes, the presence of nitrogen or oxygen gases might cause defects within the material. Argon is used in some types of arc welding such as gas metal arc welding and gas tungsten arc welding, as well as in the processing of titanium and other reactive elements. An argon atmosphere is also used for growing crystals of silicon and germanium. Argon is used in the poultry industry to asphyxiate birds, either for mass culling following disease outbreaks, or as a means of slaughter more humane than electric stunning. Argon is denser than air and displaces oxygen close to the ground during inert gas asphyxiation. Its non-reactive nature makes it suitable in a food product, and since it replaces oxygen within the dead bird, argon also enhances shelf life. Argon is sometimes used for extinguishing fires where valuable equipment may be damaged by water or foam. Scientific research Liquid argon is used as the target for neutrino experiments and direct dark matter searches. The interaction between the hypothetical WIMPs and an argon nucleus produces scintillation light that is detected by photomultiplier tubes. Two-phase detectors containing argon gas are used to detect the ionized electrons produced during the WIMP–nucleus scattering. As with most other liquefied noble gases, argon has a high scintillation light yield (about 51 photons/keV), is transparent to its own scintillation light, and is relatively easy to purify. Compared to xenon, argon is cheaper and has a distinct scintillation time profile, which allows the separation of electronic recoils from nuclear recoils. On the other hand, its intrinsic beta-ray background is larger due to contamination, unless one uses argon from underground sources, which has much less contamination. Most of the argon in the Earth's atmosphere was produced by electron capture of long-lived ( + e− → + ν) present in natural potassium within the Earth. The activity in the atmosphere is maintained by cosmogenic production through the knockout reaction (n,2n) and similar reactions. The half-life of is only 269 years. As a result, the underground Ar, shielded by rock and water, has much less contamination. Dark-matter detectors currently operating with liquid argon include DarkSide, WArP, ArDM, microCLEAN and DEAP. Neutrino experiments include ICARUS and MicroBooNE, both of which use high-purity liquid argon in a time projection chamber for fine grained three-dimensional imaging of neutrino interactions. At Linköping University, Sweden, the inert gas is being utilized in a vacuum chamber in which plasma is introduced to ionize metallic films. This process results in a film usable for manufacturing computer processors. The new process would eliminate the need for chemical baths and use of expensive, dangerous and rare materials. Preservative Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents (argon has the European food additive code E938). Aerial oxidation, hydrolysis, and other chemical reactions that degrade the products are retarded or prevented entirely. High-purity chemicals and pharmaceuticals are sometimes packed and sealed in argon. In winemaking, argon is used in a variety of activities to provide a barrier against oxygen at the liquid surface, which can spoil wine by fueling both microbial metabolism (as with acetic acid bacteria) and standard redox chemistry. Argon is sometimes used as the propellant in aerosol cans. Argon is also used as a preservative for such products as varnish, polyurethane, and paint, by displacing air to prepare a container for storage. Since 2002, the American National Archives stores important national documents such as the Declaration of Independence and the Constitution within argon-filled cases to inhibit their degradation. Argon is preferable to the helium that had been used in the preceding five decades, because helium gas escapes through the intermolecular pores in most containers and must be regularly replaced. Laboratory equipment Argon may be used as the inert gas within Schlenk lines and gloveboxes. Argon is preferred to less expensive nitrogen in cases where nitrogen may react with the reagents or apparatus. Argon may be used as the carrier gas in gas chromatography and in electrospray ionization mass spectrometry; it is the gas of choice for the plasma used in ICP spectroscopy. Argon is preferred for the sputter coating of specimens for scanning electron microscopy. Argon gas is also commonly used for sputter deposition of thin films as in microelectronics and for wafer cleaning in microfabrication. Medical use Cryosurgery procedures such as cryoablation use liquid argon to destroy tissue such as cancer cells. It is used in a procedure called "argon-enhanced coagulation", a form of argon plasma beam electrosurgery. The procedure carries a risk of producing gas embolism and has resulted in the death of at least one patient. Blue argon lasers are used in surgery to weld arteries, destroy tumors, and correct eye defects. Argon has also been used experimentally to replace nitrogen in the breathing or decompression mix known as Argox, to speed the elimination of dissolved nitrogen from the blood. Lighting Incandescent lights are filled with argon, to preserve the filaments at high temperature from oxidation. It is used for the specific way it ionizes and emits light, such as in plasma globes and calorimetry in experimental particle physics. Gas-discharge lamps filled with pure argon provide lilac/violet light; with argon and some mercury, blue light. Argon is also used for blue and green argon-ion lasers. Miscellaneous uses Argon is used for thermal insulation in energy-efficient windows. Argon is also used in technical scuba diving to inflate a dry suit because it is inert and has low thermal conductivity. Argon is used as a propellant in the development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Compressed argon gas is allowed to expand, to cool the seeker heads of some versions of the AIM-9 Sidewinder missile and other missiles that use cooled thermal seeker heads. The gas is stored at high pressure. Argon-39, with a half-life of 269 years, has been used for a number of applications, primarily ice core and ground water dating. Also, potassium–argon dating and related argon-argon dating is used to date sedimentary, metamorphic, and igneous rocks. Argon has been used by athletes as a doping agent to simulate hypoxic conditions. In 2014, the World Anti-Doping Agency (WADA) added argon and xenon to the list of prohibited substances and methods, although at this time there is no reliable test for abuse. Safety Although argon is non-toxic, it is 38% more dense than air and therefore considered a dangerous asphyxiant in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless. A 1994 incident, in which a man was asphyxiated after entering an argon-filled section of oil pipe under construction in Alaska, highlights the dangers of argon tank leakage in confined spaces and emphasizes the need for proper use, storage and handling. See also Industrial gas Oxygen–argon ratio, a ratio of two physically similar gases, which has importance in various sectors. References Further reading On triple point pressure at 69 kPa. On triple point pressure at 83.8058 K. External links Argon at The Periodic Table of Videos (University of Nottingham) USGS Periodic Table – Argon Diving applications: Why Argon? Chemical elements E-number additives Noble gases Industrial gases

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

899

https://en.wikipedia.org/wiki/Actinium

Actinium

Actinium is a chemical element with the symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name emanium; the element got its name by being wrongly identified with a substance André-Louis Debierne found in 1899 and called actinium. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table. Together with polonium, radium, and radon, actinium was one of the first non-primordial radioactive elements to be isolated. A soft, silvery-white radioactive metal, actinium reacts rapidly with oxygen and moisture in air forming a white coating of actinium oxide that prevents further oxidation. As with most lanthanides and many actinides, actinium assumes oxidation state +3 in nearly all its chemical compounds. Actinium is found only in traces in uranium and thorium ores as the isotope 227Ac, which decays with a half-life of 21.772 years, predominantly emitting beta and sometimes alpha particles, and 228Ac, which is beta active with a half-life of 6.15 hours. One tonne of natural uranium in ore contains about 0.2 milligrams of actinium-227, and one tonne of thorium contains about 5 nanograms of actinium-228. The close similarity of physical and chemical properties of actinium and lanthanum makes separation of actinium from the ore impractical. Instead, the element is prepared, in milligram amounts, by the neutron irradiation of in a nuclear reactor. Owing to its scarcity, high price and radioactivity, actinium has no significant industrial use. Its current applications include a neutron source and an agent for radiation therapy. History André-Louis Debierne, a French chemist, announced the discovery of a new element in 1899. He separated it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel found in 1902 a substance similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances' half-lives determined by Debierne, Harriet Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different times. Articles published in the 1970s and later suggest that Debierne's results published in 1904 conflict with those reported in 1899 and 1900. Furthermore, the now-known chemistry of actinium precludes its presence as anything other than a minor constituent of Debierne's 1899 and 1900 results; in fact, the chemical properties he reported make it likely that he had, instead, accidentally identified protactinium, which would not be discovered for another fourteen years, only to have it disappear due to its hydrolysis and adsorption onto his laboratory equipment. This has led some authors to advocate that Giesel alone should be credited with the discovery. A less confrontational vision of scientific discovery is proposed by Adloff. He suggests that hindsight criticism of the early publications should be mitigated by the then nascent state of radiochemistry: highlighting the prudence of Debierne's claims in the original papers, he notes that nobody can contend that Debierne's substance did not contain actinium. Debierne, who is now considered by the vast majority of historians as the discoverer, lost interest in the element and left the topic. Giesel, on the other hand, can rightfully be credited with the first preparation of radiochemically pure actinium and with the identification of its atomic number 89. The name actinium originates from the Ancient Greek aktis, aktinos (ακτίς, ακτίνος), meaning beam or ray. Its symbol Ac is also used in abbreviations of other compounds that have nothing to do with actinium, such as acetyl, acetate and sometimes acetaldehyde. Properties Actinium is a soft, silvery-white, radioactive, metallic element. Its estimated shear modulus is similar to that of lead. Owing to its strong radioactivity, actinium glows in the dark with a pale blue light, which originates from the surrounding air ionized by the emitted energetic particles. Actinium has similar chemical properties to lanthanum and other lanthanides, and therefore these elements are difficult to separate when extracting from uranium ores. Solvent extraction and ion chromatography are commonly used for the separation. The first element of the actinides, actinium gave the group its name, much as lanthanum had done for the lanthanides. The group of elements is more diverse than the lanthanides and therefore it was not until 1945 that the most significant change to Dmitri Mendeleev's periodic table since the recognition of the lanthanides, the introduction of the actinides, was generally accepted after Glenn T. Seaborg's research on the transuranium elements (although it had been proposed as early as 1892 by British chemist Henry Bassett). Actinium reacts rapidly with oxygen and moisture in air forming a white coating of actinium oxide that impedes further oxidation. As with most lanthanides and actinides, actinium exists in the oxidation state +3, and the Ac3+ ions are colorless in solutions. The oxidation state +3 originates from the [Rn]6d17s2 electronic configuration of actinium, with three valence electrons that are easily donated to give the stable closed-shell structure of the noble gas radon. The rare oxidation state +2 is only known for actinium dihydride (AcH2); even this may in reality be an electride compound like its lighter congener LaH2 and thus have actinium(III). Ac3+ is the largest of all known tripositive ions and its first coordination sphere contains approximately 10.9 ± 0.5 water molecules. Chemical compounds Due to actinium's intense radioactivity, only a limited number of actinium compounds are known. These include: AcF3, AcCl3, AcBr3, AcOF, AcOCl, AcOBr, Ac2S3, Ac2O3, AcPO4 and Ac(NO3)3. Except for AcPO4, they are all similar to the corresponding lanthanum compounds. They all contain actinium in the oxidation state +3. In particular, the lattice constants of the analogous lanthanum and actinium compounds differ by only a few percent. Here a, b and c are lattice constants, No is space group number and Z is the number of formula units per unit cell. Density was not measured directly but calculated from the lattice parameters. Oxides Actinium oxide (Ac2O3) can be obtained by heating the hydroxide at 500 °C or the oxalate at 1100 °C, in vacuum. Its crystal lattice is isotypic with the oxides of most trivalent rare-earth metals. Halides Actinium trifluoride can be produced either in solution or in solid reaction. The former reaction is carried out at room temperature, by adding hydrofluoric acid to a solution containing actinium ions. In the latter method, actinium metal is treated with hydrogen fluoride vapors at 700 °C in an all-platinum setup. Treating actinium trifluoride with ammonium hydroxide at 900–1000 °C yields oxyfluoride AcOF. Whereas lanthanum oxyfluoride can be easily obtained by burning lanthanum trifluoride in air at 800 °C for an hour, similar treatment of actinium trifluoride yields no AcOF and only results in melting of the initial product. AcF3 + 2 NH3 + H2O → AcOF + 2 NH4F Actinium trichloride is obtained by reacting actinium hydroxide or oxalate with carbon tetrachloride vapors at temperatures above 960 °C. Similar to oxyfluoride, actinium oxychloride can be prepared by hydrolyzing actinium trichloride with ammonium hydroxide at 1000 °C. However, in contrast to the oxyfluoride, the oxychloride could well be synthesized by igniting a solution of actinium trichloride in hydrochloric acid with ammonia. Reaction of aluminium bromide and actinium oxide yields actinium tribromide: Ac2O3 + 2 AlBr3 → 2 AcBr3 + Al2O3 and treating it with ammonium hydroxide at 500 °C results in the oxybromide AcOBr. Other compounds Actinium hydride was obtained by reduction of actinium trichloride with potassium at 300 °C, and its structure was deduced by analogy with the corresponding LaH2 hydride. The source of hydrogen in the reaction was uncertain. Mixing monosodium phosphate (NaH2PO4) with a solution of actinium in hydrochloric acid yields white-colored actinium phosphate hemihydrate (AcPO4·0.5H2O), and heating actinium oxalate with hydrogen sulfide vapors at 1400 °C for a few minutes results in a black actinium sulfide Ac2S3. It may possibly be produced by acting with a mixture of hydrogen sulfide and carbon disulfide on actinium oxide at 1000 °C. Isotopes Naturally occurring actinium is composed of two radioactive isotopes; (from the radioactive family of ) and (a granddaughter of ). decays mainly as a beta emitter with a very small energy, but in 1.38% of cases it emits an alpha particle, so it can readily be identified through alpha spectrometry. Thirty-six radioisotopes have been identified, the most stable being with a half-life of 21.772 years, with a half-life of 10.0 days and with a half-life of 29.37 hours. All remaining radioactive isotopes have half-lives that are less than 10 hours and the majority of them have half-lives shorter than one minute. The shortest-lived known isotope of actinium is (half-life of 69 nanoseconds) which decays through alpha decay. Actinium also has two known meta states. The most significant isotopes for chemistry are 225Ac, 227Ac, and 228Ac. Purified comes into equilibrium with its decay products after about a half of year. It decays according to its 21.772-year half-life emitting mostly beta (98.62%) and some alpha particles (1.38%); the successive decay products are part of the actinium series. Owing to the low available amounts, low energy of its beta particles (maximum 44.8 keV) and low intensity of alpha radiation, is difficult to detect directly by its emission and it is therefore traced via its decay products. The isotopes of actinium range in atomic weight from 205 u () to 236 u (). Occurrence and synthesis Actinium is found only in traces in uranium ores – one tonne of uranium in ore contains about 0.2 milligrams of 227Ac – and in thorium ores, which contain about 5 nanograms of 228Ac per one tonne of thorium. The actinium isotope 227Ac is a transient member of the uranium-actinium series decay chain, which begins with the parent isotope 235U (or 239Pu) and ends with the stable lead isotope 207Pb. The isotope 228Ac is a transient member of the thorium series decay chain, which begins with the parent isotope 232Th and ends with the stable lead isotope 208Pb. Another actinium isotope (225Ac) is transiently present in the neptunium series decay chain, beginning with 237Np (or 233U) and ending with thallium (205Tl) and near-stable bismuth (209Bi); even though all primordial 237Np has decayed away, it is continuously produced by neutron knock-out reactions on natural 238U. The low natural concentration, and the close similarity of physical and chemical properties to those of lanthanum and other lanthanides, which are always abundant in actinium-bearing ores, render separation of actinium from the ore impractical, and complete separation was never achieved. Instead, actinium is prepared, in milligram amounts, by the neutron irradiation of in a nuclear reactor. ^{226}_{88}Ra + ^{1}_{0}n -> ^{227}_{88}Ra ->[\beta^-][42.2 \ \ce{min}] ^{227}_{89}Ac The reaction yield is about 2% of the radium weight. 227Ac can further capture neutrons resulting in small amounts of 228Ac. After the synthesis, actinium is separated from radium and from the products of decay and nuclear fusion, such as thorium, polonium, lead and bismuth. The extraction can be performed with thenoyltrifluoroacetone-benzene solution from an aqueous solution of the radiation products, and the selectivity to a certain element is achieved by adjusting the pH (to about 6.0 for actinium). An alternative procedure is anion exchange with an appropriate resin in nitric acid, which can result in a separation factor of 1,000,000 for radium and actinium vs. thorium in a two-stage process. Actinium can then be separated from radium, with a ratio of about 100, using a low cross-linking cation exchange resin and nitric acid as eluant. 225Ac was first produced artificially at the Institute for Transuranium Elements (ITU) in Germany using a cyclotron and at St George Hospital in Sydney using a linac in 2000. This rare isotope has potential applications in radiation therapy and is most efficiently produced by bombarding a radium-226 target with 20–30 MeV deuterium ions. This reaction also yields 226Ac which however decays with a half-life of 29 hours and thus does not contaminate 225Ac. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor in vacuum at a temperature between 1100 and 1300 °C. Higher temperatures resulted in evaporation of the product and lower ones lead to an incomplete transformation. Lithium was chosen among other alkali metals because its fluoride is most volatile. Applications Owing to its scarcity, high price and radioactivity, 227Ac currently has no significant industrial use, but 225Ac is currently being studied for use in cancer treatments such as targeted alpha therapies. 227Ac is highly radioactive and was therefore studied for use as an active element of radioisotope thermoelectric generators, for example in spacecraft. The oxide of 227Ac pressed with beryllium is also an efficient neutron source with the activity exceeding that of the standard americium-beryllium and radium-beryllium pairs. In all those applications, 227Ac (a beta source) is merely a progenitor which generates alpha-emitting isotopes upon its decay. Beryllium captures alpha particles and emits neutrons owing to its large cross-section for the (α,n) nuclear reaction: ^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}C + ^{1}_{0}n + \gamma The 227AcBe neutron sources can be applied in a neutron probe – a standard device for measuring the quantity of water present in soil, as well as moisture/density for quality control in highway construction. Such probes are also used in well logging applications, in neutron radiography, tomography and other radiochemical investigations. 225Ac is applied in medicine to produce in a reusable generator or can be used alone as an agent for radiation therapy, in particular targeted alpha therapy (TAT). This isotope has a half-life of 10 days, making it much more suitable for radiation therapy than 213Bi (half-life 46 minutes). Additionally, 225Ac decays to nontoxic 209Bi rather than stable but toxic lead, which is the final product in the decay chains of several other candidate isotopes, namely 227Th, 228Th, and 230U. Not only 225Ac itself, but also its daughters, emit alpha particles which kill cancer cells in the body. The major difficulty with application of 225Ac was that intravenous injection of simple actinium complexes resulted in their accumulation in the bones and liver for a period of tens of years. As a result, after the cancer cells were quickly killed by alpha particles from 225Ac, the radiation from the actinium and its daughters might induce new mutations. To solve this problem, 225Ac was bound to a chelating agent, such as citrate, ethylenediaminetetraacetic acid (EDTA) or diethylene triamine pentaacetic acid (DTPA). This reduced actinium accumulation in the bones, but the excretion from the body remained slow. Much better results were obtained with such chelating agents as HEHA () or DOTA () coupled to trastuzumab, a monoclonal antibody that interferes with the HER2/neu receptor. The latter delivery combination was tested on mice and proved to be effective against leukemia, lymphoma, breast, ovarian, neuroblastoma and prostate cancers. The medium half-life of 227Ac (21.77 years) makes it very convenient radioactive isotope in modeling the slow vertical mixing of oceanic waters. The associated processes cannot be studied with the required accuracy by direct measurements of current velocities (of the order 50 meters per year). However, evaluation of the concentration depth-profiles for different isotopes allows estimating the mixing rates. The physics behind this method is as follows: oceanic waters contain homogeneously dispersed 235U. Its decay product, 231Pa, gradually precipitates to the bottom, so that its concentration first increases with depth and then stays nearly constant. 231Pa decays to 227Ac; however, the concentration of the latter isotope does not follow the 231Pa depth profile, but instead increases toward the sea bottom. This occurs because of the mixing processes which raise some additional 227Ac from the sea bottom. Thus analysis of both 231Pa and 227Ac depth profiles allows researchers to model the mixing behavior. There are theoretical predictions that AcHx hydrides (in this case with very high pressure) are a candidate for a near room-temperature superconductor as they have Tc significantly higher than H3S, possibly near 250 K. Precautions 227Ac is highly radioactive and experiments with it are carried out in a specially designed laboratory equipped with a tight glove box. When actinium trichloride is administered intravenously to rats, about 33% of actinium is deposited into the bones and 50% into the liver. Its toxicity is comparable to, but slightly lower than that of americium and plutonium. For trace quantities, fume hoods with good aeration suffice; for gram amounts, hot cells with shielding from the intense gamma radiation emitted by 227Ac are necessary. See also Actinium series Notes References Bibliography Meyer, Gerd and Morss, Lester R. (1991) Synthesis of lanthanide and actinide compounds, Springer. External links Actinium at The Periodic Table of Videos (University of Nottingham) NLM Hazardous Substances Databank – Actinium, Radioactive Actinium in Chemical elements Actinides

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

902

https://en.wikipedia.org/wiki/Atom

Atom

An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across. They are so small that accurately predicting their behavior using classical physics—as if they were tennis balls, for example—is not possible due to quantum effects. Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, then the atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively – such atoms are called ions. The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by the nuclear force. This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force. In this case, the nucleus splits and leaves behind different elements. This is a form of nuclear decay. The number of protons in the nucleus is the atomic number and it defines to which chemical element the atom belongs. For example, any atom that contains 29 protons is copper. The number of neutrons defines the isotope of the element. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules or crystals. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature. Chemistry is the discipline that studies these changes. History of atomic theory In philosophy The basic idea that matter is made up of tiny, indivisible particles appears in many ancient cultures such as those of Greece and India. The word atom is derived from the ancient Greek word atomos (a combination of the negative term "a-" and "τομή," the term for "cut") that means "uncuttable". This ancient idea was based in philosophical reasoning rather than scientific reasoning; modern atomic theory is not based on these old concepts. Nonetheless, the term "atom" was used throughout the ages by thinkers who suspected that matter was ultimately granular in nature. It has since been discovered that "atoms" can be split, but the misnomer is still used. Dalton's law of multiple proportions In the early 1800s, the English chemist John Dalton compiled experimental data gathered by himself and other scientists and discovered a pattern now known as the "law of multiple proportions". He noticed that in chemical compounds which contain a particular chemical element, the content of that element in these compounds will differ by ratios of small whole numbers. This pattern suggested to Dalton that each chemical element combines with other elements by some basic and consistent unit of mass. For example, there are two types of tin oxide: one is a black powder that is 88.1% tin and 11.9% oxygen, and the other is a white powder that is 78.7% tin and 21.3% oxygen. Adjusting these figures, in the black oxide there is about 13.5 g of oxygen for every 100 g of tin, and in the white oxide there is about 27 g of oxygen for every 100 g of tin. 13.5 and 27 form a ratio of 1:2. In these oxides, for every tin atom there are one or two oxygen atoms respectively (SnO and SnO2). As a second example, Dalton considered two iron oxides: a black powder which is 78.1% iron and 21.9% oxygen, and a red powder which is 70.4% iron and 29.6% oxygen. Adjusting these figures, in the black oxide there is about 28 g of oxygen for every 100 g of iron, and in the red oxide there is about 42 g of oxygen for every 100 g of iron. 28 and 42 form a ratio of 2:3. In these respective oxides, for every two atoms of iron, there are two or three atoms of oxygen (Fe2O2 and Fe2O3). As a final example: nitrous oxide is 63.3% nitrogen and 36.7% oxygen, nitric oxide is 44.05% nitrogen and 55.95% oxygen, and nitrogen dioxide is 29.5% nitrogen and 70.5% oxygen. Adjusting these figures, in nitrous oxide there is 80 g of oxygen for every 140 g of nitrogen, in nitric oxide there is about 160 g of oxygen for every 140 g of nitrogen, and in nitrogen dioxide there is 320 g of oxygen for every 140 g of nitrogen. 80, 160, and 320 form a ratio of 1:2:4. The respective formulas for these oxides are N2O, NO, and NO2. Kinetic theory of gases In the late 18th century, a number of scientists found that they could better explain the behavior of gases by describing them as collections of sub-microscopic particles and modelling their behavior using statistics and probability. Unlike Dalton's atomic theory, the kinetic theory of gases describes not how gases react chemically with each other to form compounds, but how they behave physically: diffusion, viscosity, conductivity, pressure, etc. Brownian motion In 1827, botanist Robert Brown used a microscope to look at dust grains floating in water and discovered that they moved about erratically, a phenomenon that became known as "Brownian motion". This was thought to be caused by water molecules knocking the grains about. In 1905, Albert Einstein proved the reality of these molecules and their motions by producing the first statistical physics analysis of Brownian motion. French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of molecules, thereby providing physical evidence for the particle nature of matter. Discovery of the electron In 1897, J. J. Thomson discovered that cathode rays are not electromagnetic waves but made of particles that are 1,800 times lighter than hydrogen (the lightest atom). Thomson concluded that these particles came from the atoms within the cathode — they were subatomic particles. He called these new particles corpuscles but they were later renamed electrons. Thomson also showed that electrons were identical to particles given off by photoelectric and radioactive materials. It was quickly recognized that electrons are the particles that carry electric currents in metal wires. Thomson concluded that these electrons emerged from the very atoms of the cathode in his instruments, which meant that atoms are not indivisible as the name atomos suggests. Discovery of the nucleus J. J. Thomson thought that the negatively-charged electrons were distributed throughout the atom in a sea of positive charge that was distributed across the whole volume of the atom. This model is sometimes known as the plum pudding model. Ernest Rutherford and his colleagues Hans Geiger and Ernest Marsden came to have doubts about the Thomson model after they encountered difficulties when they tried to build an instrument to measure the charge-to-mass ratio of alpha particles (these are positively-charged particles emitted by certain radioactive substances such as radium). The alpha particles were being scattered by the air in the detection chamber, which made the measurements unreliable. Thomson had encountered a similar problem in his work on cathode rays, which he solved by creating a near-perfect vacuum in his instruments. Rutherford didn't think he'd run into this same problem because alpha particles are much heavier than electrons. According to Thomson's model of the atom, the positive charge in the atom is not concentrated enough to produce an electric field strong enough to deflect an alpha particle, and the electrons are so lightweight they should be pushed aside effortlessly by the much heavier alpha particles. Yet there was scattering, so Rutherford and his colleagues decided to investigate this scattering carefully. Between 1908 and 1913, Rutheford and his colleagues performed a series of experiments in which they bombarded thin foils of metal with alpha particles. They spotted alpha particles being deflected by angles greater than 90°. To explain this, Rutherford proposed that the positive charge of the atom is not distributed throughout the atom's volume as Thomson believed, but is concentrated in a tiny nucleus at the center. Only such an intense concentration of charge could produce an electric field strong enough to deflect the alpha particles as observed. Discovery of isotopes While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J. J. Thomson created a technique for isotope separation through his work on ionized gases, which subsequently led to the discovery of stable isotopes. Bohr model In 1913, the physicist Niels Bohr proposed a model in which the electrons of an atom were assumed to orbit the nucleus but could only do so in a finite set of orbits, and could jump between these orbits only in discrete changes of energy corresponding to absorption or radiation of a photon. This quantization was used to explain why the electrons' orbits are stable (given that normally, charges in acceleration, including circular motion, lose kinetic energy which is emitted as electromagnetic radiation, see synchrotron radiation) and why elements absorb and emit electromagnetic radiation in discrete spectra. Later in the same year Henry Moseley provided additional experimental evidence in favor of Niels Bohr's theory. These results refined Ernest Rutherford's and Antonius van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its (atomic) number in the periodic table. Until these experiments, atomic number was not known to be a physical and experimental quantity. That it is equal to the atomic nuclear charge remains the accepted atomic model today. Chemical bonds between atoms were explained by Gilbert Newton Lewis in 1916, as the interactions between their constituent electrons. As the chemical properties of the elements were known to largely repeat themselves according to the periodic law, in 1919 the American chemist Irving Langmuir suggested that this could be explained if the electrons in an atom were connected or clustered in some manner. Groups of electrons were thought to occupy a set of electron shells about the nucleus. The Bohr model of the atom was the first complete physical model of the atom. It described the overall structure of the atom, how atoms bond to each other, and predicted the spectral lines of hydrogen. Bohr's model was not perfect and was soon superseded by the more accurate Schrödinger model, but it was sufficient to evaporate any remaining doubts that matter is composed of atoms. For chemists, the idea of the atom had been a useful heuristic tool, but physicists had doubts as to whether matter really is made up of atoms as nobody had yet developed a complete physical model of the atom. The Schrödinger model The Stern–Gerlach experiment of 1922 provided further evidence of the quantum nature of atomic properties. When a beam of silver atoms was passed through a specially shaped magnetic field, the beam was split in a way correlated with the direction of an atom's angular momentum, or spin. As this spin direction is initially random, the beam would be expected to deflect in a random direction. Instead, the beam was split into two directional components, corresponding to the atomic spin being oriented up or down with respect to the magnetic field. In 1925, Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics (matrix mechanics). One year earlier, Louis de Broglie had proposed the de Broglie hypothesis: that all particles behave like waves to some extent, and in 1926 Erwin Schrödinger used this idea to develop the Schrödinger equation, a mathematical model of the atom (wave mechanics) that described the electrons as three-dimensional waveforms rather than point particles. A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at a given point in time; this became known as the uncertainty principle, formulated by Werner Heisenberg in 1927. In this concept, for a given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa. This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed. Discovery of the neutron The development of the mass spectrometer allowed the mass of atoms to be measured with increased accuracy. The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge. The chemist Francis William Aston used this instrument to show that isotopes had different masses. The atomic mass of these isotopes varied by integer amounts, called the whole number rule. The explanation for these different isotopes awaited the discovery of the neutron, an uncharged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus. Fission, high-energy physics and condensed matter In 1938, the German chemist Otto Hahn, a student of Rutherford, directed neutrons onto uranium atoms expecting to get transuranium elements. Instead, his chemical experiments showed barium as a product. A year later, Lise Meitner and her nephew Otto Frisch verified that Hahn's result were the first experimental nuclear fission. In 1944, Hahn received the Nobel Prize in Chemistry. Despite Hahn's efforts, the contributions of Meitner and Frisch were not recognized. In the 1950s, the development of improved particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies. Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. The standard model of particle physics was developed that so far has successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions. Structure Subatomic particles Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron. The electron is by far the least massive of these particles at , with a negative electrical charge and a size that is too small to be measured using available techniques. It was the lightest particle with a positive rest mass measured, until the discovery of neutrino mass. Under ordinary conditions, electrons are bound to the positively charged nucleus by the attraction created from opposite electric charges. If an atom has more or fewer electrons than its atomic number, then it becomes respectively negatively or positively charged as a whole; a charged atom is called an ion. Electrons have been known since the late 19th century, mostly thanks to J.J. Thomson; see history of subatomic physics for details. Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron, or . Neutrons are the heaviest of the three constituent particles, but their mass can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of —although the 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick. In the Standard Model of physics, electrons are truly elementary particles with no internal structure, whereas protons and neutrons are composite particles composed of elementary particles called quarks. There are two types of quarks in atoms, each having a fractional electric charge. Protons are composed of two up quarks (each with charge +) and one down quark (with a charge of −). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles. The quarks are held together by the strong interaction (or strong force), which is mediated by gluons. The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force, which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear force for more). The gluon is a member of the family of gauge bosons, which are elementary particles that mediate physical forces. Nucleus All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to  femtometres, where is the total number of nucleons. This is much smaller than the radius of the atom, which is on the order of 105 fm. The nucleons are bound together by a short-ranged attractive potential called the residual strong force. At distances smaller than 2.5 fm this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other. Atoms of the same element have the same number of protons, called the atomic number. Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay. The proton, the electron, and the neutron are classified as fermions. Fermions obey the Pauli exclusion principle which prohibits identical fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud. A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay, but with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus. The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3 to 10 keV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus. Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element. If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles, then the difference between these two values can be emitted as a type of usable energy (such as a gamma ray, or the kinetic energy of a beta particle), as described by Albert Einstein's mass-energy equivalence formula, , where is the mass loss and is the speed of light. This deficit is part of the binding energy of the new nucleus, and it is the non-recoverable loss of the energy that causes the fused particles to remain together in a state that requires this energy to separate. The fusion of two nuclei that create larger nuclei with lower atomic numbers than iron and nickel—a total nucleon number of about 60—is usually an exothermic process that releases more energy than is required to bring them together. It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decrease. That means fusion processes producing nuclei that have atomic numbers higher than about 26, and atomic masses higher than about 60, is an endothermic process. These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star. Electron cloud The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at greater separations. Electrons, like other particles, have properties of both a particle and a wave. The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital, a mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured. Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form. Orbitals can have one or more ring or node structures, and differ from each other in size, shape and orientation. Each atomic orbital corresponds to a particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines. The amount of energy needed to remove or add an electron—the electron binding energy—is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom, compared to 2.23 million eV for splitting a deuterium nucleus. Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals. Properties Nuclear properties By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single-proton element hydrogen up to the 118-proton element oganesson. All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (bismuth) is so slight as to be practically negligible. About 339 nuclides occur naturally on Earth, of which 252 (about 74%) have not been observed to decay, and are referred to as "stable isotopes". Only 90 nuclides are stable theoretically, while another 162 (bringing the total to 252) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 34 radioactive nuclides have half-lives longer than 100 million years, and are long-lived enough to have been present since the birth of the Solar System. This collection of 286 nuclides are known as primordial nuclides. Finally, an additional 53 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14). For 80 of the chemical elements, at least one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.2 stable isotopes per element. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes. Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 252 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10 and nitrogen-14. Also, only four naturally occurring, radioactive odd-odd nuclides have a half-life over a billion years: potassium-40, vanadium-50, lanthanum-138 and tantalum-180m. Most odd-odd nuclei are highly unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Mass The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). The actual mass of an atom at rest is often expressed in daltons (Da), also called the unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately . Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 Da. The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 Da), but this number will not be exactly an integer except (by definition) in the case of carbon-12. The heaviest stable atom is lead-208, with a mass of . As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. One mole of atoms of any element always has the same number of atoms (about ). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 Da, and so a mole of carbon-12 atoms weighs exactly 0.012 kg. Shape and size Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. This assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin. On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm. When subjected to external forces, like electrical fields, the shape of an atom may deviate from spherical symmetry. The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals, where large crystal-electrical fields may occur at low-symmetry lattice sites. Significant ellipsoidal deformations have been shown to occur for sulfur ions and chalcogen ions in pyrite-type compounds. Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they cannot be viewed using an optical microscope, although individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width. A single drop of water contains about 2 sextillion () atoms of oxygen, and twice the number of hydrogen atoms. A single carat diamond with a mass of contains about 10 sextillion (1022) atoms of carbon. If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple. Radioactive decay Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm. The most common forms of radioactive decay are: Alpha decay: this process is caused when the nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. The result of the emission is a new element with a lower atomic number. Beta decay (and electron capture): these processes are regulated by the weak force, and result from a transformation of a neutron into a proton, or a proton into a neutron. The neutron to proton transition is accompanied by the emission of an electron and an antineutrino, while proton to neutron transition (except in electron capture) causes the emission of a positron and a neutrino. The electron or positron emissions are called beta particles. Beta decay either increases or decreases the atomic number of the nucleus by one. Electron capture is more common than positron emission, because it requires less energy. In this type of decay, an electron is absorbed by the nucleus, rather than a positron emitted from the nucleus. A neutrino is still emitted in this process, and a proton changes to a neutron. Gamma decay: this process results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. The excited state of a nucleus which results in gamma emission usually occurs following the emission of an alpha or a beta particle. Thus, gamma decay usually follows alpha or beta decay. Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle. An analog of gamma emission which allows excited nuclei to lose energy in a different way, is internal conversion—a process that produces high-speed electrons that are not beta rays, followed by production of high-energy photons that are not gamma rays. A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission. Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. Magnetic moment Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is measured in units of the reduced Planck constant (ħ), with electrons, protons and neutrons all having spin ½ ħ, or "spin-½". In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin. The magnetic field produced by an atom—its magnetic moment—is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field, but the most dominant contribution comes from electron spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons. In ferromagnetic elements such as iron, cobalt and nickel, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a spontaneous process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field. The nucleus of an atom will have no spin when it has even numbers of both neutrons and protons, but for other cases of odd numbers, the nucleus may have a spin. Normally nuclei with spin are aligned in random directions because of thermal equilibrium, but for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging. Energy levels The potential energy of an electron in an atom is negative relative to when the distance from the nucleus goes to infinity; its dependence on the electron's position reaches the minimum inside the nucleus, roughly in inverse proportion to the distance. In the quantum-mechanical model, a bound electron can occupy only a set of states centered on the nucleus, and each state corresponds to a specific energy level; see time-independent Schrödinger equation for a theoretical explanation. An energy level can be measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). The lowest energy state of a bound electron is called the ground state, i.e. stationary state, while an electron transition to a higher level results in an excited state. The electron's energy increases along with n because the (average) distance to the nucleus increases. Dependence of the energy on is caused not by the electrostatic potential of the nucleus, but by interaction between electrons. For an electron to transition between two different states, e.g. ground state to first excited state, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels, according to the Niels Bohr model, what can be precisely calculated by the Schrödinger equation. Electrons jump between orbitals in a particle-like fashion. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon; see Electron properties. The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum. Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors. When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom spontaneously emit this energy as a photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. (An observer viewing the atoms from a view that does not include the continuous spectrum in the background, instead sees a series of emission lines from the photons emitted by the atoms.) Spectroscopic measurements of the strength and width of atomic spectral lines allow the composition and physical properties of a substance to be determined. Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin-orbit coupling, which is an interaction between the spin and motion of the outermost electron. When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect. If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon then move off in parallel and with matching phases. That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band. Valence and bonding behavior Valency is the combining power of an element. It is determined by the number of bonds it can form to other atoms or groups. The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. The number of valence electrons determines the bonding behavior with other atoms. Atoms tend to chemically react with each other in a manner that fills (or empties) their outer valence shells. For example, a transfer of a single electron between atoms is a useful approximation for bonds that form between atoms with one-electron more than a filled shell, and others that are one-electron short of a full shell, such as occurs in the compound sodium chloride and other chemical ionic salts. Many elements display multiple valences, or tendencies to share differing numbers of electrons in different compounds. Thus, chemical bonding between these elements takes many forms of electron-sharing that are more than simple electron transfers. Examples include the element carbon and the organic compounds. The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases. States Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases and plasmas. Within a state, a material can also exist in different allotropes. An example of this is solid carbon, which can exist as graphite or diamond. Gaseous allotropes exist as well, such as dioxygen and ozone. At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects, which are normally only observed at the atomic scale, become apparent on a macroscopic scale. This super-cooled collection of atoms then behaves as a single super atom, which may allow fundamental checks of quantum mechanical behavior. Identification While atoms are too small to be seen, devices such as the scanning tunneling microscope (STM) enable their visualization at the surfaces of solids. The microscope uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would be insurmountable in the classical perspective. Electrons tunnel through the vacuum between two biased electrodes, providing a tunneling current that is exponentially dependent on their separation. One electrode is a sharp tip ideally ending with a single atom. At each point of the scan of the surface the tip's height is adjusted so as to keep the tunneling current at a set value. How much the tip moves to and away from the surface is interpreted as the height profile. For low bias, the microscope images the averaged electron orbitals across closely packed energy levels—the local density of the electronic states near the Fermi level. Because of the distances involved, both electrodes need to be extremely stable; only then periodicities can be observed that correspond to individual atoms. The method alone is not chemically specific, and cannot identify the atomic species present at the surface. Atoms can be easily identified by their mass. If an atom is ionized by removing one of its electrons, its trajectory when it passes through a magnetic field will bend. The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis. The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry. Electron emission techniques such as X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), which measure the binding energies of the core electrons, are used to identify the atomic species present in a sample in a non-destructive way. With proper focusing both can be made area-specific. Another such method is electron energy loss spectroscopy (EELS), which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample. Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. These colors can be replicated using a gas-discharge lamp containing the same element. Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth. Origin and current state Baryonic matter forms about 4% of the total energy density of the observable Universe, with an average density of about 0.25 particles/m3 (mostly protons and electrons). Within a galaxy such as the Milky Way, particles have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3. The Sun is believed to be inside the Local Bubble, so the density in the solar neighborhood is only about 103 atoms/m3. Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium. Up to 95% of the Milky Way's baryonic matter are concentrated inside stars, where conditions are unfavorable for atomic matter. The total baryonic mass is about 10% of the mass of the galaxy; the remainder of the mass is an unknown dark matter. High temperature inside stars makes most "atoms" fully ionized, that is, separates all electrons from the nuclei. In stellar remnants—with exception of their surface layers—an immense pressure make electron shells impossible. Formation Electrons are thought to exist in the Universe since early stages of the Big Bang. Atomic nuclei forms in nucleosynthesis reactions. In about three minutes Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the Universe, and perhaps some of the beryllium and boron. Ubiquitousness and stability of atoms relies on their binding energy, which means that an atom has a lower energy than an unbound system of the nucleus and electrons. Where the temperature is much higher than ionization potential, the matter exists in the form of plasma—a gas of positively charged ions (possibly, bare nuclei) and electrons. When the temperature drops below the ionization potential, atoms become statistically favorable. Atoms (complete with bound electrons) became to dominate over charged particles 380,000 years after the Big Bang—an epoch called recombination, when the expanding Universe cooled enough to allow electrons to become attached to nuclei. Since the Big Bang, which produced no carbon or heavier elements, atomic nuclei have been combined in stars through the process of nuclear fusion to produce more of the element helium, and (via the triple alpha process) the sequence of elements from carbon up to iron; see stellar nucleosynthesis for details. Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected. Elements heavier than iron were produced in supernovae and colliding neutron stars through the r-process, and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei. Elements such as lead formed largely through the radioactive decay of heavier elements. Earth Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating. Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay. There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere. Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions. Of the transuranic elements—those with atomic numbers greater than 92—only plutonium and neptunium occur naturally on Earth. Transuranic elements have radioactive lifetimes shorter than the current age of the Earth and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust. Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore. The Earth contains approximately atoms. Although small numbers of independent atoms of noble gases exist, such as argon, neon, and helium, 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. At the surface of the Earth, an overwhelming majority of atoms combine to form various compounds, including water, salt, silicates and oxides. Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals. This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter. Rare and theoretical forms Superheavy elements All nuclides with atomic numbers higher than 82 (lead) are known to be radioactive. No nuclide with an atomic number exceeding 92 (uranium) exists on Earth as a primordial nuclide, and heavier elements generally have shorter half-lives. Nevertheless, an "island of stability" encompassing relatively long-lived isotopes of superheavy elements with atomic numbers 110 to 114 might exist. Predictions for the half-life of the most stable nuclide on the island range from a few minutes to millions of years. In any case, superheavy elements (with Z > 104) would not exist due to increasing Coulomb repulsion (which results in spontaneous fission with increasingly short half-lives) in the absence of any stabilizing effects. Exotic matter Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each other. Because of this, along with an imbalance between the number of matter and antimatter particles, the latter are rare in the universe. The first causes of this imbalance are not yet fully understood, although theories of baryogenesis may offer an explanation. As a result, no antimatter atoms have been discovered in nature. In 1996, the antimatter counterpart of the hydrogen atom (antihydrogen) was synthesized at the CERN laboratory in Geneva. Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. For example, an electron can be replaced by a more massive muon, forming a muonic atom. These types of atoms can be used to test fundamental predictions of physics. See also Notes References Bibliography Further reading External links Chemistry Articles containing video clips

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

915

https://en.wikipedia.org/wiki/Andrey%20Markov

Andrey Markov

Andrey Andreyevich Markov (14 June 1856 – 20 July 1922) was a Russian mathematician best known for his work on stochastic processes. A primary subject of his research later became known as Markov chains or Markov processes. Markov and his younger brother Vladimir Andreevich Markov (1871–1897) proved the Markov brothers' inequality. His son, another Andrey Andreyevich Markov (1903–1979), was also a notable mathematician, making contributions to constructive mathematics and recursive function theory. Biography Andrey Markov was born on 14 June 1856 in Russia. He attended the St. Petersburg Grammar School, where some teachers saw him as a rebellious student. In his academics he performed poorly in most subjects other than mathematics. Later in life he attended Saint Petersburg Imperial University (now Saint Petersburg State University). among his teachers were Yulian Sokhotski (differential calculus, higher algebra), Konstantin Posse (analytic geometry), Yegor Zolotarev (integral calculus), Pafnuty Chebyshev (number theory and probability theory), Aleksandr Korkin (ordinary and partial differential equations), Mikhail Okatov (mechanism theory), Osip Somov (mechanics), and Nikolai Budajev (descriptive and higher geometry). He completed his studies at the university and was later asked if he would like to stay and have a career as a Mathematician. He later taught at high schools and continued his own mathematical studies. In this time he found a practical use for his mathematical skills. He figured out that he could use chains to model the alliteration of vowels and consonants in Russian literature. He also contributed to many other mathematical aspects in his time. He died at age 66 on 20 July 1922. Timeline In 1877, Markov was awarded a gold medal for his outstanding solution of the problem About Integration of Differential Equations by Continued Fractions with an Application to the Equation . During the following year, he passed the candidate's examinations, and he remained at the university to prepare for a lecturer's position. In April 1880, Markov defended his master's thesis "On the Binary Square Forms with Positive Determinant", which was directed by Aleksandr Korkin and Yegor Zolotarev. Four years later in 1884, he defended his doctoral thesis titled "On Certain Applications of the Algebraic Continuous Fractions". His pedagogical work began after the defense of his master's thesis in autumn 1880. As a privatdozent he lectured on differential and integral calculus. Later he lectured alternately on "introduction to analysis", probability theory (succeeding Chebyshev, who had left the university in 1882) and the calculus of differences. From 1895 through 1905 he also lectured in differential calculus. One year after the defense of his doctoral thesis, Markov was appointed extraordinary professor (1886) and in the same year he was elected adjunct to the Academy of Sciences. In 1890, after the death of Viktor Bunyakovsky, Markov became an extraordinary member of the academy. His promotion to an ordinary professor of St. Petersburg University followed in the fall of 1894. In 1896, Markov was elected an ordinary member of the academy as the successor of Chebyshev. In 1905, he was appointed merited professor and was granted the right to retire, which he did immediately. Until 1910, however, he continued to lecture in the calculus of differences. In connection with student riots in 1908, professors and lecturers of St. Petersburg University were ordered to monitor their students. Markov refused to accept this decree, and he wrote an explanation in which he declined to be an "agent of the governance". Markov was removed from further teaching duties at St. Petersburg University, and hence he decided to retire from the university. Markov was an atheist. In 1912, he protested Leo Tolstoy's excommunication from the Russian Orthodox Church by requesting his own excommunication. The Church complied with his request. In 1913, the council of St. Petersburg elected nine scientists honorary members of the university. Markov was among them, but his election was not affirmed by the minister of education. The affirmation only occurred four years later, after the February Revolution in 1917. Markov then resumed his teaching activities and lectured on probability theory and the calculus of differences until his death in 1922. See also List of things named after Andrey Markov Chebyshev–Markov–Stieltjes inequalities Gauss–Markov theorem Gauss–Markov process Hidden Markov model Markov blanket Markov chain Markov decision process Markov's inequality Markov brothers' inequality Markov information source Markov network Markov number Markov property Markov process Stochastic matrix (also known as Markov matrix) Subjunctive possibility Notes References Further reading А. А. Марков. "Распространение закона больших чисел на величины, зависящие друг от друга". "Известия Физико-математического общества при Казанском университете", 2-я серия, том 15, с. 135–156, 1906. A. A. Markov. "Extension of the limit theorems of probability theory to a sum of variables connected in a chain". reprinted in Appendix B of: R. Howard. Dynamic Probabilistic Systems, volume 1: Markov Chains. John Wiley and Sons, 1971. External links Markov, Andrei Andreyevich Markov, Andrei Andreyevich 19th-century Russian mathematicians 20th-century Russian mathematicians Russian atheists Former Russian Orthodox Christians Probability theorists Saint Petersburg State University alumni Full members of the Saint Petersburg Academy of Sciences Full Members of the Russian Academy of Sciences (1917–1925) People from Ryazan Russian statisticians

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

924

https://en.wikipedia.org/wiki/A.%20A.%20Milne

A. A. Milne

Alan Alexander Milne (; 18 January 1882 – 31 January 1956) was an English author, best known for his books about the teddy bear Winnie-the-Pooh and for various poems. Milne was a noted writer, primarily as a playwright, before the huge success of Pooh overshadowed all his previous work. Milne served in both World Wars, joining the British Army in World War I, and as a captain of the British Home Guard in World War II. He was the father of bookseller Christopher Robin Milne, upon whom the character Christopher Robin is based. Early life and military career Alan Alexander Milne was born in Kilburn, London, to John Vine Milne, who was born in England, and Sarah Marie Milne (née Heginbotham). He grew up at Henley House School, 6/7 Mortimer Road (now Crescent), Kilburn, a small independent school run by his father. One of his teachers was H. G. Wells, who taught there in 1889–90. Milne attended Westminster School and Trinity College, Cambridge, where he studied on a mathematics scholarship, graduating with a B.A. in Mathematics in 1903. He edited and wrote for Granta, a student magazine. He collaborated with his brother Kenneth and their articles appeared over the initials AKM. Milne's work came to the attention of the leading British humour magazine Punch, where Milne was to become a contributor and later an assistant editor. Considered a talented cricket fielder, Milne played for two amateur teams that were largely composed of British writers: the Allahakbarries and the Authors XI. His teammates included fellow writers J. M. Barrie, Arthur Conan Doyle and P. G. Wodehouse. Milne joined the British Army in World War I and served as an officer in the Royal Warwickshire Regiment and later, after a debilitating illness, the Royal Corps of Signals. He was commissioned into the 4th Battalion, Royal Warwickshire Regiment, on 1 February 1915 as a second lieutenant (on probation). His commission was confirmed on 20 December 1915. On 7 July 1916, he was injured in the Battle of the Somme and invalided back to England. Having recuperated, he was recruited into Military Intelligence to write propaganda articles for MI7 (b) between 1916 and 1918. He was discharged on 14 February 1919, and settled in Mallord Street, Chelsea. He relinquished his commission on 19 February 1920, retaining the rank of lieutenant. After the war, he wrote a denunciation of war titled Peace with Honour (1934), which he retracted somewhat with 1940's War with Honour. During World War II, Milne was one of the most prominent critics of fellow English writer (and Authors XI cricket teammate) P. G. Wodehouse, who was captured at his country home in France by the Nazis and imprisoned for a year. Wodehouse made radio broadcasts about his internment, which were broadcast from Berlin. Although the light-hearted broadcasts made fun of the Germans, Milne accused Wodehouse of committing an act of near treason by cooperating with his country's enemy. Wodehouse got some revenge on his former friend (e.g. in The Mating Season) by creating fatuous parodies of the Christopher Robin poems in some of his later stories, and claiming that Milne "was probably jealous of all other writers.... But I loved his stuff." Milne married Dorothy "Daphne" de Sélincourt (1890–1971) in 1913 and their son Christopher Robin Milne was born in 1920. In 1925, Milne bought a country home, Cotchford Farm, in Hartfield, East Sussex. During World War II, Milne was a captain in the British Home Guard in Hartfield & Forest Row, insisting on being plain "Mr. Milne" to the members of his platoon. He retired to the farm after a stroke and brain surgery in 1952 left him an invalid, and by August 1953, "he seemed very old and disenchanted." Milne died in January 1956, aged 74. Literary career 1903 to 1925 After graduating from Cambridge University in 1903, A. A. Milne contributed humorous verse and whimsical essays to Punch, joining the staff in 1906 and becoming an assistant editor. During this period he published 18 plays and three novels, including the murder mystery The Red House Mystery (1922). His son was born in August 1920 and in 1924 Milne produced a collection of children's poems, When We Were Very Young, which were illustrated by Punch staff cartoonist E. H. Shepard. A collection of short stories for children A Gallery of Children, and other stories that became part of the Winnie-the-Pooh books, were first published in 1925. Milne was an early screenwriter for the nascent British film industry, writing four stories filmed in 1920 for the company Minerva Films (founded in 1920 by the actor Leslie Howard and his friend and story editor Adrian Brunel). These were The Bump, starring Aubrey Smith; Twice Two; Five Pound Reward; and Bookworms. Some of these films survive in the archives of the British Film Institute. Milne had met Howard when the actor starred in Milne's play Mr Pim Passes By in London. Looking back on this period (in 1926), Milne observed that when he told his agent that he was going to write a detective story, he was told that what the country wanted from a "Punch humorist" was a humorous story; when two years later he said he was writing nursery rhymes, his agent and publisher were convinced he should write another detective story; and after another two years, he was being told that writing a detective story would be in the worst of taste given the demand for children's books. He concluded that "the only excuse which I have yet discovered for writing anything is that I want to write it; and I should be as proud to be delivered of a Telephone Directory con amore as I should be ashamed to create a Blank Verse Tragedy at the bidding of others." 1926 to 1928 Milne is most famous for his two Pooh books about a boy named Christopher Robin after his son, Christopher Robin Milne (1920–1996), and various characters inspired by his son's stuffed animals, most notably the bear named Winnie-the-Pooh. Christopher Robin Milne's stuffed bear, originally named Edward, was renamed Winnie after a Canadian black bear named Winnie (after Winnipeg), which was used as a military mascot in World War I, and left to London Zoo during the war. "The Pooh" comes from a swan the young Milne named "Pooh". E. H. Shepard illustrated the original Pooh books, using his own son's teddy Growler ("a magnificent bear") as the model. The rest of Christopher Robin Milne's toys, Piglet, Eeyore, Kanga, Roo and Tigger, were incorporated into A. A. Milne's stories, and two more characters – Rabbit and Owl – were created by Milne's imagination. Christopher Robin Milne's own toys are now on display in New York where 750,000 people visit them every year. The fictional Hundred Acre Wood of the Pooh stories derives from Five Hundred Acre Wood in Ashdown Forest in East Sussex, South East England, where the Pooh stories were set. Milne lived on the northern edge of the forest at Cotchford Farm, , and took his son walking there. E. H. Shepard drew on the landscapes of Ashdown Forest as inspiration for many of the illustrations he provided for the Pooh books. The adult Christopher Robin commented: "Pooh's Forest and Ashdown Forest are identical." Popular tourist locations at Ashdown Forest include: Galleon's Lap, The Enchanted Place, the Heffalump Trap and Lone Pine, Eeyore’s Sad and Gloomy Place, and the wooden Pooh Bridge where Pooh and Piglet invented Poohsticks. Not yet known as Pooh, he made his first appearance in a poem, "Teddy Bear", published in Punch magazine in February 1924 and republished in When We Were Very Young. Pooh first appeared in the London Evening News on Christmas Eve, 1925, in a story called "The Wrong Sort of Bees". Winnie-the-Pooh was published in 1926, followed by The House at Pooh Corner in 1928. A second collection of nursery rhymes, Now We Are Six, was published in 1927. All four books were illustrated by E. H. Shepard. Milne also published four plays in this period. He also "gallantly stepped forward" to contribute a quarter of the costs of dramatising P. G. Wodehouse's A Damsel in Distress. The World of Pooh won the Lewis Carroll Shelf Award in 1958. 1929 onwards The success of his children's books was to become a source of considerable annoyance to Milne, whose self-avowed aim was to write whatever he pleased and who had, until then, found a ready audience for each change of direction: he had freed pre-war Punch from its ponderous facetiousness; he had made a considerable reputation as a playwright (like his idol J. M. Barrie) on both sides of the Atlantic; he had produced a witty piece of detective writing in The Red House Mystery (although this was severely criticised by Raymond Chandler for the implausibility of its plot in his essay The Simple Art of Murder in the eponymous collection that appeared in 1950). But once Milne had, in his own words, "said goodbye to all that in 70,000 words" (the approximate length of his four principal children's books), he had no intention of producing any reworkings lacking in originality, given that one of the sources of inspiration, his son, was growing older. Another reason Milne stopped writing children's books, and especially about Winnie-the-Pooh, was that he felt "amazement and disgust" over the fame his son was exposed to, and said that "I feel that the legal Christopher Robin has already had more publicity than I want for him. I do not want CR Milne to ever wish that his name were Charles Robert." In his literary home, Punch, where the When We Were Very Young verses had first appeared, Methuen continued to publish whatever Milne wrote, including the long poem "The Norman Church" and an assembly of articles entitled Year In, Year Out (which Milne likened to a benefit night for the author). In 1930, Milne adapted Kenneth Grahame's novel The Wind in the Willows for the stage as Toad of Toad Hall. The title was an implicit admission that such chapters as Chapter 7, "The Piper at the Gates of Dawn," could not survive translation to the theatre. A special introduction written by Milne is included in some editions of Grahame's novel. Milne and his wife became estranged from their son, who came to resent what he saw as his father's exploitation of his childhood and came to hate the books that had thrust him into the public eye. Christopher's marriage to his first cousin, Lesley de Sélincourt, distanced him still further from his parents – Lesley's father and Christopher's mother had not spoken to each other for 30 years. Death and legacy Commemoration A. A. Milne died at his home in Hartfield, Sussex, on 31 January 1956, nearly two weeks after his 74th birthday. After a memorial service in London, his ashes were scattered in a crematorium's memorial garden in Brighton. The rights to A. A. Milne's Pooh books were left to four beneficiaries: his family, the Royal Literary Fund, Westminster School and the Garrick Club. After Milne's death in 1956, thirteen days after his 74th birthday, his widow sold her rights to the Pooh characters to Stephen Slesinger, whose widow sold the rights after Slesinger's death to the Walt Disney Company, which has made many Pooh cartoon movies, a Disney Channel television show, as well as Pooh-related merchandise. In 2001, the other beneficiaries sold their interest in the estate to the Disney Corporation for $350m. Previously Disney had been paying twice-yearly royalties to these beneficiaries. The estate of E. H. Shepard also received a sum in the deal. The UK copyright on the text of the original Winnie the Pooh books expires on 1 January 2027; at the beginning of the year after the 70th anniversary of the author's death (PMA-70), and has already expired in those countries with a PMA-50 rule. This applies to all of Milne's works except those first published posthumously. The illustrations in the Pooh books will remain under copyright until the same amount of time has passed, after the illustrator's death; in the UK, this will be on 1 January 2047. In the United States, copyright will not expire until 95 years after publication for each of Milne's books first published before 1978, but this includes the illustrations. In 2008, a collection of original illustrations featuring Winnie-the-Pooh and his animal friends sold for more than £1.2 million at auction in Sotheby's, London. Forbes magazine ranked Winnie the Pooh the most valuable fictional character in 2002; Winnie the Pooh merchandising products alone had annual sales of more than $5.9 billion. In 2005, Winnie the Pooh generated $6 billion, a figure surpassed only by Mickey Mouse. A memorial plaque in Ashdown Forest, unveiled by Christopher Robin in 1979, commemorates the work of A. A. Milne and Shepard in creating the world of Pooh. Milne once wrote of Ashdown Forest: "In that enchanted place on the top of the forest a little boy and his bear will always be playing." In 2003, Winnie the Pooh was listed at number 7 on the BBC's poll The Big Read which determined the UK's "best-loved novels" of all time. In 2006, Winnie the Pooh received a star on the Hollywood Walk of Fame, marking the 80th birthday of Milne's creation. That same year a UK poll saw Winnie the Pooh voted onto the list of icons of England. Marking the 90th anniversary of Milne's creation of the character, and the 90th birthday of Elizabeth II, in 2016 a new story sees Winnie the Pooh meet the Queen at Buckingham Palace. The illustrated and audio adventure is titled Winnie-the-Pooh Meets the Queen, and has been narrated by actor Jim Broadbent. Also in 2016, a new character, a Penguin, was unveiled in The Best Bear in All the World, which was inspired by a long-lost photograph of Milne and his son Christopher with a toy penguin. Several of Milne's children's poems were set to music by the composer Harold Fraser-Simson. His poems have been parodied many times, including with the books When We Were Rather Older and Now We Are Sixty. The 1963 film The King's Breakfast was based on Milne's poem of the same name. The Pooh books were used as the basis for two academic satires by Frederick C Crews: 'The Pooh Perplex'(1963–4) and 'Postmodern Pooh'(2002). An exhibition entitled "Winnie-the-Pooh: Exploring a Classic" appeared at the V & A from 9 December 2017 to 8 April 2018. An elementary school in Houston, Texas, United States, operated by the Houston Independent School District (HISD), is named after Milne. The school, A. A. Milne Elementary School in Brays Oaks, opened in 1991. Archive The bulk of A. A. Milne's papers are housed at the Harry Ransom Center at the University of Texas at Austin. The collection, established at the center in 1964, consists of manuscript drafts and fragments for over 150 of Milne's works, as well as correspondence, legal documents, genealogical records, and some personal effects. The library division holds several books formerly belonging to Milne and his wife Dorothy. The Harry Ransom Center also has small collections of correspondence from Christopher Robin Milne and Milne's frequent illustrator Ernest Shepard. The original manuscripts for Winnie the Pooh and The House at Pooh Corner are archived separately at Trinity College Library, Cambridge. Religious views Milne did not speak out much on the subject of religion, although he used religious terms to explain his decision, while remaining a pacifist, to join the British Home Guard: "In fighting Hitler," he wrote, "we are truly fighting the Devil, the Anti-Christ ... Hitler was a crusader against God." His best known comment on the subject was recalled on his death: He wrote in the poem "Explained": He also wrote in the poem "Vespers": Works Novels Lovers in London (1905. Some consider this more of a short story collection; Milne did not like it and considered The Day's Play as his first book.) Once on a Time (1917) Mr. Pim (1921) (A novelisation of his 1919 play Mr. Pim Passes By) The Red House Mystery (1922). Serialised: London (Daily News), serialised daily from 3 to 28 August 1921 Two People (1931) (Inside jacket claims this is Milne's first attempt at a novel.) Four Days' Wonder (1933) Chloe Marr (1946) Non-fiction Peace With Honour (1934) It's Too Late Now: The Autobiography of a Writer (1939) War With Honour (1940) War Aims Unlimited (1941) Year In, Year Out (1952) (illustrated by E. H. Shepard) Punch articles The Day's Play (1910) The Holiday Round (1912) Once a Week (1914) The Sunny Side (1921) Those Were the Days (1929) [The four volumes above, compiled] Newspaper articles and book introductions The Chronicles of Clovis by "Saki" (1911) [Introduction to] Not That It Matters (1919) If I May (1920) By Way of Introduction (1929) ‘'Women and Children First!’’. John Bull, 10 November 1934 It Depends on the Book (1943, in September issue of Red Cross Newspaper The Prisoner of War) Story collections for children A Gallery of Children (1925) Winnie-the-Pooh (1926) (illustrated by Ernest H. Shepard) The House at Pooh Corner (1928) (illustrated by E. H. Shepard) Short Stories Poetry collections for children When We Were Very Young (1924) (illustrated by E. H. Shepard) Now We Are Six (1927) (illustrated by E. H. Shepard) Story collections The Secret and other stories (1929) The Birthday Party (1948) A Table Near the Band (1950) Poetry When We Were Very Young (1924) (illustrated by E. H. Shepard) For the Luncheon Interval (1925) [poems from Punch] Now We Are Six (1927) (illustrated by E. H. Shepard) Behind the Lines (1940) The Norman Church (1948) Screenplays and plays Wurzel-Flummery (1917) Belinda (1918) The Boy Comes Home (1918) Make-Believe (1918) (children's play) The Camberley Triangle (1919) Mr. Pim Passes By (1919) The Red Feathers (1920) The Romantic Age (1920) The Stepmother (1920) The Truth About Blayds (1920) The Bump (1920, Minerva Films), starring C. Aubrey Smith and Faith Celli Twice Two (1920, Minerva Films) Five Pound Reward (1920, Minerva Films) Bookworms (1920, Minerva Films) The Great Broxopp (1921) The Dover Road (1921) The Lucky One (1922) The Truth About Blayds (1922) The Artist: A Duologue (1923) Give Me Yesterday (1923) (a.k.a. Success in the UK) Ariadne (1924) The Man in the Bowler Hat: A Terribly Exciting Affair (1924) To Have the Honour (1924) Portrait of a Gentleman in Slippers (1926) Success (1926) Miss Marlow at Play (1927) Winnie the Pooh. Written specially by Milne for a 'Winnie the Pooh Party' in aid of the National Mother-Saving Campaign, and performed once at Seaford House on 17 March 1928 The Fourth Wall or The Perfect Alibi (1928) (later adapted for the film Birds of Prey (1930), directed by Basil Dean) The Ivory Door (1929) Toad of Toad Hall (1929) (adaptation of The Wind in the Willows) Michael and Mary (1930) Other People's Lives (1933) (a.k.a. They Don't Mean Any Harm) Miss Elizabeth Bennet (1936) [based on Pride and Prejudice] Sarah Simple (1937) Gentleman Unknown (1938) The General Takes Off His Helmet (1939) in The Queen's Book of the Red Cross The Ugly Duckling (1941) Before the Flood (1951). Portrayal Milne is portrayed by Domhnall Gleeson in Goodbye Christopher Robin, a 2017 film. In the 2018 fantasy film Christopher Robin, an extension of the Disney Winnie the Pooh franchise, Tristan Sturrock plays A.A. Milne. References Further reading Thwaite, Ann. A.A. Milne: His Life. London: Faber and Faber, 1990. Toby, Marlene. A.A. Milne, Author of Winnie-the-Pooh. Chicago: Children's Press, 1995. External links A. A. Milne Papers at the Harry Ransom Center Works by A. A. Milne at BiblioWiki (Canada) includes the complete text of the four Pooh books Portraits of A. A. Milne in the National Portrait Gallery Essays by Milne at Quotidiana.org Milne extract in The Guardian Profile at Just-Pooh.com A. A. Milne at poeticous.com AA Milne | Books | The Guardian Finding aid to the A.A. Milne letters at Columbia University Rare Book & Manuscript Library 1882 births 1956 deaths English people of Scottish descent People from Hampstead People from Kilburn, London 20th-century British dramatists and playwrights 20th-century British short story writers 20th-century English novelists 20th-century English poets Alumni of Trinity College, Cambridge British Army personnel of World War I British Home Guard officers Royal Warwickshire Fusiliers officers English children's writers Members of the Detection Club People educated at Westminster School, London Punch (magazine) people English male poets Winnie-the-Pooh Writers from London English male novelists Children's poets Royal Corps of Signals officers Military personnel from London

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

928

https://en.wikipedia.org/wiki/Axiom

Axiom

An axiom, postulate, or assumption is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Ancient Greek word (), meaning 'that which is thought worthy or fit' or 'that which commends itself as evident'. The term has subtle differences in definition when used in the context of different fields of study. As defined in classic philosophy, an axiom is a statement that is so evident or well-established, that it is accepted without controversy or question. As used in modern logic, an axiom is a premise or starting point for reasoning. As used in mathematics, the term axiom is used in two related but distinguishable senses: "logical axioms" and "non-logical axioms". Logical axioms are usually statements that are taken to be true within the system of logic they define and are often shown in symbolic form (e.g., (A and B) implies A), while non-logical axioms (e.g., ) are actually substantive assertions about the elements of the domain of a specific mathematical theory (such as arithmetic). When used in the latter sense, "axiom", "postulate", and "assumption" may be used interchangeably. In most cases, a non-logical axiom is simply a formal logical expression used in deduction to build a mathematical theory, and might or might not be self-evident in nature (e.g., parallel postulate in Euclidean geometry). To axiomatize a system of knowledge is to show that its claims can be derived from a small, well-understood set of sentences (the axioms), and there may be multiple ways to axiomatize a given mathematical domain. Any axiom is a statement that serves as a starting point from which other statements are logically derived. Whether it is meaningful (and, if so, what it means) for an axiom to be "true" is a subject of debate in the philosophy of mathematics. Etymology The word axiom comes from the Greek word (axíōma), a verbal noun from the verb (axioein), meaning "to deem worthy", but also "to require", which in turn comes from (áxios), meaning "being in balance", and hence "having (the same) value (as)", "worthy", "proper". Among the ancient Greek philosophers an axiom was a claim which could be seen to be self-evidently true without any need for proof. The root meaning of the word postulate is to "demand"; for instance, Euclid demands that one agree that some things can be done (e.g., any two points can be joined by a straight line). Ancient geometers maintained some distinction between axioms and postulates. While commenting on Euclid's books, Proclus remarks that "Geminus held that this [4th] Postulate should not be classed as a postulate but as an axiom, since it does not, like the first three Postulates, assert the possibility of some construction but expresses an essential property." Boethius translated 'postulate' as petitio and called the axioms notiones communes but in later manuscripts this usage was not always strictly kept. Historical development Early Greeks The logico-deductive method whereby conclusions (new knowledge) follow from premises (old knowledge) through the application of sound arguments (syllogisms, rules of inference) was developed by the ancient Greeks, and has become the core principle of modern mathematics. Tautologies excluded, nothing can be deduced if nothing is assumed. Axioms and postulates are thus the basic assumptions underlying a given body of deductive knowledge. They are accepted without demonstration. All other assertions (theorems, in the case of mathematics) must be proven with the aid of these basic assumptions. However, the interpretation of mathematical knowledge has changed from ancient times to the modern, and consequently the terms axiom and postulate hold a slightly different meaning for the present day mathematician, than they did for Aristotle and Euclid. The ancient Greeks considered geometry as just one of several sciences, and held the theorems of geometry on par with scientific facts. As such, they developed and used the logico-deductive method as a means of avoiding error, and for structuring and communicating knowledge. Aristotle's posterior analytics is a definitive exposition of the classical view. An "axiom", in classical terminology, referred to a self-evident assumption common to many branches of science. A good example would be the assertion that When an equal amount is taken from equals, an equal amount results. At the foundation of the various sciences lay certain additional hypotheses that were accepted without proof. Such a hypothesis was termed a postulate. While the axioms were common to many sciences, the postulates of each particular science were different. Their validity had to be established by means of real-world experience. Aristotle warns that the content of a science cannot be successfully communicated if the learner is in doubt about the truth of the postulates. The classical approach is well-illustrated by Euclid's Elements, where a list of postulates is given (common-sensical geometric facts drawn from our experience), followed by a list of "common notions" (very basic, self-evident assertions). Postulates It is possible to draw a straight line from any point to any other point. It is possible to extend a line segment continuously in both directions. It is possible to describe a circle with any center and any radius. It is true that all right angles are equal to one another. ("Parallel postulate") It is true that, if a straight line falling on two straight lines make the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, intersect on that side on which are the angles less than the two right angles. Common notions Things which are equal to the same thing are also equal to one another. If equals are added to equals, the wholes are equal. If equals are subtracted from equals, the remainders are equal. Things which coincide with one another are equal to one another. The whole is greater than the part. Modern development A lesson learned by mathematics in the last 150 years is that it is useful to strip the meaning away from the mathematical assertions (axioms, postulates, propositions, theorems) and definitions. One must concede the need for primitive notions, or undefined terms or concepts, in any study. Such abstraction or formalization makes mathematical knowledge more general, capable of multiple different meanings, and therefore useful in multiple contexts. Alessandro Padoa, Mario Pieri, and Giuseppe Peano were pioneers in this movement. Structuralist mathematics goes further, and develops theories and axioms (e.g. field theory, group theory, topology, vector spaces) without any particular application in mind. The distinction between an "axiom" and a "postulate" disappears. The postulates of Euclid are profitably motivated by saying that they lead to a great wealth of geometric facts. The truth of these complicated facts rests on the acceptance of the basic hypotheses. However, by throwing out Euclid's fifth postulate, one can get theories that have meaning in wider contexts (e.g., hyperbolic geometry). As such, one must simply be prepared to use labels such as "line" and "parallel" with greater flexibility. The development of hyperbolic geometry taught mathematicians that it is useful to regard postulates as purely formal statements, and not as facts based on experience. When mathematicians employ the field axioms, the intentions are even more abstract. The propositions of field theory do not concern any one particular application; the mathematician now works in complete abstraction. There are many examples of fields; field theory gives correct knowledge about them all. It is not correct to say that the axioms of field theory are "propositions that are regarded as true without proof." Rather, the field axioms are a set of constraints. If any given system of addition and multiplication satisfies these constraints, then one is in a position to instantly know a great deal of extra information about this system. Modern mathematics formalizes its foundations to such an extent that mathematical theories can be regarded as mathematical objects, and mathematics itself can be regarded as a branch of logic. Frege, Russell, Poincaré, Hilbert, and Gödel are some of the key figures in this development. Another lesson learned in modern mathematics is to examine purported proofs carefully for hidden assumptions. In the modern understanding, a set of axioms is any collection of formally stated assertions from which other formally stated assertions follow – by the application of certain well-defined rules. In this view, logic becomes just another formal system. A set of axioms should be consistent; it should be impossible to derive a contradiction from the axioms. A set of axioms should also be non-redundant; an assertion that can be deduced from other axioms need not be regarded as an axiom. It was the early hope of modern logicians that various branches of mathematics, perhaps all of mathematics, could be derived from a consistent collection of basic axioms. An early success of the formalist program was Hilbert's formalization of Euclidean geometry, and the related demonstration of the consistency of those axioms. In a wider context, there was an attempt to base all of mathematics on Cantor's set theory. Here, the emergence of Russell's paradox and similar antinomies of naïve set theory raised the possibility that any such system could turn out to be inconsistent. The formalist project suffered a decisive setback, when in 1931 Gödel showed that it is possible, for any sufficiently large set of axioms (Peano's axioms, for example) to construct a statement whose truth is independent of that set of axioms. As a corollary, Gödel proved that the consistency of a theory like Peano arithmetic is an unprovable assertion within the scope of that theory. It is reasonable to believe in the consistency of Peano arithmetic because it is satisfied by the system of natural numbers, an infinite but intuitively accessible formal system. However, at present, there is no known way of demonstrating the consistency of the modern Zermelo–Fraenkel axioms for set theory. Furthermore, using techniques of forcing (Cohen) one can show that the continuum hypothesis (Cantor) is independent of the Zermelo–Fraenkel axioms. Thus, even this very general set of axioms cannot be regarded as the definitive foundation for mathematics. Other sciences Experimental sciences - as opposed to mathematics and logic - also have general founding assertions from which a deductive reasoning can be built so as to express propositions that predict properties - either still general or much more specialized to a specific experimental context. For instance, Newton's laws in classical mechanics, Maxwell's equations in classical electromagnetism, Einstein's equation in general relativity, Mandel's laws of genetics, Darwin's Natural selection law, etc. These founding assertions are usually called principles or postulates so as to distinguish from mathematical axioms. As a matter of facts, the role of axioms in mathematics and postulates in experimental sciences is different. In mathematics one neither "proves" nor "disproves" an axiom. A set of mathematical axioms gives a set of rules that fix a conceptual realm, in which the theorems logically follow. In contrast, in experimental sciences, a set of postulates shall allow deducing results that match or do not match experimental results. If postulates do not allow deducing experimental predictions, they do not set a scientific conceptual framework and have to be completed or made more accurate. If the postulates allow deducing predictions of experimental results, the comparison with experiments allows falsifying (falsified) the theory that the postulates install. A theory is considered valid as long as it has not been falsified. Now, the transition between the mathematical axioms and scientific postulates is always slightly blurred, especially in physics. This is due to the heavy use of mathematical tools to support the physical theories. For instance, the introduction of Newton's laws rarely establishes as a prerequisite neither Euclidian geometry or differential calculus that they imply. It became more apparent when Albert Einstein first introduced special relativity where the invariant quantity is no more the Euclidian length (defined as ) > but the Minkowski spacetime interval (defined as ), and then general relativity where flat Minkowskian geometry is replaced with pseudo-Riemannian geometry on curved manifolds. In quantum physics, two sets of postulates have coexisted for some time, which provide a very nice example of falsification. The 'Copenhagen school' (Niels Bohr, Werner Heisenberg, Max Born) developed an operational approach with a complete mathematical formalism that involves the description of quantum system by vectors ('states') in a separable Hilbert space, and physical quantities as linear operators that act in this Hilbert space. This approach is fully falsifiable and has so far produced the most accurate predictions in physics. But it has the unsatisfactory aspect of not allowing answers to questions one would naturally ask. For this reason, another 'hidden variables' approach was developed for some time by Albert Einstein, Erwin Schrödinger, David Bohm. It was created so as to try to give deterministic explanation to phenomena such as entanglement. This approach assumed that the Copenhagen school description was not complete, and postulated that some yet unknown variable was to be added to the theory so as to allow answering some of the questions it does not answer (the founding elements of which were discussed as the EPR paradox in 1935). Taking this ideas seriously, John Bell derived in 1964 a prediction that would lead to different experimental results (Bell's inequalities) in the Copenhagen and the Hidden variable case. The experiment was conducted first by Alain Aspect in the early 1980's, and the result excluded the simple hidden variable approach (sophisticated hidden variables could still exist but their properties would still be more disturbing than the problems they try to solve). This does not mean that the conceptual framework of quantum physics can be considered as complete now, since some open questions still exist (the limit between the quantum and classical realms, what happens during a quantum measurement, what happens in a completely closed quantum system such as the universe itself, etc). Mathematical logic In the field of mathematical logic, a clear distinction is made between two notions of axioms: logical and non-logical (somewhat similar to the ancient distinction between "axioms" and "postulates" respectively). Logical axioms These are certain formulas in a formal language that are universally valid, that is, formulas that are satisfied by every assignment of values. Usually one takes as logical axioms at least some minimal set of tautologies that is sufficient for proving all tautologies in the language; in the case of predicate logic more logical axioms than that are required, in order to prove logical truths that are not tautologies in the strict sense. Examples Propositional logic In propositional logic it is common to take as logical axioms all formulae of the following forms, where , , and can be any formulae of the language and where the included primitive connectives are only "" for negation of the immediately following proposition and "" for implication from antecedent to consequent propositions: Each of these patterns is an axiom schema, a rule for generating an infinite number of axioms. For example, if , , and are propositional variables, then and are both instances of axiom schema 1, and hence are axioms. It can be shown that with only these three axiom schemata and modus ponens, one can prove all tautologies of the propositional calculus. It can also be shown that no pair of these schemata is sufficient for proving all tautologies with modus ponens. Other axiom schemata involving the same or different sets of primitive connectives can be alternatively constructed. These axiom schemata are also used in the predicate calculus, but additional logical axioms are needed to include a quantifier in the calculus. First-order logic Axiom of Equality. Let be a first-order language. For each variable , the formula is universally valid. This means that, for any variable symbol the formula can be regarded as an axiom. Also, in this example, for this not to fall into vagueness and a never-ending series of "primitive notions", either a precise notion of what we mean by (or, for that matter, "to be equal") has to be well established first, or a purely formal and syntactical usage of the symbol has to be enforced, only regarding it as a string and only a string of symbols, and mathematical logic does indeed do that. Another, more interesting example axiom scheme, is that which provides us with what is known as Universal Instantiation: Axiom scheme for Universal Instantiation. Given a formula in a first-order language , a variable and a term that is substitutable for in , the formula is universally valid. Where the symbol stands for the formula with the term substituted for . (See Substitution of variables.) In informal terms, this example allows us to state that, if we know that a certain property holds for every and that stands for a particular object in our structure, then we should be able to claim . Again, we are claiming that the formula is valid, that is, we must be able to give a "proof" of this fact, or more properly speaking, a metaproof. These examples are metatheorems of our theory of mathematical logic since we are dealing with the very concept of proof itself. Aside from this, we can also have Existential Generalization: Axiom scheme for Existential Generalization. Given a formula in a first-order language , a variable and a term that is substitutable for in , the formula is universally valid. Non-logical axioms Non-logical axioms are formulas that play the role of theory-specific assumptions. Reasoning about two different structures, for example, the natural numbers and the integers, may involve the same logical axioms; the non-logical axioms aim to capture what is special about a particular structure (or set of structures, such as groups). Thus non-logical axioms, unlike logical axioms, are not tautologies. Another name for a non-logical axiom is postulate. Almost every modern mathematical theory starts from a given set of non-logical axioms, and it was thought that in principle every theory could be axiomatized in this way and formalized down to the bare language of logical formulas. Non-logical axioms are often simply referred to as axioms in mathematical discourse. This does not mean that it is claimed that they are true in some absolute sense. For example, in some groups, the group operation is commutative, and this can be asserted with the introduction of an additional axiom, but without this axiom, we can do quite well developing (the more general) group theory, and we can even take its negation as an axiom for the study of non-commutative groups. Thus, an axiom is an elementary basis for a formal logic system that together with the rules of inference define a deductive system. Examples This section gives examples of mathematical theories that are developed entirely from a set of non-logical axioms (axioms, henceforth). A rigorous treatment of any of these topics begins with a specification of these axioms. Basic theories, such as arithmetic, real analysis and complex analysis are often introduced non-axiomatically, but implicitly or explicitly there is generally an assumption that the axioms being used are the axioms of Zermelo–Fraenkel set theory with choice, abbreviated ZFC, or some very similar system of axiomatic set theory like Von Neumann–Bernays–Gödel set theory, a conservative extension of ZFC. Sometimes slightly stronger theories such as Morse–Kelley set theory or set theory with a strongly inaccessible cardinal allowing the use of a Grothendieck universe is used, but in fact, most mathematicians can actually prove all they need in systems weaker than ZFC, such as second-order arithmetic. The study of topology in mathematics extends all over through point set topology, algebraic topology, differential topology, and all the related paraphernalia, such as homology theory, homotopy theory. The development of abstract algebra brought with itself group theory, rings, fields, and Galois theory. This list could be expanded to include most fields of mathematics, including measure theory, ergodic theory, probability, representation theory, and differential geometry. Arithmetic The Peano axioms are the most widely used axiomatization of first-order arithmetic. They are a set of axioms strong enough to prove many important facts about number theory and they allowed Gödel to establish his famous second incompleteness theorem. We have a language where is a constant symbol and is a unary function and the following axioms: for any formula with one free variable. The standard structure is where is the set of natural numbers, is the successor function and is naturally interpreted as the number 0. Euclidean geometry Probably the oldest, and most famous, list of axioms are the 4 + 1 Euclid's postulates of plane geometry. The axioms are referred to as "4 + 1" because for nearly two millennia the fifth (parallel) postulate ("through a point outside a line there is exactly one parallel") was suspected of being derivable from the first four. Ultimately, the fifth postulate was found to be independent of the first four. One can assume that exactly one parallel through a point outside a line exists, or that infinitely many exist. This choice gives us two alternative forms of geometry in which the interior angles of a triangle add up to exactly 180 degrees or less, respectively, and are known as Euclidean and hyperbolic geometries. If one also removes the second postulate ("a line can be extended indefinitely") then elliptic geometry arises, where there is no parallel through a point outside a line, and in which the interior angles of a triangle add up to more than 180 degrees. Real analysis The objectives of the study are within the domain of real numbers. The real numbers are uniquely picked out (up to isomorphism) by the properties of a Dedekind complete ordered field, meaning that any nonempty set of real numbers with an upper bound has a least upper bound. However, expressing these properties as axioms requires the use of second-order logic. The Löwenheim–Skolem theorems tell us that if we restrict ourselves to first-order logic, any axiom system for the reals admits other models, including both models that are smaller than the reals and models that are larger. Some of the latter are studied in non-standard analysis. Role in mathematical logic Deductive systems and completeness A deductive system consists of a set of logical axioms, a set of non-logical axioms, and a set of rules of inference. A desirable property of a deductive system is that it be complete. A system is said to be complete if, for all formulas , that is, for any statement that is a logical consequence of there actually exists a deduction of the statement from . This is sometimes expressed as "everything that is true is provable", but it must be understood that "true" here means "made true by the set of axioms", and not, for example, "true in the intended interpretation". Gödel's completeness theorem establishes the completeness of a certain commonly used type of deductive system. Note that "completeness" has a different meaning here than it does in the context of Gödel's first incompleteness theorem, which states that no recursive, consistent set of non-logical axioms of the Theory of Arithmetic is complete, in the sense that there will always exist an arithmetic statement such that neither nor can be proved from the given set of axioms. There is thus, on the one hand, the notion of completeness of a deductive system and on the other hand that of completeness of a set of non-logical axioms. The completeness theorem and the incompleteness theorem, despite their names, do not contradict one another. Further discussion Early mathematicians regarded axiomatic geometry as a model of physical space, and obviously, there could only be one such model. The idea that alternative mathematical systems might exist was very troubling to mathematicians of the 19th century and the developers of systems such as Boolean algebra made elaborate efforts to derive them from traditional arithmetic. Galois showed just before his untimely death that these efforts were largely wasted. Ultimately, the abstract parallels between algebraic systems were seen to be more important than the details, and modern algebra was born. In the modern view, axioms may be any set of formulas, as long as they are not known to be inconsistent. See also Axiomatic system Dogma First principle, axiom in science and philosophy List of axioms Model theory Regulæ Juris Theorem Presupposition Physical law Principle Notes References Further reading Mendelson, Elliot (1987). Introduction to mathematical logic. Belmont, California: Wadsworth & Brooks. External links Metamath axioms page Ancient Greek philosophy Concepts in ancient Greek metaphysics Concepts in epistemology Concepts in ethics Concepts in logic Concepts in metaphysics Concepts in the philosophy of science Deductive reasoning Formal systems History of logic History of mathematics History of philosophy History of science Intellectual history Logic Mathematical logic Mathematical terminology Philosophical terminology Reasoning

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

929

https://en.wikipedia.org/wiki/Alpha

Alpha

Alpha (uppercase , lowercase ; , álpha, or ) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , which is the West Semitic word for "ox". Letters that arose from alpha include the Latin letter A and the Cyrillic letter А. Uses Greek In Ancient Greek, alpha was pronounced and could be either phonemically long ([aː]) or short ([a]). Where there is ambiguity, long and short alpha are sometimes written with a macron and breve today: Ᾱᾱ, Ᾰᾰ. ὥρα = ὥρᾱ hōrā "a time" γλῶσσα = γλῶσσᾰ glôssa "tongue" In Modern Greek, vowel length has been lost, and all instances of alpha simply represent . In the polytonic orthography of Greek, alpha, like other vowel letters, can occur with several diacritic marks: any of three accent symbols (), and either of two breathing marks (), as well as combinations of these. It can also combine with the iota subscript (). Greek grammar In the Attic–Ionic dialect of Ancient Greek, long alpha fronted to (eta). In Ionic, the shift took place in all positions. In Attic, the shift did not take place after epsilon, iota, and rho (ε, ι, ρ; e, i, r). In Doric and Aeolic, long alpha is preserved in all positions. Doric, Aeolic, Attic chṓrā – Ionic chṓrē, "country" Doric, Aeolic phā́mā – Attic, Ionic phḗmē, "report" Privative a is the Ancient Greek prefix ἀ- or ἀν- a-, an-, added to words to negate them. It originates from the Proto-Indo-European * (syllabic nasal) and is cognate with English un-. Copulative a is the Greek prefix ἁ- or ἀ- ha-, a-. It comes from Proto-Indo-European *. Mathematics and science The letter alpha represents various concepts in physics and chemistry, including alpha radiation, angular acceleration, alpha particles, alpha carbon and strength of electromagnetic interaction (as Fine-structure constant). Alpha also stands for thermal expansion coefficient of a compound in physical chemistry. It is also commonly used in mathematics in algebraic solutions representing quantities such as angles. Furthermore, in mathematics, the letter alpha is used to denote the area underneath a normal curve in statistics to denote significance level when proving null and alternative hypotheses. In ethology, it is used to name the dominant individual in a group of animals. In aerodynamics, the letter is used as a symbol for the angle of attack of an aircraft and the word "alpha" is used as a synonym for this property. In mathematical logic, α is sometimes used as a placeholder for ordinal numbers. The proportionality operator "∝" (in Unicode: U+221D) is sometimes mistaken for alpha. The uppercase letter alpha is not generally used as a symbol because it tends to be rendered identically to the uppercase Latin A. International Phonetic Alphabet In the International Phonetic Alphabet, the letter ɑ, which looks similar to the lower-case alpha, represents the open back unrounded vowel. History and symbolism Origin The Phoenician alphabet was adopted for Greek in the early 8th century BC, perhaps in Euboea. The majority of the letters of the Phoenician alphabet were adopted into Greek with much the same sounds as they had had in Phoenician, but ʼāleph, the Phoenician letter representing the glottal stop , was adopted as representing the vowel ; similarly, hē and ʽayin are Phoenician consonants that became Greek vowels, epsilon and omicron , respectively. Plutarch Plutarch, in Moralia, presents a discussion on why the letter alpha stands first in the alphabet. Ammonius asks Plutarch what he, being a Boeotian, has to say for Cadmus, the Phoenician who reputedly settled in Thebes and introduced the alphabet to Greece, placing alpha first because it is the Phoenician name for ox—which, unlike Hesiod, the Phoenicians considered not the second or third, but the first of all necessities. "Nothing at all," Plutarch replied. He then added that he would rather be assisted by Lamprias, his own grandfather, than by Dionysus' grandfather, i.e. Cadmus. For Lamprias had said that the first articulate sound made is "alpha", because it is very plain and simple—the air coming off the mouth does not require any motion of the tongue—and therefore this is the first sound that children make. According to Plutarch's natural order of attribution of the vowels to the planets, alpha was connected with the Moon. Alpha and Omega As the first letter of the alphabet, Alpha as a Greek numeral came to represent the number 1. Therefore, Alpha, both as a symbol and term, is used to refer to the "first", or "primary", or "principal" (most significant) occurrence or status of a thing. The New Testament has God declaring himself to be the "Alpha and Omega, the beginning and the end, the first and the last." (Revelation 22:13, KJV, and see also 1:8). Consequently, the term "alpha" has also come to be used to denote "primary" position in social hierarchy, examples being "alpha males" or pack leaders. Computer encodings Greek alpha / Coptic alfa For accented Greek characters, see Greek diacritics: Computer encoding. Latin / IPA alpha Mathematical / Technical alpha References Greek letters Vowel letters

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

930

https://en.wikipedia.org/wiki/Alvin%20Toffler

Alvin Toffler

Alvin Toffler (October 4, 1928 – June 27, 2016) was an American writer, futurist, and businessman known for his works discussing modern technologies, including the digital revolution and the communication revolution, with emphasis on their effects on cultures worldwide. He is regarded as one of the world's outstanding futurists. Toffler was an associate editor of Fortune magazine. In his early works he focused on technology and its impact, which he termed "information overload." In 1970, his first major book about the future, Future Shock, became a worldwide best-seller and has sold over 6 million copies. He and his wife Heidi Toffler, who collaborated with him for most of his writings, moved on to examining the reaction to changes in society with another best-selling book, The Third Wave in 1980. In it, he foresaw such technological advances as cloning, personal computers, the Internet, cable television and mobile communication. His later focus, via their other best-seller, Powershift, (1990), was on the increasing power of 21st-century military hardware and the proliferation of new technologies. He founded Toffler Associates, a management consulting company, and was a visiting scholar at the Russell Sage Foundation, visiting professor at Cornell University, faculty member of the New School for Social Research, a White House correspondent, and a business consultant. Toffler's ideas and writings were a significant influence on the thinking of business and government leaders worldwide, including China's Zhao Ziyang, and AOL founder Steve Case. Early life Alvin Toffler was born on October 4, 1928, in New York City, and raised in Brooklyn. He was the son of Rose (Albaum) and Sam Toffler, a furrier, both Jewish immigrants from Poland. He had one younger sister. He was inspired to become a writer at the age of 7 by his aunt and uncle, who lived with the Tofflers. "They were Depression-era literary intellectuals," Toffler said, "and they always talked about exciting ideas." Toffler graduated from New York University in 1950 as an English major, though by his own account he was more focused on political activism than grades. He met his future wife, Adelaide Elizabeth Farrell (nicknamed "Heidi"), when she was starting a graduate course in linguistics. Being radical students, they decided against further graduate work and moved to the Midwest, where they married on April 29, 1950. Career Seeking experiences to write about, Alvin and Heidi Toffler spent the next five years as blue collar workers on assembly lines while studying industrial mass production in their daily work. He compared his own desire for experience to other writers, such as Jack London, who in his quest for subjects to write about sailed the seas, and John Steinbeck, who went to pick grapes with migrant workers. In their first factory jobs, Heidi became a union shop steward in the aluminum foundry where she worked. Alvin became a millwright and welder. In the evenings Alvin would write poetry and fiction, but discovered he was proficient at neither. His hands-on practical labor experience helped Alvin Toffler land a position at a union-backed newspaper, a transfer to its Washington bureau in 1957, then three years as a White House correspondent, covering Congress and the White House for a Pennsylvania daily newspaper. They returned to New York City in 1959 when Fortune magazine invited Alvin to become its labor columnist, later having him write about business and management. After leaving Fortune magazine in 1962, Toffler began a freelance career, writing long form articles for scholarly journals and magazines. His 1964 Playboy interviews with Russian novelist Vladimir Nabokov and Ayn Rand were considered among the magazine's best. His interview with Rand was the first time the magazine had given such a platform to a female intellectual, which as one commentator said, "the real bird of paradise Toffler captured for Playboy in 1964 was Ayn Rand." Toffler was hired by IBM to conduct research and write a paper on the social and organizational impact of computers, leading to his contact with the earliest computer "gurus" and artificial intelligence researchers and proponents. Xerox invited him to write about its research laboratory and AT&T consulted him for strategic advice. This AT&T work led to a study of telecommunications, which advised the company's top management to break up the company more than a decade before the government forced AT&T to break up. In the mid-1960s, the Tofflers began five years of research on what would become Future Shock, published in 1970. It has sold over 6 million copies worldwide, according to the New York Times, or over 15 million copies according to the Tofflers' Web site. Toffler coined the term "future shock" to refer to what happens to a society when change happens too fast, which results in social confusion and normal decision-making processes breaking down. The book has never been out of print and has been translated into dozens of languages. He continued the theme in The Third Wave in 1980. While he describes the first and second waves as the agricultural and industrial revolutions, the "third wave," a phrase he coined, represents the current information, computer-based revolution. He forecast the spread of the Internet and email, interactive media, cable television, cloning, and other digital advancements. He claimed that one of the side effects of the digital age has been "information overload," another term he coined. In 1990, he wrote Powershift, also with the help of his wife, Heidi. In 1996, with American business consultant Tom Johnson, they co-founded Toffler Associates, an advisory firm designed to implement many of the ideas the Tofflers had written on. The firm worked with businesses, NGOs, and governments in the United States, South Korea, Mexico, Brazil, Singapore, Australia, and other countries. During this period in his career, Toffler lectured worldwide, taught at several schools and met world leaders, such as Mikhail Gorbachev, along with key executives and military officials. Ideas and opinions Toffler stated many of his ideas during an interview with the Australian Broadcasting Corporation in 1998. "Society needs people who take care of the elderly and who know how to be compassionate and honest," he said. "Society needs people who work in hospitals. Society needs all kinds of skills that are not just cognitive; they're emotional, they're affectional. You can't run the society on data and computers alone." His opinions about the future of education, many of which were in Future Shock, have often been quoted. An often misattributed quote, however, is that of psychologist Herbert Gerjuoy: "Tomorrow's illiterate will not be the man who can't read; he will be the man who has not learned how to learn." Early in his career, after traveling to other countries, he became aware of the new and myriad inputs that visitors received from these other cultures. He explained during an interview that some visitors would become "truly disoriented and upset" by the strange environment, which he described as a reaction to culture shock. From that issue, he foresaw another problem for the future, when a culturally "new environment comes to you ... and comes to you rapidly." That kind of sudden cultural change within one's own country, which he felt many would not understand, would lead to a similar reaction, one of "future shock", which he wrote about in his book by that title. Toffler writes: In The Third Wave, Toffler describes three types of societies, based on the concept of "waves"—each wave pushes the older societies and cultures aside. He describes the "First Wave" as the society after agrarian revolution and replaced the first hunter-gatherer cultures. The "Second Wave," he labels society during the Industrial Revolution (ca. late 17th century through the mid-20th century). That period saw the increase of urban industrial populations which had undermined the traditional nuclear family, and initiated a factory-like education system, and the growth of the corporation. Toffler said: The "Third Wave" was a term he coined to describe the post-industrial society, which began in the late 1950s. His description of this period dovetails with other futurist writers, who also wrote about the Information Age, Space Age, Electronic Era, Global Village, terms which highlighted a scientific-technological revolution. The Tofflers claimed to have predicted a number of geopolitical events, such as the collapse of the Soviet Union, the fall of the Berlin Wall and the future economic growth in the Asia-Pacific region. Influences and popular culture Toffler often visited with dignitaries in Asia, including China's Zhao Ziyang, Singapore's Lee Kuan Yew and South Korea's Kim Dae Jung, all of whom were influenced by his views as Asia's emerging markets increased in global significance during the 1980s and 1990s. Although they had originally censored some of his books and ideas, China's government cited him along with Franklin Roosevelt and Bill Gates as being among the Westerners who had most influenced their country. The Third Wave along with a video documentary based on it became best-sellers in China and were widely distributed to schools. The video's success inspired the marketing of videos on related themes in the late 1990s by Infowars, whose name is derived from the term coined by Toffler in the book. Toffler's influence on Asian thinkers was summed up in an article in Daedalus, published by the American Academy of Arts & Sciences: U.S. House Speaker Newt Gingrich publicly lauded his ideas about the future, and urged members of Congress to read Toffler's book, Creating a New Civilization (1995). Others, such as AOL founder Steve Case, cited Toffler's The Third Wave as a formative influence on his thinking, which inspired him to write The Third Wave: An Entrepreneur's Vision of the Future in 2016. Case said that Toffler was a "real pioneer in helping people, companies and even countries lean into the future." In 1980, Ted Turner founded CNN, which he said was inspired by Toffler's forecasting the end of the dominance of the three main television networks. Turner's company, Turner Broadcasting, published Toffler's Creating a New Civilization in 1995. Shortly after the book was released, the former Soviet president Mikhail Gorbachev hosted the Global Governance Conference in San Francisco with the theme, Toward a New Civilization, which was attended by dozens of world figures, including the Tofflers, George H. W. Bush, Margaret Thatcher, Carl Sagan, Abba Eban and Turner with his then-wife, actress Jane Fonda. Mexican billionaire Carlos Slim was influenced by his works, and became a friend of the writer. Global marketer J.D. Power also said he was inspired by Toffler's works. Since the 1960s, people had tried to make sense out of the effect of new technologies and social change, a problem which made Toffler's writings widely influential beyond the confines of scientific, economic, and public policy. His works and ideas have been subject to various criticisms, usually with the same argumentation used against futurology: that foreseeing the future is nigh impossible. Techno music pioneer Juan Atkins cites Toffler's phrase "techno rebels" in The Third Wave as inspiring him to use the word "techno" to describe the musical style he helped to create Musician Curtis Mayfield released a disco song called "Future Shock," later covered in an electro version by Herbie Hancock. Science fiction author John Brunner wrote "The Shockwave Rider," from the concept of "future shock." The nightclub Toffler, in Rotterdam, is named after him. In the song "Victoria" by The Exponents, the protagonist's daily routine and cultural interests are described: "She's up in time to watch the soap operas, reads Cosmopolitan and Alvin Toffler". Critical assessment Accenture, the management consultancy firm, identified Toffler in 2002 as being among the most influential voices in business leaders, along with Bill Gates and Peter Drucker. Toffler has also been described in a Financial Times interview as the "world's most famous futurologist". In 2006, the People's Daily classed him among the 50 foreigners who shaped modern China, which one U.S. newspaper notes made him a "guru of sorts to world statesmen." Chinese Premier and General Secretary Zhao Ziyang was greatly influenced by Toffler. He convened conferences to discuss The Third Wave in the early 1980s, and in 1985 the book was the No. 2 best seller in China. Author Mark Satin characterizes Toffler as an important early influence on radical centrist political thought. Newt Gingrich became close to the Tofflers in the 1970s and said The Third Wave had immensely influenced his own thinking and was "one of the great seminal works of our time." Selected awards Toffler has received several prestigious prizes and awards, including the McKinsey Foundation Book Award for Contributions to Management Literature, Officier de L'Ordre des Arts et Lettres, and appointments, including Fellow of the American Association for the Advancement of Science and the International Institute for Strategic Studies. In 2006, Alvin and Heidi Toffler were recipients of Brown University's Independent Award. Personal life Toffler was married to Heidi Toffler, also a writer and futurist. They lived in the Bel Air section of Los Angeles, California, and previously lived in Redding, Connecticut. The couple's only child, Karen Toffler (1954–2000), died at age 46 after more than a decade suffering from Guillain–Barré syndrome. Alvin Toffler died in his sleep on June 27, 2016, at his home in Los Angeles. No cause of death was given. He is buried at Westwood Memorial Park. Bibliography Alvin Toffler co-wrote his books with his wife Heidi. The Culture Consumers (1964) St. Martin's Press, The Schoolhouse in the City (1968) Praeger (editors), Future Shock (1970) Bantam Books, The Futurists (1972) Random House (editors), Learning for Tomorrow (1974) Random House (editors), The Eco-Spasm Report (1975) Bantam Books, The Third Wave (1980) Bantam Books, Previews & Premises (1983) William Morrow & Co, The Adaptive Corporation (1985) McGraw-Hill, Powershift: Knowledge, Wealth and Violence at the Edge of the 21st Century (1990) Bantam Books, War and Anti-War (1993) Warner Books, Creating a New Civilization (1995) Turner Pub, Revolutionary Wealth (2006) Knopf, See also Daniel Bell Norman Swan Human nature John Naisbitt References External links  – official Alvin Toffler site Toffler Associates Interview with Alvin Toffler by the World Affairs Council Discuss Alvin Toffler's Future Shock with other readers, BookTalk.org Alvin Toffler at Find a Grave Future Shock Forum 2018 Finding aid to the Alvin and Heidi Toffler papers at Columbia University. Rare Book & Manuscript Library 1928 births 2016 deaths American people of Polish-Jewish descent American technology writers American futurologists Burials at Westwood Village Memorial Park Cemetery Jewish American writers People from Ridgefield, Connecticut Writers from Connecticut Writers from Brooklyn 20th-century American non-fiction writers 21st-century American non-fiction writers American transhumanists New York University alumni Singularitarians People from Redding, Connecticut 20th-century American male writers American male non-fiction writers Jewish American journalists People from Bel Air, Los Angeles 21st-century American male writers 21st-century American Jews

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

933

https://en.wikipedia.org/wiki/AM

AM

AM may refer to: Arts and entertainment Music Skengdo & AM, British rap duo AM (musician), American musician A.M. (musician), Canadian musician DJ AM, American DJ and producer AM (Abraham Mateo album) A.M. (Wilco album) A.M. (Chris Young album) AM (Arctic Monkeys album) Am, the A minor chord symbol A minor, a minor scale in music Armeemarschsammlung, Prussian Army March Collection (Preußische Armeemarschsammlung) Television and radio AM (ABC Radio), Australian radio programme American Morning, American television program Am, Antes del Mediodia, Argentine television program Other media Allied Mastercomputer, the antagonist of the short story "I Have No Mouth, and I Must Scream" Education Master of Arts, an academic degree Arts et Métiers ParisTech, a French engineering school Active Minds, a mental health awareness charity Science Americium, a chemical element Attometre, a unit of length Adrenomedullin, a protein Air mass (astronomy) attomolar (aM), a unit of molar concentration Am, tropical monsoon climate in the Köppen climate classification AM, a complexity class related to Arthur–Merlin protocol Technology .am, Internet domain for Armenia .am, a file extension associated with Automake software Agile modeling, a software engineering methodology for modeling and documenting software systems Amplitude modulation, an electronic communication technique Additive Manufacturing, a process of making a three-dimensional solid object of virtually any shape from a digital model. AM broadcasting, radio broadcasting using amplitude modulation Anti-materiel rifle Automated Mathematician, an artificial intelligence program Timekeeping ante meridiem, Latin for "before midday" Anno Mundi, a calendar era based on the biblical creation of the world Anno Martyrum, a method of numbering years in the Coptic calendar Transportation A.M. (automobile), a 1906 French car Aeroméxico (IATA airline code AM) Arkansas and Missouri Railroad All-mountain, a discipline of mountain biking Military AM, the United States Navy hull classification symbol for "minesweeper" Air marshal, a senior air officer rank used in Commonwealth countries Anti-materiel rifle Aviation Structural Mechanic, a U.S. Navy occupational rating Other uses Am (cuneiform), a written syllable Member of the Order of Australia, postnominal letters which can be used by a Member of the Order Assembly Member (disambiguation), a political office Member of the National Assembly for Wales Member of the London Assembly Amharic language (ISO 639-1 language code am) Armenia (ISO country code AM) Attacking midfielder, a position in association football First person singular present of the copula verb to be. See also Pro–am `am (disambiguation) A&M (disambiguation) AM2 (disambiguation) AMS (disambiguation)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

974

https://en.wikipedia.org/wiki/Ada%20Lovelace

Ada Lovelace

Augusta Ada King, Countess of Lovelace (née Byron; 10 December 1815 – 27 November 1852) was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the Analytical Engine. She was the first to recognise that the machine had applications beyond pure calculation, and to have published the first algorithm intended to be carried out by such a machine. As a result, she is often regarded as the first computer programmer. Ada Byron was the only child of poet Lord Byron and mathematician Lady Byron. All of Byron's other children were born out of wedlock to other women. Byron separated from his wife a month after Ada was born and left England forever. Four months later, he commemorated the parting in a poem that begins, "Is thy face like thy mother's my fair child! ADA! sole daughter of my house and heart?". He died in Greece when Ada was eight years old. Her mother remained bitter and promoted Ada's interest in mathematics and logic in an effort to prevent her from developing her father's perceived insanity. Despite this, Ada remained interested in him, naming her two sons Byron and Gordon. Upon her death, she was buried next to him at her request. Although often ill in her childhood, Ada pursued her studies assiduously. She married William King in 1835. King was made Earl of Lovelace in 1838, Ada thereby becoming Countess of Lovelace. Her educational and social exploits brought her into contact with scientists such as Andrew Crosse, Charles Babbage, Sir David Brewster, Charles Wheatstone, Michael Faraday and the author Charles Dickens, contacts which she used to further her education. Ada described her approach as "poetical science" and herself as an "Analyst (& Metaphysician)". When she was a teenager (18), her mathematical talents led her to a long working relationship and friendship with fellow British mathematician Charles Babbage, who is known as "the father of computers". She was in particular interested in Babbage's work on the Analytical Engine. Lovelace first met him in June 1833, through their mutual friend, and her private tutor, Mary Somerville. Between 1842 and 1843, Ada translated an article by Italian military engineer Luigi Menabrea about the Analytical Engine, supplementing it with an elaborate set of notes, simply called "Notes". Lovelace's notes are important in the early history of computers, containing what many consider to be the first computer program—that is, an algorithm designed to be carried out by a machine. Other historians reject this perspective and point out that Babbage's personal notes from the years 1836/1837 contain the first programs for the engine. She also developed a vision of the capability of computers to go beyond mere calculating or number-crunching, while many others, including Babbage himself, focused only on those capabilities. Her mindset of "poetical science" led her to ask questions about the Analytical Engine (as shown in her notes) examining how individuals and society relate to technology as a collaborative tool. She died of uterine cancer in 1852 at the age of 36, the same age at which her father died. Biography Childhood Lord Byron expected his child to be a "glorious boy" and was disappointed when Lady Byron gave birth to a girl. The child was named after Byron's half-sister, Augusta Leigh, and was called "Ada" by Byron himself. On 16 January 1816, at Lord Byron's command, Lady Byron left for her parents' home at Kirkby Mallory, taking their five-week-old daughter with her. Although English law at the time granted full custody of children to the father in cases of separation, Lord Byron made no attempt to claim his parental rights, but did request that his sister keep him informed of Ada's welfare. On 21 April, Lord Byron signed the deed of separation, although very reluctantly, and left England for good a few days later. Aside from an acrimonious separation, Lady Byron continued throughout her life to make allegations about her husband's immoral behaviour. This set of events made Lovelace infamous in Victorian society. Ada did not have a relationship with her father. He died in 1824 when she was eight years old. Her mother was the only significant parental figure in her life. Lovelace was not shown the family portrait of her father until her 20th birthday. Lovelace did not have a close relationship with her mother. She was often left in the care of her maternal grandmother Judith, Hon. Lady Milbanke, who doted on her. However, because of societal attitudes of the time—which favoured the husband in any separation, with the welfare of any child acting as mitigation—Lady Byron had to present herself as a loving mother to the rest of society. This included writing anxious letters to Lady Milbanke about her daughter's welfare, with a cover note saying to retain the letters in case she had to use them to show maternal concern. In one letter to Lady Milbanke, she referred to her daughter as "it": "I talk to it for your satisfaction, not my own, and shall be very glad when you have it under your own." Lady Byron had her teenage daughter watched by close friends for any sign of moral deviation. Lovelace dubbed these observers the "Furies" and later complained they exaggerated and invented stories about her. Lovelace was often ill, beginning in early childhood. At the age of eight, she experienced headaches that obscured her vision. In June 1829, she was paralyzed after a bout of measles. She was subjected to continuous bed rest for nearly a year, something which may have extended her period of disability. By 1831, she was able to walk with crutches. Despite the illnesses, she developed her mathematical and technological skills. Ada Byron had an affair with a tutor in early 1833. She tried to elope with him after she was caught, but the tutor's relatives recognised her and contacted her mother. Lady Byron and her friends covered the incident up to prevent a public scandal. Lovelace never met her younger half-sister, Allegra, the daughter of Lord Byron and Claire Clairmont. Allegra died in 1822 at the age of five. Lovelace did have some contact with Elizabeth Medora Leigh, the daughter of Byron's half-sister Augusta Leigh, who purposely avoided Lovelace as much as possible when introduced at court. Adult years Lovelace became close friends with her tutor Mary Somerville, who introduced her to Charles Babbage in 1833. She had a strong respect and affection for Somerville, and they corresponded for many years. Other acquaintances included the scientists Andrew Crosse, Sir David Brewster, Charles Wheatstone, Michael Faraday and the author Charles Dickens. She was presented at Court at the age of seventeen "and became a popular belle of the season" in part because of her "brilliant mind." By 1834 Ada was a regular at Court and started attending various events. She danced often and was able to charm many people, and was described by most people as being dainty, although John Hobhouse, Byron's friend, described her as "a large, coarse-skinned young woman but with something of my friend's features, particularly the mouth". This description followed their meeting on 24 February 1834 in which Ada made it clear to Hobhouse that she did not like him, probably due to her mother's influence, which led her to dislike all of her father's friends. This first impression was not to last, and they later became friends. On 8 July 1835, she married William, 8th Baron King, becoming Lady King. They had three homes: Ockham Park, Surrey; a Scottish estate on Loch Torridon in Ross-shire; and a house in London. They spent their honeymoon at Worthy Manor in Ashley Combe near Porlock Weir, Somerset. The Manor had been built as a hunting lodge in 1799 and was improved by King in preparation for their honeymoon. It later became their summer retreat and was further improved during this time. From 1845, the family's main house was Horsley Towers, built in the Tudorbethan fashion by the architect of the Houses of Parliament, Charles Barry, and later greatly enlarged to Lovelace's own designs. They had three children: Byron (born 1836); Anne Isabella (called Annabella, born 1837); and Ralph Gordon (born 1839). Immediately after the birth of Annabella, Lady King experienced "a tedious and suffering illness, which took months to cure." Ada was a descendant of the extinct Barons Lovelace and in 1838, her husband was made Earl of Lovelace and Viscount Ockham, meaning Ada became the Countess of Lovelace. In 1843–44, Ada's mother assigned William Benjamin Carpenter to teach Ada's children and to act as a "moral" instructor for Ada. He quickly fell for her and encouraged her to express any frustrated affections, claiming that his marriage meant he would never act in an "unbecoming" manner. When it became clear that Carpenter was trying to start an affair, Ada cut it off. In 1841, Lovelace and Medora Leigh (the daughter of Lord Byron's half-sister Augusta Leigh) were told by Ada's mother that Ada's father was also Medora's father. On 27 February 1841, Ada wrote to her mother: "I am not in the least astonished. In fact, you merely confirm what I have for years and years felt scarcely a doubt about, but should have considered it most improper in me to hint to you that I in any way suspected." She did not blame the incestuous relationship on Byron, but instead blamed Augusta Leigh: "I fear she is more inherently wicked than he ever was." In the 1840s, Ada flirted with scandals: firstly, from a relaxed approach to extra-marital relationships with men, leading to rumours of affairs; and secondly, from her love of gambling. She apparently lost more than £3,000 on the horses during the later 1840s. The gambling led to her forming a syndicate with male friends, and an ambitious attempt in 1851 to create a mathematical model for successful large bets. This went disastrously wrong, leaving her thousands of pounds in debt to the syndicate, forcing her to admit it all to her husband. She had a shadowy relationship with Andrew Crosse's son John from 1844 onwards. John Crosse destroyed most of their correspondence after her death as part of a legal agreement. She bequeathed him the only heirlooms her father had personally left to her. During her final illness, she would panic at the idea of the younger Crosse being kept from visiting her. Education From 1832, when she was seventeen, her mathematical abilities began to emerge, and her interest in mathematics dominated the majority of her adult life. Her mother's obsession with rooting out any of the insanity of which she accused Byron was one of the reasons that Ada was taught mathematics from an early age. She was privately educated in mathematics and science by William Frend, William King, and Mary Somerville, the noted 19th-century researcher and scientific author. In the 1840s, the mathematician Augustus De Morgan extended her "much help in her mathematical studies" including study of advanced calculus topics including the "numbers of Bernoulli" (that formed her celebrated algorithm for Babbage's Analytical Engine). In a letter to Lady Byron, De Morgan suggested that Ada's skill in mathematics might lead her to become "an original mathematical investigator, perhaps of first-rate eminence." Lovelace often questioned basic assumptions through integrating poetry and science. Whilst studying differential calculus, she wrote to De Morgan: I may remark that the curious transformations many formulae can undergo, the unsuspected and to a beginner apparently impossible identity of forms exceedingly dissimilar at first sight, is I think one of the chief difficulties in the early part of mathematical studies. I am often reminded of certain sprites and fairies one reads of, who are at one's elbows in one shape now, and the next minute in a form most dissimilar. Lovelace believed that intuition and imagination were critical to effectively applying mathematical and scientific concepts. She valued metaphysics as much as mathematics, viewing both as tools for exploring "the unseen worlds around us." Death Lovelace died at the age of 36 on 27 November 1852, from uterine cancer. The illness lasted several months, in which time Annabella took command over whom Ada saw, and excluded all of her friends and confidants. Under her mother's influence, Ada had a religious transformation and was coaxed into repenting of her previous conduct and making Annabella her executor. She lost contact with her husband after confessing something to him on 30 August which caused him to abandon her bedside. It is not known what she told him. She was buried, at her request, next to her father at the Church of St. Mary Magdalene in Hucknall, Nottinghamshire. A memorial plaque, written in Latin, to her and her father is in the chapel attached to Horsley Towers. Work Throughout her life, Lovelace was strongly interested in scientific developments and fads of the day, including phrenology and mesmerism. After her work with Babbage, Lovelace continued to work on other projects. In 1844, she commented to a friend Woronzow Greig about her desire to create a mathematical model for how the brain gives rise to thoughts and nerves to feelings ("a calculus of the nervous system"). She never achieved this, however. In part, her interest in the brain came from a long-running pre-occupation, inherited from her mother, about her "potential" madness. As part of her research into this project, she visited the electrical engineer Andrew Crosse in 1844 to learn how to carry out electrical experiments. In the same year, she wrote a review of a paper by Baron Karl von Reichenbach, Researches on Magnetism, but this was not published and does not appear to have progressed past the first draft. In 1851, the year before her cancer struck, she wrote to her mother mentioning "certain productions" she was working on regarding the relation of maths and music. Lovelace first met Charles Babbage in June 1833, through their mutual friend Mary Somerville. Later that month, Babbage invited Lovelace to see the prototype for his difference engine. She became fascinated with the machine and used her relationship with Somerville to visit Babbage as often as she could. Babbage was impressed by Lovelace's intellect and analytic skills. He called her "The Enchantress of Number." In 1843, he wrote to her: During a nine-month period in 1842–43, Lovelace translated the Italian mathematician Luigi Menabrea's article on Babbage's newest proposed machine, the Analytical Engine. With the article, she appended a set of notes. Explaining the Analytical Engine's function was a difficult task, as many other scientists did not really grasp the concept and the British establishment had shown little interest in it. Lovelace's notes even had to explain how the Analytical Engine differed from the original Difference Engine. Her work was well received at the time; the scientist Michael Faraday described himself as a supporter of her writing. The notes are around three times longer than the article itself and include (in Note G), in complete detail, a method for calculating a sequence of Bernoulli numbers using the Analytical Engine, which might have run correctly had it ever been built (only Babbage's Difference Engine has been built, completed in London in 2002). Based on this work, Lovelace is now considered by many to be the first computer programmer and her method has been called the world's first computer program. Others dispute this because some of Charles Babbage's earlier writings could be considered computer programs. Note G also contains Lovelace's dismissal of artificial intelligence. She wrote that "The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis; but it has no power of anticipating any analytical relations or truths." This objection has been the subject of much debate and rebuttal, for example by Alan Turing in his paper "Computing Machinery and Intelligence". Lovelace and Babbage had a minor falling out when the papers were published, when he tried to leave his own statement (criticising the government's treatment of his Engine) as an unsigned preface, which could have been mistakenly interpreted as a joint declaration. When Taylor's Scientific Memoirs ruled that the statement should be signed, Babbage wrote to Lovelace asking her to withdraw the paper. This was the first that she knew he was leaving it unsigned, and she wrote back refusing to withdraw the paper. The historian Benjamin Woolley theorised that "His actions suggested he had so enthusiastically sought Ada's involvement, and so happily indulged her ... because of her 'celebrated name'." Their friendship recovered, and they continued to correspond. On 12 August 1851, when she was dying of cancer, Lovelace wrote to him asking him to be her executor, though this letter did not give him the necessary legal authority. Part of the terrace at Worthy Manor was known as Philosopher's Walk, as it was there that Lovelace and Babbage were reputed to have walked while discussing mathematical principles. First computer program In 1840, Babbage was invited to give a seminar at the University of Turin about his Analytical Engine. Luigi Menabrea, a young Italian engineer and the future Prime Minister of Italy, transcribed Babbage's lecture into French, and this transcript was subsequently published in the Bibliothèque universelle de Genève in October 1842. Babbage's friend Charles Wheatstone commissioned Ada Lovelace to translate Menabrea's paper into English. She then augmented the paper with notes, which were added to the translation. Ada Lovelace spent the better part of a year doing this, assisted with input from Babbage. These notes, which are more extensive than Menabrea's paper, were then published in the September 1843 edition of Taylor's Scientific Memoirs under the initialism AAL. Ada Lovelace's notes were labelled alphabetically from A to G. In note G, she describes an algorithm for the Analytical Engine to compute Bernoulli numbers. It is considered to be the first published algorithm ever specifically tailored for implementation on a computer, and Ada Lovelace has often been cited as the first computer programmer for this reason. The engine was never completed so her program was never tested. In 1953, more than a century after her death, Ada Lovelace's notes on Babbage's Analytical Engine were republished as an appendix to B. V. Bowden's Faster than Thought: A Symposium on Digital Computing Machines. The engine has now been recognised as an early model for a computer and her notes as a description of a computer and software. Insight into potential of computing devices In her notes, Ada Lovelace emphasised the difference between the Analytical Engine and previous calculating machines, particularly its ability to be programmed to solve problems of any complexity. She realised the potential of the device extended far beyond mere number crunching. In her notes, she wrote: This analysis was an important development from previous ideas about the capabilities of computing devices and anticipated the implications of modern computing one hundred years before they were realised. Walter Isaacson ascribes Ada's insight regarding the application of computing to any process based on logical symbols to an observation about textiles: "When she saw some mechanical looms that used punchcards to direct the weaving of beautiful patterns, it reminded her of how Babbage's engine used punched cards to make calculations." This insight is seen as significant by writers such as Betty Toole and Benjamin Woolley, as well as the programmer John Graham-Cumming, whose project Plan 28 has the aim of constructing the first complete Analytical Engine. According to the historian of computing and Babbage specialist Doron Swade: Ada saw something that Babbage in some sense failed to see. In Babbage's world his engines were bound by number...What Lovelace saw...was that number could represent entities other than quantity. So once you had a machine for manipulating numbers, if those numbers represented other things, letters, musical notes, then the machine could manipulate symbols of which number was one instance, according to rules. It is this fundamental transition from a machine which is a number cruncher to a machine for manipulating symbols according to rules that is the fundamental transition from calculation to computation—to general-purpose computation—and looking back from the present high ground of modern computing, if we are looking and sifting history for that transition, then that transition was made explicitly by Ada in that 1843 paper. Controversy over contribution Though Lovelace is often referred to as the first computer programmer, some biographers, computer scientists and historians of computing claim otherwise. Allan G. Bromley, in the 1990 article Difference and Analytical Engines: Bruce Collier, who later wrote a biography of Babbage, wrote in his 1970 Harvard University PhD thesis that Lovelace "made a considerable contribution to publicizing the Analytical Engine, but there is no evidence that she advanced the design or theory of it in any way". Eugene Eric Kim and Betty Alexandra Toole consider it "incorrect" to regard Lovelace as the first computer programmer, as Babbage wrote the initial programs for his Analytical Engine, although the majority were never published. Bromley notes several dozen sample programs prepared by Babbage between 1837 and 1840, all substantially predating Lovelace's notes. Dorothy K. Stein regards Lovelace's notes as "more a reflection of the mathematical uncertainty of the author, the political purposes of the inventor, and, above all, of the social and cultural context in which it was written, than a blueprint for a scientific development." Doron Swade, a specialist on history of computing known for his work on Babbage, discussed Lovelace during a lecture on Babbage's analytical engine. He explained that Ada was only a "promising beginner" instead of genius in mathematics, that she began studying basic concepts of mathematics five years after Babbage conceived the analytical engine so she could not have made important contributions to it, and that she only published the first computer program instead of actually writing it. But he agrees that Ada was the only person to see the potential of the analytical engine as a machine capable of expressing entities other than quantities. In his self-published book, Idea Makers, Stephen Wolfram defends Lovelace's contributions. While acknowledging that Babbage wrote several unpublished algorithms for the Analytical Engine prior to Lovelace's notes, Wolfram argues that "there's nothing as sophisticated—or as clean—as Ada's computation of the Bernoulli numbers. Babbage certainly helped and commented on Ada's work, but she was definitely the driver of it." Wolfram then suggests that Lovelace's main achievement was to distill from Babbage's correspondence "a clear exposition of the abstract operation of the machine—something which Babbage never did." In popular culture 1810s Lord Byron wrote the poem "Fare Thee Well" to his wife Lady Byron in 1816, following their separation after the birth of Ada Lovelace. In the poem he writes: And when thou would'st solace gather— When our child's first accents flow— Wilt thou teach her to say "Father!" Though his care she must forego? When her little hands shall press thee— When her lip to thine is pressed— Think of him whose prayer shall bless thee— Think of him thy love had blessed! Should her lineaments resemble Those thou never more may'st see, Then thy heart will softly tremble With a pulse yet true to me. 1970s Lovelace is portrayed in Romulus Linney's 1977 play Childe Byron. 1990s In the 1990 steampunk novel The Difference Engine by William Gibson and Bruce Sterling, Lovelace delivers a lecture on the "punched cards" programme which proves Gödel's incompleteness theorems decades before their actual discovery. In the 1997 film Conceiving Ada, a computer scientist obsessed with Ada finds a way of communicating with her in the past by means of "undying information waves". In Tom Stoppard's 1993 play Arcadia, the precocious teenage genius Thomasina Coverly—a character "apparently based" on Ada Lovelace (the play also involves Lord Byron)—comes to understand chaos theory, and theorises the second law of thermodynamics, before either is officially recognised. 2000s Lovelace features in John Crowley's 2005 novel, Lord Byron's Novel: The Evening Land, as an unseen character whose personality is forcefully depicted in her annotations and anti-heroic efforts to archive her father's lost novel. 2010s The 2015 play Ada and the Engine by Lauren Gunderson portrays Lovelace and Charles Babbage in unrequited love, and it imagines a post-death meeting between Lovelace and her father. Lovelace and Babbage are the main characters in Sydney Padua's webcomic and graphic novel The Thrilling Adventures of Lovelace and Babbage. The comic features extensive footnotes on the history of Ada Lovelace, and many lines of dialogue are drawn from actual correspondence. Lovelace and Mary Shelley as teenagers are the central characters in Jordan Stratford's steampunk series, The Wollstonecraft Detective Agency. Lovelace, identified as Ada Augusta Byron, is portrayed by Lily Lesser in the second season of The Frankenstein Chronicles. She is employed as an "analyst" to provide the workings of a life-sized humanoid automaton. The brass workings of the machine are reminiscent of Babbage's analytical engine. Her employment is described as keeping her occupied until she returns to her studies in advanced mathematics. Lovelace and Babbage appear as characters in the second season of the ITV series Victoria (2017). Emerald Fennell portrays Lovelace in the episode, "The Green-Eyed Monster." The Cardano cryptocurrency platform, which was launched in 2017, uses Ada as the name for their cryptocurrency and Lovelace as the smallest sub-unit of an Ada. "Lovelace" is the name given to the operating system designed by the character Cameron Howe in Halt and Catch Fire. Lovelace is a primary character in the 2019 Big Finish Doctor Who audio play The Enchantress of Numbers, starring Tom Baker as the Fourth Doctor and Jane Slavin as his current companion, WPC Ann Kelso. Lovelace is played by Finty Williams. In 2019, Lovelace is a featured character in the play STEM FEMMES by Philadelphia theater company Applied Mechanics. 2020s Lovelace features as a character in "Spyfall, Part 2", the second episode of Doctor Who, series 12, which first aired on BBC One on 5 January 2020. The character was portrayed by Sylvie Briggs, alongside characterisations of Charles Babbage and Noor Inayat Khan. In 2021, Nvidia named their upcoming GPU architecture (to be released in 2022), "Ada Lovelace", after her. Commemoration The computer language Ada, created on behalf of the United States Department of Defense, was named after Lovelace. The reference manual for the language was approved on 10 December 1980 and the Department of Defense Military Standard for the language, MIL-STD-1815, was given the number of the year of her birth. In 1981, the Association for Women in Computing inaugurated its Ada Lovelace Award. Since 1998, the British Computer Society (BCS) has awarded the Lovelace Medal, and in 2008 initiated an annual competition for women students. BCSWomen sponsors the Lovelace Colloquium, an annual conference for women undergraduates. Ada College is a further-education college in Tottenham Hale, London, focused on digital skills. Ada Lovelace Day is an annual event celebrated on the second Tuesday of October, which began in 2009. Its goal is to "... raise the profile of women in science, technology, engineering, and maths," and to "create new role models for girls and women" in these fields. Events have included Wikipedia edit-a-thons with the aim of improving the representation of women on Wikipedia in terms of articles and editors to reduce unintended gender bias on Wikipedia. The Ada Initiative was a non-profit organisation dedicated to increasing the involvement of women in the free culture and open source movements. The Engineering in Computer Science and Telecommunications College building in Zaragoza University is called the Ada Byron Building. The computer centre in the village of Porlock, near where Lovelace lived, is named after her. Ada Lovelace House is a council-owned building in Kirkby-in-Ashfield, Nottinghamshire, near where Lovelace spent her infancy. In 2012, a Google Doodle and blog post honoured her on her birthday. In 2013, Ada Developers Academy was founded and named after her. The mission of Ada Developers Academy is to diversify tech by providing women and gender diverse people the skills, experience, and community support to become professional software developers to change the face of tech. On 17 September 2013, an episode of Great Lives about Ada Lovelace aired. As of November 2015, all new British passports have included an illustration of Lovelace and Babbage. In 2017, a Google Doodle honoured her with other women on International Women's Day. On 2 February 2018, Satellogic, a high-resolution Earth observation imaging and analytics company, launched a ÑuSat type micro-satellite named in honour of Ada Lovelace. In March 2018, The New York Times published a belated obituary for Ada Lovelace. On 27 July 2018, Senator Ron Wyden submitted, in the United States Senate, the designation of 9 October 2018 as National Ada Lovelace Day: "To honor the life and contributions of Ada Lovelace as a leading woman in science and mathematics". The resolution (S.Res.592) was considered, and agreed to without amendment and with a preamble by unanimous consent. In November 2020 it was announced that Trinity College Dublin whose library had previously held forty busts, all of them of men, was commissioning four new busts of women, one of whom was to be Lovelace. Bicentenary The bicentenary of Ada Lovelace's birth was celebrated with a number of events, including: The Ada Lovelace Bicentenary Lectures on Computability, Israel Institute for Advanced Studies, 20 December 2015 – 31 January 2016. Ada Lovelace Symposium, University of Oxford, 13–14 October 2015. Ada.Ada.Ada, a one-woman show about the life and work of Ada Lovelace (using an LED dress), premiered at Edinburgh International Science Festival on 11 April 2015, and continues to touring internationally to promote diversity on STEM at technology conferences, businesses, government and educational organisations. Special exhibitions were displayed by the Science Museum in London, England and the Weston Library (part of the Bodleian Library) in Oxford, England. Publications Lovelace, Ada King. Ada, the Enchantress of Numbers: A Selection from the Letters of Lord Byron's Daughter and her Description of the First Computer. Mill Valley, CA: Strawberry Press, 1992. . Publication history Six copies of the 1843 first edition of Sketch of the Analytical Engine with Ada Lovelace's "Notes" have been located. Three are held at Harvard University, one at the University of Oklahoma, and one at the United States Air Force Academy. On 20 July 2018, the sixth copy was sold at auction to an anonymous buyer for £95,000. A digital facsimile of one of the copies in the Harvard University Library is available online. In December 2016, a letter written by Ada Lovelace was forfeited by Martin Shkreli to the New York State Department of Taxation and Finance for unpaid taxes owed by Shkreli. See also Ai-Da (robot) Code: Debugging the Gender Gap List of pioneers in computer science Timeline of women in science Women in computing Women in STEM fields Explanatory notes References General sources . . . . . . . With notes upon the memoir by the translator. Miller, Clair Cain. "Ada Lovelace, 1815–1852," New York Times, 8 March 2018. . . . . . . . Further reading Miranda Seymour, In Byron's Wake: The Turbulent Lives of Byron's Wife and Daughter: Annabella Milbanke and Ada Lovelace, Pegasus, 2018, 547 pp. Christopher Hollings, Ursula Martin, and Adrian Rice, Ada Lovelace: The Making of a Computer Scientist, Bodleian Library, 2018, 114 pp. Jenny Uglow, "Stepping Out of Byron's Shadow", The New York Review of Books, vol. LXV, no. 18 (22 November 2018), pp. 30–32. Jennifer Chiaverini, Enchantress of Numbers, Dutton, 2017, 426 pp. External links "Ada's Army gets set to rewrite history at Inspirefest 2018" by Luke Maxwell, 4 August 2018 "Untangling the Tale of Ada Lovelace" by Stephen Wolfram, December 2015 1815 births 1852 deaths 19th-century British women scientists 19th-century British writers 19th-century English mathematicians 19th-century English women writers 19th-century British inventors 19th-century English nobility Ada (programming language) British countesses British women computer scientists British women mathematicians Burials in Nottinghamshire Ada Women computer scientists Computer designers Daughters of barons Deaths from cancer in England Deaths from uterine cancer English computer programmers English people of Scottish descent English women poets Lord Byron Mathematicians from London Women of the Victorian era Burials at the Church of St Mary Magdalene, Hucknall

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

991

https://en.wikipedia.org/wiki/Absolute%20value

Absolute value

In mathematics, the absolute value or modulus of a real number , is the non-negative value without regard to its sign. Namely, if is a positive number, and if is negative (in which case negating makes positive), and For example, the absolute value of 3 and the absolute value of −3 is The absolute value of a number may be thought of as its distance from zero. Generalisations of the absolute value for real numbers occur in a wide variety of mathematical settings. For example, an absolute value is also defined for the complex numbers, the quaternions, ordered rings, fields and vector spaces. The absolute value is closely related to the notions of magnitude, distance, and norm in various mathematical and physical contexts. Terminology and notation In 1806, Jean-Robert Argand introduced the term module, meaning unit of measure in French, specifically for the complex absolute value, and it was borrowed into English in 1866 as the Latin equivalent modulus. The term absolute value has been used in this sense from at least 1806 in French and 1857 in English. The notation , with a vertical bar on each side, was introduced by Karl Weierstrass in 1841. Other names for absolute value include numerical value and magnitude. In programming languages and computational software packages, the absolute value of x is generally represented by abs(x), or a similar expression. The vertical bar notation also appears in a number of other mathematical contexts: for example, when applied to a set, it denotes its cardinality; when applied to a matrix, it denotes its determinant. Vertical bars denote the absolute value only for algebraic objects for which the notion of an absolute value is defined, notably an element of a normed division algebra, for example a real number, a complex number, or a quaternion. A closely related but distinct notation is the use of vertical bars for either the Euclidean norm or sup norm of a vector although double vertical bars with subscripts respectively) are a more common and less ambiguous notation. Definition and properties Real numbers For any the absolute value or modulus is denoted , with a vertical bar on each side of the quantity, and is defined as The absolute value is thus always either a positive number or zero, but never negative. When itself is negative then its absolute value is necessarily positive From an analytic geometry point of view, the absolute value of a real number is that number's distance from zero along the real number line, and more generally the absolute value of the difference of two real numbers is the distance between them. The notion of an abstract distance function in mathematics can be seen to be a generalisation of the absolute value of the difference (see "Distance" below). Since the square root symbol represents the unique positive square root, when applied to a positive number, it follows that This is equivalent to the definition above, and may be used as an alternative definition of the absolute value of real numbers. The absolute value has the following four fundamental properties (a, b are real numbers), that are used for generalization of this notion to other domains: Non-negativity, positive definiteness, and multiplicativity are readily apparent from the definition. To see that subadditivity holds, first note that with its sign chosen to make the result positive. Now, since it follows that, whichever of is the value one has for all Consequently, , as desired. Some additional useful properties are given below. These are either immediate consequences of the definition or implied by the four fundamental properties above. Two other useful properties concerning inequalities are: These relations may be used to solve inequalities involving absolute values. For example: The absolute value, as "distance from zero", is used to define the absolute difference between arbitrary real numbers, the standard metric on the real numbers. Complex numbers Since the complex numbers are not ordered, the definition given at the top for the real absolute value cannot be directly applied to complex numbers. However, the geometric interpretation of the absolute value of a real number as its distance from 0 can be generalised. The absolute value of a complex number is defined by the Euclidean distance of its corresponding point in the complex plane from the origin. This can be computed using the Pythagorean theorem: for any complex number where and are real numbers, the absolute value or modulus is and is defined by the Pythagorean addition of and , where and denote the real and imaginary parts respectively. When the is zero, this coincides with the definition of the absolute value of the When a complex number is expressed in its polar form its absolute value Since the product of any complex number and its with the same absolute value, is always the non-negative real number the absolute value of a complex number is the square root which is therefore called the absolute square or squared modulus This generalizes the alternative definition for reals: The complex absolute value shares the four fundamental properties given above for the real absolute value. Absolute value function The real absolute value function is continuous everywhere. It is differentiable everywhere except for . It is monotonically decreasing on the interval and monotonically increasing on the interval . Since a real number and its opposite have the same absolute value, it is an even function, and is hence not invertible. The real absolute value function is a piecewise linear, convex function. For both real and complex numbers the absolute value function is idempotent (meaning that the absolute value of any absolute value is itself). Relationship to the sign function The absolute value function of a real number returns its value irrespective of its sign, whereas the sign (or signum) function returns a number's sign irrespective of its value. The following equations show the relationship between these two functions: or and for , Derivative The real absolute value function has a derivative for every , but is not differentiable at . Its derivative for is given by the step function: The real absolute value function is an example of a continuous function that achieves a global minimum where the derivative does not exist. The subdifferential of  at  is the interval . The complex absolute value function is continuous everywhere but complex differentiable nowhere because it violates the Cauchy–Riemann equations. The second derivative of  with respect to  is zero everywhere except zero, where it does not exist. As a generalised function, the second derivative may be taken as two times the Dirac delta function. Antiderivative The antiderivative (indefinite integral) of the real absolute value function is where is an arbitrary constant of integration. This is not a complex antiderivative because complex antiderivatives can only exist for complex-differentiable (holomorphic) functions, which the complex absolute value function is not. Distance The absolute value is closely related to the idea of distance. As noted above, the absolute value of a real or complex number is the distance from that number to the origin, along the real number line, for real numbers, or in the complex plane, for complex numbers, and more generally, the absolute value of the difference of two real or complex numbers is the distance between them. The standard Euclidean distance between two points and in Euclidean -space is defined as: This can be seen as a generalisation, since for and real, i.e. in a 1-space, according to the alternative definition of the absolute value, and for and complex numbers, i.e. in a 2-space, {| |- | | |- | | |- | | |} The above shows that the "absolute value"-distance, for real and complex numbers, agrees with the standard Euclidean distance, which they inherit as a result of considering them as one and two-dimensional Euclidean spaces, respectively. The properties of the absolute value of the difference of two real or complex numbers: non-negativity, identity of indiscernibles, symmetry and the triangle inequality given above, can be seen to motivate the more general notion of a distance function as follows: A real valued function on a set is called a metric (or a distance function) on , if it satisfies the following four axioms: {| |- |style="width:250px" | |Non-negativity |- | |Identity of indiscernibles |- | |Symmetry |- | |Triangle inequality |} Generalizations Ordered rings The definition of absolute value given for real numbers above can be extended to any ordered ring. That is, if  is an element of an ordered ring R, then the absolute value of , denoted by , is defined to be: where is the additive inverse of , 0 is the additive identity, and < and ≥ have the usual meaning with respect to the ordering in the ring. Fields The four fundamental properties of the absolute value for real numbers can be used to generalise the notion of absolute value to an arbitrary field, as follows. A real-valued function  on a field  is called an absolute value (also a modulus, magnitude, value, or valuation) if it satisfies the following four axioms: {| cellpadding=10 |- | |Non-negativity |- | |Positive-definiteness |- | |Multiplicativity |- | |Subadditivity or the triangle inequality |} Where 0 denotes the additive identity of . It follows from positive-definiteness and multiplicativity that , where 1 denotes the multiplicative identity of . The real and complex absolute values defined above are examples of absolute values for an arbitrary field. If is an absolute value on , then the function  on , defined by , is a metric and the following are equivalent: satisfies the ultrametric inequality for all , , in . is bounded in R. for every . for all for all . An absolute value which satisfies any (hence all) of the above conditions is said to be non-Archimedean, otherwise it is said to be Archimedean. Vector spaces Again the fundamental properties of the absolute value for real numbers can be used, with a slight modification, to generalise the notion to an arbitrary vector space. A real-valued function on a vector space  over a field , represented as , is called an absolute value, but more usually a norm, if it satisfies the following axioms: For all  in , and , in , {| cellpadding=10 |- | |Non-negativity |- | |Positive-definiteness |- | |Positive homogeneity or positive scalability |- | |Subadditivity or the triangle inequality |} The norm of a vector is also called its length or magnitude. In the case of Euclidean space , the function defined by is a norm called the Euclidean norm. When the real numbers are considered as the one-dimensional vector space , the absolute value is a norm, and is the -norm (see Lp space) for any . In fact the absolute value is the "only" norm on , in the sense that, for every norm on , . The complex absolute value is a special case of the norm in an inner product space, which is identical to the Euclidean norm when the complex plane is identified as the Euclidean plane . Composition algebras Every composition algebra A has an involution x → x* called its conjugation. The product in A of an element x and its conjugate x* is written N(x) = x x* and called the norm of x. The real numbers , complex numbers , and quaternions are all composition algebras with norms given by definite quadratic forms. The absolute value in these division algebras is given by the square root of the composition algebra norm. In general the norm of a composition algebra may be a quadratic form that is not definite and has null vectors. However, as in the case of division algebras, when an element x has a non-zero norm, then x has a multiplicative inverse given by x*/N(x). Notes References Bartle; Sherbert; Introduction to real analysis (4th ed.), John Wiley & Sons, 2011 . Nahin, Paul J.; An Imaginary Tale; Princeton University Press; (hardcover, 1998). . Mac Lane, Saunders, Garrett Birkhoff, Algebra, American Mathematical Soc., 1999. . Mendelson, Elliott, Schaum's Outline of Beginning Calculus, McGraw-Hill Professional, 2008. . O'Connor, J.J. and Robertson, E.F.; "Jean Robert Argand". Schechter, Eric; Handbook of Analysis and Its Foundations, pp. 259–263, "Absolute Values", Academic Press (1997) . External links Special functions Real numbers Norms (mathematics)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1004

https://en.wikipedia.org/wiki/April

April

April is the fourth month of the year in the Gregorian calendar, the fifth in the early Julian, the first of four months to have a length of 30 days, and the second of five months to have a length of less than 31 days. April is commonly associated with the season of autumn in parts of the Southern Hemisphere, and spring in parts of the Northern Hemisphere, where it is the seasonal equivalent to October in the Southern Hemisphere and vice versa. History The Romans gave this month the Latin name Aprilis but the derivation of this name is uncertain. The traditional etymology is from the verb aperire, "to open", in allusion to its being the season when trees and flowers begin to "open", which is supported by comparison with the modern Greek use of άνοιξη (ánixi) (opening) for spring. Since some of the Roman months were named in honor of divinities, and as April was sacred to the goddess Venus, her Veneralia being held on the first day, it has been suggested that Aprilis was originally her month Aphrilis, from her equivalent Greek goddess name Aphrodite (Aphros), or from the Etruscan name Apru. Jacob Grimm suggests the name of a hypothetical god or hero, Aper or Aprus. April was the second month of the earliest Roman calendar, before Ianuarius and Februarius were added by King Numa Pompilius about 700 BC. It became the fourth month of the calendar year (the year when twelve months are displayed in order) during the time of the decemvirs about 450 BC, when it also was given 29 days. The 30th day was added during the reform of the calendar undertaken by Julius Caesar in the mid-40s BC, which produced the Julian calendar. The Anglo-Saxons called April ēastre-monaþ. The Venerable Bede says in The Reckoning of Time that this month ēastre is the root of the word Easter. He further states that the month was named after a goddess Eostre whose feast was in that month. It is also attested by Einhard in his work, Vita Karoli Magni. St George's day is the twenty-third of the month; and St Mark's Eve, with its superstition that the ghosts of those who are doomed to die within the year will be seen to pass into the church, falls on the twenty-fourth. In China the symbolic of the earth by the emperor and princes of the blood took place in their third month, which frequently corresponds to April. In Finnish April is huhtikuu, meaning slash-and-burn moon, when gymnosperms for beat and burn clearing of farmland were felled. In Slovene, the most established traditional name is mali traven, meaning the month when plants start growing. It was first written in 1466 in the Škofja Loka manuscript. The month Aprilis had 30 days; Numa Pompilius made it 29 days long; finally Julius Caesar’s calendar reform made it again 30 days long, which was not changed in the calendar revision of Augustus Caesar in 8 BC. Additionally in the Spanish colony, Las Islas Filipinas (now known as the Philippines), the month Aprilis had a significant meaning to the life of the natives as it was associated to the influence of the Chinese during the Spanish colonial period. The importance of this aspect to the lives of the natives was formerly associated to an event called "Abril na Ikaw" as it is closely linked to the famous trader, April Yu. In Ancient Rome, the festival of Cerealia was held for seven days from mid-to-late April, but exact dates are uncertain. Feriae Latinae was also held in April, with the date varying. Other ancient Roman observances include Veneralia (April 1), Megalesia (April 10–16), Fordicidia (April 15), Parilia (April 21), Vinalia Urbana, Robigalia, and Serapia were celebrated on (April 25). Floralia was held April 27 during the Republican era, or April 28 on the Julian calendar, and lasted until May 3. However, these dates do not correspond to the modern Gregorian calendar. The Lyrids meteor shower appears on April 16 – April 26 each year, with the peak generally occurring on April 22. Eta Aquariids meteor shower also appears in April. It is visible from about April 21 to about May 20 each year with peak activity on or around May 6. The Pi Puppids appear on April 23, but only in years around the parent comet's perihelion date. The Virginids also shower at various dates in April. The "Days of April" (journées d'avril) is a name appropriated in French history to a series of insurrections at Lyons, Paris and elsewhere, against the government of Louis Philippe in 1834, which led to violent repressive measures, and to a famous trial known as the procès d'avril. April symbols April's birthstone is the diamond. The birth flower is typically listed as either the Daisy (Bellis perennis) or the Sweet Pea. The zodiac signs for the month of April are Aries (until April 20) and Taurus (April 20 onwards). April observances This list does not necessarily imply either official status nor general observance. Month-long observances In Catholic, Protestant and Orthodox tradition, April is the Month of the Resurrection of the Lord. April and March are the months in which is celebrated the moveable Feast of Easter Sunday. National Pet Month (United Kingdom) United States Arab American Heritage Month Autism Awareness Month Cancer Control Month Community College Awareness Month Confederate History Month (Alabama, Florida, Georgia, Louisiana, Mississippi, Texas, Virginia) Donate Life Month Financial Literacy Month Jazz Appreciation Month Mathematics and Statistics Awareness Month National Poetry Month National Poetry Writing Month Occupational Therapy Month National Prevent Child Abuse Month National Volunteer Month Parkinson's Disease Awareness Month Rosacea Awareness Month Sexual Assault Awareness Month United States Food months Fresh Florida Tomato Month National Food Month National Grilled Cheese Month National Pecan Month National Soft Pretzel Month National Soyfoods Month Non-Gregorian observances: 2021 (All Baha'i, Islamic, and Jewish observances begin at the sundown prior to the date listed, and end at sundown of the date in question unless otherwise noted.) List of observances set by the Bahá'í calendar List of observances set by the Chinese calendar List of observances set by the Hebrew calendar List of observances set by the Islamic calendar List of observances set by the Solar Hijri calendar Movable observances, 2021 dates Youth Homelessness Matters Day National Health Day (Kiribati): April 6 Oral, Head and Neck Cancer Awareness Week (United States): April 13–19 National Park Week (United States): April 18–26 Crime Victims' Rights Week (United States): April 19–25 National Volunteer Week: April 19–25 European Immunization Week: April 20–26 Day of Silence (United States): April 24 Pay It Forward Day: April 28 (International observance) Denim Day: April 29 (International observance) Day of Dialogue (United States) Vaccination Week In The Americas See: List of movable Western Christian observances See: List of movable Eastern Christian observances First Wednesday: April 1 National Day of Hope (United States) First Saturday: April 4 Ulcinj Municipality Day (Ulcinj, Montenegro) First Sunday: April 5 Daylight saving time ends (Australia and New Zealand) Geologists Day (former Soviet Union countries) Kanamara Matsuri (Kawasaki, Japan) Opening Day (United States) First full week: April 5–11 National Library Week (United States) National Library Workers Day (United States) (Tuesday of National Library week, April 4) National Bookmobile Day (Wednesday of National Library week, April 5) National Public Health Week (United States) National Public Safety Telecommunicators Week (United States) Second Wednesday: April 8 International Day of Pink Second Thursday: April 9 National Former Prisoner of War Recognition Day (United States) Second Friday of April: April 10 Fast and Prayer Day (Liberia) Air Force Day (Russia) Kamakura Matsuri at Tsurugaoka Hachiman (Kamakura, Japan), lasts until third Sunday. Second Sunday: April 12 Children's Day (Peru) Week of April 14: April 12–18 Pan-American Week (United States) Third Wednesday: April 15 Administrative Professionals' Day (New Zealand) Third Thursday: April 16 National High Five Day (United States) Third Saturday: April 18 Record Store Day (International observance) Last full week of April: April 19–25 Administrative Professionals Week (Malaysia, North America) World Immunization Week Week of April 23: April 19–25 Canada Book Week (Canada) Week of the New Moon: April 19–25 National Dark-Sky Week (United States) Third Monday: April 20 Patriots' Day (Massachusetts, Maine, United States) Queen's Official Birthday (Saint Helena, Ascension and Tristan da Cunha) Sechseläuten (Zürich, Switzerland) Wednesday of last full week of April: April 22 Administrative Professionals' Day (Hong Kong, North America) First Thursday after April 18: April 23 First Day of Summer (Iceland) Fourth Thursday: April 23 Take Our Daughters And Sons To Work Day (United States) Last Friday: April 24 Arbor Day (United States) Día de la Chupina (Rosario, Argentina) Last Friday in April to first Sunday in May: April 24-May 3 Arbour Week in Ontario Last Saturday: April 25 Children's Day (Colombia) National Rebuilding Day (United States) National Sense of Smell Day (United States) World Tai Chi and Qigong Day Last Sunday: April 26 Flag Day (Åland, Finland) Turkmen Racing Horse Festival (Turkmenistan) April 27 (moves to April 26 if April 27 is on a Sunday): April 27 Koningsdag (Netherlands) Last Monday: April 27 Confederate Memorial Day (Alabama, Georgia (U.S. state), and Mississippi, United States) Last Wednesday: April 29 International Noise Awareness Day Fixed observances April 1 April Fools' Day Arbor Day (Tanzania) Civil Service Day (Thailand) Cyprus National Day (Cyprus) Edible Book Day Fossil Fools Day Kha b-Nisan (Assyrian people) National Civil Service Day (Thailand) Odisha Day (Odisha, India) Start of Testicular Cancer Awareness week (United States), April 1–7 Season for Nonviolence January 30 – April 4 April 2 International Children's Book Day (International observance) Malvinas Day (Argentina) National Peanut Butter and Jelly Day (United States) Thai Heritage Conservation Day (Thailand) Unity of Peoples of Russia and Belarus Day (Belarus) World Autism Awareness Day (International observance) April 3 April 4 Children's Day (Hong Kong, Taiwan) Independence Day (Senegal) International Day for Mine Awareness and Assistance in Mine Action Peace Day (Angola) April 5 Children's Day (Palestinian territories) National Caramel Day (United States) Sikmogil (South Korea) April 6 Chakri Day (Thailand) National Beer Day (United Kingdom) New Beer's Eve (United States) Tartan Day (United States & Canada) April 7 Flag Day (Slovenia) Genocide Memorial Day (Rwanda), and its related observance: International Day of Reflection on the 1994 Rwanda Genocide (United Nations) Motherhood and Beauty Day (Armenia) National Beer Day (United States) No Housework Day Sheikh Abeid Amani Karume Day (Tanzania) Women's Day (Mozambique) World Health Day (International observance) April 8 Buddha's Birthday (Japan only, other countries follow different calendars) Feast of the First Day of the Writing of the Book of the Law (Thelema) International Romani Day (International observance) Trading Cards for Grown-ups Day April 9 Anniversary of the German Invasion of Denmark (Denmark) Baghdad Liberation Day (Iraqi Kurdistan) Constitution Day (Kosovo) Day of National Unity (Georgia) Day of the Finnish Language (Finland) Day of Valor or Araw ng Kagitingan (Philippines) Feast of the Second Day of the Writing of the Book of the Law (Thelema) International Banshtai Tsai Day Martyr's Day (Tunisia) National Former Prisoner of War Recognition Day (United States) Remembrance for Haakon Sigurdsson (The Troth) Vimy Ridge Day (Canada) April 10 Day of the Builder (Azerbaijan) Feast of the Third Day of the Writing of the Book of the Law (Thelema) Siblings Day (International observance) April 11 Juan Santamaría Day, anniversary of his death in the Second Battle of Rivas. (Costa Rica) International Louie Louie Day National Cheese Fondue Day (United States) World Parkinson's Day April 12 Children's Day (Bolivia and Haiti) Commemoration of first human in space by Yuri Gagarin: Cosmonautics Day (Russia) International Day of Human Space Flight Yuri's Night (International observance) Halifax Day (North Carolina) National Grilled Cheese Sandwich Day (United States) National Redemption Day (Liberia) Walk on Your Wild Side Day April 13 Jefferson's Birthday (United States) Katyn Memorial Day (Poland) Teacher's Day (Ecuador) First day of Thingyan (Myanmar) (April 13–16) Unfairly Prosecuted Persons Day (Slovakia) April 14 ʔabusibaree (Okinawa Islands, Japan) Ambedkar Jayanti (India) Black Day (South Korea) Commemoration of Anfal Genocide Against the Kurds (Iraqi Kurdistan) Dhivehi Language Day (Maldives) Day of Mologa (Yaroslavl Oblast, Russia) Day of the Georgian language (Georgia (country)) Season of Emancipation (April 14 to August 23) (Barbados) N'Ko Alphabet Day (Mande speakers) Pohela Boishakh (Bangladesh) Pana Sankranti (Odisha, India) Puthandu (Tamils) (India, Malaysia, Singapore, Sri Lanka) Second day of Songkran (Thailand) (Thailand) Pan American Day (several countries in the Americas) The first day of Takayama Spring Festival (Takayama, Gifu, Japan) Vaisakh (Punjab (region)), (India and Pakistan) Youth Day (Angola) April 15 Day of the Sun (North Korea). Hillsborough Disaster Memorial (Liverpool, England) Jackie Robinson Day (United States) National Banana Day (United States) Pohela Boishakh (West Bengal, India) (Note: celebrated on April 14 in Bangladesh) Last day of Songkran (Thailand) (Thailand) Tax Day, the official deadline for filing an individual tax return (or requesting an extension). (United States, Philippines) Universal Day of Culture World Art Day April 16 Birthday of José de Diego (Puerto Rico, United States) Birthday of Queen Margrethe II (Denmark) Emancipation Day (Washington, D.C., United States) Foursquare Day (International observance) Memorial Day for the Victims of the Holocaust (Hungary) National Healthcare Decisions Day (United States) Remembrance of Chemical Attack on Balisan and Sheikh Wasan (Iraqi Kurdistan) World Voice Day April 17 Blah Blah Blah Day Evacuation Day (Syria) FAO Day (Iraq) Flag Day (American Samoa) Malbec World Day National Cheeseball Day (United States) National Espresso Day (Italy) Women's Day (Gabon) World Hemophilia Day April 18 Anniversary of the Victory over the Teutonic Knights in the Battle of the Ice, 1242 (Russia) Army Day (Iran) Coma Patients' Day (Poland) Friend's Day (Brazil) Independence Day (Zimbabwe) International Day For Monuments and Sites Invention Day (Japan) Pet Owner's Independence Day April 19 Army Day (Brazil) Beginning of the Independence Movement (Venezuela) Bicycle Day Dutch-American Friendship Day (United States) Holocaust Remembrance Day (Poland) Indian Day (Brazil) King Mswati III's birthday (Swaziland) Landing of the 33 Patriots Day (Uruguay) National Garlic Day (United States) National Rice Ball Day (United States) Primrose Day (United Kingdom) April 20 420 (cannabis culture) (International) UN Chinese Language Day (United Nations) April 21 A&M Day (Texas A&M University) Civil Service Day (India) Day of Local Self-Government (Russia) Grounation Day (Rastafari movement) Heroic Defense of Veracruz (Mexico) Kang Pan-sok's Birthday (North Korea) Kartini Day (Indonesia) Local Self Government Day (Russia) National Tree Planting Day (Kenya) San Jacinto Day (Texas) Queen's Official Birthday (Falkland Islands) Tiradentes' Day (Brazil) Vietnam Book Day (Vietnam) April 22 Discovery Day (Brazil) Earth Day (International observance) and its related observance: International Mother Earth Day Holocaust Remembrance Day (Serbia) National Jelly Bean Day (United States) April 23 Castile and León Day (Castile and León, Spain) German Beer Day (Germany) Independence Day (Conch Republic, Key West, Florida) International Pixel-Stained Technopeasant Day Khongjom Day (Manipur, India) National Sovereignty and Children's Day (Turkey and Northern Cyprus) Navy Day (China) St George's Day (England) and its related observances: Canada Book Day (Canada) La Diada de Sant Jordi (Catalonia, Spain) World Book Day UN English Language Day (United Nations) April 24 Armenian Genocide Remembrance Day (Armenia) Concord Day (Niger) Children's Day (Zambia) Democracy Day (Nepal) Fashion Revolution Day Flag Day (Ireland) International Sculpture Day Kapyong Day (Australia) Labour Safety Day (Bangladesh) National Panchayati Raj Day (India) National Pigs in a Blanket Day (United States) Republic Day (The Gambia) St Mark's Eve (Western Christianity) World Day for Laboratory Animals April 25 Anniversary of the First Cabinet of Kurdish Government (Iraqi Kurdistan) Anzac Day (Australia, New Zealand) Arbor Day (Germany) DNA Day Feast of Saint Mark (Western Christianity) Flag Day (Faroe Islands) Flag Day (Swaziland) Freedom Day (Portugal) Liberation Day (Italy) Major Rogation (Western Christianity) Military Foundation Day (North Korea) National Zucchini Bread Day (United States) Parental Alienation Awareness Day Red Hat Society Day Sinai Liberation Day (Egypt) World Malaria Day April 26 Chernobyl disaster related observances: Memorial Day of Radiation Accidents and Catastrophes (Russia) Day of Remembrance of the Chernobyl tragedy (Belarus) Confederate Memorial Day (Florida, United States) Hug A Friend Day Hug an Australian Day Lesbian Visibility Day National Pretzel Day (United States) Old Permic Alphabet Day Union Day (Tanzania) World Intellectual Property Day April 27 Day of Russian Parliamentarism (Russia) Day of the Uprising Against the Occupying Forces (Slovenia) Flag Day (Moldova) Freedom Day (South Africa) UnFreedom Day Independence Day (Sierra Leone) Independence Day (Togo) National Day (Mayotte) National Day (Sierra Leone) National Prime Rib Day (United States) National Veterans' Day (Finland) April 28 Lawyers' Day (Orissa, India) Mujahideen Victory Day (Afghanistan) National Day (Sardinia, Italy) National Heroes Day (Barbados) Restoration of Sovereignty Day (Japan) Workers' Memorial Day and World Day for Safety and Health at Work (international) National Day of Mourning (Canada) April 29 Day of Remembrance for all Victims of Chemical Warfare (United Nations) International Dance Day (UNESCO) Princess Bedike's Birthday (Denmark) National Shrimp Scampi Day (United States) Shōwa Day, traditionally the start of the Golden Week holiday period, which is April 29 and May 3–5. (Japan) April 30 Armed Forces Day (Georgia (country)) Birthday of the King (Sweden) Camarón Day (French Foreign Legion) Children's Day (Mexico) Consumer Protection Day (Thailand) Honesty Day (United States) International Jazz Day (UNESCO) Martyr's Day (Pakistan) May Eve, the eve of the first day of summer in the Northern hemisphere (see May 1): Beltane begins at sunset in the Northern hemisphere, Samhain begins at sunset in the Southern hemisphere. (Neo-Druidic Wheel of the Year) Carodejnice (Czech Republic and Slovakia) Walpurgis Night (Central and Northern Europe) National Persian Gulf Day (Iran) Reunification Day (Vietnam) Russian State Fire Service Day (Russia) Tax Day (Canada) Teachers' Day (Paraguay) See also Germanic calendar List of historical anniversaries Sinking of the RMS Titanic References External links National Arbor Day Foundation 00

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1012

https://en.wikipedia.org/wiki/August%2022

August 22

Events Pre-1600 392 – Arbogast has Eugenius elected Western Roman Emperor. 851 – Battle of Jengland: Erispoe defeats Charles the Bald near the Breton town of Jengland. 1138 – Battle of the Standard between Scotland and England. 1485 – The Battle of Bosworth Field, the death of Richard III and the end of the House of Plantagenet. 1559 – Bartolomé Carranza, Spanish archbishop, is arrested for heresy. 1601–1900 1614 – Fettmilch Uprising: Jews are expelled from Frankfurt, Holy Roman Empire, following the plundering of the Judengasse. 1639 – Madras (now Chennai), India, is founded by the British East India Company on a sliver of land bought from local Nayak rulers. 1642 – Charles I raises his standard in Nottingham, which marks the beginning of the English Civil War. 1654 – Jacob Barsimson arrives in New Amsterdam. He is the first known Jewish immigrant to America. 1711 – Britain's Quebec Expedition loses eight ships and almost nine hundred soldiers, sailors and women to rocks at Pointe-aux-Anglais. 1717 – Spanish troops land on Sardinia. 1770 – James Cook names and lands on Possession Island, and claims the east coast of Australia for Britain as New South Wales. 1777 – British forces abandon the Siege of Fort Stanwix after hearing rumors of Continental Army reinforcements. 1780 – James Cook's ship returns to England (Cook having been killed on Hawaii during the voyage). 1791 – Beginning of the Haitian Slave Revolution in Saint-Domingue, Haiti. 1798 – French troops land at Kilcummin, County Mayo, Ireland to aid the rebellion. 1827 – José de la Mar becomes President of Peru. 1846 – The Second Federal Republic of Mexico is established. 1849 – The first air raid in history. Austria launches pilotless balloons against the city of Venice. 1851 – The first America's Cup is won by the yacht America. 1864 – Twelve nations sign the First Geneva Convention, establishing the rules of protection of the victims of armed conflicts. 1875 – The Treaty of Saint Petersburg between Japan and Russia is ratified, providing for the exchange of Sakhalin for the Kuril Islands. 1894 – Mahatma Gandhi forms the Natal Indian Congress (NIC) in order to fight discrimination against Indian traders in Natal. 1901–present 1902 – Cadillac Motor Company is founded. 1902 – Theodore Roosevelt becomes the first President of the United States to make a public appearance in an automobile. 1902 – At least 4,000 people are killed by the 1902 Turkestan earthquake in the Tien Shan mountains. 1922 – Michael Collins, Commander-in-chief of the Irish Free State Army, is shot dead in an ambush during the Irish Civil War. 1934 – Bill Woodfull of Australia becomes the only test cricket captain to twice regain The Ashes. 1941 – World War II: German troops begin the Siege of Leningrad. 1942 – Brazil declares war on Germany, Japan and Italy. 1944 – World War II: Holocaust of Kedros in Crete by German forces. 1949 – The Queen Charlotte earthquake is Canada's strongest since the 1700 Cascadia earthquake. 1953 – The penal colony on Devil's Island is permanently closed. 1962 – The OAS attempts to assassinate French president Charles de Gaulle. 1963 – X-15 Flight 91 reaches the highest altitude of the X-15 program ( (354,200 feet)). 1966 – Labor movements NFWA and AWOC merge to become the United Farm Workers Organizing Committee (UFWOC), predecessor of the United Farm Workers. 1968 – Pope Paul VI arrives in Bogotá, Colombia. It is the first visit of a pope to Latin America. 1971 – J. Edgar Hoover and John Mitchell announce the arrest of 20 of the Camden 28. 1972 – Rhodesia is expelled by the IOC for its racist policies. 1973 – The Congress of Chile votes in favour of a resolution condemning President Salvador Allende's government and demands that he resign or else be unseated through force and new elections. 1978 – Nicaraguan Revolution: The FLSN seizes the National Congress of Nicaragua, along with over a thousand hostages. 1978 – The District of Columbia Voting Rights Amendment is passed by the U.S. Congress, although it is never ratified by a sufficient number of states. 1981 – Far Eastern Air Transport Flight 103 disintegrates in mid-air and crashes in Sanyi Township, Miaoli County, Taiwan. All 110 people on board are killed. 1985 – British Airtours Flight 28M suffers an engine fire during takeoff at Manchester Airport. The pilots abort but due to inefficient evacuation procedures 55 people are killed, mostly from smoke inhalation. 1989 – Nolan Ryan strikes out Rickey Henderson to become the first Major League Baseball pitcher to record 5,000 strikeouts. 1991 – Iceland is the first nation in the world to recognize the independence of the Baltic states. 1992 – FBI sniper Lon Horiuchi shoots and kills Vicki Weaver during an 11-day siege at her home at Ruby Ridge, Idaho. 2003 – Alabama Chief Justice Roy Moore is suspended after refusing to comply with a federal court order to remove a rock inscribed with the Ten Commandments from the lobby of the Alabama Supreme Court building. 2004 – Versions of The Scream and Madonna, two paintings by Edvard Munch, are stolen at gunpoint from a museum in Oslo, Norway. 2006 – Pulkovo Aviation Enterprise Flight 612 crashes near the Russian border over eastern Ukraine, killing all 170 people on board. 2006 – Grigori Perelman is awarded the Fields Medal for his proof of the Poincaré conjecture in mathematics but refuses to accept the medal. 2007 – The Texas Rangers defeat the Baltimore Orioles 30–3, the most runs scored by a team in modern Major League Baseball history. 2012 – Ethnic clashes over grazing rights for cattle in Kenya's Tana River District result in more than 52 deaths. Births Pre-1600 1412 – Frederick II, Elector of Saxony (d. 1464) 1570 – Franz von Dietrichstein, Roman Catholic archbishop and cardinal (d. 1636) 1599 – Agatha Marie of Hanau, German noblewoman (d. 1636) 1601–1900 1601 – Georges de Scudéry, French author, poet, and playwright (d. 1667) 1624 – Jean Regnault de Segrais, French author and poet (d. 1701) 1647 – Denis Papin, French physicist and mathematician, developed pressure cooking (d. 1712) 1679 – Pierre Guérin de Tencin, French cardinal (d. 1758) 1760 – Pope Leo XII (d. 1829) 1764 – Charles Percier, French architect and interior designer (d. 1838) 1771 – Henry Maudslay, English engineer (d. 1831) 1773 – Aimé Bonpland, French botanist and explorer (d. 1858) 1778 – James Kirke Paulding, American poet, playwright, and politician, 11th United States Secretary of the Navy (d. 1860) 1788 – Thomas Tredgold, English engineer and author (d. 1829) 1800 – William S. Harney, American general (d. 1889) 1800 – Samuel David Luzzatto, Italian poet and scholar (d. 1865) 1827 – Ezra Butler Eddy, Canadian businessman and politician (d. 1906) 1834 – Samuel Pierpont Langley, American physicist and astronomer (d. 1906) 1836 – Archibald Willard, American soldier and painter (d. 1918) 1844 – George W. De Long, American Naval officer and explorer (d. 1881) 1845 – William Lewis Douglas, American businessman and politician, 42nd Governor of Massachusetts (d. 1924) 1847 – John Forrest, Australian politician, 1st Premier of Western Australia (d. 1918) 1848 – Melville Elijah Stone, American publisher, founded the Chicago Daily News (d. 1929) 1854 – Milan I of Serbia (d. 1901) 1857 – Ned Hanlon, American baseball player and manager (d. 1937) 1860 – Paul Gottlieb Nipkow, Polish-German technician and inventor, created the Nipkow disk (d. 1940) 1860 – Alfred Ploetz, German physician, biologist, and eugenicist (d. 1940) 1862 – Claude Debussy, French pianist and composer (d. 1918) 1867 – Maximilian Bircher-Benner, Swiss physician and nutritionist (d. 1939) 1867 – Charles Francis Jenkins, American inventor (d. 1934) 1868 – Willis R. Whitney, American chemist (d. 1958) 1873 – Alexander Bogdanov, Russian physician and philosopher (d. 1928) 1874 – Max Scheler, German philosopher and author (d. 1928) 1880 – Gorch Fock, German author and poet (d. 1916) 1880 – George Herriman, American cartoonist (d. 1944) 1881 – James Newland, Australian soldier and policeman (d. 1949) 1882 – Raymonde de Laroche, French pilot (d. 1919) 1887 – Lutz Graf Schwerin von Krosigk, German jurist and politician, German Minister of Foreign Affairs (d. 1977) 1890 – Cecil Kellaway, South African actor (d. 1973) 1891 – Henry Bachtold, Australian soldier and railway engineer (d. 1983) 1891 – Jacques Lipchitz, Lithuanian-Italian sculptor (d. 1973) 1893 – Wilfred Kitching, English 7th General of The Salvation Army (d. 1977) 1893 – Dorothy Parker, American poet, short story writer, critic, and satirist (d. 1967) 1893 – Ernest H. Volwiler, American chemist (d. 1992) 1895 – László Almásy, Hungarian captain, pilot, and explorer (d. 1951) 1895 – Paul Comtois, Canadian lawyer and politician, 21st Lieutenant Governor of Quebec (d. 1966) 1896 – Laurence McKinley Gould, American geologist, educator, and polar explorer (d. 1995) 1897 – Bill Woodfull, Australian cricketer and educator (d. 1965) 1900 – Lisy Fischer, Swiss-born pianist and child prodigy (d. 1999) 1901–present 1902 – Thomas Pelly, American lawyer and politician (d. 1973) 1902 – Leni Riefenstahl, German actress, film director and propagandist (d. 2003) 1902 – Edward Rowe Snow, American historian and author (d. 1982) 1903 – Jerry Iger, American cartoonist, co-founded Eisner & Iger (d. 1990) 1904 – Deng Xiaoping, Chinese soldier and politician, 1st Vice Premier of the People's Republic of China (d. 1997) 1908 – Henri Cartier-Bresson, French photographer and painter (d. 2004) 1908 – Erwin Thiesies, German rugby player and coach (d. 1993) 1909 – Julius J. Epstein, American screenwriter and producer (d. 2000) 1909 – Mel Hein, American football player and coach (d. 1992) 1913 – Leonard Pagliero, English businessman and pilot (d. 2008) 1913 – Bruno Pontecorvo, Italian physicist and academic (d. 1993) 1914 – Jack Dunphy, American author and playwright (d. 1992) 1914 – Connie B. Gay, American businessman, co-founded the Country Music Hall of Fame and Museum (d. 1989) 1915 – David Dellinger, American activist (d. 2004) 1915 – James Hillier, Canadian-American scientist, co-designed the electron microscope (d. 2007) 1915 – Edward Szczepanik, Polish economist and politician, 15th Prime Minister of the Polish Republic in Exile (d. 2005) 1917 – John Lee Hooker, American singer-songwriter and guitarist (d. 2001) 1918 – Mary McGrory, American journalist and author (d. 2004) 1920 – Ray Bradbury, American science fiction writer and screenwriter (d. 2012) 1920 – Denton Cooley, American surgeon and scientist (d. 2016) 1921 – Dinos Dimopoulos, Greek director and screenwriter (d. 2003) 1921 – Tony Pawson, English cricketer, footballer, and journalist (d. 2012) 1922 – Roberto Aizenberg, Argentine painter and sculptor (d. 1996) 1922 – Theoni V. Aldredge, Greek-American costume designer (d. 2011) 1924 – James Kirkwood, Jr., American playwright and author (d. 1989) 1924 – Harishankar Parsai, Indian writer, satirist and humorist (d. 1995) 1925 – Honor Blackman, English actress and republican (d. 2020) 1926 – Bob Flanigan, American pop singer (d. 2011) 1928 – Tinga Seisay, Sierra Leonean academic and diplomat (d.2015) 1928 – Karlheinz Stockhausen, German composer and academic (d. 2007) 1929 – Valery Alekseyev, Russian anthropologist and author (d. 1991) 1929 – Ulrich Wegener, German police officer and general (d. 2017) 1930 – Gylmar dos Santos Neves, Brazilian footballer (d. 2013) 1932 – Gerald P. Carr, American engineer, colonel, and astronaut (d. 2020) 1933 – Sylva Koscina, Italian actress (d. 1994) 1934 – Norman Schwarzkopf, Jr., American general and engineer (d. 2012) 1935 – Annie Proulx, American novelist, short story writer, and journalist 1936 – Chuck Brown, American singer-songwriter, guitarist, and producer (d. 2012) 1936 – John Callaway, American journalist and producer (d. 2009) 1936 – Dale Hawkins, American singer-songwriter and guitarist (d. 2010) 1936 – Werner Stengel, German roller coaster designer and engineer, designed the Maverick roller coaster 1938 – Jean Berkey, American businesswoman and politician (d. 2013) 1939 – Valerie Harper, American actress (d. 2019) 1939 – Fred Milano, American doo-wop singer (d. 2012) 1939 – Carl Yastrzemski, American baseball player 1940 – Bill McCartney, American football player and coach, founded Promise Keepers 1941 – Bill Parcells, American football player and coach 1942 – Uğur Mumcu, Turkish journalist and author (d. 1993) 1943 – Alun Michael, Welsh police commissioner and politician, inaugural First Minister of Wales 1943 – Masatoshi Shima, Japanese computer scientist and engineer, co-designed the Intel 4004 1944 – Roger Cashmore, English physicist and academic 1945 – David Chase, American director, producer, and screenwriter 1945 – Ron Dante, American singer-songwriter and producer 1947 – Donna Jean Godchaux, American singer-songwriter 1947 – Cindy Williams, American actress and producer 1948 – David Marks, American singer-songwriter and guitarist 1949 – Doug Bair, American baseball player and coach 1949 – Diana Nyad, American swimmer and author 1950 – Ray Burris, American baseball player and coach 1950 – Scooter Libby, American lawyer and politician, Chief of Staff to the Vice President of the United States 1952 – Peter Laughner, American singer-songwriter and guitarist (d. 1977) 1953 – Paul Ellering, American weightlifter, wrestler, and manager 1955 – Chiranjeevi, Indian film actor, producer and politician 1956 – Paul Molitor, American baseball player and coach 1956 – Peter Taylor, Australian cricketer 1957 – Steve Davis, English snooker player, sportscaster, and author 1957 – Holly Dunn, American country music singer-songwriter (d. 2016) 1958 – Colm Feore, American-Canadian actor 1958 – Stevie Ray, American semi-retired wrestler 1958 – Vernon Reid, English-born American guitarist and songwriter 1959 – Juan Croucier, Cuban-American singer-songwriter, bass player, and producer 1959 – Pia Gjellerup, Danish lawyer and politician, Danish Minister of Finance 1959 – Mark Williams, English actor 1960 – Holger Gehrke, German footballer and manager 1960 – Collin Raye, American country music singer 1961 – Andrés Calamaro, Argentine singer-songwriter, guitarist, and producer 1961 – Iain Coucher, English businessman 1961 – Roland Orzabal, English singer-songwriter, guitarist, and producer 1961 – Debbi Peterson, American singer-songwriter and drummer 1962 – Stefano Tilli, Italian sprinter 1963 – Tori Amos, American singer-songwriter, pianist, and producer 1963 – James DeBarge, American R&B/soul singer 1963 – Terry Catledge, American basketball player 1964 – Trey Gowdy, American lawyer and U.S. Representative 1964 – Mats Wilander, Swedish-American tennis player and coach 1965 – Wendy Botha, South African-Australian surfer 1965 – David Reimer, Canadian victim of a botched circumcision and sex reassignment surgery (d. 2004) 1966 – GZA, American rapper and producer 1966 – Rob Witschge, Dutch footballer and manager 1967 – Ty Burrell, American actor and comedian 1967 – Paul Colman, Australian singer-songwriter and guitarist 1967 – Alfred Gough, American screenwriter and producer 1967 – Layne Staley, American singer-songwriter (d. 2002) 1968 – Casper Christensen, Danish comedian, actor, and screenwriter 1968 – Rich Lowry, American writer and magazine editor (National Review) 1968 – Aleksandr Mostovoi, Russian footballer 1968 – Elisabeth Murdoch, Australian businesswoman 1968 – Horst Skoff, Austrian tennis player (d. 2008) 1970 – Charlie Connelly, English author and broadcaster 1970 – Giada De Laurentiis, Italian-American chef and author 1970 – Tímea Nagy, Hungarian fencer 1971 – Craig Finn, American singer-songwriter and guitarist 1972 – Okkert Brits, South African pole vaulter 1972 – Paul Doucette, American singer-songwriter, guitarist, and drummer 1972 – Steve Kline, American baseball player and coach 1972 – Max Wilson, German-Brazilian race car driver 1973 – Roslina Bakar, Malaysian sport shooter 1973 – Howie Dorough, American singer-songwriter and dancer 1973 – Kristen Wiig, American actress, comedian, and screenwriter 1973 – Eurelijus Žukauskas, Lithuanian basketball player 1974 – Cory Gardner, American politician 1974 – Agustín Pichot, Argentinian rugby player 1975 – Clint Bolton, Australian footballer 1975 – Rodrigo Santoro, Brazilian actor 1976 – Marius Bezykornovas, Lithuanian footballer 1976 – Bryn Davies, American bassist, cellist, and pianist 1976 – Laurent Hernu, French decathlete 1976 – Randy Wolf, American baseball player 1977 – Heiðar Helguson, Icelandic footballer 1977 – Keren Cytter, Israeli visual artist and writer 1978 – James Corden, English actor, comedian, writer, and television presenter 1978 – Ioannis Gagaloudis, Greek basketball player 1979 – Matt Walters, American football player 1980 – Roland Benschneider, German footballer 1980 – Nicolas Macrozonaris, Canadian sprinter 1980 – Seiko Yamamoto, Japanese wrestler 1981 – Alex Holmes, American football player 1981 – Jang Hyun-kyu, South Korean footballer (d. 2012) 1981 – Christina Obergföll, German athlete 1983 – Theo Bos, Dutch cyclist 1983 – Jahri Evans, American football player 1984 – Lee Camp, English footballer 1984 – Lawrence Quaye, Ghanaian-Qatari footballer 1985 – Luke Russert, American journalist 1985 – Jey Uso, Samoan-American wrestler 1985 – Jimmy Uso, Samoan-American wrestler 1986 – Stephen Ireland, Irish footballer 1986 – Neville, English wrestler 1986 – Tokushōryū Makoto, Japanese sumo wrestler 1987 – Leonardo Moracci, Italian footballer 1987 – Apollo Crews, American wrestler 1989 – Giacomo Bonaventura, Italian footballer 1990 – Randall Cobb, American football player 1990 – Drew Hutchison, American baseball player 1990 – Robbie Rochow, Australian rugby league player 1991 – Federico Macheda, Italian footballer 1991 – Brayden Schenn, Canadian ice hockey player 1992 – Ema Burgić Bucko, Bosnian tennis player 1994 – Olli Määttä, Finnish ice hockey player 1995 – Dua Lipa, English singer-songwriter 1996 – Jessica-Jane Applegate, British Paralympic swimmer Deaths Pre-1600 408 – Stilicho, Roman general (b. 359) 1155 – Emperor Konoe of Japan (b. 1139) 1241 – Pope Gregory IX, (b. 1143) 1280 – Pope Nicholas III (b. 1225) 1304 – John II, Count of Holland (b. 1247) 1338 – William II, Duke of Athens (b. 1312) 1350 – Philip VI of France (b. 1293) 1358 – Isabella of France (b. 1295) 1425 – Eleanor, Princess of Asturias (b. 1423) 1456 – Vladislav II of Wallachia 1485 – Richard III of England (b. 1452) 1485 – James Harrington, Yorkist knight 1485 – John Howard, 1st Duke of Norfolk (b. 1430) 1485 – Richard Ratcliffe, supporter of Richard III 1485 – William Brandon, supporter of Henry VII (b. 1426) 1532 – William Warham, Archbishop of Canterbury (b. 1450) 1545 – Charles Brandon, 1st Duke of Suffolk, English politician and husband of Mary Tudor (b. c. 1484) 1553 – John Dudley, 1st Duke of Northumberland, English admiral and politician, Lord President of the Council (b. 1504) 1572 – Thomas Percy, 7th Earl of Northumberland, English leader of the Rising of the North (b. 1528) 1584 – Jan Kochanowski, Polish poet and playwright (b. 1530) 1599 – Luca Marenzio, Italian singer-songwriter (b. 1553) 1601–1900 1607 – Bartholomew Gosnold, English lawyer and explorer, founded the London Company (b. 1572) 1652 – Jacob De la Gardie, Estonian-Swedish soldier and politician, Lord High Constable of Sweden (b. 1583) 1664 – Maria Cunitz, Polish astronomer and author (b. 1610) 1680 – John George II, Elector of Saxony (b. 1613) 1681 – Philippe Delano, Dutch Plymouth Colony settler (b. 1602) 1701 – John Granville, 1st Earl of Bath, English soldier and politician, Lord Lieutenant of Ireland (b. 1628) 1711 – Louis François, duc de Boufflers, French general (b. 1644) 1752 – William Whiston, English mathematician, historian, and theologian (b. 1667) 1773 – George Lyttelton, 1st Baron Lyttelton, English poet and politician, Chancellor of the Exchequer (b. 1709) 1793 – Louis de Noailles, French general (b. 1713) 1797 – Dagobert Sigmund von Wurmser, French-Austrian field marshal (b. 1724) 1806 – Jean-Honoré Fragonard, French painter and illustrator (b. 1732) 1818 – Warren Hastings, English lawyer and politician, 1st Governor-General of Bengal (b. 1732) 1828 – Franz Joseph Gall, Austrian neuroanatomist and physiologist (b. 1758) 1850 – Nikolaus Lenau, Romanian-Austrian poet and author (b. 1802) 1861 – Xianfeng, Emperor of China (b. 1831) 1888 – Ágoston Trefort, Hungarian jurist and politician, Hungarian Minister of Education (b. 1817) 1891 – Jan Neruda, Czech journalist, author, and poet (b. 1834) 1901–present 1903 – Robert Gascoyne-Cecil, 3rd Marquess of Salisbury, English academic and politician, Prime Minister of the United Kingdom (b. 1830) 1904 – Kate Chopin, American novelist and poet (b. 1850) 1909 – Henry Radcliffe Crocker, English dermatologist and author (b. 1846) 1914 – Giacomo Radini-Tedeschi, Italian bishop and academic (b. 1859) 1918 – Korbinian Brodmann, German neurologist and academic (b. 1868) 1920 – Anders Zorn, Swedish artist (b. 1860) 1922 – Michael Collins, Irish rebel, counter-intelligence and military tactician, and politician; 2nd Irish Minister of Finance (b. 1890) 1926 – Charles William Eliot, American academic (b. 1834) 1933 – Alexandros Kontoulis, Greek general and diplomat (b. 1858) 1940 – Oliver Lodge, English physicist and academic (b. 1851) 1940 – Gerald Strickland, 1st Baron Strickland, Maltese lawyer and politician, 4th Prime Minister of Malta (b. 1861) 1942 – Michel Fokine, Russian dancer and choreographer (b. 1880) 1946 – Döme Sztójay, Hungarian general and politician, 35th Prime Minister of Hungary (b. 1883) 1950 – Kirk Bryan, American geologist and academic (b. 1888) 1951 – Jack Bickell, Canadian businessman and philanthropist (b. 1884) 1953 – Jim Tabor, American baseball player (b. 1916) 1958 – Roger Martin du Gard, French novelist and paleographer, Nobel Prize laureate (b. 1881) 1960 – Johannes Sikkar, Estonian soldier and politician, Prime Minister of Estonia in exile (b. 1897) 1963 – William Morris, 1st Viscount Nuffield, English businessman and philanthropist, founded Morris Motors (b. 1877) 1967 – Gregory Goodwin Pincus, American biologist and academic, co-created the birth-control pill (b. 1903) 1970 – Vladimir Propp, Russian philologist and scholar (b. 1895) 1974 – Jacob Bronowski, Polish-English mathematician, biologist, and author (b. 1908) 1976 – Gina Bachauer, Greek pianist and composer (b. 1913) 1976 – Juscelino Kubitschek, Brazilian physician and politician, 21st President of Brazil (b. 1902) 1977 – Sebastian Cabot, English actor (b. 1918) 1977 – Chunseong, Korean monk, philosopher and writer (b. 1891) 1978 – Jomo Kenyatta, Kenyan journalist and politician, 1st President of Kenya (b. 1894) 1979 – James T. Farrell, American novelist, short-story writer, and poet (b. 1904) 1980 – James Smith McDonnell, American pilot, engineer, and businessman, founded McDonnell Aircraft (b. 1899) 1981 – Vicente Manansala, Filipino painter (b. 1910) 1985 – Charles Gibson (historian), Historian of Mexico and its Indians, President of the American Historical Association (b. 1920) 1986 – Celâl Bayar, Turkish lawyer and politician, 3rd President of Turkey (b. 1883) 1987 – Joseph P. Lash, American author and journalist (b. 1909) 1989 – Robert Grondelaers, Belgian cyclist (b. 1933) 1989 – Huey P. Newton, American activist, co-founded the Black Panther Party (b. 1942) 1991 – Colleen Dewhurst, Canadian-American actress (b. 1924) 1991 – Boris Pugo, Russian soldier and politician, Soviet Minister of Interior (b. 1937) 1994 – Gilles Groulx, Canadian director and screenwriter (b. 1931) 1994 – Allan Houser, American sculptor and painter (b. 1914) 1995 – Johnny Carey, Irish footballer and manager (b. 1919) 1996 – Erwin Komenda, Austrian car designer and engineer (b. 1904) 2000 – Abulfaz Elchibey, 2nd President of Azerbaijan (b. 1938) 2003 – Arnold Gerschwiler, Swiss figure skater and coach (b. 1914) 2004 – Konstantin Aseev, Russian chess player and trainer (b. 1960) 2004 – Angus Bethune, Australian soldier and politician, 33rd Premier of Tasmania (b. 1908) 2004 – Daniel Petrie, Canadian director and producer (b. 1920) 2005 – Luc Ferrari, French-Italian director and composer (b. 1929) 2005 – Ernest Kirkendall, American chemist and metallurgist (b. 1914) 2007 – Grace Paley, American short story writer and poet (b. 1922) 2008 – Gladys Powers, English-Canadian soldier (b. 1899) 2009 – Muriel Duckworth, Canadian pacifist, feminist, and activist (b. 1908) 2009 – Elmer Kelton, American journalist and author (b. 1926) 2010 – Stjepan Bobek, Croatian footballer and manager (b. 1923) 2011 – Nick Ashford, American singer-songwriter and producer (b. 1942) 2011 – Jack Layton, Canadian academic and politician (b. 1950) 2011 – Casey Ribicoff, American philanthropist (b. 1922) 2012 – Nina Bawden, English author (b. 1925) 2012 – Paul Shan Kuo-hsi, Chinese cardinal (b. 1923) 2012 – Jeffrey Stone, American actor and screenwriter (b. 1926) 2013 – Paul Poberezny, American pilot and businessman, founded the Experimental Aircraft Association (b. 1921) 2013 – Andrea Servi, Italian footballer (b. 1984) 2014 – U. R. Ananthamurthy, Indian author, poet, and playwright (b. 1932) 2014 – Emmanuel Kriaras, Greek lexicographer and philologist (b. 1906) 2014 – Pete Ladygo, American football player and coach (b. 1928) 2014 – Noella Leduc, American baseball player (b. 1933) 2014 – John Sperling, American businessman, founded the University of Phoenix (b. 1921) 2014 – John S. Waugh, American chemist and academic (b. 1929) 2015 – Arthur Morris, Australian cricketer and journalist (b. 1922) 2015 – Ieng Thirith, Cambodian academic and politician (b. 1932) 2015 – Eric Thompson, English race car driver and book dealer (b. 1919) 2016 – S. R. Nathan, 6th President of Singapore (b. 1924) 2016 – Toots Thielemans, Belgian and American jazz musician (b. 1922) 2017 – Michael J. C. Gordon, British Computer scientist (b. 1948) 2018 – Ed King, American musician (b. 1949) 2018 – Krishna Reddy, Indian printmaker, sculptor and teacher (b. 1925) 2021 – Rod Gilbert, Canadian ice hockey player (b. 1941) Holidays and observances Christian feast day: Fabrizio Guinefort, the holy greyhound, feast day traditionally. Immaculate Heart of Mary (Roman Catholic calendar of 1960) Queenship of Mary Symphorian and Timotheus August 22 (Eastern Orthodox liturgics) Earliest day on which National Heroes' Day (Philippines) can fall, while August 28 is the latest; celebrated on the fourth Monday in August. Flag Day (Russia) Madras Day (Chennai and Tamil Nadu, India) End of Filseta feast in Ethiopian Orthodox Tewahedo and Eritrean Orthodox Tewahedo Church International Day Commemorating the Victims of Acts of Violence Based on Religion or Belief (International) References External links Days of the year August

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1018

https://en.wikipedia.org/wiki/Algebraically%20closed%20field

Algebraically closed field

In mathematics, a field is algebraically closed if every non-constant polynomial in (the univariate polynomial ring with coefficients in ) has a root in . Examples As an example, the field of real numbers is not algebraically closed, because the polynomial equation x2 + 1 = 0  has no solution in real numbers, even though all its coefficients (1 and 0) are real. The same argument proves that no subfield of the real field is algebraically closed; in particular, the field of rational numbers is not algebraically closed. Also, no finite field F is algebraically closed, because if a1, a2, ..., an are the elements of F, then the polynomial (x − a1)(x − a2) ⋯ (x − an) + 1 has no zero in F. By contrast, the fundamental theorem of algebra states that the field of complex numbers is algebraically closed. Another example of an algebraically closed field is the field of (complex) algebraic numbers. Equivalent properties Given a field F, the assertion "F is algebraically closed" is equivalent to other assertions: The only irreducible polynomials are those of degree one The field F is algebraically closed if and only if the only irreducible polynomials in the polynomial ring F[x] are those of degree one. The assertion "the polynomials of degree one are irreducible" is trivially true for any field. If F is algebraically closed and p(x) is an irreducible polynomial of F[x], then it has some root a and therefore p(x) is a multiple of x − a. Since p(x) is irreducible, this means that p(x) = k(x − a), for some k ∈ F \ {0}. On the other hand, if F is not algebraically closed, then there is some non-constant polynomial p(x) in F[x] without roots in F. Let q(x) be some irreducible factor of p(x). Since p(x) has no roots in F, q(x) also has no roots in F. Therefore, q(x) has degree greater than one, since every first degree polynomial has one root in F. Every polynomial is a product of first degree polynomials The field F is algebraically closed if and only if every polynomial p(x) of degree n ≥ 1, with coefficients in F, splits into linear factors. In other words, there are elements k, x1, x2, ..., xn of the field F such that p(x) = k(x − x1)(x − x2) ⋯ (x − xn). If F has this property, then clearly every non-constant polynomial in F[x] has some root in F; in other words, F is algebraically closed. On the other hand, that the property stated here holds for F if F is algebraically closed follows from the previous property together with the fact that, for any field K, any polynomial in K[x] can be written as a product of irreducible polynomials. Polynomials of prime degree have roots If every polynomial over F of prime degree has a root in F, then every non-constant polynomial has a root in F. It follows that a field is algebraically closed if and only if every polynomial over F of prime degree has a root in F. The field has no proper algebraic extension The field F is algebraically closed if and only if it has no proper algebraic extension. If F has no proper algebraic extension, let p(x) be some irreducible polynomial in F[x]. Then the quotient of F[x] modulo the ideal generated by p(x) is an algebraic extension of F whose degree is equal to the degree of p(x). Since it is not a proper extension, its degree is 1 and therefore the degree of p(x) is 1. On the other hand, if F has some proper algebraic extension K, then the minimal polynomial of an element in K \ F is irreducible and its degree is greater than 1. The field has no proper finite extension The field F is algebraically closed if and only if it has no proper finite extension because if, within the previous proof, the term "algebraic extension" is replaced by the term "finite extension", then the proof is still valid. (Note that finite extensions are necessarily algebraic.) Every endomorphism of Fn has some eigenvector The field F is algebraically closed if and only if, for each natural number n, every linear map from Fn into itself has some eigenvector. An endomorphism of Fn has an eigenvector if and only if its characteristic polynomial has some root. Therefore, when F is algebraically closed, every endomorphism of Fn has some eigenvector. On the other hand, if every endomorphism of Fn has an eigenvector, let p(x) be an element of F[x]. Dividing by its leading coefficient, we get another polynomial q(x) which has roots if and only if p(x) has roots. But if q(x) = xn + an − 1xn − 1+ ⋯ + a0, then q(x) is the characteristic polynomial of the n×n companion matrix Decomposition of rational expressions The field F is algebraically closed if and only if every rational function in one variable x, with coefficients in F, can be written as the sum of a polynomial function with rational functions of the form a/(x − b)n, where n is a natural number, and a and b are elements of F. If F is algebraically closed then, since the irreducible polynomials in F[x] are all of degree 1, the property stated above holds by the theorem on partial fraction decomposition. On the other hand, suppose that the property stated above holds for the field F. Let p(x) be an irreducible element in F[x]. Then the rational function 1/p can be written as the sum of a polynomial function q with rational functions of the form a/(x – b)n. Therefore, the rational expression can be written as a quotient of two polynomials in which the denominator is a product of first degree polynomials. Since p(x) is irreducible, it must divide this product and, therefore, it must also be a first degree polynomial. Relatively prime polynomials and roots For any field F, if two polynomials p(x),q(x) ∈ F[x] are relatively prime then they do not have a common root, for if a ∈ F was a common root, then p(x) and  q(x) would both be multiples of x − a and therefore they would not be relatively prime. The fields for which the reverse implication holds (that is, the fields such that whenever two polynomials have no common root then they are relatively prime) are precisely the algebraically closed fields. If the field F is algebraically closed, let p(x) and q(x) be two polynomials which are not relatively prime and let r(x) be their greatest common divisor. Then, since r(x) is not constant, it will have some root a, which will be then a common root of p(x) and q(x). If F is not algebraically closed, let p(x) be a polynomial whose degree is at least 1 without roots. Then p(x) and p(x) are not relatively prime, but they have no common roots (since none of them has roots). Other properties If F is an algebraically closed field and n is a natural number, then F contains all nth roots of unity, because these are (by definition) the n (not necessarily distinct) zeroes of the polynomial xn − 1. A field extension that is contained in an extension generated by the roots of unity is a cyclotomic extension, and the extension of a field generated by all roots of unity is sometimes called its cyclotomic closure. Thus algebraically closed fields are cyclotomically closed. The converse is not true. Even assuming that every polynomial of the form xn − a splits into linear factors is not enough to assure that the field is algebraically closed. If a proposition which can be expressed in the language of first-order logic is true for an algebraically closed field, then it is true for every algebraically closed field with the same characteristic. Furthermore, if such a proposition is valid for an algebraically closed field with characteristic 0, then not only is it valid for all other algebraically closed fields with characteristic 0, but there is some natural number N such that the proposition is valid for every algebraically closed field with characteristic p when p > N. Every field F has some extension which is algebraically closed. Such an extension is called an algebraically closed extension. Among all such extensions there is one and only one (up to isomorphism, but not unique isomorphism) which is an algebraic extension of F; it is called the algebraic closure of F. The theory of algebraically closed fields has quantifier elimination. Notes References Field (mathematics)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1020

https://en.wikipedia.org/wiki/Anatoly%20Karpov

Anatoly Karpov

Anatoly Yevgenyevich Karpov (; born May 23, 1951) is a Russian and former Soviet chess grandmaster, former World Chess Champion, ⁣and politician. He was the 12th World Chess Champion from 1975 to 1985, a three-time FIDE World Champion (1993, 1996, 1998), twice World Chess champion as a member of the USSR team (1985, 1989), and a six-time winner of Chess Olympiads as a member of the USSR team (1972, 1974, 1980, 1982, 1986, 1988). The International Association of Chess Press awarded him nine Chess "Oscars" (1973, 1974, 1975, 1976, 1977, 1979, 1980, 1981, 1984). Karpov's tournament successes include over 160 first-place finishes. He had a peak Elo rating of 2780, and his 102 total months at world number one is the third-longest of all time, behind Magnus Carlsen and Garry Kasparov, since the inception of the FIDE ranking list in 1970. Karpov is also an elected Member of the Duma in Russia. Since 2006, he has chaired the Commission for Ecological Safety and Environmental Protection of the Civic Chamber of the Russian Federation. And since 2007, he has been a member of the Public Council under the Ministry of Defence. Early life Karpov was born on May 23, 1951, in Zlatoust, in the Urals region of the former Soviet Union, and learned to play chess at the age of four. His early rise in chess was swift, as he became a candidate master by age 11. At 12, he was accepted into Mikhail Botvinnik's prestigious chess school, though Botvinnik made the following remark about the young Karpov: "The boy does not have a clue about chess, and there's no future at all for him in this profession." Karpov acknowledged that his understanding of chess theory was very confused at that time, and later wrote that the homework Botvinnik assigned greatly helped him, since it required that he consult chess books and work diligently. Karpov improved so quickly under Botvinnik's tutelage that he became the youngest Soviet master in history at fifteen in 1966; this tied the record established by Boris Spassky in 1952. Career Young master Karpov finished first in his first international tournament in Třinec several months later, ahead of Viktor Kupreichik. In 1967, he won the annual Niemeyer Tournament at Groningen. Karpov won a gold medal for academic excellence in high school, and entered Moscow State University in 1968 to study mathematics. He later transferred to Leningrad State University, eventually graduating from there in economics. One reason for the transfer was to be closer to his coach, grandmaster Semyon Furman, who lived in Leningrad. In his writings, Karpov credits Furman as a major influence on his development as a world-class player. In 1969, Karpov became the first Soviet player since Spassky (1955) to win the World Junior Championship, scoring an undefeated 10/11 in the final A at Stockholm. This victory earned him the international master title. In 1970, he tied for fourth and fifth places with Pal Benko at an international tournament in Caracas, Venezuela, and earned the international grandmaster title. FIDE awarded him the title during its 41st congress, held during the Chess Olympiad in Siegen, West Germany in September 1970. Grandmaster He won the 1971 Alekhine Memorial tournament in Moscow (jointly with Leonid Stein), ahead of a star-studded field, for his first significant adult victory. His Elo rating shot from 2540 in 1971 to 2660 in 1973, when he shared second place in the USSR Chess Championship. Candidate Karpov's world junior championship qualified him for one of the two Interzonals, a stage in the 1975 World Championship cycle to choose the challenger to play world champion Bobby Fischer. He finished equal first in the Leningrad Interzonal, qualifying for the 1974 Candidates Matches. Karpov defeated Lev Polugaevsky by the score of +3=5 in the first Candidates' match, earning the right to face former champion Boris Spassky in the semifinal round. Karpov was on record saying that he believed Spassky would easily beat him and win the Candidates' cycle to face Fischer, and that he (Karpov) would win the following Candidates' cycle in 1977. Spassky won the first game as Black in good style, but tenacious, aggressive play from Karpov secured him overall victory by +4−1=6. The Candidates' final was played in Moscow with Victor Korchnoi. Karpov took an early lead, winning the second game against the Sicilian Dragon, then scoring another victory in the sixth game. Following ten consecutive draws, Korchnoi threw away a winning position in the seventeenth game to give Karpov a 3–0 lead. In game 19, Korchnoi succeeded in winning a long endgame, then notched a speedy victory after a blunder by Karpov two games later. Three more draws, the last agreed by Karpov in a clearly better position, closed the match, as he thus prevailed +3−2=19, moving on to challenge Fischer for the world title. Match with Fischer in 1975 Though a world championship match between Karpov and Fischer was highly anticipated, those hopes were never realised. Fischer not only insisted that the match be the first to ten wins (draws not counting), but also that the champion retain the crown if the score was tied 9–9. FIDE, the International Chess Federation, refused to allow this proviso, and gave both players a deadline of April 1, 1975, to agree to play the match under the FIDE-approved rules. When Fischer did not agree, FIDE President Max Euwe declared on April 3, 1975, that Fischer had forfeited his title and Karpov was the new World Champion. Karpov later attempted to set up another match with Fischer, but the negotiations fell through. This thrust the young Karpov into the role of World Champion without having faced the reigning champion. Garry Kasparov argued that Karpov would have had good chances because he had beaten Spassky convincingly and was a new breed of tough professional, and indeed had higher quality games, while Fischer had been inactive for three years. This view is echoed by Karpov himself. Spassky thought that Fischer would have won in 1975, but Karpov would have qualified again and beaten Fischer in 1978. Karpov is on record saying that if he had had the opportunity to play Fischer for the crown in his twenties, he could have been a much better player as a result. World champion Determined to prove himself a legitimate champion, Karpov participated in nearly every major tournament for the next ten years. He convincingly won the Milan tournament in 1975, and captured his first of three Soviet titles in 1976. He created a phenomenal streak of tournament wins against the strongest players in the world. Karpov held the record for most consecutive tournament victories (9) until it was shattered by Garry Kasparov (14). As a result, most chess professionals soon agreed that Karpov was a legitimate world champion. In 1978, Karpov's first title defence was against Viktor Korchnoi, the opponent he had defeated in the 1973–75 Candidates' cycle; the match was played at Baguio, Philippines, with the winner needing six victories. As in 1974, Karpov took an early lead, winning the eighth game after seven draws to open the match. When the score was +5−2=20 in Karpov's favour, Korchnoi staged a comeback, and won three of the next four games to draw level with Karpov. Karpov then won the very next game to retain the title (+6−5=21). Three years later, Korchnoi reemerged as the Candidates' winner against German finalist Robert Hübner to challenge Karpov in Merano, Italy. Karpov handily won this match, 11–7 (+6−2=10), in what is remembered as the "Massacre in Merano". Karpov's tournament career reached a peak at the Montreal "Tournament of Stars" tournament in 1979, where he finished joint first (+7−1=10) with Mikhail Tal ahead of a field of strong grandmasters completed by Jan Timman, Ljubomir Ljubojević, Boris Spassky, Vlastimil Hort, Lajos Portisch, Hübner, Bent Larsen and Lubomir Kavalek. He dominated Las Palmas in 1977 with 13½/15. He also won the prestigious Bugojno tournament in 1978 (shared), 1980 and 1986, the Linares tournament in 1981 (shared with Larry Christiansen) and 1994, the Tilburg tournament in 1977, 1979, 1980, 1982, and 1983, and the Soviet Championship in 1976, 1983, and 1988. Karpov represented the Soviet Union at six Chess Olympiads, in all of which the USSR won the team gold medal. He played as the first reserve at Skopje 1972, winning the board prize with 13/15. At Nice 1974, he advanced to board one and again won the board prize with 12/14. At La Valletta 1980, he was again board one and scored 9/12. At Lucerne 1982, he scored 6½/8 on board one. At Dubai 1986, he scored 6/9 on board two. His last was Thessaloniki 1988, where on board two he scored 8/10. In Olympiad play, Karpov lost only two games out of 68 played. To illustrate Karpov's dominance over his peers as champion, his score was +11−2=20 versus Spassky, +5=12 versus Robert Hübner, +6−1=16 versus Ulf Andersson, +3−1=10 versus Vasily Smyslov, +1=16 versus Mikhail Tal, and +10−2=13 versus Ljubomir Ljubojević. Rivalry with Kasparov Karpov had cemented his position as the world's best player and world champion by the time Garry Kasparov arrived on the scene. In their first match, the World Chess Championship 1984 in Moscow, the first player to win six games would win the match. Karpov built a 4–0 lead after nine games. The next 17 games were drawn, setting a record for world title matches, and it took Karpov until game 27 to gain his fifth win. In game 31, Karpov had a winning position but failed to take advantage and settled for a draw. He lost the next game, after which 14 more draws ensued. Karpov held a solidly winning position in Game 41, but again blundered and had to settle for a draw. After Kasparov won games 47 and 48, FIDE President Florencio Campomanes unilaterally terminated the match, citing the players' health. Karpov is said to have lost 10 kg over the course of the match. The match had lasted an unprecedented five months, with five wins for Karpov, three for Kasparov, and 40 draws. A rematch was set for later in 1985, also in Moscow. The events of the so-called Marathon Match forced FIDE to return to the previous format, with a match limited to 24 games (with Karpov remaining champion if the match finished 12–12). Karpov needed to win the final game to draw the match and retain his title, but lost, surrendering the title to his opponent. The final score was 13–11 (+3−5=16) in favour of Kasparov. Karpov remained a formidable opponent (and the world No. 2) until the mid-1990s. He fought Kasparov in three more world championship matches in 1986 (held in London and Leningrad), 1987 (in Seville), and 1990 (in New York City and Lyon). All three matches were extremely close: the scores were 11½–12½ (+4−5=15), 12–12 (+4−4=16), and 11½–12½ (+3−4=17). In all three matches, Karpov had winning chances up to the last games. In particular, the 1987 Seville match featured an astonishing blunder by Kasparov in the 23rd game. In the final game, needing only a draw to win the title, Karpov cracked under time pressure at the end of the first session of play, missed a variation leading to an almost forced draw, and allowed Kasparov to adjourn the game with an extra pawn. After a further mistake in the second session, Karpov was slowly ground down and resigned on move 64, ending the match and allowing Kasparov to keep the title. In their five world championship matches, Karpov scored 19 wins, 21 losses, and 104 draws in 144 games.. Overall, Karpov played five matches against Kasparov for the title from 1984 to 1990 without ever defeating him in a match. FIDE champion again (1993–1999) In 1992, Karpov lost a Candidates Match against Nigel Short. But in the World Chess Championship 1993, Karpov reacquired the FIDE World Champion title when Kasparov and Short split from FIDE. Karpov defeated Timman – the loser of the Candidates' final against Short. The next major meeting of Kasparov and Karpov was the 1994 Linares chess tournament. The field, in eventual finishing order, was Karpov, Kasparov, Shirov, Bareev, Kramnik, Lautier, Anand, Kamsky, Topalov, Ivanchuk, Gelfand, Illescas, Judit Polgár, and Beliavsky; with an average Elo rating of 2685, the highest ever at that time. Impressed by the strength of the tournament, Kasparov had said several days before the tournament that the winner could rightly be called the world champion of tournaments. Perhaps spurred on by this comment, Karpov played the best tournament of his life. He was undefeated and earned 11 points out of 13 (the best world-class tournament winning percentage since Alekhine won San Remo in 1930), finishing 2½ points ahead of second-place Kasparov and Shirov. Many of his wins were spectacular (in particular, his win over Topalov is considered possibly the finest of his career). This performance against the best players in the world put his Elo rating tournament performance at 2985, the highest performance rating of any player in history up until 2009, when Magnus Carlsen won the category XXI Pearl Spring chess tournament with a performance of 3002. Chess statistician Jeff Sonas considers Karpov's Linares performance the best tournament result in history. Karpov defended his FIDE title against the rising star Gata Kamsky (+6−3=9) in 1996. In 1998, FIDE largely scrapped the old system of Candidates' Matches, instead having a large knockout event in which a large number of players contested short matches against each other over just a few weeks. In the first of these events, the FIDE World Chess Championship 1998, champion Karpov was seeded straight into the final, defeating Viswanathan Anand (+2−2=2, rapid tiebreak 2–0). In the subsequent cycle, the format was changed, with the champion having to qualify. Karpov refused to defend his title, and ceased to be FIDE World Champion after the FIDE World Chess Championship 1999. Towards retirement Karpov's classical tournament play has been seriously limited since 1997, since he prefers to be more involved in Russian politics. He had been a member of the Supreme Soviet Commission for Foreign Affairs and the president of the Soviet Peace Fund before the Soviet Union dissolved. In addition, he has been involved in several disputes with FIDE. In the September 2009 FIDE rating list, he dropped out of the world's Top 100 for the first time. Karpov usually limits his play to exhibition events, and has revamped his style to specialize in rapid chess. In 2002, he won a match against Kasparov, defeating him in a rapid time control match 2½–1½. In 2006, he tied for first with Kasparov in a blitz tournament, ahead of Korchnoi and Judit Polgár. Karpov and Kasparov played a mixed 12-game match from September 21–24, 2009, in Valencia, Spain. It consisted of four rapid (or semi-rapid) and eight blitz games and took place exactly 25 years after the two players' legendary encounter at the World Chess Championship 1984. Kasparov won the match 9–3. Karpov played a match against Yasser Seirawan in 2012 in St. Louis, Missouri, an important center of the North American chess scene, winning 8–6 (+5−3=6). In November 2012, he won the Cap d'Agde rapid tournament that bears his name (Anatoly Karpov Trophy), beating Vasyl Ivanchuk (ranked 9th in the October 2012 FIDE world rankings) in the final. Personal life after retirement In 2003, Karpov opened his first American chess school in Lindsborg, Kansas. Karpov has been a member of the sixth, seventh and eighth Russian State Dumas. Since 2005, he has been a member of the Public Chamber of Russia. He has involved himself in several humanitarian causes, such as advocating the use of iodised salt. On December 17, 2012, Karpov supported the law in the Russian Parliament banning adoption of Russian orphans by U.S. citizens. Karpov expressed support of the annexation of Crimea by the Russian Federation, and accused Europe of trying to demonize Putin. In August 2019, Maxim Dlugy said that Karpov had been waiting since March for the approval of a non-immigrant visa to the United States, despite frequently visiting the country since 1972. Karpov had been scheduled to teach a summer camp at the Chess Max Academy. Dlugy said that Karpov had been questioned at the US embassy in Moscow about whether he planned to communicate with American politicians. Karpov was among the Russian State Duma members placed under sanctions by the EU during the 2021–2022 Russo-Ukrainian crisis. Candidate for FIDE presidency In March 2010 Karpov announced that he would be a candidate for the presidency of FIDE. The election took place in September 2010 at the 39th Chess Olympiad. In May, a fund-raising event took place in New York with the participation of Kasparov and of Magnus Carlsen, both of whom supported his bid and campaigned for him. Nigel Short also supported Karpov's candidacy. On September 29, 2010, Kirsan Ilyumzhinov was reelected as president of FIDE, 95 votes to 55. Style Karpov's "boa constrictor" playing style is solidly positional, taking minimal risks but reacting mercilessly to the slightest error by his opponent. As a result, he is often compared to José Raúl Capablanca, the third world champion. Karpov himself describes his style as follows:Let us say the game may be continued in two ways: one of them is a beautiful tactical blow that gives rise to variations that don't yield to precise calculations; the other is clear positional pressure that leads to an endgame with microscopic chances of victory.... I would choose [the latter] without thinking twice. If the opponent offers keen play I don't object; but in such cases I get less satisfaction, even if I win, than from a game conducted according to all the rules of strategy with its ruthless logic. Notable games Viktor Korchnoi vs. Anatoly Karpov, Moscow 1973 Karpov sacrifices a pawn for a strong center and attack. Anatoly Karpov vs. Gyula Sax, Linares 1983 Karpov sacrifices for an attack that wins the game 20 moves later, after another spectacular sacrifice from Karpov and counter-sacrifice from Sax. It won the tournament's first . This was not the first time Karpov used the sharp Keres Attack (6.g4) – see his win in Anatoly Karpov vs. Vlastimil Hort, Alekhine Memorial Tournament, Moscow 1971. Anatoly Karpov vs. Veselin Topalov, Dos Hermanas 1994 This game features a sham sacrifice of two pieces, which Karpov regains with a variation, culminating in the win of an exchange with a technically won endgame. Hobbies Karpov's extensive stamp collection of Belgian philately and Belgian Congo stamps and postal history covering mail from 1742 through 1980 was sold by David Feldman's auction company between December 2011 and 2012. He is also known to have a large chess stamp and chess book collections. His private chess library consists of 9000 books. Honours and awards Order of Merit for the Fatherland, 3rd class (2001) – for outstanding contribution to the implementation of charitable programmes, the strengthening of peace and friendship between the peoples Order of Friendship (2011) – for his great contribution to strengthening peace and friendship between peoples and productive social activities Order of Lenin (1981) Order of the Red Banner of Labour (1978) Order of Merit, 2nd class (Ukraine) (November 13, 2006) – for his contribution to the victims of the Chernobyl disaster Order of Holy Prince Daniel of Moscow, 2nd class (1996) Order of St. Sergius of Radonezh, 2nd class (2001) Medal "For outstanding contribution to the Collector business in Russia" Honorary member of the Soviet Philately Society (1979) Diploma of the State Duma of the Russian Federation No. 1 Order "For outstanding achievements in sport" (Republic of Cuba) Medal of Tsiolkovsky Cosmonautics Federation of Russia Medal "For Strengthening the penal system", 1st and 2nd class Breastplate of the 1st degree of the Interior Ministry International Association of Chess Press, 9 times voted the best chess player of the year and awarded the "Chess Oscar" Order of Saint Nestor the Chronicler, 1st class Asteroid 90414 Karpov is named after Karpov Anatoly Karpov International Chess Tournament, an annual round-robin tournament held in his honour in Poikovsky, Khanty-Mansi Autonomous Okrug, Russia since 2000 Books Karpov has authored or co-authored several books, most of which have been translated into English. Karpov, A.E. Ninth vertical. 1978. Moscow: Molodaya Gvardia. (also a 1992 Simon & Schuster edition) References Further reading Fine, Rueben (1983). The World's Great Chess Games. Dover. . Hurst, Sarah (2002). Curse of Kirsan: Adventures in the Chess Underworld. Russell Enterprises. . Karpov, Anatoly (2003). Anatoly Karpov's Best Games. Batsford. . Winter, Edward G., editor (1981).World Chess Champions. Pergamon Press. . External links Karpov's official homepage Edward Winter, "Books about Korchnoi and Karpov", Chess Notes 25 minute video interview with Karpov, OnlineChessLessons.NET, June 19, 2012 "Anatoly Karpov tells all" (2015 interview by Sport Express, translated by ChessBase): part 1, part 2, part 3, part 4 1951 births Living people People from Zlatoust World chess champions Chess grandmasters World Junior Chess Champions Chess Olympiad competitors Russian chess players Soviet chess players Saint Petersburg State University alumni Russian chess writers Soviet chess writers Soviet male writers 20th-century male writers Communist Party of the Soviet Union members Members of the Civic Chamber of the Russian Federation Recipients of the Order "For Merit to the Fatherland", 3rd class Recipients of the Order of Lenin Recipients of the Order of Merit (Ukraine), 1st class Recipients of the Order of Holy Prince Daniel of Moscow Book and manuscript collectors Russian philatelists Russian sportsperson-politicians Sixth convocation members of the State Duma (Russian Federation) Seventh convocation members of the State Duma (Russian Federation) Eighth convocation members of the State Duma (Russian Federation)

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1030

https://en.wikipedia.org/wiki/Austrian%20School

Austrian School

The Austrian School is a heterodox school of economic thought that is based on methodological individualism, the concept that social phenomena result exclusively from the motivations and actions of individuals. The Austrian School originated in late-19th and early-20th-century Vienna with the work of Carl Menger, Eugen Böhm von Bawerk, Friedrich von Wieser, and others. It was methodologically opposed to the younger Historical School (based in Germany), in a dispute known as Methodenstreit, or methodology struggle. Current-day economists working in this tradition are located in many different countries, but their work is still referred to as Austrian economics. Among the theoretical contributions of the early years of the Austrian School are the subjective theory of value, marginalism in price theory and the formulation of the economic calculation problem, each of which has become an accepted part of mainstream economics. Since the mid-20th century, mainstream economists have been critical of the modern-day Austrian School and consider its rejection of mathematical modelling, econometrics and macroeconomic analysis to be outside mainstream economics, or "heterodox". In the 1970s, the Austrian School attracted some renewed interest after Friedrich Hayek shared the 1974 Nobel Memorial Prize in Economic Sciences with Gunnar Myrdal. History Etymology The Austrian School owes its name to members of the German historical school of economics, who argued against the Austrians during the late-19th century Methodenstreit ("methodology struggle"), in which the Austrians defended the role of theory in economics as distinct from the study or compilation of historical circumstance. In 1883, Menger published Investigations into the Method of the Social Sciences with Special Reference to Economics, which attacked the methods of the historical school. Gustav von Schmoller, a leader of the historical school, responded with an unfavorable review, coining the term "Austrian School" in an attempt to characterize the school as outcast and provincial. The label endured and was adopted by the adherents themselves. First wave The school originated in Vienna in the Austrian Empire. Carl Menger's 1871 book Principles of Economics is generally considered the founding of the Austrian School. The book was one of the first modern treatises to advance the theory of marginal utility. The Austrian School was one of three founding currents of the marginalist revolution of the 1870s, with its major contribution being the introduction of the subjectivist approach in economics. Despite such claim, John Stuart Mill had used value in use in this sense in 1848 in Principles of Political Economy, where he wrote: "Value in use, or as Mr. De Quincey calls it, teleologic value, is the extreme limit of value in exchange. The exchange value of a thing may fall short, to any amount, of its value in use; but that it can ever exceed the value in use, implies a contradiction; it supposes that persons will give, to possess a thing, more than the utmost value which they themselves put upon it as a means of gratifying their inclinations." While marginalism was generally influential, there was also a more specific school that began to coalesce around Menger's work, which came to be known as the "Psychological School", "Vienna School", or "Austrian School". Menger's contributions to economic theory were closely followed by those of Eugen Böhm von Bawerk and Friedrich von Wieser. These three economists became what is known as the "first wave" of the Austrian School. Böhm-Bawerk wrote extensive critiques of Karl Marx in the 1880s and 1890s as was part of the Austrians' participation in the late 19th-century Methodenstreit, during which they attacked the Hegelian doctrines of the historical school. Early 20th century Frank Albert Fetter (1863–1949) was a leader in the United States of Austrian thought. He obtained his PhD in 1894 from the University of Halle and then was made Professor of Political Economy and Finance at Cornell in 1901. Several important Austrian economists trained at the University of Vienna in the 1920s and later participated in private seminars held by Ludwig von Mises. These included Gottfried Haberler, Friedrich Hayek, Fritz Machlup, Karl Menger (son of Carl Menger), Oskar Morgenstern, Paul Rosenstein-Rodan, Abraham Wald, and Michael A. Heilperin, among others, as well as the sociologist Alfred Schütz. Later 20th century By the mid-1930s, most economists had embraced what they considered the important contributions of the early Austrians. Fritz Machlup quoted Hayek's statement that "the greatest success of a school is that it stops existing because its fundamental teachings have become parts of the general body of commonly accepted thought". Sometime during the middle of the 20th century, Austrian economics became disregarded or derided by mainstream economists because it rejected model building and mathematical and statistical methods in the study of economics. Mises' student Israel Kirzner recalled that in 1954, when Kirzner was pursuing his PhD, there was no separate Austrian School as such. When Kirzner was deciding which graduate school to attend, Mises had advised him to accept an offer of admission at Johns Hopkins because it was a prestigious university and Fritz Machlup taught there. After the 1940s, Austrian economics can be divided into two schools of economic thought and the school "split" to some degree in the late 20th century. One camp of Austrians, exemplified by Mises, regards neoclassical methodology to be irredeemably flawed; the other camp, exemplified by Friedrich Hayek, accepts a large part of neoclassical methodology and is more accepting of government intervention in the economy. Henry Hazlitt wrote economics columns and editorials for a number of publications and wrote many books on the topic of Austrian economics from the 1930s to the 1980s. Hazlitt's thinking was influenced by Mises. His book Economics in One Lesson (1946) sold over a million copies and he is also known for The Failure of the "New Economics" (1959), a line-by-line critique of John Maynard Keynes's General Theory. The reputation of the Austrian School rose in the late 20th century due in part to the work of Israel Kirzner and Ludwig Lachmann at New York University and to renewed public awareness of the work of Hayek after he won the 1974 Nobel Memorial Prize in Economic Sciences. Hayek's work was influential in the revival of laissez-faire thought in the 20th century. Split among contemporary Austrians Economist Leland Yeager discussed the late 20th-century rift and referred to a discussion written by Murray Rothbard, Hans-Hermann Hoppe, Joseph Salerno and others in which they attack and disparage Hayek. Yeager stated: "To try to drive a wedge between Mises and Hayek on [the role of knowledge in economic calculation], especially to the disparagement of Hayek, is unfair to these two great men, unfaithful to the history of economic thought". He went on to call the rift subversive to economic analysis and the historical understanding of the fall of Eastern European communism. In a 1999 book published by the Ludwig von Mises Institute, Hoppe asserted that Rothbard was the leader of the "mainstream within Austrian Economics" and contrasted Rothbard with Nobel Laureate Friedrich Hayek, whom he identified as a British empiricist and an opponent of the thought of Mises and Rothbard. Hoppe acknowledged that Hayek was the most prominent Austrian economist within academia, but stated that Hayek was an opponent of the Austrian tradition which led from Carl Menger and Böhm-Bawerk through Mises to Rothbard. Austrian economist Walter Block says that the Austrian School can be distinguished from other schools of economic thought through two categories—economic theory and political theory. According to Block, while Hayek can be considered an Austrian economist, his views on political theory clash with the libertarian political theory which Block sees as an integral part of the Austrian School. Both criticism from Hoppe and Block to Hayek apply to Carl Menger, the founder of the Austrian School. Hoppe emphasizes that Hayek, which for him is from the English empirical tradition, is an opponent of the supposed rationalist tradition of the Austrian School; Menger made strong critiques to rationalism in his works in similar vein as Hayek's. He emphasized the idea that there are several institutions which were not deliberately created, have a kind of "superior wisdom" and serve important functions to society. He also talked about Burke and the English tradition to sustain these positions. When saying that the libertarian political theory is an integral part of the Austrian School and supposing Hayek is not a libertarian, Block excludes Menger from the Austrian School too since Menger seems to defend broader state activity than Hayek—for example, progressive taxation and extensive labour legislation. Economists of the Hayekian view are affiliated with the Cato Institute, George Mason University (GMU) and New York University, among other institutions. They include Peter Boettke, Roger Garrison, Steven Horwitz, Peter Leeson and George Reisman. Economists of the Mises–Rothbard view include Walter Block, Hans-Hermann Hoppe, Jesús Huerta de Soto and Robert P. Murphy, each of whom is associated with the Mises Institute and some of them also with academic institutions. According to Murphy, a "truce between (for lack of better terms) the GMU Austro-libertarians and the Auburn Austro-libertarians" was signed around 2011. Influence Many theories developed by "first wave" Austrian economists have long been absorbed into mainstream economics. These include Carl Menger's theories on marginal utility, Friedrich von Wieser's theories on opportunity cost and Eugen Böhm von Bawerk's theories on time preference, as well as Menger and Böhm-Bawerk's criticisms of Marxian economics. Former American Federal Reserve Chairman Alan Greenspan said that the founders of the Austrian School "reached far into the future from when most of them practiced and have had a profound and, in my judgment, probably an irreversible effect on how most mainstream economists think in this country". In 1987, Nobel Laureate James M. Buchanan told an interviewer: "I have no objections to being called an Austrian. Hayek and Mises might consider me an Austrian but, surely some of the others would not". Currently, universities with a significant Austrian presence are George Mason University, New York University, Grove City College, Loyola University New Orleans and Auburn University in the United States; King Juan Carlos University in Spain; and Universidad Francisco Marroquín in Guatemala. Austrian economic ideas are also promoted by privately funded organizations such as the Mises Institute and the Cato Institute. Methodology The Austrian School theorizes that the subjective choices of individuals including individual knowledge, time, expectation and other subjective factors cause all economic phenomena. Austrians seek to understand the economy by examining the social ramifications of individual choice, an approach called methodological individualism. It differs from other schools of economic thought, which have focused on aggregate variables, equilibrium analysis and societal groups rather than individuals. In the 20th and 21st centuries, economists with a methodological lineage to the early Austrian School developed many diverse approaches and theoretical orientations. Ludwig von Mises organized his version of the subjectivist approach, which he called "praxeology", in a book published in English as Human Action in 1949. In it, Mises stated that praxeology could be used to deduce a priori theoretical economic truths and that deductive economic thought experiments could yield conclusions which follow irrefutably from the underlying assumptions. He wrote that conclusions could not be inferred from empirical observation or statistical analysis and argued against the use of probabilities in economic models. Since Mises' time, some Austrian thinkers have accepted his praxeological approach while others have adopted alternative methodologies. For example, Fritz Machlup, Friedrich Hayek and others did not take Mises' strong a priori approach to economics. Ludwig Lachmann, a radical subjectivist, also largely rejected Mises' formulation of Praxeology in favor of the verstehende Methode ("interpretive method") articulated by Max Weber. In the 20th century, various Austrians incorporated models and mathematics into their analysis. Austrian economist Steven Horwitz argued in 2000 that Austrian methodology is consistent with macroeconomics and that Austrian macroeconomics can be expressed in terms of microeconomic foundations. Austrian economist Roger Garrison writes that Austrian macroeconomic theory can be correctly expressed in terms of diagrammatic models. In 1944, Austrian economist Oskar Morgenstern presented a rigorous schematization of an ordinal utility function (the Von Neumann–Morgenstern utility theorem) in Theory of Games and Economic Behavior. Fundamental tenets In 1981, Fritz Machlup listed the typical views of Austrian economic thinking as such: Methodological individualism: in the explanation of economic phenomena, we have to go back to the actions (or inaction) of individuals; groups or "collectives" cannot act except through the actions of individual members. Groups don't think; people think. Methodological subjectivism: in the explanation of economic phenomena, we have to go back to judgments and choices made by individuals on the basis of whatever knowledge they have or believe to have and whatever expectations they entertain regarding external developments and especially the perceived consequences of their own intended actions. Tastes and preferences: subjective valuations of goods and services determine the demand for them so that their prices are influenced by (actual and potential) consumers. Opportunity costs: the costs with which producers and other economic actors calculate reflect the alternative opportunities that must be foregone; as productive services are employed for one purpose, all alternative uses have to be sacrificed. Marginalism: in all economic designs, the values, costs, revenues, productivity and so on are determined by the significance of the last unit added to or subtracted from the total. Time structure of production and consumption: decisions to save reflect "time preferences" regarding consumption in the immediate, distant, or indefinite future and investments are made in view of larger outputs expected to be obtained if more time-taking production processes are undertaken. He included two additional tenets held by the Mises branch of Austrian economics: Consumer sovereignty: the influence consumers have on the effective demand for goods and services and through the prices which result in free competitive markets, on the production plans of producers and investors, is not merely a hard fact but also an important objective, attainable only by complete avoidance of governmental interference with the markets and of restrictions on the freedom of sellers and buyers to follow their own judgment regarding quantities, qualities and prices of products and services. Political individualism: only when individuals are given full economic freedom will it be possible to secure political and moral freedom. Restrictions on economic freedom lead, sooner or later, to an extension of the coercive activities of the state into the political domain, undermining and eventually destroying the essential individual liberties which the capitalistic societies were able to attain in the 19th century. Contributions to economic thought Opportunity cost The opportunity cost doctrine was first explicitly formulated by the Austrian economist Friedrich von Wieser in the late 19th century. Opportunity cost is the cost of any activity measured in terms of the value of the next best alternative foregone (that is not chosen). It is the sacrifice related to the second best choice available to someone, or group, who has picked among several mutually exclusive choices. Opportunity cost is a key concept in mainstream economics and has been described as expressing "the basic relationship between scarcity and choice". The notion of opportunity cost plays a crucial part in ensuring that resources are used efficiently. Capital and interest The Austrian theory of capital and interest was first developed by Eugen Böhm von Bawerk. He stated that interest rates and profits are determined by two factors, namely supply and demand in the market for final goods and time preference. Böhm-Bawerk's theory equates capital intensity with the degree of roundaboutness of production processes. Böhm-Bawerk also argued that the law of marginal utility necessarily implies the classical law of costs. Some Austrian economists therefore entirely reject the notion that interest rates are affected by liquidity preference. Inflation In Mises's definition, inflation is an increase in the supply of money: Hayek pointed out that inflationary stimulation exploits the lag between an increase in money supply and the consequent increase in the prices of goods and services: Economic calculation problem The economic calculation problem refers to a criticism of planned economies which was first stated by Max Weber in 1920. Mises subsequently discussed Weber's idea with his student Friedrich Hayek, who developed it in various works including The Road to Serfdom. What the calculation problem essentially states is that without price signals, the factors of production cannot be allocated in the most efficient way possible, rendering planned economies inefficacious. Austrian theory emphasizes the organizing power of markets. Hayek stated that market prices reflect information, the totality of which is not known to any single individual, which determines the allocation of resources in an economy. Because socialist systems lack the individual incentives and price discovery processes by which individuals act on their personal information, Hayek argued that socialist economic planners lack all of the knowledge required to make optimal decisions. Those who agree with this criticism view it as a refutation of socialism, showing that socialism is not a viable or sustainable form of economic organization. The debate rose to prominence in the 1920s and 1930s and that specific period of the debate has come to be known by historians of economic thought as the socialist calculation debate. Mises argued in a 1920 essay "Economic Calculation in the Socialist Commonwealth" that the pricing systems in socialist economies were necessarily deficient because if the government owned the means of production, then no prices could be obtained for capital goods as they were merely internal transfers of goods in a socialist system and not "objects of exchange", unlike final goods. Therefore, they were unpriced and hence the system would be necessarily inefficient since the central planners would not know how to allocate the available resources efficiently. This led him to write "that rational economic activity is impossible in a socialist commonwealth". Business cycles The Austrian theory of the business cycle (ABCT) focuses on banks' issuance of credit as the cause of economic fluctuations. Although later elaborated by Hayek and others, the theory was first set forth by Mises, who posited that fractional reserve banks extend credit at artificially low interest rates, causing businesses to invest in relatively roundabout production processes which leads to an artificial "boom". Mises stated that this artificial "boom" then led to a misallocation of resources which he called "malinvestment" - which eventually must end in a "bust". Mises surmised how government manipulation of money and credit in the banking system throws savings and investment out of balance, resulting in misdirected investment projects that are eventually found to be unsustainable, at which point the economy has to rebalance itself through a period of corrective recession. Austrian economist Fritz Machlup summarized the Austrian view by stating, "monetary factors cause the cycle but real phenomena constitute it." For Austrians, the only prudent strategy for government is to leave money and the financial system to the free market's competitive forces to eradicate the business cycle's inflationary booms and recessionary busts, allowing markets to keep people's saving and investment decisions in place for well-coordinated economic stability and growth. A Keynesian would suggest government intervention during a recession to inject spending into the economy when people are not. However, the heart of Austrian macroeconomic theory states the government "fine tuning" through expansions and contractions in the money supply orchestrated by the government are actually the cause of business cycles because of the differing impact of the resulting interest rate changes on different stages in the structure of production. Austrian economist Thomas Woods further supports this view by arguing it is not consumption, but rather production that should be emphasized. A country cannot become rich by consuming, and therefore, by using up all their resources. Instead, production is what enables consumption as a possibility in the first place, since a producer would be working for nothing, if not for the desire to consume. Central banks According to Ludwig von Mises, central banks enable the commercial banks to fund loans at artificially low interest rates, thereby inducing an unsustainable expansion of bank credit and impeding any subsequent contraction and argued for a gold standard to constrain growth in fiduciary media. Friedrich Hayek took a different perspective not focusing on gold but focusing on regulation of the banking sector via strong central banking. Criticism General Mainstream economists generally reject modern-day Austrian economics, and argue that modern-day Austrian economists are excessively averse to the use of mathematics and statistics in economics. Austrian opposition to mathematization extends to economic theorizing only, as they argue that human behavior is too variable for overarching mathematical models to hold true across time and context. Austrians do, however, support analyzing revealed preference via mathematization to aid business and finance. Economist Paul Krugman has stated that they are unaware of holes in their own thinking because Austrians do not use "explicit models". Economist Benjamin Klein has criticized the economic methodological work of Austrian economist Israel M. Kirzner. While praising Kirzner for highlighting shortcomings in traditional methodology, Klein argued that Kirzner did not provide a viable alternative for economic methodology. Economist Tyler Cowen has written that Kirzner's theory of entrepreneurship can ultimately be reduced to a neoclassical search model and is thus not in the radical subjectivist tradition of Austrian praxeology. Cowen states that Kirzner's entrepreneurs can be modeled in mainstream terms of search. Economist Jeffrey Sachs argues that among developed countries, those with high rates of taxation and high social welfare spending perform better on most measures of economic performance compared to countries with low rates of taxation and low social outlays. He concludes that Friedrich Hayek was wrong to argue that high levels of government spending harms an economy and "a generous social-welfare state is not a road to serfdom but rather to fairness, economic equality and international competitiveness". Economist Bryan Caplan has noted that Mises has been criticized for overstating the strength of his case in describing socialism as "impossible" rather than as something that would need to establish non-market institutions to deal with the inefficiency. Methodology Critics generally argue that Austrian economics lacks scientific rigor and rejects scientific methods and the use of empirical data in modelling economic behavior. Some economists describe Austrian methodology as being a priori or non-empirical. Economist Mark Blaug has criticized over-reliance on methodological individualism, arguing it would rule out all macroeconomic propositions that cannot be reduced to microeconomic ones, and hence reject almost the whole of received macroeconomics. Economist Thomas Mayer has stated that Austrians advocate a rejection of the scientific method which involves the development of empirically falsifiable theories. Furthermore, economists have developed numerous experiments that elicit useful information about individual preferences. Although economist Leland Yeager is sympathetic to Austrian economics, he rejects many favorite views of the Misesian group of Austrians, in particular "the specifics of their business-cycle theory, ultra-subjectivism in value theory and particularly in interest-rate theory, their insistence on unidirectional causality rather than general interdependence, and their fondness for methodological brooding, pointless profundities, and verbal gymnastics". Economist Paul A. Samuelson wrote in 1964 that most economists believe that economic conclusions reached by pure logical deduction are limited and weak. According to Samuelson and Caplan, Mises' deductive methodology also embraced by Murray Rothbard and to a lesser extent by Mises' student Israel Kirzner was not sufficient in and of itself. Business cycle theory Mainstream economic research regarding Austrian business cycle theory finds that it is inconsistent with empirical evidence. Economists such as Gordon Tullock, Milton Friedman and Paul Krugman have said that they regard the theory as incorrect. Austrian economist Ludwig Lachmann noted that the Austrian theory was rejected during the 1930s: Theoretical objections Some economists argue that Austrian business cycle theory requires bankers and investors to exhibit a kind of irrationality because the Austrian theory posits that investors will be fooled repeatedly (by temporarily low interest rates) into making unprofitable investment decisions. Milton Friedman objected to the policy implications of the theory, stating the following in a 1998 interview: Empirical objections Milton Friedman after examining the history of business cycles in the United States wrote that there "appears to be no systematic connection between the size of an expansion and of the succeeding contraction", and that further analysis could cast doubt on business cycle theories which rely on this premise. Referring to Friedman's discussion of the business cycle, Austrian economist Roger Garrison argued that Friedman's empirical findings are "broadly consistent with both Monetarist and Austrian views" and goes on to argue that although Friedman's model "describes the economy's performance at the highest level of aggregation, Austrian theory offers an insightful account of the market process that might underlie those aggregates". See also Carl Menger Chicago school of economics Criticism of the Federal Reserve Eugen von Böhm-Bawerk Friedrich Hayek Hans-Hermann Hoppe Henry Hazlitt Israel Kirzner List of Austrian intellectual traditions List of Austrian School economists Ludwig von Mises New institutional economics Perspectives on capitalism by school of thought School of Salamanca Notes and references Further reading Campagnolo, Gilles, and Christel Vivel. "The foundations of the theory of entrepreneurship in austrian economics–Menger and Böhm-Bawerk on the entrepreneur." Revue de philosophie économique 15.1 (2014): 49–97. online in English Hagemann, Harald, Tamotsu Nishizawa, and Yukihiro Ikeda, eds. Austrian Economics in Transition: From Carl Menger to Friedrich Hayek (Palgrave Macmillan; 2010) 339 pp. online review Holcombe, Randall. The Great Austrian Economists (1999) 273pp. . Littlechild, Stephen, ed. (1990). Austrian economics, 3 v. Edward Elgar. Description and scroll to chapter preview links for v. 1. Papaioannou, Theo. Reading Hayek in the 21st Century: a critical inquiry into his political thought Springer, 2012. Wasserman, Janek. The Marginal Revolutionaries: How Austrian Economists Fought the War of Ideas (2019) except External links Understanding Austrian Economics by Henry Hazlitt Schools of economic thought Libertarian theory

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1051

https://en.wikipedia.org/wiki/Alexis%20Carrel

Alexis Carrel

Alexis Carrel (; 28 June 1873 – 5 November 1944) was a French surgeon and biologist who was awarded the Nobel Prize in Physiology or Medicine in 1912 for pioneering vascular suturing techniques. He invented the first perfusion pump with Charles A. Lindbergh opening the way to organ transplantation. His positive description of a miraculous healing he witnessed during a pilgrimage earned him scorn of some of his colleagues. This prompted him to relocate to the United States, where he lived most of his life. He had a leading role in implementing eugenic policies in Vichy France. A Nobel Prize laureate in 1912, Alexis Carrel was also elected twice, in 1924 and 1927, as an honorary member of the Academy of Sciences of the USSR. Biography Born in Sainte-Foy-lès-Lyon, Rhône, Carrel was raised in a devout Catholic family and was educated by Jesuits, though he had become an agnostic by the time he became a university student. He was a pioneer in transplantology and thoracic surgery. Alexis Carrel was also a member of learned societies in the U.S., Spain, Russia, Sweden, the Netherlands, Belgium, France, Vatican City, Germany, Italy and Greece and received honorary doctorates from Queen's University of Belfast, Princeton University, California, New York, Brown University and Columbia University. In 1902, he was claimed to have witnessed the miraculous cure of Marie Bailly at Lourdes, made famous in part because she named Carrel as a witness of her cure. After the notoriety surrounding the event, Carrel could not obtain a hospital appointment because of the pervasive anticlericalism in the French university system at the time. In 1903, he emigrated to Montreal, Canada, but soon relocated to Chicago, Illinois, to work for Hull Laboratory. While there he collaborated with American physician Charles Claude Guthrie in work on vascular suture and the transplantation of blood vessels and organs as well as the head, and Carrel was awarded the 1912 Nobel Prize in Physiology or Medicine for these efforts. In 1906, he joined the newly formed Rockefeller Institute of Medical Research in New York where he spent the rest of his career. There he did significant work on tissue cultures with pathologist Montrose Thomas Burrows. In the 1930s, Carrel and Charles Lindbergh became close friends not only because of the years they worked together but also because they shared personal, political, and social views. Lindbergh initially sought out Carrel to see if his sister-in-law's heart, damaged by rheumatic fever, could be repaired. When Lindbergh saw the crudeness of Carrel's machinery, he offered to build new equipment for the scientist. Eventually they built the first perfusion pump, an invention instrumental to the development of organ transplantation and open heart surgery. Lindbergh considered Carrel his closest friend, and said he would preserve and promote Carrel's ideals after his death. Due to his close proximity with Jacques Doriot's fascist Parti Populaire Français (PPF) during the 1930s and his role in implementing eugenics policies during Vichy France, he was accused after the Liberation of collaboration, but died before the trial. In his later life he returned to his Catholic roots. In 1939, he met with Trappist monk Alexis Presse on a recommendation. Although Carrel was skeptical about meeting with a priest, Presse ended up having a profound influence on the rest of Carrel's life. In 1942, he said "I believe in the existence of God, in the immortality of the soul, in Revelation and in all the Catholic Church teaches." He summoned Presse to administer the Catholic Sacraments on his death bed in November 1944. For much of his life, Carrel and his wife spent their summers on the , which they owned. After he and Lindbergh became close friends, Carrel persuaded him to also buy a neighboring island, the Ile Illiec, where the Lindberghs often resided in the late 1930s. Contributions to science Vascular suture Carrel was a young surgeon in 1894, when the French president Sadi Carnot was assassinated with a knife. Carnot bled to death due to severing of his portal vein, and surgeons who treated the president felt that the vein could not be successfully reconnected. This left a deep impression on Carrel, and he set about developing new techniques for suturing blood vessels. The technique of "triangulation", using three stay-sutures as traction points in order to minimize damage to the vascular wall during suturing, was inspired by sewing lessons he took from an embroideress and is still used today. Julius Comroe wrote: "Between 1901 and 1910, Alexis Carrel, using experimental animals, performed every feat and developed every technique known to vascular surgery today." He had great success in reconnecting arteries and veins, and performing surgical grafts, and this led to his Nobel Prize in 1912. Wound antisepsis During World War I (1914–1918), Carrel and the English chemist Henry Drysdale Dakin developed the Carrel–Dakin method of treating wounds based on chlorine (Dakin's solution) which, preceding the development of antibiotics, was a major medical advance in the care of traumatic wounds. For this, Carrel was awarded the Légion d'honneur. Carrel also advocated the use of wound debridement (cutting away necrotic or otherwise damaged tissue) and irrigation of wounds. His method of wound irrigation involved flushing the tissues with a high volume of antiseptic fluid so that dirt and other contaminants would be washed away (this is known today as "mechanical irrigation.") The World War I era Rockefeller War Demonstration Hospital (United States Army Auxiliary Hospital No. 1) was created, in part, to promote the Carrel–Dakin method: "The war demonstration hospital of the Rockefeller Institute was planned as a school in which to teach military surgeons the principles of and art of applying the Carrel-Dakin treatment." Organ transplants Carrel co-authored a book with pilot Charles A. Lindbergh, The Culture of Organs, and worked with Lindbergh in the mid-1930s to create the "perfusion pump," which allowed living organs to exist outside the body during surgery. The advance is said to have been a crucial step in the development of open-heart surgery and organ transplants, and to have laid the groundwork for the artificial heart, which became a reality decades later. Some critics of Lindbergh claimed that Carrel overstated Lindbergh's role to gain media attention, but other sources say Lindbergh played an important role in developing the device. Both Lindbergh and Carrel appeared on the cover of Time magazine on 13 June 1938. Cellular senescence Carrel was also interested in the phenomenon of senescence, or aging. He claimed that all cells continued to grow indefinitely, and this became a dominant view in the early 20th century. Carrel started an experiment on 17 January 1912, where he placed tissue cultured from an embryonic chicken heart in a stoppered Pyrex flask of his own design. He maintained the living culture for over 20 years with regular supplies of nutrient. This was longer than a chicken's normal lifespan. The experiment, which was conducted at the Rockefeller Institute for Medical Research, attracted considerable popular and scientific attention. Carrel's experiment was never successfully replicated, and in the 1960s Leonard Hayflick and Paul Moorhead proposed that differentiated cells can undergo only a limited number of divisions before dying. This is known as the Hayflick limit, and is now a pillar of biology. It is not certain how Carrel obtained his anomalous results. Leonard Hayflick suggests that the daily feeding of nutrient was continually introducing new living cells to the alleged immortal culture. J. A. Witkowski has argued that, while "immortal" strains of visibly mutated cells have been obtained by other experimenters, a more likely explanation is deliberate introduction of new cells into the culture, possibly without Carrel's knowledge. Honors In 1972, the Swedish Post Office honored Carrel with a stamp that was part of its Nobel stamp series. In 1979, the lunar crater Carrel was named after him as a tribute to his scientific breakthroughs. In February 2002, as part of celebrations of the 100th anniversary of Charles Lindbergh's birth, the Medical University of South Carolina at Charleston established the Lindbergh-Carrel Prize, given to major contributors to "development of perfusion and bioreactor technologies for organ preservation and growth". Michael DeBakey and nine other scientists received the prize, a bronze statuette created for the event by the Italian artist C. Zoli and named "Elisabeth" after Elisabeth Morrow, sister of Lindbergh's wife Anne Morrow, who died from heart disease. It was in fact Lindbergh's disappointment that contemporary medical technology could not provide an artificial heart pump which would allow for heart surgery on her that led to Lindbergh's first contact with Carrel. Alexis Carrel and Lourdes In 1902, Alexis Carrel went from being a skeptic of the visions and miracles reported at Lourdes to being a believer in spiritual cures after experiencing a healing of Marie Bailly that he could not explain. The Catholic journal Le nouvelliste reported that she named him as the prime witness of her cure. Alexis Carrel refused to discount a supernatural explanation and steadfastly reiterated his beliefs, even writing the book The Voyage to Lourdes describing his experience, although it was not published until four years after his death. This was a detriment to his career and reputation among his fellow doctors, and feeling he had no future in academic medicine in France, he emigrated to Canada with the intention of farming and raising cattle. After a brief period, he accepted an appointment at the University of Chicago and, two years later, at the Rockefeller Institute of Medical Research. Man, the Unknown (1935, 1939) In 1935, Carrel published a book titled L'Homme, cet inconnu (Man, the Unknown), which became a best-seller. In the book, he attempted to outline a comprehensive account of what is known and more importantly unknown of the human body and human life "in light of discoveries in biology, physics, and medicine", to elucidate problems of the modern world, and to provide possible routes to a better life for human beings. For Carrel, the fundamental problem was that: [M]en cannot follow modern civilization along its present course, because they are degenerating. They have been fascinated by the beauty of the sciences of inert matter. They have not understood that their body and consciousness are subjected to natural laws, more obscure than, but as inexorable as, the laws of the sidereal world. Neither have they understood that they cannot transgress these laws without being punished. They must, therefore, learn the necessary relations of the cosmic universe, of their fellow men, and of their inner selves, and also those of their tissues and their mind. Indeed, man stands above all things. Should he degenerate, the beauty of civilization, and even the grandeur of the physical universe, would vanish. ... Humanity's attention must turn from the machines of the world of inanimate matter to the body and the soul of man, to the organic and mental processes which have created the machines and the universe of Newton and Einstein. Carrel advocated, in part, that mankind could better itself by following the guidance of an elite group of intellectuals, and by incorporating eugenics into the social framework. He argued for an aristocracy springing from individuals of potential, writing: We must single out the children who are endowed with high potentialities, and develop them as completely as possible. And in this manner give to the nation a non-hereditary aristocracy. Such children may be found in all classes of society, although distinguished men appear more frequently in distinguished families than in others. The descendants of the founders of American civilization may still possess the ancestral qualities. These qualities are generally hidden under the cloak of degeneration. But this degeneration is often superficial. It comes chiefly from education, idleness, lack of responsibility and moral discipline. The sons of very rich men, like those of criminals, should be removed while still infants from their natural surroundings. Thus separated from their family, they could manifest their hereditary strength. In the aristocratic families of Europe there are also individuals of great vitality. The issue of the Crusaders is by no means extinct. The laws of genetics indicate the probability that the legendary audacity and love of adventure can appear again in the lineage of the feudal lords. It is possible also that the offspring of the great criminals who had imagination, courage, and judgment, of the heroes of the French or Russian Revolutions, of the high-handed business men who live among us, might be excellent building stones for an enterprising minority. As we know, criminality is not hereditary if not united with feeble-mindedness or other mental or cerebral defects. High potentialities are rarely encountered in the sons of honest, intelligent, hard-working men who have had ill luck in their careers, who have failed in business or have muddled along all their lives in inferior positions. Or among peasants living on the same spot for centuries. However, from such people sometimes spring artists, poets, adventurers, saints. A brilliantly gifted and well-known New York family came from peasants who cultivated their farm in the south of France from the time of Charlemagne to that of Napoleon. Carrel advocated for euthanasia for criminals, and the criminally insane, specifically endorsing the use of gassing: (t)he conditioning of petty criminals with the whip, or some more scientific procedure, followed by a short stay in hospital, would probably suffice to insure order. Those who have murdered, robbed while armed with automatic pistol or machine gun, kidnapped children, despoiled the poor of their savings, misled the public in important matters, should be humanely and economically disposed of in small euthanasic institutions supplied with proper gasses. A similar treatment could be advantageously applied to the insane, guilty of criminal acts. Otherwise he endorsed voluntary positive eugenics. He wrote: We have mentioned that natural selection has not played its part for a long while. That many inferior individuals have been conserved through the efforts of hygiene and medicine. But we cannot prevent the reproduction of the weak when they are neither insane nor criminal. Or destroy sickly or defective children as we do the weaklings in a litter of puppies. The only way to obviate the disastrous predominance of the weak is to develop the strong. Our efforts to render normal the unfit are evidently useless. We should, then, turn our attention toward promoting the optimum growth of the fit. By making the strong still stronger, we could effectively help the weak; For the herd always profits by the ideas and inventions of the elite. Instead of leveling organic and mental inequalities, we should amplify them and construct greater men. He continued: Carrel's endorsement of euthanasia of the criminal and insane was published in the mid-1930s, prior to the implementation of death camps and gas chambers in Nazi Germany. In the 1936 German introduction of his book, at the publisher's request, he added the following praise of the Nazi regime which did not appear in the editions in other languages: (t)he German government has taken energetic measures against the propagation of the defective, the mentally diseased, and the criminal. The ideal solution would be the suppression of each of these individuals as soon as he has proven himself to be dangerous. French Foundation for the Study of Human Problems In 1937, Carrel joined Jean Coutrot's Centre d'Etudes des Problèmes Humains - Coutrot's aim was to develop what he called an "economic humanism" through "collective thinking." In 1941, through connections to the cabinet of Vichy France president Philippe Pétain (specifically, French industrial physicians André Gros and Jacques Ménétrier) he went on to advocate for the creation of the French Foundation for the Study of Human Problems ( which was created by decree of the Vichy regime in 1941, and where he served as "regent". The foundation was at the origin of the 11 October 1946, law, enacted by the Provisional Government of the French Republic (GPRF), which institutionalized the field of occupational medicine. It worked on demographics (Robert Gessain, Paul Vincent, Jean Bourgeois-Pichat), on economics, (François Perroux), on nutrition (Jean Sutter), on habitation (Jean Merlet) and on the first opinion polls (Jean Stoetzel). "The foundation was chartered as a public institution under the joint supervision of the ministries of finance and public health. It was given financial autonomy and a budget of forty million francs—roughly one franc per inhabitant—a true luxury considering the burdens imposed by the German Occupation on the nation's resources. By way of comparison, the whole Centre National de la Recherche Scientifique (CNRS) was given a budget of fifty million francs." The Foundation made many positive accomplishments during its time. It promoted the 16 December 1942 Act which established the prenuptial certificate, which was required before marriage, and was aimed at insuring the good health of the spouses, in particular in regard to sexually transmitted diseases (STD) and "life hygiene". The institute also established the , which could be used to record students' grades in the French secondary schools, and thus classify and select them according to scholastic performance. According to Gwen Terrenoire, writing in Eugenics in France (1913–1941) : a review of research findings, "The foundation was a pluridisciplinary centre that employed around 300 researchers (mainly statisticians, psychologists, physicians) from the summer of 1942 to the end of the autumn of 1944. After the liberation of Paris, Carrel was suspended by the Minister of Health; he died in November 1944, but the Foundation itself was "purged", only to reappear in a short time as the Institut national d'études démographiques (INED) that is still active." Although Carrel himself was dead most members of his team did move to the INED, which was led by demographist Alfred Sauvy, who coined the expression "Third World". Others joined Robert Debré's "Institut national d'hygiène" (National Hygiene Institute), which later became the INSERM. See also HeLa Notes References Citations Cited sources Further reading Etienne Lepicard. L'Homme, cet inconnu d'Alexis Carrel (1935). Anatomie d'un succès, analyse d'un échec, Paris, Classiques Garnier, « Littérature, Histoire, Politique, 38 », 2019. Feuerwerker, Elie. Alexis Carrel et l'eugénisme. Le Monde, 1er Juillet 1986. Bonnafé, Lucien and Tort, Patrick. L'Homme, cet inconnu? Alexis Carrel, Jean-Marie le Pen et les chambres a gaz Editions Syllepse, 1996. David Zane Mairowitz. "Fascism à la mode: in France, the far right presses for national purity", Harper's Magazine; 10/1/1997 Berman, Paul. Terror and Liberalism W. W. Norton, 2003. Walther, Rudolph. Die seltsamen Lehren des Doktor Carrel, DIE ZEIT, 31.07.2003 Nr. 32 Terrenoire, Gwen, CNRS. Eugenics in France (1913–1941) : a review of research findings Joint Programmatic Commission UNESCO-ONG Science and Ethics, 24 March 2003 (Comité de Liaison ONG-UNESCO) Borghi L. (2015) "Heart Matters. The Collaboration Between Surgeons and Engineers in the Rise of Cardiac Surgery". In: Pisano R. (eds) A Bridge between Conceptual Frameworks. History of Mechanism and Machine Science, vol 27. Springer, Dordrecht, pp. 53–68 External links including the Nobel Lecture on December 11, 1912 Suture of Blood-Vessels and Transplantation of Organs Research Foundation entitled to Alexis Carrel Time, 16 October 1944 Death of Alexis Carrel, Time, 13 November 1944 1873 births 1944 deaths French eugenicists Converts to Roman Catholicism from atheism or agnosticism French Nobel laureates Nobel laureates in Physiology or Medicine French Roman Catholics French collaborators with Nazi Germany Chevaliers of the Légion d'honneur Members of the Pontifical Academy of Sciences Corresponding Members of the Russian Academy of Sciences (1917–1925) Corresponding Members of the USSR Academy of Sciences Honorary Members of the USSR Academy of Sciences People from Sainte-Foy-lès-Lyon French vascular surgeons History of transplant surgery Rockefeller University people 20th-century French physicians

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1130

https://en.wikipedia.org/wiki/Avicenna

Avicenna

Ibn Sina (), also known as Abu Ali Sina (), Pour Sina (), and often known in the West as Avicenna (;  – June 1037), was a Persian polymath who is regarded as one of the most significant physicians, astronomers, thinkers and writers of the Islamic Golden Age, and the father of early modern medicine. Sajjad H. Rizvi has called Avicenna "arguably the most influential philosopher of the pre-modern era". He was a Muslim Peripatetic philosopher influenced by Greek Aristotelian philosophy. Of the 450 works he is believed to have written, around 240 have survived, including 150 on philosophy and 40 on medicine. His most famous works are The Book of Healing, a philosophical and scientific encyclopedia, and The Canon of Medicine, a medical encyclopedia which became a standard medical text at many medieval universities and remained in use as late as 1650. Besides philosophy and medicine, Avicenna's corpus includes writings on astronomy, alchemy, geography and geology, psychology, Islamic theology, logic, mathematics, physics and works of poetry. Name is a Latin corruption of the Arabic patronym Ibn Sīnā (), meaning "Son of Sina". However, Avicenna was not the son but the great-great-grandson of a man named Sina. His formal Arabic name was Abū ʿAlī al-Ḥusayn bin ʿAbdullāh ibn al-Ḥasan bin ʿAlī bin Sīnā al-Balkhi al-Bukhari (). Circumstances Avicenna created an extensive corpus of works during what is commonly known as the Islamic Golden Age, in which the translations of Byzantine Greco-Roman, Persian and Indian texts were studied extensively. Greco-Roman (Mid- and Neo-Platonic, and Aristotelian) texts translated by the Kindi school were commented, redacted and developed substantially by Islamic intellectuals, who also built upon Persian and Indian mathematical systems, astronomy, algebra, trigonometry and medicine. The Samanid dynasty in the eastern part of Persia, Greater Khorasan and Central Asia as well as the Buyid dynasty in the western part of Persia and Iraq provided a thriving atmosphere for scholarly and cultural development. Under the Samanids, Bukhara rivaled Baghdad as a cultural capital of the Islamic world. There, the study of the Quran and the Hadith thrived. Philosophy, Fiqh and theology (kalaam) were further developed, most noticeably by Avicenna and his opponents. Al-Razi and Al-Farabi had provided methodology and knowledge in medicine and philosophy. Avicenna had access to the great libraries of Balkh, Khwarezm, Gorgan, Rey, Isfahan and Hamadan. Various texts (such as the 'Ahd with Bahmanyar) show that he debated philosophical points with the greatest scholars of the time. Aruzi Samarqandi describes how before Avicenna left Khwarezm he had met Al-Biruni (a famous scientist and astronomer), Abu Nasr Iraqi (a renowned mathematician), Abu Sahl Masihi (a respected philosopher) and Abu al-Khayr Khammar (a great physician). Biography Early life and education Avicenna was born in in the village of Afshana in Transoxiana to a family of Persian stock. The village was near the Samanid capital of Bukhara, which was his mother's hometown. His father Abd Allah was a native of the city of Balkh in Tukharistan. An official of the Samanid bureaucracy, he had served as the governor of a village of the royal estate of Harmaytan (near Bukhara) during the reign of Nuh II (). Avicenna also had a younger brother. A few years later, the family settled in Bukhara, a centre of learning, which attracted many scholars. It was there that Avicenna was educated, which early on was seemingly administered by his father. Although both Avicenna's father and brother had converted to Ismailism, he himself did not follow the faith. He was instead an adherent of the Hanafi school, which was also followed by the Samanids. Avicenna was first schooled in the Quran and literature, and by the age of 10, he had memorised the entire Quran. He was later sent by his father to an Indian greengrocer, who taught him arithmetic. Afterwards, he was schooled in Jurisprudence by the Hanafi jurist Ismail al-Zahid. Some time later, Avicenna's father invited the physician and philosopher Abu Abdallah al-Natili to their house to educate Avicenna. Together, they studied the Isagoge of Porphyry (died 305) and possibly the Categories of Aristotle (died 322 BC) as well. After Avicenna had read the Almagest of Ptolemy (died 170) and Euclid's Elements, Natili told him to continue his research independently. By the time Avicenna was eighteen, he was well-educated in Greek sciences. Although Avicenna only mentions Natili as his teacher in his autobiography, he most likely had other teachers as well, such as the physicians Abu Mansur Qumri and Abu Sahl al-Masihi. Career In Bukhara and Gurganj At the age of seventeen, Avicenna was made a physician of Nuh II. By the time Avicenna was at least 21 years old, his father died. He was subsequently given an administrative post, possibly succeeding his father as the governor of Harmaytan. Avicenna later moved to Gurganj, the capital of Khwarazm, which he reports that he did due to "necessity". The date he went to the place is uncertain, as he reports that he served the Khwarazmshah (ruler) of the region, the Ma'munid Abu al-Hasan Ali. The latter ruled from 997 to 1009, which indicates that Avicenna moved sometime during that period. He may have moved in 999, the year which the Samanid state fell after the Turkic Qarakhanids captured Bukhara and imprisoned the Samanid ruler Abd al-Malik II. Due to his high position and strong connection with the Samanids, Avicenna may have found himself in an unfavorable position after the fall of his suzerain. It was through the minister of Gurganj, Abu'l-Husayn as-Sahi, a patron of Greek sciences, that Avicenna entered into the service of Abu al-Hasan Ali. Under the Ma'munids, Gurganj became a centre of learning, attracting many prominent figures, such as Avicenna and his former teacher Abu Sahl al-Masihi, the mathematician Abu Nasr Mansur, the physician Ibn al-Khammar, and the philologist al-Tha'alibi. In Gurgan Avicenna later moved due to "necessity" once more (in 1012), this time to the west. There he travelled through the Khurasani cities of Nasa, Abivard, Tus, Samangan and Jajarm. He was planning to visit the ruler of the city of Gurgan, the Ziyarid Qabus (), a cultivated patron of writing, whose court attracted many distinguished poets and scholars. However, when Avicenna eventually arrived, he discovered that the ruler had been dead since the winter of 1013. Avicenna then left Gurgan for Dihistan, but returned after becoming ill. There he met Abu 'Ubayd al-Juzjani (died 1070) who became his pupil and companion. Avicenna stayed briefly in Gurgan, reportedly serving Qabus' son and successor Manuchihr () and resided in the house of a patron. In Ray and Hamadan In , Avicenna went to the city of Ray, where he entered into the service of the Buyid amir (ruler) Majd al-Dawla () and his mother Sayyida Shirin, the de facto ruler of the realm. There he served as the physician at the court, treating Majd al-Dawla, who was suffering from melancholia. Avicenna reportedly later served as the "business manager" of Sayyida Shirin in Qazvin and Hamadan, though details regarding this tenure are unclear. During his period, Avicenna finished his Canon of Medicine, and started writing his Book of Healing. In 1015, during Avicenna's stay in Hamadan, he participated in a public debate, as was custom for newly arrived scholars in western Iran at that time. The purpose of the debate was to examining one's reputation against a prominent local resident. The person whom Avicenna debated against was Abu'l-Qasim al-Kirmani, a member of the school of philosophers of Baghdad. The debate became heated, resulting in Avicenna accusing Abu'l-Qasim of lack of basic knowledge in logic, while Abu'l-Qasim accused Avicenna of impoliteness. After the debate, Avicenna sent a letter to the Baghdad Peripatetics, asking if Abu'l-Qasim's claim that he shared the same opinion as them was true. Abu'l-Qasim later retaliated by writing a letter to an unknown person, in which he made accusations so serious, that Avicenna wrote to a deputy of Majd al-Dawla, named Abu Sa'd, to investigate the matter. The accusation made towards Avicenna may have been the same as he had received earlier, in which he was accused by the people of Hamadan of copying the stylistic structures of the Quran in his Sermons on Divine Unity. The seriousness of this charge, in the words of the historian Peter Adamson, "cannot be underestimated in the larger Muslim culture." Not long afterwards, Avicenna shifted his allegiance to the rising Buyid amir Shams al-Dawla (the younger brother of Majd al-Dawla), which Adamson suggests was due to Abu'l-Qasim also working under Sayyida Shirin. Avicenna had been called upon by Shams al-Dawla to treat him, but after the latters campaign in the same year against his former ally, the Annazid ruler Abu Shawk (), he forced Avicenna to become his vizier. Although Avicenna would sometimes clash with Shams al-Dawla's troops, he remained vizier until the latter died of colic in 1021. Avicenna was asked by Shams al-Dawla's son and successor Sama' al-Dawla () stay as vizier, but instead went into hiding with his patron Abu Ghalib al-Attar, to wait for better opportunities to emerge. It was during this period that Avicenna was secretly in contact with Ala al-Dawla Muhammad (), the Kakuyid ruler of Isfahan and uncle of Sayyida Shirin. During his stay at Attar's home that Avicenna completed his Book of Healing, writing fifty pages a day. The Buyid court in Hamadan, particularly the Kurdish vizier Taj al-Mulk, suspected Avicenna of correspondence with Ala al-Dawla, and as result had the house of Attar ransacked and Avicenna imprisoned in the fortress of Fardajan, outside Hamadan. Juzjani blames one of Avicenna's informers for his capture. Avicenna was imprisoned in four months, until Ala al-Dawla captured Hamadan, thus putting an end to Sama al-Dawla's reign. In Isfahan Avicenna was subsequently released, and went to Isfahan, where he was well received by Ala al-Dawla. In the words of Juzjani, the Kakuyid ruler gave Avicenna "the respect and esteem which someone like him deserved." Adamson also says that Avicenna's service under Ala al-Dawla "proved to be the most stable period of his life." Avicenna served as the advisor, if not vizier of Ala al-Dawla, accompanying him in many of his military expeditions and travels. Avicenna dedicated two Persian works to him, a philosophical treatise named Danish-nama-yi Ala'i ("Book of Science for Ala"), and a medical treatise about the pulse. During the brief occupation of Isfahan by the Ghaznavids in January 1030, Avicenna and Ala al-Dawla relocated to the southwestern Iranian region of Khuzistan, where they stayed until the death of the Ghaznavid ruler Mahmud (), which occurred two months later. It was seemingly when Avicenna returned to Isfahan that he started writing his Pointers and Reminders. In 1037, while Avicenna was accompanying Ala al-Dawla to a battle near Isfahan, he was hit by a severe colic, which he had been constantly suffering from throughout his life. He died shortly afterwards in Hamadan, where he was buried. Philosophy Avicenna wrote extensively on early Islamic philosophy, especially the subjects logic, ethics and metaphysics, including treatises named Logic and Metaphysics. Most of his works were written in Arabic—then the language of science in the Middle East—and some in Persian. Of linguistic significance even to this day are a few books that he wrote in nearly pure Persian language (particularly the Danishnamah-yi 'Ala', Philosophy for Ala' ad-Dawla'). Avicenna's commentaries on Aristotle often criticized the philosopher, encouraging a lively debate in the spirit of ijtihad. Avicenna's Neoplatonic scheme of "emanations" became fundamental in the Kalam (school of theological discourse) in the 12th century. His Book of Healing became available in Europe in partial Latin translation some fifty years after its composition, under the title Sufficientia, and some authors have identified a "Latin Avicennism" as flourishing for some time, paralleling the more influential Latin Averroism, but suppressed by the Parisian decrees of 1210 and 1215. Avicenna's psychology and theory of knowledge influenced William of Auvergne, Bishop of Paris and Albertus Magnus, while his metaphysics influenced the thought of Thomas Aquinas. Metaphysical doctrine Early Islamic philosophy and Islamic metaphysics, imbued as it is with Islamic theology, distinguishes more clearly than Aristotelianism between essence and existence. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Avicenna, particularly that part relating to metaphysics, owes much to al-Farabi. The search for a definitive Islamic philosophy separate from Occasionalism can be seen in what is left of his work. Following al-Farabi's lead, Avicenna initiated a full-fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence cannot be inferred from or accounted for by the essence of existing things, and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent-cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect. Avicenna's consideration of the essence-attributes question may be elucidated in terms of his ontological analysis of the modalities of being; namely impossibility, contingency and necessity. Avicenna argued that the impossible being is that which cannot exist, while the contingent in itself (mumkin bi-dhatihi) has the potentiality to be or not to be without entailing a contradiction. When actualized, the contingent becomes a 'necessary existent due to what is other than itself' (wajib al-wujud bi-ghayrihi). Thus, contingency-in-itself is potential beingness that could eventually be actualized by an external cause other than itself. The metaphysical structures of necessity and contingency are different. Necessary being due to itself (wajib al-wujud bi-dhatihi) is true in itself, while the contingent being is 'false in itself' and 'true due to something else other than itself'. The necessary is the source of its own being without borrowed existence. It is what always exists. The Necessary exists 'due-to-Its-Self', and has no quiddity/essence (mahiyya) other than existence (wujud). Furthermore, It is 'One' (wahid ahad) since there cannot be more than one 'Necessary-Existent-due-to-Itself' without differentia (fasl) to distinguish them from each other. Yet, to require differentia entails that they exist 'due-to-themselves' as well as 'due to what is other than themselves'; and this is contradictory. However, if no differentia distinguishes them from each other, then there is no sense in which these 'Existents' are not one and the same. Avicenna adds that the 'Necessary-Existent-due-to-Itself' has no genus (jins), nor a definition (hadd), nor a counterpart (nadd), nor an opposite (did), and is detached (bari) from matter (madda), quality (kayf), quantity (kam), place (ayn), situation (wad) and time (waqt). Avicenna's theology on metaphysical issues (ilāhiyyāt) has been criticized by some Islamic scholars, among them al-Ghazali, Ibn Taymiyya and Ibn al-Qayyim. While discussing the views of the theists among the Greek philosophers, namely Socrates, Plato and Aristotle in Al-Munqidh min ad-Dalal ("Deliverance from Error"), al-Ghazali noted that the Greek philosophers "must be taxed with unbelief, as must their partisans among the Muslim philosophers, such as Avicenna and al-Farabi and their likes." He added that "None, however, of the Muslim philosophers engaged so much in transmitting Aristotle's lore as did the two men just mentioned. [...] The sum of what we regard as the authentic philosophy of Aristotle, as transmitted by al-Farabi and Avicenna, can be reduced to three parts: a part which must be branded as unbelief; a part which must be stigmatized as innovation; and a part which need not be repudiated at all." Argument for God's existence Avicenna made an argument for the existence of God which would be known as the "Proof of the Truthful" (Arabic: burhan al-siddiqin). Avicenna argued that there must be a "necessary existent" (Arabic: wajib al-wujud), an entity that cannot not exist and through a series of arguments, he identified it with the Islamic conception of God. Present-day historian of philosophy Peter Adamson called this argument one of the most influential medieval arguments for God's existence, and Avicenna's biggest contribution to the history of philosophy. Al-Biruni correspondence Correspondence between Avicenna (with his student Ahmad ibn 'Ali al-Ma'sumi) and Al-Biruni has survived in which they debated Aristotelian natural philosophy and the Peripatetic school. Abu Rayhan began by asking Avicenna eighteen questions, ten of which were criticisms of Aristotle's On the Heavens. Theology Avicenna was a devout Muslim and sought to reconcile rational philosophy with Islamic theology. His aim was to prove the existence of God and His creation of the world scientifically and through reason and logic. Avicenna's views on Islamic theology (and philosophy) were enormously influential, forming part of the core of the curriculum at Islamic religious schools until the 19th century. Avicenna wrote a number of short treatises dealing with Islamic theology. These included treatises on the prophets (whom he viewed as "inspired philosophers"), and also on various scientific and philosophical interpretations of the Quran, such as how Quranic cosmology corresponds to his own philosophical system. In general these treatises linked his philosophical writings to Islamic religious ideas; for example, the body's afterlife. There are occasional brief hints and allusions in his longer works, however, that Avicenna considered philosophy as the only sensible way to distinguish real prophecy from illusion. He did not state this more clearly because of the political implications of such a theory, if prophecy could be questioned, and also because most of the time he was writing shorter works which concentrated on explaining his theories on philosophy and theology clearly, without digressing to consider epistemological matters which could only be properly considered by other philosophers. Later interpretations of Avicenna's philosophy split into three different schools; those (such as al-Tusi) who continued to apply his philosophy as a system to interpret later political events and scientific advances; those (such as al-Razi) who considered Avicenna's theological works in isolation from his wider philosophical concerns; and those (such as al-Ghazali) who selectively used parts of his philosophy to support their own attempts to gain greater spiritual insights through a variety of mystical means. It was the theological interpretation championed by those such as al-Razi which eventually came to predominate in the madrasahs. Avicenna memorized the Quran by the age of ten, and as an adult, he wrote five treatises commenting on suras from the Quran. One of these texts included the Proof of Prophecies, in which he comments on several Quranic verses and holds the Quran in high esteem. Avicenna argued that the Islamic prophets should be considered higher than philosophers. Avicenna is generally understood to have been aligned with the Sunni Hanafi school of thought. Avicenna studied Hanafi law, many of his notable teachers were Hanafi jurists, and he served under the Hanafi court of Ali ibn Mamun. Avicenna said at an early age that he remained "unconvinced" by Ismaili missionary attempts to convert him. Medieval historian Ẓahīr al-dīn al-Bayhaqī (d. 1169) also believed Avicenna to be a follower of the Brethren of Purity. Thought experiments While he was imprisoned in the castle of Fardajan near Hamadhan, Avicenna wrote his famous "floating man"—literally falling man—a thought experiment to demonstrate human self-awareness and the substantiality and immateriality of the soul. Avicenna believed his "Floating Man" thought experiment demonstrated that the soul is a substance, and claimed humans cannot doubt their own consciousness, even in a situation that prevents all sensory data input. The thought experiment told its readers to imagine themselves created all at once while suspended in the air, isolated from all sensations, which includes no sensory contact with even their own bodies. He argued that, in this scenario, one would still have self-consciousness. Because it is conceivable that a person, suspended in air while cut off from sense experience, would still be capable of determining his own existence, the thought experiment points to the conclusions that the soul is a perfection, independent of the body, and an immaterial substance. The conceivability of this "Floating Man" indicates that the soul is perceived intellectually, which entails the soul's separateness from the body. Avicenna referred to the living human intelligence, particularly the active intellect, which he believed to be the hypostasis by which God communicates truth to the human mind and imparts order and intelligibility to nature. Following is an English translation of the argument: However, Avicenna posited the brain as the place where reason interacts with sensation. Sensation prepares the soul to receive rational concepts from the universal Agent Intellect. The first knowledge of the flying person would be "I am," affirming his or her essence. That essence could not be the body, obviously, as the flying person has no sensation. Thus, the knowledge that "I am" is the core of a human being: the soul exists and is self-aware. Avicenna thus concluded that the idea of the self is not logically dependent on any physical thing, and that the soul should not be seen in relative terms, but as a primary given, a substance. The body is unnecessary; in relation to it, the soul is its perfection. In itself, the soul is an immaterial substance. The Canon of Medicine Avicenna authored a five-volume medical encyclopedia: The Canon of Medicine (Al-Qanun fi't-Tibb). It was used as the standard medical textbook in the Islamic world and Europe up to the 18th century. The Canon still plays an important role in Unani medicine. Liber Primus Naturalium Avicenna considered whether events like rare diseases or disorders have natural causes. He used the example of polydactyly to explain his perception that causal reasons exist for all medical events. This view of medical phenomena anticipated developments in the Enlightenment by seven centuries. The Book of Healing Earth sciences Avicenna wrote on Earth sciences such as geology in The Book of Healing. While discussing the formation of mountains, he explained: Philosophy of science In the Al-Burhan (On Demonstration) section of The Book of Healing, Avicenna discussed the philosophy of science and described an early scientific method of inquiry. He discussed Aristotle's Posterior Analytics and significantly diverged from it on several points. Avicenna discussed the issue of a proper methodology for scientific inquiry and the question of "How does one acquire the first principles of a science?" He asked how a scientist would arrive at "the initial axioms or hypotheses of a deductive science without inferring them from some more basic premises?" He explained that the ideal situation is when one grasps that a "relation holds between the terms, which would allow for absolute, universal certainty". Avicenna then added two further methods for arriving at the first principles: the ancient Aristotelian method of induction (istiqra), and the method of examination and experimentation (tajriba). Avicenna criticized Aristotelian induction, arguing that "it does not lead to the absolute, universal, and certain premises that it purports to provide." In its place, he developed a "method of experimentation as a means for scientific inquiry." Logic An early formal system of temporal logic was studied by Avicenna. Although he did not develop a real theory of temporal propositions, he did study the relationship between temporalis and the implication. Avicenna's work was further developed by Najm al-Dīn al-Qazwīnī al-Kātibī and became the dominant system of Islamic logic until modern times. Avicennian logic also influenced several early European logicians such as Albertus Magnus and William of Ockham. Avicenna endorsed the law of non-contradiction proposed by Aristotle, that a fact could not be both true and false at the same time and in the same sense of the terminology used. He stated, "Anyone who denies the law of non-contradiction should be beaten and burned until he admits that to be beaten is not the same as not to be beaten, and to be burned is not the same as not to be burned." Physics In mechanics, Avicenna, in The Book of Healing, developed a theory of motion, in which he made a distinction between the inclination (tendency to motion) and force of a projectile, and concluded that motion was a result of an inclination (mayl) transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease. He viewed inclination as a permanent force whose effect is dissipated by external forces such as air resistance. The theory of motion presented by Avicenna was probably influenced by the 6th-century Alexandrian scholar John Philoponus. Avicenna's is a less sophisticated variant of the theory of impetus developed by Buridan in the 14th century. It is unclear if Buridan was influenced by Avicenna, or by Philoponus directly. In optics, Avicenna was among those who argued that light had a speed, observing that "if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite." He also provided a wrong explanation of the rainbow phenomenon. Carl Benjamin Boyer described Avicenna's ("Ibn Sīnā") theory on the rainbow as follows: In 1253, a Latin text entitled Speculum Tripartitum stated the following regarding Avicenna's theory on heat: Psychology Avicenna's legacy in classical psychology is primarily embodied in the Kitab al-nafs parts of his Kitab al-shifa (The Book of Healing) and Kitab al-najat (The Book of Deliverance). These were known in Latin under the title De Anima (treatises "on the soul"). Notably, Avicenna develops what is called the Flying Man argument in the Psychology of The Cure I.1.7 as defence of the argument that the soul is without quantitative extension, which has an affinity with Descartes's cogito argument (or what phenomenology designates as a form of an "epoche"). Avicenna's psychology requires that connection between the body and soul be strong enough to ensure the soul's individuation, but weak enough to allow for its immortality. Avicenna grounds his psychology on physiology, which means his account of the soul is one that deals almost entirely with the natural science of the body and its abilities of perception. Thus, the philosopher's connection between the soul and body is explained almost entirely by his understanding of perception; in this way, bodily perception interrelates with the immaterial human intellect. In sense perception, the perceiver senses the form of the object; first, by perceiving features of the object by our external senses. This sensory information is supplied to the internal senses, which merge all the pieces into a whole, unified conscious experience. This process of perception and abstraction is the nexus of the soul and body, for the material body may only perceive material objects, while the immaterial soul may only receive the immaterial, universal forms. The way the soul and body interact in the final abstraction of the universal from the concrete particular is the key to their relationship and interaction, which takes place in the physical body. The soul completes the action of intellection by accepting forms that have been abstracted from matter. This process requires a concrete particular (material) to be abstracted into the universal intelligible (immaterial). The material and immaterial interact through the Active Intellect, which is a "divine light" containing the intelligible forms. The Active Intellect reveals the universals concealed in material objects much like the sun makes colour available to our eyes. Other contributions Astronomy and astrology Avicenna wrote an attack on astrology titled Resāla fī ebṭāl aḥkām al-nojūm, in which he cited passages from the Quran to dispute the power of astrology to foretell the future. He believed that each planet had some influence on the earth, but argued against astrologers being able to determine the exact effects. Avicenna's astronomical writings had some influence on later writers, although in general his work could be considered less developed than Alhazen or Al-Biruni. One important feature of his writing is that he considers mathematical astronomy as a separate discipline to astrology. He criticized Aristotle's view of the stars receiving their light from the Sun, stating that the stars are self-luminous, and believed that the planets are also self-luminous. He claimed to have observed Venus as a spot on the Sun. This is possible, as there was a transit on 24 May 1032, but Avicenna did not give the date of his observation, and modern scholars have questioned whether he could have observed the transit from his location at that time; he may have mistaken a sunspot for Venus. He used his transit observation to help establish that Venus was, at least sometimes, below the Sun in Ptolemaic cosmology, i.e. the sphere of Venus comes before the sphere of the Sun when moving out from the Earth in the prevailing geocentric model. He also wrote the Summary of the Almagest, (based on Ptolemy's Almagest), with an appended treatise "to bring that which is stated in the Almagest and what is understood from Natural Science into conformity". For example, Avicenna considers the motion of the solar apogee, which Ptolemy had taken to be fixed. Chemistry Avicenna was first to derive the attar of flowers from distillation and used steam distillation to produce essential oils such as rose essence, which he used as aromatherapeutic treatments for heart conditions. Unlike al-Razi, Avicenna explicitly disputed the theory of the transmutation of substances commonly believed by alchemists: Four works on alchemy attributed to Avicenna were translated into Latin as: was the most influential, having influenced later medieval chemists and alchemists such as Vincent of Beauvais. However, Anawati argues (following Ruska) that the de Anima is a fake by a Spanish author. Similarly the Declaratio is believed not to be actually by Avicenna. The third work (The Book of Minerals) is agreed to be Avicenna's writing, adapted from the Kitab al-Shifa (Book of the Remedy). Avicenna classified minerals into stones, fusible substances, sulfurs and salts, building on the ideas of Aristotle and Jabir. The epistola de Re recta is somewhat less sceptical of alchemy; Anawati argues that it is by Avicenna, but written earlier in his career when he had not yet firmly decided that transmutation was impossible. Poetry Almost half of Avicenna's works are versified. His poems appear in both Arabic and Persian. As an example, Edward Granville Browne claims that the following Persian verses are incorrectly attributed to Omar Khayyám, and were originally written by Ibn Sīnā: Legacy Classical Islamic civilization Robert Wisnovsky, a scholar of Avicenna attached to the McGill University, says that "Avicenna was the central figure in the long history of the rational sciences in Islam, particularly in the fields of metaphysics, logic and medicine" but that his works didn't only have an influence in these "secular" fields of knowledge alone, as "these works, or portions of them, were read, taught, copied, commented upon, quoted, paraphrased and cited by thousands of post-Avicennian scholars—not only philosophers, logicians, physicians and specialists in the mathematical or exact sciences, but also by those who specialized in the disciplines of ʿilm al-kalām (rational theology, but understood to include natural philosophy, epistemology and philosophy of mind) and usūl al-fiqh (jurisprudence, but understood to include philosophy of law, dialectic, and philosophy of language)." Middle Ages and Renaissance As early as the 14th century when Dante Alighieri depicted him in Limbo alongside the virtuous non-Christian thinkers in his Divine Comedy such as Virgil, Averroes, Homer, Horace, Ovid, Lucan, Socrates, Plato and Saladin. Avicenna has been recognized by both East and West, as one of the great figures in intellectual history. George Sarton, the author of The History of Science, described Avicenna as "one of the greatest thinkers and medical scholars in history" and called him "the most famous scientist of Islam and one of the most famous of all races, places, and times". He was one of the Islamic world's leading writers in the field of medicine. Along with Rhazes, Abulcasis, Ibn al-Nafis and al-Ibadi, Avicenna is considered an important compiler of early Muslim medicine. He is remembered in the Western history of medicine as a major historical figure who made important contributions to medicine and the European Renaissance. His medical texts were unusual in that where controversy existed between Galen and Aristotle's views on medical matters (such as anatomy), he preferred to side with Aristotle, where necessary updating Aristotle's position to take into account post-Aristotelian advances in anatomical knowledge. Aristotle's dominant intellectual influence among medieval European scholars meant that Avicenna's linking of Galen's medical writings with Aristotle's philosophical writings in the Canon of Medicine (along with its comprehensive and logical organisation of knowledge) significantly increased Avicenna's importance in medieval Europe in comparison to other Islamic writers on medicine. His influence following translation of the Canon was such that from the early fourteenth to the mid-sixteenth centuries he was ranked with Hippocrates and Galen as one of the acknowledged authorities, ("prince of physicians"). Modern reception In present-day Iran, Afghanistan and Tajikistan, he is considered a national icon, and is often regarded as among the greatest Persians. A monument was erected outside the Bukhara museum. The Avicenna Mausoleum and Museum in Hamadan was built in 1952. Bu-Ali Sina University in Hamadan (Iran), the biotechnology Avicenna Research Institute in Tehran (Iran), the ibn Sīnā Tajik State Medical University in Dushanbe, Ibn Sina Academy of Medieval Medicine and Sciences at Aligarh, India, Avicenna School in Karachi and Avicenna Medical College in Lahore, Pakistan, Ibn Sina Balkh Medical School in his native province of Balkh in Afghanistan, Ibni Sina Faculty Of Medicine of Ankara University Ankara, Turkey, the main classroom building (the Avicenna Building) of the Sharif University of Technology, and Ibn Sina Integrated School in Marawi City (Philippines) are all named in his honour. His portrait hangs in the Hall of the Avicenna Faculty of Medicine in the University of Paris. There is a crater on the Moon named Avicenna and a mangrove genus. In 1980, the Soviet Union, which then ruled his birthplace Bukhara, celebrated the thousandth anniversary of Avicenna's birth by circulating various commemorative stamps with artistic illustrations, and by erecting a bust of Avicenna based on anthropological research by Soviet scholars. Near his birthplace in Qishlak Afshona, some north of Bukhara, a training college for medical staff has been named for him. On the grounds is a museum dedicated to his life, times and work. The Avicenna Prize, established in 2003, is awarded every two years by UNESCO and rewards individuals and groups for their achievements in the field of ethics in science. The aim of the award is to promote ethical reflection on issues raised by advances in science and technology, and to raise global awareness of the importance of ethics in science. The Avicenna Directories (2008–15; now the World Directory of Medical Schools) list universities and schools where doctors, public health practitioners, pharmacists and others, are educated. The original project team stated "Why Avicenna? Avicenna ... was ... noted for his synthesis of knowledge from both east and west. He has had a lasting influence on the development of medicine and health sciences. The use of Avicenna's name symbolises the worldwide partnership that is needed for the promotion of health services of high quality." In June 2009, Iran donated a "Persian Scholars Pavilion" to United Nations Office in Vienna which is placed in the central Memorial Plaza of the Vienna International Center. The "Persian Scholars Pavilion" at United Nations in Vienna, Austria is featuring the statues of four prominent Iranian figures. Highlighting the Iranian architectural features, the pavilion is adorned with Persian art forms and includes the statues of renowned Iranian scientists Avicenna, Al-Biruni, Zakariya Razi (Rhazes) and Omar Khayyam. The 1982 Soviet film Youth of Genius () by recounts Avicenna's younger years. The film is set in Bukhara at the turn of the millennium. In Louis L'Amour's 1985 historical novel The Walking Drum, Kerbouchard studies and discusses Avicenna's The Canon of Medicine. In his book The Physician (1988) Noah Gordon tells the story of a young English medical apprentice who disguises himself as a Jew to travel from England to Persia and learn from Avicenna, the great master of his time. The novel was adapted into a feature film, The Physician, in 2013. Avicenna was played by Ben Kingsley. List of works The treatises of Avicenna influenced later Muslim thinkers in many areas including theology, philology, mathematics, astronomy, physics and music. His works numbered almost 450 volumes on a wide range of subjects, of which around 240 have survived. In particular, 150 volumes of his surviving works concentrate on philosophy and 40 of them concentrate on medicine. His most famous works are The Book of Healing, and The Canon of Medicine. Avicenna wrote at least one treatise on alchemy, but several others have been falsely attributed to him. His Logic, Metaphysics, Physics, and De Caelo, are treatises giving a synoptic view of Aristotelian doctrine, though Metaphysics demonstrates a significant departure from the brand of Neoplatonism known as Aristotelianism in Avicenna's world; Arabic philosophers have hinted at the idea that Avicenna was attempting to "re-Aristotelianise" Muslim philosophy in its entirety, unlike his predecessors, who accepted the conflation of Platonic, Aristotelian, Neo- and Middle-Platonic works transmitted into the Muslim world. The Logic and Metaphysics have been extensively reprinted, the latter, e.g., at Venice in 1493, 1495 and 1546. Some of his shorter essays on medicine, logic, etc., take a poetical form (the poem on logic was published by Schmoelders in 1836). Two encyclopedic treatises, dealing with philosophy, are often mentioned. The larger, Al-Shifa' (Sanatio), exists nearly complete in manuscript in the Bodleian Library and elsewhere; part of it on the De Anima appeared at Pavia (1490) as the Liber Sextus Naturalium, and the long account of Avicenna's philosophy given by Muhammad al-Shahrastani seems to be mainly an analysis, and in many places a reproduction, of the Al-Shifa'. A shorter form of the work is known as the An-najat (Liberatio). The Latin editions of part of these works have been modified by the corrections which the monastic editors confess that they applied. There is also a (hikmat-al-mashriqqiyya, in Latin Philosophia Orientalis), mentioned by Roger Bacon, the majority of which is lost in antiquity, which according to Averroes was pantheistic in tone. Avicenna's works further include: Sirat al-shaykh al-ra'is (The Life of Avicenna), ed. and trans. WE. Gohlman, Albany, NY: State University of New York Press, 1974. (The only critical edition of Avicenna's autobiography, supplemented with material from a biography by his student Abu 'Ubayd al-Juzjani. A more recent translation of the Autobiography appears in D. Gutas, Avicenna and the Aristotelian Tradition: Introduction to Reading Avicenna's Philosophical Works, Leiden: Brill, 1988; second edition 2014.) Al-isharat wa al-tanbihat (Remarks and Admonitions), ed. S. Dunya, Cairo, 1960; parts translated by S.C. Inati, Remarks and Admonitions, Part One: Logic, Toronto, Ont.: Pontifical Institute for Mediaeval Studies, 1984, and Ibn Sina and Mysticism, Remarks and Admonitions: Part 4, London: Kegan Paul International, 1996. Al-Qanun fi'l-tibb (The Canon of Medicine), ed. I. a-Qashsh, Cairo, 1987. (Encyclopedia of medicine.) manuscript, Latin translation, Flores Avicenne, Michael de Capella, 1508, Modern text. Ahmed Shawkat Al-Shatti, Jibran Jabbur. Risalah fi sirr al-qadar (Essay on the Secret of Destiny), trans. G. Hourani in Reason and Tradition in Islamic Ethics, Cambridge: Cambridge University Press, 1985. Danishnama-i 'ala'i (The Book of Scientific Knowledge), ed. and trans. P. Morewedge, The Metaphysics of Avicenna, London: Routledge and Kegan Paul, 1973. Kitab al-Shifa''' (The Book of Healing). (Avicenna's major work on philosophy. He probably began to compose al-Shifa' in 1014, and completed it in 1020.) Critical editions of the Arabic text have been published in Cairo, 1952–83, originally under the supervision of I. Madkour. Kitab al-Najat (The Book of Salvation), trans. F. Rahman, Avicenna's Psychology: An English Translation of Kitab al-Najat, Book II, Chapter VI with Historical-philosophical Notes and Textual Improvements on the Cairo Edition, Oxford: Oxford University Press, 1952. (The psychology of al-Shifa'.) (Digital version of the Arabic text) Risala fi'l-Ishq (A Treatise on Love). Translated by Emil L. Fackenheim. Persian works Avicenna's most important Persian work is the Danishnama-i 'Alai (, "the Book of Knowledge for [Prince] 'Ala ad-Daulah"). Avicenna created new scientific vocabulary that had not previously existed in Persian. The Danishnama covers such topics as logic, metaphysics, music theory and other sciences of his time. It has been translated into English by Parwiz Morewedge in 1977. The book is also important in respect to Persian scientific works.Andar Danesh-e Rag (, "On the Science of the Pulse") contains nine chapters on the science of the pulse and is a condensed synopsis. Persian poetry from Avicenna is recorded in various manuscripts and later anthologies such as Nozhat al-Majales. See also Al-Qumri (possibly Avicenna's teacher) Abdol Hamid Khosro Shahi (Iranian theologian) Mummia (Persian medicine) Namesakes of Ibn Sina Ibn Sina Academy of Medieval Medicine and Sciences in Aligarh Avicenna Bay in Antarctica Avicenna (crater) on the far side of the Moon Avicenna Cultural and Scientific Foundation Avicenne Hospital in Paris, France Avicenna International College in Budapest, Hungary Avicenna Mausoleum (complex dedicated to Avicenna) in Hamadan, Iran Avicenna Research Institute in Tehran, Iran Avicenna Tajik State Medical University in Dushanbe, Tajikistan Bu-Ali Sina University in Hamedan, Iran Ibn Sina Peak – named after the Scientist, on the Kyrgyzstan–Tajikistan border Ibn Sina Foundation in Houston, Texas Ibn Sina Hospital, Baghdad, Iraq Ibn Sina Hospital, Istanbul, Turkey Ibn Sina Medical College Hospital, Dhaka, Bangladesh Ibn Sina University Hospital of Rabat-Salé at Mohammed V University in Rabat, Morocco Ibne Sina Hospital, Multan, Punjab, Pakistan International Ibn Sina Clinic, Dushanbe, Tajikistan Philosophy Eastern philosophy Iranian philosophy Islamic philosophy Contemporary Islamic philosophy Science in the medieval Islamic world List of scientists in medieval Islamic world Sufi philosophy Science and technology in Iran Ancient Iranian medicine List of pre-modern Iranian scientists and scholars References Sources cited Further reading Encyclopedic articles (PDF version) Avicenna entry by Sajjad H. Rizvi in the Internet Encyclopedia of Philosophy Primary literature For an old list of other extant works, C. Brockelmann's Geschichte der arabischen Litteratur (Weimar 1898), vol. i. pp. 452–458. (XV. W.; G. W. T.) For a current list of his works see A. Bertolacci (2006) and D. Gutas (2014) in the section "Philosophy". Avicenne: Réfutation de l'astrologie. Edition et traduction du texte arabe, introduction, notes et lexique par Yahya Michot. Préface d'Elizabeth Teissier (Beirut-Paris: Albouraq, 2006) . William E. Gohlam (ed.), The Life of Ibn Sina. A Critical Edition and Annotated Translation, Albany, State of New York University Press, 1974. For Ibn Sina's life, see Ibn Khallikan's Biographical Dictionary, translated by de Slane (1842); F. Wüstenfeld's Geschichte der arabischen Aerzte und Naturforscher (Göttingen, 1840). Madelung, Wilferd and Toby Mayer (ed. and tr.), Struggling with the Philosopher: A Refutation of Avicenna's Metaphysics. A New Arabic Edition and English Translation of Shahrastani's Kitab al-Musara'a. Secondary literature This is, on the whole, an informed and good account of the life and accomplishments of one of the greatest influences on the development of thought both Eastern and Western. ... It is not as philosophically thorough as the works of D. Saliba, A.M. Goichon, or L. Gardet, but it is probably the best essay in English on this important thinker of the Middle Ages. (Julius R. Weinberg, The Philosophical Review, Vol. 69, No. 2, Apr. 1960, pp. 255–259) This is a distinguished work which stands out from, and above, many of the books and articles which have been written in this century on Avicenna (Ibn Sīnā) (980–1037). It has two main features on which its distinction as a major contribution to Avicennan studies may be said to rest: the first is its clarity and readability; the second is the comparative approach adopted by the author. ... (Ian Richard Netton, Journal of the Royal Asiatic Society, Third Series, Vol. 4, No. 2, July 1994, pp. 263–264) Y.T. Langermann (ed.), Avicenna and his Legacy. A Golden Age of Science and Philosophy, Brepols Publishers, 2010, For a new understanding of his early career, based on a newly discovered text, see also: Michot, Yahya, Ibn Sînâ: Lettre au vizir Abû Sa'd. Editio princeps d'après le manuscrit de Bursa, traduction de l'arabe, introduction, notes et lexique (Beirut-Paris: Albouraq, 2000) . This German publication is both one of the most comprehensive general introductions to the life and works of the philosopher and physician Avicenna (Ibn Sīnā, d. 1037) and an extensive and careful survey of his contribution to the history of science. Its author is a renowned expert in Greek and Arabic medicine who has paid considerable attention to Avicenna in his recent studies. ... (Amos Bertolacci, Isis, Vol. 96, No. 4, December 2005, p. 649) Shaikh al Rais Ibn Sina (Special number) 1958–59, Ed. Hakim Syed Zillur Rahman, Tibbia College Magazine, Aligarh Muslim University, Aligarh, India. Medicine Browne, Edward G. Islamic Medicine. Fitzpatrick Lectures Delivered at the Royal College of Physicians in 1919–1920, reprint: New Delhi: Goodword Books, 2001. Pormann, Peter & Savage-Smith, Emilie. Medieval Islamic Medicine, Washington: Georgetown University Press, 2007. Prioreschi, Plinio. Byzantine and Islamic Medicine, A History of Medicine, Vol. 4, Omaha: Horatius Press, 2001. Syed Ziaur Rahman. Pharmacology of Avicennian Cardiac Drugs (Metaanalysis of researches and studies in Avicennian Cardiac Drugs along with English translation of Risalah al Adwiya al Qalbiyah), Ibn Sina Academy of Medieval Medicine and Sciences, Aligarh, India, 2020 Philosophy Amos Bertolacci, The Reception of Aristotle's Metaphysics in Avicenna's Kitab al-Sifa'. A Milestone of Western Metaphysical Thought, Leiden: Brill 2006, (Appendix C contains an Overview of the Main Works by Avicenna on Metaphysics in Chronological Order). Dimitri Gutas, Avicenna and the Aristotelian Tradition: Introduction to Reading Avicenna's Philosophical Works, Leiden, Brill 2014, second revised and expanded edition (first edition: 1988), including an inventory of Avicenna' Authentic Works. Andreas Lammer: The Elements of Avicenna's Physics. Greek Sources and Arabic Innovations. Scientia graeco-arabica 20. Berlin / Boston: Walter de Gruyter, 2018. Jon McGinnis and David C. Reisman (eds.) Interpreting Avicenna: Science and Philosophy in Medieval Islam: Proceedings of the Second Conference of the Avicenna Study Group, Leiden: Brill, 2004. Michot, Jean R., La destinée de l'homme selon Avicenne, Louvain: Aedibus Peeters, 1986, . Nader El-Bizri, The Phenomenological Quest between Avicenna and Heidegger, Binghamton, N.Y.: Global Publications SUNY, 2000 (reprinted by SUNY Press in 2014 with a new Preface). Nader El-Bizri, "Avicenna and Essentialism," Review of Metaphysics, Vol. 54 (June 2001), pp. 753–778. Nader El-Bizri, "Avicenna's De Anima between Aristotle and Husserl," in The Passions of the Soul in the Metamorphosis of Becoming, ed. Anna-Teresa Tymieniecka, Dordrecht: Kluwer, 2003, pp. 67–89. Nader El-Bizri, "Being and Necessity: A Phenomenological Investigation of Avicenna's Metaphysics and Cosmology," in Islamic Philosophy and Occidental Phenomenology on the Perennial Issue of Microcosm and Macrocosm, ed. Anna-Teresa Tymieniecka, Dordrecht: Kluwer, 2006, pp. 243–261. Nader El-Bizri, 'Ibn Sīnā's Ontology and the Question of Being', Ishrāq: Islamic Philosophy Yearbook 2 (2011), 222–237 Nader El-Bizri, 'Philosophising at the Margins of 'Sh'i Studies': Reflections on Ibn Sīnā's Ontology', in The Study of Sh'i Islam. History, Theology and Law, eds. F. Daftary and G. Miskinzoda (London: I.B. Tauris, 2014), pp. 585–597. Reisman, David C. (ed.), Before and After Avicenna: Proceedings of the First Conference of the Avicenna Study Group'', Leiden: Brill, 2003. External links Avicenna (Ibn-Sina) on the Subject and the Object of Metaphysics with a list of translations of the logical and philosophical works and an annotated bibliography 980s births 1037 deaths 10th-century Iranian people 11th-century astronomers 11th-century Persian writers 11th-century philosophers Alchemists of medieval Islam Aristotelian philosophers Burials in Iran Buyid viziers Classical humanists Critics of atheism Cultural critics Epistemologists Founders of philosophical traditions Iranian music theorists Islamic philosophers Transoxanian Islamic scholars Logicians People from Bukhara Region Pharmacologists of medieval Iran Medieval Persian poets Medieval Persian writers Metaphysicians Moral philosophers Musical theorists of medieval Islam Ontologists People from Khorasan Persian physicists Philosophers of ethics and morality Philosophers of logic Philosophers of mind Philosophers of psychology Philosophers of religion Philosophers of science Physicians of medieval Islam Samanid scholars Unani medicine Medieval Persian philosophers Iranian logicians Iranian ethicists People who memorized the Quran Samanid officials

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1134

https://en.wikipedia.org/wiki/Analysis

Analysis

Analysis is the process of breaking a complex topic or substance into smaller parts in order to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle (384–322 B.C.), though analysis as a formal concept is a relatively recent development. The word comes from the Ancient Greek ἀνάλυσις (analysis, "a breaking-up" or "an untying;" from ana- "up, throughout" and lysis "a loosening"). From it also comes the word's plural, analyses. As a formal concept, the method has variously been ascribed to Alhazen, René Descartes (Discourse on the Method), and Galileo Galilei. It has also been ascribed to Isaac Newton, in the form of a practical method of physical discovery (which he did not name). Applications Science The field of chemistry uses analysis in three ways: to identify the components of a particular chemical compound (qualitative analysis), to identify the proportions of components in a mixture (quantitative analysis), and to break down chemical processes and examine chemical reactions between elements of matter. For an example of its use, analysis of the concentration of elements is important in managing a nuclear reactor, so nuclear scientists will analyze neutron activation to develop discrete measurements within vast samples. A matrix can have a considerable effect on the way a chemical analysis is conducted and the quality of its results. Analysis can be done manually or with a device. Types of Analysis: A) Qualitative Analysis: It is concerned with which components are in a given sample or compound. Example: Precipitation reaction B) Quantitative Analysis: It is to determine the quantity of individual component present in a given sample or compound. Example: To find concentration by uv-spectrophotometer. Isotopes Chemists can use isotope analysis to assist analysts with issues in anthropology, archeology, food chemistry, forensics, geology, and a host of other questions of physical science. Analysts can discern the origins of natural and man-made isotopes in the study of environmental radioactivity. Business Financial statement analysis – the analysis of the accounts and the economic prospects of a firm Fundamental analysis – a stock valuation method that uses financial analysis Gap analysis – involves the comparison of actual performance with potential or desired performance of an organization Business analysis – involves identifying the needs and determining the solutions to business problems Price analysis – involves the breakdown of a price to a unit figure Market analysis – consists of suppliers and customers, and price is determined by the interaction of supply and demand Technical analysis – the study of price action in securities markets in order to forecast future prices Opportunity analysis – consists of customers trends within the industry, customer demand and experience determine purchasing behavior Computer science Requirements analysis – encompasses those tasks that go into determining the needs or conditions to meet for a new or altered product, taking account of the possibly conflicting requirements of the various stakeholders, such as beneficiaries or users. Competitive analysis (online algorithm) – shows how online algorithms perform and demonstrates the power of randomization in algorithms Lexical analysis – the process of processing an input sequence of characters and producing as output a sequence of symbols Object-oriented analysis and design – à la Booch Program analysis (computer science) – the process of automatically analysing the behavior of computer programs Semantic analysis (computer science) – a pass by a compiler that adds semantical information to the parse tree and performs certain checks Static code analysis – the analysis of computer software that is performed without actually executing programs built from that Structured systems analysis and design methodology – à la Yourdon Syntax analysis – a process in compilers that recognizes the structure of programming languages, also known as parsing Worst-case execution time – determines the longest time that a piece of software can take to run Economics Agroecosystem analysis Input–output model if applied to a region, is called Regional Impact Multiplier System Engineering Analysts in the field of engineering look at requirements, structures, mechanisms, systems and dimensions. Electrical engineers analyse systems in electronics. Life cycles and system failures are broken down and studied by engineers. It is also looking at different factors incorporated within the design. Intelligence The field of intelligence employs analysts to break down and understand a wide array of questions. Intelligence agencies may use heuristics, inductive and deductive reasoning, social network analysis, dynamic network analysis, link analysis, and brainstorming to sort through problems they face. Military intelligence may explore issues through the use of game theory, Red Teaming, and wargaming. Signals intelligence applies cryptanalysis and frequency analysis to break codes and ciphers. Business intelligence applies theories of competitive intelligence analysis and competitor analysis to resolve questions in the marketplace. Law enforcement intelligence applies a number of theories in crime analysis. Linguistics Linguistics explores individual languages and language in general. It breaks language down and analyses its component parts: theory, sounds and their meaning, utterance usage, word origins, the history of words, the meaning of words and word combinations, sentence construction, basic construction beyond the sentence level, stylistics, and conversation. It examines the above using statistics and modeling, and semantics. It analyses language in context of anthropology, biology, evolution, geography, history, neurology, psychology, and sociology. It also takes the applied approach, looking at individual language development and clinical issues. Literature Literary criticism is the analysis of literature. The focus can be as diverse as the analysis of Homer or Freud. While not all literary-critical methods are primarily analytical in nature, the main approach to the teaching of literature in the west since the mid-twentieth century, literary formal analysis or close reading, is. This method, rooted in the academic movement labelled The New Criticism, approaches texts – chiefly short poems such as sonnets, which by virtue of their small size and significant complexity lend themselves well to this type of analysis – as units of discourse that can be understood in themselves, without reference to biographical or historical frameworks. This method of analysis breaks up the text linguistically in a study of prosody (the formal analysis of meter) and phonic effects such as alliteration and rhyme, and cognitively in examination of the interplay of syntactic structures, figurative language, and other elements of the poem that work to produce its larger effects. Mathematics Modern mathematical analysis is the study of infinite processes. It is the branch of mathematics that includes calculus. It can be applied in the study of classical concepts of mathematics, such as real numbers, complex variables, trigonometric functions, and algorithms, or of non-classical concepts like constructivism, harmonics, infinity, and vectors. Florian Cajori explains in A History of Mathematics (1893) the difference between modern and ancient mathematical analysis, as distinct from logical analysis, as follows: The terms synthesis and analysis are used in mathematics in a more special sense than in logic. In ancient mathematics they had a different meaning from what they now have. The oldest definition of mathematical analysis as opposed to synthesis is that given in [appended to] Euclid, XIII. 5, which in all probability was framed by Eudoxus: "Analysis is the obtaining of the thing sought by assuming it and so reasoning up to an admitted truth; synthesis is the obtaining of the thing sought by reasoning up to the inference and proof of it." The analytic method is not conclusive, unless all operations involved in it are known to be reversible. To remove all doubt, the Greeks, as a rule, added to the analytic process a synthetic one, consisting of a reversion of all operations occurring in the analysis. Thus the aim of analysis was to aid in the discovery of synthetic proofs or solutions. James Gow uses a similar argument as Cajori, with the following clarification, in his A Short History of Greek Mathematics (1884): The synthetic proof proceeds by shewing that the proposed new truth involves certain admitted truths. An analytic proof begins by an assumption, upon which a synthetic reasoning is founded. The Greeks distinguished theoretic from problematic analysis. A theoretic analysis is of the following kind. To prove that A is B, assume first that A is B. If so, then, since B is C and C is D and D is E, therefore A is E. If this be known a falsity, A is not B. But if this be a known truth and all the intermediate propositions be convertible, then the reverse process, A is E, E is D, D is C, C is B, therefore A is B, constitutes a synthetic proof of the original theorem. Problematic analysis is applied in all cases where it is proposed to construct a figure which is assumed to satisfy a given condition. The problem is then converted into some theorem which is involved in the condition and which is proved synthetically, and the steps of this synthetic proof taken backwards are a synthetic solution of the problem. Music Musical analysis – a process attempting to answer the question "How does this music work?" Musical Analysis is a study of how the composers use the notes together to compose music. Those studying music will find differences with each composer's musical analysis, which differs depending on the culture and history of music studied. An analysis of music is meant to simplify the music for you. Schenkerian analysis Schenkerian analysis is a collection of music analysis that focuses on the production of the graphic representation. This includes both analytical procedure as well as the notational style. Simply put, it analyzes tonal music which includes all chords and tones within a composition. Philosophy Philosophical analysis – a general term for the techniques used by philosophers Philosophical analysis refers to the clarification and composition of words put together and the entailed meaning behind them. Philosophical analysis dives deeper into the meaning of words and seeks to clarify that meaning by contrasting the various definitions. It is the study of reality, justification of claims, and the analysis of various concepts. Branches of philosophy include logic, justification, metaphysics, values and ethics. If questions can be answered empirically, meaning it can be answered by using the senses, then it is not considered philosophical. Non-philosophical questions also include events that happened in the past, or questions science or mathematics can answer. Analysis is the name of a prominent journal in philosophy. Psychotherapy Psychoanalysis – seeks to elucidate connections among unconscious components of patients' mental processes Transactional analysis Transactional analysis is used by therapists to try to gain a better understanding of the unconscious. It focuses on understanding and intervening human behavior. Policy Policy analysis – The use of statistical data to predict the effects of policy decisions made by governments and agencies Policy analysis includes a systematic process to find the most efficient and effective option to address the current situation. Qualitative analysis – The use of anecdotal evidence to predict the effects of policy decisions or, more generally, influence policy decisions Signal processing Finite element analysis – a computer simulation technique used in engineering analysis Independent component analysis Link quality analysis – the analysis of signal quality Path quality analysis Fourier analysis Statistics In statistics, the term analysis may refer to any method used for data analysis. Among the many such methods, some are: Analysis of variance (ANOVA) – a collection of statistical models and their associated procedures which compare means by splitting the overall observed variance into different parts Boolean analysis – a method to find deterministic dependencies between variables in a sample, mostly used in exploratory data analysis Cluster analysis – techniques for finding groups (called clusters), based on some measure of proximity or similarity Factor analysis – a method to construct models describing a data set of observed variables in terms of a smaller set of unobserved variables (called factors) Meta-analysis – combines the results of several studies that address a set of related research hypotheses Multivariate analysis – analysis of data involving several variables, such as by factor analysis, regression analysis, or principal component analysis Principal component analysis – transformation of a sample of correlated variables into uncorrelated variables (called principal components), mostly used in exploratory data analysis Regression analysis – techniques for analysing the relationships between several predictive variables and one or more outcomes in the data Scale analysis (statistics) – methods to analyse survey data by scoring responses on a numeric scale Sensitivity analysis – the study of how the variation in the output of a model depends on variations in the inputs Sequential analysis – evaluation of sampled data as it is collected, until the criterion of a stopping rule is met Spatial analysis – the study of entities using geometric or geographic properties Time-series analysis – methods that attempt to understand a sequence of data points spaced apart at uniform time intervals Other Aura analysis – a technique in which supporters of the method claim that the body's aura, or energy field is analysed Bowling analysis – Analysis of the performance of cricket players Lithic analysis – the analysis of stone tools using basic scientific techniques Lithic analysis is most often used by archeologists in determining which types of tools were used at a given time period pertaining to current artifacts discovered. Protocol analysis – a means for extracting persons' thoughts while they are performing a task See also Formal analysis Metabolism in biology Methodology Scientific method References External links Abstraction Critical thinking skills Emergence Empiricism Epistemological theories Intelligence Mathematical modeling Metaphysics of mind Methodology Ontology Philosophy of logic Rationalism Reasoning Research methods Scientific method Theory of mind

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1141

https://en.wikipedia.org/wiki/Augustin-Jean%20Fresnel

Augustin-Jean Fresnel

Augustin-Jean Fresnel ( ; ; or ; ; 10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular theory, from the late 1830s until the end of the 19th century. He is perhaps better known for inventing the catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving countless lives at sea. The simpler dioptric (purely refractive) stepped lens, first proposed by Count Buffon and independently reinvented by Fresnel, is used in screen magnifiers and in condenser lenses for overhead projectors. By expressing Huygens's principle of secondary waves and Young's principle of interference in quantitative terms, and supposing that simple colors consist of sinusoidal waves, Fresnel gave the first satisfactory explanation of diffraction by straight edges, including the first satisfactory wave-based explanation of rectilinear propagation. Part of his argument was a proof that the addition of sinusoidal functions of the same frequency but different phases is analogous to the addition of forces with different directions. By further supposing that light waves are purely transverse, Fresnel explained the nature of polarization, the mechanism of chromatic polarization, and the transmission and reflection coefficients at the interface between two transparent isotropic media. Then, by generalizing the direction-speed-polarization relation for calcite, he accounted for the directions and polarizations of the refracted rays in doubly-refractive crystals of the biaxial class (those for which Huygens's secondary wavefronts are not axisymmetric). The period between the first publication of his pure-transverse-wave hypothesis, and the submission of his first correct solution to the biaxial problem, was less than a year. Later, he coined the terms linear polarization, circular polarization, and elliptical polarization, explained how optical rotation could be understood as a difference in propagation speeds for the two directions of circular polarization, and (by allowing the reflection coefficient to be complex) accounted for the change in polarization due to total internal reflection, as exploited in the Fresnel rhomb. Defenders of the established corpuscular theory could not match his quantitative explanations of so many phenomena on so few assumptions. Fresnel had a lifelong battle with tuberculosis, to which he succumbed at the age of 39. Although he did not become a public celebrity in his lifetime, he lived just long enough to receive due recognition from his peers, including (on his deathbed) the Rumford Medal of the Royal Society of London, and his name is ubiquitous in the modern terminology of optics and waves. After the wave theory of light was subsumed by Maxwell's electromagnetic theory in the 1860s, some attention was diverted from the magnitude of Fresnel's contribution. In the period between Fresnel's unification of physical optics and Maxwell's wider unification, a contemporary authority, Humphrey Lloyd, described Fresnel's transverse-wave theory as "the noblest fabric which has ever adorned the domain of physical science, Newton's system of the universe alone excepted." Early life Family Augustin-Jean Fresnel (also called Augustin Jean or simply Augustin), born in Broglie, Normandy, on 10 May 1788, was the second of four sons of the architect Jacques Fresnel (1755–1805) and his wife Augustine, née Mérimée (1755–1833). In 1790, following the Revolution, Broglie became part of the département of Eure. The family moved twice – in 1789/90 to Cherbourg, and in 1794 to Jacques's home town of Mathieu, where Madame Fresnel would spend 25 years as a widow, outliving two of her sons. The first son, Louis (1786–1809), was admitted to the École Polytechnique, became a lieutenant in the artillery, and was killed in action at Jaca, Spain, the day before his 23rd birthday. The third, Léonor (1790–1869), followed Augustin into civil engineering, succeeded him as secretary of the Lighthouse Commission, and helped to edit his collected works. The fourth, Fulgence Fresnel (1795–1855), became a noted linguist, diplomat, and orientalist, and occasionally assisted Augustin with negotiations. Fulgence died in Bagdad in 1855 having led a mission to explore Babylon. Léonor apparently was the only one of the four who married. Their mother's younger brother, Jean François "Léonor" Mérimée (1757–1836), father of the writer Prosper Mérimée (1803–1870), was a paint artist who turned his attention to the chemistry of painting. He became the Permanent Secretary of the École des Beaux-Arts and (until 1814) a professor at the École Polytechnique, and was the initial point of contact between Augustin and the leading optical physicists of the day . Education The Fresnel brothers were initially home-schooled by their mother. The sickly Augustin was considered the slow one, not inclined to memorization; but the popular story that he hardly began to read until the age of eight is disputed. At the age of nine or ten he was undistinguished except for his ability to turn tree-branches into toy bows and guns that worked far too well, earning himself the title l'homme de génie (the man of genius) from his accomplices, and a united crackdown from their elders. In 1801, Augustin was sent to the École Centrale at Caen, as company for Louis. But Augustin lifted his performance: in late 1804 he was accepted into the École Polytechnique, being placed 17th in the entrance examination. As the detailed records of the École Polytechnique begin in 1808, we know little of Augustin's time there, except that he made few if any friends and – in spite of continuing poor health – excelled in drawing and geometry: in his first year he took a prize for his solution to a geometry problem posed by Adrien-Marie Legendre. Graduating in 1806, he then enrolled at the École Nationale des Ponts et Chaussées (National School of Bridges and Roads, also known as "ENPC" or "École des Ponts"), from which he graduated in 1809, entering the service of the Corps des Ponts et Chaussées as an ingénieur ordinaire aspirant (ordinary engineer in training). Directly or indirectly, he was to remain in the employment of the "Corps des Ponts" for the rest of his life. Religious formation Augustin Fresnel's parents were Roman Catholics of the Jansenist sect, characterized by an extreme Augustinian view of original sin. Religion took first place in the boys' home-schooling. In 1802, Mme Fresnel reportedly said: Augustin remained a Jansenist. He indeed regarded his intellectual talents as gifts from God, and considered it his duty to use them for the benefit of others. Plagued by poor health, and determined to do his duty before death thwarted him, he shunned pleasures and worked to the point of exhaustion. According to his fellow engineer Alphonse Duleau, who helped to nurse him through his final illness, Fresnel saw the study of nature as part of the study of the power and goodness of God. He placed virtue above science and genius. Yet in his last days he needed "strength of soul," not against death alone, but against "the interruption of discoveries… of which he hoped to derive useful applications." Jansenism is considered heretical by the Roman Catholic Church , and this may be part of the explanation why Fresnel, in spite of his scientific achievements and his royalist credentials, never gained a permanent academic teaching post; his only teaching appointment was at the Athénée in the winter of 1819–20. Be that as it may, the brief article on Fresnel in the old Catholic Encyclopedia does not mention his Jansenism, but describes him as "a deeply religious man and remarkable for his keen sense of duty." Engineering assignments Fresnel was initially posted to the western département of Vendée. There, in 1811, he anticipated what became known as the Solvay process for producing soda ash, except that recycling of the ammonia was not considered. That difference may explain why leading chemists, who learned of his discovery through his uncle Léonor, eventually thought it uneconomic. About 1812, Fresnel was sent to Nyons, in the southern département of Drôme, to assist with the imperial highway that was to connect Spain and Italy. It is from Nyons that we have the first evidence of his interest in optics. On 15 May 1814, while work was slack due to Napoleon's defeat, Fresnel wrote a "P.S." to his brother Léonor, saying in part: As late as 28 December he was still waiting for information, but he had received Biot's memoir by 10 February 1815. (The Institut de France had taken over the functions of the French Académie des Sciences and other académies in 1795. In 1816 the Académie des Sciences regained its name and autonomy, but remained part of the institute.) In March 1815, perceiving Napoleon's return from Elba as "an attack on civilization", Fresnel departed without leave, hastened to Toulouse and offered his services to the royalist resistance, but soon found himself on the sick list. Returning to Nyons in defeat, he was threatened and had his windows broken. During the Hundred Days he was placed on suspension, which he was eventually allowed to spend at his mother's house in Mathieu. There he used his enforced leisure to begin his optical experiments. Contributions to physical optics Historical context: From Newton to Biot The appreciation of Fresnel's reconstruction of physical optics might be assisted by an overview of the fragmented state in which he found the subject. In this subsection, optical phenomena that were unexplained or whose explanations were disputed are named in bold type. The corpuscular theory of light, favored by Isaac Newton and accepted by nearly all of Fresnel's seniors, easily explained rectilinear propagation: the corpuscles obviously moved very fast, so that their paths were very nearly straight. The wave theory, as developed by Christiaan Huygens in his Treatise on Light (1690), explained rectilinear propagation on the assumption that each point crossed by a traveling wavefront becomes the source of a secondary wavefront. Given the initial position of a traveling wavefront, any later position (according to Huygens) was the common tangent surface (envelope) of the secondary wavefronts emitted from the earlier position. As the extent of the common tangent was limited by the extent of the initial wavefront, the repeated application of Huygens's construction to a plane wavefront of limited extent (in a uniform medium) gave a straight, parallel beam. While this construction indeed predicted rectilinear propagation, it was difficult to reconcile with the common observation that wavefronts on the surface of water can bend around obstructions, and with the similar behavior of sound waves – causing Newton to maintain, to the end of his life, that if light consisted of waves it would "bend and spread every way" into the shadows. Huygens's theory neatly explained the law of ordinary reflection and the law of ordinary refraction ("Snell's law"), provided that the secondary waves traveled slower in denser media (those of higher refractive index). The corpuscular theory, with the hypothesis that the corpuscles were subject to forces acting perpendicular to surfaces, explained the same laws equally well, albeit with the implication that light traveled faster in denser media; that implication was wrong, but could not be directly disproven with the technology of Newton's time or even Fresnel's time . Similarly inconclusive was stellar aberration—that is, the apparent change in the position of a star due to the velocity of the earth across the line of sight (not to be confused with stellar parallax, which is due to the displacement of the earth across the line of sight). Identified by James Bradley in 1728, stellar aberration was widely taken as confirmation of the corpuscular theory. But it was equally compatible with the wave theory, as Euler noted in 1746 – tacitly assuming that the aether (the supposed wave-bearing medium) near the earth was not disturbed by the motion of the earth. The outstanding strength of Huygens's theory was his explanation of the birefringence (double refraction) of "Iceland crystal" (transparent calcite), on the assumption that the secondary waves are spherical for the ordinary refraction (which satisfies Snell's law) and spheroidal for the extraordinary refraction (which does not). In general, Huygens's common-tangent construction implies that rays are paths of least time between successive positions of the wavefront, in accordance with Fermat's principle. In the special case of isotropic media, the secondary wavefronts must be spherical, and Huygens's construction then implies that the rays are perpendicular to the wavefront; indeed, the law of ordinary refraction can be separately derived from that premise, as Ignace-Gaston Pardies did before Huygens. Although Newton rejected the wave theory, he noticed its potential to explain colors, including the colors of "thin plates" (e.g., "Newton's rings", and the colors of skylight reflected in soap bubbles), on the assumption that light consists of periodic waves, with the lowest frequencies (longest wavelengths) at the red end of the spectrum, and the highest frequencies (shortest wavelengths) at the violet end. In 1672 he published a heavy hint to that effect, but contemporary supporters of the wave theory failed to act on it: Robert Hooke treated light as a periodic sequence of pulses but did not use frequency as the criterion of color, while Huygens treated the waves as individual pulses without any periodicity; and Pardies died young in 1673. Newton himself tried to explain colors of thin plates using the corpuscular theory, by supposing that his corpuscles had the wavelike property of alternating between "fits of easy transmission" and "fits of easy reflection", the distance between like "fits" depending on the color and the medium and, awkwardly, on the angle of refraction or reflection into that medium. More awkwardly still, this theory required thin plates to reflect only at the back surface, although thick plates manifestly reflected also at the front surface. It was not until 1801 that Thomas Young, in the Bakerian Lecture for that year, cited Newton's hint, and accounted for the colors of a thin plate as the combined effect of the front and back reflections, which reinforce or cancel each other according to the wavelength and the thickness. Young similarly explained the colors of "striated surfaces" (e.g., gratings) as the wavelength-dependent reinforcement or cancellation of reflections from adjacent lines. He described this reinforcement or cancellation as interference. Neither Newton nor Huygens satisfactorily explained diffraction—the blurring and fringing of shadows where, according to rectilinear propagation, they ought to be sharp. Newton, who called diffraction "inflexion", supposed that rays of light passing close to obstacles were bent ("inflected"); but his explanation was only qualitative. Huygens's common-tangent construction, without modifications, could not accommodate diffraction at all. Two such modifications were proposed by Young in the same 1801 Bakerian Lecture: first, that the secondary waves near the edge of an obstacle could diverge into the shadow, but only weakly, due to limited reinforcement from other secondary waves; and second, that diffraction by an edge was caused by interference between two rays: one reflected off the edge, and the other inflected while passing near the edge. The latter ray would be undeviated if sufficiently far from the edge, but Young did not elaborate on that case. These were the earliest suggestions that the degree of diffraction depends on wavelength. Later, in the 1803 Bakerian Lecture, Young ceased to regard inflection as a separate phenomenon, and produced evidence that diffraction fringes inside the shadow of a narrow obstacle were due to interference: when the light from one side was blocked, the internal fringes disappeared. But Young was alone in such efforts until Fresnel entered the field. Huygens, in his investigation of double refraction, noticed something that he could not explain: when light passes through two similarly oriented calcite crystals at normal incidence, the ordinary ray emerging from the first crystal suffers only the ordinary refraction in the second, while the extraordinary ray emerging from the first suffers only the extraordinary refraction in the second; but when the second crystal is rotated 90° about the incident rays, the roles are interchanged, so that the ordinary ray emerging from the first crystal suffers only the extraordinary refraction in the second, and vice versa. This discovery gave Newton another reason to reject the wave theory: rays of light evidently had "sides". Corpuscles could have sides (or poles, as they would later be called); but waves of light could not, because (so it seemed) any such waves would need to be longitudinal (with vibrations in the direction of propagation). Newton offered an alternative "Rule" for the extraordinary refraction, which rode on his authority through the 18th century, although he made "no known attempt to deduce it from any principles of optics, corpuscular or otherwise." In 1808, the extraordinary refraction of calcite was investigated experimentally, with unprecedented accuracy, by Étienne-Louis Malus, and found to be consistent with Huygens's spheroid construction, not Newton's "Rule". Malus, encouraged by Pierre-Simon Laplace, then sought to explain this law in corpuscular terms: from the known relation between the incident and refracted ray directions, Malus derived the corpuscular velocity (as a function of direction) that would satisfy Maupertuis's "least action" principle. But, as Young pointed out, the existence of such a velocity law was guaranteed by Huygens's spheroid, because Huygens's construction leads to Fermat's principle, which becomes Maupertuis's principle if the ray speed is replaced by the reciprocal of the particle speed! The corpuscularists had not found a force law that would yield the alleged velocity law, except by a circular argument in which a force acting at the surface of the crystal inexplicably depended on the direction of the (possibly subsequent) velocity within the crystal. Worse, it was doubtful that any such force would satisfy the conditions of Maupertuis's principle. In contrast, Young proceeded to show that "a medium more easily compressible in one direction than in any direction perpendicular to it, as if it consisted of an infinite number of parallel plates connected by a substance somewhat less elastic" admits spheroidal longitudinal wavefronts, as Huygens supposed. But Malus, in the midst of his experiments on double refraction, noticed something else: when a ray of light is reflected off a non-metallic surface at the appropriate angle, it behaves like one of the two rays emerging from a calcite crystal. It was Malus who coined the term polarization to describe this behavior, although the polarizing angle became known as Brewster's angle after its dependence on the refractive index was determined experimentally by David Brewster in 1815. Malus also introduced the term plane of polarization. In the case of polarization by reflection, his "plane of polarization" was the plane of the incident and reflected rays; in modern terms, this is the plane normal to the electric vibration. In 1809, Malus further discovered that the intensity of light passing through two polarizers is proportional to the squared cosine of the angle between their planes of polarization (Malus's law), whether the polarizers work by reflection or double refraction, and that all birefringent crystals produce both extraordinary refraction and polarization. As the corpuscularists started trying to explain these things in terms of polar "molecules" of light, the wave-theorists had no working hypothesis on the nature of polarization, prompting Young to remark that Malus's observations "present greater difficulties to the advocates of the undulatory theory than any other facts with which we are acquainted." Malus died in February 1812, at the age of 36, shortly after receiving the Rumford Medal for his work on polarization. In August 1811, François Arago reported that if a thin plate of mica was viewed against a white polarized backlight through a calcite crystal, the two images of the mica were of complementary colors (the overlap having the same color as the background). The light emerging from the mica was "depolarized" in the sense that there was no orientation of the calcite that made one image disappear; yet it was not ordinary ("unpolarized") light, for which the two images would be of the same color. Rotating the calcite around the line of sight changed the colors, though they remained complementary. Rotating the mica changed the saturation (not the hue) of the colors. This phenomenon became known as chromatic polarization. Replacing the mica with a much thicker plate of quartz, with its faces perpendicular to the optic axis (the axis of Huygens's spheroid or Malus's velocity function), produced a similar effect, except that rotating the quartz made no difference. Arago tried to explain his observations in corpuscular terms. In 1812, as Arago pursued further qualitative experiments and other commitments, Jean-Baptiste Biot reworked the same ground using a gypsum lamina in place of the mica, and found empirical formulae for the intensities of the ordinary and extraordinary images. The formulae contained two coefficients, supposedly representing colors of rays "affected" and "unaffected" by the plate – the "affected" rays being of the same color mix as those reflected by amorphous thin plates of proportional, but lesser, thickness. Arago protested, declaring that he had made some of the same discoveries but had not had time to write them up. In fact the overlap between Arago's work and Biot's was minimal, Arago's being only qualitative and wider in scope (attempting to include polarization by reflection). But the dispute triggered a notorious falling-out between the two men. Later that year, Biot tried to explain the observations as an oscillation of the alignment of the "affected" corpuscles at a frequency proportional to that of Newton's "fits", due to forces depending on the alignment. This theory became known as mobile polarization. To reconcile his results with a sinusoidal oscillation, Biot had to suppose that the corpuscles emerged with one of two permitted orientations, namely the extremes of the oscillation, with probabilities depending on the phase of the oscillation. Corpuscular optics was becoming expensive on assumptions. But in 1813, Biot reported that the case of quartz was simpler: the observable phenomenon (now called optical rotation or optical activity or sometimes rotary polarization) was a gradual rotation of the polarization direction with distance, and could be explained by a corresponding rotation (not oscillation) of the corpuscles. Early in 1814, reviewing Biot's work on chromatic polarization, Young noted that the periodicity of the color as a function of the plate thickness – including the factor by which the period exceeded that for a reflective thin plate, and even the effect of obliquity of the plate (but not the role of polarization)—could be explained by the wave theory in terms of the different propagation times of the ordinary and extraordinary waves through the plate. But Young was then the only public defender of the wave theory. In summary, in the spring of 1814, as Fresnel tried in vain to guess what polarization was, the corpuscularists thought that they knew, while the wave-theorists (if we may use the plural) literally had no idea. Both theories claimed to explain rectilinear propagation, but the wave explanation was overwhelmingly regarded as unconvincing. The corpuscular theory could not rigorously link double refraction to surface forces; the wave theory could not yet link it to polarization. The corpuscular theory was weak on thin plates and silent on gratings; the wave theory was strong on both, but under-appreciated. Concerning diffraction, the corpuscular theory did not yield quantitative predictions, while the wave theory had begun to do so by considering diffraction as a manifestation of interference, but had only considered two rays at a time. Only the corpuscular theory gave even a vague insight into Brewster's angle, Malus's law, or optical rotation. Concerning chromatic polarization, the wave theory explained the periodicity far better than the corpuscular theory, but had nothing to say about the role of polarization; and its explanation of the periodicity was largely ignored. And Arago had founded the study of chromatic polarization, only to lose the lead, controversially, to Biot. Such were the circumstances in which Arago first heard of Fresnel's interest in optics. Rêveries Fresnel's letters from later in 1814 reveal his interest in the wave theory, including his awareness that it explained the constancy of the speed of light and was at least compatible with stellar aberration. Eventually he compiled what he called his rêveries (musings) into an essay and submitted it via Léonor Mérimée to André-Marie Ampère, who did not respond directly. But on 19 December, Mérimée dined with Ampère and Arago, with whom he was acquainted through the École Polytechnique; and Arago promised to look at Fresnel's essay. In mid 1815, on his way home to Mathieu to serve his suspension, Fresnel met Arago in Paris and spoke of the wave theory and stellar aberration. He was informed that he was trying to break down open doors ("il enfonçait des portes ouvertes"), and directed to classical works on optics. Diffraction First attempt (1815) On 12 July 1815, as Fresnel was about to leave Paris, Arago left him a note on a new topic: Fresnel would not have ready access to these works outside Paris, and could not read English. But, in Mathieu – with a point-source of light made by focusing sunlight with a drop of honey, a crude micrometer of his own construction, and supporting apparatus made by a local locksmith – he began his own experiments. His technique was novel: whereas earlier investigators had projected the fringes onto a screen, Fresnel soon abandoned the screen and observed the fringes in space, through a lens with the micrometer at its focus, allowing more accurate measurements while requiring less light. Later in July, after Napoleon's final defeat, Fresnel was reinstated with the advantage of having backed the winning side. He requested a two-month leave of absence, which was readily granted because roadworks were in abeyance. On 23 September he wrote to Arago, beginning "I think I have found the explanation and the law of colored fringes which one notices in the shadows of bodies illuminated by a luminous point." In the same paragraph, however, Fresnel implicitly acknowledged doubt about the novelty of his work: noting that he would need to incur some expense in order to improve his measurements, he wanted to know "whether this is not useless, and whether the law of diffraction has not already been established by sufficiently exact experiments." He explained that he had not yet had a chance to acquire the items on his reading lists, with the apparent exception of "Young's book", which he could not understand without his brother's help.  Not surprisingly, he had retraced many of Young's steps. In a memoir sent to the institute on 15 October 1815, Fresnel mapped the external and internal fringes in the shadow of a wire. He noticed, like Young before him, that the internal fringes disappeared when the light from one side was blocked, and concluded that "the vibrations of two rays that cross each other under a very small angle can contradict each other…" But, whereas Young took the disappearance of the internal fringes as confirmation of the principle of interference, Fresnel reported that it was the internal fringes that first drew his attention to the principle. To explain the diffraction pattern, Fresnel constructed the internal fringes by considering the intersections of circular wavefronts emitted from the two edges of the obstruction, and the external fringes by considering the intersections between direct waves and waves reflected off the nearer edge. For the external fringes, to obtain tolerable agreement with observation, he had to suppose that the reflected wave was inverted; and he noted that the predicted paths of the fringes were hyperbolic. In the part of the memoir that most clearly surpassed Young, Fresnel explained the ordinary laws of reflection and refraction in terms of interference, noting that if two parallel rays were reflected or refracted at other than the prescribed angle, they would no longer have the same phase in a common perpendicular plane, and every vibration would be cancelled by a nearby vibration. He noted that his explanation was valid provided that the surface irregularities were much smaller than the wavelength. On 10 November, Fresnel sent a supplementary note dealing with Newton's rings and with gratings, including, for the first time, transmission gratings – although in that case the interfering rays were still assumed to be "inflected", and the experimental verification was inadequate because it used only two threads. As Fresnel was not a member of the institute, the fate of his memoir depended heavily on the report of a single member. The reporter for Fresnel's memoir turned out to be Arago (with Poinsot as the other reviewer). On 8 November, Arago wrote to Fresnel: Fresnel was troubled, wanting to know more precisely where he had collided with Young. Concerning the curved paths of the "colored bands", Young had noted the hyperbolic paths of the fringes in the two-source interference pattern, corresponding roughly to Fresnel's internal fringes, and had described the hyperbolic fringes that appear on the screen within rectangular shadows. He had not mentioned the curved paths of the external fringes of a shadow; but, as he later explained, that was because Newton had already done so. Newton evidently thought the fringes were caustics. Thus Arago erred in his belief that the curved paths of the fringes were fundamentally incompatible with the corpuscular theory. Arago's letter went on to request more data on the external fringes. Fresnel complied, until he exhausted his leave and was assigned to Rennes in the département of Ille-et-Vilaine. At this point Arago interceded with Gaspard de Prony, head of the École des Ponts, who wrote to Louis-Mathieu Molé, head of the Corps des Ponts, suggesting that the progress of science and the prestige of the Corps would be enhanced if Fresnel could come to Paris for a time. He arrived in March 1816, and his leave was subsequently extended through the middle of the year. Meanwhile, in an experiment reported on 26 February 1816, Arago verified Fresnel's prediction that the internal fringes were shifted if the rays on one side of the obstacle passed through a thin glass lamina. Fresnel correctly attributed this phenomenon to the lower wave velocity in the glass. Arago later used a similar argument to explain the colors in the scintillation of stars. Fresnel's updated memoir was eventually published in the March 1816 issue of Annales de Chimie et de Physique, of which Arago had recently become co-editor. That issue did not actually appear until May. In March, Fresnel already had competition: Biot read a memoir on diffraction by himself and his student Claude Pouillet, containing copious data and arguing that the regularity of diffraction fringes, like the regularity of Newton's rings, must be linked to Newton's "fits". But the new link was not rigorous, and Pouillet himself would become a distinguished early adopter of the wave theory. "Efficacious ray", double-mirror experiment (1816) On 24 May 1816, Fresnel wrote to Young (in French), acknowledging how little of his own memoir was new. But in a "supplement" signed on 14 July and read the next day, Fresnel noted that the internal fringes were more accurately predicted by supposing that the two interfering rays came from some distance outside the edges of the obstacle. To explain this, he divided the incident wavefront at the obstacle into what we now call Fresnel zones, such that the secondary waves from each zone were spread over half a cycle when they arrived at the observation point. The zones on one side of the obstacle largely canceled out in pairs, except the first zone, which was represented by an "efficacious ray". This approach worked for the internal fringes, but the superposition of the efficacious ray and the direct ray did not work for the external fringes. The contribution from the "efficacious ray" was thought to be only partly canceled, for reasons involving the dynamics of the medium: where the wavefront was continuous, symmetry forbade oblique vibrations; but near the obstacle that truncated the wavefront, the asymmetry allowed some sideways vibration towards the geometric shadow. This argument showed that Fresnel had not (yet) fully accepted Huygens's principle, which would have permitted oblique radiation from all portions of the front. In the same supplement, Fresnel described his well-known double mirror, comprising two flat mirrors joined at an angle of slightly less than 180°, with which he produced a two-slit interference pattern from two virtual images of the same slit. A conventional double-slit experiment required a preliminary single slit to ensure that the light falling on the double slit was coherent (synchronized). In Fresnel's version, the preliminary single slit was retained, and the double slit was replaced by the double mirror – which bore no physical resemblance to the double slit and yet performed the same function. This result (which had been announced by Arago in the March issue of the Annales) made it hard to believe that the two-slit pattern had anything to do with corpuscles being deflected as they passed near the edges of the slits. But 1816 was the "Year Without a Summer": crops failed; hungry farming families lined the streets of Rennes; the central government organized "charity workhouses" for the needy; and in October, Fresnel was sent back to Ille-et-Vilaine to supervise charity workers in addition to his regular road crew. According to Arago, Fresnel's letters from December 1816 reveal his consequent anxiety. To Arago he complained of being "tormented by the worries of surveillance, and the need to reprimand…" And to Mérimée he wrote: "I find nothing more tiresome than having to manage other men, and I admit that I have no idea what I'm doing." Prize memoir (1818) and sequel On 17 March 1817, the Académie des Sciences announced that diffraction would be the topic for the biannual physics Grand Prix to be awarded in 1819. The deadline for entries was set at 1 August 1818 to allow time for replication of experiments. Although the wording of the problem referred to rays and inflection and did not invite wave-based solutions, Arago and Ampère encouraged Fresnel to enter. In the fall of 1817, Fresnel, supported by de Prony, obtained a leave of absence from the new head of the Corp des Ponts, Louis Becquey, and returned to Paris. He resumed his engineering duties in the spring of 1818; but from then on he was based in Paris, first on the Canal de l'Ourcq, and then (from May 1819) with the cadastre of the pavements. On 15 January 1818, in a different context (revisited below), Fresnel showed that the addition of sinusoidal functions of the same frequency but different phases is analogous to the addition of forces with different directions. His method was similar to the phasor representation, except that the "forces" were plane vectors rather than complex numbers; they could be added, and multiplied by scalars, but not (yet) multiplied and divided by each other. The explanation was algebraic rather than geometric. Knowledge of this method was assumed in a preliminary note on diffraction, dated 19 April 1818 and deposited on 20 April, in which Fresnel outlined the elementary theory of diffraction as found in modern textbooks. He restated Huygens's principle in combination with the superposition principle, saying that the vibration at each point on a wavefront is the sum of the vibrations that would be sent to it at that moment by all the elements of the wavefront in any of its previous positions, all elements acting separately . For a wavefront partly obstructed in a previous position, the summation was to be carried out over the unobstructed portion. In directions other than the normal to the primary wavefront, the secondary waves were weakened due to obliquity, but weakened much more by destructive interference, so that the effect of obliquity alone could be ignored. For diffraction by a straight edge, the intensity as a function of distance from the geometric shadow could then be expressed with sufficient accuracy in terms of what are now called the normalized Fresnel integrals: The same note included a table of the integrals, for an upper limit ranging from 0 to 5.1 in steps of 0.1, computed with a mean error of 0.0003, plus a smaller table of maxima and minima of the resulting intensity. In his final "Memoir on the diffraction of light", deposited on 29 July and bearing the Latin epigraph "Natura simplex et fecunda" ("Nature simple and fertile"), Fresnel slightly expanded the two tables without changing the existing figures, except for a correction to the first minimum of intensity. For completeness, he repeated his solution to "the problem of interference", whereby sinusoidal functions are added like vectors. He acknowledged the directionality of the secondary sources and the variation in their distances from the observation point, chiefly to explain why these things make negligible difference in the context, provided of course that the secondary sources do not radiate in the retrograde direction. Then, applying his theory of interference to the secondary waves, he expressed the intensity of light diffracted by a single straight edge (half-plane) in terms of integrals which involved the dimensions of the problem, but which could be converted to the normalized forms above. With reference to the integrals, he explained the calculation of the maxima and minima of the intensity (external fringes), and noted that the calculated intensity falls very rapidly as one moves into the geometric shadow. The last result, as Olivier Darrigol says, "amounts to a proof of the rectilinear propagation of light in the wave theory, indeed the first proof that a modern physicist would still accept." For the experimental testing of his calculations, Fresnel used red light with a wavelength of 638nm, which he deduced from the diffraction pattern in the simple case in which light incident on a single slit was focused by a cylindrical lens. For a variety of distances from the source to the obstacle and from the obstacle to the field point, he compared the calculated and observed positions of the fringes for diffraction by a half-plane, a slit, and a narrow strip – concentrating on the minima, which were visually sharper than the maxima. For the slit and the strip, he could not use the previously computed table of maxima and minima; for each combination of dimensions, the intensity had to be expressed in terms of sums or differences of Fresnel integrals and calculated from the table of integrals, and the extrema had to be calculated anew. The agreement between calculation and measurement was better than 1.5% in almost every case. Near the end of the memoir, Fresnel summed up the difference between Huygens's use of secondary waves and his own: whereas Huygens says there is light only where the secondary waves exactly agree, Fresnel says there is complete darkness only where the secondary waves exactly cancel out. The judging committee comprised Laplace, Biot, and Poisson (all corpuscularists), Gay-Lussac (uncommitted), and Arago, who eventually wrote the committee's report. Although entries in the competition were supposed to be anonymous to the judges, Fresnel's must have been recognizable by the content. There was only one other entry, of which neither the manuscript nor any record of the author has survived. That entry (identified as "no.1") was mentioned only in the last paragraph of the judges' report, noting that the author had shown ignorance of the relevant earlier works of Young and Fresnel, used insufficiently precise methods of observation, overlooked known phenomena, and made obvious errors. In the words of John Worrall, "The competition facing Fresnel could hardly have been less stiff." We may infer that the committee had only two options: award the prize to Fresnel ("no. 2"), or withhold it. The committee deliberated into the new year. Then Poisson, exploiting a case in which Fresnel's theory gave easy integrals, predicted that if a circular obstacle were illuminated by a point-source, there should be (according to the theory) a bright spot in the center of the shadow, illuminated as brightly as the exterior. This seems to have been intended as a reductio ad absurdum. Arago, undeterred, assembled an experiment with an obstacle 2mm in diameter – and there, in the center of the shadow, was Poisson's spot. The unanimous report of the committee, read at the meeting of the Académie on 15 March 1819, awarded the prize to "the memoir marked no. 2, and bearing as epigraph: Natura simplex et fecunda." At the same meeting, after the judgment was delivered, the president of the Académie opened a sealed note accompanying the memoir, revealing the author as Fresnel. The award was announced at the public meeting of the Académie a week later, on 22 March. Arago's verification of Poisson's counter-intuitive prediction passed into folklore as if it had decided the prize. That view, however, is not supported by the judges' report, which gave the matter only two sentences in the penultimate paragraph. Neither did Fresnel's triumph immediately convert Laplace, Biot, and Poisson to the wave theory, for at least four reasons. First, although the professionalization of science in France had established common standards, it was one thing to acknowledge a piece of research as meeting those standards, and another thing to regard it as conclusive. Second, it was possible to interpret Fresnel's integrals as rules for combining rays. Arago even encouraged that interpretation, presumably in order to minimize resistance to Fresnel's ideas. Even Biot began teaching the Huygens-Fresnel principle without committing himself to a wave basis. Third, Fresnel's theory did not adequately explain the mechanism of generation of secondary waves or why they had any significant angular spread; this issue particularly bothered Poisson. Fourth, the question that most exercised optical physicists at that time was not diffraction, but polarization – on which Fresnel had been working, but was yet to make his critical breakthrough. Polarization Background: Emissionism and selectionism An emission theory of light was one that regarded the propagation of light as the transport of some kind of matter. While the corpuscular theory was obviously an emission theory, the converse did not follow: in principle, one could be an emissionist without being a corpuscularist. This was convenient because, beyond the ordinary laws of reflection and refraction, emissionists never managed to make testable quantitative predictions from a theory of forces acting on corpuscles of light. But they did make quantitative predictions from the premises that rays were countable objects, which were conserved in their interactions with matter (except absorbent media), and which had particular orientations with respect to their directions of propagation. According to this framework, polarization and the related phenomena of double refraction and partial reflection involved altering the orientations of the rays and/or selecting them according to orientation, and the state of polarization of a beam (a bundle of rays) was a question of how many rays were in what orientations: in a fully polarized beam, the orientations were all the same. This approach, which Jed Buchwald has called selectionism, was pioneered by Malus and diligently pursued by Biot. Fresnel, in contrast, decided to introduce polarization into interference experiments. Interference of polarized light, chromatic polarization (1816–21) In July or August 1816, Fresnel discovered that when a birefringent crystal produced two images of a single slit, he could not obtain the usual two-slit interference pattern, even if he compensated for the different propagation times. A more general experiment, suggested by Arago, found that if the two beams of a double-slit device were separately polarized, the interference pattern appeared and disappeared as the polarization of one beam was rotated, giving full interference for parallel polarizations, but no interference for perpendicular polarizations . These experiments, among others, were eventually reported in a brief memoir published in 1819 and later translated into English. In a memoir drafted on 30 August 1816 and revised on 6 October, Fresnel reported an experiment in which he placed two matching thin laminae in a double-slit apparatus – one over each slit, with their optic axes perpendicular – and obtained two interference patterns offset in opposite directions, with perpendicular polarizations. This, in combination with the previous findings, meant that each lamina split the incident light into perpendicularly polarized components with different velocities – just like a normal (thick) birefringent crystal, and contrary to Biot's "mobile polarization" hypothesis. Accordingly, in the same memoir, Fresnel offered his first attempt at a wave theory of chromatic polarization. When polarized light passed through a crystal lamina, it was split into ordinary and extraordinary waves (with intensities described by Malus's law), and these were perpendicularly polarized and therefore did not interfere, so that no colors were produced (yet). But if they then passed through an analyzer (second polarizer), their polarizations were brought into alignment (with intensities again modified according to Malus's law), and they would interfere. This explanation, by itself, predicts that if the analyzer is rotated 90°, the ordinary and extraordinary waves simply switch roles, so that if the analyzer takes the form of a calcite crystal, the two images of the lamina should be of the same hue (this issue is revisited below). But in fact, as Arago and Biot had found, they are of complementary colors. To correct the prediction, Fresnel proposed a phase-inversion rule whereby one of the constituent waves of one of the two images suffered an additional 180° phase shift on its way through the lamina. This inversion was a weakness in the theory relative to Biot's, as Fresnel acknowledged, although the rule specified which of the two images had the inverted wave. Moreover, Fresnel could deal only with special cases, because he had not yet solved the problem of superposing sinusoidal functions with arbitrary phase differences due to propagation at different velocities through the lamina. He solved that problem in a "supplement" signed on 15 January 1818 (mentioned above). In the same document, he accommodated Malus's law by proposing an underlying law: that if polarized light is incident on a birefringent crystal with its optic axis at an angle θ to the "plane of polarization", the ordinary and extraordinary vibrations (as functions of time) are scaled by the factors cosθ and sinθ, respectively. Although modern readers easily interpret these factors in terms of perpendicular components of a transverse oscillation, Fresnel did not (yet) explain them that way. Hence he still needed the phase-inversion rule. He applied all these principles to a case of chromatic polarization not covered by Biot's formulae, involving two successive laminae with axes separated by 45°, and obtained predictions that disagreed with Biot's experiments (except in special cases) but agreed with his own. Fresnel applied the same principles to the standard case of chromatic polarization, in which one birefringent lamina was sliced parallel to its axis and placed between a polarizer and an analyzer. If the analyzer took the form of a thick calcite crystal with its axis in the plane of polarization, Fresnel predicted that the intensities of the ordinary and extraordinary images of the lamina were respectively proportional to where is the angle from the initial plane of polarization to the optic axis of the lamina, is the angle from the initial plane of polarization to the plane of polarization of the final ordinary image, and is the phase lag of the extraordinary wave relative to the ordinary wave due to the difference in propagation times through the lamina. The terms in are the frequency-dependent terms and explain why the lamina must be thin in order to produce discernible colors: if the lamina is too thick, will pass through too many cycles as the frequency varies through the visible range, and the eye (which divides the visible spectrum into only three bands) will not be able to resolve the cycles. From these equations it is easily verified that for all so that the colors are complementary. Without the phase-inversion rule, there would be a plus sign in front of the last term in the second equation, so that the -dependent term would be the same in both equations, implying (incorrectly) that the colors were of the same hue. These equations were included in an undated note that Fresnel gave to Biot, to which Biot added a few lines of his own. If we substitute  and  then Fresnel's formulae can be rewritten as which are none other than Biot's empirical formulae of 1812, except that Biot interpreted and as the "unaffected" and "affected" selections of the rays incident on the lamina. If Biot's substitutions were accurate, they would imply that his experimental results were more fully explained by Fresnel's theory than by his own. Arago delayed reporting on Fresnel's works on chromatic polarization until June 1821, when he used them in a broad attack on Biot's theory. In his written response, Biot protested that Arago's attack went beyond the proper scope of a report on the nominated works of Fresnel. But Biot also claimed that the substitutions for and and therefore Fresnel's expressions for and were empirically wrong because when Fresnel's intensities of spectral colors were mixed according to Newton's rules, the squared cosine and sine functions varied too smoothly to account for the observed sequence of colors. That claim drew a written reply from Fresnel, who disputed whether the colors changed as abruptly as Biot claimed, and whether the human eye could judge color with sufficient objectivity for the purpose. On the latter question, Fresnel pointed out that different observers may give different names to the same color. Furthermore, he said, a single observer can only compare colors side by side; and even if they are judged to be the same, the identity is of sensation, not necessarily of composition. Fresnel's oldest and strongest point – that thin crystals were subject to the same laws as thick ones and did not need or allow a separate theory – Biot left unanswered.  Arago and Fresnel were seen to have won the debate. Moreover, by this time Fresnel had a new, simpler explanation of his equations on chromatic polarization. Breakthrough: Pure transverse waves (1821) In the draft memoir of 30 August 1816, Fresnel mentioned two hypotheses – one of which he attributed to Ampère – by which the non-interference of orthogonally-polarized beams could be explained if polarized light waves were partly transverse. But Fresnel could not develop either of these ideas into a comprehensive theory. As early as September 1816, according to his later account, he realized that the non-interference of orthogonally-polarized beams, together with the phase-inversion rule in chromatic polarization, would be most easily explained if the waves were purely transverse, and Ampère "had the same thought" on the phase-inversion rule. But that would raise a new difficulty: as natural light seemed to be unpolarized and its waves were therefore presumed to be longitudinal, one would need to explain how the longitudinal component of vibration disappeared on polarization, and why it did not reappear when polarized light was reflected or refracted obliquely by a glass plate. Independently, on 12 January 1817, Young wrote to Arago (in English) noting that a transverse vibration would constitute a polarization, and that if two longitudinal waves crossed at a significant angle, they could not cancel without leaving a residual transverse vibration. Young repeated this idea in an article published in a supplement to the Encyclopædia Britannica in February 1818, in which he added that Malus's law would be explained if polarization consisted in a transverse motion. Thus Fresnel, by his own testimony, may not have been the first person to suspect that light waves could have a transverse component, or that polarized waves were exclusively transverse. And it was Young, not Fresnel, who first published the idea that polarization depends on the orientation of a transverse vibration. But these incomplete theories had not reconciled the nature of polarization with the apparent existence of unpolarized light; that achievement was to be Fresnel's alone. In a note that Buchwald dates in the summer of 1818, Fresnel entertained the idea that unpolarized waves could have vibrations of the same energy and obliquity, with their orientations distributed uniformly about the wave-normal, and that the degree of polarization was the degree of non-uniformity in the distribution. Two pages later he noted, apparently for the first time in writing, that his phase-inversion rule and the non-interference of orthogonally-polarized beams would be easily explained if the vibrations of fully polarized waves were "perpendicular to the normal to the wave"—that is, purely transverse. But if he could account for lack of polarization by averaging out the transverse component, he did not also need to assume a longitudinal component. It was enough to suppose that light waves are purely transverse, hence always polarized in the sense of having a particular transverse orientation, and that the "unpolarized" state of natural or "direct" light is due to rapid and random variations in that orientation, in which case two coherent portions of "unpolarized" light will still interfere because their orientations will be synchronized. It is not known exactly when Fresnel made this last step, because there is no relevant documentation from 1820 or early 1821 (perhaps because he was too busy working on lighthouse-lens prototypes; see below). But he first published the idea in a paper on "Calcul des teintes…" ("calculation of the tints…"), serialized in Arago's Annales for May, June, and July 1821. In the first installment, Fresnel described "direct" (unpolarized) light as "the rapid succession of systems of waves polarized in all directions", and gave what is essentially the modern explanation of chromatic polarization, albeit in terms of the analogy between polarization and the resolution of forces in a plane, mentioning transverse waves only in a footnote. The introduction of transverse waves into the main argument was delayed to the second installment, in which he revealed the suspicion that he and Ampère had harbored since 1816, and the difficulty it raised. He continued: According to this new view, he wrote, "the act of polarization consists not in creating these transverse movements, but in decomposing them into two fixed perpendicular directions and in separating the two components". While selectionists could insist on interpreting Fresnel's diffraction integrals in terms of discrete, countable rays, they could not do the same with his theory of polarization. For a selectionist, the state of polarization of a beam concerned the distribution of orientations over the population of rays, and that distribution was presumed to be static. For Fresnel, the state of polarization of a beam concerned the variation of a displacement over time. That displacement might be constrained but was not static, and rays were geometric constructions, not countable objects. The conceptual gap between the wave theory and selectionism had become unbridgeable. The other difficulty posed by pure transverse waves, of course, was the apparent implication that the aether was an elastic solid, except that, unlike other elastic solids, it was incapable of transmitting longitudinal waves. The wave theory was cheap on assumptions, but its latest assumption was expensive on credulity. If that assumption was to be widely entertained, its explanatory power would need to be impressive. Partial reflection (1821) In the second installment of "Calcul des teintes" (June 1821), Fresnel supposed, by analogy with sound waves, that the density of the aether in a refractive medium was inversely proportional to the square of the wave velocity, and therefore directly proportional to the square of the refractive index. For reflection and refraction at the surface between two isotropic media of different indices, Fresnel decomposed the transverse vibrations into two perpendicular components, now known as the s and p components, which are parallel to the surface and the plane of incidence, respectively; in other words, the s and p components are respectively square and parallel to the plane of incidence. For the s component, Fresnel supposed that the interaction between the two media was analogous to an elastic collision, and obtained a formula for what we now call the reflectivity: the ratio of the reflected intensity to the incident intensity. The predicted reflectivity was non-zero at all angles. The third installment (July 1821) was a short "postscript" in which Fresnel announced that he had found, by a "mechanical solution", a formula for the reflectivity of the p component, which predicted that the reflectivity was zero at the Brewster angle. So polarization by reflection had been accounted for – but with the proviso that the direction of vibration in Fresnel's model was perpendicular to the plane of polarization as defined by Malus. (On the ensuing controversy, see Plane of polarization.) The technology of the time did not allow the s and p reflectivities to be measured accurately enough to test Fresnel's formulae at arbitrary angles of incidence. But the formulae could be rewritten in terms of what we now call the reflection coefficient: the signed ratio of the reflected amplitude to the incident amplitude. Then, if the plane of polarization of the incident ray was at 45° to the plane of incidence, the tangent of the corresponding angle for the reflected ray was obtainable from the ratio of the two reflection coefficients, and this angle could be measured. Fresnel had measured it for a range of angles of incidence, for glass and water, and the agreement between the calculated and measured angles was better than 1.5° in all cases. Fresnel gave details of the "mechanical solution" in a memoir read to the Académie des Sciences on 7 January 1823. Conservation of energy was combined with continuity of the tangential vibration at the interface. The resulting formulae for the reflection coefficients and reflectivities became known as the Fresnel equations. The reflection coefficients for the s and p polarizations are most succinctly expressed as and where and are the angles of incidence and refraction; these equations are known respectively as Fresnel's sine law and Fresnel's tangent law. By allowing the coefficients to be complex, Fresnel even accounted for the different phase shifts of the s and p components due to total internal reflection. This success inspired James MacCullagh and Augustin-Louis Cauchy, beginning in 1836, to analyze reflection from metals by using the Fresnel equations with a complex refractive index. The same technique is applicable to non-metallic opaque media. With these generalizations, the Fresnel equations can predict the appearance of a wide variety of objects under illumination – for example, in computer graphics . Circular and elliptical polarization, optical rotation (1822) In a memoir dated 9 December 1822, Fresnel coined the terms linear polarization (French: polarisation rectiligne) for the simple case in which the perpendicular components of vibration are in phase or 180° out of phase, circular polarization for the case in which they are of equal magnitude and a quarter-cycle (±90°) out of phase, and elliptical polarization for other cases in which the two components have a fixed amplitude ratio and a fixed phase difference. He then explained how optical rotation could be understood as a species of birefringence. Linearly-polarized light could be resolved into two circularly-polarized components rotating in opposite directions. If these components propagated at slightly different speeds, the phase difference between them – and therefore the direction of their linearly-polarized resultant – would vary continuously with distance. These concepts called for a redefinition of the distinction between polarized and unpolarized light. Before Fresnel, it was thought that polarization could vary in direction, and in degree (e.g., due to variation in the angle of reflection off a transparent body), and that it could be a function of color (chromatic polarization), but not that it could vary in kind. Hence it was thought that the degree of polarization was the degree to which the light could be suppressed by an analyzer with the appropriate orientation. Light that had been converted from linear to elliptical or circular polarization (e.g., by passage through a crystal lamina, or by total internal reflection) was described as partly or fully "depolarized" because of its behavior in an analyzer. After Fresnel, the defining feature of polarized light was that the perpendicular components of vibration had a fixed ratio of amplitudes and a fixed difference in phase. By that definition, elliptically or circularly polarized light is fully polarized although it cannot be fully suppressed by an analyzer alone. The conceptual gap between the wave theory and selectionism had widened again. Total internal reflection (1817–23) By 1817 it had been discovered by Brewster, but not adequately reported, that plane-polarized light was partly depolarized by total internal reflection if initially polarized at an acute angle to the plane of incidence. Fresnel rediscovered this effect and investigated it by including total internal reflection in a chromatic-polarization experiment. With the aid of his first theory of chromatic polarization, he found that the apparently depolarized light was a mixture of components polarized parallel and perpendicular to the plane of incidence, and that the total reflection introduced a phase difference between them. Choosing an appropriate angle of incidence (not yet exactly specified) gave a phase difference of 1/8 of a cycle (45°). Two such reflections from the "parallel faces" of "two coupled prisms" gave a phase difference of 1/4 of a cycle (90°). These findings were contained in a memoir submitted to the Académie on 10 November 1817 and read a fortnight later. An undated marginal note indicates that the two coupled prisms were later replaced by a single "parallelepiped in glass"—now known as a Fresnel rhomb. This was the memoir whose "supplement", dated January 1818, contained the method of superposing sinusoidal functions and the restatement of Malus's law in terms of amplitudes. In the same supplement, Fresnel reported his discovery that optical rotation could be emulated by passing the polarized light through a Fresnel rhomb (still in the form of "coupled prisms"), followed by an ordinary birefringent lamina sliced parallel to its axis, with the axis at 45° to the plane of reflection of the Fresnel rhomb, followed by a second Fresnel rhomb at 90° to the first. In a further memoir read on 30 March, Fresnel reported that if polarized light was fully "depolarized" by a Fresnel rhomb – now described as a parallelepiped – its properties were not further modified by a subsequent passage through an optically rotating medium or device. The connection between optical rotation and birefringence was further explained in 1822, in the memoir on elliptical and circular polarization. This was followed by the memoir on reflection, read in January 1823, in which Fresnel quantified the phase shifts in total internal reflection, and thence calculated the precise angle at which a Fresnel rhomb should be cut in order to convert linear polarization to circular polarization. For a refractive index of 1.51, there were two solutions: about 48.6° and 54.6°. Double refraction Background: Uniaxial and biaxial crystals; Biot's laws When light passes through a slice of calcite cut perpendicular to its optic axis, the difference between the propagation times of the ordinary and extraordinary waves has a second-order dependence on the angle of incidence. If the slice is observed in a highly convergent cone of light, that dependence becomes significant, so that a chromatic-polarization experiment will show a pattern of concentric rings. But most minerals, when observed in this manner, show a more complicated pattern of rings involving two foci and a lemniscate curve, as if they had two optic axes. The two classes of minerals naturally become known as uniaxal and biaxal—or, in later literature, uniaxial and biaxial. In 1813, Brewster observed the simple concentric pattern in "beryl, emerald, ruby &c." The same pattern was later observed in calcite by Wollaston, Biot, and Seebeck.  Biot, assuming that the concentric pattern was the general case, tried to calculate the colors with his theory of chromatic polarization, and succeeded better for some minerals than for others. In 1818, Brewster belatedly explained why: seven of the twelve minerals employed by Biot had the lemniscate pattern, which Brewster had observed as early as 1812; and the minerals with the more complicated rings also had a more complicated law of refraction. In a uniform crystal, according to Huygens's theory, the secondary wavefront that expands from the origin in unit time is the ray-velocity surface—that is, the surface whose "distance" from the origin in any direction is the ray velocity in that direction. In calcite, this surface is two-sheeted, consisting of a sphere (for the ordinary wave) and an oblate spheroid (for the extraordinary wave) touching each other at opposite points of a common axis—touching at the north and south poles, if we may use a geographic analogy. But according to Malus's corpuscular theory of double refraction, the ray velocity was proportional to the reciprocal of that given by Huygens's theory, in which case the velocity law was of the form where and were the ordinary and extraordinary ray velocities according to the corpuscular theory, and was the angle between the ray and the optic axis. By Malus's definition, the plane of polarization of a ray was the plane of the ray and the optic axis if the ray was ordinary, or the perpendicular plane (containing the ray) if the ray was extraordinary. In Fresnel's model, the direction of vibration was normal to the plane of polarization. Hence, for the sphere (the ordinary wave), the vibration was along the lines of latitude (continuing the geographic analogy); and for the spheroid (the extraordinary wave), the vibration was along the lines of longitude. On 29 March 1819, Biot presented a memoir in which he proposed simple generalizations of Malus's rules for a crystal with two axes, and reported that both generalizations seemed to be confirmed by experiment. For the velocity law, the squared sine was replaced by the product of the sines of the angles from the ray to the two axes (Biot's sine law). And for the polarization of the ordinary ray, the plane of the ray and the axis was replaced by the plane bisecting the dihedral angle between the two planes each of which contained the ray and one axis (Biot's dihedral law). Biot's laws meant that a biaxial crystal with axes at a small angle, cleaved in the plane of those axes, behaved nearly like a uniaxial crystal at near-normal incidence; this was fortunate because gypsum, which had been used in chromatic-polarization experiments, is biaxial. First memoir and supplements (1821–22) Until Fresnel turned his attention to biaxial birefringence, it was assumed that one of the two refractions was ordinary, even in biaxial crystals. But, in a memoir submitted on 19 November 1821, Fresnel reported two experiments on topaz showing that neither refraction was ordinary in the sense of satisfying Snell's law; that is, neither ray was the product of spherical secondary waves. The same memoir contained Fresnel's first attempt at the biaxial velocity law. For calcite, if we interchange the equatorial and polar radii of Huygens's oblate spheroid while preserving the polar direction, we obtain a prolate spheroid touching the sphere at the equator. A plane through the center/origin cuts this prolate spheroid in an ellipse whose major and minor semi-axes give the magnitudes of the extraordinary and ordinary ray velocities in the direction normal to the plane, and (said Fresnel) the directions of their respective vibrations. The direction of the optic axis is the normal to the plane for which the ellipse of intersection reduces to a circle. So, for the biaxial case, Fresnel simply replaced the prolate spheroid with a triaxial ellipsoid, which was to be sectioned by a plane in the same way. In general there would be two planes passing through the center of the ellipsoid and cutting it in a circle, and the normals to these planes would give two optic axes. From the geometry, Fresnel deduced Biot's sine law (with the ray velocities replaced by their reciprocals). The ellipsoid indeed gave the correct ray velocities (although the initial experimental verification was only approximate). But it did not give the correct directions of vibration, for the biaxial case or even for the uniaxial case, because the vibrations in Fresnel's model were tangential to the wavefront—which, for an extraordinary ray, is not generally normal to the ray. This error (which is small if, as in most cases, the birefringence is weak) was corrected in an "extract" that Fresnel read to the Académie a week later, on 26 November. Starting with Huygens's spheroid, Fresnel obtained a 4th-degree surface which, when sectioned by a plane as above, would yield the wave-normal velocities for a wavefront in that plane, together with their vibration directions. For the biaxial case, he generalized the equation to obtain a surface with three unequal principal dimensions; this he subsequently called the "surface of elasticity". But he retained the earlier ellipsoid as an approximation, from which he deduced Biot's dihedral law. Fresnel's initial derivation of the surface of elasticity had been purely geometric, and not deductively rigorous. His first attempt at a mechanical derivation, contained in a "supplement" dated 13 January 1822, assumed that (i) there were three mutually perpendicular directions in which a displacement produced a reaction in the same direction, (ii) the reaction was otherwise a linear function of the displacement, and (iii) the radius of the surface in any direction was the square root of the component, in that direction, of the reaction to a unit displacement in that direction. The last assumption recognized the requirement that if a wave was to maintain a fixed direction of propagation and a fixed direction of vibration, the reaction must not be outside the plane of those two directions. In the same supplement, Fresnel considered how he might find, for the biaxial case, the secondary wavefront that expands from the origin in unit time—that is, the surface that reduces to Huygens's sphere and spheroid in the uniaxial case. He noted that this "wave surface" (surface de l'onde) is tangential to all possible plane wavefronts that could have crossed the origin one unit of time ago, and he listed the mathematical conditions that it must satisfy. But he doubted the feasibility of deriving the surface from those conditions. In a "second supplement", Fresnel eventually exploited two related facts: (i) the "wave surface" was also the ray-velocity surface, which could be obtained by sectioning the ellipsoid that he had initially mistaken for the surface of elasticity, and (ii) the "wave surface" intersected each plane of symmetry of the ellipsoid in two curves: a circle and an ellipse. Thus he found that the "wave surface" is described by the 4th-degree equation where and are the propagation speeds in directions normal to the coordinate axes for vibrations along the axes (the ray and wave-normal speeds being the same in those special cases). Later commentators put the equation in the more compact and memorable form Earlier in the "second supplement", Fresnel modeled the medium as an array of point-masses and found that the force-displacement relation was described by a symmetric matrix, confirming the existence of three mutually perpendicular axes on which the displacement produced a parallel force. Later in the document, he noted that in a biaxial crystal, unlike a uniaxial crystal, the directions in which there is only one wave-normal velocity are not the same as those in which there is only one ray velocity. Nowadays we refer to the former directions as the optic axes or binormal axes, and the latter as the ray axes or biradial axes . Fresnel's "second supplement" was signed on 31 March 1822 and submitted the next day – less than a year after the publication of his pure-transverse-wave hypothesis, and just less than a year after the demonstration of his prototype eight-panel lighthouse lens . Second memoir (1822–26) Having presented the pieces of his theory in roughly the order of discovery, Fresnel needed to rearrange the material so as to emphasize the mechanical foundations; and he still needed a rigorous treatment of Biot's dihedral law. He attended to these matters in his "second memoir" on double refraction, published in the Recueils of the Académie des Sciences for 1824; this was not actually printed until late 1827, a few months after his death. In this work, having established the three perpendicular axes on which a displacement produces a parallel reaction, and thence constructed the surface of elasticity, he showed that Biot's dihedral law is exact provided that the binormals are taken as the optic axes, and the wave-normal direction as the direction of propagation. As early as 1822, Fresnel discussed his perpendicular axes with Cauchy. Acknowledging Fresnel's influence, Cauchy went on to develop the first rigorous theory of elasticity of non-isotropic solids (1827), hence the first rigorous theory of transverse waves therein (1830) — which he promptly tried to apply to optics. The ensuing difficulties drove a long competitive effort to find an accurate mechanical model of the aether. Fresnel's own model was not dynamically rigorous; for example, it deduced the reaction to a shear strain by considering the displacement of one particle while all others were fixed, and it assumed that the stiffness determined the wave velocity as in a stretched string, whatever the direction of the wave-normal. But it was enough to enable the wave theory to do what selectionist theory could not: generate testable formulae covering a comprehensive range of optical phenomena, from mechanical assumptions. Photoelasticity, multiple-prism experiments (1822) In 1815, Brewster reported that colors appear when a slice of isotropic material, placed between crossed polarizers, is mechanically stressed. Brewster himself immediately and correctly attributed this phenomenon to stress-induced birefringence — now known as photoelasticity. In a memoir read in September 1822, Fresnel announced that he had verified Brewster's diagnosis more directly, by compressing a combination of glass prisms so severely that one could actually see a double image through it. In his experiment, Fresnel lined up seven 45°-90°-45° prisms, short side to short side, with their 90° angles pointing in alternating directions. Two half-prisms were added at the ends to make the whole assembly rectangular. The prisms were separated by thin films of turpentine (térébenthine) to suppress internal reflections, allowing a clear line of sight along the row. When the four prisms with similar orientations were compressed in a vise across the line of sight, an object viewed through the assembly produced two images with perpendicular polarizations, with an apparent spacing of 1.5mm at one metre. At the end of that memoir, Fresnel predicted that if the compressed prisms were replaced by (unstressed) monocrystalline quartz prisms with matching directions of optical rotation, and with their optic axes aligned along the row, an object seen by looking along the common optic axis would give two images, which would seem unpolarized when viewed through an analyzer but, when viewed through a Fresnel rhomb, would be polarized at ±45° to the plane of reflection of the rhomb (indicating that they were initially circularly polarized in opposite directions). This would show directly that optical rotation is a form of birefringence. In the memoir of December 1822, in which he introduced the term circular polarization, he reported that he had confirmed this prediction using only one 14°-152°-14° prism and two glass half-prisms. But he obtained a wider separation of the images by replacing the glass half-prism with quartz half-prisms whose rotation was opposite to that of the 14°-152°-14° prism. He added in passing that one could further increase the separation by increasing the number of prisms. Reception For the supplement to Riffault's translation of Thomson's System of Chemistry, Fresnel was chosen to contribute the article on light. The resulting 137-page essay, titled De la Lumière (On Light), was apparently finished in June 1821 and published by February 1822. With sections covering the nature of light, diffraction, thin-film interference, reflection and refraction, double refraction and polarization, chromatic polarization, and modification of polarization by reflection, it made a comprehensive case for the wave theory to a readership that was not restricted to physicists. To examine Fresnel's first memoir and supplements on double refraction, the Académie des Sciences appointed Ampère, Arago, Fourier, and Poisson. Their report, of which Arago was clearly the main author, was delivered at the meeting of 19 August 1822. Then, in the words of Émile Verdet, as translated by Ivor Grattan-Guinness: Whether Laplace was announcing his conversion to the wave theory – at the age of 73 – is uncertain. Grattan-Guinness entertained the idea. Buchwald, noting that Arago failed to explain that the "ellipsoid of elasticity" did not give the correct planes of polarization, suggests that Laplace may have merely regarded Fresnel's theory as a successful generalization of Malus's ray-velocity law, embracing Biot's laws. In the following year, Poisson, who did not sign Arago's report, disputed the possibility of transverse waves in the aether. Starting from assumed equations of motion of a fluid medium, he noted that they did not give the correct results for partial reflection and double refraction – as if that were Fresnel's problem rather than his own – and that the predicted waves, even if they were initially transverse, became more longitudinal as they propagated. In reply Fresnel noted, inter alia, that the equations in which Poisson put so much faith did not even predict viscosity. The implication was clear: given that the behavior of light had not been satisfactorily explained except by transverse waves, it was not the responsibility of the wave-theorists to abandon transverse waves in deference to pre-conceived notions about the aether; rather, it was the responsibility of the aether modelers to produce a model that accommodated transverse waves. According to Robert H. Silliman, Poisson eventually accepted the wave theory shortly before his death in 1840. Among the French, Poisson's reluctance was an exception. According to Eugene Frankel, "in Paris no debate on the issue seems to have taken place after 1825. Indeed, almost the entire generation of physicists and mathematicians who came to maturity in the 1820s – Pouillet, Savart, Lamé, Navier, Liouville, Cauchy – seem to have adopted the theory immediately." Fresnel's other prominent French opponent, Biot, appeared to take a neutral position in 1830, and eventually accepted the wave theory – possibly by 1846 and certainly by 1858. In 1826, the British astronomer John Herschel, who was working on a book-length article on light for the Encyclopædia Metropolitana, addressed three questions to Fresnel concerning double refraction, partial reflection, and their relation to polarization. The resulting article, titled simply "Light", was highly sympathetic to the wave theory, although not entirely free of selectionist language. It was circulating privately by 1828 and was published in 1830. Meanwhile, Young's translation of Fresnel's De la Lumière was published in installments from 1827 to 1829. George Biddell Airy, the former Lucasian Professor at Cambridge and future Astronomer Royal, unreservedly accepted the wave theory by 1831. In 1834, he famously calculated the diffraction pattern of a circular aperture from the wave theory, thereby explaining the limited angular resolution of a perfect telescope . By the end of the 1830s, the only prominent British physicist who held out against the wave theory was Brewster, whose objections included the difficulty of explaining photochemical effects and (in his opinion) dispersion. A German translation of De la Lumière was published in installments in 1825 and 1828. The wave theory was adopted by Fraunhofer in the early 1820s and by Franz Ernst Neumann in the 1830s, and then began to find favor in German textbooks. The economy of assumptions under the wave theory was emphasized by William Whewell in his History of the Inductive Sciences, first published in 1837. In the corpuscular system, "every new class of facts requires a new supposition," whereas in the wave system, a hypothesis devised in order to explain one phenomenon is then found to explain or predict others. In the corpuscular system there is "no unexpected success, no happy coincidence, no convergence of principles from remote quarters"; but in the wave system, "all tends to unity and simplicity." Hence, in 1850, when Foucault and Fizeau found by experiment that light travels more slowly in water than in air, in accordance with the wave explanation of refraction and contrary to the corpuscular explanation, the result came as no surprise. Lighthouses and the Fresnel lens Fresnel was not the first person to focus a lighthouse beam using a lens. That distinction apparently belongs to the London glass-cutter Thomas Rogers, whose first lenses, 53cm in diameter and 14cm thick at the center, were installed at the Old Lower Lighthouse at Portland Bill in 1789. Further samples were installed in about half a dozen other locations by 1804. But much of the light was wasted by absorption in the glass. Nor was Fresnel the first to suggest replacing a convex lens with a series of concentric annular prisms, to reduce weight and absorption. In 1748, Count Buffon proposed grinding such prisms as steps in a single piece of glass. In 1790, the Marquis de Condorcet suggested that it would be easier to make the annular sections separately and assemble them on a frame; but even that was impractical at the time. These designs were intended not for lighthouses, but for burning glasses. Brewster, however, proposed a system similar to Condorcet's in 1811, and by 1820 was advocating its use in British lighthouses. Meanwhile, on 21 June 1819, Fresnel was "temporarily" seconded by the Commission des Phares (Commission of Lighthouses) on the recommendation of Arago (a member of the Commission since 1813), to review possible improvements in lighthouse illumination. The commission had been established by Napoleon in 1811 and placed under the Corps des Ponts – Fresnel's employer. By the end of August 1819, unaware of the Buffon-Condorcet-Brewster proposal, Fresnel made his first presentation to the commission, recommending what he called lentilles à échelons (lenses by steps) to replace the reflectors then in use, which reflected only about half of the incident light. One of the assembled commissioners, Jacques Charles, recalled Buffon's suggestion, leaving Fresnel embarrassed for having again "broken through an open door". But, whereas Buffon's version was biconvex and in one piece, Fresnel's was plano-convex and made of multiple prisms for easier construction. With an official budget of 500 francs, Fresnel approached three manufacturers. The third, François Soleil, produced the prototype. Finished in March 1820, it had a square lens panel 55cm on a side, containing 97 polygonal (not annular) prisms – and so impressed the Commission that Fresnel was asked for a full eight-panel version. This model, completed a year later in spite of insufficient funding, had panels 76cm square. In a public spectacle on the evening of 13 April 1821, it was demonstrated by comparison with the most recent reflectors, which it suddenly rendered obsolete. Fresnel's next lens was a rotating apparatus with eight "bull's-eye" panels, made in annular arcs by Saint-Gobain, giving eight rotating beams – to be seen by mariners as a periodic flash. Above and behind each main panel was a smaller, sloping bull's-eye panel of trapezoidal outline with trapezoidal elements. This refracted the light to a sloping plane mirror, which then reflected it horizontally, 7 degrees ahead of the main beam, increasing the duration of the flash. Below the main panels were 128 small mirrors arranged in four rings, stacked like the slats of a louver or Venetian blind. Each ring, shaped as a frustum of a cone, reflected the light to the horizon, giving a fainter steady light between the flashes. The official test, conducted on the unfinished Arc de Triomphe on 20 August 1822, was witnessed by the commission – and by Louis and his entourage – from 32km away. The apparatus was stored at Bordeaux for the winter, and then reassembled at Cordouan Lighthouse under Fresnel's supervision. On 25 July 1823, the world's first lighthouse Fresnel lens was lit. Soon afterwards, Fresnel started coughing up blood. In May 1824, Fresnel was promoted to secretary of the Commission des Phares, becoming the first member of that body to draw a salary, albeit in the concurrent role of Engineer-in-Chief. He was also an examiner (not a teacher) at the École Polytechnique since 1821; but poor health, long hours during the examination season, and anxiety about judging others induced him to resign that post in late 1824, to save his energy for his lighthouse work. In the same year he designed the first fixed lens – for spreading light evenly around the horizon while minimizing waste above or below. Ideally the curved refracting surfaces would be segments of toroids about a common vertical axis, so that the dioptric panel would look like a cylindrical drum. If this was supplemented by reflecting (catoptric) rings above and below the refracting (dioptric) parts, the entire apparatus would look like a beehive. The second Fresnel lens to enter service was indeed a fixed lens, of third order, installed at Dunkirk by 1 February 1825. However, due to the difficulty of fabricating large toroidal prisms, this apparatus had a 16-sided polygonal plan. In 1825, Fresnel extended his fixed-lens design by adding a rotating array outside the fixed array. Each panel of the rotating array was to refract part of the fixed light from a horizontal fan into a narrow beam. Also in 1825, Fresnel unveiled the Carte des Phares (Lighthouse Map), calling for a system of 51 lighthouses plus smaller harbor lights, in a hierarchy of lens sizes (called orders, the first order being the largest), with different characteristics to facilitate recognition: a constant light (from a fixed lens), one flash per minute (from a rotating lens with eight panels), and two per minute (sixteen panels). In late 1825, to reduce the loss of light in the reflecting elements, Fresnel proposed to replace each mirror with a catadioptric prism, through which the light would travel by refraction through the first surface, then total internal reflection off the second surface, then refraction through the third surface. The result was the lighthouse lens as we now know it. In 1826 he assembled a small model for use on the Canal Saint-Martin, but he did not live to see a full-sized version. The first fixed lens with toroidal prisms was a first-order apparatus designed by the Scottish engineer Alan Stevenson under the guidance of Léonor Fresnel, and fabricated by Isaac Cookson & Co. from French glass; it entered service at the Isle of May in 1836. The first large catadioptric lenses were fixed third-order lenses made in 1842 for the lighthouses at Gravelines and Île Vierge. The first fully catadioptric first-order lens, installed at Ailly in 1852, gave eight rotating beams assisted by eight catadioptric panels at the top (to lengthen the flashes), plus a fixed light from below. The first fully catadioptric lens with purely revolving beams – also of first order – was installed at Saint-Clément-des-Baleines in 1854, and marked the completion of Augustin Fresnel's original Carte des Phares. Production of one-piece stepped dioptric lenses—roughly as envisaged by Buffon—became practical in 1852, when John L. Gilliland of the Brooklyn Flint-Glass Company patented a method of making such lenses from press-molded glass. By the 1950s, the substitution of plastic for glass made it economic to use fine-stepped Fresnel lenses as condensers in overhead projectors. Still finer steps can be found in low-cost plastic "sheet" magnifiers. Honors Fresnel was elected to the Société Philomathique de Paris in April 1819, and in 1822 became one of the editors of the Société's Bulletin des Sciences. As early as May 1817, at Arago's suggestion, Fresnel applied for membership of the Académie des Sciences, but received only one vote. The successful candidate on that occasion was Joseph Fourier. In November 1822, Fourier's elevation to Permanent Secretary of the Académie created a vacancy in the physics section, which was filled in February 1823 by Pierre Louis Dulong, with 36 votes to Fresnel's 20. But in May 1823, after another vacancy was left by the death of Jacques Charles, Fresnel's election was unanimous. In 1824, Fresnel was made a chevalier de la Légion d'honneur (Knight of the Legion of Honour). Meanwhile, in Britain, the wave theory was yet to take hold; Fresnel wrote to Thomas Young in November 1824, saying in part: But "the praise of English scholars" soon followed. On 9 June 1825, Fresnel was made a Foreign Member of the Royal Society of London. In 1827 he was awarded the society's Rumford Medal for the year 1824, "For his Development of the Undulatory Theory as applied to the Phenomena of Polarized Light, and for his various important discoveries in Physical Optics." A monument to Fresnel at his birthplace was dedicated on 14 September 1884 with a speech by , Permanent Secretary of the Académie des Sciences.  "" is among the 72 names embossed on the Eiffel Tower (on the south-east side, fourth from the left). In the 19th century, as every lighthouse in France acquired a Fresnel lens, every one acquired a bust of Fresnel, seemingly watching over the coastline that he had made safer. The lunar features Promontorium Fresnel and Rimae Fresnel were later named after him. Decline and death Fresnel's health, which had always been poor, deteriorated in the winter of 1822–1823, increasing the urgency of his original research, and (in part) preventing him from contributing an article on polarization and double refraction for the Encyclopædia Britannica. The memoirs on circular and elliptical polarization and optical rotation, and on the detailed derivation of the Fresnel equations and their application to total internal reflection, date from this period. In the spring he recovered enough, in his own view, to supervise the lens installation at Cordouan. Soon afterwards, it became clear that his condition was tuberculosis. In 1824, he was advised that if he wanted to live longer, he needed to scale back his activities. Perceiving his lighthouse work to be his most important duty, he resigned as an examiner at the École Polytechnique, and closed his scientific notebooks. His last note to the Académie, read on 13 June 1825, described the first radiometer and attributed the observed repulsive force to a temperature difference. Although his fundamental research ceased, his advocacy did not; as late as August or September 1826, he found the time to answer Herschel's queries on the wave theory. It was Herschel who recommended Fresnel for the Royal Society's Rumford Medal. Fresnel's cough worsened in the winter of 1826–1827, leaving him too ill to return to Mathieu in the spring. The Académie meeting of 30 April 1827 was the last that he attended. In early June he was carried to Ville-d'Avray, 12km west of Paris. There his mother joined him. On 6 July, Arago arrived to deliver the Rumford Medal. Sensing Arago's distress, Fresnel whispered that "the most beautiful crown means little, when it is laid on the grave of a friend." Fresnel did not have the strength to reply to the Royal Society. He died eight days later, on Bastille Day. He is buried at Père Lachaise Cemetery, Paris. The inscription on his headstone is partly eroded away; the legible part says, when translated, "To the memory of Augustin Jean Fresnel, member of the Institute of France". Posthumous publications Fresnel's "second memoir" on double refraction was not printed until late 1827, a few months after his death. Until then, the best published source on his work on double refraction was an extract of that memoir, printed in 1822. His final treatment of partial reflection and total internal reflection, read to the Académie in January 1823, was thought to be lost until it was rediscovered among the papers of the deceased Joseph Fourier (1768–1830), and was printed in 1831. Until then, it was known chiefly through an extract printed in 1823 and 1825. The memoir introducing the parallelepiped form of the Fresnel rhomb, read in March 1818, was mislaid until 1846, and then attracted such interest that it was soon republished in English. Most of Fresnel's writings on polarized light before 1821 – including his first theory of chromatic polarization (submitted 7 October 1816) and the crucial "supplement" of January 1818 — were not published in full until his Oeuvres complètes ("complete works") began to appear in 1866. The "supplement" of July 1816, proposing the "efficacious ray" and reporting the famous double-mirror experiment, met the same fate, as did the "first memoir" on double refraction. Publication of Fresnel's collected works was itself delayed by the deaths of successive editors. The task was initially entrusted to Félix Savary, who died in 1841. It was restarted twenty years later by the Ministry of Public Instruction. Of the three editors eventually named in the Oeuvres, Sénarmont died in 1862, Verdet in 1866, and Léonor Fresnel in 1869, by which time only two of the three volumes had appeared. At the beginning of vol. 3 (1870), the completion of the project is described in a long footnote by "J. Lissajous." Not included in the Oeuvres are two short notes by Fresnel on magnetism, which were discovered among Ampère's manuscripts. In response to Ørsted's discovery of electromagnetism in 1820, Ampère initially supposed that the field of a permanent magnet was due to a macroscopic circulating current. Fresnel suggested instead that there was a microscopic current circulating around each particle of the magnet. In his first note, he argued that microscopic currents, unlike macroscopic currents, would explain why a hollow cylindrical magnet does not lose its magnetism when cut longitudinally. In his second note, dated 5 July 1821, he further argued that a macroscopic current had the counterfactual implication that a permanent magnet should be hot, whereas microscopic currents circulating around the molecules might avoid the heating mechanism. He was not to know that the fundamental units of permanent magnetism are even smaller than molecules . The two notes, together with Ampère's acknowledgment, were eventually published in 1885. Lost works Fresnel's essay Rêveries of 1814 has not survived. While its content would have been interesting to historians, its quality may perhaps be gauged from the fact that Fresnel himself never referred to it in his maturity. More disturbing is the fate of the late article "Sur les Différents Systèmes relatifs à la Théorie de la Lumière" ("On the Different Systems relating to the Theory of Light"), which Fresnel wrote for the newly launched English journal European Review. This work seems to have been similar in scope to the essay De la Lumière of 1821/22, except that Fresnel's views on double refraction, circular and elliptical polarization, optical rotation, and total internal reflection had developed since then. The manuscript was received by the publisher's agent in Paris in early September 1824, and promptly forwarded to London. But the journal failed before Fresnel's contribution could be published. Fresnel tried unsuccessfully to recover the manuscript. The editors of his collected works were also unable to find it, and admitted that it was probably lost. Unfinished business Aether drag and aether density In 1810, Arago found experimentally that the degree of refraction of starlight does not depend on the direction of the earth's motion relative to the line of sight. In 1818, Fresnel showed that this result could be explained by the wave theory, on the hypothesis that if an object with refractive index moved at velocity relative to the external aether (taken as stationary), then the velocity of light inside the object gained the additional component . He supported that hypothesis by supposing that if the density of the external aether was taken as unity, the density of the internal aether was , of which the excess, namely , was dragged along at velocity , whence the average velocity of the internal aether was . The factor in parentheses, which Fresnel originally expressed in terms of wavelengths, became known as the Fresnel drag coefficient. In his analysis of double refraction, Fresnel supposed that the different refractive indices in different directions within the same medium were due to a directional variation in elasticity, not density (because the concept of mass per unit volume is not directional). But in his treatment of partial reflection, he supposed that the different refractive indices of different media were due to different aether densities, not different elasticities. The latter decision, although puzzling in the context of double refraction, was consistent with the earlier treatment of aether drag. In 1846, George Gabriel Stokes pointed out that there was no need to divide the aether inside a moving object into two portions; all of it could be considered as moving at a common velocity. Then, if the aether was conserved while its density changed in proportion to , the resulting velocity of the aether inside the object was equal to Fresnel's additional velocity component. Dispersion The analogy between light waves and transverse waves in elastic solids does not predict dispersion — that is, the frequency-dependence of the speed of propagation, which enables prisms to produce spectra and causes lenses to suffer from chromatic aberration. Fresnel, in De la Lumière and in the second supplement to his first memoir on double refraction, suggested that dispersion could be accounted for if the particles of the medium exerted forces on each other over distances that were significant fractions of a wavelength. Later, more than once, Fresnel referred to the demonstration of this result as being contained in a note appended to his "second memoir" on double refraction. But no such note appeared in print, and the relevant manuscripts found after his death showed only that, around 1824, he was comparing refractive indices (measured by Fraunhofer) with a theoretical formula, the meaning of which was not fully explained. In the 1830s, Fresnel's suggestion was taken up by Cauchy, Powell, and Kelland, and it was indeed found to be tolerably consistent with the variation of refractive indices with wavelength over the visible spectrum, for a variety of transparent media . These investigations were enough to show that the wave theory was at least compatible with dispersion. However, if the model of dispersion was to be accurate over a wider range of frequencies, it needed to be modified so as to take account of resonances within the medium . Conical refraction The analytical complexity of Fresnel's derivation of the ray-velocity surface was an implicit challenge to find a shorter path to the result. This was answered by MacCullagh in 1830, and by William Rowan Hamilton in 1832. Hamilton went further, establishing two properties of the surface that Fresnel, in the short time given to him, had overlooked: (i) at each of the four points where the inner and outer sheets of the surface make contact, the surface has a tangent cone (tangential to both sheets), hence a cone of normals, indicating that a cone of wave-normal directions corresponds to a single ray-velocity vector; and (ii) around each of these points, the outer sheet has a circle of contact with a tangent plane, indicating that a cone of ray directions corresponds to a single wave-normal velocity vector. As Hamilton noted, these properties respectively imply that (i) a narrow beam propagating inside the crystal in the direction of the single ray velocity will, on exiting the crystal through a flat surface, break into a hollow cone (external conical refraction), and (ii) a narrow beam striking a flat surface of the crystal in the appropriate direction (corresponding to that of the single internal wave-normal velocity) will, on entering the crystal, break into a hollow cone (internal conical refraction). Thus a new pair of phenomena, qualitatively different from anything previously observed or suspected, had been predicted by mathematics as consequences of Fresnel's theory. The prompt experimental confirmation of those predictions by Humphrey Lloyd brought Hamilton a prize that had never come to Fresnel: immediate fame. Legacy Within a century of Fresnel's initial stepped-lens proposal, more than 10,000 lights with Fresnel lenses were protecting lives and property around the world. Concerning the other benefits, the science historian Theresa H. Levitt has remarked: In the history of physical optics, Fresnel's successful revival of the wave theory nominates him as the pivotal figure between Newton, who held that light consisted of corpuscles, and James Clerk Maxwell, who established that light waves are electromagnetic. Whereas Albert Einstein described Maxwell's work as "the most profound and the most fruitful that physics has experienced since the time of Newton," commentators of the era between Fresnel and Maxwell made similarly strong statements about Fresnel: MacCullagh, as early as 1830, wrote that Fresnel's mechanical theory of double refraction "would do honour to the sagacity of Newton". Lloyd, in his Report on the progress and present state of physical optics (1834) for the British Association for the Advancement of Science, surveyed previous knowledge of double refraction and declared:The theory of Fresnel to which I now proceed,— and which not only embraces all the known phenomena, but has even outstripped observation, and predicted consequences which were afterwards fully verified,— will, I am persuaded, be regarded as the finest generalization in physical science which has been made since the discovery of universal gravitation.In 1841, Lloyd published his Lectures on the Wave-theory of Light, in which he described Fresnel's transverse-wave theory as "the noblest fabric which has ever adorned the domain of physical science, Newton's system of the universe alone excepted." William Whewell, in all three editions of his History of the Inductive Sciences (1837, 1847, and 1857), at the end of Book , compared the histories of physical astronomy and physical optics and concluded:It would, perhaps, be too fanciful to attempt to establish a parallelism between the prominent persons who figure in these two histories. If we were to do this, we must consider Huyghens and Hooke as standing in the place of Copernicus, since, like him, they announced the true theory, but left it to a future age to give it development and mechanical confirmation; Malus and Brewster, grouping them together, correspond to Tycho Brahe and Kepler, laborious in accumulating observations, inventive and happy in discovering laws of phenomena; and Young and Fresnel combined, make up the Newton of optical science. What Whewell called the "true theory" has since undergone two major revisions. The first, by Maxwell, specified the physical fields whose variations constitute the waves of light. Without the benefit of this knowledge, Fresnel managed to construct the world's first coherent theory of light, showing in retrospect that his methods are applicable to multiple types of waves. The second revision, initiated by Einstein's explanation of the photoelectric effect, supposed that the energy of light waves was divided into quanta, which were eventually identified with particles called photons. But photons did not exactly correspond to Newton's corpuscles; for example, Newton's explanation of ordinary refraction required the corpuscles to travel faster in media of higher refractive index, which photons do not. Neither did photons displace waves; rather, they led to the paradox of wave–particle duality. Moreover, the phenomena studied by Fresnel, which included nearly all the optical phenomena known at his time, are still most easily explained in terms of the wave nature of light. So it was that, as late as 1927, the astronomer Eugène Michel Antoniadi declared Fresnel to be "the dominant figure in optics." See also Explanatory notes References Citations Bibliography D.F.J. Arago (tr. B. Powell), 1857, "Fresnel" (elegy read at the Public Meeting of the Academy of Sciences, 26 July 1830), in D.F.J. Arago (tr.  W.H. Smyth, B. Powell, and R. Grant), Biographies of Distinguished Scientific Men (single-volume edition), London: Longman, Brown, Green, Longmans, & Roberts, 1857, pp. 399–471. (On the translator's identity, see pp. 425n,452n.)  Erratum: In the translator's note on p. 413, a plane tangent to the outer sphere at point t should intersect the refractive surface (assumed flat); then, through that intersection, tangent planes should be drawn to the inner sphere and spheroid (cf. Mach, 1926, p.263). D.F.J. Arago and A. Fresnel, 1819, "Mémoire sur l'action que les rayons de lumière polarisée exercent les uns sur les autres", Annales de Chimie et de Physique, Ser.2, vol. 10, pp. 288–305, March 1819; reprinted in Fresnel, 1866–70, vol. 1, pp. 509–22; translated as "On the action of rays of polarized light upon each other", in Crew, 1900, pp. 145–55. G.-A. Boutry, 1948, "Augustin Fresnel: His time, life and work, 1788–1827", Science Progress, vol. 36, no. 144 (October 1948), pp. 587–604; jstor.org/stable/43413515. J.Z. Buchwald, 1989, The Rise of the Wave Theory of Light: Optical Theory and Experiment in the Early Nineteenth Century, University of Chicago Press, . J.Z. Buchwald, 2013, "Optics in the Nineteenth Century", in J.Z. Buchwald and R. Fox (eds.), The Oxford Handbook of the History of Physics, Oxford, , pp. 445–72. H. Crew (ed.), 1900, The Wave Theory of Light: Memoirs by Huygens, Young and Fresnel, American Book Company. O. Darrigol, 2012, A History of Optics: From Greek Antiquity to the Nineteenth Century, Oxford, . J. Elton, 2009, "A Light to Lighten our Darkness: Lighthouse Optics and the Later Development of Fresnel's Revolutionary Refracting Lens 1780–1900", International Journal for the History of Engineering & Technology, vol. 79, no. 2 (July 2009), pp. 183–244; . E. Frankel, 1974, "The search for a corpuscular theory of double refraction: Malus, Laplace and the competition of 1808", Centaurus, vol. 18, no. 3 (September 1974), pp. 223–245. E. Frankel, 1976, "Corpuscular optics and the wave theory of light: The science and politics of a revolution in physics", Social Studies of Science, vol. 6, no. 2 (May 1976), pp. 141–84; jstor.org/stable/284930. A. Fresnel, 1815a, Letter to Jean François "Léonor" Mérimée, 10 February 1815 (Smithsonian Dibner Library, MSS 546A), printed in G. Magalhães, "Remarks on a new autograph letter from Augustin Fresnel: Light aberration and wave theory", Science in Context, vol. 19, no.2 (June 2006), pp. 295–307, , at p.306 (original French) and p.307 (English translation). A. Fresnel, 1816, "Mémoire sur la diffraction de la lumière" ("Memoir on the diffraction of light"), Annales de Chimie et de Physique, Ser.2, vol. 1, pp. 239–81 (March 1816); reprinted as "Deuxième Mémoire…" ("Second Memoir…") in Fresnel, 1866–70, vol. 1, pp. 89–122.  Not to be confused with the later "prize memoir" (Fresnel, 1818b). A. Fresnel, 1818a, "Mémoire sur les couleurs développées dans les fluides homogènes par la lumière polarisée", read 30 March 1818 (according to Kipnis, 1991, p. 217), published 1846; reprinted in Fresnel, 1866–70, vol. 1, pp. 655–83; translated by E. Ronalds & H. Lloyd as "Memoir upon the colours produced in homogeneous fluids by polarized light", in Taylor, 1852, pp. 44–65. (Cited page numbers refer to the translation.) A. Fresnel, 1818b, "Mémoire sur la diffraction de la lumière" ("Memoir on the diffraction of light"), deposited 29 July 1818, "crowned" 15 March 1819, published (with appended notes) in Mémoires de l'Académie Royale des Sciences de l'Institut de France, vol.  (for 1821 & 1822, printed 1826), pp. 339–475; reprinted (with notes) in Fresnel, 1866–70, vol. 1, pp. 247–383; partly translated as "Fresnel's prize memoir on the diffraction of light", in Crew, 1900, pp. 81–144.  Not to be confused with the earlier memoir with the same French title (Fresnel, 1816). A. Fresnel, 1818c, "Lettre de M. Fresnel à M. Arago sur l'influence du mouvement terrestre dans quelques phénomènes d'optique", Annales de Chimie et de Physique, Ser.2, vol. 9, pp. 57–66 & plate after p.111 (Sep. 1818), & p.286–7 (Nov. 1818); reprinted in Fresnel, 1866–70, vol. 2, pp. 627–36; translated as "Letter from Augustin Fresnel to François Arago, on the influence of the movement of the earth on some phenomena of optics" in K.F. Schaffner, Nineteenth-Century Aether Theories, Pergamon, 1972 (), pp. 125–35; also translated (with several errors) by R.R. Traill as "Letter from Augustin Fresnel to François Arago concerning the influence of terrestrial movement on several optical phenomena", General Science Journal, 23 January 2006 (PDF, 8pp.). A. Fresnel, 1821a, "Note sur le calcul des teintes que la polarisation développe dans les lames cristallisées" et seq., Annales de Chimie et de Physique, Ser.2, vol. 17, pp. 102–11 (May 1821), 167–96 (June 1821), 312–15 ("Postscript", July 1821); reprinted (with added section nos.) in Fresnel, 1866–70, vol. 1, pp. 609–48; translated as "On the calculation of the tints that polarization develops in crystalline plates, & postscript", / , 2021. A. Fresnel, 1821b, "Note sur les remarques de M. Biot...", Annales de Chimie et de Physique, Ser.2, vol. 17, pp. 393–403 (August 1821); reprinted (with added section nos.) in Fresnel, 1866–70, vol. 1, pp. 601–608; translated as "Note on the remarks of Mr. Biot relating to colors of thin plates", / , 2021. A. Fresnel, 1821c, Letter to D.F.J.Arago, 21 September 1821, in Fresnel, 1866–70, vol. 2, pp. 257–9; translated as "Letter to Arago on biaxial birefringence", Wikisource, April 2021. A. Fresnel, 1822a, De la Lumière (On Light), in J. Riffault (ed.), Supplément à la traduction française de la cinquième édition du "Système de Chimie" par Th.Thomson, Paris: Chez Méquignon-Marvis, 1822, pp. 1–137,535–9; reprinted in Fresnel, 1866–70, vol. 2, pp. 3–146; translated by T. Young as "Elementary view of the undulatory theory of light", Quarterly Journal of Science, Literature, and Art, vol. 22 (Jan.–Jun.1827), pp. 127–41, 441–54; vol. 23 (Jul.–Dec.1827), pp. 113–35, 431–48; vol. 24 (Jan.–Jun.1828), pp. 198–215; vol. 25 (Jul.–Dec.1828), pp. 168–91, 389–407; vol. 26 (Jan.–Jun.1829), pp. 159–65. A. Fresnel, 1822b, "Mémoire sur un nouveau système d'éclairage des phares", read 29 July 1822; reprinted in Fresnel, 1866–70, vol. 3, pp. 97–126; translated by T. Tag as "Memoir upon a new system of lighthouse illumination", U.S. Lighthouse Society, accessed 26 August 2017; archived 19 August 2016. (Cited page numbers refer to the translation.) A. Fresnel, 1827, "Mémoire sur la double réfraction", Mémoires de l'Académie Royale des Sciences de l'Institut de France, vol.  (for 1824, printed 1827), pp. 45–176; reprinted as "Second mémoire…" in Fresnel, 1866–70, vol. 2, pp. 479–596; translated by A.W. Hobson as "Memoir on double refraction", in Taylor, 1852, pp. 238–333. (Cited page numbers refer to the translation. For notable errata in the original edition, and consequently in the translation, see Fresnel, 1866–70, vol. 2, p. 596n.) A. Fresnel (ed. H. de Sénarmont, E. Verdet, and L. Fresnel), 1866–70, Oeuvres complètes d'Augustin Fresnel (3 volumes), Paris: Imprimerie Impériale; vol. 1 (1866), vol. 2 (1868), vol. 3 (1870). I. Grattan-Guinness, 1990, Convolutions in French Mathematics, 1800–1840, Basel: Birkhäuser, vol. 2, , chapter 13 (pp. 852–915, "The entry of Fresnel: Physical optics, 1815–1824") and chapter 15 (pp. 968–1045, "The entry of Navier and the triumph of Cauchy: Elasticity theory, 1819–1830"). C. Huygens, 1690, Traité de la Lumière (Leiden: Van der Aa), translated by S.P. Thompson as Treatise on Light, University of Chicago Press, 1912; Project Gutenberg, 2005. (Cited page numbers match the 1912 edition and the Gutenberg HTML edition.) F.A. Jenkins and H.E. White, 1976, Fundamentals of Optics, 4th Ed., New York: McGraw-Hill, . N. Kipnis, 1991, History of the Principle of Interference of Light, Basel: Birkhäuser, , chapters . K.A. Kneller (tr. T.M. Kettle), 1911, Christianity and the Leaders of Modern Science: A contribution to the history of culture in the nineteenth century, Freiburg im Breisgau: B. Herder, pp. 146–9. T.H. Levitt, 2009, The Shadow of Enlightenment: Optical and Political Transparency in France, 1789–1848, Oxford, . T.H. Levitt, 2013, A Short Bright Flash: Augustin Fresnel and the Birth of the Modern Lighthouse, New York: W.W. Norton, . H. Lloyd, 1834, "Report on the progress and present state of physical optics", Report of the Fourth Meeting of the British Association for the Advancement of Science (held at Edinburgh in 1834), London: J. Murray, 1835, pp. 295–413. E. Mach (tr. J.S. Anderson & A.F.A. Young), The Principles of Physical Optics: An Historical and Philosophical Treatment, London: Methuen & Co., 1926. I. Newton, 1730, Opticks: or, a Treatise of the Reflections, Refractions, Inflections, and Colours of Light, 4th Ed. (London: William Innys, 1730; Project Gutenberg, 2010); republished with Foreword by A. Einstein and Introduction by E.T. Whittaker (London: George Bell & Sons, 1931); reprinted with additional Preface by I.B. Cohen and Analytical Table of Contents by D.H.D. Roller,  Mineola, NY: Dover, 1952, 1979 (with revised preface), 2012. (Cited page numbers match the Gutenberg HTML edition and the Dover editions.) R.H. Silliman, 1967, Augustin Fresnel (1788–1827) and the Establishment of the Wave Theory of Light (PhD dissertation, ), Princeton University, submitted 1967, accepted 1968; available from ProQuest (missing the first page of the preface). R.H. Silliman, 2008, "Fresnel, Augustin Jean", Complete Dictionary of Scientific Biography, Detroit: Charles Scribner's Sons, vol. 5, pp. 165–71. (The version at encyclopedia.com lacks the diagram and equations.) R. Taylor (ed.), 1852, Scientific Memoirs, selected from the Transactions of Foreign Academies of Science and Learned Societies, and from Foreign Journals (in English), vol. , London: Taylor & Francis. W. Whewell, 1857, History of the Inductive Sciences: From the Earliest to the Present Time, 3rd Ed., London: J.W. Parker & Son, vol. 2, book , chapters . E. T. Whittaker, 1910, A History of the Theories of Aether and Electricity: From the age of Descartes to the close of the nineteenth century, London: Longmans, Green, & Co., chapters . J. Worrall, 1989, "Fresnel, Poisson and the white spot: The role of successful predictions in the acceptance of scientific theories", in D. Gooding, T. Pinch, and S. Schaffer (eds.), The Uses of Experiment: Studies in the Natural Sciences, Cambridge University Press, , pp. 135–57. T. Young, 1807, A Course of Lectures on Natural Philosophy and the Mechanical Arts (2 volumes), London: J.Johnson; vol. 1, vol. 2. T. Young (ed. G. Peacock), 1855, Miscellaneous Works of the late Thomas Young, London: J. Murray, vol. 1. Further reading Some English translations of works by Fresnel are included in the above Bibliography. For a more comprehensive list, see "External links" below. The most detailed secondary source on Fresnel in English is apparently Buchwald 1989 —in which Fresnel, although not named in the title, is clearly the central character. On lighthouse lenses, this article heavily cites Levitt 2013, Elton 2009, and Thomas Tag at the U.S. Lighthouse Society (see "External links" below). All three authors deal not only with Fresnel's contributions but also with later innovations that are not mentioned here (see Fresnel lens: History). By comparison with the volume and impact of his scientific and technical writings, biographical information on Fresnel is remarkably scarce. There is no book-length critical biography of him, and anyone who proposes to write one must confront the fact that the letters published in his Oeuvres complètes—contrary to the title—are heavily redacted. In the words of Robert H. Silliman (1967, p. 6n): "By an unhappy judgment of the editors, dictated in part, one suspects, by political expediency, the letters appear in fragmentary form, preserving almost nothing beyond the technical discussions of Fresnel and his correspondents." It is not clear from the secondary sources whether the manuscripts of those letters are still extant (cf. Grattan-Guinness, 1990, p.854n). External links List of English translations of works by Augustin Fresnel at Zenodo. United States Lighthouse Society, especially "Fresnel Lenses". . . 1788 births 1827 deaths 19th-century deaths from tuberculosis 19th-century French physicists Burials at Père Lachaise Cemetery Corps des ponts École des Ponts ParisTech alumni École Polytechnique alumni Foreign Members of the Royal Society French civil engineers French humanitarians French Roman Catholics History of physics Tuberculosis deaths in France Jansenists Light Lighthouses Members of the French Academy of Sciences Optical physicists People from Eure Physical optics

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1152

https://en.wikipedia.org/wiki/Alan%20Garner

Alan Garner

Alan Garner (born 17 October 1934) is an English novelist best known for his children's fantasy novels and his retellings of traditional British folk tales. Much of his work is rooted in the landscape, history and folklore of his native county of Cheshire, North West England, being set in the region and making use of the native Cheshire dialect. Born in Congleton, Garner grew up around the nearby town of Alderley Edge, and spent much of his youth in the wooded area known locally as "The Edge", where he gained an early interest in the folklore of the region. Studying at Manchester Grammar School and then briefly at Oxford University, in 1957 he moved to the village of Blackden, where he bought and renovated an Early Modern Period (circa 1590) building known as Toad Hall. His first novel, The Weirdstone of Brisingamen, was published in 1960. A children's fantasy novel set on the Edge, it incorporated elements of local folklore in its plot and characters. Garner wrote a sequel, The Moon of Gomrath (1963), and a third book, Boneland (2012). He wrote several fantasy novels, including Elidor (1965), The Owl Service (1967) and Red Shift (1973). Turning away from fantasy as a genre, Garner produced The Stone Book Quartet (1979), a series of four short novellas detailing a day in the life of four generations of his family. He also published a series of British folk tales which he had rewritten in a series of books entitled Alan Garner's Fairy Tales of Gold (1979), Alan Garner's Book of British Fairy Tales (1984) and A Bag of Moonshine (1986). In his subsequent novels, Strandloper (1996) and Thursbitch (2003), he continued writing tales revolving around Cheshire, although without the fantasy elements which had characterised his earlier work. Biography Early life: 1934–56 Garner was born in the front room of his grandmother's house in Congleton, Cheshire, on 17 October 1934. He was raised in nearby Alderley Edge, a well-to-do village that had effectively become a suburb of Manchester. His "rural working-class family", had been connected to Alderley Edge since at least the sixteenth century, and could be traced back to the death of William Garner in 1592. Garner has stated that his family had passed on "a genuine oral tradition" involving folk tales about The Edge, which included a description of a king and his army of knights who slept under it, guarded by a wizard. In the mid-nineteenth century Alan's great-great grandfather Robert had carved the face of a bearded wizard onto the face of a cliff next to a well, known locally at that time as the Wizard's Well. Robert Garner and his other relatives had all been craftsmen, and, according to Garner, each successive generation had tried to "improve on, or do something different from, the previous generation". Garner's grandfather, Joseph Garner, "could read, but didn't and so was virtually unlettered". Instead he taught his grandson the folk tales he knew about The Edge. Garner later remarked that as a result he was "aware of [the Edge's] magic" as a child, and he and his friends often played there. The story of the king and the wizard living under the hill played an important part in his life, becoming, he explained, "deeply embedded in my psyche" and heavily influencing his later novels. Garner faced several life-threatening childhood illnesses, which left him bed ridden for much of the time. He attended a local village school, where he found that, despite being praised for his intelligence, he was punished for speaking in his native Cheshire dialect; for instance, when he was six his primary school teacher washed his mouth out with soapy water. Garner then won a place at Manchester Grammar School, where he received his secondary education; entry was means-tested, resulting in his school fees being waived. Rather than focusing his interest on creative writing, it was here that he excelled at sprinting. He used to go jogging along the highway, and later claimed that in doing so he was sometimes accompanied by the mathematician Alan Turing, who shared his fascination with the Disney film Snow White and the Seven Dwarfs. Garner was then conscripted into national service, serving for a time with the Royal Artillery while posted to Woolwich in Southeast London. At school, Garner had developed a keen interest in the work of Aeschylus and Homer, as well as the Ancient Greek language. Thus, he decided to pursue the study of Classics at Magdalen College, Oxford, passing his entrance exams in January 1953; at the time he had thoughts of becoming a professional academic. He was the first member of his family to receive anything more than a basic education, and he noted that this removed him from his "cultural background" and led to something of a schism with other members of his family, who "could not cope with me, and I could not cope with" them. Looking back, he remarked, "I soon learned that it was not a good idea to come home excited over irregular verbs". In 1955, he joined the university theatrical society, playing the role of Mark Antony in a performance of William Shakespeare's Antony and Cleopatra where he co-starred alongside Dudley Moore and where Kenneth Baker was the stage manager. In August 1956, he decided that he wished to devote himself to novel writing, and decided to abandon his university education without taking a degree; he left Oxford in late 1956. He nevertheless felt that the academic rigour which he learned during his university studies has remained "a permanent strength through all my life". The Weirdstone of Brisingamen and The Moon of Gomrath: 1957–64 Aged 22, Garner was out cycling when he came across a hand-painted sign announcing that an agricultural cottage in Toad Hall – a Late Medieval building situated in Blackden, seven miles from Alderley Edge – was on sale for £510. Although he personally could not afford it, he was lent the money by the local Oddfellow lodge, enabling him to purchase and move into the cottage in June 1957. In the late nineteenth century the Hall had been divided into two agricultural labourers' cottages, but Garner was able to purchase the second for £150 about a year later; he proceeded to knock down the dividing walls and convert both halves back into a single home. Garner had begun writing his first novel, The Weirdstone of Brisingamen: A Tale of Alderley, in September 1956. However it was while at Toad Hall that he finished the book. Set in Alderley Edge, it revolves around two children, Susan and Colin, who are sent to live in the area with their mother's old nursemaid, Bess, and her husband, Gowther Mossock. While exploring the Edge, they encounter a race of malevolent creatures, the svart alfar, who dwell in the Edge's abandoned mines and who seem intent on capturing them. They are rescued by the wizard Cadellin, who reveals that the forces of darkness are massing at the Edge in search of a powerful magical talisman, the eponymous "weirdstone of Brisingamen". Whilst writing in his spare time Garner attempted to gain employment as a teacher, but soon gave that up, believing that "I couldn't write and teach; the energies were too similar." Instead, he worked off and on as a general labourer for four years, remaining unemployed for much of that time. Garner sent his debut novel to the publishing company Collins, where it was picked up by the company's head, Sir William Collins, who was on the look out for new fantasy novels following the recent commercial and critical success of J. R. R. Tolkien's The Lord of the Rings (1954–55). Garner, who went on to become a personal friend of Collins, would later relate that "Billy Collins saw a title with funny-looking words in it on the stockpile, and he decided to publish it." On its release in 1960, The Weirdstone of Brisingamen proved to be a critical and commercial success, later being described as "a tour de force of the imagination, a novel that showed almost every writer who came afterwards what it was possible to achieve in novels ostensibly published for children." Garner himself however would later denounce his first novel as "a fairly bad book" in 1968. With his first book published, Garner abandoned his work as a labourer and gained a job as a freelance television reporter, living a "hand to mouth" lifestyle on a "shoestring" budget. He also began a sequel to The Weirdstone of Brisingamen, which would be known as The Moon of Gomrath. The Moon of Gomrath also revolves around the adventures of Colin and Susan, with the latter being possessed by a malevolent creature called the Brollachan who has recently entered the world. With the help of the wizard Cadellin, the Brollachan is exorcised, but Susan's soul also leaves her body, being sent to another dimension, leaving Colin to find a way to bring it back. Critic Neil Philip characterised it as "an artistic advance" but "a less satisfying story". In a 1989 interview, Garner stated that he had left scope for a third book following the adventures of Colin and Susan, envisioning a trilogy, but that he had intentionally decided not to write it, instead moving on to write something different. However Boneland, the conclusion to the sequence, was belatedly published in August 2012. Elidor, The Owl Service and Red Shift: 1964–73 In 1962, Garner began work on a radio play entitled Elidor, which eventually became a novel of the same name. Set in contemporary Manchester, Elidor tells the story of four children who enter a derelict Victorian church and find a portal to the magical realm of Elidor. In Elidor, they are entrusted by King Malebron to help rescue four treasures which have been stolen by the forces of evil, who are attempting to take control of the kingdom. The children succeed and return to Manchester with the treasures, but are pursued by the malevolent forces who need the items to seal their victory. Before writing Elidor, Garner had seen a dinner service set which could be arranged to make pictures of either flowers or owls. Inspired by this design, he produced his fourth novel, The Owl Service. The story, which was heavily influenced by the Medieval Welsh tale of Math fab Mathonwy from the Mabinogion, was critically acclaimed, winning both the Carnegie Medal and Guardian Children's Fiction Prize. It also sparked discussions among critics as to whether Garner should properly be considered a children's writer, given that this book in particular was deemed equally suitable for an adult readership. It took Garner six years to write his next novel, Red Shift. The book centres on three intertwined love stories, one set in the present, another during the English Civil War, and the third in the second century CE. Philip referred to it as "a complex book but not a complicated one: the bare lines of story and emotion stand clear". Academic specialist in children's literature Maria Nikolajeva characterised Red Shift as "a difficult book" for an unprepared reader, identifying its main themes as those of "loneliness and failure to communicate". Ultimately, she thought that repeated re-readings of the novel bring about the realisation that "it is a perfectly realistic story with much more depth and psychologically more credible than the most so-called "realistic" juvenile novels." The Stone Book series and folkloric collections: 1974–94 From 1976 to 1978, Garner published a series of four novellas, which have come to be collectively known as The Stone Book quartet: The Stone Book, Granny Reardun, The Aimer Gate, and Tom Fobble's Day. Each focused on a day in the life of a child in the Garner family, each from a different generation. In a 1989 interview, Garner noted that although writing The Stone Book Quartet had been "exhausting", it had been "the most rewarding of everything" he'd done to date. Philip described the quartet as "a complete command of the material he had been working and reworking since the start of his career". Garner pays particular attention to language, and strives to render the cadence of the Cheshire tongue in modern English. This he explains by the sense of anger he felt on reading Sir Gawain and the Green Knight: the footnotes would not have been needed by his father. In 1981, the literary critic Neil Philip published an analysis of Garner's novels as A Fine Anger, which was based on his doctoral thesis, produced for the University of London in 1980. In this study he noted that "The Stone Book quartet marks a watershed in Garner's writing career, and provides a suitable moment for an evaluation of his work thus far." Strandloper, Thursbitch, Boneland, and Treacle Walker: 1995–present In 1996, Garner's novel Strandloper was published. His collection of essays and public talks, The Voice That Thunders, contains much autobiographical material (including an account of his life with bipolar disorder), as well as critical reflection upon folklore and language, literature and education, the nature of myth and time. In The Voice That Thunders he reveals the commercial pressure placed upon him during the decade-long drought which preceded Strandloper to 'forsake "literature", and become instead a "popular" writer, cashing in on my established name by producing sequels to, and making series of, the earlier books'. Garner feared that "making series ... would render sterile the existing work, the life that produced it, and bring about my artistic and spiritual death" and felt unable to comply. Garner's novel Thursbitch was published in 2003. Garner's novel, Boneland, was published in 2012, nominally completing a trilogy begun some 50 years earlier with The Weirdstone of Brisingamen. The novel Treacle Walker was published in October 2021. Where Shall We Run To? 2018 In August 2018 Garner published his only set of memoirs, Where Shall We Run To?, which describes his childhood during the Second World War. Personal life With his first wife Ann Cook he had three children. In 1972, he married for a second time, this time to Griselda Greaves, a teacher and critic with whom he had two children. In a 2014 interview conducted with Mike Pitts for British Archaeology magazine, Garner stated that "I don't have anything to do with the literary world. I avoid writers. I don't like them. Most of my close personal friends are professional archaeologists." Literary style Although Garner's early work is often labelled as "children's literature", Garner himself rejects such a description, informing one interviewer that "I certainly have never written for children" but that instead he has always written purely for himself. Neil Philip, in his critical study of Garner's work (1981), commented that up till that point, "Everything Alan Garner has published has been published for children", although he went on to relate that "It may be that Garner's is a case" where the division between children's and adult's literature is "meaningless" and that his fiction is instead "enjoyed by a type of person, no matter what their age." Philip offered the opinion that the "essence of his work" was "the struggle to render the complex in simple, bare terms; to couch the abstract in the concrete and communicate it directly to the reader". He added that Garner's work is "intensely autobiographical, in both obvious and subtle ways". Highlighting Garner's use of mythological and folkloric sources, Philip stated that his work explores "the disjointed and troubled psychological and emotional landscape of the twentieth century through the symbolism of myth and folklore." He also expressed the opinion that "Time is Garner's most consistent theme". The English author and academic Catherine Butler noted that Garner was attentive to the "geological, archaeological and cultural history of his settings, and careful to integrate his fiction with the physical reality beyond the page." As a part of this, Garner had included maps of Alderley Edge in both The Weirdstone of Brisingamen and The Moon of Gomrath. Garner has spent much time investigating the areas that he deals with in his books; writing in the Times Literary Supplement in 1968, Garner commented that in preparation for writing his book Elidor: I had to read extensively textbooks on physics, Celtic symbolism, unicorns, medieval watermarks, megalithic archaeology; study the writings of Jung; brush up my Plato; visit Avebury, Silbury and Coventry Cathedral; spend a lot of time with demolition gangs on slum clearance sites; and listen to the whole of Britten's War Requiem nearly every day. Recognition and legacy In a paper published in the Children's Literature Association Quarterly, Maria Nikolajeva characterised Garner as "one of the most controversial" authors of modern children's literature. In the fiftieth anniversary edition of The Weirdstone of Brisingamen, published by HarperCollins in 2010, several notable British fantasy novelists praised Garner and his work. Susan Cooper related that "The power and range of Alan Garner's astounding talent has grown with every book he's written", whilst David Almond called him one of Britain's "greatest writers" whose works "really matter". Philip Pullman, the author of the His Dark Materials trilogy, went further when he remarked that: Garner is indisputably the great originator, the most important British writer of fantasy since Tolkien, and in many respects better than Tolkien, because deeper and more truthful... Any country except Britain would have long ago recognised his importance, and celebrated it with postage stamps and statues and street-names. But that's the way with us: our greatest prophets go unnoticed by the politicians and the owners of media empires. I salute him with the most heartfelt respect and admiration. Another British fantasy writer, Neil Gaiman, claimed that "Garner's fiction is something special" in that it was "smart and challenging, based in the here and the now, in which real English places emerged from the shadows of folklore, and in which people found themselves walking, living and battling their way through the dreams and patterns of myth." Praise also came from Nick Lake, the editorial director of HarperCollins Children's Books, who proclaimed that "Garner is, quite simply, one of the greatest and most influential writers this country has ever produced." Awards The biennial Hans Christian Andersen Award conferred by the International Board on Books for Young People is the highest recognition available to a writer or illustrator of children's books. Garner was the sole runner-up for the writing award in 1978. Garner was appointed Officer of the Order of the British Empire (OBE) for services to literature in the 2001 New Year's Honours list. He received the British Fantasy Society's occasional Karl Edward Wagner Award in 2003 and the World Fantasy Award for Life Achievement in 2012. In January 2011, the University of Warwick awarded the degree of Doctor of Letters (honoris causa). On that occasion he gave a half-hour interview about his work. He has also been awarded honorary doctorates from the University of Salford (2011) and the University of Huddersfield in (2012). He has been recognised several times for particular works. The Owl Service (1967) won both the Carnegie Medal and the Guardian Children's Fiction Prize, For the 70th anniversary of the Carnegie in 2007 it was named one of the top ten Medal-winning works, selected by a panel to compose the ballot for a public election of the all-time favourite. The Weirdstone of Brisingamen (1960) was named to the Lewis Carroll Shelf Award list by the University of Wisconsin–Madison School of Education in 1970, denoting that it "belongs on the same shelf" with the 1865 classic Alice in Wonderland and its sequel. The Stone Book (1976), first in the Stone Book series, won the 1996 Phoenix Award as the best English-language children's book that did not win a major award when it was originally published twenty years earlier. The 1981 film Images won First Prize at the Chicago International Film Festival Television, radio, and other adaptations Elidor was read in instalments by John Stride for the BBC's Jackanory programme in June 1968. The Owl Service (1969), a British TV series transmitted by Granada Television based on Garner's novel of the same name. A second adaptation of Elidor was read on a BBC Radio 4 in July 1972. Red Shift (BBC, transmitted 17 January 1978); directed by John Mackenzie; part of the BBC's Play for Today series. To Kill a King (1980), part of the BBC series of plays on supernatural themes, Leap in the Dark: an atmospheric story about a writer overcoming depression and writer's block. The hero's home appears to be Garner's own house. The Keeper (ITV, transmitted 13 June 1983), an episode of the ITV children's series Dramarama: Spooky series Garner and Don Webb adapted Elidor as a BBC children's television series shown in 1995, comprising six half-hour episodes starring Damian Zuk as Roland and Suzanne Shaw as Helen. The Owl Service was adapted for the stage in 2004 by The Drum Theatre in Plymouth. Elidor was dramatised as a radio play in four-parts by Don Webb, broadcast on BBC Radio 4 Extra in 2011. Works Novels The Weirdstone of Brisingamen, 1960 The Moon of Gomrath, 1963 Elidor, 1965 The Owl Service, 1967 Red Shift, 1973 Strandloper, 1996 Thursbitch, 2003 Boneland, 2012 Treacle Walker, 2021 Short story collections The Guizer: A Book of Fools, 1975 The Stone Book Quartet, 1979 The Lad of the Gad, 1980 Fairytales of Gold, 1980, (Illustrated by Michael Foreman). Book of British Fairy Tales, 1984, (Illustrated by Derek Collard). A Bag of Moonshine, 1986, (Illustrated by P. J. Lynch). Once Upon a Time, 1993 Collected Folk Tales, 2011 Other books Holly from the Bongs: A Nativity Play, 1966 The Old Man of Mow, 1967 The Breadhorse, 1975 Jack and the Beanstalk, 1992, (Illustrated by Julek Heller). The Little Red Hen, 1997 The Well of the Wind, 1998 Grey Wolf, Prince Jack and the Firebird, 1998 The Voice That Thunders, 1997 Where Shall We Run To?, 2018 See also References Footnotes Sources Further reading External links Alan Garner coverage by The Guardian'' English short story writers English children's writers English fantasy writers Carnegie Medal in Literature winners Fellows of the Royal Society of Literature Guardian Children's Fiction Prize winners Officers of the Order of the British Empire Alumni of Magdalen College, Oxford People educated at Manchester Grammar School People from Alderley Edge People from Congleton People with bipolar disorder World Fantasy Award-winning writers 1934 births Living people English male novelists

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1160

https://en.wikipedia.org/wiki/Automorphism

Automorphism

In mathematics, an automorphism is an isomorphism from a mathematical object to itself. It is, in some sense, a symmetry of the object, and a way of mapping the object to itself while preserving all of its structure. The set of all automorphisms of an object forms a group, called the automorphism group. It is, loosely speaking, the symmetry group of the object. Definition In the context of abstract algebra, a mathematical object is an algebraic structure such as a group, ring, or vector space. An automorphism is simply a bijective homomorphism of an object with itself. (The definition of a homomorphism depends on the type of algebraic structure; see, for example, group homomorphism, ring homomorphism, and linear operator). The identity morphism (identity mapping) is called the trivial automorphism in some contexts. Respectively, other (non-identity) automorphisms are called nontrivial automorphisms. The exact definition of an automorphism depends on the type of "mathematical object" in question and what, precisely, constitutes an "isomorphism" of that object. The most general setting in which these words have meaning is an abstract branch of mathematics called category theory. Category theory deals with abstract objects and morphisms between those objects. In category theory, an automorphism is an endomorphism (i.e., a morphism from an object to itself) which is also an isomorphism (in the categorical sense of the word, meaning there exists a right and left inverse endomorphism). This is a very abstract definition since, in category theory, morphisms are not necessarily functions and objects are not necessarily sets. In most concrete settings, however, the objects will be sets with some additional structure and the morphisms will be functions preserving that structure. Automorphism group If the automorphisms of an object form a set (instead of a proper class), then they form a group under composition of morphisms. This group is called the automorphism group of . Closure Composition of two automorphisms is another automorphism. Associativity It is part of the definition of a category that composition of morphisms is associative. Identity The identity is the identity morphism from an object to itself, which is an automorphism. Inverses By definition every isomorphism has an inverse which is also an isomorphism, and since the inverse is also an endomorphism of the same object it is an automorphism. The automorphism group of an object X in a category C is denoted AutC(X), or simply Aut(X) if the category is clear from context. Examples In set theory, an arbitrary permutation of the elements of a set X is an automorphism. The automorphism group of X is also called the symmetric group on X. In elementary arithmetic, the set of integers, Z, considered as a group under addition, has a unique nontrivial automorphism: negation. Considered as a ring, however, it has only the trivial automorphism. Generally speaking, negation is an automorphism of any abelian group, but not of a ring or field. A group automorphism is a group isomorphism from a group to itself. Informally, it is a permutation of the group elements such that the structure remains unchanged. For every group G there is a natural group homomorphism G → Aut(G) whose image is the group Inn(G) of inner automorphisms and whose kernel is the center of G. Thus, if G has trivial center it can be embedded into its own automorphism group. In linear algebra, an endomorphism of a vector space V is a linear operator V → V. An automorphism is an invertible linear operator on V. When the vector space is finite-dimensional, the automorphism group of V is the same as the general linear group, GL(V). (The algebraic structure of all endomorphisms of V is itself an algebra over the same base field as V, whose invertible elements precisely consist of GL(V).) A field automorphism is a bijective ring homomorphism from a field to itself. In the cases of the rational numbers (Q) and the real numbers (R) there are no nontrivial field automorphisms. Some subfields of R have nontrivial field automorphisms, which however do not extend to all of R (because they cannot preserve the property of a number having a square root in R). In the case of the complex numbers, C, there is a unique nontrivial automorphism that sends R into R: complex conjugation, but there are infinitely (uncountably) many "wild" automorphisms (assuming the axiom of choice). Field automorphisms are important to the theory of field extensions, in particular Galois extensions. In the case of a Galois extension L/K the subgroup of all automorphisms of L fixing K pointwise is called the Galois group of the extension. The automorphism group of the quaternions (H) as a ring are the inner automorphisms, by the Skolem–Noether theorem: maps of the form . This group is isomorphic to SO(3), the group of rotations in 3-dimensional space. The automorphism group of the octonions (O) is the exceptional Lie group G2. In graph theory an automorphism of a graph is a permutation of the nodes that preserves edges and non-edges. In particular, if two nodes are joined by an edge, so are their images under the permutation. In geometry, an automorphism may be called a motion of the space. Specialized terminology is also used: In metric geometry an automorphism is a self-isometry. The automorphism group is also called the isometry group. In the category of Riemann surfaces, an automorphism is a biholomorphic map (also called a conformal map), from a surface to itself. For example, the automorphisms of the Riemann sphere are Möbius transformations. An automorphism of a differentiable manifold M is a diffeomorphism from M to itself. The automorphism group is sometimes denoted Diff(M). In topology, morphisms between topological spaces are called continuous maps, and an automorphism of a topological space is a homeomorphism of the space to itself, or self-homeomorphism (see homeomorphism group). In this example it is not sufficient for a morphism to be bijective to be an isomorphism. History One of the earliest group automorphisms (automorphism of a group, not simply a group of automorphisms of points) was given by the Irish mathematician William Rowan Hamilton in 1856, in his icosian calculus, where he discovered an order two automorphism, writing: so that is a new fifth root of unity, connected with the former fifth root by relations of perfect reciprocity. Inner and outer automorphisms In some categories—notably groups, rings, and Lie algebras—it is possible to separate automorphisms into two types, called "inner" and "outer" automorphisms. In the case of groups, the inner automorphisms are the conjugations by the elements of the group itself. For each element a of a group G, conjugation by a is the operation given by (or a−1ga; usage varies). One can easily check that conjugation by a is a group automorphism. The inner automorphisms form a normal subgroup of Aut(G), denoted by Inn(G); this is called Goursat's lemma. The other automorphisms are called outer automorphisms. The quotient group is usually denoted by Out(G); the non-trivial elements are the cosets that contain the outer automorphisms. The same definition holds in any unital ring or algebra where a is any invertible element. For Lie algebras the definition is slightly different. See also Antiautomorphism Automorphism (in Sudoku puzzles) Characteristic subgroup Endomorphism ring Frobenius automorphism Morphism Order automorphism (in order theory). Relation-preserving automorphism Fractional Fourier transform References External links Automorphism at Encyclopaedia of Mathematics Morphisms Abstract algebra Symmetry

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1164

https://en.wikipedia.org/wiki/Artificial%20intelligence

Artificial intelligence

Artificial intelligence (AI) is intelligence demonstrated by machines, as opposed to natural intelligence displayed by animals including humans. Leading AI textbooks define the field as the study of "intelligent agents": any system that perceives its environment and takes actions that maximize its chance of achieving its goals. Some popular accounts use the term "artificial intelligence" to describe machines that mimic "cognitive" functions that humans associate with the human mind, such as "learning" and "problem solving", however, this definition is rejected by major AI researchers. AI applications include advanced web search engines (e.g., Google), recommendation systems (used by YouTube, Amazon and Netflix), understanding human speech (such as Siri and Alexa), self-driving cars (e.g., Tesla), automated decision-making and competing at the highest level in strategic game systems (such as chess and Go). As machines become increasingly capable, tasks considered to require "intelligence" are often removed from the definition of AI, a phenomenon known as the AI effect. For instance, optical character recognition is frequently excluded from things considered to be AI, having become a routine technology. Artificial intelligence was founded as an academic discipline in 1956, and in the years since has experienced several waves of optimism, followed by disappointment and the loss of funding (known as an "AI winter"), followed by new approaches, success and renewed funding. AI research has tried and discarded many different approaches since its founding, including simulating the brain, modeling human problem solving, formal logic, large databases of knowledge and imitating animal behavior. In the first decades of the 21st century, highly mathematical statistical machine learning has dominated the field, and this technique has proved highly successful, helping to solve many challenging problems throughout industry and academia. The various sub-fields of AI research are centered around particular goals and the use of particular tools. The traditional goals of AI research include reasoning, knowledge representation, planning, learning, natural language processing, perception, and the ability to move and manipulate objects. General intelligence (the ability to solve an arbitrary problem) is among the field's long-term goals. To solve these problems, AI researchers have adapted and integrated a wide range of problem-solving techniques—including search and mathematical optimization, formal logic, artificial neural networks, and methods based on statistics, probability and economics. AI also draws upon computer science, psychology, linguistics, philosophy, and many other fields. The field was founded on the assumption that human intelligence "can be so precisely described that a machine can be made to simulate it". This raises philosophical arguments about the mind and the ethics of creating artificial beings endowed with human-like intelligence. These issues have been explored by myth, fiction, and philosophy since antiquity. Science fiction and futurology have also suggested that, with its enormous potential and power, AI may become an existential risk to humanity. History Artificial beings with intelligence appeared as storytelling devices in antiquity, and have been common in fiction, as in Mary Shelley's Frankenstein or Karel Čapek's R.U.R. These characters and their fates raised many of the same issues now discussed in the ethics of artificial intelligence. The study of mechanical or "formal" reasoning began with philosophers and mathematicians in antiquity. The study of mathematical logic led directly to Alan Turing's theory of computation, which suggested that a machine, by shuffling symbols as simple as "0" and "1", could simulate any conceivable act of mathematical deduction. This insight that digital computers can simulate any process of formal reasoning is known as the Church–Turing thesis. The Church-Turing thesis, along with concurrent discoveries in neurobiology, information theory and cybernetics, led researchers to consider the possibility of building an electronic brain. The first work that is now generally recognized as AI was McCullouch and Pitts' 1943 formal design for Turing-complete "artificial neurons". When access to digital computers became possible in the mid-1950s, AI research began to explore the possibility that human intelligence could be reduced to step-by-step symbol manipulation, known as Symbolic AI or GOFAI. Approaches based on cybernetics or artificial neural networks were abandoned or pushed into the background. The field of AI research was born at a workshop at Dartmouth College in 1956. The attendees became the founders and leaders of AI research. They and their students produced programs that the press described as "astonishing": computers were learning checkers strategies, solving word problems in algebra, proving logical theorems and speaking English. By the middle of the 1960s, research in the U.S. was heavily funded by the Department of Defense and laboratories had been established around the world. Researchers in the 1960s and the 1970s were convinced that symbolic approaches would eventually succeed in creating a machine with artificial general intelligence and considered this the goal of their field. Herbert Simon predicted, "machines will be capable, within twenty years, of doing any work a man can do". Marvin Minsky agreed, writing, "within a generation ... the problem of creating 'artificial intelligence' will substantially be solved". They failed to recognize the difficulty of some of the remaining tasks. Progress slowed and in 1974, in response to the criticism of Sir James Lighthill and ongoing pressure from the US Congress to fund more productive projects, both the U.S. and British governments cut off exploratory research in AI. The next few years would later be called an "AI winter", a period when obtaining funding for AI projects was difficult. In the early 1980s, AI research was revived by the commercial success of expert systems, a form of AI program that simulated the knowledge and analytical skills of human experts. By 1985, the market for AI had reached over a billion dollars. At the same time, Japan's fifth generation computer project inspired the U.S and British governments to restore funding for academic research. However, beginning with the collapse of the Lisp Machine market in 1987, AI once again fell into disrepute, and a second, longer-lasting winter began. Many researchers began to doubt that the symbolic approach would be able to imitate all the processes of human cognition, especially perception, robotics, learning and pattern recognition. A number of researchers began to look into "sub-symbolic" approaches to specific AI problems. Robotics researchers, such as Rodney Brooks, rejected symbolic AI and focused on the basic engineering problems that would allow robots to move, survive, and learn their environment. Interest in neural networks and "connectionism" was revived by Geoffrey Hinton, David Rumelhart and others in the middle of the 1980s. Soft computing tools were developed in the 80s, such as neural networks, fuzzy systems, Grey system theory, evolutionary computation and many tools drawn from statistics or mathematical optimization. AI gradually restored its reputation in the late 1990s and early 21st century by finding specific solutions to specific problems. The narrow focus allowed researchers to produce verifiable results, exploit more mathematical methods, and collaborate with other fields (such as statistics, economics and mathematics). By 2000, solutions developed by AI researchers were being widely used, although in the 1990s they were rarely described as "artificial intelligence". Faster computers, algorithmic improvements, and access to large amounts of data enabled advances in machine learning and perception; data-hungry deep learning methods started to dominate accuracy benchmarks around 2012. According to Bloomberg's Jack Clark, 2015 was a landmark year for artificial intelligence, with the number of software projects that use AI within Google increased from a "sporadic usage" in 2012 to more than 2,700 projects. He attributes this to an increase in affordable neural networks, due to a rise in cloud computing infrastructure and to an increase in research tools and datasets. In a 2017 survey, one in five companies reported they had "incorporated AI in some offerings or processes". The amount of research into AI (measured by total publications) increased by 50% in the years 2015–2019. Numerous academic researchers became concerned that AI was no longer pursuing the original goal of creating versatile, fully intelligent machines. Much of current research involves statistical AI, which is overwhelmingly used to solve specific problems, even highly successful techniques such as deep learning. This concern has led to the subfield artificial general intelligence (or "AGI"), which had several well-funded institutions by the 2010s. Goals The general problem of simulating (or creating) intelligence has been broken down into sub-problems. These consist of particular traits or capabilities that researchers expect an intelligent system to display. The traits described below have received the most attention. Reasoning, problem solving Early researchers developed algorithms that imitated step-by-step reasoning that humans use when they solve puzzles or make logical deductions. By the late 1980s and 1990s, AI research had developed methods for dealing with uncertain or incomplete information, employing concepts from probability and economics. Many of these algorithms proved to be insufficient for solving large reasoning problems because they experienced a "combinatorial explosion": they became exponentially slower as the problems grew larger. Even humans rarely use the step-by-step deduction that early AI research could model. They solve most of their problems using fast, intuitive judgments. Knowledge representation Knowledge representation and knowledge engineering allow AI programs to answer questions intelligently and make deductions about real world facts. A representation of "what exists" is an ontology: the set of objects, relations, concepts, and properties formally described so that software agents can interpret them. The most general ontologies are called upper ontologies, which attempt to provide a foundation for all other knowledge and act as mediators between domain ontologies that cover specific knowledge about a particular knowledge domain (field of interest or area of concern). A truly intelligent program would also need access to commonsense knowledge; the set of facts that an average person knows. The semantics of an ontology is typically represented in a description logic, such as the Web Ontology Language. AI research has developed tools to represent specific domains, such as: objects, properties, categories and relations between objects; situations, events, states and time; causes and effects; knowledge about knowledge (what we know about what other people know);. default reasoning (things that humans assume are true until they are told differently and will remain true even when other facts are changing); as well as other domains. Among the most difficult problems in AI are: the breadth of commonsense knowledge (the number of atomic facts that the average person knows is enormous); and the sub-symbolic form of most commonsense knowledge (much of what people know is not represented as "facts" or "statements" that they could express verbally). Formal knowledge representations are used in content-based indexing and retrieval, scene interpretation, clinical decision support, knowledge discovery (mining "interesting" and actionable inferences from large databases), and other areas. Planning An intelligent agent that can plan makes a representation of the state of the world, makes predictions about how their actions will change it and makes choices that maximize the utility (or "value") of the available choices. In classical planning problems, the agent can assume that it is the only system acting in the world, allowing the agent to be certain of the consequences of its actions. However, if the agent is not the only actor, then it requires that the agent reason under uncertainty, and continuously re-assess its environment and adapt. Multi-agent planning uses the cooperation and competition of many agents to achieve a given goal. Emergent behavior such as this is used by evolutionary algorithms and swarm intelligence. Learning Machine learning (ML), a fundamental concept of AI research since the field's inception, is the study of computer algorithms that improve automatically through experience. Unsupervised learning finds patterns in a stream of input. Supervised learning requires a human to label the input data first, and comes in two main varieties: classification and numerical regression. Classification is used to determine what category something belongs in—the program sees a number of examples of things from several categories and will learn to classify new inputs. Regression is the attempt to produce a function that describes the relationship between inputs and outputs and predicts how the outputs should change as the inputs change. Both classifiers and regression learners can be viewed as "function approximators" trying to learn an unknown (possibly implicit) function; for example, a spam classifier can be viewed as learning a function that maps from the text of an email to one of two categories, "spam" or "not spam". In reinforcement learning the agent is rewarded for good responses and punished for bad ones. The agent classifies its responses to form a strategy for operating in its problem space. Transfer learning is when knowledge gained from one problem is applied to a new problem. Computational learning theory can assess learners by computational complexity, by sample complexity (how much data is required), or by other notions of optimization. Natural language processing Natural language processing (NLP) allows machines to read and understand human language. A sufficiently powerful natural language processing system would enable natural-language user interfaces and the acquisition of knowledge directly from human-written sources, such as newswire texts. Some straightforward applications of NLP include information retrieval, question answering and machine translation. Symbolic AI used formal syntax to translate the deep structure of sentences into logic. This failed to produce useful applications, due to the intractability of logic and the breadth of commonsense knowledge. Modern statistical techniques include co-occurrence frequencies (how often one word appears near another), "Keyword spotting" (searching for a particular word to retrieve information), transformer-based deep learning (which finds patterns in text), and others. They have achieved acceptable accuracy at the page or paragraph level, and, by 2019, could generate coherent text. Perception Machine perception is the ability to use input from sensors (such as cameras, microphones, wireless signals, and active lidar, sonar, radar, and tactile sensors) to deduce aspects of the world. Applications include speech recognition, facial recognition, and object recognition. Computer vision is the ability to analyze visual input. Motion and manipulation AI is heavily used in robotics. Localization is how a robot knows its location and maps its environment. When given a small, static, and visible environment, this is easy; however, dynamic environments, such as (in endoscopy) the interior of a patient's breathing body, pose a greater challenge. Motion planning is the process of breaking down a movement task into "primitives" such as individual joint movements. Such movement often involves compliant motion, a process where movement requires maintaining physical contact with an object. Robots can learn from experience how to move efficiently despite the presence of friction and gear slippage. Social intelligence Affective computing is an interdisciplinary umbrella that comprises systems which recognize, interpret, process, or simulate human feeling, emotion and mood. For example, some virtual assistants are programmed to speak conversationally or even to banter humorously; it makes them appear more sensitive to the emotional dynamics of human interaction, or to otherwise facilitate human–computer interaction. However, this tends to give naïve users an unrealistic conception of how intelligent existing computer agents actually are. Moderate successes related to affective computing include textual sentiment analysis and, more recently, multimodal sentiment analysis), wherein AI classifies the affects displayed by a videotaped subject. General intelligence A machine with general intelligence can solve a wide variety of problems with a breadth and versatility similar to human intelligence. There are several competing ideas about how to develop artificial general intelligence. Hans Moravec and Marvin Minsky argue that work in different individual domains can be incorporated into an advanced multi-agent system or cognitive architecture with general intelligence. Pedro Domingos hopes that there is a conceptually straightforward, but mathematically difficult, "master algorithm" that could lead to AGI. Others believe that anthropomorphic features like an artificial brain or simulated child development will someday reach a critical point where general intelligence emerges. Tools Search and optimization Many problems in AI can be solved theoretically by intelligently searching through many possible solutions: Reasoning can be reduced to performing a search. For example, logical proof can be viewed as searching for a path that leads from premises to conclusions, where each step is the application of an inference rule. Planning algorithms search through trees of goals and subgoals, attempting to find a path to a target goal, a process called means-ends analysis. Robotics algorithms for moving limbs and grasping objects use local searches in configuration space. Simple exhaustive searches are rarely sufficient for most real-world problems: the search space (the number of places to search) quickly grows to astronomical numbers. The result is a search that is too slow or never completes. The solution, for many problems, is to use "heuristics" or "rules of thumb" that prioritize choices in favor of those more likely to reach a goal and to do so in a shorter number of steps. In some search methodologies, heuristics can also serve to eliminate some choices unlikely to lead to a goal (called "pruning the search tree"). Heuristics supply the program with a "best guess" for the path on which the solution lies. Heuristics limit the search for solutions into a smaller sample size. A very different kind of search came to prominence in the 1990s, based on the mathematical theory of optimization. For many problems, it is possible to begin the search with some form of a guess and then refine the guess incrementally until no more refinements can be made. These algorithms can be visualized as blind hill climbing: we begin the search at a random point on the landscape, and then, by jumps or steps, we keep moving our guess uphill, until we reach the top. Other optimization algorithms are simulated annealing, beam search and random optimization. Evolutionary computation uses a form of optimization search. For example, they may begin with a population of organisms (the guesses) and then allow them to mutate and recombine, selecting only the fittest to survive each generation (refining the guesses). Classic evolutionary algorithms include genetic algorithms, gene expression programming, and genetic programming. Alternatively, distributed search processes can coordinate via swarm intelligence algorithms. Two popular swarm algorithms used in search are particle swarm optimization (inspired by bird flocking) and ant colony optimization (inspired by ant trails). Logic Logic is used for knowledge representation and problem solving, but it can be applied to other problems as well. For example, the satplan algorithm uses logic for planning and inductive logic programming is a method for learning. Several different forms of logic are used in AI research. Propositional logic involves truth functions such as "or" and "not". First-order logic adds quantifiers and predicates, and can express facts about objects, their properties, and their relations with each other. Fuzzy logic assigns a "degree of truth" (between 0 and 1) to vague statements such as "Alice is old" (or rich, or tall, or hungry), that are too linguistically imprecise to be completely true or false. Default logics, non-monotonic logics and circumscription are forms of logic designed to help with default reasoning and the qualification problem. Several extensions of logic have been designed to handle specific domains of knowledge, such as: description logics; situation calculus, event calculus and fluent calculus (for representing events and time); causal calculus; belief calculus (belief revision); and modal logics. Logics to model contradictory or inconsistent statements arising in multi-agent systems have also been designed, such as paraconsistent logics. Probabilistic methods for uncertain reasoning Many problems in AI (in reasoning, planning, learning, perception, and robotics) require the agent to operate with incomplete or uncertain information. AI researchers have devised a number of powerful tools to solve these problems using methods from probability theory and economics. Bayesian networks are a very general tool that can be used for various problems: reasoning (using the Bayesian inference algorithm), learning (using the expectation-maximization algorithm), planning (using decision networks) and perception (using dynamic Bayesian networks). Probabilistic algorithms can also be used for filtering, prediction, smoothing and finding explanations for streams of data, helping perception systems to analyze processes that occur over time (e.g., hidden Markov models or Kalman filters). A key concept from the science of economics is "utility": a measure of how valuable something is to an intelligent agent. Precise mathematical tools have been developed that analyze how an agent can make choices and plan, using decision theory, decision analysis, and information value theory. These tools include models such as Markov decision processes, dynamic decision networks, game theory and mechanism design. Classifiers and statistical learning methods The simplest AI applications can be divided into two types: classifiers ("if shiny then diamond") and controllers ("if diamond then pick up"). Controllers do, however, also classify conditions before inferring actions, and therefore classification forms a central part of many AI systems. Classifiers are functions that use pattern matching to determine a closest match. They can be tuned according to examples, making them very attractive for use in AI. These examples are known as observations or patterns. In supervised learning, each pattern belongs to a certain predefined class. A class is a decision that has to be made. All the observations combined with their class labels are known as a data set. When a new observation is received, that observation is classified based on previous experience. A classifier can be trained in various ways; there are many statistical and machine learning approaches. The decision tree is the simplest and most widely used symbolic machine learning algorithm. K-nearest neighbor algorithm was the most widely used analogical AI until the mid-1990s. Kernel methods such as the support vector machine (SVM) displaced k-nearest neighbor in the 1990s. The naive Bayes classifier is reportedly the "most widely used learner" at Google, due in part to its scalability. Neural networks are also used for classification. Classifier performance depends greatly on the characteristics of the data to be classified, such as the dataset size, distribution of samples across classes, the dimensionality, and the level of noise. Model-based classifiers perform well if the assumed model is an extremely good fit for the actual data. Otherwise, if no matching model is available, and if accuracy (rather than speed or scalability) is the sole concern, conventional wisdom is that discriminative classifiers (especially SVM) tend to be more accurate than model-based classifiers such as "naive Bayes" on most practical data sets. Artificial neural networks Neural networks were inspired by the architecture of neurons in the human brain. A simple "neuron" N accepts input from other neurons, each of which, when activated (or "fired"), casts a weighted "vote" for or against whether neuron N should itself activate. Learning requires an algorithm to adjust these weights based on the training data; one simple algorithm (dubbed "fire together, wire together") is to increase the weight between two connected neurons when the activation of one triggers the successful activation of another. Neurons have a continuous spectrum of activation; in addition, neurons can process inputs in a nonlinear way rather than weighing straightforward votes. Modern neural networks model complex relationships between inputs and outputs or and find patterns in data. They can learn continuous functions and even digital logical operations. Neural networks can be viewed a type of mathematical optimization — they perform a gradient descent on a multi-dimensional topology that was created by training the network. The most common training technique is the backpropagation algorithm. Other learning techniques for neural networks are Hebbian learning ("fire together, wire together"), GMDH or competitive learning. The main categories of networks are acyclic or feedforward neural networks (where the signal passes in only one direction) and recurrent neural networks (which allow feedback and short-term memories of previous input events). Among the most popular feedforward networks are perceptrons, multi-layer perceptrons and radial basis networks. Deep learning Deep learning uses several layers of neurons between the network's inputs and outputs. The multiple layers can progressively extract higher-level features from the raw input. For example, in image processing, lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits or letters or faces. Deep learning has drastically improved the performance of programs in many important subfields of artificial intelligence, including computer vision, speech recognition, image classification and others. Deep learning often uses convolutional neural networks for many or all of its layers. In a convolutional layer, each neuron receives input from only a restricted area of the previous layer called the neuron's receptive field. This can substantially reduce the number of weighted connections between neurons, and creates a hierarchy similar to the organization of the animal visual cortex. In a recurrent neural network the signal will propagate through a layer more than once; thus, an RNN is an example of deep learning. RNNs can be trained by gradient descent, however long-term gradients which are back-propagated can "vanish" (that is, they can tend to zero) or "explode" (that is, they can tend to infinity), known as the vanishing gradient problem. The long short term memory (LSTM) technique can prevent this in most cases. Specialized languages and hardware Specialized languages for artificial intelligence have been developed, such as Lisp, Prolog, TensorFlow and many others. Hardware developed for AI includes AI accelerators and neuromorphic computing. Applications AI is relevant to any intellectual task. Modern artificial intelligence techniques are pervasive and are too numerous to list here. Frequently, when a technique reaches mainstream use, it is no longer considered artificial intelligence; this phenomenon is described as the AI effect. In the 2010s, AI applications were at the heart of the most commercially successful areas of computing, and have become a ubiquitous feature of daily life. AI is used in search engines (such as Google Search), targeting online advertisements, recommendation systems (offered by Netflix, YouTube or Amazon), driving internet traffic, targeted advertising (AdSense, Facebook), virtual assistants (such as Siri or Alexa), autonomous vehicles (including drones and self-driving cars), automatic language translation (Microsoft Translator, Google Translate), facial recognition (Apple's Face ID or Microsoft's DeepFace), image labeling (used by Facebook, Apple's iPhoto and TikTok) and spam filtering. There are also thousands of successful AI applications used to solve problems for specific industries or institutions. A few examples are: energy storage, deepfakes, medical diagnosis, military logistics, or supply chain management. Game playing has been a test of AI's strength since the 1950s. Deep Blue became the first computer chess-playing system to beat a reigning world chess champion, Garry Kasparov, on 11 May 1997. In 2011, in a Jeopardy! quiz show exhibition match, IBM's question answering system, Watson, defeated the two greatest Jeopardy! champions, Brad Rutter and Ken Jennings, by a significant margin. In March 2016, AlphaGo won 4 out of 5 games of Go in a match with Go champion Lee Sedol, becoming the first computer Go-playing system to beat a professional Go player without handicaps. Other programs handle imperfect-information games; such as for poker at a superhuman level, Pluribus and Cepheus. DeepMind in the 2010s developed a "generalized artificial intelligence" that could learn many diverse Atari games on its own. By 2020, Natural Language Processing systems such as the enormous GPT-3 (then by far the largest artificial neural network) were matching human performance on pre-existing benchmarks, albeit without the system attaining commonsense understanding of the contents of the benchmarks. DeepMind's AlphaFold 2 (2020) demonstrated the ability to approximate, in hours rather than months, the 3D structure of a protein. Other applications predict the result of judicial decisions, create art (such as poetry or painting) and prove mathematical theorems. Philosophy Defining artificial intelligence Thinking vs. acting: the Turing test Alan Turing wrote in 1950 "I propose to consider the question 'can machines think'?" He advised changing the question from whether a machine "thinks", to "whether or not it is possible for machinery to show intelligent behaviour". The only thing visible is the behavior of the machine, so it does not matter if the machine is conscious, or has a mind, or whether the intelligence is merely a "simulation" and not "the real thing". He noted that we also don't know these things about other people, but that we extend a "polite convention" that they are actually "thinking". This idea forms the basis of the Turing test. Acting humanly vs. acting intelligently: intelligent agents AI founder John McCarthy said: "Artificial intelligence is not, by definition, simulation of human intelligence". Russell and Norvig agree and criticize the Turing test. They wrote: "Aeronautical engineering texts do not define the goal of their field as 'making machines that fly so exactly like pigeons that they can fool other pigeons. Other researchers and analysts disagree and have argued that AI should simulate natural intelligence by studying psychology or neurobiology. The intelligent agent paradigm defines intelligent behavior in general, without reference to human beings. An intelligent agent is a system that perceives its environment and takes actions that maximize its chances of success. Any system that has goal-directed behavior can be analyzed as an intelligent agent: something as simple as a thermostat, as complex as a human being, as well as large systems such as firms, biomes or nations. The intelligent agent paradigm became widely accepted during the 1990s, and currently serves as the definition of the field. The paradigm has other advantages for AI. It provides a reliable and scientific way to test programs; researchers can directly compare or even combine different approaches to isolated problems, by asking which agent is best at maximizing a given "goal function". It also gives them a common language to communicate with other fields — such as mathematical optimization (which is defined in terms of "goals") or economics (which uses the same definition of a "rational agent"). Evaluating approaches to AI No established unifying theory or paradigm has guided AI research for most of its history. The unprecedented success of statistical machine learning in the 2010s eclipsed all other approaches (so much so that some sources, especially in the business world, use the term "artificial intelligence" to mean "machine learning with neural networks"). This approach is mostly sub-symbolic, neat, soft and narrow (see below). Critics argue that these questions may have to be revisited by future generations of AI researchers. Symbolic AI and its limits Symbolic AI (or "GOFAI") simulated the high-level conscious reasoning that people use when they solve puzzles, express legal reasoning and do mathematics. They were highly successful at "intelligent" tasks such as algebra or IQ tests. In the 1960s, Newell and Simon proposed the physical symbol systems hypothesis: "A physical symbol system has the necessary and sufficient means of general intelligent action." However, the symbolic approach failed dismally on many tasks that humans solve easily, such as learning, recognizing an object or commonsense reasoning. Moravec's paradox is the discovery that high-level "intelligent" tasks were easy for AI, but low level "instinctive" tasks were extremely difficult. Philosopher Hubert Dreyfus had argued since the 1960s that human expertise depends on unconscious instinct rather than conscious symbol manipulation, and on having a "feel" for the situation, rather than explicit symbolic knowledge. Although his arguments had been ridiculed and ignored when they were first presented, eventually AI research came to agree. The issue is not resolved: sub-symbolic reasoning can make many of the same inscrutable mistakes that human intuition does, such as algorithmic bias. Critics such Noam Chomsky argue continuing research into symbolic AI will still be necessary to attain general intelligence, in part because sub-symbolic AI is a move away from explainable AI: it can be difficult or impossible to understand why a modern statistical AI program made a particular decision. Neat vs. scruffy "Neats" hope that intelligent behavior be described using simple, elegant principles (such as logic, optimization, or neural networks). "Scruffies" expect that it necessarily requires solving a large number of unrelated problems. This issue was actively discussed in the 70s and 80s, but in the 1990s mathematical methods and solid scientific standards became the norm, a transition that Russell and Norvig termed "the victory of the neats". Soft vs. hard computing Finding a provably correct or optimal solution is intractable for many important problems. Soft computing is a set of techniques, including genetic algorithms, fuzzy logic and neural networks, that are tolerant of imprecision, uncertainty, partial truth and approximation. Soft computing was introduced in the late 80s and most successful AI programs in the 21st century are examples of soft computing with neural networks. Narrow vs. general AI AI researchers are divided as to whether to pursue the goals of artificial general intelligence and superintelligence (general AI) directly, or to solve as many specific problems as possible (narrow AI) in hopes these solutions will lead indirectly to the field's long-term goals General intelligence is difficult to define and difficult to measure, and modern AI has had more verifiable successes by focussing on specific problems with specific solutions. The experimental sub-field of artificial general intelligence studies this area exclusively. Machine consciousness, sentience and mind The philosophy of mind does not know whether a machine can have a mind, consciousness and mental states, in the same sense that human beings do. This issue considers the internal experiences of the machine, rather than its external behavior. Mainstream AI research considers this issue irrelevant, because it does not effect the goals of the field. Stuart Russell and Peter Norvig observe that most AI researchers "don't care about the [philosophy of AI] — as long as the program works, they don't care whether you call it a simulation of intelligence or real intelligence." However, the question has become central to the philosophy of mind. It is also typically the central question at issue in artificial intelligence in fiction. Consciousness David Chalmers identified two problems in understanding the mind, which he named the "hard" and "easy" problems of consciousness. The easy problem is understanding how the brain processes signals, makes plans and controls behavior. The hard problem is explaining how this feels or why it should feel like anything at all. Human information processing is easy to explain, however human subjective experience is difficult to explain. For example, it is easy to imagine a color blind person who has learned to identify which objects in their field of view are red, but it is not clear what would be required for the person to know what red looks like. Computationalism and functionalism Computationalism is the position in the philosophy of mind that the human mind is an information processing system and that thinking is a form of computing. Computationalism argues that the relationship between mind and body is similar or identical to the relationship between software and hardware and thus may be a solution to the mind-body problem. This philosophical position was inspired by the work of AI researchers and cognitive scientists in the 1960s and was originally proposed by philosophers Jerry Fodor and Hilary Putnam. Philosopher John Searle characterized this position as "strong AI": "The appropriately programmed computer with the right inputs and outputs would thereby have a mind in exactly the same sense human beings have minds." Searle counters this assertion with his Chinese room argument, which attempts to show that, even if a machine perfectly simulates human behavior, there is still no reason to suppose it also has a mind. Robot rights If a machine has a mind and subjective experience, then it may also have sentience (the ability to feel), and if so, then it could also suffer, and thus it would be entitled to certain rights. Any hypothetical robot rights would lie on a spectrum with animal rights and human rights. This issue has been considered in fiction for centuries, and is now being considered by, for example, California's Institute for the Future, however critics argue that the discussion is premature. Future Superintelligence A superintelligence, hyperintelligence, or superhuman intelligence, is a hypothetical agent that would possess intelligence far surpassing that of the brightest and most gifted human mind. Superintelligence may also refer to the form or degree of intelligence possessed by such an agent. If research into artificial general intelligence produced sufficiently intelligent software, it might be able to reprogram and improve itself. The improved software would be even better at improving itself, leading to recursive self-improvement. Its intelligence would increase exponentially in an intelligence explosion and could dramatically surpass humans. Science fiction writer Vernor Vinge named this scenario the "singularity". Because it is difficult or impossible to know the limits of intelligence or the capabilities of superintelligent machines, the technological singularity is an occurrence beyond which events are unpredictable or even unfathomable. Robot designer Hans Moravec, cyberneticist Kevin Warwick, and inventor Ray Kurzweil have predicted that humans and machines will merge in the future into cyborgs that are more capable and powerful than either. This idea, called transhumanism, has roots in Aldous Huxley and Robert Ettinger. Edward Fredkin argues that "artificial intelligence is the next stage in evolution", an idea first proposed by Samuel Butler's "Darwin among the Machines" as far back as 1863, and expanded upon by George Dyson in his book of the same name in 1998. Risks Technological unemployment In the past technology has tended to increase rather than reduce total employment, but economists acknowledge that "we're in uncharted territory" with AI. A survey of economists showed disagreement about whether the increasing use of robots and AI will cause a substantial increase in long-term unemployment, but they generally agree that it could be a net benefit, if productivity gains are redistributed. Subjective estimates of the risk vary widely; for example, Michael Osborne and Carl Benedikt Frey estimate 47% of U.S. jobs are at "high risk" of potential automation, while an OECD report classifies only 9% of U.S. jobs as "high risk". Unlike previous waves of automation, many middle-class jobs may be eliminated by artificial intelligence; The Economist states that "the worry that AI could do to white-collar jobs what steam power did to blue-collar ones during the Industrial Revolution" is "worth taking seriously". Jobs at extreme risk range from paralegals to fast food cooks, while job demand is likely to increase for care-related professions ranging from personal healthcare to the clergy. Bad actors and weaponized AI AI provides a number of tools that are particularly useful for authoritarian governments: smart spyware, face recognition and voice recognition allow widespread surveillance; such surveillance allows machine learning to classify potential enemies of the state and can prevent them from hiding; recommendation systems can precisely target propaganda and misinformation for maximum effect; deepfakes aid in producing misinformation; advanced AI can make centralized decision making more competitive with liberal and decentralized systems such as markets. Terrorists, criminals and rogue states may use other forms of weaponized AI such as advanced digital warfare and lethal autonomous weapons. By 2015, over fifty countries were reported to be researching battlefield robots. Algorithmic bias AI programs can become biased after learning from real world data. It is not typically introduced by the system designers, but is learned by the program, and thus the programmers are often unaware that the bias exists. Bias can be inadvertently introduced by the way training data is selected. It can also emerge from correlations: AI is used to classify individuals into groups and then make predictions assuming that the individual will resemble other members of the group. In some cases, this assumption may be unfair. An example of this is COMPAS, a commercial program widely used by U.S. courts to assess the likelihood of a defendant becoming a recidivist. ProPublica claims that the COMPAS-assigned recidivism risk level of black defendants is far more likely to be an overestimate than that of white defendants, despite the fact that the program was not told the races of the defendants. Other examples where algorithmic bias can lead to unfair outcomes are when AI is used for credit rating or hiring. Existential risk Superintelligent AI may be able to improve itself to the point that humans could not control it. This could, as physicist Stephen Hawking puts it, "spell the end of the human race". Philosopher Nick Bostrom argues that sufficiently intelligent AI, if it chooses actions based on achieving some goal, will exhibit convergent behavior such as acquiring resources or protecting itself from being shut down. If this AI's goals do not fully reflect humanity's, it might need to harm humanity to acquire more resources or prevent itself from being shut down, ultimately to better achieve its goal. He concludes that AI poses a risk to mankind, however humble or "friendly" its stated goals might be. Political scientist Charles T. Rubin argues that "any sufficiently advanced benevolence may be indistinguishable from malevolence." Humans should not assume machines or robots would treat us favorably because there is no a priori reason to believe that they would share our system of morality. The opinion of experts and industry insiders is mixed, with sizable fractions both concerned and unconcerned by risk from eventual superhumanly-capable AI. Stephen Hawking, Microsoft founder Bill Gates, history professor Yuval Noah Harari, and SpaceX founder Elon Musk have all expressed serious misgivings about the future of AI. Prominent tech titans including Peter Thiel (Amazon Web Services) and Musk have committed more than $1 billion to nonprofit companies that champion responsible AI development, such as OpenAI and the Future of Life Institute. Mark Zuckerberg (CEO, Facebook) has said that artificial intelligence is helpful in its current form and will continue to assist humans. Other experts argue is that the risks are far enough in the future to not be worth researching, or that humans will be valuable from the perspective of a superintelligent machine. Rodney Brooks, in particular, has said that "malevolent" AI is still centuries away. Ethical machines Friendly AI are machines that have been designed from the beginning to minimize risks and to make choices that benefit humans. Eliezer Yudkowsky, who coined the term, argues that developing friendly AI should be a higher research priority: it may require a large investment and it must be completed before AI becomes an existential risk. Machines with intelligence have the potential to use their intelligence to make ethical decisions. The field of machine ethics provides machines with ethical principles and procedures for resolving ethical dilemmas. Machine ethics is also called machine morality, computational ethics or computational morality, and was founded at an AAAI symposium in 2005. Others approaches include Wendell Wallach's "artificial moral agents" and Stuart J. Russell's three principles for developing provably beneficial machines. Human-Centered AI Human-Centered Artificial Intelligence (HCAI) is a set of processes for designing applications that are reliable, safe, and trustworthy. These extend the processes of user experience design such as user observation and interviews. Further processes include discussions with stakeholders, usability testing, iterative refinement and continuing evaluation in use of systems that employ AI and machine learning algorithms. Human-Centered AI manifests in products that are designed to amplify, augment, empower and enhance human performance. These products ensure high levels of human control and high levels of automation. HCAI research includes governance structures that include safety cultures within organizations and independent oversight by experienced groups that review plans for new projects, continuous evaluation of usage, and retrospective analysis of failures. The rise of HCAI is visible in topics such as explainable AI, transparency, audit trail, fairness, trustworthiness, and controllable systems. Regulation The regulation of artificial intelligence is the development of public sector policies and laws for promoting and regulating artificial intelligence (AI); it is therefore related to the broader regulation of algorithms. The regulatory and policy landscape for AI is an emerging issue in jurisdictions globally. Between 2016 and 2020, more than 30 countries adopted dedicated strategies for AI. Most EU member states had released national AI strategies, as had Canada, China, India, Japan, Mauritius, the Russian Federation, Saudi Arabia, United Arab Emirates, USA and Vietnam. Others were in the process of elaborating their own AI strategy, including Bangladesh, Malaysia and Tunisia. The Global Partnership on Artificial Intelligence was launched in June 2020, stating a need for AI to be developed in accordance with human rights and democratic values, to ensure public confidence and trust in the technology. Henry Kissinger, Eric Schmidt, and Daniel Huttenlocher published an joint statement in November 2021 calling for a government commission to regulate AI. In fiction Thought-capable artificial beings have appeared as storytelling devices since antiquity, and have been a persistent theme in science fiction. A common trope in these works began with Mary Shelley's Frankenstein, where a human creation becomes a threat to its masters. This includes such works as Arthur C. Clarke's and Stanley Kubrick's 2001: A Space Odyssey (both 1968), with HAL 9000, the murderous computer in charge of the Discovery One spaceship, as well as The Terminator (1984) and The Matrix (1999). In contrast, the rare loyal robots such as Gort from The Day the Earth Stood Still (1951) and Bishop from Aliens (1986) are less prominent in popular culture. Isaac Asimov introduced the Three Laws of Robotics in many books and stories, most notably the "Multivac" series about a super-intelligent computer of the same name. Asimov's laws are often brought up during lay discussions of machine ethics; while almost all artificial intelligence researchers are familiar with Asimov's laws through popular culture, they generally consider the laws useless for many reasons, one of which is their ambiguity. Transhumanism (the merging of humans and machines) is explored in the manga Ghost in the Shell and the science-fiction series Dune. Several works use AI to force us to confront the fundamental question of what makes us human, showing us artificial beings that have the ability to feel, and thus to suffer. This appears in Karel Čapek's R.U.R., the films A.I. Artificial Intelligence and Ex Machina, as well as the novel Do Androids Dream of Electric Sheep?, by Philip K. Dick. Dick considers the idea that our understanding of human subjectivity is altered by technology created with artificial intelligence. See also A.I. Rising AI control problem Artificial intelligence arms race Artificial general intelligence Behavior selection algorithm Business process automation Case-based reasoning Citizen Science Emergent algorithm Female gendering of AI technologies Glossary of artificial intelligence Robotic process automation Synthetic intelligence Universal basic income Weak AI Explanatory notes Citations References AI textbooks These were the four the most widely used AI textbooks in 2008. . Later editions. . The two most widely used textbooks in 2021. History of AI . . Other sources was introduced by Kunihiko Fukushima in 1980. | . Presidential Address to the Association for the Advancement of Artificial Intelligence. Later published as . Further reading DH Author, "Why Are There Still So Many Jobs? The History and Future of Workplace Automation" (2015) 29(3) Journal of Economic Perspectives 3. Boden, Margaret, Mind As Machine, Oxford University Press, 2006. Cukier, Kenneth, "Ready for Robots? How to Think about the Future of AI", Foreign Affairs, vol. 98, no. 4 (July/August 2019), pp. 192–98. George Dyson, historian of computing, writes (in what might be called "Dyson's Law") that "Any system simple enough to be understandable will not be complicated enough to behave intelligently, while any system complicated enough to behave intelligently will be too complicated to understand." (p. 197.) Computer scientist Alex Pentland writes: "Current AI machine-learning algorithms are, at their core, dead simple stupid. They work, but they work by brute force." (p. 198.) Domingos, Pedro, "Our Digital Doubles: AI will serve our species, not control it", Scientific American, vol. 319, no. 3 (September 2018), pp. 88–93. Gopnik, Alison, "Making AI More Human: Artificial intelligence has staged a revival by starting to incorporate what we know about how children learn", Scientific American, vol. 316, no. 6 (June 2017), pp. 60–65. Halpern, Sue, "The Human Costs of AI" (review of Kate Crawford, Atlas of AI: Power, Politics, and the Planetary Costs of Artificial Intelligence, Yale University Press, 2021, 327 pp.; Simon Chesterman, We, the Robots?: Regulating Artificial Intelligence and the Limits of the Law, Cambridge University Press, 2021, 289 pp.; Keven Roose, Futureproof: 9 Rules for Humans in the Age of Automation, Random House, 217 pp.; Erik J. Larson, The Myth of Artificial Intelligence: Why Computers Can't Think the Way We Do, Belknap Press / Harvard University Press, 312 pp.), The New York Review of Books, vol. LXVIII, no. 16 (21 October 2021), pp. 29–31. "AI training models can replicate entrenched social and cultural biases. [...] Machines only know what they know from the data they have been given. [p. 30.] [A]rtificial general intelligence–machine-based intelligence that matches our own–is beyond the capacity of algorithmic machine learning... 'Your brain is one piece in a broader system which includes your body, your environment, other humans, and culture as a whole.' [E]ven machines that master the tasks they are trained to perform can't jump domains. AIVA, for example, can't drive a car even though it can write music (and wouldn't even be able to do that without Bach and Beethoven [and other composers on which AIVA is trained])." (p. 31.) Johnston, John (2008) The Allure of Machinic Life: Cybernetics, Artificial Life, and the New AI, MIT Press. Koch, Christof, "Proust among the Machines", Scientific American, vol. 321, no. 6 (December 2019), pp. 46–49. Christof Koch doubts the possibility of "intelligent" machines attaining consciousness, because "[e]ven the most sophisticated brain simulations are unlikely to produce conscious feelings." (p. 48.) According to Koch, "Whether machines can become sentient [is important] for ethical reasons. If computers experience life through their own senses, they cease to be purely a means to an end determined by their usefulness to... humans. Per GNW [the Global Neuronal Workspace theory], they turn from mere objects into subjects... with a point of view.... Once computers' cognitive abilities rival those of humanity, their impulse to push for legal and political rights will become irresistible—the right not to be deleted, not to have their memories wiped clean, not to suffer pain and degradation. The alternative, embodied by IIT [Integrated Information Theory], is that computers will remain only supersophisticated machinery, ghostlike empty shells, devoid of what we value most: the feeling of life itself." (p. 49.) Marcus, Gary, "Am I Human?: Researchers need new ways to distinguish artificial intelligence from the natural kind", Scientific American, vol. 316, no. 3 (March 2017), pp. 58–63. A stumbling block to AI has been an incapacity for reliable disambiguation. An example is the "pronoun disambiguation problem": a machine has no way of determining to whom or what a pronoun in a sentence refers. (p. 61.) E McGaughey, 'Will Robots Automate Your Job Away? Full Employment, Basic Income, and Economic Democracy' (2018) SSRN, part 2(3) . George Musser, "Artificial Imagination: How machines could learn creativity and common sense, among other human qualities", Scientific American, vol. 320, no. 5 (May 2019), pp. 58–63. Myers, Courtney Boyd ed. (2009). "The AI Report" . Forbes June 2009 Scharre, Paul, "Killer Apps: The Real Dangers of an AI Arms Race", Foreign Affairs, vol. 98, no. 3 (May/June 2019), pp. 135–44. "Today's AI technologies are powerful but unreliable. Rules-based systems cannot deal with circumstances their programmers did not anticipate. Learning systems are limited by the data on which they were trained. AI failures have already led to tragedy. Advanced autopilot features in cars, although they perform well in some circumstances, have driven cars without warning into trucks, concrete barriers, and parked cars. In the wrong situation, AI systems go from supersmart to superdumb in an instant. When an enemy is trying to manipulate and hack an AI system, the risks are even greater." (p. 140.) Sun, R. & Bookman, L. (eds.), Computational Architectures: Integrating Neural and Symbolic Processes. Kluwer Academic Publishers, Needham, MA. 1994. Taylor, Paul, "Insanely Complicated, Hopelessly Inadequate" (review of Brian Cantwell Smith, The Promise of Artificial Intelligence: Reckoning and Judgment, MIT, 2019, , 157 pp.; Gary Marcus and Ernest Davis, Rebooting AI: Building Artificial Intelligence We Can Trust, Ballantine, 2019, , 304 pp.; Judea Pearl and Dana Mackenzie, The Book of Why: The New Science of Cause and Effect, Penguin, 2019, , 418 pp.), London Review of Books, vol. 43, no. 2 (21 January 2021), pp. 37–39. Paul Taylor writes (p. 39): "Perhaps there is a limit to what a computer can do without knowing that it is manipulating imperfect representations of an external reality." Tooze, Adam, "Democracy and Its Discontents", The New York Review of Books, vol. LXVI, no. 10 (6 June 2019), pp. 52–53, 56–57. "Democracy has no clear answer for the mindless operation of bureaucratic and technological power. We may indeed be witnessing its extension in the form of artificial intelligence and robotics. Likewise, after decades of dire warning, the environmental problem remains fundamentally unaddressed.... Bureaucratic overreach and environmental catastrophe are precisely the kinds of slow-moving existential challenges that democracies deal with very badly.... Finally, there is the threat du jour: corporations and the technologies they promote." (pp. 56–57.) External links Artificial Intelligence. BBC Radio 4 discussion with John Agar, Alison Adam & Igor Aleksander (In Our Time, Dec. 8, 2005). Sources Cybernetics Formal sciences Computational neuroscience Emerging technologies Unsolved problems in computer science Computational fields of study

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1168

https://en.wikipedia.org/wiki/Anaximander

Anaximander

Anaximander (; Anaximandros; ) was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia (in modern-day Turkey). He belonged to the Milesian school and learned the teachings of his master Thales. He succeeded Thales and became the second master of that school where he counted Anaximenes and, arguably, Pythagoras amongst his pupils. Little of his life and work is known today. According to available historical documents, he is the first philosopher known to have written down his studies, although only one fragment of his work remains. Fragmentary testimonies found in documents after his death provide a portrait of the man. Anaximander was an early proponent of science and tried to observe and explain different aspects of the universe, with a particular interest in its origins, claiming that nature is ruled by laws, just like human societies, and anything that disturbs the balance of nature does not last long. Like many thinkers of his time, Anaximander's philosophy included contributions to many disciplines. In astronomy, he attempted to describe the mechanics of celestial bodies in relation to the Earth. In physics, his postulation that the indefinite (or apeiron) was the source of all things led Greek philosophy to a new level of conceptual abstraction. His knowledge of geometry allowed him to introduce the gnomon in Greece. He created a map of the world that contributed greatly to the advancement of geography. He was also involved in the politics of Miletus and was sent as a leader to one of its colonies. Biography Anaximander, son of Praxiades, was born in the third year of the 42nd Olympiad (610 BC). According to Apollodorus of Athens, Greek grammarian of the 2nd century BC, he was sixty-four years old during the second year of the 58th Olympiad (547–546 BC), and died shortly afterwards. Establishing a timeline of his work is now impossible, since no document provides chronological references. Themistius, a 4th-century Byzantine rhetorician, mentions that he was the "first of the known Greeks to publish a written document on nature." Therefore, his texts would be amongst the earliest written in prose, at least in the Western world. By the time of Plato, his philosophy was almost forgotten, and Aristotle, his successor Theophrastus and a few doxographers provide us with the little information that remains. However, we know from Aristotle that Thales, also from Miletus, precedes Anaximander. It is debatable whether Thales actually was the teacher of Anaximander, but there is no doubt that Anaximander was influenced by Thales' theory that everything is derived from water. One thing that is not debatable is that even the ancient Greeks considered Anaximander to be from the Monist school which began in Miletus, with Thales followed by Anaximander and which ended with Anaximenes. 3rd-century Roman rhetorician Aelian depicts Anaximander as leader of the Milesian colony to Apollonia on the Black Sea coast, and hence some have inferred that he was a prominent citizen. Indeed, Various History (III, 17) explains that philosophers sometimes also dealt with political matters. It is very likely that leaders of Miletus sent him there as a legislator to create a constitution or simply to maintain the colony's allegiance. Anaximander lived the final few years of his life as a subject of the Persian Achaemenid Empire. Theories Anaximander's theories were influenced by the Greek mythical tradition, and by some ideas of Thales – the father of Western philosophy – as well as by observations made by older civilizations in the Near East, especially Babylon. All these were developed rationally. In his desire to find some universal principle, he assumed, like traditional religion, the existence of a cosmic order; and his ideas on this used the old language of myths which ascribed divine control to various spheres of reality. This was a common practice for the Greek philosophers in a society which saw gods everywhere, and therefore could fit their ideas into a tolerably elastic system. Some scholars see a gap between the existing mythical and the new rational way of thought which is the main characteristic of the archaic period (8th to 6th century BC) in the Greek city-states. This has given rise to the phrase "Greek miracle". But if we follow carefully the course of Anaximander's ideas, we will notice that there was not such an abrupt break as initially appears. The basic elements of nature (water, air, fire, earth) which the first Greek philosophers believed made up the universe in fact represent the primordial forces imagined in earlier ways of thinking. Their collision produced what the mythical tradition had called cosmic harmony. In the old cosmogonies – Hesiod (8th – 7th century BC) and Pherecydes (6th century BC) – Zeus establishes his order in the world by destroying the powers which were threatening this harmony (the Titans). Anaximander claimed that the cosmic order is not monarchic but geometric, and that this causes the equilibrium of the earth, which is lying in the centre of the universe. This is the projection on nature of a new political order and a new space organized around a centre which is the static point of the system in the society as in nature. In this space there is isonomy (equal rights) and all the forces are symmetrical and transferable. The decisions are now taken by the assembly of demos in the agora which is lying in the middle of the city. The same rational way of thought led him to introduce the abstract apeiron (indefinite, infinite, boundless, unlimited) as an origin of the universe, a concept that is probably influenced by the original Chaos (gaping void, abyss, formless state) from which everything else appeared in the mythical Greek cosmogony. It also takes notice of the mutual changes between the four elements. Origin, then, must be something else unlimited in its source, that could create without experiencing decay, so that genesis would never stop. Apeiron The Refutation attributed to Hippolytus of Rome (I, 5), and the later 6th century Byzantine philosopher Simplicius of Cilicia, attribute to Anaximander the earliest use of the word apeiron ( "infinite" or "limitless") to designate the original principle. He was the first philosopher to employ, in a philosophical context, the term archē (), which until then had meant beginning or origin. "That Anaximander called this something by the name of is the natural interpretation of what Theophrastos says; the current statement that the term was introduced by him appears to be due to a misunderstanding." And "Hippolytos, however, is not an independent authority, and the only question is what Theophrastos wrote." For him, it became no longer a mere point in time, but a source that could perpetually give birth to whatever will be. The indefiniteness is spatial in early usages as in Homer (indefinite sea) and as in Xenophanes (6th century BC) who said that the earth went down indefinitely (to apeiron) i.e. beyond the imagination or concept of men. Burnet (1930) in Early Greek Philosophy says: "Nearly all we know of Anaximander’s system is derived in the last resort from Theophrastos, who certainly knew his book. He seems once at least to have quoted Anaximander's own words, and he criticised his style. Here are the remains of what he said of him in the First Book: "Anaximander of Miletos, son of Praxiades, a fellow-citizen and associate of Thales, said that the material cause and first element of things was the Infinite, he being the first to introduce this name of the material cause. He says it is neither water nor any other of the so-called elements, but a substance different from them which is infinite" [apeiron, or ] "from which arise all the heavens and the worlds within them.—Phys, Op. fr. 2 (Dox. p. 476 ; R. P. 16)." Burnet's quote from the "First Book" is his translation of Theophrastos' Physic Opinion fragment 2 as it appears in p. 476 of Historia Philosophiae Graecae (1898) by Ritter and Preller and section 16 of Doxographi Graeci (1879) by Diels. By ascribing the "Infinite" with a "material cause", Theophrastos is following the Aristotelian tradition of "nearly always discussing the facts from the point of view of his own system". Aristotle writes (Metaphysics, I.III 3–4) that the Pre-Socratics were searching for the element that constitutes all things. While each pre-Socratic philosopher gave a different answer as to the identity of this element (water for Thales and air for Anaximenes), Anaximander understood the beginning or first principle to be an endless, unlimited primordial mass (apeiron), subject to neither old age nor decay, that perpetually yielded fresh materials from which everything we perceive is derived. He proposed the theory of the apeiron in direct response to the earlier theory of his teacher, Thales, who had claimed that the primary substance was water. The notion of temporal infinity was familiar to the Greek mind from remote antiquity in the religious concept of immortality, and Anaximander's description was in terms appropriate to this conception. This archē is called "eternal and ageless". (Hippolytus (?), Refutation, I,6,I;DK B2)"Aristotle puts things in his own way regardless of historical considerations, and it is difficult to see that it is more of an anachronism to call the Boundless “ intermediate between the elements ” than to say that it is " distinct from the elements.” Indeed, if once we introduce the elements at all, the former description is the more adequate of the two. At any rate, if we refuse to understand these passages as referring to Anaximander, we shall have to say that Aristotle paid a great deal of attention to some one whose very name has been lost, and who not only agreed with some of Anaximander’s views, but also used some of his most characteristic expressions. We may add that in one or two places Aristotle certainly seems to identify the “ intermediate ” with the something “ distinct from ” the elements.""It is certain that he [Anaximander] cannot have said anything about elements, which no one thought of before Empedokles, and no one could think of before Parmenides. The question has only been mentioned because it has given rise to a lengthy controversy, and because it throws light on the historical value of Aristotle’s statements. From the point of view of his own system, these may be justified; but we shall have to remember in other cases that, when he seems to attribute an idea to some earlier thinker, we are not bound to take what he says in an historical sense."For Anaximander, the principle of things, the constituent of all substances, is nothing determined and not an element such as water in Thales' view. Neither is it something halfway between air and water, or between air and fire, thicker than air and fire, or more subtle than water and earth. Anaximander argues that water cannot embrace all of the opposites found in nature — for example, water can only be wet, never dry — and therefore cannot be the one primary substance; nor could any of the other candidates. He postulated the apeiron as a substance that, although not directly perceptible to us, could explain the opposites he saw around him."If Thales had been right in saying that water was the fundamental reality, it would not be easy to see how anything else could ever have existed. One side of the opposition, the cold and moist, would have had its way unchecked, and the warm and dry would have been driven from the field long ago. We must, then, have something not itself one of the warring opposites, something more primitive, out of which they arise, and into which they once more pass away."Anaximander explains how the four elements of ancient physics (air, earth, water and fire) are formed, and how Earth and terrestrial beings are formed through their interactions. Unlike other Pre-Socratics, he never defines this principle precisely, and it has generally been understood (e.g., by Aristotle and by Saint Augustine) as a sort of primal chaos. According to him, the Universe originates in the separation of opposites in the primordial matter. It embraces the opposites of hot and cold, wet and dry, and directs the movement of things; an entire host of shapes and differences then grow that are found in "all the worlds" (for he believed there were many)."Anaximander taught, then, that there was an eternal. The indestructible something out of which everything arises, and into which everything returns; a boundless stock from which the waste of existence is continually made good, “elements.”. That is only the natural development of the thought we have ascribed to Thales, and there can be no doubt that Anaximander at least formulated it distinctly. Indeed, we can still follow to some extent the reasoning which led him to do so. Thales had regarded water as the most likely thing to be that of which all others are forms; Anaximander appears to have asked how the primary substance could be one of these particular things. His argument seems to be preserved by Aristotle, who has the following passage in his discussion of the Infinite: "Further, there cannot be a single, simple body which is infinite, either, as some hold, one distinct from the elements, which they then derive from it, or without this qualification. For there are some who make this. (i.e. a body distinct from the elements). the infinite, and not air or water, in order that the other things may not be destroyed by their infinity. They are in opposition one to another. air is cold, water moist, and fire hot. and therefore, if any one of them were infinite, the rest would have ceased to be by this time. Accordingly they say that what is infinite is something other than the elements, and from it the elements arise.'⁠—Aristotle Physics. F, 5 204 b 22 (Ritter and Preller (1898) Historia Philosophiae Graecae, section 16 b)."Anaximander maintains that all dying things are returning to the element from which they came (apeiron). The one surviving fragment of Anaximander's writing deals with this matter. Simplicius transmitted it as a quotation, which describes the balanced and mutual changes of the elements: Whence things have their origin, Thence also their destruction happens, According to necessity; For they give to each other justice and recompense For their injustice In conformity with the ordinance of Time. Simplicius mentions that Anaximander said all these "in poetic terms", meaning that he used the old mythical language. The goddess Justice (Dike) keeps the cosmic order. This concept of returning to the element of origin was often revisited afterwards, notably by Aristotle, and by the Greek tragedian Euripides: "what comes from earth must return to earth." Friedrich Nietzsche, in his Philosophy in the Tragic Age of the Greeks, stated that Anaximander viewed "... all coming-to-be as though it were an illegitimate emancipation from eternal being, a wrong for which destruction is the only penance." Physicist Max Born, in commenting upon Werner Heisenberg's arriving at the idea that the elementary particles of quantum mechanics are to be seen as different manifestations, different quantum states, of one and the same “primordial substance,”' proposed that this primordial substance be called apeiron. Cosmology Anaximander's bold use of non-mythological explanatory hypotheses considerably distinguishes him from previous cosmology writers such as Hesiod. It confirms that pre-Socratic philosophers were making an early effort to demystify physical processes. His major contribution to history was writing the oldest prose document about the Universe and the origins of life; for this he is often called the "Father of Cosmology" and founder of astronomy. However, pseudo-Plutarch states that he still viewed celestial bodies as deities. Anaximander was the first to conceive a mechanical model of the world. In his model, the Earth floats very still in the centre of the infinite, not supported by anything. It remains "in the same place because of its indifference", a point of view that Aristotle considered ingenious, but false, in On the Heavens. Its curious shape is that of a cylinder]ref>"A column of stone", Aetius reports in De Fide (III, 7, 1), or "similar to a pillar-shaped stone", pseudo-Plutarch (III, 10).</ref> with a height one-third of its diameter. The flat top forms the inhabited world, which is surrounded by a circular oceanic mass. Anaximander's realization that the Earth floats free without falling and does not need to be resting on something has been indicated by many as the first cosmological revolution and the starting point of scientific thinking. Karl Popper calls this idea "one of the boldest, most revolutionary, and most portentous ideas in the whole history of human thinking." Such a model allowed the concept that celestial bodies could pass under the Earth, opening the way to Greek astronomy. At the origin, after the separation of hot and cold, a ball of flame appeared that surrounded Earth like bark on a tree. This ball broke apart to form the rest of the Universe. It resembled a system of hollow concentric wheels, filled with fire, with the rims pierced by holes like those of a flute. Consequently, the Sun was the fire that one could see through a hole the same size as the Earth on the farthest wheel, and an eclipse corresponded with the occlusion of that hole. The diameter of the solar wheel was twenty-seven times that of the Earth (or twenty-eight, depending on the sources) and the lunar wheel, whose fire was less intense, eighteen (or nineteen) times. Its hole could change shape, thus explaining lunar phases. The stars and the planets, located closer, followed the same model. Anaximander was the first astronomer to consider the Sun as a huge mass, and consequently, to realize how far from Earth it might be, and the first to present a system where the celestial bodies turned at different distances. Furthermore, according to Diogenes Laertius (II, 2), he built a celestial sphere. This invention undoubtedly made him the first to realize the obliquity of the Zodiac as the Roman philosopher Pliny the Elder reports in Natural History (II, 8). It is a little early to use the term ecliptic, but his knowledge and work on astronomy confirm that he must have observed the inclination of the celestial sphere in relation to the plane of the Earth to explain the seasons. The doxographer and theologian Aetius attributes to Pythagoras the exact measurement of the obliquity. Multiple worlds According to Simplicius, Anaximander already speculated on the plurality of worlds, similar to atomists Leucippus and Democritus, and later philosopher Epicurus. These thinkers supposed that worlds appeared and disappeared for a while, and that some were born when others perished. They claimed that this movement was eternal, "for without movement, there can be no generation, no destruction". In addition to Simplicius, Hippolytus reports Anaximander's claim that from the infinite comes the principle of beings, which themselves come from the heavens and the worlds (several doxographers use the plural when this philosopher is referring to the worlds within, which are often infinite in quantity). Cicero writes that he attributes different gods to the countless worlds. This theory places Anaximander close to the Atomists and the Epicureans who, more than a century later, also claimed that an infinity of worlds appeared and disappeared. In the timeline of the Greek history of thought, some thinkers conceptualized a single world (Plato, Aristotle, Anaxagoras and Archelaus), while others instead speculated on the existence of a series of worlds, continuous or non-continuous (Anaximenes, Heraclitus, Empedocles and Diogenes). Meteorological phenomena Anaximander attributed some phenomena, such as thunder and lightning, to the intervention of elements, rather than to divine causes. In his system, thunder results from the shock of clouds hitting each other; the loudness of the sound is proportionate with that of the shock. Thunder without lightning is the result of the wind being too weak to emit any flame, but strong enough to produce a sound. A flash of lightning without thunder is a jolt of the air that disperses and falls, allowing a less active fire to break free. Thunderbolts are the result of a thicker and more violent air flow. He saw the sea as a remnant of the mass of humidity that once surrounded Earth. A part of that mass evaporated under the sun's action, thus causing the winds and even the rotation of the celestial bodies, which he believed were attracted to places where water is more abundant. He explained rain as a product of the humidity pumped up from Earth by the sun. For him, the Earth was slowly drying up and water only remained in the deepest regions, which someday would go dry as well. According to Aristotle's Meteorology (II, 3), Democritus also shared this opinion. Origin of humankind Anaximander speculated about the beginnings and origin of animal life, and that humans came from other animals in waters. According to his evolutionary theory, animals sprang out of the sea long ago, born trapped in a spiny bark, but as they got older, the bark would dry up and animals would be able to break it. As the early humidity evaporated, dry land emerged and, in time, humankind had to adapt. The 3rd century Roman writer Censorinus reports: Anaximander put forward the idea that humans had to spend part of this transition inside the mouths of big fish to protect themselves from the Earth's climate until they could come out in open air and lose their scales. He thought that, considering humans' extended infancy, we could not have survived in the primeval world in the same manner we do presently. Other accomplishments Cartography Both Strabo and Agathemerus (later Greek geographers) claim that, according to the geographer Eratosthenes, Anaximander was the first to publish a map of the world. The map probably inspired the Greek historian Hecataeus of Miletus to draw a more accurate version. Strabo viewed both as the first geographers after Homer. Maps were produced in ancient times, also notably in Egypt, Lydia, the Middle East, and Babylon. Only some small examples survived until today. The unique example of a world map comes from late Babylonian tablet BM 92687 later than 9th century BC but is based probably on a much older map. These maps indicated directions, roads, towns, borders, and geological features. Anaximander's innovation was to represent the entire inhabited land known to the ancient Greeks. Such an accomplishment is more significant than it at first appears. Anaximander most likely drew this map for three reasons. First, it could be used to improve navigation and trade between Miletus's colonies and other colonies around the Mediterranean Sea and Black Sea. Second, Thales would probably have found it easier to convince the Ionian city-states to join in a federation in order to push the Median threat away if he possessed such a tool. Finally, the philosophical idea of a global representation of the world simply for the sake of knowledge was reason enough to design one. Surely aware of the sea's convexity, he may have designed his map on a slightly rounded metal surface. The centre or “navel” of the world ( omphalós gẽs) could have been Delphi, but is more likely in Anaximander's time to have been located near Miletus. The Aegean Sea was near the map's centre and enclosed by three continents, themselves located in the middle of the ocean and isolated like islands by sea and rivers. Europe was bordered on the south by the Mediterranean Sea and was separated from Asia by the Black Sea, the Lake Maeotis, and, further east, either by the Phasis River (now called the Rioni in Georgia) or the Tanais. The Nile flowed south into the ocean, separating Libya (which was the name for the part of the then-known African continent) from Asia. Gnomon The Suda relates that Anaximander explained some basic notions of geometry. It also mentions his interest in the measurement of time and associates him with the introduction in Greece of the gnomon. In Lacedaemon, he participated in the construction, or at least in the adjustment, of sundials to indicate solstices and equinoxes. Indeed, a gnomon required adjustments from a place to another because of the difference in latitude. In his time, the gnomon was simply a vertical pillar or rod mounted on a horizontal plane. The position of its shadow on the plane indicated the time of day. As it moves through its apparent course, the Sun draws a curve with the tip of the projected shadow, which is shortest at noon, when pointing due south. The variation in the tip's position at noon indicates the solar time and the seasons; the shadow is longest on the winter solstice and shortest on the summer solstice. The invention of the gnomon itself cannot be attributed to Anaximander because its use, as well as the division of days into twelve parts, came from the Babylonians. It is they, according to Herodotus' Histories (II, 109), who gave the Greeks the art of time measurement. It is likely that he was not the first to determine the solstices, because no calculation is necessary. On the other hand, equinoxes do not correspond to the middle point between the positions during solstices, as the Babylonians thought. As the Suda seems to suggest, it is very likely that with his knowledge of geometry, he became the first Greek to accurately determine the equinoxes. Prediction of an earthquake In his philosophical work De Divinatione (I, 50, 112), Cicero states that Anaximander convinced the inhabitants of Lacedaemon to abandon their city and spend the night in the country with their weapons because an earthquake was near. The city collapsed when the top of the Taygetus split like the stern of a ship. Pliny the Elder also mentions this anecdote (II, 81), suggesting that it came from an "admirable inspiration", as opposed to Cicero, who did not associate the prediction with divination. Interpretations Bertrand Russell in the History of Western Philosophy interprets Anaximander's theories as an assertion of the necessity of an appropriate balance between earth, fire, and water, all of which may be independently seeking to aggrandize their proportions relative to the others. Anaximander seems to express his belief that a natural order ensures balance among these elements, that where there was fire, ashes (earth) now exist. His Greek peers echoed this sentiment with their belief in natural boundaries beyond which not even the gods could operate. Friedrich Nietzsche, in Philosophy in the Tragic Age of the Greeks, claimed that Anaximander was a pessimist who asserted that the primal being of the world was a state of indefiniteness. In accordance with this, anything definite has to eventually pass back into indefiniteness. In other words, Anaximander viewed "...all coming-to-be as though it were an illegitimate emancipation from eternal being, a wrong for which destruction is the only penance". (Ibid., § 4) The world of individual objects, in this way of thinking, has no worth and should perish. Martin Heidegger lectured extensively on Anaximander, and delivered a lecture entitled "Anaximander's Saying" which was subsequently included in Off the Beaten Track. The lecture examines the ontological difference and the oblivion of Being or Dasein in the context of the Anaximander fragment. Heidegger's lecture is, in turn, an important influence on the French philosopher Jacques Derrida. Works According to the Suda: On Nature ( / Perì phúseôs) Rotation of the Earth ( / Gễs períodos) On Fixed stars ( / Perì tỗn aplanỗn) The [Celestial] Sphere ( / Sphaĩra) See also Material monism Indefinite monism Footnotes References Primary sources Aelian: Various History (III, 17) Aëtius: De Fide (I-III; V) Agathemerus: A Sketch of Geography in Epitome (I, 1) Aristotle: Meteorology (II, 3) Translated by E. W. Webster Aristotle: On Generation and Corruption (II, 5) Translated by H. H. Joachim Aristotle: On the Heavens (II, 13) Translated by J. L. Stocks (III, 5, 204 b 33–34) Censorinus: De Die Natali (IV, 7) See original text at LacusCurtius (I, 50, 112) Cicero: On the Nature of the Gods (I, 10, 25) Euripides: The Suppliants (532) Translated by E. P. Coleridge Eusebius of Caesarea: Preparation for the Gospel (X, 14, 11) Translated by E.H. Gifford Heidel, W.A. Anaximander's Book: PAAAS, vol. 56, n.7, 1921, pp. 239–288. Herodotus: Histories (II, 109) See original text in Perseus project Hippolytus (?): Refutation of All Heresies (I, 5) Translated by Roberts and Donaldson Pliny the Elder: Natural History (II, 8) See original text in Perseus project Pseudo-Plutarch: The Doctrines of the Philosophers (I, 3; I, 7; II, 20–28; III, 2–16; V, 19) Seneca the Younger: Natural Questions (II, 18) Simplicius: Comments on Aristotle's Physics (24, 13–25; 1121, 5–9) Strabo: Geography (I, 1) Books 1‑7, 15‑17 translated by H. L. Jones Themistius: Oratio (36, 317) The Suda (Suda On Line) Secondary sources The default source; anything not otherwise attributed should be in Conche. External links Philoctete – Anaximandre: Fragments ((Grk icon)) The Internet Encyclopedia of Philosophy – Anaximander Extensive bibliography by Dirk Couprie Anaximander entry by John Burnet contains fragments of Anaximander Anaximander of Miletus Life and Work - Fragments and Testimonies by Giannis Stamatellos 6th-century BC Greek people 6th-century BC philosophers 610s BC births 540s BC deaths Ancient Greek astronomers Ancient Greek cartographers Ancient Greek metaphysicians Ancient Greek physicists Ancient Greeks from the Achaemenid Empire Ancient Milesians Natural philosophers Philosophers of ancient Ionia Presocratic philosophers 6th-century BC geographers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1169

https://en.wikipedia.org/wiki/APL

APL

APL is an abbreviation, acronym, or initialism that may refer to: Organizations APL (shipping company), a Singapore-based container and shipping company Aden Protectorate Levies, a militia force for local defense of the Aden Protectorate Advanced Production and Loading, a Norwegian marine engineering company formed in 1993 Afghanistan Premier League, an Afghan Twenty20 cricket league Afghan Premier League, a men's football league in Afghanistan American Patriot League, a proposed American football spring league American Premier League, a proposed Twenty20 cricket league in the US American President Lines, a container transportation and shipping company American Protective League, a World War I-era pro-war organization Applied Physics Laboratory, at Johns Hopkins University Association of Pension Lawyers, UK Irish Anti-Partition League, a Northern Ireland political organisation Aurora Public Library (disambiguation), several Aurora Public Libraries use the APL abbreviation Science and technology Abductor pollicis longus muscle, in the human hand Acute promyelocytic leukemia, a subtype of acute myelogenous leukemia 132524 APL, an asteroid Nampula Airport (IATA: APL), in Mozambique Applied Physics Letters, a physics journal also abbreviated as Appl. Phys. Lett. Computers .apl, the file extension of the Monkey's Audio metadata file Address Prefix List, a DNS record type Address programming language, an early high-level programming language developed in the Soviet Union Advanced Physical Layer, an extension of Ethernet 10BASE-T1L for field devices Alexa Presentation Language, a language for developing Amazon Alexa skills APL (programming language) ("A Programming Language"), an array-based programming language APL (codepage), the character set for programming in APL AMD Performance Library, renamed Framewave, a computer compiler library in the languages C and C++ Software licences Adaptive Public License, an Open Source license from the University of Victoria, Canada AROS Public License, a license of AROS Research Operating System Arphic Public License, a free font license Other uses apl.de.ap (born 1974), pseudonym of Allan Pineda Lindo, Filipino-American musician Auxiliary Personal Living, a US Navy hull classification for barracks craft; see

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1170

https://en.wikipedia.org/wiki/Architect

Architect

An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the design of buildings and the space within the site surrounding the buildings that have human occupancy or use as their principal purpose. Etymologically, the term architect derives from the Latin architectus, which derives from the Greek (arkhi-, chief + tekton, builder), i.e., chief builder. The professional requirements for architects vary from place to place. An architect's decisions affect public safety, and thus the architect must undergo specialized training consisting of advanced education and a practicum (or internship) for practical experience to earn a license to practice architecture. Practical, technical, and academic requirements for becoming an architect vary by jurisdiction, though the formal study of architecture in academic institutions has played a pivotal role in the development of the profession as a whole. Origins Throughout ancient and medieval history, most of the architectural design and construction was carried out by artisans—such as stone masons and carpenters, rising to the role of master builder. Until modern times, there was no clear distinction between architect and engineer. In Europe, the titles architect and engineer were primarily geographical variations that referred to the same person, often used interchangeably. It is suggested that various developments in technology and mathematics allowed the development of the professional 'gentleman' architect, separate from the hands-on craftsman. Paper was not used in Europe for drawing until the 15th century but became increasingly available after 1500. Pencils were used more often for drawing by 1600. The availability of both allowed pre-construction drawings to be made by professionals. Concurrently, the introduction of linear perspective and innovations such as the use of different projections to describe a three-dimensional building in two dimensions, together with an increased understanding of dimensional accuracy, helped building designers communicate their ideas. However, the development was gradual. Until the 18th-century, buildings continued to be designed and set out by craftsmen with the exception of high-status projects. Architecture In most developed countries, only those qualified with an appropriate license, certification, or registration with a relevant body (often governmental) may legally practice architecture. Such licensure usually requires a university degree, successful completion of exams, as well as a training period. Representation of oneself as an architect through the use of terms and titles is restricted to licensed individuals by law, although in general, derivatives such as architectural designer are often not legally protected. To practice architecture implies the ability to practice independently of supervision. The term building design professional (or design professional), by contrast, is a much broader term that includes professionals who practice independently under an alternate profession, such as engineering professionals, or those who assist in the practice of architecture under the supervision of a licensed architect such as intern architects. In many places, independent, non-licensed individuals may perform design services outside the professional restrictions, such design houses and other smaller structures. Practice In the architectural profession, technical and environmental knowledge, design and construction management, and an understanding of business are as important as design. However, the design is the driving force throughout the project and beyond. An architect accepts a commission from a client. The commission might involve preparing feasibility reports, building audits, the design of a building or of several buildings, structures, and the spaces among them. The architect participates in developing the requirements the client wants in the building. Throughout the project (planning to occupancy), the architect coordinates a design team. Structural, mechanical, and electrical engineers and other specialists are hired by the client or the architect, who must ensure that the work is coordinated to construct the design. Design role The architect, once hired by a client, is responsible for creating a design concept that both meets the requirements of that client and provides a facility suitable to the required use. The architect must meet with, and question, the client in order to ascertain all the requirements (and nuances) of the planned project. Often the full brief is not entirely clear at the beginning: entailing a degree of risk in the design undertaking. The architect may make early proposals to the client, which may rework the very terms of the brief. The "program" (or brief) is essential to producing a project that meets all the needs of the owner. This then is a guide for the architect in creating the design concept. Design proposal(s) are generally expected to be both imaginative and pragmatic. Depending on the place, time, finance, culture, and available crafts and technology in which the design takes place, the precise extent and nature of these expectations will vary. Foresight is a prerequisite as designing buildings is a very complex and demanding undertaking. Any design concept must at a very early stage in its generation take into account a great number of issues and variables which include qualities of space(s), the end-use and life-cycle of these proposed spaces, connections, relations, and aspects between spaces including how they are put together as well as the impact of proposals on the immediate and wider locality. Selection of appropriate materials and technology must be considered, tested and reviewed at an early stage in the design to ensure there are no setbacks (such as higher-than-expected costs) which may occur later. The site and its environs, as well as the culture and history of the place, will also influence the design. The design must also countenance increasing concerns with environmental sustainability. The architect may introduce (intentionally or not), to greater or lesser degrees, aspects of mathematics and architecture, new or current architectural theory, or references to architectural history. A key part of the design is that the architect often consults with engineers, surveyors and other specialists throughout the design, ensuring that aspects such as the structural supports and air conditioning elements are coordinated in the scheme as a whole. The control and planning of construction costs are also a part of these consultations. Coordination of the different aspects involves a high degree of specialized communication, including advanced computer technology such as BIM (building information modeling), CAD, and cloud-based technologies. At all times in the design, the architect reports back to the client who may have reservations or recommendations, introducing a further variable into the design. Architects deal with local and federal jurisdictions about regulations and building codes. The architect might need to comply with local planning and zoning laws, such as required setbacks, height limitations, parking requirements, transparency requirements (windows), and land use. Some established jurisdictions require adherence to design and historic preservation guidelines. Health and safety risks form a vital part of the current design, and in many jurisdictions, design reports and records are required which include ongoing considerations such as materials and contaminants, waste management and recycling, traffic control and fire safety. Means of design Previously, architects employed drawings to illustrate and generate design proposals. While conceptual sketches are still widely used by architects, computer technology has now become the industry standard. However, design may include the use of photos, collages, prints, linocuts, 3D scanning technology and other media in design production. Increasingly, computer software is shaping how architects work. BIM technology allows for the creation of a virtual building that serves as an information database for the sharing of design and building information throughout the life-cycle of the building's design, construction and maintenance. Virtual reality (VR) presentations are becoming more common for visualizing structural designs and interior spaces from a point-of-view perspective. Environmental role As current buildings are now known to be high emitters of carbon into the atmosphere, increasing controls are being placed on buildings and associated technology to reduce emissions, increase energy efficiency, and make use of renewable energy sources. Renewable energy sources may be developed within the proposed building or via local or national renewable energy providers. As a result, the architect is required to remain abreast of current regulations that are continually tightening. Some new developments exhibit extremely low energy use or passive solar building design. However, the architect is also increasingly required to provide initiatives in a wider environmental sense, such as making provision for low-energy transport, natural daylighting instead of artificial lighting, natural ventilation instead of air conditioning, pollution, and waste management, use of recycled materials and employment of materials which can be easily recycled in the future. Construction role As the design becomes more advanced and detailed, specifications and detail designs are made of all the elements and components of the building. Techniques in the production of a building are continually advancing which places a demand on the architect to ensure that he or she remains up to date with these advances. Depending on the client's needs and the jurisdiction's requirements, the spectrum of the architect's services during construction stages may be extensive (detailed document preparation and construction review) or less involved (such as allowing a contractor to exercise considerable design-build functions). Architects typically put projects to tender on behalf of their clients, advise on the award of the project to a general contractor, facilitate and then administer a contract of agreement which is often between the client and the contractor. This contract is legally binding and covers a very wide range of aspects including the insurances and commitments of all stakeholders, the status of the design documents, provisions for the architect's access, and procedures for the control of the works as they proceed. Depending on the type of contract utilized, provisions for further sub-contract tenders may be required. The architect may require that some elements are covered by a warranty which specifies the expected life and other aspects of the material, product or work. In most jurisdictions, prior notification to the relevant local authority must be given before commencement on site, thus giving the local authority notice to carry out independent inspections. The architect will then review and inspect the progress of the work in coordination with the local authority. The architect will typically review contractor shop drawings and other submittals, prepare and issue site instructions, and provide Certificates for Payment to the contractor (see also Design-bid-build) which is based on the work done to date as well as any materials and other goods purchased or hired. In the United Kingdom and other countries, a quantity surveyor is often part of the team to provide cost consulting. With very large, complex projects, an independent construction manager is sometimes hired to assist in the design and to manage construction. In many jurisdictions, mandatory certification or assurance of the completed work or part of works is required. This demand for certification entails a high degree of risk - therefore, regular inspections of the work as it progresses on site is required to ensure that is in compliance with the design itself as well as with all relevant statutes and permissions. Alternate practice and specializations Recent decades have seen the rise of specializations within the profession. Many architects and architectural firms focus on certain project types (for example, healthcare, retail, public housing, event management), technological expertise or project delivery methods. Some architects specialize as building code, building envelope, sustainable design, technical writing, historic preservation(US) or conservation (UK), accessibility and other forms of specialist consultants. Many architects elect to move into real estate (property) development, corporate facilities planning, project management, construction management, chief sustainability officers interior design, city planning, user experience design, design researcher or other related fields. Professional requirements Although there are variations from place to place, most of the world's architects are required to register with the appropriate jurisdiction. To do so, architects are typically required to meet three common requirements: education, experience, and examination. Educational requirements generally consist of a university degree in architecture. The experience requirement for degree candidates is usually satisfied by a practicum or internship (usually two to three years, depending on jurisdiction). Finally, a Registration Examination or a series of exams is required prior to licensure. Professionals engaged in the design and supervision of construction projects prior to the late 19th century were not necessarily trained in a separate architecture program in an academic setting. Instead, they often trained under established architects. Prior to modern times, there was no distinction between architects and engineers and the title used varied depending on geographical location. They often carried the title of master builder or surveyor after serving a number of years as an apprentice (such as Sir Christopher Wren). The formal study of architecture in academic institutions played a pivotal role in the development of the profession as a whole, serving as a focal point for advances in architectural technology and theory. The use of "Architect" or abbreviations such as "Ar." as a title attached to a person's name is regulated by law in some countries. Fees Architects' fee structures are typically based on a percentage of construction value, as a rate per unit area of the proposed construction, hourly rates or a fixed lump sum fee. Combinations of these structures are also common. Fixed fees are usually based on a project's allocated construction cost and can range between 4 and 12% of new construction cost, for commercial and institutional projects, depending on a project's size and complexity. Residential projects range from 12 to 20%. Renovation projects typically command higher percentages, as high as 15-20%. Overall billings for architectural firms range widely, depending on location and economic climate. Billings have traditionally been dependent on the local economic conditions but, with rapid globalization, this is becoming less of a factor for larger international firms. Salaries also vary, depending on experience, position within the firm (staff architect, partner, or shareholder, etc.), and the size and location of the firm. Professional organizations A number of national professional organizations exist to promote career and business development in architecture. The International Union of Architects (UIA) The American Institute of Architects (AIA) USA Royal Institute of British Architects (RIBA) UK Architects Registration Board (ARB) UK The Australian Institute of Architects (AIA) Australia The South African Institute of Architects (SAIA) South Africa Association of Consultant Architects (ACA) UK Association of Licensed Architects (ALA) USA The Consejo Profesional de Arquitectura y Urbanismo (CPAU) Argentina Indian Institute of Architects (IIA) & Council of Architecture (COA) India The National Organization of Minority Architects (NOMA) USA Prizes, awards A wide variety of prizes is awarded by national professional associations and other bodies, recognizing accomplished architects, their buildings, structures, and professional careers. The most lucrative award an architect can receive is the Pritzker Prize, sometimes termed the "Nobel Prize for architecture." The inaugural Pritzker Prize winner was Philip Johnson who was cited "for 50 years of imagination and vitality embodied in a myriad of museums, theatres libraries, houses gardens and corporate structure". The Pritzker Prize has been awarded for forty-two straight editions without interruption, and there are now 22 countries with at least one winning architect. Other prestigious architectural awards are the Royal Gold Medal, the AIA Gold Medal (USA), AIA Gold Medal (Australia), and the Praemium Imperiale. Architects in the UK, who have made contributions to the profession through design excellence or architectural education, or have in some other way advanced the profession, might until 1971 be elected Fellows of the Royal Institute of British Architects and can write FRIBA after their name if they feel so inclined. Those elected to chartered membership of the RIBA after 1971 may use the initials RIBA but cannot use the old ARIBA and FRIBA. An Honorary Fellow may use the initials, Hon. FRIBA. and an International Fellow may use the initials Int. FRIBA. Architects in the US, who have made contributions to the profession through design excellence or architectural education, or have in some other way advanced the profession, are elected Fellows of the American Institute of Architects and can write FAIA after their name. Architects in Canada, who have made outstanding contributions to the profession through contribution to research, scholarship, public service, or professional standing to the good of architecture in Canada, or elsewhere, may be recognized as a Fellow of the Royal Architectural Institute of Canada and can write FRAIC after their name. In Hong Kong, those elected to chartered membership may use the initial HKIA, and those who have made a special contribution after nomination and election by The Hong Kong Institute of Architects (HKIA), may be elected as fellow members of HKIA and may use FHKIA after their name. Architects in the Philippines and Filipino communities overseas (whether they are Filipinos or not), especially those who also profess other jobs at the same time, are addressed and introduced as Architect, rather than Sir/Madam in speech or Mr./Mrs./Ms. (G./Gng./Bb. in Filipino) before surnames. That word is used either in itself or before the given name or surname. See also References Architecture occupations Professional certification in architecture

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1176

https://en.wikipedia.org/wiki/Antisymmetric%20relation

Antisymmetric relation

In mathematics, a binary relation on a set is antisymmetric if there is no pair of distinct elements of each of which is related by to the other. More formally, is antisymmetric precisely if for all or equivalently, The definition of antisymmetry says nothing about whether actually holds or not for any . An antisymmetric relation on a set may be reflexive (that is, for all ), irreflexive (that is, for no ), or neither reflexive nor irreflexive. A relation is asymmetric if and only if it is both antisymmetric and irreflexive. Examples The divisibility relation on the natural numbers is an important example of an antisymmetric relation. In this context, antisymmetry means that the only way each of two numbers can be divisible by the other is if the two are, in fact, the same number; equivalently, if and are distinct and is a factor of then cannot be a factor of For example, 12 is divisible by 4, but 4 is not divisible by 12. The usual order relation on the real numbers is antisymmetric: if for two real numbers and both inequalities and hold then and must be equal. Similarly, the subset order on the subsets of any given set is antisymmetric: given two sets and if every element in also is in and every element in is also in then and must contain all the same elements and therefore be equal: A real-life example of a relation that is typically antisymmetric is "paid the restaurant bill of" (understood as restricted to a given occasion). Typically some people pay their own bills, while others pay for their spouses or friends. As long as no two people pay each other's bills, the relation is antisymmetric. Properties Partial and total orders are antisymmetric by definition. A relation can be both symmetric and antisymmetric (in this case, it must be coreflexive), and there are relations which are neither symmetric nor antisymmetric (for example, the "preys on" relation on biological species). Antisymmetry is different from asymmetry: a relation is asymmetric if and only if it is antisymmetric and irreflexive. See also References nLab antisymmetric relation Binary relations

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1178

https://en.wikipedia.org/wiki/Afterlife

Afterlife

The afterlife (also referred to as life after death or the world to come) is a purported existence in which the essential part of an individual's identity or their stream of consciousness continues to live after the death of their physical body. According to various ideas about the afterlife, the essential aspect of the individual that lives on after death may be some partial element, or the entire soul or spirit of an individual, which carries with it and may confer personal identity or, on the contrary nirvana. Belief in an afterlife is in contrast to the belief in oblivion after death. In some views, this continued existence takes place in a spiritual realm, and in other popular views, the individual may be reborn into this world and begin the life cycle over again, likely with no memory of what they have done in the past. In this latter view, such rebirths and deaths may take place over and over again continuously until the individual gains entry to a spiritual realm or otherworld. Major views on the afterlife derive from religion, esotericism and metaphysics. Some belief systems, such as those in the Abrahamic tradition, hold that the dead go to a specific plane of existence after death, as determined by God, or other divine judgment, based on their actions or beliefs during life. In contrast, in systems of reincarnation, such as those in the Indian religions, the nature of the continued existence is determined directly by the actions of the individual in the ended life. Different metaphysical models Theists generally believe some afterlife awaits people when they die. Members of some generally non-theistic religions tend to believe in an afterlife but without reference to a deity. The Sadducees were an ancient Jewish sect that generally believed that there was a God but no existence after death. Many religions, whether they believe in the soul's existence in another world like Christianity, Islam, and many pagan belief systems, or reincarnation like many forms of Hinduism and Buddhism, believe that one's status in the afterlife is a consequence of one's conduct during life. Reincarnation Reincarnation is the philosophical or religious concept that an aspect of a living being starts a new life in a different physical body or form after each death. This concept is also known as rebirth or transmigration and is part of the Saṃsāra doctrine of cyclic existence. It is a central tenet of all major Indian religions, namely Buddhism, Hinduism, Jainism, and Sikhism. The idea of reincarnation is found in many ancient cultures, and a belief in rebirth/metempsychosis was held by historic Greek figures, such as Pythagoras, Socrates, and Plato. It is also a common belief of various ancient and modern religions such as Spiritism, Theosophy, and Eckankar. It is found as well in many tribal societies around the world, in places such as Australia, East Asia, Siberia, and South America. Although the majority of denominations within the Abrahamic religions of Judaism, Christianity, and Islam do not believe that individuals reincarnate, particular groups within these religions do refer to reincarnation; these groups include the mainstream historical and contemporary followers of Kabbalah, the Cathars, Alawites, the Druze, and the Rosicrucians. The historical relations between these sects and the beliefs about reincarnation that were characteristic of Neoplatonism, Orphism, Hermeticism, Manicheanism, and Gnosticism of the Roman era as well as the Indian religions have been the subject of recent scholarly research. Unity Church and its founder Charles Fillmore teach reincarnation. Rosicrucians speak of a life review period occurring immediately after death and before entering the afterlife's planes of existence (before the silver cord is broken), followed by a judgment, more akin to a final review or end report over one's life. Heaven and Hell Heaven, the heavens, Seven Heavens, pure lands, Tian, Jannah, Valhalla, or the Summerland, is a common religious, cosmological, or transcendent place where beings such as gods, angels, jinn, saints, or venerated ancestors are said to originate, be enthroned, or live. According to the beliefs of some religions, heavenly beings can descend to earth or incarnate, and earthly beings can ascend to heaven in the afterlife, or in exceptional cases, enter heaven alive. Heaven is often described as a "higher place", the holiest place, a paradise, in contrast to hell or the underworld or the "low places", and universally or conditionally accessible by earthly beings according to various standards of divinity, goodness, piety, faith or other virtues or right beliefs or simply the will of God. Some believe in the possibility of a heaven on Earth in a world to come. In Hinduism, heaven is considered as Svarga loka. There are seven positive regions the soul can go to after death and seven negative regions. After completing its stay in the respective region, the soul is subjected to rebirth in different living forms according to its karma. This cycle can be broken after a soul achieves Moksha or Nirvana. Any place of existence, either of humans, souls or deities, outside the tangible world (heaven, hell, or other) is referred to as otherworld. Hell, in many religious and folkloric traditions, is a place of torment and punishment in the afterlife. Religions with a linear divine history often depict hell as an eternal destination, while religions with a cyclic history often depict a hell as an intermediary period between incarnations. Typically, these traditions locate hell in another dimension or under the earth's surface and often include entrances to hell from the land of the living. Other afterlife destinations include purgatory and limbo. Traditions that do not conceive of the afterlife as a place of punishment or reward merely describe hell as an abode of the dead, the grave, a neutral place (for example, Sheol or Hades) located under the surface of earth. Ancient religions Ancient Egyptian religion The afterlife played an important role in Ancient Egyptian religion, and its belief system is one of the earliest known in recorded history. When the body died, parts of its soul known as ka (body double) and the ba (personality) would go to the Kingdom of the Dead. While the soul dwelt in the Fields of Aaru, Osiris demanded work as restitution for the protection he provided. Statues were placed in the tombs to serve as substitutes for the deceased. Arriving at one's reward in afterlife was a demanding ordeal, requiring a sin-free heart and the ability to recite the spells, passwords, and formulae of the Book of the Dead. In the Hall of Two Truths, the deceased's heart was weighed against the Shu feather of truth and justice taken from the headdress of the goddess Ma'at. If the heart was lighter than the feather, they could pass on, but if it were heavier they would be devoured by the demon Ammit. Egyptians also believed that being mummified and put in a sarcophagus (an ancient Egyptian "coffin" carved with complex symbols and designs, as well as pictures and hieroglyphs) was the only way to have an afterlife. What are referred to as the Coffin Texts, are inscribed on a coffin and serve as a guide for the challenges in the afterlife. The Coffin texts are more or less a duplication of the Pyramid Texts, which would serve as a guide for Egyptian pharaohs or queens in the afterlife. Only if the corpse had been properly embalmed and entombed in a mastaba, could the dead live again in the Fields of Yalu and accompany the Sun on its daily ride. Due to the dangers the afterlife posed, the Book of the Dead was placed in the tomb with the body as well as food, jewelry, and 'curses'. They also used the "opening of the mouth". Ancient Egyptian civilization was based on religion. The belief in the rebirth after death became the driving force behind funeral practices. Death was simply a temporary interruption, rather than complete cessation of life. Eternal life could be ensured by means like piety to the gods, preservation of the physical form through mummification, and the provision of statuary and other funerary equipment. Each human consisted of the physical body, the ka, the ba, and the akh. The Name and Shadow were also living entities. To enjoy the afterlife, all these elements had to be sustained and protected from harm. On 30 March 2010, a spokesman for the Egyptian Culture Ministry claimed it had unearthed a large red granite door in Luxor with inscriptions by User, a powerful adviser to the 18th Dynasty Queen Hatshepsut who ruled between 1479 BC and 1458 BC, the longest of any woman. It believes the false door is a 'door to the Afterlife'. According to the archaeologists, the door was reused in a structure in Roman Egypt. Ancient Greek and Roman religions The Greek god Hades is known in Greek mythology as the king of the underworld, a place where souls live after death. The Greek god Hermes, the messenger of the gods, would take the dead soul of a person to the underworld (sometimes called Hades or the House of Hades). Hermes would leave the soul on the banks of the River Styx, the river between life and death. Charon, also known as the ferry-man, would take the soul across the river to Hades, if the soul had gold: Upon burial, the family of the dead soul would put coins under the deceased's tongue. Once crossed, the soul would be judged by Aeacus, Rhadamanthus and King Minos. The soul would be sent to Elysium, Tartarus, or Asphodel Fields. The Elysian Fields were for the ones that lived pure lives. It consisted of green fields, valleys and mountains, everyone there was peaceful and contented, and the Sun always shone there. Tartarus was for the people that blasphemed against the gods, or were simply rebellious and consciously evil. The Asphodel Fields were for a varied selection of human souls including those whose sins equalled their goodness, those who were indecisive in their lives, and those who were not judged. Those who had sinned went to the deepest pit, Tartarus. In Tartarus, the soul would be punished by being burned in lava, or stretched on racks. Some heroes of Greek legend are allowed to visit the underworld. The Romans had a similar belief system about the afterlife, with Hades becoming known as Pluto. In the ancient Greek myth about the Labours of Heracles, the hero Heracles had to travel to the underworld to capture Cerberus, the three-headed guard dog, as one of his tasks. In Dream of Scipio, Cicero describes what seems to be an out of body experience, of the soul traveling high above the Earth, looking down at the small planet, from far away. In Book VI of Virgil's Aeneid, the hero, Aeneas, travels to the underworld to see his father. By the River Styx, he sees the souls of those not given a proper burial, forced to wait by the river until someone buries them. While down there, along with the dead, he is shown the place where the wrongly convicted reside, the fields of sorrow where those who committed suicide and now regret it reside, including Aeneas' former lover, the warriors and shades, Tartarus (where the titans and powerful non-mortal enemies of the Olympians reside) where he can hear the groans of the imprisoned, the palace of Pluto, and the fields of Elysium where the descendants of the divine and bravest heroes reside. He sees the river of forgetfulness, Lethe, which the dead must drink to forget their life and begin anew. Lastly, his father shows him all of the future heroes of Rome who will live if Aeneas fulfills his destiny in founding the city. Norse religion The Poetic and Prose Eddas, the oldest sources for information on the Norse concept of the afterlife, vary in their description of the several realms that are described as falling under this topic. The most well-known are: Valhalla: (lit. "Hall of the Slain" i.e. "the Chosen Ones") Half the warriors who die in battle join the god Odin who rules over a majestic hall called Valhalla in Asgard. Fólkvangr: (lit. "Field of the Host") The other half join the goddess Freyja in a great meadow known as Fólkvangr. Hel: (lit. "The Covered Hall") Niflhel: (lit. "The Dark" or "Misty Hel") Abrahamic religions Judaism Sheol Sheol, in the Hebrew Bible, is a place of darkness (Job x. 21, 22) to which all the dead go, both the righteous and the unrighteous, regardless of the moral choices made in life, (Gen. xxxvii. 36; Ezek. xxxii.; Isa. xiv.; Job xxx. 23), a place of stillness, (Ps. lxxxviii. 13, xciv. 17; Eccl. ix. 10), at the longest possible distance from heaven (Job xi. 8; Amos ix. 2; Ps. cxxxix. 8). The inhabitants of Sheol are the "shades" (rephaim), entities without personality or strength. Under some circumstances they are thought to be able to be contacted by the living, as the Witch of Endor contacts the shade of Samuel for Saul, but such practices are forbidden (Deuteronomy 18:10). While the Hebrew Bible appears to describe Sheol as the permanent place of the dead, in the Second Temple period (roughly 500 BC – 70 AD) a more diverse set of ideas developed. In some texts, Sheol is considered to be the home of both the righteous and the wicked, separated into respective compartments; in others, it was considered a place of punishment, meant for the wicked dead alone. When the Hebrew scriptures were translated into Greek in ancient Alexandria around 200 BC, the word "Hades" (the Greek underworld) was substituted for Sheol. This is reflected in the New Testament where Hades is both the underworld of the dead and the personification of the evil it represents. World to Come The Talmud offers a number of thoughts relating to the afterlife. After death, the soul is brought for judgment. Those who have led pristine lives enter immediately into the Olam Haba or world to come. Most do not enter the world to come immediately, but experience a period of reflection of their earthly actions and are made aware of what they have done wrong. Some view this period as being a "re-schooling", with the soul gaining wisdom as one's errors are reviewed. Others view this period to include spiritual discomfort for past wrongs. At the end of this period, not longer than one year, the soul then takes its place in the world to come. Although discomforts are made part of certain Jewish conceptions of the afterlife, the concept of eternal damnation is not a tenet of the Jewish afterlife. According to the Talmud, extinction of the soul is reserved for a far smaller group of malicious and evil leaders, either whose very evil deeds go way beyond norms, or who lead large groups of people to utmost evil. This is also part of Maimonides' 13 principles of faith. Maimonides describes the Olam Haba in spiritual terms, relegating the prophesied physical resurrection to the status of a future miracle, unrelated to the afterlife or the Messianic era. According to Maimonides, an afterlife continues for the soul of every human being, a soul now separated from the body in which it was "housed" during its earthly existence. The Zohar describes Gehenna not as a place of punishment for the wicked but as a place of spiritual purification for souls. Reincarnation in Jewish tradition Although there is no reference to reincarnation in the Talmud or any prior writings, according to rabbis such as Avraham Arieh Trugman, reincarnation is recognized as being part and parcel of Jewish tradition. Trugman explains that it is through oral tradition that the meanings of the Torah, its commandments and stories, are known and understood. The classic work of Jewish mysticism, the Zohar, is quoted liberally in all Jewish learning; in the Zohar the idea of reincarnation is mentioned repeatedly. Trugman states that in the last five centuries the concept of reincarnation, which until then had been a much hidden tradition within Judaism, was given open exposure. Shraga Simmons commented that within the Bible itself, the idea [of reincarnation] is intimated in Deut. 25:5–10, Deut. 33:6 and Isaiah 22:14, 65:6. Yirmiyahu Ullman wrote that reincarnation is an "ancient, mainstream belief in Judaism". The Zohar makes frequent and lengthy references to reincarnation. Onkelos, a righteous convert and authoritative commentator of the same period, explained the verse, "Let Reuben live and not die ..." (Deuteronomy 33:6) to mean that Reuben should merit the World to Come directly, and not have to die again as a result of being reincarnated. Torah scholar, commentator and kabbalist, Nachmanides (Ramban 1195–1270), attributed Job's suffering to reincarnation, as hinted in Job's saying "God does all these things twice or three times with a man, to bring back his soul from the pit to... the light of the living' (Job 33:29, 30)." Reincarnation, called gilgul, became popular in folk belief, and is found in much Yiddish literature among Ashkenazi Jews. Among a few kabbalists, it was posited that some human souls could end up being reincarnated into non-human bodies. These ideas were found in a number of Kabbalistic works from the 13th century, and also among many mystics in the late 16th century. Martin Buber's early collection of stories of the Baal Shem Tov's life includes several that refer to people reincarnating in successive lives. Among well known (generally non-kabbalist or anti-kabbalist) rabbis who rejected the idea of reincarnation are Saadia Gaon, David Kimhi, Hasdai Crescas, Yedayah Bedershi (early 14th century), Joseph Albo, Abraham ibn Daud, the Rosh and Leon de Modena. Saadia Gaon, in Emunoth ve-Deoth (Hebrew: "beliefs and opinions") concludes Section VI with a refutation of the doctrine of metempsychosis (reincarnation). While rebutting reincarnation, Saadia Gaon further states that Jews who hold to reincarnation have adopted non-Jewish beliefs. By no means do all Jews today believe in reincarnation, but belief in reincarnation is not uncommon among many Jews, including Orthodox. Other well-known rabbis who are reincarnationists include Yonassan Gershom, Abraham Isaac Kook, Talmud scholar Adin Steinsaltz, DovBer Pinson, David M. Wexelman, Zalman Schachter, and many others. Reincarnation is cited by authoritative biblical commentators, including Ramban (Nachmanides), Menachem Recanti and Rabbenu Bachya. Among the many volumes of Yitzchak Luria, most of which come down from the pen of his primary disciple, Chaim Vital, are insights explaining issues related to reincarnation. His Shaar HaGilgulim, "The Gates of Reincarnation", is a book devoted exclusively to the subject of reincarnation in Judaism. Rabbi Naftali Silberberg of The Rohr Jewish Learning Institute notes that "Many ideas that originate in other religions and belief systems have been popularized in the media and are taken for granted by unassuming Jews." Christianity Mainstream Christianity professes belief in the Nicene Creed, and English versions of the Nicene Creed in current use include the phrase: "We look for the resurrection of the dead, and the life of the world to come." When questioned by the Sadducees about the resurrection of the dead (in a context relating to who one's spouse would be if one had been married several times in life), Jesus said that marriage will be irrelevant after the resurrection as the resurrected will be like the angels in heaven. Jesus also maintained that the time would come when the dead would hear the voice of the Son of God, and all who were in the tombs would come out; those who have heard His "[commandments] and believes in the one who sent [Him]" to the resurrection of life, but those who do not to the resurrection of condemnation. The Book of Enoch describes Sheol as divided into four compartments for four types of the dead: the faithful saints who await resurrection in Paradise, the merely virtuous who await their reward, the wicked who await punishment, and the wicked who have already been punished and will not be resurrected on Judgment Day. The Book of Enoch is considered apocryphal by most denominations of Christianity and all denominations of Judaism. The book of 2 Maccabees gives a clear account of the dead awaiting a future resurrection and judgment in addition to prayers and offerings for the dead to remove the burden of sin. The author of Luke recounts the story of Lazarus and the rich man, which shows people in Hades awaiting the resurrection either in comfort or torment. The author of the Book of Revelation writes about God and the angels versus Satan and demons in an epic battle at the end of times when all souls are judged. There is mention of ghostly bodies of past prophets, and the transfiguration. The non-canonical Acts of Paul and Thecla speak of the efficacy of prayer for the dead so that they might be "translated to a state of happiness". Hippolytus of Rome pictures the underworld (Hades) as a place where the righteous dead, awaiting in the bosom of Abraham their resurrection, rejoice at their future prospect, while the unrighteous are tormented at the sight of the "lake of unquenchable fire" into which they are destined to be cast. Gregory of Nyssa discusses the long-before believed possibility of purification of souls after death. Pope Gregory I repeats the concept, articulated over a century earlier by Gregory of Nyssa that the saved suffer purification after death, in connection with which he wrote of "purgatorial flames". The noun "purgatorium" (Latin: place of cleansing) is used for the first time to describe a state of painful purification of the saved after life. The same word in adjectival form (purgatorius -a -um, cleansing), which appears also in non-religious writing, was already used by Christians such as Augustine of Hippo and Pope Gregory I to refer to an after-death cleansing. During the Age of Enlightenment, theologians and philosophers presented various philosophies and beliefs. A notable example is Emanuel Swedenborg who wrote some 18 theological works which describe in detail the nature of the afterlife according to his claimed spiritual experiences, the most famous of which is Heaven and Hell. His report of life there covers a wide range of topics, such as marriage in heaven (where all angels are married), children in heaven (where they are raised by angel parents), time and space in heaven (there are none), the after-death awakening process in the World of Spirits (a place halfway between Heaven and Hell and where people first wake up after death), the allowance of a free will choice between Heaven or Hell (as opposed to being sent to either one by God), the eternity of Hell (one could leave but would never want to), and that all angels or devils were once people on earth. The Catholic Church The "Spiritual Combat", a written work by Lorenzo Scupoli, states that four assaults are attempted by the "evil one" at the hour of death. The Catholic conception of the afterlife teaches that after the body dies, the soul is judged, the righteous and free of sin enter Heaven. However, those who die in unrepented mortal sin go to hell. In the 1990s, the Catechism of the Catholic Church defined hell not as punishment imposed on the sinner but rather as the sinner's self-exclusion from God. Unlike other Christian groups, the Catholic Church teaches that those who die in a state of grace, but still carry venial sin, go to a place called Purgatory where they undergo purification to enter Heaven. Limbo Despite popular opinion, Limbo, which was elaborated upon by theologians beginning in the Middle Ages, was never recognized as a dogma of the Catholic Church, yet, at times, it has been a very popular theological theory within the Church. Limbo is a theory that unbaptized but innocent souls, such as those of infants, virtuous individuals who lived before Jesus Christ was born on earth, or those that die before baptism exist in neither Heaven or Hell proper. Therefore, these souls neither merit the beatific vision, nor are subjected to any punishment, because they are not guilty of any personal sin although they have not received baptism, so still bear original sin. So they are generally seen as existing in a state of natural, but not supernatural, happiness, until the end of time. In other Christian denominations it has been described as an intermediate place or state of confinement in oblivion and neglect. Purgatory The notion of purgatory is associated particularly with the Catholic Church. In the Catholic Church, all those who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven or the final purification of the elect, which is entirely different from the punishment of the damned. The tradition of the church, by reference to certain texts of scripture, speaks of a "cleansing fire" although it is not always called purgatory. Anglicans of the Anglo-Catholic tradition generally also hold to the belief. John Wesley, the founder of Methodism, believed in an intermediate state between death and the resurrection of the dead and in the possibility of "continuing to grow in holiness there", but Methodism does not officially affirm this belief and denies the possibility of helping by prayer any who may be in that state. Orthodox Christianity The Orthodox Church is intentionally reticent on the afterlife, as it acknowledges the mystery especially of things that have not yet occurred. Beyond the second coming of Jesus, bodily resurrection, and final judgment, all of which is affirmed in the Nicene Creed (325 CE), Orthodoxy does not teach much else in any definitive manner. Unlike Western forms of Christianity, however, Orthodoxy is traditionally non-dualist and does not teach that there are two separate literal locations of heaven and hell, but instead acknowledges that "the 'location' of one's final destiny—heaven or hell—as being figurative." Instead, Orthodoxy teaches that the final judgment is simply one's uniform encounter with divine love and mercy, but this encounter is experienced multifariously depending on the extent to which one has been transformed, partaken of divinity, and is therefore compatible or incompatible with God. "The monadic, immutable, and ceaseless object of eschatological encounter is therefore the love and mercy of God, his glory which infuses the heavenly temple, and it is the subjective human reaction which engenders multiplicity or any division of experience." For instance, St. Isaac the Syrian observes that "those who are punished in Gehenna, are scourged by the scourge of love. ... The power of love works in two ways: it torments sinners ... [as] bitter regret. But love inebriates the souls of the sons of Heaven by its delectability." In this sense, the divine action is always, immutably, and uniformly love and if one experiences this love negatively, the experience is then one of self-condemnation because of free will rather than condemnation by God. Orthodoxy therefore uses the description of Jesus' judgment in John 3:19–21 as their model: "19 And this is the judgment: the light has come into the world, and people loved the darkness rather than the light because their works were evil. 20 For everyone who does wicked things hates the light and does not come to the light, lest his works should be exposed. 21 But whoever does what is true comes to the light, so that it may be clearly seen that his works have been carried out in God." As a characteristically Orthodox understanding, then, Fr. Thomas Hopko writes, "[I]t is precisely the presence of God's mercy and love which cause the torment of the wicked. God does not punish; he forgives... . In a word, God has mercy on all, whether all like it or not. If we like it, it is paradise; if we do not, it is hell. Every knee will bend before the Lord. Everything will be subject to Him. God in Christ will indeed be "all and in all," with boundless mercy and unconditional pardon. But not all will rejoice in God's gift of forgiveness, and that choice will be judgment, the self-inflicted source of their sorrow and pain." Moreover, Orthodoxy includes a prevalent tradition of apokatastasis, or the restoration of all things in the end. This has been taught most notably by Origen, but also many other Church fathers and Saints, including Gregory of Nyssa. The Second Council of Constantinople (553 CE) affirmed the orthodoxy of Gregory of Nyssa while simultaneously condemning Origen's brand of universalism because it taught the restoration back to our pre-existent state, which Orthodoxy doesn't teach. It is also a teaching of such eminent Orthodox theologians as Olivier Clément, Metropolitan Kallistos Ware, and Bishop Hilarion Alfeyev. Although apokatastasis is not a dogma of the church but instead a theologoumenon, it is no less a teaching of the Orthodox Church than its rejection. As Met. Kallistos Ware explains, "It is heretical to say that all must be saved, for this is to deny free will; but, it is legitimate to hope that all may be saved," as insisting on torment without end also denies free will. The Church of Jesus Christ of Latter-day Saints Joseph F. Smith of The Church of Jesus Christ of Latter-day Saints presents an elaborate vision of the afterlife. It is revealed as the scene of an extensive missionary effort by righteous spirits in paradise to redeem those still in darkness—a spirit prison or "hell" where the spirits of the dead remain until judgment. It is divided into two parts: Spirit Prison and Paradise. Together these are also known as the Spirit World (also Abraham's Bosom; see Luke 16:19–25). They believe that Christ visited spirit prison (1 Peter 3:18–20) and opened the gate for those who repent to cross over to Paradise. This is similar to the Harrowing of Hell doctrine of some mainstream Christian faiths. Both Spirit Prison and Paradise are temporary according to Latter-day Saint beliefs. After the resurrection, spirits are assigned "permanently" to three degrees of heavenly glory, determined by how they lived – Celestial, Terrestrial, and Telestial. (1 Cor 15:44–42; Doctrine and Covenants, Section 76) Sons of Perdition, or those who have known and seen God and deny it, will be sent to the realm of Satan, which is called Outer Darkness, where they shall live in misery and agony forever. However, according to the beliefs of the Church of Jesus Christ of Latter Day Saints, most persons lack the amount of knowledge to commit the Eternal sin and are therefore incapable of becoming sons of perdition. The Celestial Kingdom is believed to be a place where the righteous can live eternally with their families. Progression does not end once one has entered the Celestial Kingdom, but extends eternally. According to "True to the Faith" (a handbook on doctrines in the LDS faith), "The celestial kingdom is the place prepared for those who have "received the testimony of Jesus" and been "made perfect through Jesus the mediator of the new covenant, who wrought out this perfect atonement through the shedding of his own blood" (Doctrine and Covenants, 76:51, 69). To inherit this gift, we must receive the ordinances of salvation, keep the commandments, and repent of our sins." Jehovah's Witnesses Jehovah's Witnesses occasionally use terms such as "afterlife" to refer to any hope for the dead, but they understand Ecclesiastes 9:5 to preclude belief in an immortal soul. Individuals judged by God to be wicked, such as in the Great Flood or at Armageddon, are given no hope of an afterlife. However, they believe that after Armageddon there will be a bodily resurrection of "both righteous and unrighteous" dead (but not the "wicked"). Survivors of Armageddon and those who are resurrected are then to gradually restore earth to a paradise. After Armageddon, unrepentant sinners are punished with eternal death (non-existence). Seventh-day Adventists The Seventh-day Adventist Church's beliefs regarding the afterlife differ from other Christian churches. Rather than ascend to Heaven or descend to Hell, Adventists believe the dead "remain unconscious until the return of Christ in judgement". The concept that the dead remain dead until resurrection is one of the fundamental beliefs of Seventh-day Adventist. Adventists believe that death is an unconscious state (a “sleep”). This is based on Matt. 9:24; Mark 5:39; John 11:11-14; 1 Cor. 15:51, 52; 1 Thess. 4:13-17; 2 Peter 3:4; Eccl. 9:5, 6, 10. At death, all consciousness ends. The dead person does not know anything and does not do anything. They believe that death is creation, only in reverse. Ecclesiastes 12:7. When a person dies, the body turns to dust again, and the spirit goes back to God, who gave it. The spirit of every person who dies—whether saved or unsaved—returns to God at death. The spirit that returns to God at death is the breath of life. Islam The Quran (the holy book of Islam), emphasizes the insignificance of worldly life (ḥayāt ad-dunyā usually translated as "this world") vis-a-vis the hereafter. A central doctrine of Islamic faith is the Last Day (al-yawm al-ākhir, also known by other names), on which the world will come to an end and God will raise all mankind (as well as the jinn) from the dead and evaluate their worldly actions. The resurrected will be judged according to their deeds, records of which are kept on two books compiled for every human being—one for their good deeds and one for their evil ones. Having been judged, the resurrected will cross the bridge of As-Sirāt over the pit of hell; when the condemned attempt to they will be made to fall off into hellfire below; while the righteous will have no trouble and continue on to their eternal abode of heaven. Afterlife in Islam actually begins before the Last Day. After death, humans will be questioned about their faith by two angels, Munkar and Nakīr. Those who die as martyrs go immediately to paradise. Others who have died and been buried, will receive a taste of their eternal reward from the al-qabr or "the grave" (compare the Jewish concept of Sheol). Those bound for hell will suffer "punishment of the grave", while those bound for heaven will find the grave "peaceful and blessed". Islamic scripture — the Quran and hadith (reports of the words and deeds of the Islamic Prophet Muhammad who is believed to have visited heaven and hell during his Isra and Mi'raj journey) -- give vivid descriptions of the pleasures of paradise (Jannah) and sufferings of hell (Jahannam). The gardens of jannah have cool shade adorned couchs and cushions rich carpets spread out, cups full of wine and every meat and fruit . Men will be provided with perpetually youthful, beautiful ḥūr, "untouched beforehand by man or jinn", with large, beautiful eyes . (In recent years some have argued that the term ḥūr refers both to pure men and pure women, and/or that Quranic references to "immortal boys" (, ) or "young men" () (ghilmān, wildān, and suqāh) who serve wine and meals to the blessed, are the male equivalents of hur.) In contrast, those in Jahannam will dwell in a land infested with thousands of serpents and scorpions; be "burnt" by "scorching fire" and when "their skins are roasted through, We shall change them for fresh skins" to repeat the process forever ; they will have nothing to drink but "boiling water and running sores" ; their cries of remorse and pleading for forgiveness will be in vain . Traditionally jannah and jahannam are thought to have different levels. Eight gates and eight levels in Jannah, where the higher the level the better it is and the happier you are. Jahannam possess seven layers. Each layer more horrible than the one above. The Quran teaches that the purpose of Man's creation is to worship God and God alone. Those it describes as being punished in hell are "most typically", unbelievers, including those who worship others besides Allah , those who deny the divine origin of the Quran , or the coming of Judgement Day . Straightforward crimes/sins against other people are also grounds for going to hell: the murder of a believer , usury (Q.2:275), devouring the property of an orphan , slander , particularly of a chaste woman . However it is a common belief among Muslims that whatever crimes/sins Muslims may have committed, their punishment in hell will be temporary. Only unbelievers will reside in hell permanently. Thus Jahannam combines both the concept of an eternal hell (for unbelievers), and what is known in Christian Catholicism as purgatory (for believers eventually destined for heaven after punishment for their sins). The common belief holds that Jahannam coexists with the temporal world. Mainstream Islam teaches the continued existence of the soul and a transformed physical existence after death. The resurrection that will take place on the Last Day is physical, and is explained by suggesting that God will re-create the decayed body ("Have they not realized that Allah, Who created the heavens and the earth, can ˹easily˺ re-create them?" ). Ahmadiyya Ahmadi Muslims believe that the afterlife is not material but of a spiritual nature. According to Mirza Ghulam Ahmad, founder of the Ahmadiyya Muslim Community, the soul will give birth to another rarer entity and will resemble the life on this earth in the sense that this entity will bear a similar relationship to the soul as the soul bears relationship with the human existence on earth. On earth, if a person leads a righteous life and submits to the will of God, his or her tastes become attuned to enjoying spiritual pleasures as opposed to carnal desires. With this, an "embryonic soul" begins to take shape. Different tastes are said to be born which a person given to carnal passions finds no enjoyment. For example, sacrifice of one's own rights over that of others becomes enjoyable, or that forgiveness becomes second nature. In such a state a person finds contentment and peace at heart and at this stage, according to Ahmadiyya beliefs, it can be said that a soul within the soul has begun to take shape. Sufism The Sufi Muslim scholar Ibn 'Arabi defined Barzakh as the intermediate realm or "isthmus". It is between the world of corporeal bodies and the world of spirits, and is a means of contact between the two worlds. Without it, there would be no contact between the two and both would cease to exist. He described it as simple and luminous, like the world of spirits, but also able to take on many different forms just like the world of corporeal bodies can. In broader terms Barzakh, "is anything that separates two things". It has been called the dream world in which the dreamer is in both life and death. Baháʼí Faith The teachings of the Baháʼí Faith state that the nature of the afterlife is beyond the understanding of those living, just as an unborn fetus cannot understand the nature of the world outside of the womb. The Baháʼí writings state that the soul is immortal and after death it will continue to progress until it finally attains God's presence. In Baháʼí belief, souls in the afterlife will continue to retain their individuality and consciousness and will be able to recognize and communicate spiritually with other souls whom they have made deep profound friendships with, such as their spouses. The Baháʼí scriptures also state there are distinctions between souls in the afterlife, and that souls will recognize the worth of their own deeds and understand the consequences of their actions. It is explained that those souls that have turned toward God will experience gladness, while those who have lived in error will become aware of the opportunities they have lost. Also, in the Baháʼí view, souls will be able to recognize the accomplishments of the souls that have reached the same level as themselves, but not those that have achieved a rank higher than them. Indian religions Buddhism Buddhists maintain that rebirth takes place without an unchanging self or soul passing from one form to another. The type of rebirth will be conditioned by the moral tone of the person's actions (kamma or karma). For example, if a person has committed harmful actions by body, speech and mind based on greed, hate and delusion, would have his/her rebirth in a lower realm, i.e. an animal, a hungry ghost or a hell realm, is to be expected. On the other hand, where a person has performed skillful actions based on generosity, loving-kindness (metta), compassion and wisdom, rebirth in a happy realm, i.e. human or one of the many heavenly realms, can be expected. However, the mechanism of rebirth with Kamma is not deterministic. It depends on various levels of kamma. The most important moment that determines where a person is reborn into is the last thought moment. At that moment, heavy kamma would ripen if there were performed. If not, near death kamma would ripen, and if not death kamma, then habitual kamma would ripen. Finally if none of the above happened, then residual kamma from previous actions can ripen. According to Theravada Buddhism, there are 31 realms of existence that one can be reborn into. Pure Land Buddhism of Mahayana believes in a special place apart from the 31 planes of existence called Pure Land. It is believed that each Buddha has their own pure land, created out of their merits for the sake of sentient beings who recall them mindfully to be able to be reborn in their pure land and train to become a Buddha there. Thus the main practice of pure land Buddhism is to chant a Buddha's name. In Tibetan Buddhism the Tibetan Book of the Dead explains the intermediate state of humans between death and reincarnation. The deceased will find the bright light of wisdom, which shows a straightforward path to move upward and leave the cycle of reincarnation. There are various reasons why the deceased do not follow that light. Some had no briefing about the intermediate state in the former life. Others only used to follow their basic instincts like animals. And some have fear, which results from foul deeds in the former life or from insistent haughtiness. In the intermediate state the awareness is very flexible, so it is important to be virtuous, adopt a positive attitude, and avoid negative ideas. Ideas which are rising from subconsciousness can cause extreme tempers and cowing visions. In this situation they have to understand, that these manifestations are just reflections of the inner thoughts. No one can really hurt them, because they have no more material body. The deceased get help from different Buddhas who show them the path to the bright light. The ones who do not follow the path after all will get hints for a better reincarnation. They have to release the things and beings on which or whom they still hang from the life before. It is recommended to choose a family where the parents trust in the Dharma and to reincarnate with the will to care for the welfare of all beings. "Life is cosmic energy of the universe and after death it merges in universe again and as the time comes to find the suitable place for the entity died in the life condition it gets born. There are 10 life states of any life: Hell, hunger, anger, animality, rapture, humanity, learning, realization, bodhisatva and buddhahood. The life dies in which life condition it reborn in the same life condition." Hinduism There are two major views of afterlife in Hinduism: mythical and philosophical. The philosophies of Hinduism consider each individual consists of 3 bodies: physical body compose of water and bio-matter (sthūla śarīra), an energetic/psychic/mental/subtle body (sūkṣma-śarīra) and a causal body (kāraṇa śarīra) comprising subliminal stuff i.e. mental impressions etc. The individual is a stream of consciousness (Ātman) which flows through all the physical changes of the body and at the death of the physical body, flows on into another physical body. The two components that transmigrate are the subtle body and the causal body. The thought that occupies the mind at the time of death determines the quality of our rebirth (antim smaraṇa), hence Hinduism advises to be mindful of one's thoughts and cultivate positive wholesome thoughts - Mantra chanting (Japa) is commonly practiced for this. The mythical includes the philosophical but adds heaven and hell myths. When one leaves the physical body at death he appears in the court of Lord Yama, the God of Death for an exit interview. The panel consists of Yama and Chitragupta - the cosmic accountant, and Varuna the cosmic intelligence officer. He is counseled about his life, achievements and failures and is shown a mirror in which his entire life is reflected. (Philosophically these three men are projections of one's mind) Yama the Lord of Justice then sends him to a heavenly realm (svarga) if he has been exceptionally benevolent and beneficent for a period of Rest and Recreation. his period is limited in time by the weight of his good deeds. If he has been exceptionally malevolent and caused immense suffering to other beings then he is sent to a cosmic gulag (naraka) for his sins. After one has exhausted his karmas, he takes birth again to continue his spiritual evolution. Rebirth can take place as a god (deva), a human (manuṣya) an animal (tiryak) — but it is generally taught that the spiritual evolution takes place from lower to higher species. In certain cases of traumatic death a person can take the form of a Preta or Hungry Ghost - and remains in an earth-bound state interminably - until certain ceremonies are done to liberate them. This mythological part is extensively elaborated in the Hindu Puranas especially in the Garuda Purana. The Upanishads are the first scriptures in Hinduism which explicitly mention about Afterlife, The Bhagavad Gita, a famous Hindu script, says that just as a man discards his old clothes and wears new ones; similarly the Atman discards the old body and takes on a new one. In Hinduism, the belief is that the body is nothing but a shell, the consciousness inside is immutable and indestructible and takes on different lives in a cycle of birth and death. The end of this cycle is called mukti (Sanskrit: मुक्ति) and staying finally with the ultimate reality forever; is moksha (Sanskrit: मोक्ष) or liberation Jainism Jainism also believes in the afterlife. They believe that the soul takes on a body form based on previous karmas or actions performed by that soul through eternity. Jains believe the soul is eternal and that the freedom from the cycle of reincarnation is the means to attain eternal bliss. Sikhism The essential doctrine of Sikhism is to experience the divine through simple living, meditation and contemplation while being alive. Sikhism also has the belief of being in union with God while living. Accounts of afterlife are considered to be aimed at the popular prevailing views of the time so as to provide a referential framework without necessarily establishing a belief in the afterlife. Thus while it is also acknowledged that living the life of a householder is above the metaphysical truth, Sikhism can be considered agnostic to the question of an afterlife. Some scholars also interpret the mention of reincarnation to be naturalistic akin to the biogeochemical cycles. But if one analyses the Sikh Scriptures carefully, one may find that on many occasions the afterlife and the existence of heaven and hell are mentioned in Guru Granth Sahib and in Dasam Granth, so from that it can be concluded that Sikhism does believe in the existence of heaven and hell; however, heaven and hell are created to temporarily reward and punish, and one will then take birth again until one merges in God. According to the Sikh scriptures, the human form is the closet form to God and the best opportunity for a human being to attain salvation and merge back with God. Sikh Gurus said that nothing dies, nothing is born, everything is ever present, and it just changes forms. Like standing in front of a wardrobe, you pick up a dress and wear it and then you discard it. You wear another one. Thus, in the view of Sikhism, your soul is never born and never dies. Your soul is a part of God and hence lives forever. Others Traditional African religions Traditional African religions are diverse in their beliefs in an afterlife. Hunter-gatherer societies such as the Hadza have no particular belief in an afterlife, and the death of an individual is a straightforward end to their existence. Ancestor cults are found throughout Sub-Saharan Africa, including cultures like the Yombe, Beng, Yoruba and Ewe, "[T]he belief that the dead come back into life and are reborn into their families is given concrete expression in the personal names that are given to children....What is reincarnated are some of the dominant characteristics of the ancestor and not his soul. For each soul remains distinct and each birth represents a new soul." The Yoruba, Dogon and LoDagoa have eschatological ideas similar to Abrahamic religions, "but in most African societies, there is a marked absence of such clear-cut notions of heaven and hell, although there are notions of God judging the soul after death." In some societies like the Mende, multiple beliefs coexist. The Mende believe that people die twice: once during the process of joining the secret society, and again during biological death after which they become ancestors. However, some Mende also believe that after people are created by God they live ten consecutive lives, each in progressively descending worlds. One cross-cultural theme is that the ancestors are part of the world of the living, interacting with it regularly. Shinto It is common for families to participate in ceremonies for children at a shrine, yet have a Buddhist funeral at the time of death. In old Japanese legends, it is often claimed that the dead go to a place called yomi (黄泉), a gloomy underground realm with a river separating the living from the dead mentioned in the legend of Izanami and Izanagi. This yomi very closely resembles the Greek Hades; however, later myths include notions of resurrection and even Elysium-like descriptions such as in the legend of Okuninushi and Susanoo. Shinto tends to hold negative views on death and corpses as a source of pollution called kegare. However, death is also viewed as a path towards apotheosis in Shintoism as can be evidenced by how legendary individuals become enshrined after death. Perhaps the most famous would be Emperor Ojin who was enshrined as Hachiman the God of War after his death. Unitarian Universalism Some Unitarian Universalists believe in universalism: that all souls will ultimately be saved and that there are no torments of hell. Unitarian Universalists differ widely in their theology hence there is no exact same stance on the issue. Although Unitarians historically believed in a literal hell, and Universalists historically believed that everyone goes to heaven, modern Unitarian Universalists can be categorized into those believing in a heaven, reincarnation and oblivion. Most Unitarian Universalists believe that heaven and hell are symbolic places of consciousness and the faith is largely focused on the worldly life rather than any possible afterlife. Spiritualism According to Edgar Cayce, the afterlife consisted of nine realms equated with the nine planets of astrology. The first, symbolized by Saturn, was a level for the purification of the souls. The second, Mercury's realm, gives us the ability to consider problems as a whole. The third of the nine soul realms is ruled by Earth and is associated with the Earthly pleasures. The fourth realm is where we find out about love and is ruled by Venus. The fifth realm is where we meet our limitations and is ruled by Mars. The sixth realm is ruled by Neptune, and is where we begin to use our creative powers and free ourselves from the material world. The seventh realm is symbolized by Jupiter, which strengthens the soul's ability to depict situations, to analyze people and places, things, and conditions. The eighth afterlife realm is ruled by Uranus and develops psychic ability. The ninth afterlife realm is symbolized by Pluto, the astrological realm of the unconscious. This afterlife realm is a transient place where souls can choose to travel to other realms or other solar systems, it is the souls liberation into eternity, and is the realm that opens the doorway from our solar system into the cosmos point of view. Mainstream Spiritualists postulate a series of seven realms that are not unlike Edgar Cayce's nine realms ruled by the planets. As it evolves, the soul moves higher and higher until it reaches the ultimate realm of spiritual oneness. The first realm, equated with hell, is the place where troubled souls spend a long time before they are compelled to move up to the next level. The second realm, where most souls move directly, is thought of as an intermediate transition between the lower planes of life and hell and the higher perfect realms of the universe. The third level is for those who have worked with their karmic inheritance. The fourth level is that from which evolved souls teach and direct those on Earth. The fifth level is where the soul leaves human consciousness behind. At the sixth plane, the soul is finally aligned with the cosmic consciousness and has no sense of separateness or individuality. Finally, the seventh level, the goal of each soul, is where the soul transcends its own sense of "soulfulness" and reunites with the World Soul and the universe. Wicca The Wiccan afterlife is most commonly described as The Summerland. Here, souls rest, recuperate from life, and reflect on the experiences they had during their lives. After a period of rest, the souls are reincarnated, and the memory of their previous lives is erased. Many Wiccans see The Summerland as a place to reflect on their life actions. It is not a place of reward, but rather the end of a life journey at an end point of incarnations. Zoroastrianism Zoroastrianism states that the urvan, the disembodied spirit, lingers on earth for three days before departing downward to the kingdom of the dead that is ruled by Yima. For the three days that it rests on Earth, righteous souls sit at the head of their body, chanting the Ustavaiti Gathas with joy, while a wicked person sits at the feet of the corpse, wails and recites the Yasna. Zoroastrianism states that for the righteous souls, a beautiful maiden, which is the personification of the soul's good thoughts, words and deeds, appears. For a wicked person, a very old, ugly, naked hag appears. After three nights, the soul of the wicked is taken by the demon Vizaresa (Vīzarəša), to Chinvat bridge, and is made to go to darkness (hell). Yima is believed to have been the first king on earth to rule, as well as the first man to die. Inside of Yima's realm, the spirits live a shadowy existence, and are dependent on their own descendants which are still living on Earth. Their descendants are to satisfy their hunger and clothe them, through rituals done on earth. Rituals which are done on the first three days are vital and important, as they protect the soul from evil powers and give it strength to reach the underworld. After three days, the soul crosses Chinvat bridge which is the Final Judgment of the soul. Rashnu and Sraosha are present at the final judgment. The list is expanded sometimes, and include Vahman and Ormazd. Rashnu is the yazata who holds the scales of justice. If the good deeds of the person outweigh the bad, the soul is worthy of paradise. If the bad deeds outweigh the good, the bridge narrows down to the width of a blade-edge, and a horrid hag pulls the soul in her arms, and takes it down to hell with her. Misvan Gatu is the "place of the mixed ones" where the souls lead a gray existence, lacking both joy and sorrow. A soul goes here if his/her good deeds and bad deeds are equal, and Rashnu's scale is equal. Parapsychology The Society for Psychical Research was founded in 1882 with the express intention of investigating phenomena relating to Spiritualism and the afterlife. Its members continue to conduct scientific research on the paranormal to this day. Some of the earliest attempts to apply scientific methods to the study of phenomena relating to an afterlife were conducted by this organization. Its earliest members included noted scientists like William Crookes, and philosophers such as Henry Sidgwick and William James. Parapsychological investigation of the afterlife includes the study of haunting, apparitions of the deceased, instrumental trans-communication, electronic voice phenomena, and mediumship. A study conducted in 1901 by physician Duncan MacDougall sought to measure the weight lost by a human when the soul "departed the body" upon death. MacDougall weighed dying patients in an attempt to prove that the soul was material, tangible and thus measurable. Although MacDougall's results varied considerably from "21 grams", for some people this figure has become synonymous with the measure of a soul's mass. The title of the 2003 movie 21 Grams is a reference to MacDougall's findings. His results have never been reproduced, and are generally regarded either as meaningless or considered to have had little if any scientific merit. Frank Tipler has argued that physics can explain immortality, although such arguments are not falsifiable and, in Karl Popper's views, they do not qualify as science. After 25 years of parapsychological research Susan Blackmore came to the conclusion that, according to her experiences, there is not enough empirical evidence for many of these cases. Mediumship Mediums purportedly act as a vessel for communications from spirits in other realms. Mediumship is not specific to one culture or religion; it can be identified in several belief systems, most notably Spiritualism. While the practice gained popularity in Europe and North America in the 19th century, evidence of mediumship dates back thousands of years in Asia. Mediums who claim to have contact with deceased people include Tyler Henry and Pascal Voggenhuber. Near death research Research also includes the study of the near death experience. Scientists who have worked in this area include Elisabeth Kübler-Ross, Raymond Moody, Sam Parnia, Michael Sabom, Bruce Greyson, Peter Fenwick, Jeffrey Long, Susan Blackmore, Charles Tart, William James, Ian Stevenson, Michael Persinger, Pim van Lommel, Penny Sartori, Walter van Laack among others. Philosophy Modern philosophy There is a view based on the philosophical question of personal identity, termed open individualism by Daniel Kolak, that concludes that individual conscious experience is illusory, and because consciousness continues after death in all conscious beings, you do not die. This position has allegedly been supported by physicists such as Erwin Schrödinger and Freeman Dyson. Certain problems arise with the idea of a particular person continuing after death. Peter van Inwagen, in his argument regarding resurrection, notes that the materialist must have some sort of physical continuity. John Hick also raises questions regarding personal identity in his book, Death and Eternal Life, using an example of a person ceasing to exist in one place while an exact replica appears in another. If the replica had all the same experiences, traits, and physical appearances of the first person, we would all attribute the same identity to the second, according to Hick. Process philosophy In the panentheistic model of process philosophy and theology the writers Alfred North Whitehead and Charles Hartshorne rejected the idea that the universe was made of substance, instead saying reality is composed of living experiences (occasions of experience). According to Hartshorne people do not experience subjective (or personal) immortality in the afterlife, but they do have objective immortality because their experiences live on forever in God, who contains all that was. However other process philosophers such as David Ray Griffin have written that people may have subjective experience after death. Science Psychological proposals for the origin of a belief in an afterlife include cognitive disposition, cultural learning, and as an intuitive religious idea. In one study, children were able to recognize the ending of physical, mental, and perceptual activity in death, but were hesitant to conclude the ending of will, self, or emotion in death. In 2008, a large-scale study conducted by the University of Southampton involving 2060 patients from 15 hospitals in the United Kingdom, United States and Austria was launched. The AWARE (AWAreness during REsuscitation) study examined the broad range of mental experiences in relation to death. In a large study, researchers also tested the validity of conscious experiences for the first time using objective markers, to determine whether claims of awareness compatible with out-of-body experiences correspond with real or hallucinatory events. The results revealed that 40% of those who survived a cardiac arrest were aware during the time that they were clinically dead and before their hearts were restarted. One patient also had a verified out-of-body experience (over 80% of patients did not survive their cardiac arrest or were too sick to be interviewed), but his cardiac arrest occurred in a room without markers. Dr. Parnia in the interview stated, "The evidence thus far suggests that in the first few minutes after death, consciousness is not annihilated." The study continues in AWARE II, which is set to be completed in September 2020. Studies have also been done on the widely reported phenomenon of Near Death Experiences. Experiencers commonly report being transported to a different “realm” or “plane of existence” and they have been shown to display a lasting positive aftereffect on most experiencers. See also Allegory of the long spoons Astral Plane Bardo Brig of Dread (Bridge of Dread) Empiricism Epistemology Eternal oblivion Exaltation (Mormonism) Fate of the unlearned Heaven Rebecca Hensler Hell Immortality Mictlan Mind uploading Nirvana Omega Point Paradise Phowa Pre-existence Purgatory Rebirth Reincarnation Soul Soul retrieval Spiritism Suspended animation Spirit World Undead References Explanatory notes Citations Bibliography Afterlife: A History of Life after Death by Philip C Almond (London and Ithaca NY: I.B. Tauris and Cornell University Press, 2015). Death and Afterlife: Perspectives of World Religions edited by Hiroshi Obayashi, Praeger, 1991. Beyond Death: Theological and Philosophical Reflections on Life after Death edited by Dan Cohn-Sherbok and Christopher Lewis, Pelgrave-MacMillan, 1995. The Islamic Understanding of Death and Resurrection by Jane Idelman Smith and Yazbeck Haddad, Oxford UP, 2002. Life After Death: A History of the Afterlife in Western Religion by Alan F. Segal, Doubleday, 2004. Brain & Belief: An Exploration of the Human Soul by John J. McGraw, Aegis Press, 2004. Beyond the Threshold: Afterlife Beliefs and Experiences in World Religions by Christopher M. Moreman, Rowman & Littlefield, 2008. Is there an afterlife: a comprehensive overview of the evidence by David Fontana, O Books 2005. Death and the Afterlife, by Robert A. Morey. Minneapolis, Minn.: Bethany House Publishers, 1984. 315 p. Conceptions of the Afterlife in Early Civilizations: Universalism, Constructivism and Near-Death Experience by Gregory Shushan, New York & London, Continuum, 2009. . The Myth of an Afterlife: The Case against Life After Death edited by Michael Martin and Keith Augustine, Rowman & Littlefield, 2015. . A Traveler's Guide to the Afterlife: Traditions and Beliefs on Death, Dying, and What Lies Beyond by Mark Mirabello, PhD Inner Traditions. 2016 Conceptions of the Afterlife in Early Civilizations: Universalism, Constructivism, and near-Death Experience by Gregory Shushan, Continuum, 2009. External links Vatican.va: Catechism of the Catholic Church Islamic Guide: Life After Death Judaism 101: Olam Ha-Ba: The Afterlife Stewart Salmond, Christian Doctrine of Immortality Dictionary of the History of Ideas: Death and Immortality (Extensive 1878 text by William Rounseville Alger) Online searchable edition of Swedenborg's Heaven and Hell (Swedenborg Foundation 2000) Collection: Heaven, Hell, and Afterlives from the University of Michigan Museum of Art Life Between Lives Regression Near-death experiences Religious belief and doctrine Philosophy of religion

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1194

https://en.wikipedia.org/wiki/Atomic

Atomic

Atomic may refer to: Of or relating to the atom, the smallest particle of a chemical element that retains its chemical properties Atomic physics, the study of the atom Atomic Age, also known as the "Atomic Era" Atomic scale, distances comparable to the dimensions of an atom Atom (order theory), in mathematics Atomic (cocktail), a champagne cocktail Atomic (magazine), an Australian computing and technology magazine Atomic Skis, an Austrian ski producer Music Atomic (band), a Norwegian jazz quintet Atomic (Lit album), 2001 Atomic (Mogwai album), 2016 Atomic, an album by Rockets, 1982 Atomic (EP), by , 2013 "Atomic" (song), by Blondie, 1979 "Atomic", a song by Tiger Army from Tiger Army III: Ghost Tigers Rise See also Atom (disambiguation) Atomicity (database systems) Nuclear (disambiguation) Atomism, philosophy about the basic building blocks of reality Atomic formula, a formula without subformulas Atomic number, the number of protons found in the nucleus of an atom Atomic chess, a chess variant Atomic coffee machine, a 1950s stovetop coffee machine Atomic operation, in computer science Atomic TV, a channel launched in 1997 in Poland Nuclear power Nuclear weapon

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1196

https://en.wikipedia.org/wiki/Angle

Angle

In Euclidean geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles are also formed by the intersection of two planes. These are called dihedral angles. Two intersecting curves may also define an angle, which is the angle of the rays lying tangent to the respective curves at their point of intersection. Angle is also used to designate the measure of an angle or of a rotation. This measure is the ratio of the length of a circular arc to its radius. In the case of a geometric angle, the arc is centered at the vertex and delimited by the sides. In the case of a rotation, the arc is centered at the center of the rotation and delimited by any other point and its image by the rotation. History and etymology The word angle comes from the Latin word angulus, meaning "corner"; cognate words are the Greek (ankylοs), meaning "crooked, curved," and the English word "ankle". Both are connected with the Proto-Indo-European root *ank-, meaning "to bend" or "bow". Euclid defines a plane angle as the inclination to each other, in a plane, of two lines which meet each other, and do not lie straight with respect to each other. According to Proclus, an angle must be either a quality or a quantity, or a relationship. The first concept was used by Eudemus, who regarded an angle as a deviation from a straight line; the second by Carpus of Antioch, who regarded it as the interval or space between the intersecting lines; Euclid adopted the third concept. Identifying angles In mathematical expressions, it is common to use Greek letters (α, β, γ, θ, φ, . . . ) as variables denoting the size of some angle (to avoid confusion with its other meaning, the symbol is typically not used for this purpose). Lower case Roman letters (a, b, c, . . . ) are also used, as are upper case Roman letters in the context of polygons. See the figures in this article for examples. In geometric figures, angles may also be identified by the labels attached to the three points that define them. For example, the angle at vertex A enclosed by the rays AB and AC (i.e. the lines from point A to point B and point A to point C) is denoted ∠BAC (in Unicode ) or . Where there is no risk of confusion, the angle may sometimes be referred to simply by its vertex (in this case "angle A"). Potentially, an angle denoted as, say, ∠BAC, might refer to any of four angles: the clockwise angle from B to C, the anticlockwise angle from B to C, the clockwise angle from C to B, or the anticlockwise angle from C to B, where the direction in which the angle is measured determines its sign (see Positive and negative angles). However, in many geometrical situations, it is obvious from context that the positive angle less than or equal to 180 degrees is meant, in which case no ambiguity arises. Otherwise, a convention may be adopted so that ∠BAC always refers to the anticlockwise (positive) angle from B to C, and ∠CAB the anticlockwise (positive) angle from C to B. Types of angles Individual angles There is some common terminology for angles, whose measure is always non-negative (see ): An angle equal to 0° or not turned is called a zero angle. An angle smaller than a right angle (less than 90°) is called an acute angle ("acute" meaning "sharp"). An angle equal to  turn (90° or radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or perpendicular. An angle larger than a right angle and smaller than a straight angle (between 90° and 180°) is called an obtuse angle ("obtuse" meaning "blunt"). An angle equal to  turn (180° or radians) is called a straight angle. An angle larger than a straight angle but less than 1 turn (between 180° and 360°) is called a reflex angle. An angle equal to 1 turn (360° or 2 radians) is called a full angle, complete angle, round angle or a perigon. An angle that is not a multiple of a right angle is called an oblique angle. The names, intervals, and measuring units are shown in the table below: Equivalence angle pairs Angles that have the same measure (i.e. the same magnitude) are said to be equal or congruent. An angle is defined by its measure and is not dependent upon the lengths of the sides of the angle (e.g. all right angles are equal in measure). Two angles that share terminal sides, but differ in size by an integer multiple of a turn, are called coterminal angles. A reference angle is the acute version of any angle determined by repeatedly subtracting or adding straight angle ( turn, 180°, or radians), to the results as necessary, until the magnitude of the result is an acute angle, a value between 0 and turn, 90°, or radians. For example, an angle of 30 degrees has a reference angle of 30 degrees, and an angle of 150 degrees also has a reference angle of 30 degrees (180–150). An angle of 750 degrees has a reference angle of 30 degrees (750–720). Vertical and adjacent angle pairs When two straight lines intersect at a point, four angles are formed. Pairwise these angles are named according to their location relative to each other. A pair of angles opposite each other, formed by two intersecting straight lines that form an "X"-like shape, are called vertical angles or opposite angles or vertically opposite angles. They are abbreviated as vert. opp. ∠s. The equality of vertically opposite angles is called the vertical angle theorem. Eudemus of Rhodes attributed the proof to Thales of Miletus. The proposition showed that since both of a pair of vertical angles are supplementary to both of the adjacent angles, the vertical angles are equal in measure. According to a historical note, when Thales visited Egypt, he observed that whenever the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal. Thales concluded that one could prove that all vertical angles are equal if one accepted some general notions such as: All straight angles are equal. Equals added to equals are equal. Equals subtracted from equals are equal. When two adjacent angles form a straight line, they are supplementary. Therefore, if we assume that the measure of angle A equals x, then the measure of angle C would be . Similarly, the measure of angle D would be . Both angle C and angle D have measures equal to and are congruent. Since angle B is supplementary to both angles C and D, either of these angle measures may be used to determine the measure of Angle B. Using the measure of either angle C or angle D, we find the measure of angle B to be . Therefore, both angle A and angle B have measures equal to x and are equal in measure. Adjacent angles, often abbreviated as adj. ∠s, are angles that share a common vertex and edge but do not share any interior points. In other words, they are angles that are side by side, or adjacent, sharing an "arm". Adjacent angles which sum to a right angle, straight angle, or full angle are special and are respectively called complementary, supplementary and explementary angles (see below). A transversal is a line that intersects a pair of (often parallel) lines, and is associated with alternate interior angles, corresponding angles, interior angles, and exterior angles. Combining angle pairs Three special angle pairs involve the summation of angles: Complementary angles are angle pairs whose measures sum to one right angle ( turn, 90°, or radians). If the two complementary angles are adjacent, their non-shared sides form a right angle. In Euclidean geometry, the two acute angles in a right triangle are complementary, because the sum of internal angles of a triangle is 180 degrees, and the right angle itself accounts for 90 degrees. The adjective complementary is from Latin complementum, associated with the verb complere, "to fill up". An acute angle is "filled up" by its complement to form a right angle. The difference between an angle and a right angle is termed the complement of the angle. If angles A and B are complementary, the following relationships hold: (The tangent of an angle equals the cotangent of its complement and its secant equals the cosecant of its complement.) The prefix "co-" in the names of some trigonometric ratios refers to the word "complementary". Two angles that sum to a straight angle ( turn, 180°, or radians) are called supplementary angles. If the two supplementary angles are adjacent (i.e. have a common vertex and share just one side), their non-shared sides form a straight line. Such angles are called a linear pair of angles. However, supplementary angles do not have to be on the same line, and can be separated in space. For example, adjacent angles of a parallelogram are supplementary, and opposite angles of a cyclic quadrilateral (one whose vertices all fall on a single circle) are supplementary. If a point P is exterior to a circle with center O, and if the tangent lines from P touch the circle at points T and Q, then ∠TPQ and ∠TOQ are supplementary. The sines of supplementary angles are equal. Their cosines and tangents (unless undefined) are equal in magnitude but have opposite signs. In Euclidean geometry, any sum of two angles in a triangle is supplementary to the third, because the sum of internal angles of a triangle is a straight angle. Two angles that sum to a complete angle (1 turn, 360°, or 2 radians) are called explementary angles or conjugate angles. The difference between an angle and a complete angle is termed the explement of the angle or conjugate of an angle. Polygon-related angles An angle that is part of a simple polygon is called an interior angle if it lies on the inside of that simple polygon. A simple concave polygon has at least one interior angle that is a reflex angle. In Euclidean geometry, the measures of the interior angles of a triangle add up to radians, 180°, or turn; the measures of the interior angles of a simple convex quadrilateral add up to 2 radians, 360°, or 1 turn. In general, the measures of the interior angles of a simple convex polygon with n sides add up to (n − 2) radians, or (n − 2)180 degrees, (n − 2)2 right angles, or (n − 2) turn. The supplement of an interior angle is called an exterior angle, that is, an interior angle and an exterior angle form a linear pair of angles. There are two exterior angles at each vertex of the polygon, each determined by extending one of the two sides of the polygon that meet at the vertex; these two angles are vertical and hence are equal. An exterior angle measures the amount of rotation one has to make at a vertex to trace out the polygon. If the corresponding interior angle is a reflex angle, the exterior angle should be considered negative. Even in a non-simple polygon it may be possible to define the exterior angle, but one will have to pick an orientation of the plane (or surface) to decide the sign of the exterior angle measure. In Euclidean geometry, the sum of the exterior angles of a simple convex polygon, if only one of the two exterior angles is assumed at each vertex, will be one full turn (360°). The exterior angle here could be called a supplementary exterior angle. Exterior angles are commonly used in Logo Turtle programs when drawing regular polygons. In a triangle, the bisectors of two exterior angles and the bisector of the other interior angle are concurrent (meet at a single point). In a triangle, three intersection points, each of an external angle bisector with the opposite extended side, are collinear. In a triangle, three intersection points, two of them between an interior angle bisector and the opposite side, and the third between the other exterior angle bisector and the opposite side extended, are collinear. Some authors use the name exterior angle of a simple polygon to simply mean the explement exterior angle (not supplement!) of the interior angle. This conflicts with the above usage. Plane-related angles The angle between two planes (such as two adjacent faces of a polyhedron) is called a dihedral angle. It may be defined as the acute angle between two lines normal to the planes. The angle between a plane and an intersecting straight line is equal to ninety degrees minus the angle between the intersecting line and the line that goes through the point of intersection and is normal to the plane. Measuring angles The size of a geometric angle is usually characterized by the magnitude of the smallest rotation that maps one of the rays into the other. Angles that have the same size are said to be equal or congruent or equal in measure. In some contexts, such as identifying a point on a circle or describing the orientation of an object in two dimensions relative to a reference orientation, angles that differ by an exact multiple of a full turn are effectively equivalent. In other contexts, such as identifying a point on a spiral curve or describing the cumulative rotation of an object in two dimensions relative to a reference orientation, angles that differ by a non-zero multiple of a full turn are not equivalent. In order to measure an angle θ, a circular arc centered at the vertex of the angle is drawn, e.g. with a pair of compasses. The ratio of the length s of the arc by the radius r of the circle is the number of radians in the angle. Conventionally, in mathematics and in the SI, the radian is treated as being equal to the dimensionless value 1. The angle expressed another angular unit may then be obtained by multiplying the angle by a suitable conversion constant of the form , where k is the measure of a complete turn expressed in the chosen unit (for example, for degrees or 400 grad for gradians): The value of thus defined is independent of the size of the circle: if the length of the radius is changed then the arc length changes in the same proportion, so the ratio s/r is unaltered. In particular, the measure of angle is radian can be also interpreted as the arc length of its corresponding unit circle: Angle addition postulate The angle addition postulate states that if B is in the interior of angle AOC, then The measure of the angle AOC is the sum of the measure of angle AOB and the measure of angle BOC. Units Throughout history, angles have been measured in various units. These are known as angular units, with the most contemporary units being the degree ( ° ), the radian (rad), and the gradian (grad), though many others have been used throughout history. In the International System of Quantities, angle is defined as a dimensionless quantity. This impacts how angle is treated in dimensional analysis. Most units of angular measurement are defined such that one turn (i.e. one full circle) is equal to n units, for some whole number n. Two exceptions are the radian (and its decimal submultiples) and the diameter part. One radian is the angle subtended by an arc of a circle that has the same length as the circle's radius. The radian is the derived unit of angular measurement in the SI system. By definition, it is dimensionless, though it may be specified as rad to avoid ambiguity. Angles measured in degrees, are shown with the symbol °. Subdivisions of the degree are minute (symbol ′, 1′ = 1/60°) and second (symbol ″, 1″ = 1/3600°). An angle of 360° corresponds to the angle subtended by a full circle, and is equal to radians, or 400 gradians. Other units used to represent angles are listed in the following table. These units are defined such that the number of turns is equivalent to a full circle. Other descriptors Hour angle (n = 24): The astronomical hour angle is  turn. As this system is amenable to measuring objects that cycle once per day (such as the relative position of stars), the sexagesimal subunits are called minute of time and second of time. These are distinct from, and 15 times larger than, minutes and seconds of arc. 1 hour = 15° =  rad =  quad =  turn =  grad. (Compass) point or wind (n = 32): The point, used in navigation, is of a turn. 1 point = of a right angle = 11.25° = 12.5 grad. Each point is subdivided in four quarter-points so that 1 turn equals 128 quarter-points. Pechus (n = 144–180): The pechus was a Babylonian unit equal to about 2° or °. Tau, the number of radians in one turn (1 turn = rad), . Diameter part (n = 376.99...): The diameter part (occasionally used in Islamic mathematics) is radian. One "diameter part" is approximately 0.95493°. There are about 376.991 diameter parts per turn. Milliradian and derived definitions: The true milliradian is defined a thousandth of a radian, which means that a rotation of one turn would equal exactly 2000π mil (or approximately 6283.185 mil), and almost all scope sights for firearms are calibrated to this definition. In addition there are three other derived definitions used for artillery and navigation which are approximately equal to a milliradian. Under these three other definitions one turn makes up for exactly 6000, 6300 or 6400 mils, which equals spanning the range from 0.05625 to 0.06 degrees (3.375 to 3.6 minutes). In comparison, the true milliradian is approximately 0.05729578 degrees (3.43775 minutes). One "NATO mil" is defined as of a circle. Just like with the true milliradian, each of the other definitions exploits the mil's useful property of subtensions, i.e. that the value of one milliradian approximately equals the angle subtended by a width of 1 meter as seen from 1 km away ( = 0.0009817... ≈ ). Akhnam and zam. In old Arabia a turn was subdivided in 32 Akhnam and each akhnam was subdivided in 7 zam, so that a turn is 224 zam. Signed angles Although the definition of the measurement of an angle does not support the concept of a negative angle, it is frequently useful to impose a convention that allows positive and negative angular values to represent orientations and/or rotations in opposite directions relative to some reference. In a two-dimensional Cartesian coordinate system, an angle is typically defined by its two sides, with its vertex at the origin. The initial side is on the positive x-axis, while the other side or terminal side is defined by the measure from the initial side in radians, degrees, or turns. With positive angles representing rotations toward the positive y-axis and negative angles representing rotations toward the negative y-axis. When Cartesian coordinates are represented by standard position, defined by the x-axis rightward and the y-axis upward, positive rotations are anticlockwise and negative rotations are clockwise. In many contexts, an angle of −θ is effectively equivalent to an angle of "one full turn minus θ". For example, an orientation represented as −45° is effectively equivalent to an orientation represented as 360° − 45° or 315°. Although the final position is the same, a physical rotation (movement) of −45° is not the same as a rotation of 315° (for example, the rotation of a person holding a broom resting on a dusty floor would leave visually different traces of swept regions on the floor). In three-dimensional geometry, "clockwise" and "anticlockwise" have no absolute meaning, so the direction of positive and negative angles must be defined relative to some reference, which is typically a vector passing through the angle's vertex and perpendicular to the plane in which the rays of the angle lie. In navigation, bearings or azimuth are measured relative to north. By convention, viewed from above, bearing angles are positive clockwise, so a bearing of 45° corresponds to a north-east orientation. Negative bearings are not used in navigation, so a north-west orientation corresponds to a bearing of 315°. Alternative ways of measuring the size of an angle There are several alternatives to measuring the size of an angle by the angle of rotation. The slope or gradient is equal to the tangent of the angle, or sometimes (rarely) the sine; a gradient is often expressed as a percentage. For very small values (less than 5%), the grade of a slope is approximately the measure of the angle in radians. In rational geometry the spread between two lines is defined as the square of the sine of the angle between the lines. As the sine of an angle and the sine of its supplementary angle are the same, any angle of rotation that maps one of the lines into the other leads to the same value for the spread between the lines. Astronomical approximations Astronomers measure angular separation of objects in degrees from their point of observation. 0.5° is approximately the width of the sun or moon. 1° is approximately the width of a little finger at arm's length. 10° is approximately the width of a closed fist at arm's length. 20° is approximately the width of a handspan at arm's length. These measurements clearly depend on the individual subject, and the above should be treated as rough rule of thumb approximations only. In astronomy, right ascension and declination are usually measured in angular units, expressed in terms of time, based on a 24-hour day. Measurements that are not angular units Not all angle measurements are angular units, for an angular measurement, it is definitional that the angle addition postulate holds. Some angle measurements where the angle addition postulate does not hold include: Trigonometric functions Slope Angles between curves The angle between a line and a curve (mixed angle) or between two intersecting curves (curvilinear angle) is defined to be the angle between the tangents at the point of intersection. Various names (now rarely, if ever, used) have been given to particular cases:—amphicyrtic (Gr. , on both sides, κυρτός, convex) or cissoidal (Gr. κισσός, ivy), biconvex; xystroidal or sistroidal (Gr. ξυστρίς, a tool for scraping), concavo-convex; amphicoelic (Gr. κοίλη, a hollow) or angulus lunularis, biconcave. Bisecting and trisecting angles The ancient Greek mathematicians knew how to bisect an angle (divide it into two angles of equal measure) using only a compass and straightedge, but could only trisect certain angles. In 1837, Pierre Wantzel showed that for most angles this construction cannot be performed. Dot product and generalisations In the Euclidean space, the angle θ between two Euclidean vectors u and v is related to their dot product and their lengths by the formula This formula supplies an easy method to find the angle between two planes (or curved surfaces) from their normal vectors and between skew lines from their vector equations. Inner product To define angles in an abstract real inner product space, we replace the Euclidean dot product ( · ) by the inner product , i.e. In a complex inner product space, the expression for the cosine above may give non-real values, so it is replaced with or, more commonly, using the absolute value, with The latter definition ignores the direction of the vectors and thus describes the angle between one-dimensional subspaces and spanned by the vectors and correspondingly. Angles between subspaces The definition of the angle between one-dimensional subspaces and given by in a Hilbert space can be extended to subspaces of any finite dimensions. Given two subspaces , with , this leads to a definition of angles called canonical or principal angles between subspaces. Angles in Riemannian geometry In Riemannian geometry, the metric tensor is used to define the angle between two tangents. Where U and V are tangent vectors and gij are the components of the metric tensor G, Hyperbolic angle A hyperbolic angle is an argument of a hyperbolic function just as the circular angle is the argument of a circular function. The comparison can be visualized as the size of the openings of a hyperbolic sector and a circular sector since the areas of these sectors correspond to the angle magnitudes in each case. Unlike the circular angle, the hyperbolic angle is unbounded. When the circular and hyperbolic functions are viewed as infinite series in their angle argument, the circular ones are just alternating series forms of the hyperbolic functions. This weaving of the two types of angle and function was explained by Leonhard Euler in Introduction to the Analysis of the Infinite. Angles in geography and astronomy In geography, the location of any point on the Earth can be identified using a geographic coordinate system. This system specifies the latitude and longitude of any location in terms of angles subtended at the center of the Earth, using the equator and (usually) the Greenwich meridian as references. In astronomy, a given point on the celestial sphere (that is, the apparent position of an astronomical object) can be identified using any of several astronomical coordinate systems, where the references vary according to the particular system. Astronomers measure the angular separation of two stars by imagining two lines through the center of the Earth, each intersecting one of the stars. The angle between those lines can be measured and is the angular separation between the two stars. In both geography and astronomy, a sighting direction can be specified in terms of a vertical angle such as altitude /elevation with respect to the horizon as well as the azimuth with respect to north. Astronomers also measure the apparent size of objects as an angular diameter. For example, the full moon has an angular diameter of approximately 0.5°, when viewed from Earth. One could say, "The Moon's diameter subtends an angle of half a degree." The small-angle formula can be used to convert such an angular measurement into a distance/size ratio. See also Angle measuring instrument Angular statistics (mean, standard deviation) Angle bisector Angular acceleration Angular diameter Angular velocity Argument (complex analysis) Astrological aspect Central angle Clock angle problem Decimal degrees Dihedral angle Exterior angle theorem Golden angle Great circle distance Inscribed angle Irrational angle Phase (waves) Protractor Solid angle Spherical angle Transcendent angle Trisection Zenith angle Notes References Bibliography . External links

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1198

https://en.wikipedia.org/wiki/Acoustics

Acoustics

Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries. Hearing is one of the most crucial means of survival in the animal world and speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or marking territories. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's "Wheel of Acoustics" is a well accepted overview of the various fields in acoustics. History Etymology The word "acoustic" is derived from the Greek word ἀκουστικός (akoustikos), meaning "of or for hearing, ready to hear" and that from ἀκουστός (akoustos), "heard, audible", which in turn derives from the verb ἀκούω(akouo), "I hear". The Latin synonym is "sonic", after which the term sonics used to be a synonym for acoustics and later a branch of acoustics. Frequencies above and below the audible range are called "ultrasonic" and "infrasonic", respectively. Early research in acoustics In the 6th century BC, the ancient Greek philosopher Pythagoras wanted to know why some combinations of musical sounds seemed more beautiful than others, and he found answers in terms of numerical ratios representing the harmonic overtone series on a string. He is reputed to have observed that when the lengths of vibrating strings are expressible as ratios of integers (e.g. 2 to 3, 3 to 4), the tones produced will be harmonious, and the smaller the integers the more harmonious the sounds. For example, a string of a certain length would sound particularly harmonious with a string of twice the length (other factors being equal). In modern parlance, if a string sounds the note C when plucked, a string twice as long will sound a C an octave lower. In one system of musical tuning, the tones in between are then given by 16:9 for D, 8:5 for E, 3:2 for F, 4:3 for G, 6:5 for A, and 16:15 for B, in ascending order. Aristotle (384–322 BC) understood that sound consisted of compressions and rarefactions of air which "falls upon and strikes the air which is next to it...", a very good expression of the nature of wave motion. On Things Heard, generally ascribed to Strato of Lampsacus, states that the pitch is related to the frequency of vibrations of the air and to the speed of sound. In about 20 BC, the Roman architect and engineer Vitruvius wrote a treatise on the acoustic properties of theaters including discussion of interference, echoes, and reverberation—the beginnings of architectural acoustics. In Book V of his De architectura (The Ten Books of Architecture) Vitruvius describes sound as a wave comparable to a water wave extended to three dimensions, which, when interrupted by obstructions, would flow back and break up following waves. He described the ascending seats in ancient theaters as designed to prevent this deterioration of sound and also recommended bronze vessels of appropriate sizes be placed in theaters to resonate with the fourth, fifth and so on, up to the double octave, in order to resonate with the more desirable, harmonious notes. During the Islamic golden age, Abū Rayhān al-Bīrūnī (973-1048) is believed to postulated that the speed of sound was much slower than the speed of light. The physical understanding of acoustical processes advanced rapidly during and after the Scientific Revolution. Mainly Galileo Galilei (1564–1642) but also Marin Mersenne (1588–1648), independently, discovered the complete laws of vibrating strings (completing what Pythagoras and Pythagoreans had started 2000 years earlier). Galileo wrote "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound", a remarkable statement that points to the beginnings of physiological and psychological acoustics. Experimental measurements of the speed of sound in air were carried out successfully between 1630 and 1680 by a number of investigators, prominently Mersenne. Meanwhile, Newton (1642–1727) derived the relationship for wave velocity in solids, a cornerstone of physical acoustics (Principia, 1687). Age of Enlightenment and onward Substantial progress in acoustics, resting on firmer mathematical and physical concepts, was made during the eighteenth century by Euler (1707–1783), Lagrange (1736–1813), and d'Alembert (1717–1783). During this era, continuum physics, or field theory, began to receive a definite mathematical structure. The wave equation emerged in a number of contexts, including the propagation of sound in air. In the nineteenth century the major figures of mathematical acoustics were Helmholtz in Germany, who consolidated the field of physiological acoustics, and Lord Rayleigh in England, who combined the previous knowledge with his own copious contributions to the field in his monumental work The Theory of Sound (1877). Also in the 19th century, Wheatstone, Ohm, and Henry developed the analogy between electricity and acoustics. The twentieth century saw a burgeoning of technological applications of the large body of scientific knowledge that was by then in place. The first such application was Sabine's groundbreaking work in architectural acoustics, and many others followed. Underwater acoustics was used for detecting submarines in the first World War. Sound recording and the telephone played important roles in a global transformation of society. Sound measurement and analysis reached new levels of accuracy and sophistication through the use of electronics and computing. The ultrasonic frequency range enabled wholly new kinds of application in medicine and industry. New kinds of transducers (generators and receivers of acoustic energy) were invented and put to use. Fundamental concepts of acoustics Definition Acoustics is defined by ANSI/ASA S1.1-2013 as "(a) Science of sound, including its production, transmission, and effects, including biological and psychological effects. (b) Those qualities of a room that, together, determine its character with respect to auditory effects." The study of acoustics revolves around the generation, propagation and reception of mechanical waves and vibrations. The steps shown in the above diagram can be found in any acoustical event or process. There are many kinds of cause, both natural and volitional. There are many kinds of transduction process that convert energy from some other form into sonic energy, producing a sound wave. There is one fundamental equation that describes sound wave propagation, the acoustic wave equation, but the phenomena that emerge from it are varied and often complex. The wave carries energy throughout the propagating medium. Eventually this energy is transduced again into other forms, in ways that again may be natural and/or volitionally contrived. The final effect may be purely physical or it may reach far into the biological or volitional domains. The five basic steps are found equally well whether we are talking about an earthquake, a submarine using sonar to locate its foe, or a band playing in a rock concert. The central stage in the acoustical process is wave propagation. This falls within the domain of physical acoustics. In fluids, sound propagates primarily as a pressure wave. In solids, mechanical waves can take many forms including longitudinal waves, transverse waves and surface waves. Acoustics looks first at the pressure levels and frequencies in the sound wave and how the wave interacts with the environment. This interaction can be described as either a diffraction, interference or a reflection or a mix of the three. If several media are present, a refraction can also occur. Transduction processes are also of special importance to acoustics. Wave propagation: pressure levels In fluids such as air and water, sound waves propagate as disturbances in the ambient pressure level. While this disturbance is usually small, it is still noticeable to the human ear. The smallest sound that a person can hear, known as the threshold of hearing, is nine orders of magnitude smaller than the ambient pressure. The loudness of these disturbances is related to the sound pressure level (SPL) which is measured on a logarithmic scale in decibels. Wave propagation: frequency Physicists and acoustic engineers tend to discuss sound pressure levels in terms of frequencies, partly because this is how our ears interpret sound. What we experience as "higher pitched" or "lower pitched" sounds are pressure vibrations having a higher or lower number of cycles per second. In a common technique of acoustic measurement, acoustic signals are sampled in time, and then presented in more meaningful forms such as octave bands or time frequency plots. Both of these popular methods are used to analyze sound and better understand the acoustic phenomenon. The entire spectrum can be divided into three sections: audio, ultrasonic, and infrasonic. The audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies can be detected by the human ear. This range has a number of applications, including speech communication and music. The ultrasonic range refers to the very high frequencies: 20,000 Hz and higher. This range has shorter wavelengths which allow better resolution in imaging technologies. Medical applications such as ultrasonography and elastography rely on the ultrasonic frequency range. On the other end of the spectrum, the lowest frequencies are known as the infrasonic range. These frequencies can be used to study geological phenomena such as earthquakes. Analytic instruments such as the spectrum analyzer facilitate visualization and measurement of acoustic signals and their properties. The spectrogram produced by such an instrument is a graphical display of the time varying pressure level and frequency profiles which give a specific acoustic signal its defining character. Transduction in acoustics A transducer is a device for converting one form of energy into another. In an electroacoustic context, this means converting sound energy into electrical energy (or vice versa). Electroacoustic transducers include loudspeakers, microphones, particle velocity sensors, hydrophones and sonar projectors. These devices convert a sound wave to or from an electric signal. The most widely used transduction principles are electromagnetism, electrostatics and piezoelectricity. The transducers in most common loudspeakers (e.g. woofers and tweeters), are electromagnetic devices that generate waves using a suspended diaphragm driven by an electromagnetic voice coil, sending off pressure waves. Electret microphones and condenser microphones employ electrostatics—as the sound wave strikes the microphone's diaphragm, it moves and induces a voltage change. The ultrasonic systems used in medical ultrasonography employ piezoelectric transducers. These are made from special ceramics in which mechanical vibrations and electrical fields are interlinked through a property of the material itself. Acoustician An acoustician is an expert in the science of sound. Education There are many types of acoustician, but they usually have a Bachelor's degree or higher qualification. Some possess a degree in acoustics, while others enter the discipline via studies in fields such as physics or engineering. Much work in acoustics requires a good grounding in Mathematics and science. Many acoustic scientists work in research and development. Some conduct basic research to advance our knowledge of the perception (e.g. hearing, psychoacoustics or neurophysiology) of speech, music and noise. Other acoustic scientists advance understanding of how sound is affected as it moves through environments, e.g. underwater acoustics, architectural acoustics or structural acoustics. Other areas of work are listed under subdisciplines below. Acoustic scientists work in government, university and private industry laboratories. Many go on to work in Acoustical Engineering. Some positions, such as Faculty (academic staff) require a Doctor of Philosophy. Subdisciplines Archaeoacoustics Archaeoacoustics, also known as the archaeology of sound, is one of the only ways to experience the past with senses other than our eyes. Archaeoacoustics is studied by testing the acoustic properties of prehistoric sites, including caves. Iegor Rezkinoff, a sound archaeologist, studies the acoustic properties of caves through natural sounds like humming and whistling. Archaeological theories of acoustics are focused around ritualistic purposes as well as a way of echolocation in the caves. In archaeology, acoustic sounds and rituals directly correlate as specific sounds were meant to bring ritual participants closer to a spiritual awakening. Parallels can also be drawn between cave wall paintings and the acoustic properties of the cave; they are both dynamic. Because archaeoacoustics is a fairly new archaeological subject, acoustic sound is still being tested in these prehistoric sites today. Aeroacoustics Aeroacoustics is the study of noise generated by air movement, for instance via turbulence, and the movement of sound through the fluid air. This knowledge is applied in acoustical engineering to study how to quieten aircraft. Aeroacoustics is important for understanding how wind musical instruments work. Acoustic signal processing Acoustic signal processing is the electronic manipulation of acoustic signals. Applications include: active noise control; design for hearing aids or cochlear implants; echo cancellation; music information retrieval, and perceptual coding (e.g. MP3 or Opus). Architectural acoustics Architectural acoustics (also known as building acoustics) involves the scientific understanding of how to achieve good sound within a building. It typically involves the study of speech intelligibility, speech privacy, music quality, and vibration reduction in the built environment. Commonly studied environments are hospitals, classrooms, dwellings, performance venues, recording and broadcasting studios. Focus considerations include room acoustics, airborne and impact transmission in building structures, airborne and structure-borne noise control, noise control of building systems and electroacoustic systems . Bioacoustics Bioacoustics is the scientific study of the hearing and calls of animal calls, as well as how animals are affected by the acoustic and sounds of their habitat. Electroacoustics This subdiscipline is concerned with the recording, manipulation and reproduction of audio using electronics. This might include products such as mobile phones, large scale public address systems or virtual reality systems in research laboratories. Environmental noise and soundscapes Environmental acoustics is concerned with noise and vibration caused by railways, road traffic, aircraft, industrial equipment and recreational activities. The main aim of these studies is to reduce levels of environmental noise and vibration. Research work now also has a focus on the positive use of sound in urban environments: soundscapes and tranquility. Musical acoustics Musical acoustics is the study of the physics of acoustic instruments; the audio signal processing used in electronic music; the computer analysis of music and composition, and the perception and cognitive neuroscience of music. Noise The goal this acoustics sub-discipline is to reduce the impact of unwanted sound. Scope of noise studies includes the generation, propagation, and impact on structures, objects, and people. Innovative model development Measurement techniques Mitigation strategies Inupt to the establishment of standards and regulations Noise research investigates the impact of noise on humans and animals to include work in definitions, abatement, transportation noise, hearing protection, Jet and rocket noise, building system noise and vibration, atmospheric sound propagation, soundscapes, and low-frequency sound. Psychoacoustics Many studies have been conducted to identify the relationship between acoustics and cognition, or more commonly known as psychoacoustics, in which what one hears is a combination of perception and biological aspects. The information intercepted by the passage of sound waves through the ear is understood and interpreted through the brain, emphasizing the connection between the mind and acoustics. Psychological changes have been seen as brain waves slow down or speed up as a result of varying auditory stimulus which can in turn affect the way one thinks, feels, or even behaves. This correlation can be viewed in normal, everyday situations in which listening to an upbeat or uptempo song can cause one's foot to start tapping or a slower song can leave one feeling calm and serene. In a deeper biological look at the phenomenon of psychoacoustics, it was discovered that the central nervous system is activated by basic acoustical characteristics of music. By observing how the central nervous system, which includes the brain and spine, is influenced by acoustics, the pathway in which acoustic affects the mind, and essentially the body, is evident. Speech Acousticians study the production, processing and perception of speech. Speech recognition and Speech synthesis are two important areas of speech processing using computers. The subject also overlaps with the disciplines of physics, physiology, psychology, and linguistics. Structural Vibration and Dynamics Structural acoustics is the study of motions and interactions of mechanical systems with their environments and the methods of their measurement, analysis, and control . There are several sub-disciplines found within this regime: Modal Analysis Material characterization Structural health monitoring Acoustic Metamaterials Friction Acoustics Applications might include: ground vibrations from railways; vibration isolation to reduce vibration in operating theatres; studying how vibration can damage health (vibration white finger); vibration control to protect a building from earthquakes, or measuring how structure-borne sound moves through buildings. Ultrasonics Ultrasonics deals with sounds at frequencies too high to be heard by humans. Specialisms include medical ultrasonics (including medical ultrasonography), sonochemistry, ultrasonic testing, material characterisation and underwater acoustics (sonar). Underwater acoustics Underwater acoustics is the scientific study of natural and man-made sounds underwater. Applications include sonar to locate submarines, underwater communication by whales, climate change monitoring by measuring sea temperatures acoustically, sonic weapons, and marine bioacoustics. Professional societies The Acoustical Society of America (ASA) Australian Acoustical Society (AAS) The European Acoustics Association (EAA) Institute of Electrical and Electronics Engineers (IEEE) Institute of Acoustics (IoA UK) The Audio Engineering Society (AES) American Society of Mechanical Engineers, Noise Control and Acoustics Division (ASME-NCAD) International Commission for Acoustics (ICA) American Institute of Aeronautics and Astronautics, Aeroacoustics (AIAA) International Computer Music Association (ICMA) Academic journals Acta Acustica united with Acustica Applied Acoustics Journal of the Acoustical Society of America (JASA) Journal of the Acoustical Society of America, Express Letters (JASA-EL) Journal of the Audio Engineering Society Journal of Sound and Vibration (JSV) Journal of Vibration and Acoustics American Society of Mechanical Engineers Ultrasonics (journal) See also Outline of acoustics Acoustic attenuation Acoustic emission Acoustic engineering Acoustic impedance Acoustic levitation Acoustic location Acoustic phonetics Acoustic streaming Acoustic tags Acoustic thermometry Acoustic wave Audiology Auditory illusion Diffraction Doppler effect Fisheries acoustics Friction acoustics Helioseismology Lamb wave Linear elasticity The Little Red Book of Acoustics (in the UK) Longitudinal wave Musicology Music therapy Noise pollution One-Way Wave Equation Phonon Picosecond ultrasonics Rayleigh wave Shock wave Seismology Sonification Sonochemistry Soundproofing Soundscape Sonic boom Sonoluminescence Surface acoustic wave Thermoacoustics Transverse wave Wave equation References Further reading (Volume 4 is available from the Internet Archive ) Mason W.P., Thurston R.N. Physical Acoustics (1981) Philip M. Morse and K. Uno Ingard, 1986. Theoretical Acoustics (Princeton University Press). Allan D. Pierce, 1989. Acoustics: An Introduction to its Physical Principles and Applications (Acoustical Society of America). D. R. Raichel, 2006. The Science and Applications of Acoustics, second edition (Springer). E. Skudrzyk, 1971. The Foundations of Acoustics: Basic Mathematics and Basic Acoustics (Springer). External links International Commission for Acoustics European Acoustics Association Acoustical Society of America Institute of Noise Control Engineers National Council of Acoustical Consultants Institute of Acoustic in UK Australian Acoustical Society (AAS) Sound

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1200

https://en.wikipedia.org/wiki/Atomic%20physics

Atomic physics

Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned with the way in which electrons are arranged around the nucleus and the processes by which these arrangements change. This comprises ions, neutral atoms and, unless otherwise stated, it can be assumed that the term atom includes ions. The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics—which deals with the atom as a system consisting of a nucleus and electrons—and nuclear physics, which studies nuclear reactions and special properties of atomic nuclei. As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular, and optical physics. Physics research groups are usually so classified. Isolated atoms Atomic physics primarily considers atoms in isolation. Atomic models will consist of a single nucleus that may be surrounded by one or more bound electrons. It is not concerned with the formation of molecules (although much of the physics is identical), nor does it examine atoms in a solid state as condensed matter. It is concerned with processes such as ionization and excitation by photons or collisions with atomic particles. While modelling atoms in isolation may not seem realistic, if one considers atoms in a gas or plasma then the time-scales for atom-atom interactions are huge in comparison to the atomic processes that are generally considered. This means that the individual atoms can be treated as if each were in isolation, as the vast majority of the time they are. By this consideration atomic physics provides the underlying theory in plasma physics and atmospheric physics, even though both deal with very large numbers of atoms. Electronic configuration Electrons form notional shells around the nucleus. These are normally in a ground state but can be excited by the absorption of energy from light (photons), magnetic fields, or interaction with a colliding particle (typically ions or other electrons). Electrons that populate a shell are said to be in a bound state. The energy necessary to remove an electron from its shell (taking it to infinity) is called the binding energy. Any quantity of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the conservation of energy. The atom is said to have undergone the process of ionization. If the electron absorbs a quantity of energy less than the binding energy, it will be transferred to an excited state. After a certain time, the electron in an excited state will "jump" (undergo a transition) to a lower state. In a neutral atom, the system will emit a photon of the difference in energy, since energy is conserved. If an inner electron has absorbed more than the binding energy (so that the atom ionizes), then a more outer electron may undergo a transition to fill the inner orbital. In this case, a visible photon or a characteristic x-ray is emitted, or a phenomenon known as the Auger effect may take place, where the released energy is transferred to another bound electron, causing it to go into the continuum. The Auger effect allows one to multiply ionize an atom with a single photon. There are rather strict selection rules as to the electronic configurations that can be reached by excitation by light — however there are no such rules for excitation by collision processes. History and developments One of the earliest steps towards atomic physics was the recognition that matter was composed of atoms. It forms a part of the texts written in 6th century BC to 2nd century BC such as those of Democritus or Vaisheshika Sutra written by Kanad. This theory was later developed in the modern sense of the basic unit of a chemical element by the British chemist and physicist John Dalton in the 18th century. At this stage, it wasn't clear what atoms were although they could be described and classified by their properties (in bulk). The invention of the periodic system of elements by Mendeleev was another great step forward. The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon, most notably by Joseph von Fraunhofer. The study of these lines led to the Bohr atom model and to the birth of quantum mechanics. In seeking to explain atomic spectra an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells were concerned, not only did this yield a better overall description, i.e. the atomic orbital model, but it also provided a new theoretical basis for chemistry (quantum chemistry) and spectroscopy. Since the Second World War, both theoretical and experimental fields have advanced at a rapid pace. This can be attributed to progress in computing technology, which has allowed larger and more sophisticated models of atomic structure and associated collision processes. Similar technological advances in accelerators, detectors, magnetic field generation and lasers have greatly assisted experimental work. Significant atomic physicists See also Particle physics Isomeric shift Atomic engineering Bibliography References External links MIT-Harvard Center for Ultracold Atoms Joint Quantum Institute at University of Maryland and NIST Atomic Physics on the Internet JILA (Atomic Physics) ORNL Physics Division Atomic, molecular, and optical physics

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1202

https://en.wikipedia.org/wiki/Applet

Applet

In computing, an applet is any small application that performs one specific task that runs within the scope of a dedicated widget engine or a larger program, often as a plug-in. The term is frequently used to refer to a Java applet, a program written in the Java programming language that is designed to be placed on a web page. Applets are typical examples of transient and auxiliary applications that don't monopolize the user's attention. Applets are not full-featured application programs, and are intended to be easily accessible. History The word applet was first used in 1990 in PC Magazine. However, the concept of an applet, or more broadly a small interpreted program downloaded and executed by the user, dates at least to RFC 5 (1969) by Jeff Rulifson, which described the Decode-Encode Language (DEL), which was designed to allow remote use of the oN-Line System (NLS) over ARPANET, by downloading small programs to enhance the interaction. This has been specifically credited as a forerunner of Java's downloadable programs in RFC 2555. Applet as an extension of other software In some cases, an applet does not run independently. These applets must run either in a container provided by a host program, through a plugin, or a variety of other applications including mobile devices that support the applet programming model. Web-based Applets Applets were used to provide interactive features to web applications that historically could not be provided by HTML alone. They could capture mouse input and also had controls like buttons or check boxes. In response to the user action an applet could change the provided graphic content. This made applets well suitable for demonstration, visualization, and teaching. There were online applet collections for studying various subjects, from physics to heart physiology. Applets were also used to create online game collections that allowed players to compete against live opponents in real-time. An applet could also be a text area only, providing, for instance, a cross platform command-line interface to some remote system. If needed, an applet could leave the dedicated area and run as a separate window. However, applets had very little control over web page content outside the applet dedicated area, so they were less useful for improving the site appearance in general (while applets like news tickers or WYSIWYG editors are also known). Applets could also play media in formats that are not natively supported by the browser. HTML pages could embed parameters that were passed to the applet. Hence the same applet could appear differently depending on the parameters that were passed. Examples of Web-based Applets include: QuickTime movies Flash movies Windows Media Player applets, used to display embedded video files in Internet Explorer (and other browsers that supported the plugin) 3D modeling display applets, used to rotate and zoom a model Browser games that were applet-based, though some developed into fully functional applications that required installation. Applet Vs. Subroutine A larger application distinguishes its applets through several features: Applets execute only on the "client" platform environment of a system, as contrasted from "servlet". As such, an applet provides functionality or performance beyond the default capabilities of its container (the browser). The container restricts applets' capabilities. Applets are written in a language different from the scripting or HTML language that invokes it. The applet is written in a compiled language, whereas the scripting language of the container is an interpreted language, hence the greater performance or functionality of the applet. Unlike a subroutine, a complete web component can be implemented as an applet. Java applets A Java applet is a Java program that is launched from HTML and run in a web browser.It takes code from server and run in a web browser.It can provide web applications with interactive features that cannot be provided by HTML. Since Java's bytecode is platform-independent, Java applets can be executed by browsers running under many platforms, including Windows, Unix, macOS, and Linux. When a Java technology-enabled web browser processes a page that contains an applet, the applet's code is transferred to the client's system and executed by the browser's Java Virtual Machine (JVM). An HTML page references an applet either via the deprecated tag or via its replacement, the tag. Security Recent developments in the coding of applications including mobile and embedded systems have led to the awareness of the security of applets. Open platform applets Applets in an open platform environment should provide secure interactions between different applications. A compositional approach can be used to provide security for open platform applets. Advanced compositional verification methods have been developed for secure applet interactions. Java applets A Java applet contains different security models: unsigned Java applet security, signed Java applet security, and self signed Java applet security. Web-based applets In an applet-enabled web browser, many methods can be used to provide applet security for malicious applets. A malicious applet can infect a computer system in many ways, including denial of service, invasion of privacy, and annoyance. A typical solution for malicious applets is to make the web browser to monitor applets' activities. This will result in a web browser that will enable the manual or automatic stopping of malicious applets. See also Application posture Bookmarklet Java applet Widget engine Abstract Window Toolkit References External links Technology neologisms Component-based software engineering Java (programming language) libraries

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1203

https://en.wikipedia.org/wiki/Alternate%20history

Alternate history

Alternate history (also alternative history, althist, AH) is a genre of speculative fiction of stories in which one or more historical events occur and are resolved differently than in real life. As conjecture based upon historical fact, alternative history stories propose What if? scenarios about crucial events in human history, and present outcomes very different from the historical record. Alternate history also is a subgenre of literary fiction, science fiction, and historical fiction; as literature, alternate history uses the tropes of the genre to answer the What if? speculations of the story. Since the 1950s, as a subgenre of science fiction, alternative history stories feature the tropes of time travel between histories, and the psychic awareness of the existence of an alternative universe, by the inhabitants of a given universe; and time travel that divides history into various timestreams. In the Spanish, French, German, and Portuguese, Italian, Catalan, and Galician languages, the terms Uchronie, ucronia, ucronía, and Uchronie identify the alternate history genre, from which derives the English term Uchronia, composed of the Greek prefix ("not", "not any", and "no") and the Greek word () "time", to describe a story that occurs "[in] no time"; analogous to a story that occurs in utopia, "[in] no place". The term Uchronia also is the name of the list of alternate-history books, uchronia.net. Moreover, Allohistory (other history) is another term for the genre of alternative history. Definition Alternative history is a genre of fiction wherein the author speculates upon how the course of history might have been altered if a particular historical event had an outcome different from the real life outcome. An alternate history requires three conditions: (i) A point of divergence from the historical record, before the time in which the author is writing; (ii) A change that would alter known history; and (iii) An examination of the ramifications of that alteration to history. Occasionally, some types of genre fiction are misidentified as alternative history, specifically science fiction stories set in a time that was the future for the writer, but now is the past for the reader, such as the novels 2001: A Space Odyssey (1968), by Arthur C. Clarke and Nineteen Eighty-Four (1949), by George Orwell, because the authors did not alter the history of the past when they wrote the stories. Moreover, the genre of the Secret History of an event, which can be either fictional or non-fictional, documents events that might have occurred in history, but which had no effect upon the recorded historical outcome. Alternative history also is thematically related to, but distinct from, Counterfactual History, which is a form of historiography that attempts to answer the What if? speculations that arise from counterfactual conditions in order to understand what did happen. As a method of historical research, counterfactual history explores historical events with an extrapolated timeline in which key historical events either did not occur or had an outcome different from the historical record. History of literature Antiquity and medieval The earliest example of alternate (or counterfactual) history is found in Livy's Ab Urbe Condita Libri (book IX, sections 17–19). Livy contemplated an alternative 4th century BC in which Alexander the Great had survived to attack Europe as he had planned; asking, "What would have been the results for Rome if she had been engaged in a war with Alexander?" Livy concluded that the Romans would likely have defeated Alexander. An even earlier possibility is Herodotus's Histories, which contains speculative material. Another example of counterfactual history was posited by cardinal and Doctor of the Church Peter Damian in the 11th century. In his famous work De Divina Omnipotentia, a long letter in which he discusses God's omnipotence, he treats questions related to the limits of divine power, including the question of whether God can change the past, for example, bringing about that Rome was never founded:I see I must respond finally to what many people, on the basis of your holiness’s [own] judgment, raise as an objection on the topic of this dispute. For they say: If, as you assert, God is omnipotent in all things, can he manage this, that things that have been made were not made? He can certainly destroy all things that have been made, so that they do not exist now. But it cannot be seen how he can bring it about that things that have been made were not made. To be sure, it can come about that from now on and hereafter Rome does not exist; for it can be destroyed. But no opinion can grasp how it can come about that it was not founded long ago...One early work of fiction detailing an alternate history is Joanot Martorell's 1490 epic romance Tirant lo Blanch, which was written when the loss of Constantinople to the Turks was still a recent and traumatic memory for Christian Europe. It tells the story of the knight Tirant the White from Brittany who travels to the embattled remnants of the Byzantine Empire. He becomes a Megaduke and commander of its armies and manages to fight off the invading Ottoman armies of . He saves the city from Islamic conquest, and even chases the Turks deeper into lands they had previously conquered. 19th century One of the earliest works of alternate history published in large quantities for the reception of a large audience may be Louis Geoffroy's Histoire de la Monarchie universelle: Napoléon et la conquête du monde (1812–1832) (History of the Universal Monarchy: Napoleon and the Conquest of the World) (1836), which imagines Napoleon's First French Empire emerging victorious in the French invasion of Russia in 1812 and in an invasion of England in 1814, later unifying the world under Bonaparte's rule. In the English language, the first known complete alternate history is Nathaniel Hawthorne's short story "P.'s Correspondence", published in 1845. It recounts the tale of a man who is considered "a madman" due to his perceptions of a different 1845, a reality in which long-dead famous people, such as the poets Robert Burns, Lord Byron, Percy Bysshe Shelley and John Keats, the actor Edmund Kean, the British politician George Canning, and Napoleon Bonaparte, are still alive. The first novel-length alternate history in English would seem to be Castello Holford's Aristopia (1895). While not as nationalistic as Louis Geoffroy's Napoléon et la conquête du monde, 1812–1823, Aristopia is another attempt to portray a Utopian society. In Aristopia, the earliest settlers in Virginia discover a reef made of solid gold and are able to build a Utopian society in North America. Early 20th century and the era of the pulps In 1905, H. G. Wells published A Modern Utopia. As explicitly noted in the book itself, Wells's main aim in writing it was to set out his social and political ideas, the plot serving mainly as a vehicle to expound them. This book introduced the idea of a person being transported from a point in our familiar world to the precise geographical equivalent point in an alternate world in which history had gone differently. The protagonists undergo various adventures in the alternate world, and then are finally transported back to our world, again to the precise geographical equivalent point. Since then, that has become a staple of the alternate history genre. A number of alternate history stories and novels appeared in the late 19th and early 20th centuries (see, for example, Joseph Edgar Chamberlin's The Ifs of History [1907] and Charles Petrie's If: A Jacobite Fantasy [1926]). In 1931, British historian Sir John Squire collected a series of essays from some of the leading historians of the period for his anthology If It Had Happened Otherwise. In that work, scholars from major universities, as well as important non-academic authors, turned their attention to such questions as "If the Moors in Spain Had Won" and "If Louis XVI Had Had an Atom of Firmness". The essays range from serious scholarly efforts to Hendrik Willem van Loon's fanciful and satiric portrayal of an independent 20th-century New Amsterdam, a Dutch city-state on the island of Manhattan. Among the authors included were Hilaire Belloc, André Maurois, and Winston Churchill. One of the entries in Squire's volume was Churchill's "If Lee Had Not Won the Battle of Gettysburg", written from the viewpoint of a historian in a world in which the Confederacy had won the American Civil War. The entry considers what would have happened if the North had been victorious (in other words, a character from an alternate world imagines a world more like the real one we live in, although it is not identical in every detail). Speculative work that narrates from the point of view of an alternate history is variously known as "recursive alternate history", a "double-blind what-if", or an "alternate-alternate history". Churchill's essay was one of the influences behind Ward Moore's alternate history novel Bring the Jubilee in which General Robert E. Lee won the Battle of Gettysburg and paved the way for the eventual victory of the Confederacy in the American Civil War (named the "War of Southron Independence" in this timeline). The protagonist, the autodidact Hodgins Backmaker, travels back to the aforementioned battle and inadvertently changes history, which results in the emergence of our own timeline and the consequent victory of the Union instead. The American humorist author James Thurber parodied alternate history stories about the American Civil War in his 1930 story "If Grant Had Been Drinking at Appomattox", which he accompanied with this very brief introduction: "Scribner's magazine is publishing a series of three articles: 'If Booth Had Missed Lincoln', 'If Lee Had Won the Battle of Gettysburg', and 'If Napoleon Had Escaped to America'. This is the fourth". Another example of alternate history from this period (and arguably the first that explicitly posited cross-time travel from one universe to another as anything more than a visionary experience) is H.G. Wells' Men Like Gods (1923) in which the London-based journalist Mr. Barnstable, along with two cars and their passengers, is mysteriously teleported into "another world", which the "Earthlings" call Utopia. Being far more advanced than Earth, Utopia is some 3000 years ahead of humanity in its development. Wells describes a multiverse of alternative worlds, complete with the paratime travel machines that would later become popular with American pulp writers. However, since his hero experiences only a single alternate world, the story is not very different from conventional alternate history. In the 1930s, alternate history moved into a new arena. The December 1933 issue of Astounding published Nat Schachner's "Ancestral Voices", which was quickly followed by Murray Leinster's "Sidewise in Time". While earlier alternate histories examined reasonably-straightforward divergences, Leinster attempted something completely different. In his "World gone mad", pieces of Earth traded places with their analogs from different timelines. The story follows Professor Minott and his students from a fictitious Robinson College as they wander through analogues of worlds that followed a different history. A somewhat similar approach was taken by Robert A. Heinlein in his 1941 novelette Elsewhen in which a professor trains his mind to move his body across timelines. He then hypnotizes his students so that they can explore more of them. Eventually, each settles into the reality that is most suitable for him or her. Some of the worlds they visit are mundane, some are very odd, and others follow science fiction or fantasy conventions. World War II produced alternate history for propaganda: both British and American authors wrote works depicting Nazi invasions of their respective countries as cautionary tales. Time travel to create historical divergences The period around World War II also saw the publication of the time travel novel Lest Darkness Fall by L. Sprague de Camp in which an American academic travels to Italy at the time of the Byzantine invasion of the Ostrogoths. De Camp's time traveler, Martin Padway, is depicted as making permanent historical changes and implicitly forming a new time branch, thereby making the work an alternate history. In William Tenn's short story Brooklyn Project (1948), a tyrannical US Government brushes aside the warnings of scientists about the dangers of time travel and goes on with a planned experiment - with the result that minor changes to the prehistoric past cause Humanity to never have existed, its place taken by tentacled underwater intelligent creatures - who also have a tyrannical government which also insists on experimenting with time-travel. Time travel as the cause of a point of divergence (POD), which can denote either the bifurcation of a historical timeline or a simple replacement of the future that existed before the time-travelling event, has continued to be a popular theme. In Ward Moore's Bring the Jubilee, the protagonist lives in an alternate history in which the Confederacy has won the American Civil War. He travels backward through time and brings about a Union victory at the Battle of Gettysburg. When a story's assumptions about the nature of time travel lead to the complete replacement of the visited time's future, rather than just the creation of an additional time line, the device of a "time patrol" is often used where guardians move through time to preserve the "correct" history. A more recent example is Making History by Stephen Fry in which a time machine is used to alter history so that Adolf Hitler was never born. That ironically results in a more competent leader of Nazi Germany and results in the country's ascendancy and longevity in the altered timeline. Cross-time stories H.G. Wells' "cross-time" or "many universes" variant (see above) was fully developed by Murray Leinster in his 1934 short story "Sidewise in Time", in which sections of the Earth's surface begin changing places with their counterparts in alternate timelines. Fredric Brown employed this subgenre to satirize the science fiction pulps and their adolescent readers—and fears of foreign invasion—in the classic What Mad Universe (1949). In Clifford D. Simak's Ring Around the Sun (1953), the hero ends up in an alternate earth of thick forests in which humanity never developed but a band of mutants is establishing a colony; the story line appears to frame the author's anxieties regarding McCarthyism and the Cold War. Quantum theory of many worlds While many justifications for alternate histories involve a multiverse, the "many world" theory would naturally involve many worlds, in fact a continually exploding array of universes. In quantum theory, new worlds would proliferate with every quantum event, and even if the writer uses human decisions, every decision that could be made differently would result in a different timeline. A writer's fictional multiverse may, in fact, preclude some decisions as humanly impossible, as when, in Night Watch, Terry Pratchett depicts a character informing Vimes that while anything that can happen, has happened, nevertheless there is no history whatsoever in which Vimes has ever murdered his wife. When the writer explicitly maintains that all possible decisions are made in all possible ways, one possible conclusion is that the characters were neither brave, nor clever, nor skilled, but simply lucky enough to happen on the universe in which they did not choose the cowardly route, take the stupid action, fumble the crucial activity, etc.; few writers focus on this idea, although it has been explored in stories such as Larry Niven's story All the Myriad Ways, where the reality of all possible universes leads to an epidemic of suicide and crime because people conclude their choices have no moral import. In any case, even if it is true that every possible outcome occurs in some world, it can still be argued that traits such as bravery and intelligence might still affect the relative frequency of worlds in which better or worse outcomes occurred (even if the total number of worlds with each type of outcome is infinite, it is still possible to assign a different measure to different infinite sets). The physicist David Deutsch, a strong advocate of the many-worlds interpretation of quantum mechanics, has argued along these lines, saying that "By making good choices, doing the right thing, we thicken the stack of universes in which versions of us live reasonable lives. When you succeed, all the copies of you who made the same decision succeed too. What you do for the better increases the portion of the multiverse where good things happen." This view is perhaps somewhat too abstract to be explored directly in science fiction stories, but a few writers have tried, such as Greg Egan in his short story The Infinite Assassin, where an agent is trying to contain reality-scrambling "whirlpools" that form around users of a certain drug, and the agent is constantly trying to maximize the consistency of behavior among his alternate selves, attempting to compensate for events and thoughts he experiences, he guesses are of low measure relative to those experienced by most of his other selves. Many writers—perhaps the majority—avoid the discussion entirely. In one novel of this type, H. Beam Piper's Lord Kalvan of Otherwhen, a Pennsylvania State Police officer, who knows how to make gunpowder, is transported from our world to an alternate universe where the recipe for gunpowder is a tightly held secret and saves a country that is about to be conquered by its neighbors. The paratime patrol members are warned against going into the timelines immediately surrounding it, where the country will be overrun, but the book never depicts the slaughter of the innocent thus entailed, remaining solely in the timeline where the country is saved. The cross-time theme was further developed in the 1960s by Keith Laumer in the first three volumes of his Imperium sequence, which would be completed in Zone Yellow (1990). Piper's politically more sophisticated variant was adopted and adapted by Michael Kurland and Jack Chalker in the 1980s; Chalker's G.O.D. Inc trilogy (1987–89), featuring paratime detectives Sam and Brandy Horowitz, marks the first attempt at merging the paratime thriller with the police procedural. Kurland's Perchance (1988), the first volume of the never-completed "Chronicles of Elsewhen", presents a multiverse of secretive cross-time societies that utilize a variety of means for cross-time travel, ranging from high-tech capsules to mutant powers. Harry Turtledove has launched the Crosstime Traffic series for teenagers featuring a variant of H. Beam Piper's paratime trading empire. Rival paratime worlds The concept of a cross-time version of a world war, involving rival paratime empires, was developed in Fritz Leiber's Change War series, starting with the Hugo Award winning The Big Time (1958); followed by Richard C. Meredith's Timeliner trilogy in the 1970s, Michael McCollum's A Greater Infinity (1982) and John Barnes' Timeline Wars trilogy in the 1990s. Such "paratime" stories may include speculation that the laws of nature can vary from one universe to the next, providing a science fictional explanation—or veneer—for what is normally fantasy. Aaron Allston's Doc Sidhe and Sidhe Devil take place between our world, the "grim world" and an alternate "fair world" where the Sidhe retreated to. Although technology is clearly present in both worlds, and the "fair world" parallels our history, about fifty years out of step, there is functional magic in the fair world. Even with such explanation, the more explicitly the alternate world resembles a normal fantasy world, the more likely the story is to be labelled fantasy, as in Poul Anderson's "House Rule" and "Loser's Night". In both science fiction and fantasy, whether a given parallel universe is an alternate history may not be clear. The writer might allude to a POD only to explain the existence and make no use of the concept, or may present the universe without explanation of its existence. Major writers explore alternate histories Isaac Asimov's short story "What If—" (1952) is about a couple who can explore alternate realities by means of a television-like device. This idea can also be found in Asimov's novel The End of Eternity (1955), in which the "Eternals" can change the realities of the world, without people being aware of it. Poul Anderson's Time Patrol stories feature conflicts between forces intent on changing history and the Patrol who work to preserve it. One story, Delenda Est, describes a world in which Carthage triumphed over the Roman Republic. The Big Time, by Fritz Leiber, describes a Change War ranging across all of history. Keith Laumer's Worlds of the Imperium is one of the earliest alternate history novels; it was published by Fantastic Stories of the Imagination in 1961, in magazine form, and reprinted by Ace Books in 1962 as one half of an Ace Double. Besides our world, Laumer describes a world ruled by an Imperial aristocracy formed by the merger of European empires, in which the American Revolution never happened, and a third world in post-war chaos ruled by the protagonist's doppelganger. Philip K. Dick's novel, The Man in the High Castle (1962), is an alternate history in which Nazi Germany and Imperial Japan won World War II. This book contains an example of "alternate-alternate" history, in that one of its characters authored a book depicting a reality in which the Allies won the war, itself divergent from real-world history in several aspects. The several characters live within a divided United States, in which the Empire of Japan takes the Pacific states, governing them as a puppet, Nazi Germany takes the East Coast of the United States and parts of the Midwest, with the remnants of the old United States' government as the Neutral Zone, a buffer state between the two superpowers. The book has inspired an Amazon series of the same name. Vladimir Nabokov's novel, Ada or Ardor: A Family Chronicle (1969), is a story of incest that takes place within an alternate North America settled in part by Czarist Russia and that borrows from Dick's idea of "alternate-alternate" history (the world of Nabokov's hero is wracked by rumors of a "counter-earth" that apparently is ours). Some critics believe that the references to a counter-earth suggest that the world portrayed in Ada is a delusion in the mind of the hero (another favorite theme of Dick's novels). Strikingly, the characters in Ada seem to acknowledge their own world as the copy or negative version, calling it "Anti-Terra", while its mythical twin is the real "Terra". Like history, science has followed a divergent path on Anti-Terra: it boasts all the same technology as our world, but all based on water instead of electricity; e.g., when a character in Ada makes a long-distance call, all the toilets in the house flush at once to provide hydraulic power. Guido Morselli described the defeat of Italy (and subsequently France) in World War I in his novel, Past Conditional (1975; ), wherein the static Alpine front line which divided Italy from Austria during that war collapses when the Germans and the Austrians forsake trench warfare and adopt blitzkrieg twenty years in advance. Kingsley Amis set his novel, The Alteration (1976), in the 20th century, but major events in the Reformation did not take place, and Protestantism is limited to the breakaway Republic of New England. Martin Luther was reconciled to the Roman Catholic Church and later became Pope Germanian I. In Nick Hancock and Chris England's 1997 book What Didn't Happen Next: An Alternative History of Football it is suggested that, had Gordon Banks been fit to play in the 1970 FIFA World Cup quarter-final, there would have been no Thatcherism and the post-war consensus would have continued indefinitely. Kim Stanley Robinson's novel, The Years of Rice and Salt (2002), starts at the point of divergence with Timur turning his army away from Europe, and the Black Death has killed 99% of Europe's population, instead of only a third. Robinson explores world history from that point in AD 1405 (807 AH) to about AD 2045 (1467 AH). Rather than following the great man theory of history, focusing on leaders, wars, and major events, Robinson writes more about social history, similar to the Annales School of history theory and Marxist historiography, focusing on the lives of ordinary people living in their time and place. Philip Roth's novel, The Plot Against America (2004), looks at an America where Franklin D. Roosevelt is defeated in 1940 in his bid for a third term as President of the United States, and Charles Lindbergh is elected, leading to a US that features increasing fascism and anti-Semitism. Michael Chabon, occasionally an author of speculative fiction, contributed to the genre with his novel The Yiddish Policemen's Union (2007), which explores a world in which the State of Israel was destroyed in its infancy and many of the world's Jews instead live in a small strip of Alaska set aside by the US government for Jewish settlement. The story follows a Jewish detective solving a murder case in the Yiddish-speaking semi-autonomous city state of Sitka. Stylistically, Chabon borrows heavily from the noir and detective fiction genres, while exploring social issues related to Jewish history and culture. Apart from the alternate history of the Jews and Israel, Chabon also plays with other common tropes of alternate history fiction; in the book, Germany actually loses the war even harder than they did in reality, getting hit with a nuclear bomb instead of just simply losing a ground war (subverting the common "what if Germany won WWII?" trope). Contemporary alternate history in popular literature The late 1980s and the 1990s saw a boom in popular-fiction versions of alternate history, fueled by the emergence of the prolific alternate history author Harry Turtledove, as well as the development of the steampunk genre and two series of anthologies—the What Might Have Been series edited by Gregory Benford and the Alternate ... series edited by Mike Resnick. This period also saw alternate history works by S. M. Stirling, Kim Stanley Robinson, Harry Harrison, Howard Waldrop, Peter Tieryas, and others. In 1986, a sixteen-part epic comic book series called Captain Confederacy began examining a world where the Confederate States of America won the American Civil War. In the series, the Captain and others heroes are staged government propaganda events featuring the feats of these superheroes. Since the late 1990s, Harry Turtledove has been the most prolific practitioner of alternate history and has been given the title "Master of Alternate History" by some. His books include those of Timeline 191 (a.k.a. Southern Victory, also known as TL-191), in which, while the Confederate States of America won the American Civil War, the Union and Imperial Germany defeat the Entente Powers in the two "Great War"s of the 1910s and 1940s (with a Nazi-esque Confederate government attempting to exterminate its Black population), and the Worldwar series, in which aliens invaded Earth during World War II. Other stories by Turtledove include A Different Flesh, in which America was not colonized from Asia during the last ice age; In the Presence of Mine Enemies, in which the Nazis won World War II; and Ruled Britannia, in which the Spanish Armada succeeded in conquering England in the Elizabethan era, with William Shakespeare being given the task of writing the play that will motivate the Britons to rise up against their Spanish conquerors. He also co-authored a book with actor Richard Dreyfuss, The Two Georges, in which the United Kingdom retained the American colonies, with George Washington and King George III making peace. He did a two-volume series in which the Japanese not only bombed Pearl Harbor but also invaded and occupied the Hawaiian Islands. Perhaps the most incessantly explored theme in popular alternate history focuses on worlds in which the Nazis won World War Two. In some versions, the Nazis and/or Axis Powers conquer the entire world; in others, they conquer most of the world but a "Fortress America" exists under siege; while in others, there is a Nazi/Japanese Cold War comparable to the US/Soviet equivalent in 'our' timeline. Fatherland (1992), by Robert Harris, is set in Europe following the Nazi victory. The novel Dominion by C.J. Sansom (2012) is similar in concept but is set in England, with Churchill the leader of an anti-German Resistance and other historic persons in various fictional roles. In the Mecha Samurai Empire series (2016), Peter Tieryas focuses on the Asian-American side of the alternate history, exploring an America ruled by the Japanese Empire while integrating elements of Asian pop culture like mechas and videogames. Several writers have posited points of departure for such a world but then have injected time splitters from the future or paratime travel, for instance James P. Hogan's The Proteus Operation. Norman Spinrad wrote The Iron Dream in 1972, which is intended to be a science fiction novel written by Adolf Hitler after fleeing from Europe to North America in the 1920s. In Jo Walton's "Small Change" series, the United Kingdom made peace with Hitler before the involvement of the United States in World War II, and slowly collapses due to severe economic depression. Former House Speaker Newt Gingrich and William R. Forstchen have written a novel, 1945, in which the US defeated Japan but not Germany in World War II, resulting in a Cold War with Germany rather than the Soviet Union. Gingrich and Forstchen neglected to write the promised sequel; instead, they wrote a trilogy about the American Civil War, starting with Gettysburg: A Novel of the Civil War, in which the Confederates win a victory at the Battle of Gettysburg - however, after Lincoln responds by bringing Grant and his forces to the eastern theater, the Army of Northern Virginia is soon trapped and destroyed in Maryland, and the war ends within weeks. Also from that general era, Martin Cruz Smith, in his first novel, posited an independent American Indian nation following the defeat of Custer in The Indians Won (1970). Beginning with The Probability Broach in 1980, L. Neil Smith wrote several novels that postulated the disintegration of the US Federal Government after Albert Gallatin joins the Whiskey Rebellion in 1794 and eventually leads to the creation of a libertarian utopia. A recent time traveling splitter variant involves entire communities being shifted elsewhere to become the unwitting creators of new time branches. These communities are transported from the present (or the near-future) to the past or to another time-line via a natural disaster, the action of technologically advanced aliens, or a human experiment gone wrong. S. M. Stirling wrote the Island in the Sea of Time trilogy, in which Nantucket Island and all its modern inhabitants are transported to Bronze Age times to become the world's first superpower. In Eric Flint's 1632 series, a small town in West Virginia is transported to 17th century central Europe and drastically changes the course of the Thirty Years' War, which was then underway. John Birmingham's Axis of Time trilogy deals with the culture shock when a United Nations naval task force from 2021 finds itself back in 1942 helping the Allies against the Empire of Japan and the Germans (and doing almost as much harm as good in spite of its advanced weapons). The series also explores the cultural impacts of people with 2021 ideals interacting with 1940s culture. Similarly, Robert Charles Wilson's Mysterium depicts a failed US government experiment which transports a small American town into an alternative version of the US run by believers in a form of Christianity known as Gnosticism, who are engaged in a bitter war with the "Spanish" in Mexico (the chief scientist at the laboratory where the experiment occurred is described as a Gnostic, and references to Christian Gnosticism appear repeatedly in the book). In Time for Patriots by retired astronomer Thomas Wm. Hamilton (4897 Tomhamilton) a town and military academy on Long Island are transported back to 1770, where they shorten the American Revolution, rewrite the Constitution, prolong Mozart's life, battle Barbary pirates, and have other adventures. Although not dealing in physical time travel, in his alt-history novel Marx Returns, Jason Barker introduces anachronisms into the life and times of Karl Marx, such as when his wife Jenny sings a verse from the Sex Pistols's song "Anarchy in the U.K.", or in the games of chess she plays with the Marxes' housekeeper Helene Demuth, which on one occasion involves a Caro–Kann Defence. In her review of the novel, Nina Power writes of "Jenny’s 'utopian' desire for an end to time", an attitude which, according to Power, is inspired by her husband's co-authored book The German Ideology. However, in keeping with the novel's anachronisms, the latter was not published until 1932. By contrast, the novel's timeline ends in 1871. In fantasy genre Many works of straight fantasy and science fantasy take place in historical settings, though with the addition of, for example, magic or mythological beasts. Some present a secret history in which the modern day world no longer believes that these elements ever existed. Many ambiguous alternate/secret histories are set in Renaissance or pre-Renaissance times, and may explicitly include a "retreat" from the world, which would explain the current absence of such phenomena. Other stories make plan a divergence of some kind. In Poul Anderson's Three Hearts and Three Lions in which the Matter of France is history and the fairy folk are real and powerful. The same author's A Midsummer Tempest, occurs in a world in which the plays of William Shakespeare (called here "the Great Historian"), presented the literal truth in every instance. The novel itself takes place in the era of Oliver Cromwell and Charles I. Here, the English Civil War had a different outcome, and the Industrial Revolution has occurred early. Randall Garrett's "Lord Darcy" series presents a point of divergence: a monk systemizes magic rather than science, so the use of foxglove to treat heart disease is regarded as superstition. Another point of divergence occurs in 1199, when Richard the Lionheart survives the Siege of Chaluz and returns to England and makes the Angevin Empire so strong that it survives into the 20th century. Jonathan Strange & Mr Norrell by Susanna Clarke takes place in an England where a separate Kingdom ruled by the Raven King and founded on magic existed in Northumbria for over 300 years. In Patricia Wrede's Regency fantasies, Great Britain has a Royal Society of Wizards. The Tales of Alvin Maker series by Orson Scott Card (a parallel to the life of Joseph Smith, founder of the Latter Day Saint movement) takes place in an alternate America, beginning in the early 19th century. Prior to that time, a POD occurred: England, under the rule of Oliver Cromwell, had banished "makers", or anyone else demonstrating "knacks" (an ability to perform seemingly supernatural feats) to the North American continent. Thus the early American colonists embraced as perfectly ordinary these gifts, and counted on them as a part of their daily lives. The political division of the continent is considerably altered, with two large English colonies bookending a smaller "American" nation, one aligned with England, and the other governed by exiled Cavaliers. Actual historical figures are seen in a much different light: Ben Franklin is revered as the continent's finest "maker", George Washington was executed after being captured, and "Tom" Jefferson is the first president of "Appalachia", the result of a compromise between the Continentals and the British Crown. On the other hand, when the "Old Ones" (fairies) still manifest themselves in England in Keith Roberts's Pavane, which takes place in a technologically backward world after a Spanish assassination of Elizabeth I allowed the Spanish Armada to conquer England, the possibility that the fairies were real but retreated from modern advances makes the POD possible: the fairies really were present all along, in a secret history. Again, in the English Renaissance fantasy Armor of Light by Melissa Scott and Lisa A. Barnett, the magic used in the book, by Dr. John Dee and others, actually was practiced in the Renaissance; positing a secret history of effective magic makes this an alternate history with a point of departure. Sir Philip Sidney survives the Battle of Zutphen in 1586, and shortly thereafter saving the life of Christopher Marlowe. When the magical version of our world's history is set in contemporary times, the distinction becomes clear between alternate history on the one hand and contemporary fantasy, using in effect a form of secret history (as when Josepha Sherman's Son of Darkness has an elf living in New York City, in disguise) on the other. In works such as Robert A. Heinlein's Magic, Incorporated where a construction company can use magic to rig up stands at a sporting event and Poul Anderson's Operation Chaos and its sequel Operation Luna, where djinns are serious weapons of war—with atomic bombs—the use of magic throughout the United States and other modern countries makes it clear that this is not secret history—although references in Operation Chaos to degaussing the effects of cold iron make it possible that it is the result of a POD. The sequel clarifies this as the result of a collaboration of Einstein and Planck in 1901, resulting in the theory of "rhea tics". Henry Moseley applies this theory to "degauss the effects of cold iron and release the goetic forces." This results in the suppression of ferromagnetism and the re-emergence of magic and magical creatures. Alternate history shades off into other fantasy subgenres when the use of actual, though altered, history and geography decreases, although a culture may still be clearly the original source; Barry Hughart's Bridge of Birds and its sequels take place in a fantasy world, albeit one clearly based on China, and with allusions to actual Chinese history, such as the Empress Wu. Richard Garfinkle's Celestial Matters incorporates ancient Chinese physics and Greek Aristotelian physics, using them as if factual. Alternate history has long been a staple of Japanese speculative fiction with such authors as Futaro Yamada and Ryō Hanmura writing novels set in recognizable historical settings withaddded supernatural or science fiction elements. Ryō Hanmura's 1973 Musubi no Yama Hiroku which recreated 400 years of Japan's history from the perspective of a secret magical family with psychic abilities. The novel has since come to be recognized as a masterpiece of Japanese speculative fiction. Twelve years later, author Hiroshi Aramata wrote the groundbreaking Teito Monogatari which reimagined the history of Tokyo across the 20th century in a world heavily influenced by the supernatural. Television The TV show Sliders explores different possible alternate realities by having the protagonist "slide" into different parallel dimensions of the same planet Earth. Another TV show Motherland: Fort Salem explores a female-dominated world in which witchcraft is real. Its world diverged from our timeline when the Salem witch trials are resolved by an agreement between witches and ungifted humans. The anime Fena: Pirate Princess featured an alternate 18th century. The TV show The Man in the High Castle is an adaptation of the novel with the same name that ran for four seasons. Video games For the same reasons that this genre is explored by role-playing games, alternate history is also an intriguing backdrop for the storylines of many video games. A famous example of an alternate history game is Command & Conquer: Red Alert. Released in 1996, the game presents a point of divergence in 1946 in which Albert Einstein goes back in time to prevent World War II from ever taking place by erasing Adolf Hitler from time after he is released from Landsberg Prison in 1924. Einstein is successful in his mission, but in the process, he allows Joseph Stalin and the Soviet Union to become powerful enough to launch a massive campaign to conquer Europe. In the Civilization series, the player guides a civilization from prehistory to the present and creates radically altered versions of history on a long time scale. Several scenarios recreate a particular period, which becomes the "point of divergence" in an alternate history shaped by the player's actions. Popular examples in Sid Meier's Civilization IV include Desert War, set in the Mediterranean theatre of World War II and featuring scripted events tied to possible outcomes of battles; Broken Star, set in a hypothetical Russian civil war in 2010; and Rhye's and Fall of Civilization, an 'Earth simulator' designed to mirror a history as closely as possible but incorporating unpredictable elements to provide realistic alternate settings. In some games such as the Metal Gear and Resident Evil series, events that were originally intended to represent the near future when the games were originally released later ended up becoming alternate histories in later entries in those franchises. For example, Metal Gear 2: Solid Snake (1990), set in 1999, depicted a near future that ended up becoming an alternate history in Metal Gear Solid (1998). Likewise, Resident Evil (1996) and Resident Evil 2 (1998), both set in 1998, depicted near-future events that had later become an alternative history by the time Resident Evil 4 (2005) was released. In the 2009 steampunk shooter, Damnation is set on an alternate version of planet Earth, in the early 20th century after the American Civil War, which had spanned over several decades, and steam engines replace combustion engines. The game sees the protagonists fighting off a rich industrialist who wants to do away with both the Union and the Confederacy in one swift movement and turn the United States of America into a country called the "American Empire" with a totalitarian dictatorship. Crimson Skies is one example of an alternate history spawning multiple interpretations in multiple genres. The stories and games in Crimson Skies take place in an alternate 1930s United States in which the nation crumbled into many hostile states following the effects of the Great Depression, the Great War, and Prohibition. With the road and railway system destroyed, commerce took to the skies, which led to the emergence of air pirate gangs who plunder the aerial commerce. The game Freedom Fighters portrays a situation similar to that of the movie Red Dawn and Red Alert 2 but less comically than the latter. The point of divergence is during World War II in which the Soviet Union develops an atomic bomb first and uses it on Berlin. With the balance of power and influence tipped in Russia's favor, history diverges. Brief summaries at the beginning of the game inform the player of the Communist bloc's complete takeover of Europe by 1953, a different ending to the Cuban Missile Crisis, and the spread of Soviet influence into South America and Mexico. Similarly, the 2007 video game World in Conflict is set in 1989, with the Soviet Union on the verge of collapse. The point of divergence is several months before the opening of the game, when Warsaw Pact forces staged a desperate invasion of Western Europe. As the game begins, a Soviet invasion force lands in Seattle and takes advantage of the fact that most of the US military is in Europe. The game Battlestations: Pacific, released in 2008, offered in alternate history campaign for the Imperial Japanese Navy in which Japan destroys all three carriers in the Battle of Midway, which is followed by a successful invasion of the island. That causes the United States to lack any sort of aerial power to fight the Japanese and to be continuously forced onto the defense. Turning Point: Fall of Liberty, released in February 2008, is an alternate history first-person shooter in which Winston Churchill died in 1931 from being struck by a taxi cab. Therefore, Great Britain lacks the charismatic leader needed to keep the country together and allows it to be successfully conquered by Nazi Germany during Operation Sea Lion in 1940. Germany later conquers the rest of Europe, as well as North Africa and the Middle East, and produces a massive number of Wunderwaffe. The Axis powers launch a surprise invasion of the isolationist United States in the Eastern Seaboard in 1953, which forces the country to surrender and submit to a puppet government. Another alternate history game involving Nazis is War Front: Turning Point in which Hitler died during the early days of World War II and so a much more effective leadership rose to power. Under the command of a new Führer (who is referred to as "Chancellor", with his real name never being revealed), Operation Sealion succeeds, and the Nazis successfully conquer Britain and spark a cold war between them and the Allied Powers. The Fallout series of role-playing games is set in a divergent US, whose history after World War II diverges from the real world to follow a retro-futuristic timeline. For example, fusion power was invented quite soon after the end of the war, but the transistor was never developed. The result was a future that has a 1950s "World of Tomorrow" feel to it, with extremely high technology like artificial intelligence implemented with thermionic valves and other technologies that are now considered obsolete. Many game series by the Swedish developer Paradox Interactive start at a concise point in history and allow the player to immerse in the role of a contemporary leader and alter the course of in-game history. The most prominent game with that setting is Crusader Kings II. S.T.A.L.K.E.R. games have an alternate history at the Chernobyl Exclusion Zone in which a special area called "The Zone" is formed. Wolfenstein: The New Order is set in an alternate 1960 in which the Nazis won World War II and do so also by acquiring high technology. The sequel Wolfenstein II: The New Colossus continues that but is set in the conquered United States of America. A game made by Paradox Interactive, "Alternate WWII: The Game" was supposed to release in June 2021, but was canceled. It was mostly secret but announced to the public when cancelled. Online Fans of alternate history have made use of the internet from a very early point to showcase their own works and provide useful tools for those fans searching for anything alternate history, first in mailing lists and usenet groups, later in web databases and forums. The "Usenet Alternate History List" was first posted on April 11, 1991, to the Usenet newsgroup rec.arts.sf-lovers. In May 1995, the dedicated newsgroup soc.history.what-if was created for showcasing and discussing alternate histories. Its prominence declined with the general migration from unmoderated usenet to moderated web forums, most prominently AlternateHistory.com, the self-described "largest gathering of alternate history fans on the internet" with over 10,000 active members. In addition to these discussion forums, in 1997 Uchronia: The Alternate History List was created as an online repository, now containing over 2,900 alternate history novels, stories, essays, and other printed materials in several different languages. Uchronia was selected as the Sci Fi Channel's "Sci Fi Site of the Week" twice. See also 20th century in science fiction Alien space bats Alternate ending Alternative future American Civil War alternate histories Dieselpunk Dystopian Fictional universe Future history The Garden of Forking Paths Historical revisionism Hypothetical Axis victory in World War II Invasion literature Jonbar hinge List of alternate history fiction Possible worlds Pulp novels Ruritanian romance References Further reading Chapman, Edgar L., and Carl B. Yoke (eds.). Classic and Iconoclastic Alternate History Science Fiction. Mellen, 2003. Collins, William Joseph. Paths Not Taken: The Development, Structure, and Aesthetics of the Alternative History. University of California at Davis 1990. Darius, Julian. "58 Varieties: Watchmen and Revisionism". In Minutes to Midnight: Twelve Essays on Watchmen. Sequart Research & Literacy Organization, 2010. Focuses on Watchmen as alternate history. Robert Cowley (ed.), What If? Military Historians Imagine What Might Have Been. Pan Books, 1999. Gevers, Nicholas. Mirrors of the Past: Versions of History in Science Fiction and Fantasy. University of Cape Town, 1997 Hellekson, Karen. The Alternate History: Refiguring Historical Time. Kent State University Press, 2001 Keen, Antony G. "Alternate Histories of the Roman Empire in Stephen Baxter, Robert Silverberg and Sophia McDougall". Foundation: The International Review of Science Fiction 102, Spring 2008. McKnight, Edgar Vernon, Jr. Alternative History: The Development of a Literary Genre. University of North Carolina at Chapel Hill, 1994. Morgan, Glyn, and C. Palmer-Patel (eds.). Sideways in Time: Critical Essays on Alternate History Fiction. Liverpool University Press, 2019. Nedelkovh, Aleksandar B. British and American Science Fiction Novel 1950–1980 with the Theme of Alternative History (an Axiological Approach). 1994 , 1999 . Rosenfeld, Gavriel David. The World Hitler Never Made. Alternate History and the Memory of Nazism. 2005 Rosenfeld, Gavriel David. "Why Do We Ask 'What If?' Reflections on the Function of Alternate History." History and Theory 41, Theme Issue 41 (December 2002), 90–103 Schneider-Mayerson, Matthew. "What Almost Was: The Politics of the Contemporary Alternate History Novel." American Studies 30, 3–4 (Summer 2009), 63–83. Singles, Kathleen. Alternate History: Playing With Contingency and Necessity. De Gruyter, Inc., 2013. External links Historical novels subgenres

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1206

https://en.wikipedia.org/wiki/Atomic%20orbital

Atomic orbital

In atomic theory and quantum mechanics, an atomic orbital is a mathematical function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. The term atomic orbital may also refer to the physical region or space where the electron can be calculated to be present, as predicted by the particular mathematical form of the orbital. Each orbital in an atom is characterized by a set of values of the three quantum numbers , , and , which respectively correspond to the electron's energy, angular momentum, and an angular momentum vector component (the magnetic quantum number). Alternative to the magnetic quantum number, the orbitals are often labeled by the associated harmonic polynomials (e.g. xy, x2−y2). Each such orbital can be occupied by a maximum of two electrons, each with its own projection of spin . The simple names s orbital, p orbital, d orbital, and f orbital refer to orbitals with angular momentum quantum number and respectively. These names, together with the value of , are used to describe the electron configurations of atoms. They are derived from the description by early spectroscopists of certain series of alkali metal spectroscopic lines as sharp, principal, diffuse, and fundamental. Orbitals for > 3 continue alphabetically (g, h, i, k, ...), omitting j because some languages do not distinguish between the letters "i" and "j". Atomic orbitals are the basic building blocks of the atomic orbital model (alternatively known as the electron cloud or wave mechanics model), a modern framework for visualizing the submicroscopic behavior of electrons in matter. In this model the electron cloud of a multi-electron atom may be seen as being built up (in approximation) in an electron configuration that is a product of simpler hydrogen-like atomic orbitals. The repeating periodicity of the blocks of 2, 6, 10, and 14 elements within sections of the periodic table arises naturally from the total number of electrons that occupy a complete set of s, p, d, and f atomic orbitals, respectively, although for higher values of the quantum number , particularly when the atom in question bears a positive charge, the energies of certain sub-shells become very similar and so the order in which they are said to be populated by electrons (e.g. Cr = [Ar]4s13d5 and Cr2+ = [Ar]3d4) can only be rationalized somewhat arbitrarily. Electron properties With the development of quantum mechanics and experimental findings (such as the two slit diffraction of electrons), it was found that the orbiting electrons around a nucleus could not be fully described as particles, but needed to be explained by the wave-particle duality. In this sense, the electrons have the following properties: Wave-like properties: The electrons do not orbit the nucleus in the manner of a planet orbiting the sun, but instead exist as standing waves. Thus the lowest possible energy an electron can take is similar to the fundamental frequency of a wave on a string. Higher energy states are similar to harmonics of that fundamental frequency. The electrons are never in a single point location, although the probability of interacting with the electron at a single point can be found from the wave function of the electron. The charge on the electron acts like it is smeared out in space in a continuous distribution, proportional at any point to the squared magnitude of the electron's wave function. Particle-like properties: The number of electrons orbiting the nucleus can only be an integer. Electrons jump between orbitals like particles. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon. The electrons retain particle-like properties such as: each wave state has the same electrical charge as its electron particle. Each wave state has a single discrete spin (spin up or spin down) depending on its superposition. Thus, electrons cannot be described simply as solid particles. An analogy might be that of a large and often oddly shaped "atmosphere" (the electron), distributed around a relatively tiny planet (the atomic nucleus). Atomic orbitals exactly describe the shape of this "atmosphere" only when a single electron is present in an atom. When more electrons are added to a single atom, the additional electrons tend to more evenly fill in a volume of space around the nucleus so that the resulting collection (sometimes termed the atom's "electron cloud") tends toward a generally spherical zone of probability describing the electron's location, because of the uncertainty principle. Formal quantum mechanical definition Atomic orbitals may be defined more precisely in formal quantum mechanical language. They are approximate solutions to the Schrodinger equation for the electrons bound to the atom by the electric field of the atom's nucleus. Specifically, in quantum mechanics, the state of an atom, i.e., an eigenstate of the atomic Hamiltonian, is approximated by an expansion (see configuration interaction expansion and basis set) into linear combinations of anti-symmetrized products (Slater determinants) of one-electron functions. The spatial components of these one-electron functions are called atomic orbitals. (When one considers also their spin component, one speaks of atomic spin orbitals.) A state is actually a function of the coordinates of all the electrons, so that their motion is correlated, but this is often approximated by this independent-particle model of products of single electron wave functions. (The London dispersion force, for example, depends on the correlations of the motion of the electrons.) In atomic physics, the atomic spectral lines correspond to transitions (quantum leaps) between quantum states of an atom. These states are labeled by a set of quantum numbers summarized in the term symbol and usually associated with particular electron configurations, i.e., by occupation schemes of atomic orbitals (for example, 1s2 2s2 2p6 for the ground state of neon-term symbol: 1S0). This notation means that the corresponding Slater determinants have a clear higher weight in the configuration interaction expansion. The atomic orbital concept is therefore a key concept for visualizing the excitation process associated with a given transition. For example, one can say for a given transition that it corresponds to the excitation of an electron from an occupied orbital to a given unoccupied orbital. Nevertheless, one has to keep in mind that electrons are fermions ruled by the Pauli exclusion principle and must be distinguished from each other. Moreover, it sometimes happens that the configuration interaction expansion converges very slowly and that one cannot speak about simple one-determinant wave function at all. This is the case when electron correlation is large. Fundamentally, an atomic orbital is a one-electron wave function, even though most electrons do not exist in one-electron atoms, and so the one-electron view is an approximation. When thinking about orbitals, we are often given an orbital visualization heavily influenced by the Hartree–Fock approximation, which is one way to reduce the complexities of molecular orbital theory. Types of orbitals Atomic orbitals can be the hydrogen-like "orbitals" which are exact solutions to the Schrödinger equation for a hydrogen-like "atom" (i.e., an atom with one electron). Alternatively, atomic orbitals refer to functions that depend on the coordinates of one electron (i.e., orbitals) but are used as starting points for approximating wave functions that depend on the simultaneous coordinates of all the electrons in an atom or molecule. The coordinate systems chosen for atomic orbitals are usually spherical coordinates in atoms and Cartesian in polyatomic molecules. The advantage of spherical coordinates (for atoms) is that an orbital wave function is a product of three factors each dependent on a single coordinate: . The angular factors of atomic orbitals generate s, p, d, etc. functions as real combinations of spherical harmonics (where and are quantum numbers). There are typically three mathematical forms for the radial functions  which can be chosen as a starting point for the calculation of the properties of atoms and molecules with many electrons: The hydrogen-like atomic orbitals are derived from the exact solutions of the Schrödinger Equation for one electron and a nucleus, for a hydrogen-like atom. The part of the function that depends on the distance r from the nucleus has nodes (radial nodes) and decays as . The Slater-type orbital (STO) is a form without radial nodes but decays from the nucleus as does the hydrogen-like orbital. The form of the Gaussian type orbital (Gaussians) has no radial nodes and decays as . Although hydrogen-like orbitals are still used as pedagogical tools, the advent of computers has made STOs preferable for atoms and diatomic molecules since combinations of STOs can replace the nodes in hydrogen-like atomic orbital. Gaussians are typically used in molecules with three or more atoms. Although not as accurate by themselves as STOs, combinations of many Gaussians can attain the accuracy of hydrogen-like orbitals. History The term "orbital" was coined by Robert Mulliken in 1932 as an abbreviation for one-electron orbital wave function. However, the idea that electrons might revolve around a compact nucleus with definite angular momentum was convincingly argued at least 19 years earlier by Niels Bohr, and the Japanese physicist Hantaro Nagaoka published an orbit-based hypothesis for electronic behavior as early as 1904. Explaining the behavior of these electron "orbits" was one of the driving forces behind the development of quantum mechanics. Early models With J. J. Thomson's discovery of the electron in 1897, it became clear that atoms were not the smallest building blocks of nature, but were rather composite particles. The newly discovered structure within atoms tempted many to imagine how the atom's constituent parts might interact with each other. Thomson theorized that multiple electrons revolved in orbit-like rings within a positively charged jelly-like substance, and between the electron's discovery and 1909, this "plum pudding model" was the most widely accepted explanation of atomic structure. Shortly after Thomson's discovery, Hantaro Nagaoka predicted a different model for electronic structure. Unlike the plum pudding model, the positive charge in Nagaoka's "Saturnian Model" was concentrated into a central core, pulling the electrons into circular orbits reminiscent of Saturn's rings. Few people took notice of Nagaoka's work at the time, and Nagaoka himself recognized a fundamental defect in the theory even at its conception, namely that a classical charged object cannot sustain orbital motion because it is accelerating and therefore loses energy due to electromagnetic radiation. Nevertheless, the Saturnian model turned out to have more in common with modern theory than any of its contemporaries. Bohr atom In 1909, Ernest Rutherford discovered that the bulk of the atomic mass was tightly condensed into a nucleus, which was also found to be positively charged. It became clear from his analysis in 1911 that the plum pudding model could not explain atomic structure. In 1913, Rutherford's post-doctoral student, Niels Bohr, proposed a new model of the atom, wherein electrons orbited the nucleus with classical periods, but were only permitted to have discrete values of angular momentum, quantized in units h/2π. This constraint automatically permitted only certain values of electron energies. The Bohr model of the atom fixed the problem of energy loss from radiation from a ground state (by declaring that there was no state below this), and more importantly explained the origin of spectral lines. After Bohr's use of Einstein's explanation of the photoelectric effect to relate energy levels in atoms with the wavelength of emitted light, the connection between the structure of electrons in atoms and the emission and absorption spectra of atoms became an increasingly useful tool in the understanding of electrons in atoms. The most prominent feature of emission and absorption spectra (known experimentally since the middle of the 19th century), was that these atomic spectra contained discrete lines. The significance of the Bohr model was that it related the lines in emission and absorption spectra to the energy differences between the orbits that electrons could take around an atom. This was, however, not achieved by Bohr through giving the electrons some kind of wave-like properties, since the idea that electrons could behave as matter waves was not suggested until eleven years later. Still, the Bohr model's use of quantized angular momenta and therefore quantized energy levels was a significant step towards the understanding of electrons in atoms, and also a significant step towards the development of quantum mechanics in suggesting that quantized restraints must account for all discontinuous energy levels and spectra in atoms. With de Broglie's suggestion of the existence of electron matter waves in 1924, and for a short time before the full 1926 Schrödinger equation treatment of hydrogen-like atoms, a Bohr electron "wavelength" could be seen to be a function of its momentum, and thus a Bohr orbiting electron was seen to orbit in a circle at a multiple of its half-wavelength. The Bohr model for a short time could be seen as a classical model with an additional constraint provided by the 'wavelength' argument. However, this period was immediately superseded by the full three-dimensional wave mechanics of 1926. In our current understanding of physics, the Bohr model is called a semi-classical model because of its quantization of angular momentum, not primarily because of its relationship with electron wavelength, which appeared in hindsight a dozen years after the Bohr model was proposed. The Bohr model was able to explain the emission and absorption spectra of hydrogen. The energies of electrons in the n = 1, 2, 3, etc. states in the Bohr model match those of current physics. However, this did not explain similarities between different atoms, as expressed by the periodic table, such as the fact that helium (two electrons), neon (10 electrons), and argon (18 electrons) exhibit similar chemical inertness. Modern quantum mechanics explains this in terms of electron shells and subshells which can each hold a number of electrons determined by the Pauli exclusion principle. Thus the n = 1 state can hold one or two electrons, while the n = 2 state can hold up to eight electrons in 2s and 2p subshells. In helium, all n = 1 states are fully occupied; the same is true for n = 1 and n = 2 in neon. In argon, the 3s and 3p subshells are similarly fully occupied by eight electrons; quantum mechanics also allows a 3d subshell but this is at higher energy than the 3s and 3p in argon (contrary to the situation in the hydrogen atom) and remains empty. Modern conceptions and connections to the Heisenberg uncertainty principle Immediately after Heisenberg discovered his uncertainty principle, Bohr noted that the existence of any sort of wave packet implies uncertainty in the wave frequency and wavelength, since a spread of frequencies is needed to create the packet itself. In quantum mechanics, where all particle momenta are associated with waves, it is the formation of such a wave packet which localizes the wave, and thus the particle, in space. In states where a quantum mechanical particle is bound, it must be localized as a wave packet, and the existence of the packet and its minimum size implies a spread and minimal value in particle wavelength, and thus also momentum and energy. In quantum mechanics, as a particle is localized to a smaller region in space, the associated compressed wave packet requires a larger and larger range of momenta, and thus larger kinetic energy. Thus the binding energy to contain or trap a particle in a smaller region of space increases without bound as the region of space grows smaller. Particles cannot be restricted to a geometric point in space, since this would require an infinite particle momentum. In chemistry, Schrödinger, Pauling, Mulliken and others noted that the consequence of Heisenberg's relation was that the electron, as a wave packet, could not be considered to have an exact location in its orbital. Max Born suggested that the electron's position needed to be described by a probability distribution which was connected with finding the electron at some point in the wave-function which described its associated wave packet. The new quantum mechanics did not give exact results, but only the probabilities for the occurrence of a variety of possible such results. Heisenberg held that the path of a moving particle has no meaning if we cannot observe it, as we cannot with electrons in an atom. In the quantum picture of Heisenberg, Schrödinger and others, the Bohr atom number n for each orbital became known as an n-sphere in a three-dimensional atom and was pictured as the most probable energy of the probability cloud of the electron's wave packet which surrounded the atom. Orbital names Orbital notation and subshells Orbitals have been given names, which are usually given in the form: where X is the energy level corresponding to the principal quantum number ; type is a lower-case letter denoting the shape or subshell of the orbital, corresponding to the angular momentum quantum number . For example, the orbital 1s (pronounced as the individual numbers and letters: "'one' 'ess'") is the lowest energy level () and has an angular quantum number of , denoted as s. Orbitals with are denoted as p, d and f respectively. The set of orbitals for a given n and is called a subshell, denoted . The exponent y shows the number of electrons in the subshell. For example, the notation 2p4 indicates that the 2p subshell of an atom contains 4 electrons. This subshell has 3 orbitals, each with n = 2 and = 1. X-ray notation There is also another, less common system still used in X-ray science known as X-ray notation, which is a continuation of the notations used before orbital theory was well understood. In this system, the principal quantum number is given a letter associated with it. For , the letters associated with those numbers are K, L, M, N, O, ... respectively. Hydrogen-like orbitals The simplest atomic orbitals are those that are calculated for systems with a single electron, such as the hydrogen atom. An atom of any other element ionized down to a single electron is very similar to hydrogen, and the orbitals take the same form. In the Schrödinger equation for this system of one negative and one positive particle, the atomic orbitals are the eigenstates of the Hamiltonian operator for the energy. They can be obtained analytically, meaning that the resulting orbitals are products of a polynomial series, and exponential and trigonometric functions. (see hydrogen atom). For atoms with two or more electrons, the governing equations can only be solved with the use of methods of iterative approximation. Orbitals of multi-electron atoms are qualitatively similar to those of hydrogen, and in the simplest models, they are taken to have the same form. For more rigorous and precise analysis, numerical approximations must be used. A given (hydrogen-like) atomic orbital is identified by unique values of three quantum numbers: , , and . The rules restricting the values of the quantum numbers, and their energies (see below), explain the electron configuration of the atoms and the periodic table. The stationary states (quantum states) of the hydrogen-like atoms are its atomic orbitals. However, in general, an electron's behavior is not fully described by a single orbital. Electron states are best represented by time-depending "mixtures" (linear combinations) of multiple orbitals. See Linear combination of atomic orbitals molecular orbital method. The quantum number first appeared in the Bohr model where it determines the radius of each circular electron orbit. In modern quantum mechanics however, determines the mean distance of the electron from the nucleus; all electrons with the same value of n lie at the same average distance. For this reason, orbitals with the same value of n are said to comprise a "shell". Orbitals with the same value of n and also the same value of  are even more closely related, and are said to comprise a "subshell". Quantum numbers Because of the quantum mechanical nature of the electrons around a nucleus, atomic orbitals can be uniquely defined by a set of integers known as quantum numbers. These quantum numbers only occur in certain combinations of values, and their physical interpretation changes depending on whether real or complex versions of the atomic orbitals are employed. Complex orbitals In physics, the most common orbital descriptions are based on the solutions to the hydrogen atom, where orbitals are given by the product between a radial function and a pure spherical harmonic. The quantum numbers, together with the rules governing their possible values, are as follows: The principal quantum number describes the energy of the electron and is always a positive integer. In fact, it can be any positive integer, but for reasons discussed below, large numbers are seldom encountered. Each atom has, in general, many orbitals associated with each value of n; these orbitals together are sometimes called electron shells. The azimuthal quantum number describes the orbital angular momentum of each electron and is a non-negative integer. Within a shell where is some integer , ranges across all (integer) values satisfying the relation . For instance, the  shell has only orbitals with , and the  shell has only orbitals with , and . The set of orbitals associated with a particular value of  are sometimes collectively called a subshell. The magnetic quantum number, , describes the magnetic moment of an electron in an arbitrary direction, and is also always an integer. Within a subshell where is some integer , ranges thus: . The above results may be summarized in the following table. Each cell represents a subshell, and lists the values of available in that subshell. Empty cells represent subshells that do not exist. Subshells are usually identified by their - and -values. is represented by its numerical value, but is represented by a letter as follows: 0 is represented by 's', 1 by 'p', 2 by 'd', 3 by 'f', and 4 by 'g'. For instance, one may speak of the subshell with and as a '2s subshell'. Each electron also has a spin quantum number, s, which describes the spin of each electron (spin up or spin down). The number s can be + or −. The Pauli exclusion principle states that no two electrons in an atom can have the same values of all four quantum numbers. If there are two electrons in an orbital with given values for three quantum numbers, (, , ), these two electrons must differ in their spin. The above conventions imply a preferred axis (for example, the z direction in Cartesian coordinates), and they also imply a preferred direction along this preferred axis. Otherwise there would be no sense in distinguishing from . As such, the model is most useful when applied to physical systems that share these symmetries. The Stern–Gerlach experiment — where an atom is exposed to a magnetic field — provides one such example. Real orbitals In addition to the complex orbitals described above, it is common, especially in the chemistry literature, to utilize real atomic orbitals. These real orbitals arise from simple linear combinations of the complex orbitals. Using the Condon-Shortley phase convention, the real atomic orbitals are related to the complex atomic orbitals in the same way that the real spherical harmonics are related to the complex spherical harmonics. Letting denote a complex atomic orbital with quantum numbers , , and , we define the real atomic orbitals by If , with the radial part of the orbital, this definition is equivalent to where is the real spherical harmonic related to either the real or imaginary part of the complex spherical harmonic . Real spherical harmonics are physically relevant when an atom is embedded in a crystalline solid, in which case there are multiple preferred symmetry axes but no single preferred direction . Real atomic orbitals are also more frequently encountered in introductory chemistry textbooks and shown in common orbital visualizations. In the real hydrogen-like orbitals, the quantum numbers and have the same interpretation and significance as their complex counterparts, but is no longer a good quantum number (though its absolute value is). Some real atomic orbitals are given specific names beyond the simple designation. Orbitals with quantum number equal to are referred to as orbitals. With this it already possible to assigns names to complex orbitals such as where the first symbol is the quantum number, the second number is the symbol for that particular quantum number and the subscript is the quantum number. As an example of how the full orbital names are generated for real orbitals, we may calculate . From the table of spherical harmonics, we have that with . We then have Likewise we have . As a more complicated example, we also have In all of these cases we generate a Cartesian label for the orbital by examining, and abbreviating, the polynomial in , , and appearing in the numerator. We ignore any terms in the polynomial except for the term with the highest exponent in . We then use the abbreviated polynomial as a subscript label for the atomic state, using the same nomenclature as above to indicate the and quantum numbers. Note that the expression above all use the Condon-Shortley phase convention which is favored by quantum physicists. Other conventions for the phase of the spherical harmonics exists. Under these different conventions the and orbitals may appear, for example, as the sum and difference of and , contrary to what is shown above. Below is a tabulation of these Cartesian polynomial names for the atomic orbitals. Note that there does not seem to be reference in the literature as to how to abbreviate the lengthy Cartesian spherical harmonic polynomials for so there does not seem be consensus as to the naming of orbitals or higher according to this nomenclature. Shapes of orbitals Simple pictures showing orbital shapes are intended to describe the angular forms of regions in space where the electrons occupying the orbital are likely to be found. The diagrams cannot show the entire region where an electron can be found, since according to quantum mechanics there is a non-zero probability of finding the electron (almost) anywhere in space. Instead the diagrams are approximate representations of boundary or contour surfaces where the probability density has a constant value, chosen so that there is a certain probability (for example 90%) of finding the electron within the contour. Although as the square of an absolute value is everywhere non-negative, the sign of the wave function is often indicated in each subregion of the orbital picture. Sometimes the function will be graphed to show its phases, rather than the which shows probability density but has no phases (which have been lost in the process of taking the absolute value, since is a complex number). orbital graphs tend to have less spherical, thinner lobes than graphs, but have the same number of lobes in the same places, and otherwise are recognizable. This article, in order to show wave function phases, shows mostly graphs. The lobes can be viewed as standing wave interference patterns between the two counter rotating, ring resonant travelling wave "" and "" modes, with the projection of the orbital onto the xy plane having a resonant "" wavelengths around the circumference. Though rarely depicted, the travelling wave solutions can be viewed as rotating banded tori, with the bands representing phase information. For each there are two standing wave solutions and . For the case where the orbital is vertical, counter rotating information is unknown, and the orbital is z-axis symmetric. For the case where there are no counter rotating modes. There are only radial modes and the shape is spherically symmetric. For any given , the smaller is, the more radial nodes there are. For any given , the smaller is, the fewer radial nodes there are (zero for whichever first has that orbital). Loosely speaking is energy, is analogous to eccentricity, and is orientation. In the classical case, a ring resonant travelling wave, for example in a circular transmission line, unless actively forced, will spontaneously decay into a ring resonant standing wave because reflections will build up over time at even the smallest imperfection or discontinuity. Generally speaking, the number determines the size and energy of the orbital for a given nucleus: as increases, the size of the orbital increases. When comparing different elements, the higher nuclear charge of heavier elements causes their orbitals to contract by comparison to lighter ones, so that the overall size of the whole atom remains very roughly constant, even as the number of electrons in heavier elements (higher ) increases. Also in general terms, determines an orbital's shape, and its orientation. However, since some orbitals are described by equations in complex numbers, the shape sometimes depends on also. Together, the whole set of orbitals for a given and fill space as symmetrically as possible, though with increasingly complex sets of lobes and nodes. The single s-orbitals () are shaped like spheres. For it is roughly a solid ball (it is most dense at the center and fades exponentially outwardly), but for or more, each single s-orbital is composed of spherically symmetric surfaces which are nested shells (i.e., the "wave-structure" is radial, following a sinusoidal radial component as well). See illustration of a cross-section of these nested shells, at right. The s-orbitals for all numbers are the only orbitals with an anti-node (a region of high wave function density) at the center of the nucleus. All other orbitals (p, d, f, etc.) have angular momentum, and thus avoid the nucleus (having a wave node at the nucleus). Recently, there has been an effort to experimentally image the 1s and 2p orbitals in a SrTiO3 crystal using scanning transmission electron microscopy with energy dispersive x-ray spectroscopy. Because the imaging was conducted using an electron beam, Coulombic beam-orbital interaction that is often termed as the impact parameter effect is included in the final outcome (see the figure at right). The shapes of p, d and f-orbitals are described verbally here and shown graphically in the Orbitals table below. The three p-orbitals for have the form of two ellipsoids with a point of tangency at the nucleus (the two-lobed shape is sometimes referred to as a "dumbbell"—there are two lobes pointing in opposite directions from each other). The three p-orbitals in each shell are oriented at right angles to each other, as determined by their respective linear combination of values of . The overall result is a lobe pointing along each direction of the primary axes. Four of the five d-orbitals for look similar, each with four pear-shaped lobes, each lobe tangent at right angles to two others, and the centers of all four lying in one plane. Three of these planes are the xy-, xz-, and yz-planes—the lobes are between the pairs of primary axes—and the fourth has the centre along the x and y axes themselves. The fifth and final d-orbital consists of three regions of high probability density: a torus in between two pear-shaped regions placed symmetrically on its z axis. The overall total of 18 directional lobes point in every primary axis direction and between every pair. There are seven f-orbitals, each with shapes more complex than those of the d-orbitals. Additionally, as is the case with the s orbitals, individual p, d, f and g orbitals with values higher than the lowest possible value, exhibit an additional radial node structure which is reminiscent of harmonic waves of the same type, as compared with the lowest (or fundamental) mode of the wave. As with s orbitals, this phenomenon provides p, d, f, and g orbitals at the next higher possible value of (for example, 3p orbitals vs. the fundamental 2p), an additional node in each lobe. Still higher values of further increase the number of radial nodes, for each type of orbital. The shapes of atomic orbitals in one-electron atom are related to 3-dimensional spherical harmonics. These shapes are not unique, and any linear combination is valid, like a transformation to cubic harmonics, in fact it is possible to generate sets where all the d's are the same shape, just like the and are the same shape. Although individual orbitals are most often shown independent of each other, the orbitals coexist around the nucleus at the same time. Also, in 1927, Albrecht Unsöld proved that if one sums the electron density of all orbitals of a particular azimuthal quantum number of the same shell (e.g. all three 2p orbitals, or all five 3d orbitals) where each orbital is occupied by an electron or each is occupied by an electron pair, then all angular dependence disappears; that is, the resulting total density of all the atomic orbitals in that subshell (those with the same ) is spherical. This is known as Unsöld's theorem. Orbitals table This table shows all orbital configurations for the real hydrogen-like wave functions up to 7s, and therefore covers the simple electronic configuration for all elements in the periodic table up to radium. "ψ" graphs are shown with − and + wave function phases shown in two different colors (arbitrarily red and blue). The orbital is the same as the orbital, but the and are formed by taking linear combinations of the and orbitals (which is why they are listed under the label). Also, the and are not the same shape as the , since they are pure spherical harmonics. * No elements with this magnetic quantum number have been discovered yet. † The elements with this magnetic quantum number have been discovered, but their electronic configuration is only a prediction. ‡ The electronic configuration of the elements with this magnetic quantum number has only been confirmed for a spin quantum number of +1/2. These are the real-valued orbitals commonly used in chemistry. Only the orbitals where are eigenstates of the orbital angular momentum operator, . The columns with are contain combinations of two eigenstates. See comparison in the following picture: Qualitative understanding of shapes The shapes of atomic orbitals can be qualitatively understood by considering the analogous case of standing waves on a circular drum. To see the analogy, the mean vibrational displacement of each bit of drum membrane from the equilibrium point over many cycles (a measure of average drum membrane velocity and momentum at that point) must be considered relative to that point's distance from the center of the drum head. If this displacement is taken as being analogous to the probability of finding an electron at a given distance from the nucleus, then it will be seen that the many modes of the vibrating disk form patterns that trace the various shapes of atomic orbitals. The basic reason for this correspondence lies in the fact that the distribution of kinetic energy and momentum in a matter-wave is predictive of where the particle associated with the wave will be. That is, the probability of finding an electron at a given place is also a function of the electron's average momentum at that point, since high electron momentum at a given position tends to "localize" the electron in that position, via the properties of electron wave-packets (see the Heisenberg uncertainty principle for details of the mechanism). This relationship means that certain key features can be observed in both drum membrane modes and atomic orbitals. For example, in all of the modes analogous to s orbitals (the top row in the animated illustration below), it can be seen that the very center of the drum membrane vibrates most strongly, corresponding to the antinode in all s orbitals in an atom. This antinode means the electron is most likely to be at the physical position of the nucleus (which it passes straight through without scattering or striking it), since it is moving (on average) most rapidly at that point, giving it maximal momentum. A mental "planetary orbit" picture closest to the behavior of electrons in s orbitals, all of which have no angular momentum, might perhaps be that of a Keplerian orbit with the orbital eccentricity of 1 but a finite major axis, not physically possible (because particles were to collide), but can be imagined as a limit of orbits with equal major axes but increasing eccentricity. Below, a number of drum membrane vibration modes and the respective wave functions of the hydrogen atom are shown. A correspondence can be considered where the wave functions of a vibrating drum head are for a two-coordinate system and the wave functions for a vibrating sphere are three-coordinate . None of the other sets of modes in a drum membrane have a central antinode, and in all of them the center of the drum does not move. These correspond to a node at the nucleus for all non-s orbitals in an atom. These orbitals all have some angular momentum, and in the planetary model, they correspond to particles in orbit with eccentricity less than 1.0, so that they do not pass straight through the center of the primary body, but keep somewhat away from it. In addition, the drum modes analogous to p and d modes in an atom show spatial irregularity along the different radial directions from the center of the drum, whereas all of the modes analogous to s modes are perfectly symmetrical in radial direction. The non radial-symmetry properties of non-s orbitals are necessary to localize a particle with angular momentum and a wave nature in an orbital where it must tend to stay away from the central attraction force, since any particle localized at the point of central attraction could have no angular momentum. For these modes, waves in the drum head tend to avoid the central point. Such features again emphasize that the shapes of atomic orbitals are a direct consequence of the wave nature of electrons. Orbital energy In atoms with a single electron (hydrogen-like atoms), the energy of an orbital (and, consequently, of any electrons in the orbital) is determined mainly by . The orbital has the lowest possible energy in the atom. Each successively higher value of has a higher level of energy, but the difference decreases as increases. For high , the level of energy becomes so high that the electron can easily escape from the atom. In single electron atoms, all levels with different within a given are degenerate in the Schrödinger approximation, and have the same energy. This approximation is broken to a slight extent in the solution to the Dirac equation (where the energy depends on and another quantum number ), and by the effect of the magnetic field of the nucleus and quantum electrodynamics effects. The latter induce tiny binding energy differences especially for s electrons that go nearer the nucleus, since these feel a very slightly different nuclear charge, even in one-electron atoms; see Lamb shift. In atoms with multiple electrons, the energy of an electron depends not only on the intrinsic properties of its orbital, but also on its interactions with the other electrons. These interactions depend on the detail of its spatial probability distribution, and so the energy levels of orbitals depend not only on but also on . Higher values of are associated with higher values of energy; for instance, the 2p state is higher than the 2s state. When , the increase in energy of the orbital becomes so large as to push the energy of orbital above the energy of the s-orbital in the next higher shell; when the energy is pushed into the shell two steps higher. The filling of the 3d orbitals does not occur until the 4s orbitals have been filled. The increase in energy for subshells of increasing angular momentum in larger atoms is due to electron–electron interaction effects, and it is specifically related to the ability of low angular momentum electrons to penetrate more effectively toward the nucleus, where they are subject to less screening from the charge of intervening electrons. Thus, in atoms of higher atomic number, the of electrons becomes more and more of a determining factor in their energy, and the principal quantum numbers of electrons becomes less and less important in their energy placement. The energy sequence of the first 35 subshells (e.g., 1s, 2p, 3d, etc.) is given in the following table. Each cell represents a subshell with and given by its row and column indices, respectively. The number in the cell is the subshell's position in the sequence. For a linear listing of the subshells in terms of increasing energies in multielectron atoms, see the section below. Note: empty cells indicate non-existent sublevels, while numbers in italics indicate sublevels that could (potentially) exist, but which do not hold electrons in any element currently known. Electron placement and the periodic table Several rules govern the placement of electrons in orbitals (electron configuration). The first dictates that no two electrons in an atom may have the same set of values of quantum numbers (this is the Pauli exclusion principle). These quantum numbers include the three that define orbitals, as well as , or spin quantum number. Thus, two electrons may occupy a single orbital, so long as they have different values of . However, only two electrons, because of their spin, can be associated with each orbital. Additionally, an electron always tends to fall to the lowest possible energy state. It is possible for it to occupy any orbital so long as it does not violate the Pauli exclusion principle, but if lower-energy orbitals are available, this condition is unstable. The electron will eventually lose energy (by releasing a photon) and drop into the lower orbital. Thus, electrons fill orbitals in the order specified by the energy sequence given above. This behavior is responsible for the structure of the periodic table. The table may be divided into several rows (called 'periods'), numbered starting with 1 at the top. The presently known elements occupy seven periods. If a certain period has number i, it consists of elements whose outermost electrons fall in the ith shell. Niels Bohr was the first to propose (1923) that the periodicity in the properties of the elements might be explained by the periodic filling of the electron energy levels, resulting in the electronic structure of the atom. The periodic table may also be divided into several numbered rectangular 'blocks'. The elements belonging to a given block have this common feature: their highest-energy electrons all belong to the same -state (but the associated with that -state depends upon the period). For instance, the leftmost two columns constitute the 's-block'. The outermost electrons of Li and Be respectively belong to the 2s subshell, and those of Na and Mg to the 3s subshell. The following is the order for filling the "subshell" orbitals, which also gives the order of the "blocks" in the periodic table: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d, and f "blocks", is more obvious if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements: Although this is the general order of orbital filling according to the Madelung rule, there are exceptions, and the actual electronic energies of each element are also dependent upon additional details of the atoms (see ). The number of electrons in an electrically neutral atom increases with the atomic number. The electrons in the outermost shell, or valence electrons, tend to be responsible for an element's chemical behavior. Elements that contain the same number of valence electrons can be grouped together and display similar chemical properties. Relativistic effects For elements with high atomic number , the effects of relativity become more pronounced, and especially so for s electrons, which move at relativistic velocities as they penetrate the screening electrons near the core of high- atoms. This relativistic increase in momentum for high speed electrons causes a corresponding decrease in wavelength and contraction of 6s orbitals relative to 5d orbitals (by comparison to corresponding s and d electrons in lighter elements in the same column of the periodic table); this results in 6s valence electrons becoming lowered in energy. Examples of significant physical outcomes of this effect include the lowered melting temperature of mercury (which results from 6s electrons not being available for metal bonding) and the golden color of gold and caesium. In the Bohr Model, an  electron has a velocity given by , where is the atomic number, is the fine-structure constant, and is the speed of light. In non-relativistic quantum mechanics, therefore, any atom with an atomic number greater than 137 would require its 1s electrons to be traveling faster than the speed of light. Even in the Dirac equation, which accounts for relativistic effects, the wave function of the electron for atoms with is oscillatory and unbounded. The significance of element 137, also known as untriseptium, was first pointed out by the physicist Richard Feynman. Element 137 is sometimes informally called feynmanium (symbol Fy). However, Feynman's approximation fails to predict the exact critical value of  due to the non-point-charge nature of the nucleus and very small orbital radius of inner electrons, resulting in a potential seen by inner electrons which is effectively less than . The critical  value, which makes the atom unstable with regard to high-field breakdown of the vacuum and production of electron-positron pairs, does not occur until is about 173. These conditions are not seen except transiently in collisions of very heavy nuclei such as lead or uranium in accelerators, where such electron-positron production from these effects has been claimed to be observed. There are no nodes in relativistic orbital densities, although individual components of the wave function will have nodes. pp hybridisation (conjectured) In late period-8 elements a hybrid of 8p3/2 and 9p1/2 is expected to exist, where "3/2" and "1/2" refer to the total angular momentum quantum number. This "pp" hybrid may be responsible for the p-block of the period due to properties similar to p subshells in ordinary valence shells. Energy levels of 8p3/2 and 9p1/2 come close due to relativistic spin–orbit effects; the 9s subshell should also participate, as these elements are expected to be analogous to the respective 5p elements indium through xenon. Transitions between orbitals Bound quantum states have discrete energy levels. When applied to atomic orbitals, this means that the energy differences between states are also discrete. A transition between these states (i.e., an electron absorbing or emitting a photon) can thus only happen if the photon has an energy corresponding with the exact energy difference between said states. Consider two states of the hydrogen atom: State , , and State , , and By quantum theory, state 1 has a fixed energy of , and state 2 has a fixed energy of . Now, what would happen if an electron in state 1 were to move to state 2? For this to happen, the electron would need to gain an energy of exactly . If the electron receives energy that is less than or greater than this value, it cannot jump from state 1 to state 2. Now, suppose we irradiate the atom with a broad-spectrum of light. Photons that reach the atom that have an energy of exactly will be absorbed by the electron in state 1, and that electron will jump to state 2. However, photons that are greater or lower in energy cannot be absorbed by the electron, because the electron can only jump to one of the orbitals, it cannot jump to a state between orbitals. The result is that only photons of a specific frequency will be absorbed by the atom. This creates a line in the spectrum, known as an absorption line, which corresponds to the energy difference between states 1 and 2. The atomic orbital model thus predicts line spectra, which are observed experimentally. This is one of the main validations of the atomic orbital model. The atomic orbital model is nevertheless an approximation to the full quantum theory, which only recognizes many electron states. The predictions of line spectra are qualitatively useful but are not quantitatively accurate for atoms and ions other than those containing only one electron. See also Atomic electron configuration table Wiswesser's rule Condensed matter physics Electron configuration Energy level Hund's rules Molecular orbital Quantum chemistry Quantum chemistry computer programs Solid state physics Wave function collapse Notes References External links 3D hydrogen orbitals on Wikimedia Commons Guide to atomic orbitals Covalent Bonds and Molecular Structure Animation of the time evolution of an hydrogenic orbital The Orbitron, a visualization of all common and uncommon atomic orbitals, from 1s to 7g Grand table Still images of many orbitals Atomic physics Chemical bonding Electron states Quantum chemistry Articles containing video clips

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1208

https://en.wikipedia.org/wiki/Alan%20Turing

Alan Turing

Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer. Turing is widely considered to be the father of theoretical computer science and artificial intelligence. Born in Maida Vale, London, Turing was raised in southern England. He graduated at King's College, Cambridge, with a degree in mathematics. Whilst he was a fellow at Cambridge, he published a proof demonstrating that some purely mathematical yes–no questions can never be answered by computation and defined a Turing machine, and went on to prove the halting problem for Turing machines is undecidable. In 1938, he obtained his PhD from the Department of Mathematics at Princeton University. During the Second World War, Turing worked for the Government Code and Cypher School (GC&CS) at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. For a time he led Hut 8, the section that was responsible for German naval cryptanalysis. Here, he devised a number of techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bombe method, an electromechanical machine that could find settings for the Enigma machine. Turing played a crucial role in cracking intercepted coded messages that enabled the Allies to defeat the Axis powers in many crucial engagements, including the Battle of the Atlantic. After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine (ACE), one of the first designs for a stored-program computer. In 1948, Turing joined Max Newman's Computing Machine Laboratory, at the Victoria University of Manchester, where he helped develop the Manchester computers and became interested in mathematical biology. He wrote a paper on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s. Despite these accomplishments, he was never fully recognised in his home country during his lifetime because much of his work was covered by the Official Secrets Act. Turing was prosecuted in 1952 for homosexual acts. He accepted hormone treatment with DES, so-called chemical castration, as an alternative to prison. In 2009, following an Internet campaign, British Prime Minister Gordon Brown made an official public apology on behalf of the British government for "the appalling way he was treated". Queen Elizabeth II granted Turing a posthumous pardon in 2013. The "Alan Turing law" is now an informal term for a 2017 law in the United Kingdom that retroactively pardoned men cautioned or convicted under historical legislation that outlawed homosexual acts. Turing died in 1954, 16 days before his 42nd birthday, from cyanide poisoning. An inquest determined his death as a suicide, but it has been noted that the known evidence is also consistent with accidental poisoning. Turing has an extensive legacy with statues of him and many things named after him, including an annual award for computer science innovations. He appears on the current Bank of England £50 note, which was released to coincide with his birthday. A 2019 BBC series, as voted by the audience, named him the greatest person of the 20th century. Early life and education Family Turing was born in Maida Vale, London, while his father, Julius Mathison Turing (1873–1947), was on leave from his position with the Indian Civil Service (ICS) at Chatrapur, then in the Madras Presidency and presently in Odisha state, in India. Turing's father was the son of a clergyman, the Rev. John Robert Turing, from a Scottish family of merchants that had been based in the Netherlands and included a baronet. Turing's mother, Julius's wife, was Ethel Sara Turing (; 1881–1976), daughter of Edward Waller Stoney, chief engineer of the Madras Railways. The Stoneys were a Protestant Anglo-Irish gentry family from both County Tipperary and County Longford, while Ethel herself had spent much of her childhood in County Clare. Julius's work with the ICS brought the family to British India, where his grandfather had been a general in the Bengal Army. However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to Maida Vale, London, where Alan Turing was born on 23 June 1912, as recorded by a blue plaque on the outside of the house of his birth, later the Colonnade Hotel. Turing had an elder brother, John (the father of Sir John Dermot Turing, 12th Baronet of the Turing baronets). Turing's father's civil service commission was still active and during Turing's childhood years, his parents travelled between Hastings in the United Kingdom and India, leaving their two sons to stay with a retired Army couple. At Hastings, Turing stayed at Baston Lodge, Upper Maze Hill, St Leonards-on-Sea, now marked with a blue plaque. The plaque was unveiled on 23 June 2012, the centenary of Turing's birth. Very early in life, Turing showed signs of the genius that he was later to display prominently. His parents purchased a house in Guildford in 1927, and Turing lived there during school holidays. The location is also marked with a blue plaque. School Turing's parents enrolled him at St Michael's, a primary school at 20 Charles Road, St Leonards-on-Sea, from the age of six to nine. The headmistress recognised his talent, noting that she has "...had clever boys and hardworking boys, but Alan is a genius." Between January 1922 and 1926, Turing was educated at Hazelhurst Preparatory School, an independent school in the village of Frant in Sussex (now East Sussex). In 1926, at the age of 13, he went on to Sherborne School, a boarding independent school in the market town of Sherborne in Dorset, where he boarded at Westcott House. The first day of term coincided with the 1926 General Strike, in Britain, but Turing was so determined to attend, that he rode his bicycle unaccompanied from Southampton to Sherborne, stopping overnight at an inn. Turing's natural inclination towards mathematics and science did not earn him respect from some of the teachers at Sherborne, whose definition of education placed more emphasis on the classics. His headmaster wrote to his parents: "I hope he will not fall between two stools. If he is to stay at public school, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a public school". Despite this, Turing continued to show remarkable ability in the studies he loved, solving advanced problems in 1927 without having studied even elementary calculus. In 1928, aged 16, Turing encountered Albert Einstein's work; not only did he grasp it, but it is possible that he managed to deduce Einstein's questioning of Newton's laws of motion from a text in which this was never made explicit. Christopher Morcom At Sherborne, Turing formed a significant friendship with fellow pupil Christopher Collan Morcom (13 July 1911 – 13 February 1930), who has been described as Turing's "first love". Their relationship provided inspiration in Turing's future endeavours, but it was cut short by Morcom's death, in February 1930, from complications of bovine tuberculosis, contracted after drinking infected cow's milk some years previously. The event caused Turing great sorrow. He coped with his grief by working that much harder on the topics of science and mathematics that he had shared with Morcom. In a letter to Morcom's mother, Frances Isobel Morcom (née Swan), Turing wrote: Turing's relationship with Morcom's mother continued long after Morcom's death, with her sending gifts to Turing, and him sending letters, typically on Morcom's birthday. A day before the third anniversary of Morcom's death (13 February 1933), he wrote to Mrs. Morcom: Some have speculated that Morcom's death was the cause of Turing's atheism and materialism. Apparently, at this point in his life he still believed in such concepts as a spirit, independent of the body and surviving death. In a later letter, also written to Morcom's mother, Turing wrote: University and work on computability After Sherborne, Turing studied as an undergraduate from 1931 to 1934 at King's College, Cambridge, where he was awarded first-class honours in mathematics. In 1935, at the age of 22, he was elected a Fellow of King's College on the strength of a dissertation in which he proved the central limit theorem. Unknown to the committee, the theorem had already been proven, in 1922, by Jarl Waldemar Lindeberg. In 1936, Turing published his paper "On Computable Numbers, with an Application to the Entscheidungsproblem". It was published in the Proceedings of the London Mathematical Society journal in two parts, the first on 30 November and the second on 23 December. In this paper, Turing reformulated Kurt Gödel's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines. The Entscheidungsproblem (decision problem) was originally posed by German mathematician David Hilbert in 1928. Turing proved that his "universal computing machine" would be capable of performing any conceivable mathematical computation if it were representable as an algorithm. He went on to prove that there was no solution to the decision problem by first showing that the halting problem for Turing machines is undecidable: it is not possible to decide algorithmically whether a Turing machine will ever halt. This paper has been called "easily the most influential math paper in history". Although Turing's proof was published shortly after Alonzo Church's equivalent proof using his lambda calculus, Turing's approach is considerably more accessible and intuitive than Church's. It also included a notion of a 'Universal Machine' (now known as a universal Turing machine), with the idea that such a machine could perform the tasks of any other computation machine (as indeed could Church's lambda calculus). According to the Church–Turing thesis, Turing machines and the lambda calculus are capable of computing anything that is computable. John von Neumann acknowledged that the central concept of the modern computer was due to Turing's paper. To this day, Turing machines are a central object of study in theory of computation. From September 1936 to July 1938, Turing spent most of his time studying under Church at Princeton University, in the second year as a Jane Eliza Procter Visiting Fellow. In addition to his purely mathematical work, he studied cryptology and also built three of four stages of an electro-mechanical binary multiplier. In June 1938, he obtained his PhD from the Department of Mathematics at Princeton; his dissertation, Systems of Logic Based on Ordinals, introduced the concept of ordinal logic and the notion of relative computing, in which Turing machines are augmented with so-called oracles, allowing the study of problems that cannot be solved by Turing machines. John von Neumann wanted to hire him as his postdoctoral assistant, but he went back to the United Kingdom. Career and research When Turing returned to Cambridge, he attended lectures given in 1939 by Ludwig Wittgenstein about the foundations of mathematics. The lectures have been reconstructed verbatim, including interjections from Turing and other students, from students' notes. Turing and Wittgenstein argued and disagreed, with Turing defending formalism and Wittgenstein propounding his view that mathematics does not discover any absolute truths, but rather invents them. Cryptanalysis During the Second World War, Turing was a leading participant in the breaking of German ciphers at Bletchley Park. The historian and wartime codebreaker Asa Briggs has said, "You needed exceptional talent, you needed genius at Bletchley and Turing's was that genius." From September 1938, Turing worked part-time with the Government Code and Cypher School (GC&CS), the British codebreaking organisation. He concentrated on cryptanalysis of the Enigma cipher machine used by Nazi Germany, together with Dilly Knox, a senior GC&CS codebreaker. Soon after the July 1939 meeting near Warsaw at which the Polish Cipher Bureau gave the British and French details of the wiring of Enigma machine's rotors and their method of decrypting Enigma machine's messages, Turing and Knox developed a broader solution. The Polish method relied on an insecure indicator procedure that the Germans were likely to change, which they in fact did in May 1940. Turing's approach was more general, using crib-based decryption for which he produced the functional specification of the bombe (an improvement on the Polish Bomba). On 4 September 1939, the day after the UK declared war on Germany, Turing reported to Bletchley Park, the wartime station of GC&CS. Like all others who came to Bletchley, he was required to sign the Official Secrets Act, in which he agreed not to disclose anything about his work at Bletchley, with severe legal penalties for violating the Act. Specifying the bombe was the first of five major cryptanalytical advances that Turing made during the war. The others were: deducing the indicator procedure used by the German navy; developing a statistical procedure dubbed Banburismus for making much more efficient use of the bombes; developing a procedure dubbed Turingery for working out the cam settings of the wheels of the Lorenz SZ 40/42 (Tunny) cipher machine and, towards the end of the war, the development of a portable secure voice scrambler at Hanslope Park that was codenamed Delilah. By using statistical techniques to optimise the trial of different possibilities in the code breaking process, Turing made an innovative contribution to the subject. He wrote two papers discussing mathematical approaches, titled The Applications of Probability to Cryptography and Paper on Statistics of Repetitions, which were of such value to GC&CS and its successor GCHQ that they were not released to the UK National Archives until April 2012, shortly before the centenary of his birth. A GCHQ mathematician, "who identified himself only as Richard," said at the time that the fact that the contents had been restricted under the Official Secrets Act for some 70 years demonstrated their importance, and their relevance to post-war cryptanalysis: Turing had a reputation for eccentricity at Bletchley Park. He was known to his colleagues as "Prof" and his treatise on Enigma was known as the "Prof's Book". According to historian Ronald Lewin, Jack Good, a cryptanalyst who worked with Turing, said of his colleague: Peter Hilton recounted his experience working with Turing in Hut 8 in his "Reminiscences of Bletchley Park" from A Century of Mathematics in America: Hilton echoed similar thoughts in the Nova PBS documentary Decoding Nazi Secrets. While working at Bletchley, Turing, who was a talented long-distance runner, occasionally ran the to London when he was needed for meetings, and he was capable of world-class marathon standards. Turing tried out for the 1948 British Olympic team, but he was hampered by an injury. His tryout time for the marathon was only 11 minutes slower than British silver medallist Thomas Richards' Olympic race time of 2 hours 35 minutes. He was Walton Athletic Club's best runner, a fact discovered when he passed the group while running alone. When asked why he ran so hard in training he replied: Due to the problems of counterfactual history, it is hard to estimate the precise effect Ultra intelligence had on the war. However, official war historian Harry Hinsley estimated that this work shortened the war in Europe by more than two years and saved over 14 million lives. At the end of the war, a memo was sent to all those who had worked at Bletchley Park, reminding them that the code of silence dictated by the Official Secrets Act did not end with the war but would continue indefinitely. Thus, even though Turing was appointed an Officer of the Order of the British Empire (OBE) in 1946 by King George VI for his wartime services, his work remained secret for many years. Bombe Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine called the bombe, which could break Enigma more effectively than the Polish bomba kryptologiczna, from which its name was derived. The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-enciphered messages. The bombe searched for possible correct settings used for an Enigma message (i.e., rotor order, rotor settings and plugboard settings) using a suitable crib: a fragment of probable plaintext. For each possible setting of the rotors (which had on the order of 1019 states, or 1022 states for the four-rotor U-boat variant), the bombe performed a chain of logical deductions based on the crib, implemented electromechanically. The bombe detected when a contradiction had occurred and ruled out that setting, moving on to the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. A contradiction would occur when an enciphered letter would be turned back into the same plaintext letter, which was impossible with the Enigma. The first bombe was installed on 18 March 1940. By late 1941, Turing and his fellow cryptanalysts Gordon Welchman, Hugh Alexander and Stuart Milner-Barry were frustrated. Building on the work of the Poles, they had set up a good working system for decrypting Enigma signals, but their limited staff and bombes meant they could not translate all the signals. In the summer, they had considerable success, and shipping losses had fallen to under 100,000 tons a month; however, they badly needed more resources to keep abreast of German adjustments. They had tried to get more people and fund more bombes through the proper channels, but had failed. On 28 October they wrote directly to Winston Churchill explaining their difficulties, with Turing as the first named. They emphasised how small their need was compared with the vast expenditure of men and money by the forces and compared with the level of assistance they could offer to the forces. As Andrew Hodges, biographer of Turing, later wrote, "This letter had an electric effect." Churchill wrote a memo to General Ismay, which read: "ACTION THIS DAY. Make sure they have all they want on extreme priority and report to me that this has been done." On 18 November, the chief of the secret service reported that every possible measure was being taken. The cryptographers at Bletchley Park did not know of the Prime Minister's response, but as Milner-Barry recalled, "All that we did notice was that almost from that day the rough ways began miraculously to be made smooth." More than two hundred bombes were in operation by the end of the war. Hut 8 and the naval Enigma Turing decided to tackle the particularly difficult problem of German naval Enigma "because no one else was doing anything about it and I could have it to myself". In December 1939, Turing solved the essential part of the naval indicator system, which was more complex than the indicator systems used by the other services. That same night, he also conceived of the idea of Banburismus, a sequential statistical technique (what Abraham Wald later called sequential analysis) to assist in breaking the naval Enigma, "though I was not sure that it would work in practice, and was not, in fact, sure until some days had actually broken." For this, he invented a measure of weight of evidence that he called the ban. Banburismus could rule out certain sequences of the Enigma rotors, substantially reducing the time needed to test settings on the bombes. Later this sequential process of accumulating sufficient weight of evidence using decibans (one tenth of a ban) was used in Cryptanalysis of the Lorenz cipher. Turing travelled to the United States in November 1942 and worked with US Navy cryptanalysts on the naval Enigma and bombe construction in Washington; he also visited their Computing Machine Laboratory in Dayton, Ohio. Turing's reaction to the American bombe design was far from enthusiastic: During this trip, he also assisted at Bell Labs with the development of secure speech devices. He returned to Bletchley Park in March 1943. During his absence, Hugh Alexander had officially assumed the position of head of Hut 8, although Alexander had been de facto head for some time (Turing having little interest in the day-to-day running of the section). Turing became a general consultant for cryptanalysis at Bletchley Park. Alexander wrote of Turing's contribution: Turingery In July 1942, Turing devised a technique termed Turingery (or jokingly Turingismus) for use against the Lorenz cipher messages produced by the Germans' new Geheimschreiber (secret writer) machine. This was a teleprinter rotor cipher attachment codenamed Tunny at Bletchley Park. Turingery was a method of wheel-breaking, i.e., a procedure for working out the cam settings of Tunny's wheels. He also introduced the Tunny team to Tommy Flowers who, under the guidance of Max Newman, went on to build the Colossus computer, the world's first programmable digital electronic computer, which replaced a simpler prior machine (the Heath Robinson), and whose superior speed allowed the statistical decryption techniques to be applied usefully to the messages. Some have mistakenly said that Turing was a key figure in the design of the Colossus computer. Turingery and the statistical approach of Banburismus undoubtedly fed into the thinking about cryptanalysis of the Lorenz cipher, but he was not directly involved in the Colossus development. Delilah Following his work at Bell Labs in the US, Turing pursued the idea of electronic enciphering of speech in the telephone system. In the latter part of the war, he moved to work for the Secret Service's Radio Security Service (later HMGCC) at Hanslope Park. At the park, he further developed his knowledge of electronics with the assistance of engineer Donald Bayley. Together they undertook the design and construction of a portable secure voice communications machine codenamed Delilah. The machine was intended for different applications, but it lacked the capability for use with long-distance radio transmissions. In any case, Delilah was completed too late to be used during the war. Though the system worked fully, with Turing demonstrating it to officials by encrypting and decrypting a recording of a Winston Churchill speech, Delilah was not adopted for use. Turing also consulted with Bell Labs on the development of SIGSALY, a secure voice system that was used in the later years of the war. Early computers and the Turing test Between 1945 and 1947, Turing lived in Hampton, London, while he worked on the design of the ACE (Automatic Computing Engine) at the National Physical Laboratory (NPL). He presented a paper on 19 February 1946, which was the first detailed design of a stored-program computer. Von Neumann's incomplete First Draft of a Report on the EDVAC had predated Turing's paper, but it was much less detailed and, according to John R. Womersley, Superintendent of the NPL Mathematics Division, it "contains a number of ideas which are Dr. Turing's own". Although ACE was a feasible design, the effect of the Official Secrets Act surrounding the wartime work at Bletchley Park made it impossible for Turing to explain the basis of his analysis of how a computer installation involving human operators would work. This led to delays in starting the project and he became disillusioned. In late 1947 he returned to Cambridge for a sabbatical year during which he produced a seminal work on Intelligent Machinery that was not published in his lifetime. While he was at Cambridge, the Pilot ACE was being built in his absence. It executed its first program on 10 May 1950, and a number of later computers around the world owe much to it, including the English Electric DEUCE and the American Bendix G-15. The full version of Turing's ACE was not built until after his death. According to the memoirs of the German computer pioneer Heinz Billing from the Max Planck Institute for Physics, published by Genscher, Düsseldorf, there was a meeting between Turing and Konrad Zuse. It took place in Göttingen in 1947. The interrogation had the form of a colloquium. Participants were Womersley, Turing, Porter from England and a few German researchers like Zuse, Walther, and Billing (for more details see Herbert Bruderer, Konrad Zuse und die Schweiz). In 1948, Turing was appointed reader in the Mathematics Department at the Victoria University of Manchester. A year later, he became deputy director of the Computing Machine Laboratory, where he worked on software for one of the earliest stored-program computers—the Manchester Mark 1. Turing wrote the first version of the Programmer's Manual for this machine, and was recruited by Ferranti as a consultant in the development of their commercialised machine, the Ferranti Mark 1. He continued to be paid consultancy fees by Ferranti until his death. During this time, he continued to do more abstract work in mathematics, and in "Computing Machinery and Intelligence" (Mind, October 1950), Turing addressed the problem of artificial intelligence, and proposed an experiment that became known as the Turing test, an attempt to define a standard for a machine to be called "intelligent". The idea was that a computer could be said to "think" if a human interrogator could not tell it apart, through conversation, from a human being. In the paper, Turing suggested that rather than building a program to simulate the adult mind, it would be better to produce a simpler one to simulate a child's mind and then to subject it to a course of education. A reversed form of the Turing test is widely used on the Internet; the CAPTCHA test is intended to determine whether the user is a human or a computer. In 1948, Turing, working with his former undergraduate colleague, D.G. Champernowne, began writing a chess program for a computer that did not yet exist. By 1950, the program was completed and dubbed the Turochamp. In 1952, he tried to implement it on a Ferranti Mark 1, but lacking enough power, the computer was unable to execute the program. Instead, Turing "ran" the program by flipping through the pages of the algorithm and carrying out its instructions on a chessboard, taking about half an hour per move. The game was recorded. According to Garry Kasparov, Turing's program "played a recognizable game of chess." The program lost to Turing's colleague Alick Glennie, although it is said that it won a game against Champernowne's wife, Isabel. His Turing test was a significant, characteristically provocative, and lasting contribution to the debate regarding artificial intelligence, which continues after more than half a century. Pattern formation and mathematical biology When Turing was 39 years old in 1951, he turned to mathematical biology, finally publishing his masterpiece "The Chemical Basis of Morphogenesis" in January 1952. He was interested in morphogenesis, the development of patterns and shapes in biological organisms. He suggested that a system of chemicals reacting with each other and diffusing across space, termed a reaction–diffusion system, could account for "the main phenomena of morphogenesis". He used systems of partial differential equations to model catalytic chemical reactions. For example, if a catalyst A is required for a certain chemical reaction to take place, and if the reaction produced more of the catalyst A, then we say that the reaction is autocatalytic, and there is positive feedback that can be modelled by nonlinear differential equations. Turing discovered that patterns could be created if the chemical reaction not only produced catalyst A, but also produced an inhibitor B that slowed down the production of A. If A and B then diffused through the container at different rates, then you could have some regions where A dominated and some where B did. To calculate the extent of this, Turing would have needed a powerful computer, but these were not so freely available in 1951, so he had to use linear approximations to solve the equations by hand. These calculations gave the right qualitative results, and produced, for example, a uniform mixture that oddly enough had regularly spaced fixed red spots. The Russian biochemist Boris Belousov had performed experiments with similar results, but could not get his papers published because of the contemporary prejudice that any such thing violated the second law of thermodynamics. Belousov was not aware of Turing's paper in the Philosophical Transactions of the Royal Society. Although published before the structure and role of DNA was understood, Turing's work on morphogenesis remains relevant today and is considered a seminal piece of work in mathematical biology. One of the early applications of Turing's paper was the work by James Murray explaining spots and stripes on the fur of cats, large and small. Further research in the area suggests that Turing's work can partially explain the growth of "feathers, hair follicles, the branching pattern of lungs, and even the left-right asymmetry that puts the heart on the left side of the chest." In 2012, Sheth, et al. found that in mice, removal of Hox genes causes an increase in the number of digits without an increase in the overall size of the limb, suggesting that Hox genes control digit formation by tuning the wavelength of a Turing-type mechanism. Later papers were not available until Collected Works of A. M. Turing was published in 1992. Personal life Engagement In 1941, Turing proposed marriage to Hut 8 colleague Joan Clarke, a fellow mathematician and cryptanalyst, but their engagement was short-lived. After admitting his homosexuality to his fiancée, who was reportedly "unfazed" by the revelation, Turing decided that he could not go through with the marriage. Conviction for indecency In January 1952, Turing was 39 when he started a relationship with Arnold Murray, a 19-year-old unemployed man. Just before Christmas, Turing was walking along Manchester's Oxford Road when he met Murray just outside the Regal Cinema and invited him to lunch. On 23 January, Turing's house was burgled. Murray told Turing that he and the burglar were acquainted, and Turing reported the crime to the police. During the investigation, he acknowledged a sexual relationship with Murray. Homosexual acts were criminal offences in the United Kingdom at that time, and both men were charged with "gross indecency" under Section 11 of the Criminal Law Amendment Act 1885. Initial committal proceedings for the trial were held on 27 February during which Turing's solicitor "reserved his defence", i.e., did not argue or provide evidence against the allegations. Turing was later convinced by the advice of his brother and his own solicitor, and he entered a plea of guilty. The case, Regina v. Turing and Murray, was brought to trial on 31 March 1952. Turing was convicted and given a choice between imprisonment and probation. His probation would be conditional on his agreement to undergo hormonal physical changes designed to reduce libido. He accepted the option of injections of what was then called stilboestrol (now known as diethylstilbestrol or DES), a synthetic oestrogen; this feminization of his body was continued for the course of one year. The treatment rendered Turing impotent and caused breast tissue to form, fulfilling in the literal sense Turing's prediction that "no doubt I shall emerge from it all a different man, but quite who I've not found out". Murray was given a conditional discharge. Turing's conviction led to the removal of his security clearance and barred him from continuing with his cryptographic consultancy for the Government Communications Headquarters (GCHQ), the British signals intelligence agency that had evolved from GC&CS in 1946, though he kept his academic job. He was denied entry into the United States after his conviction in 1952, but was free to visit other European countries. Death On 8 June 1954, at his house at 43 Adlington Road, Wilmslow, Turing's housekeeper found him dead. He had died the previous day at the age of 41. Cyanide poisoning was established as the cause of death. When his body was discovered, an apple lay half-eaten beside his bed, and although the apple was not tested for cyanide, it was speculated that this was the means by which Turing had consumed a fatal dose. An inquest determined that he had committed suicide. Andrew Hodges and another biographer, David Leavitt, have both speculated that Turing was re-enacting a scene from the Walt Disney film Snow White and the Seven Dwarfs (1937), his favourite fairy tale. Both men noted that (in Leavitt's words) he took "an especially keen pleasure in the scene where the Wicked Queen immerses her apple in the poisonous brew". Turing's remains were cremated at Woking Crematorium on 12 June 1954, and his ashes were scattered in the gardens of the crematorium, just as his father's had been. Philosopher Jack Copeland has questioned various aspects of the coroner's historical verdict. He suggested an alternative explanation for the cause of Turing's death: the accidental inhalation of cyanide fumes from an apparatus used to electroplate gold onto spoons. The potassium cyanide was used to dissolve the gold. Turing had such an apparatus set up in his tiny spare room. Copeland noted that the autopsy findings were more consistent with inhalation than with ingestion of the poison. Turing also habitually ate an apple before going to bed, and it was not unusual for the apple to be discarded half-eaten. Furthermore, Turing had reportedly borne his legal setbacks and hormone treatment (which had been discontinued a year previously) "with good humour" and had shown no sign of despondency prior to his death. He even set down a list of tasks that he intended to complete upon returning to his office after the holiday weekend. Turing's mother believed that the ingestion was accidental, resulting from her son's careless storage of laboratory chemicals. Biographer Andrew Hodges theorised that Turing arranged the delivery of the equipment to deliberately allow his mother plausible deniability with regard to any suicide claims. It has been suggested that Turing's belief in fortune-telling may have caused his depressed mood. As a youth, Turing had been told by a fortune-teller that he would be a genius. In mid-May 1954, shortly before his death, Turing again decided to consult a fortune-teller during a day-trip to St Annes-on-Sea with the Greenbaum family. According to the Greenbaums' daughter, Barbara: But it was a lovely sunny day and Alan was in a cheerful mood and off we went... Then he thought it would be a good idea to go to the Pleasure Beach at Blackpool. We found a fortune-teller's tent[,] and Alan said he'd like to go in[,] so we waited around for him to come back... And this sunny, cheerful visage had shrunk into a pale, shaking, horror-stricken face. Something had happened. We don't know what the fortune-teller said[,] but he obviously was deeply unhappy. I think that was probably the last time we saw him before we heard of his suicide. Government apology and pardon In August 2009, British programmer John Graham-Cumming started a petition urging the British government to apologise for Turing's prosecution as a homosexual. The petition received more than 30,000 signatures. The Prime Minister, Gordon Brown, acknowledged the petition, releasing a statement on 10 September 2009 apologising and describing the treatment of Turing as "appalling": In December 2011, William Jones and his Member of Parliament, John Leech, created an e-petition requesting that the British government pardon Turing for his conviction of "gross indecency": The petition gathered over 37,000 signatures, and was submitted to Parliament by the Manchester MP John Leech but the request was discouraged by Justice Minister Lord McNally, who said: John Leech, the MP for Manchester Withington (2005–15), submitted several bills to Parliament and led a high-profile campaign to secure the pardon. Leech made the case in the House of Commons that Turing's contribution to the war made him a national hero and that it was "ultimately just embarrassing" that the conviction still stood. Leech continued to take the bill through Parliament and campaigned for several years, gaining the public support of numerous leading scientists, including Stephen Hawking. At the British premiere of a film based on Turing's life, The Imitation Game, the producers thanked Leech for bringing the topic to public attention and securing Turing's pardon. Leech is now regularly described as the "architect" of Turing's pardon and subsequently the Alan Turing Law which went on to secure pardons for 75,000 other men and women convicted of similar crimes. On 26 July 2012, a bill was introduced in the House of Lords to grant a statutory pardon to Turing for offences under section 11 of the Criminal Law Amendment Act 1885, of which he was convicted on 31 March 1952. Late in the year in a letter to The Daily Telegraph, the physicist Stephen Hawking and 10 other signatories including the Astronomer Royal Lord Rees, President of the Royal Society Sir Paul Nurse, Lady Trumpington (who worked for Turing during the war) and Lord Sharkey (the bill's sponsor) called on Prime Minister David Cameron to act on the pardon request. The government indicated it would support the bill, and it passed its third reading in the House of Lords in October. At the bill's second reading in the House of Commons on 29 November 2013, Conservative MP Christopher Chope objected to the bill, delaying its passage. The bill was due to return to the House of Commons on 28 February 2014, but before the bill could be debated in the House of Commons, the government elected to proceed under the royal prerogative of mercy. On 24 December 2013, Queen Elizabeth II signed a pardon for Turing's conviction for "gross indecency", with immediate effect. Announcing the pardon, Lord Chancellor Chris Grayling said Turing deserved to be "remembered and recognised for his fantastic contribution to the war effort" and not for his later criminal conviction. The Queen officially pronounced Turing pardoned in August 2014. The Queen's action is only the fourth royal pardon granted since the conclusion of the Second World War. Pardons are normally granted only when the person is technically innocent, and a request has been made by the family or other interested party; neither condition was met in regard to Turing's conviction. In September 2016, the government announced its intention to expand this retroactive exoneration to other men convicted of similar historical indecency offences, in what was described as an "Alan Turing law". The Alan Turing law is now an informal term for the law in the United Kingdom, contained in the Policing and Crime Act 2017, which serves as an amnesty law to retroactively pardon men who were cautioned or convicted under historical legislation that outlawed homosexual acts. The law applies in England and Wales. Legacy Awards, honours, and tributes Turing was appointed an officer of the Order of the British Empire in 1946. He was also elected a Fellow of the Royal Society (FRS) in 1951. Turing has been honoured in various ways in Manchester, the city where he worked towards the end of his life. In 1994, a stretch of the A6010 road (the Manchester city intermediate ring road) was named "Alan Turing Way". A bridge carrying this road was widened, and carries the name Alan Turing Bridge. A statue of Turing was unveiled in Manchester on 23 June 2001 in Sackville Park, between the University of Manchester building on Whitworth Street and Canal Street. The memorial statue depicts the "father of computer science" sitting on a bench at a central position in the park. Turing is shown holding an apple. The cast bronze bench carries in relief the text 'Alan Mathison Turing 1912–1954', and the motto 'Founder of Computer Science' as it could appear if encoded by an Enigma machine: 'IEKYF ROMSI ADXUO KVKZC GUBJ'. However, the meaning of the coded message is disputed, as the 'u' in 'computer' matches up with the 'u' in 'ADXUO'. As a letter encoded by an enigma machine cannot appear as itself, the actual message behind the code is uncertain. A plaque at the statue's feet reads 'Father of computer science, mathematician, logician, wartime codebreaker, victim of prejudice'. There is also a Bertrand Russell quotation: "Mathematics, rightly viewed, possesses not only truth, but supreme beauty—a beauty cold and austere, like that of sculpture." The sculptor buried his own old Amstrad computer under the plinth as a tribute to "the godfather of all modern computers". In 1999, Time magazine named Turing as one of the 100 Most Important People of the 20th century and stated, "The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine." A blue plaque was unveiled at King's College on the centenary of his birth on 23 June 2012 and is now installed at the college's Keynes Building on King's Parade. On 25 March 2021, the Bank of England publicly unveiled the design for a new £50 note, featuring Turing's portrait, before its official issue on 23 June, Turing's birthday. Turing was selected as the new face of the note in 2019 following a public nomination process. Centenary celebrations To mark the 100th anniversary of Turing's birth, the Turing Centenary Advisory Committee (TCAC) co-ordinated the Alan Turing Year in 2012, a year-long programme of events around the world honouring Turing's life and achievements. The TCAC, chaired by S. Barry Cooper with Turing's nephew Sir John Dermot Turing acting as Honorary President, worked with the University of Manchester faculty members and a broad spectrum of people from Cambridge University and Bletchley Park. Steel sculpture controversy In May 2020 it was reported by Gay Star News that a high steel sculpture, to honour Turing, designed by Sir Antony Gormley, was planned to be installed at King's College, Cambridge. Historic England, however, was quoted as saying that the abstract work of 19 steel slabs "... would be at odds with the existing character of the College. This would result in harm, of a less than substantial nature, to the significance of the listed buildings and landscape, and by extension the conservation area." References Sources Bruderer, Herbert: Konrad Zuse und die Schweiz. Wer hat den Computer erfunden? Charles Babbage, Alan Turing und John von Neumann Oldenbourg Verlag, München 2012, XXVI, 224 Seiten, in Petzold, Charles (2008). "The Annotated Turing: A Guided Tour through Alan Turing's Historic Paper on Computability and the Turing Machine". Indianapolis: Wiley Publishing. Smith, Roger (1997). Fontana History of the Human Sciences. London: Fontana. Weizenbaum, Joseph (1976). Computer Power and Human Reason. London: W.H. Freeman. and Turing's mother, who survived him by many years, wrote this 157-page biography of her son, glorifying his life. It was published in 1959, and so could not cover his war work. Scarcely 300 copies were sold (Sara Turing to Lyn Newman, 1967, Library of St John's College, Cambridge). The six-page foreword by Lyn Irvine includes reminiscences and is more frequently quoted. It was re-published by Cambridge University Press in 2012, to honour the centenary of his birth, and included a new foreword by Martin Davis, as well as a never-before-published memoir by Turing's older brother John F. Turing. This 1986 Hugh Whitemore play tells the story of Turing's life and death. In the original West End and Broadway runs, Derek Jacobi played Turing and he recreated the role in a 1997 television film based on the play made jointly by the BBC and WGBH, Boston. The play is published by Amber Lane Press, Oxford, ASIN: B000B7TM0Q Williams, Michael R. (1985) A History of Computing Technology, Englewood Cliffs, New Jersey: Prentice-Hall, Further reading Articles Books (originally published in 1983); basis of the film The Imitation Game (originally published in 1959 by W. Heffer & Sons, Ltd) External links Oral history interview with Nicholas C. Metropolis, Charles Babbage Institute, University of Minnesota. Metropolis was the first director of computing services at Los Alamos National Laboratory; topics include the relationship between Turing and John von Neumann How Alan Turing Cracked The Enigma Code Imperial War Museums Alan Turing RKBExplorer Alan Turing Year CiE 2012: Turing Centenary Conference Science in the Making Alan Turing's papers in the Royal Society's archives Alan Turing site maintained by Andrew Hodges including a short biography AlanTuring.net – Turing Archive for the History of Computing by Jack Copeland The Turing Archive – contains scans of some unpublished documents and material from the King's College, Cambridge archive Alan Turing Papers – University of Manchester Library, Manchester Sherborne School Archives – holds papers relating to Turing's time at Sherborne School Alan Turing plaques recorded on openplaques.org Alan Turing archive on New Scientist 1912 births 1954 deaths 1954 suicides 20th-century mathematicians 20th-century atheists 20th-century British scientists 20th-century English philosophers Academics of the University of Manchester Academics of the University of Manchester Institute of Science and Technology Alumni of King's College, Cambridge Artificial intelligence researchers Bayesian statisticians Bletchley Park people British anti-fascists British cryptographers British people of World War II Computability theorists Computer designers English atheists English computer scientists English inventors English logicians English male long-distance runners English mathematicians English people of Irish descent English people of Scottish descent Fellows of King's College, Cambridge Fellows of the Royal Society Former Protestants Foreign Office personnel of World War II Gay academics Gay scientists Gay sportsmen GCHQ people History of artificial intelligence History of computing in the United Kingdom LGBT-related suicides LGBT mathematicians LGBT philosophers LGBT scientists from the United Kingdom LGBT sportspeople from England LGBT track and field athletes Officers of the Order of the British Empire People educated at Sherborne School People from Maida Vale People from Wilmslow People convicted for homosexuality in the United Kingdom People who have received posthumous pardons Princeton University alumni Recipients of British royal pardons Suicides by cyanide poisoning Suicides in England Theoretical computer scientists Deaths by poisoning

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1209

https://en.wikipedia.org/wiki/Area

Area

Area is the quantity that expresses the extent of a two-dimensional region, shape, or planar lamina, in the plane. Surface area is its analog on the two-dimensional surface of a three-dimensional object. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat. It is the two-dimensional analog of the length of a curve (a one-dimensional concept) or the volume of a solid (a three-dimensional concept). The area of a shape can be measured by comparing the shape to squares of a fixed size. In the International System of Units (SI), the standard unit of area is the square metre (written as m2), which is the area of a square whose sides are one metre long. A shape with an area of three square metres would have the same area as three such squares. In mathematics, the unit square is defined to have area one, and the area of any other shape or surface is a dimensionless real number. There are several well-known formulas for the areas of simple shapes such as triangles, rectangles, and circles. Using these formulas, the area of any polygon can be found by dividing the polygon into triangles. For shapes with curved boundary, calculus is usually required to compute the area. Indeed, the problem of determining the area of plane figures was a major motivation for the historical development of calculus. For a solid shape such as a sphere, cone, or cylinder, the area of its boundary surface is called the surface area. Formulas for the surface areas of simple shapes were computed by the ancient Greeks, but computing the surface area of a more complicated shape usually requires multivariable calculus. Area plays an important role in modern mathematics. In addition to its obvious importance in geometry and calculus, area is related to the definition of determinants in linear algebra, and is a basic property of surfaces in differential geometry. In analysis, the area of a subset of the plane is defined using Lebesgue measure, though not every subset is measurable. In general, area in higher mathematics is seen as a special case of volume for two-dimensional regions. Area can be defined through the use of axioms, defining it as a function of a collection of certain plane figures to the set of real numbers. It can be proved that such a function exists. Formal definition An approach to defining what is meant by "area" is through axioms. "Area" can be defined as a function from a collection M of a special kinds of plane figures (termed measurable sets) to the set of real numbers, which satisfies the following properties: For all S in M, a(S) ≥ 0. If S and T are in M then so are S ∪ T and S ∩ T, and also a(S∪T) = a(S) + a(T) − a(S∩T). If S and T are in M with S ⊆ T then T − S is in M and a(T−S) = a(T) − a(S). If a set S is in M and S is congruent to T then T is also in M and a(S) = a(T). Every rectangle R is in M. If the rectangle has length h and breadth k then a(R) = hk. Let Q be a set enclosed between two step regions S and T. A step region is formed from a finite union of adjacent rectangles resting on a common base, i.e. S ⊆ Q ⊆ T. If there is a unique number c such that a(S) ≤ c ≤ a(T) for all such step regions S and T, then a(Q) = c. It can be proved that such an area function actually exists. Units Every unit of length has a corresponding unit of area, namely the area of a square with the given side length. Thus areas can be measured in square metres (m2), square centimetres (cm2), square millimetres (mm2), square kilometres (km2), square feet (ft2), square yards (yd2), square miles (mi2), and so forth. Algebraically, these units can be thought of as the squares of the corresponding length units. The SI unit of area is the square metre, which is considered an SI derived unit. Conversions Calculation of the area of a square whose length and width are 1 metre would be: 1 metre × 1 metre = 1 m2 and so, a rectangle with different sides (say length of 3 metres and width of 2 metres) would have an area in square units that can be calculated as: 3 metres × 2 metres = 6 m2. This is equivalent to 6 million square millimetres. Other useful conversions are: 1 square kilometre = 1,000,000 square metres 1 square metre = 10,000 square centimetres = 1,000,000 square millimetres 1 square centimetre = 100 square millimetres. Non-metric units In non-metric units, the conversion between two square units is the square of the conversion between the corresponding length units. 1 foot = 12 inches, the relationship between square feet and square inches is 1 square foot = 144 square inches, where 144 = 122 = 12 × 12. Similarly: 1 square yard = 9 square feet 1 square mile = 3,097,600 square yards = 27,878,400 square feet In addition, conversion factors include: 1 square inch = 6.4516 square centimetres 1 square foot = square metres 1 square yard = square metres 1 square mile = square kilometres Other units including historical There are several other common units for area. The are was the original unit of area in the metric system, with: 1 are = 100 square metres Though the are has fallen out of use, the hectare is still commonly used to measure land: 1 hectare = 100 ares = 10,000 square metres = 0.01 square kilometres Other uncommon metric units of area include the tetrad, the hectad, and the myriad. The acre is also commonly used to measure land areas, where 1 acre = 4,840 square yards = 43,560 square feet. An acre is approximately 40% of a hectare. On the atomic scale, area is measured in units of barns, such that: 1 barn = 10−28 square meters. The barn is commonly used in describing the cross-sectional area of interaction in nuclear physics. In India, 20 dhurki = 1 dhur 20 dhur = 1 khatha 20 khata = 1 bigha 32 khata = 1 acre History Circle area In the 5th century BCE, Hippocrates of Chios was the first to show that the area of a disk (the region enclosed by a circle) is proportional to the square of its diameter, as part of his quadrature of the lune of Hippocrates, but did not identify the constant of proportionality. Eudoxus of Cnidus, also in the 5th century BCE, also found that the area of a disk is proportional to its radius squared. Subsequently, Book I of Euclid's Elements dealt with equality of areas between two-dimensional figures. The mathematician Archimedes used the tools of Euclidean geometry to show that the area inside a circle is equal to that of a right triangle whose base has the length of the circle's circumference and whose height equals the circle's radius, in his book Measurement of a Circle. (The circumference is 2r, and the area of a triangle is half the base times the height, yielding the area r2 for the disk.) Archimedes approximated the value of π (and hence the area of a unit-radius circle) with his doubling method, in which he inscribed a regular triangle in a circle and noted its area, then doubled the number of sides to give a regular hexagon, then repeatedly doubled the number of sides as the polygon's area got closer and closer to that of the circle (and did the same with circumscribed polygons). Swiss scientist Johann Heinrich Lambert in 1761 proved that π, the ratio of a circle's area to its squared radius, is irrational, meaning it is not equal to the quotient of any two whole numbers. In 1794, French mathematician Adrien-Marie Legendre proved that π2 is irrational; this also proves that π is irrational. In 1882, German mathematician Ferdinand von Lindemann proved that π is transcendental (not the solution of any polynomial equation with rational coefficients), confirming a conjecture made by both Legendre and Euler. Triangle area Heron (or Hero) of Alexandria found what is known as Heron's formula for the area of a triangle in terms of its sides, and a proof can be found in his book, Metrica, written around 60 CE. It has been suggested that Archimedes knew the formula over two centuries earlier, and since Metrica is a collection of the mathematical knowledge available in the ancient world, it is possible that the formula predates the reference given in that work. In 499 Aryabhata, a great mathematician-astronomer from the classical age of Indian mathematics and Indian astronomy, expressed the area of a triangle as one-half the base times the height in the Aryabhatiya (section 2.6). A formula equivalent to Heron's was discovered by the Chinese independently of the Greeks. It was published in 1247 in Shushu Jiuzhang ("Mathematical Treatise in Nine Sections"), written by Qin Jiushao. Quadrilateral area In the 7th century CE, Brahmagupta developed a formula, now known as Brahmagupta's formula, for the area of a cyclic quadrilateral (a quadrilateral inscribed in a circle) in terms of its sides. In 1842, the German mathematicians Carl Anton Bretschneider and Karl Georg Christian von Staudt independently found a formula, known as Bretschneider's formula, for the area of any quadrilateral. General polygon area The development of Cartesian coordinates by René Descartes in the 17th century allowed the development of the surveyor's formula for the area of any polygon with known vertex locations by Gauss in the 19th century. Areas determined using calculus The development of integral calculus in the late 17th century provided tools that could subsequently be used for computing more complicated areas, such as the area of an ellipse and the surface areas of various curved three-dimensional objects. Area formulas Polygon formulas For a non-self-intersecting (simple) polygon, the Cartesian coordinates (i=0, 1, ..., n-1) of whose n vertices are known, the area is given by the surveyor's formula: where when i=n-1, then i+1 is expressed as modulus n and so refers to 0. Rectangles The most basic area formula is the formula for the area of a rectangle. Given a rectangle with length and width , the formula for the area is:  (rectangle). That is, the area of the rectangle is the length multiplied by the width. As a special case, as in the case of a square, the area of a square with side length is given by the formula:  (square). The formula for the area of a rectangle follows directly from the basic properties of area, and is sometimes taken as a definition or axiom. On the other hand, if geometry is developed before arithmetic, this formula can be used to define multiplication of real numbers. Dissection, parallelograms, and triangles Most other simple formulas for area follow from the method of dissection. This involves cutting a shape into pieces, whose areas must sum to the area of the original shape. For an example, any parallelogram can be subdivided into a trapezoid and a right triangle, as shown in figure to the left. If the triangle is moved to the other side of the trapezoid, then the resulting figure is a rectangle. It follows that the area of the parallelogram is the same as the area of the rectangle:  (parallelogram). However, the same parallelogram can also be cut along a diagonal into two congruent triangles, as shown in the figure to the right. It follows that the area of each triangle is half the area of the parallelogram:  (triangle). Similar arguments can be used to find area formulas for the trapezoid as well as more complicated polygons. Area of curved shapes Circles The formula for the area of a circle (more properly called the area enclosed by a circle or the area of a disk) is based on a similar method. Given a circle of radius , it is possible to partition the circle into sectors, as shown in the figure to the right. Each sector is approximately triangular in shape, and the sectors can be rearranged to form an approximate parallelogram. The height of this parallelogram is , and the width is half the circumference of the circle, or . Thus, the total area of the circle is :  (circle). Though the dissection used in this formula is only approximate, the error becomes smaller and smaller as the circle is partitioned into more and more sectors. The limit of the areas of the approximate parallelograms is exactly , which is the area of the circle. This argument is actually a simple application of the ideas of calculus. In ancient times, the method of exhaustion was used in a similar way to find the area of the circle, and this method is now recognized as a precursor to integral calculus. Using modern methods, the area of a circle can be computed using a definite integral: Ellipses The formula for the area enclosed by an ellipse is related to the formula of a circle; for an ellipse with semi-major and semi-minor axes and the formula is: Surface area Most basic formulas for surface area can be obtained by cutting surfaces and flattening them out. For example, if the side surface of a cylinder (or any prism) is cut lengthwise, the surface can be flattened out into a rectangle. Similarly, if a cut is made along the side of a cone, the side surface can be flattened out into a sector of a circle, and the resulting area computed. The formula for the surface area of a sphere is more difficult to derive: because a sphere has nonzero Gaussian curvature, it cannot be flattened out. The formula for the surface area of a sphere was first obtained by Archimedes in his work On the Sphere and Cylinder. The formula is:  (sphere), where is the radius of the sphere. As with the formula for the area of a circle, any derivation of this formula inherently uses methods similar to calculus. General formulas Areas of 2-dimensional figures A triangle: (where B is any side, and h is the distance from the line on which B lies to the other vertex of the triangle). This formula can be used if the height h is known. If the lengths of the three sides are known then Heron's formula can be used: where a, b, c are the sides of the triangle, and is half of its perimeter. If an angle and its two included sides are given, the area is where is the given angle and and are its included sides. If the triangle is graphed on a coordinate plane, a matrix can be used and is simplified to the absolute value of . This formula is also known as the shoelace formula and is an easy way to solve for the area of a coordinate triangle by substituting the 3 points (x1,y1), (x2,y2), and (x3,y3). The shoelace formula can also be used to find the areas of other polygons when their vertices are known. Another approach for a coordinate triangle is to use calculus to find the area. A simple polygon constructed on a grid of equal-distanced points (i.e., points with integer coordinates) such that all the polygon's vertices are grid points: , where i is the number of grid points inside the polygon and b is the number of boundary points. This result is known as Pick's theorem. Area in calculus The area between a positive-valued curve and the horizontal axis, measured between two values a and b (b is defined as the larger of the two values) on the horizontal axis, is given by the integral from a to b of the function that represents the curve: The area between the graphs of two functions is equal to the integral of one function, f(x), minus the integral of the other function, g(x): where is the curve with the greater y-value. An area bounded by a function expressed in polar coordinates is: The area enclosed by a parametric curve with endpoints is given by the line integrals: or the z-component of (For details, see .) This is the principle of the planimeter mechanical device. Bounded area between two quadratic functions To find the bounded area between two quadratic functions, we subtract one from the other to write the difference as where f(x) is the quadratic upper bound and g(x) is the quadratic lower bound. Define the discriminant of f(x)-g(x) as By simplifying the integral formula between the graphs of two functions (as given in the section above) and using Vieta's formula, we can obtain The above remains valid if one of the bounding functions is linear instead of quadratic. Surface area of 3-dimensional figures Cone: , where r is the radius of the circular base, and h is the height. That can also be rewritten as or where r is the radius and l is the slant height of the cone. is the base area while is the lateral surface area of the cone. cube: , where s is the length of an edge. cylinder: , where r is the radius of a base and h is the height. The 2r can also be rewritten as d, where d is the diameter. prism: 2B + Ph, where B is the area of a base, P is the perimeter of a base, and h is the height of the prism. pyramid: , where B is the area of the base, P is the perimeter of the base, and L is the length of the slant. rectangular prism: , where is the length, w is the width, and h is the height. General formula for surface area The general formula for the surface area of the graph of a continuously differentiable function where and is a region in the xy-plane with the smooth boundary: An even more general formula for the area of the graph of a parametric surface in the vector form where is a continuously differentiable vector function of is: List of formulas The above calculations show how to find the areas of many common shapes. The areas of irregular (and thus arbitrary) polygons can be calculated using the "Surveyor's formula" (shoelace formula). Relation of area to perimeter The isoperimetric inequality states that, for a closed curve of length L (so the region it encloses has perimeter L) and for area A of the region that it encloses, and equality holds if and only if the curve is a circle. Thus a circle has the largest area of any closed figure with a given perimeter. At the other extreme, a figure with given perimeter L could have an arbitrarily small area, as illustrated by a rhombus that is "tipped over" arbitrarily far so that two of its angles are arbitrarily close to 0° and the other two are arbitrarily close to 180°. For a circle, the ratio of the area to the circumference (the term for the perimeter of a circle) equals half the radius r. This can be seen from the area formula πr2 and the circumference formula 2πr. The area of a regular polygon is half its perimeter times the apothem (where the apothem is the distance from the center to the nearest point on any side). Fractals Doubling the edge lengths of a polygon multiplies its area by four, which is two (the ratio of the new to the old side length) raised to the power of two (the dimension of the space the polygon resides in). But if the one-dimensional lengths of a fractal drawn in two dimensions are all doubled, the spatial content of the fractal scales by a power of two that is not necessarily an integer. This power is called the fractal dimension of the fractal. Area bisectors There are an infinitude of lines that bisect the area of a triangle. Three of them are the medians of the triangle (which connect the sides' midpoints with the opposite vertices), and these are concurrent at the triangle's centroid; indeed, they are the only area bisectors that go through the centroid. Any line through a triangle that splits both the triangle's area and its perimeter in half goes through the triangle's incenter (the center of its incircle). There are either one, two, or three of these for any given triangle. Any line through the midpoint of a parallelogram bisects the area. All area bisectors of a circle or other ellipse go through the center, and any chords through the center bisect the area. In the case of a circle they are the diameters of the circle. Optimization Given a wire contour, the surface of least area spanning ("filling") it is a minimal surface. Familiar examples include soap bubbles. The question of the filling area of the Riemannian circle remains open. The circle has the largest area of any two-dimensional object having the same perimeter. A cyclic polygon (one inscribed in a circle) has the largest area of any polygon with a given number of sides of the same lengths. A version of the isoperimetric inequality for triangles states that the triangle of greatest area among all those with a given perimeter is equilateral. The triangle of largest area of all those inscribed in a given circle is equilateral; and the triangle of smallest area of all those circumscribed around a given circle is equilateral. The ratio of the area of the incircle to the area of an equilateral triangle, , is larger than that of any non-equilateral triangle. The ratio of the area to the square of the perimeter of an equilateral triangle, is larger than that for any other triangle. See also Brahmagupta quadrilateral, a cyclic quadrilateral with integer sides, integer diagonals, and integer area. Equiareal map Heronian triangle, a triangle with integer sides and integer area. List of triangle inequalities One-seventh area triangle, an inner triangle with one-seventh the area of the reference triangle. Routh's theorem, a generalization of the one-seventh area triangle. Orders of magnitude—A list of areas by size. Derivation of the formula of a pentagon Planimeter, an instrument for measuring small areas, e.g. on maps. Area of a convex quadrilateral Robbins pentagon, a cyclic pentagon whose side lengths and area are all rational numbers. References External links

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1212

https://en.wikipedia.org/wiki/Artist

Artist

An artist is a person engaged in an activity related to creating art, practicing the arts, or demonstrating an art. The common usage in both everyday speech and academic discourse refers to a practitioner in the visual arts only. However, the term is also often used in the entertainment business, especially in a business context, for musicians and other performers (although less often for actors). "Artiste" (French for artist) is a variant used in English in this context, but this use has become rare. Use of the term "artist" to describe writers is valid, but less common, and mostly restricted to contexts like used in criticism. Dictionary definitions The Oxford English Dictionary defines the older broad meanings of the term "artist": A learned person or Master of Arts. One who pursues a practical science, traditionally medicine, astrology, alchemy, chemistry. A follower of a pursuit in which skill comes by study or practice. A follower of a manual art, such as a mechanic. One who makes their craft a fine art. One who cultivates one of the fine arts – traditionally the arts presided over by the muses. History of the term The Greek word "techně", often translated as "art," implies mastery of any sort of craft. The adjectival Latin form of the word, "technicus", became the source of the English words technique, technology, technical. In Greek culture each of the nine Muses oversaw a different field of human creation: Calliope (the 'beautiful of speech'): chief of the muses and muse of epic or heroic poetry Clio (the 'glorious one'): muse of history Erato (the 'amorous one'): muse of love or erotic poetry, lyrics, and marriage songs Euterpe (the 'well-pleasing'): muse of music and lyric poetry Melpomene (the 'chanting one'): muse of tragedy Polyhymnia or Polymnia (the '[singer] of many hymns'): muse of sacred song, oratory, lyric, singing, and rhetoric Terpsichore (the '[one who] delights in dance'): muse of choral song and dance Thalia (the 'blossoming one'): muse of comedy and bucolic poetry Urania (the 'celestial one'): muse of astronomy No muse was identified with the visual arts of painting and sculpture. In ancient Greece sculptors and painters were held in low regard, somewhere between freemen and slaves, their work regarded as mere manual labour. The word art derives from the Latin "ars" (stem art-), which, although literally defined means "skill method" or "technique", also conveys a connotation of beauty. During the Middle Ages the word artist already existed in some countries such as Italy, but the meaning was something resembling craftsman, while the word artesan was still unknown. An artist was someone able to do a work better than others, so the skilled excellency was underlined, rather than the activity field. In this period some "artisanal" products (such as textiles) were much more precious and expensive than paintings or sculptures. The first division into major and minor arts dates back at least to the works of Leon Battista Alberti (1404–1472): De re aedificatoria, De statua, De pictura, which focused on the importance of the intellectual skills of the artist rather than the manual skills (even if in other forms of art there was a project behind). With the Academies in Europe (second half of 16th century) the gap between fine and applied arts was definitely set. Many contemporary definitions of "artist" and "art" are highly contingent on culture, resisting aesthetic prescription, in much the same way that the features constituting beauty and the beautiful cannot be standardized easily without moving into kitsch. Training and employment The US Bureau of Labor Statistics classifies many visual artists as either craft artists or fine artists. A craft artist makes handmade functional works of art, such as pottery or clothing. A fine artist makes paintings, illustrations (such as book illustrations or medical illustrations), sculptures, or similar artistic works primarily for their aesthetic value. The main source of skill for both craft artists and fine artists is long-term repetition and practice. Many fine artists have studied their art form at university and some have a master's degree in fine arts. Artists may also study on their own or receive on-the-job training from an experienced artist. The number of available jobs as an artist is increasing more slowly than other fields. About half of US artists are self-employed. Others work in a variety of industries. For example, a pottery manufacturer will employ craft artists, and book publishers will hire illustrators. In the US, fine artists have a median income of approximately US$50,000 per year, and craft artists have a median income of approximately US$33,000 per year. This compares to US$61,000 for all art-related fields, including related jobs such as graphic designers, multimedia artists, animators, and fashion designers. Many artists work part-time as artists and hold a second job. See also Art Art history Arts by region Artist in Residence Fine art Humanities List of painters by name List of painters List of composers List of sculptors List of sketches of notable people by Marguerite Martyn Mathematics and art Social science Notes References P.Galloni, Il sacro artefice. Mitologie degli artigiani medievali, Laterza, Bari, 1998 C. T. Onions (1991). The Shorter Oxford English Dictionary. Clarendon Press Oxford. External links Aesthetics Art occupations Arts-related lists Humanities occupations Artisans

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1264

https://en.wikipedia.org/wiki/Anisotropy

Anisotropy

Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties (absorbance, refractive index, conductivity, tensile strength, etc.). An example of anisotropy is light coming through a polarizer. Another is wood, which is easier to split along its grain than across it. Fields of interest Computer graphics In the field of computer graphics, an anisotropic surface changes in appearance as it rotates about its geometric normal, as is the case with velvet. Anisotropic filtering (AF) is a method of enhancing the image quality of textures on surfaces that are far away and steeply angled with respect to the point of view. Older techniques, such as bilinear and trilinear filtering, do not take into account the angle a surface is viewed from, which can result in aliasing or blurring of textures. By reducing detail in one direction more than another, these effects can be reduced. Chemistry A chemical anisotropic filter, as used to filter particles, is a filter with increasingly smaller interstitial spaces in the direction of filtration so that the proximal regions filter out larger particles and distal regions increasingly remove smaller particles, resulting in greater flow-through and more efficient filtration. In NMR spectroscopy, the orientation of nuclei with respect to the applied magnetic field determines their chemical shift. In this context, anisotropic systems refer to the electron distribution of molecules with abnormally high electron density, like the pi system of benzene. This abnormal electron density affects the applied magnetic field and causes the observed chemical shift to change. In fluorescence spectroscopy, the fluorescence anisotropy, calculated from the polarization properties of fluorescence from samples excited with plane-polarized light, is used, e.g., to determine the shape of a macromolecule. Anisotropy measurements reveal the average angular displacement of the fluorophore that occurs between absorption and subsequent emission of a photon. Real-world imagery Images of a gravity-bound or man-made environment are particularly anisotropic in the orientation domain, with more image structure located at orientations parallel with or orthogonal to the direction of gravity (vertical and horizontal). Physics Physicists from University of California, Berkeley reported about their detection of the cosine anisotropy in cosmic microwave background radiation in 1977. Their experiment demonstrated the Doppler shift caused by the movement of the earth with respect to the early Universe matter, the source of the radiation. Cosmic anisotropy has also been seen in the alignment of galaxies' rotation axes and polarisation angles of quasars. Physicists use the term anisotropy to describe direction-dependent properties of materials. Magnetic anisotropy, for example, may occur in a plasma, so that its magnetic field is oriented in a preferred direction. Plasmas may also show "filamentation" (such as that seen in lightning or a plasma globe) that is directional. An anisotropic liquid has the fluidity of a normal liquid, but has an average structural order relative to each other along the molecular axis, unlike water or chloroform, which contain no structural ordering of the molecules. Liquid crystals are examples of anisotropic liquids. Some materials conduct heat in a way that is isotropic, that is independent of spatial orientation around the heat source. Heat conduction is more commonly anisotropic, which implies that detailed geometric modeling of typically diverse materials being thermally managed is required. The materials used to transfer and reject heat from the heat source in electronics are often anisotropic. Many crystals are anisotropic to light ("optical anisotropy"), and exhibit properties such as birefringence. Crystal optics describes light propagation in these media. An "axis of anisotropy" is defined as the axis along which isotropy is broken (or an axis of symmetry, such as normal to crystalline layers). Some materials can have multiple such optical axes. Geophysics and geology Seismic anisotropy is the variation of seismic wavespeed with direction. Seismic anisotropy is an indicator of long range order in a material, where features smaller than the seismic wavelength (e.g., crystals, cracks, pores, layers or inclusions) have a dominant alignment. This alignment leads to a directional variation of elasticity wavespeed. Measuring the effects of anisotropy in seismic data can provide important information about processes and mineralogy in the Earth; significant seismic anisotropy has been detected in the Earth's crust, mantle and inner core. Geological formations with distinct layers of sedimentary material can exhibit electrical anisotropy; electrical conductivity in one direction (e.g. parallel to a layer), is different from that in another (e.g. perpendicular to a layer). This property is used in the gas and oil exploration industry to identify hydrocarbon-bearing sands in sequences of sand and shale. Sand-bearing hydrocarbon assets have high resistivity (low conductivity), whereas shales have lower resistivity. Formation evaluation instruments measure this conductivity/resistivity and the results are used to help find oil and gas in wells. The mechanical anisotropy measured for some of the sedimentary rocks like coal and shale can change with corresponding changes in their surface properties like sorption when gases are produced from the coal and shale reservoirs. The hydraulic conductivity of aquifers is often anisotropic for the same reason. When calculating groundwater flow to drains or to wells, the difference between horizontal and vertical permeability must be taken into account, otherwise the results may be subject to error. Most common rock-forming minerals are anisotropic, including quartz and feldspar. Anisotropy in minerals is most reliably seen in their optical properties. An example of an isotropic mineral is garnet. Medical acoustics Anisotropy is also a well-known property in medical ultrasound imaging describing a different resulting echogenicity of soft tissues, such as tendons, when the angle of the transducer is changed. Tendon fibers appear hyperechoic (bright) when the transducer is perpendicular to the tendon, but can appear hypoechoic (darker) when the transducer is angled obliquely. This can be a source of interpretation error for inexperienced practitioners. Materials science and engineering Anisotropy, in materials science, is a material's directional dependence of a physical property. This is a critical consideration for materials selection in engineering applications. A material with physical properties that are symmetric about an axis that is normal to a plane of isotropy is called a transversely isotropic material. Tensor descriptions of material properties can be used to determine the directional dependence of that property. For a monocrystalline material, anisotropy is associated with the crystal symmetry in the sense that more symmetric crystal types have fewer independent coefficients in the tensor description of a given property. When a material is polycrystalline, the directional dependence on properties is often related to the processing techniques it has undergone. A material with randomly oriented grains will be isotropic, whereas materials with texture will be often be anisotropic. Textured materials are often the result of processing techniques like hot rolling, wire-drawing, and heat treatment. Mechanical properties of materials such as Young's modulus, ductility, yield strength, and high temperature creep rate, are often dependent on the direction of measurement. Fourth rank tensor properties, like the elastic constants, are anisotropic, even for materials with cubic symmetry. The Young's modulus relates stress and strain when an isotropic material is elastically deformed; to describe elasticity in an anisotropic material, stiffness (or compliance) tensors are used instead. In metals, anisotropic elasticity behavior is present in all single crystals with three independent coefficients for cubic crystals, for example. For face centered cubic materials such as Nickel and Copper, the stiffness is highest along the <111> direction, normal to the close packed planes, and smallest parallel to <100>. Tungsten is so nearly isotropic at room temperature that it can be considered to have only two stiffness coefficients; Aluminum is another metal that is nearly isotropic. For an isotropic material, , where is the shear modulus, is the Young's modulus, and is the material's Poisson's ratio. Therefore, for cubic materials, we can think of anisotropy, , as the ratio between the empirically determined shear modulus for the cubic material and its (isotropic) equivalent: The latter expression is known as the Zener ratio, , where refers to Elastic constants in Voigt (vector-matrix) notation. For an isotropic material, the ratio is one. Fiber-reinforced or layered composite materials exhibit anisotropic mechanical properties, due to orientation of the reinforcement material. In many fiber-reinforced composites like carbon fiber or glass fiber based composites, the weave of the material (e.g. unidirectional or plain weave) can determine the extent of the anisotropy of the bulk material. The tunability of orientation of the fibers, allows for application-based designs of composite materials, depending on the direction of stresses applied onto the material. Amorphous materials such as glass and polymers are typically isotropic. Due to the highly randomized orientation of macromolecules in polymeric materials, polymers are in general described as isotropic. However, polymers can be engineered to have directionally dependent properties through processing techniques or introduction of anisotropy-inducing elements. Researchers have built composite materials with aligned fibers and voids to generate anisotropic hydrogels, in order to mimic hierarchically ordered biological soft matter. 3D printing, especially Fused Deposition Modeling, can introduce anisotropy into printed parts. This is due to the fact that FDM is designed to extrude and print layers of thermoplastic materials. This creates materials that are strong when tensile stress is applied in parallel to the layers and weak when the material is perpendicular to the layers. Microfabrication Anisotropic etching techniques (such as deep reactive ion etching) are used in microfabrication processes to create well defined microscopic features with a high aspect ratio. These features are commonly used in MEMS and microfluidic devices, where the anisotropy of the features is needed to impart desired optical, electrical, or physical properties to the device. Anisotropic etching can also refer to certain chemical etchants used to etch a certain material preferentially over certain crystallographic planes (e.g., KOH etching of silicon [100] produces pyramid-like structures) Neuroscience Diffusion tensor imaging is an MRI technique that involves measuring the fractional anisotropy of the random motion (Brownian motion) of water molecules in the brain. Water molecules located in fiber tracts are more likely to be anisotropic, since they are restricted in their movement (they move more in the dimension parallel to the fiber tract rather than in the two dimensions orthogonal to it), whereas water molecules dispersed in the rest of the brain have less restricted movement and therefore display more isotropy. This difference in fractional anisotropy is exploited to create a map of the fiber tracts in the brains of the individual. Atmospheric radiative transfer Radiance fields (see BRDF) from a reflective surface are often not isotropic in nature. This makes calculations of the total energy being reflected from any scene a difficult quantity to calculate. In remote sensing applications, anisotropy functions can be derived for specific scenes, immensely simplifying the calculation of the net reflectance or (thereby) the net irradiance of a scene. For example, let the BRDF be where 'i' denotes incident direction and 'v' denotes viewing direction (as if from a satellite or other instrument). And let P be the Planar Albedo, which represents the total reflectance from the scene. It is of interest because, with knowledge of the anisotropy function as defined, a measurement of the BRDF from a single viewing direction (say, ) yields a measure of the total scene reflectance (Planar Albedo) for that specific incident geometry (say, ). See also Circular symmetry References External links "Gauge, and knitted fabric generally, is an anisotropic phenomenon" "Overview of Anisotropy" DoITPoMS Teaching and Learning Package: "Introduction to Anisotropy" Orientation (geometry) Asymmetry

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1267

https://en.wikipedia.org/wiki/Alpha%20decay

Alpha decay

Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. It has a charge of and a mass of . For example, uranium-238 decays to form thorium-234. Alpha particles have a charge , but as a nuclear equation describes a nuclear reaction without considering the electrons – a convention that does not imply that the nuclei necessarily occur in neutral atoms – the charge is not usually shown. Alpha decay typically occurs in the heaviest nuclides. Theoretically, it can occur only in nuclei somewhat heavier than nickel (element 28), where the overall binding energy per nucleon is no longer a maximum and the nuclides are therefore unstable toward spontaneous fission-type processes. In practice, this mode of decay has only been observed in nuclides considerably heavier than nickel, with the lightest known alpha emitters being the lightest isotopes (mass numbers 104–109) of tellurium (element 52). Exceptionally, however, beryllium-8 decays to two alpha particles. Alpha decay is by far the most common form of cluster decay, where the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind. It is the most common form because of the combined extremely high nuclear binding energy and a relatively small mass of the alpha particle. Like other cluster decays, alpha decay is fundamentally a quantum tunneling process. Unlike beta decay, it is governed by the interplay between both the strong nuclear force and the electromagnetic force. Alpha particles have a typical kinetic energy of 5 MeV (or ≈ 0.13% of their total energy, 110 TJ/kg) and have a speed of about 15,000,000 m/s, or 5% of the speed of light. There is surprisingly small variation around this energy, due to the heavy dependence of the half-life of this process on the energy produced. Because of their relatively large mass, the electric charge of and relatively low velocity, alpha particles are very likely to interact with other atoms and lose their energy, and their forward motion can be stopped by a few centimeters of air. Approximately 99% of the helium produced on Earth is the result of the alpha decay of underground deposits of minerals containing uranium or thorium. The helium is brought to the surface as a by-product of natural gas production. History Alpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899, and by 1907 they were identified as He2+ ions. By 1928, George Gamow had solved the theory of alpha decay via tunneling. The alpha particle is trapped inside the nucleus by an attractive nuclear potential well and a repulsive electromagnetic potential barrier. Classically, it is forbidden to escape, but according to the (then) newly discovered principles of quantum mechanics, it has a tiny (but non-zero) probability of "tunneling" through the barrier and appearing on the other side to escape the nucleus. Gamow solved a model potential for the nucleus and derived, from first principles, a relationship between the half-life of the decay, and the energy of the emission, which had been previously discovered empirically, and was known as the Geiger–Nuttall law. Mechanism The nuclear force holding an atomic nucleus together is very strong, in general much stronger than the repulsive electromagnetic forces between the protons. However, the nuclear force is also short-range, dropping quickly in strength beyond about 1 femtometer, while the electromagnetic force has an unlimited range. The strength of the attractive nuclear force keeping a nucleus together is thus proportional to the number of nucleons, but the total disruptive electromagnetic force trying to break the nucleus apart is roughly proportional to the square of its atomic number. A nucleus with 210 or more nucleons is so large that the strong nuclear force holding it together can just barely counterbalance the electromagnetic repulsion between the protons it contains. Alpha decay occurs in such nuclei as a means of increasing stability by reducing size. One curiosity is why alpha particles, helium nuclei, should be preferentially emitted as opposed to other particles like a single proton or neutron or other atomic nuclei. Part of the reason is the high binding energy of the alpha particle, which means that its mass is less than the sum of the masses of two protons and two neutrons. This increases the disintegration energy. Computing the total disintegration energy given by the equation where is the initial mass of the nucleus, is the mass of the nucleus after particle emission, and is the mass of the emitted particle, one finds that in certain cases it is positive and so alpha particle emission is possible, whereas other decay modes would require energy to be added. For example, performing the calculation for uranium-232 shows that alpha particle emission gives 5.4 MeV of energy, while a single proton emission would require 6.1 MeV. Most of the disintegration energy becomes the kinetic energy of the alpha particle itself, although to maintain conservation of momentum part of the energy goes to the recoil of the nucleus itself (see Atomic recoil). However, since the mass numbers of most alpha-emitting radioisotopes exceed 210, far greater than the mass number of the alpha particle (4) the fraction of the energy going to the recoil of the nucleus is generally quite small, less than 2%, however the recoil energy (on the scale of keV) is still much larger than the strength of chemical bonds (on the scale of eV), so the daughter nuclide will break away from the chemical environment the parent was in. The energies and ratios of the alpha particles can be used to identify the radioactive parent via alpha spectrometry. These disintegration energies, however, are substantially smaller than the repulsive potential barrier created by the electromagnetic force, which prevents the alpha particle from escaping. The energy needed to bring an alpha particle from infinity to a point near the nucleus just outside the range of the nuclear force's influence is generally in the range of about 25 MeV. An alpha particle can be thought of as being inside a potential barrier whose walls are 25 MeV above the potential at infinity. However, decay alpha particles only have energies of around 4 to 9 MeV above the potential at infinity, far less than the energy needed to escape. Quantum mechanics, however, allows the alpha particle to escape via quantum tunneling. The quantum tunneling theory of alpha decay, independently developed by George Gamow and Ronald Wilfred Gurney and Edward Condon in 1928, was hailed as a very striking confirmation of quantum theory. Essentially, the alpha particle escapes from the nucleus not by acquiring enough energy to pass over the wall confining it, but by tunneling through the wall. Gurney and Condon made the following observation in their paper on it: It has hitherto been necessary to postulate some special arbitrary 'instability' of the nucleus, but in the following note, it is pointed out that disintegration is a natural consequence of the laws of quantum mechanics without any special hypothesis... Much has been written of the explosive violence with which the α-particle is hurled from its place in the nucleus. But from the process pictured above, one would rather say that the α-particle almost slips away unnoticed. The theory supposes that the alpha particle can be considered an independent particle within a nucleus, that is in constant motion but held within the nucleus by strong interaction. At each collision with the repulsive potential barrier of the electromagnetic force, there is a small non-zero probability that it will tunnel its way out. An alpha particle with a speed of 1.5×107 m/s within a nuclear diameter of approximately 10−14 m will collide with the barrier more than 1021 times per second. However, if the probability of escape at each collision is very small, the half-life of the radioisotope will be very long, since it is the time required for the total probability of escape to reach 50%. As an extreme example, the half-life of the isotope bismuth-209 is . The isotopes in beta-decay stable isobars that are also stable with regards to double beta decay with mass number A = 5, A = 8, 143 ≤ A ≤ 155, 160 ≤ A ≤ 162, and A ≥ 165 are theorized to undergo alpha decay. All other mass numbers (isobars) have exactly one theoretically stable nuclide). Those with mass 5 decay to helium-4 and a proton or a neutron, and those with mass 8 decay to two helium-4 nuclei; their half-lives (helium-5, lithium-5, and beryllium-8) are very short, unlike the half-lives for all other such nuclides with A ≤ 209, which are very long. (Such nuclides with A ≤ 209 are primordial nuclides except 146Sm.) Working out the details of the theory leads to an equation relating the half-life of a radioisotope to the decay energy of its alpha particles, a theoretical derivation of the empirical Geiger–Nuttall law. Uses Americium-241, an alpha emitter, is used in smoke detectors. The alpha particles ionize air in an open ion chamber and a small current flows through the ionized air. Smoke particles from the fire that enter the chamber reduce the current, triggering the smoke detector's alarm. Radium-223 is also an alpha emitter. It is used in the treatment of skeletal metastases (cancers in the bones). Alpha decay can provide a safe power source for radioisotope thermoelectric generators used for space probes and were used for artificial heart pacemakers. Alpha decay is much more easily shielded against than other forms of radioactive decay. Static eliminators typically use polonium-210, an alpha emitter, to ionize the air, allowing the 'static cling' to dissipate more rapidly. Toxicity Highly charged and heavy, alpha particles lose their several MeV of energy within a small volume of material, along with a very short mean free path. This increases the chance of double-strand breaks to the DNA in cases of internal contamination, when ingested, inhaled, injected or introduced through the skin. Otherwise, touching an alpha source is typically not harmful, as alpha particles are effectively shielded by a few centimeters of air, a piece of paper, or the thin layer of dead skin cells that make up the epidermis; however, many alpha sources are also accompanied by beta-emitting radio daughters, and both are often accompanied by gamma photon emission. Relative biological effectiveness (RBE) quantifies the ability of radiation to cause certain biological effects, notably either cancer or cell-death, for equivalent radiation exposure. Alpha radiation has a high linear energy transfer (LET) coefficient, which is about one ionization of a molecule/atom for every angstrom of travel by the alpha particle. The RBE has been set at the value of 20 for alpha radiation by various government regulations. The RBE is set at 10 for neutron irradiation, and at 1 for beta radiation and ionizing photons. However, the recoil of the parent nucleus (alpha recoil) gives it a significant amount of energy, which also causes ionization damage (see ionizing radiation). This energy is roughly the weight of the alpha (4 u) divided by the weight of the parent (typically about 200 u) times the total energy of the alpha. By some estimates, this might account for most of the internal radiation damage, as the recoil nucleus is part of an atom that is much larger than an alpha particle, and causes a very dense trail of ionization; the atom is typically a heavy metal, which preferentially collect on the chromosomes. In some studies, this has resulted in an RBE approaching 1,000 instead of the value used in governmental regulations. The largest natural contributor to public radiation dose is radon, a naturally occurring, radioactive gas found in soil and rock. If the gas is inhaled, some of the radon particles may attach to the inner lining of the lung. These particles continue to decay, emitting alpha particles, which can damage cells in the lung tissue. The death of Marie Curie at age 66 from aplastic anemia was probably caused by prolonged exposure to high doses of ionizing radiation, but it is not clear if this was due to alpha radiation or X-rays. Curie worked extensively with radium, which decays into radon, along with other radioactive materials that emit beta and gamma rays. However, Curie also worked with unshielded X-ray tubes during World War I, and analysis of her skeleton during a reburial showed a relatively low level of radioisotope burden. The Russian dissident Alexander Litvinenko's 2006 murder by radiation poisoning is thought to have been carried out with polonium-210, an alpha emitter. References Alpha emitters by increasing energy (Appendix 1) Notes External links The LIVEChart of Nuclides - IAEA with filter on alpha decay Alpha decay with 3 animated examples showing the recoil of daughter Helium Nuclear physics Radioactivity

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1271

https://en.wikipedia.org/wiki/Analytical%20Engine

Analytical Engine

The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage. It was first described in 1837 as the successor to Babbage's difference engine, which was a design for a simpler mechanical calculator. The Analytical Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete. In other words, the logical structure of the Analytical Engine was essentially the same as that which has dominated computer design in the electronic era. The Analytical Engine is one of the most successful achievements of Charles Babbage. Babbage was never able to complete construction of any of his machines due to conflicts with his chief engineer and inadequate funding. It was not until 1941 that Konrad Zuse built the first general-purpose computer, Z3, more than a century after Babbage had proposed the pioneering Analytical Engine in 1837. Design Babbage's first attempt at a mechanical computing device, the Difference Engine, was a special-purpose machine designed to tabulate logarithms and trigonometric functions by evaluating finite differences to create approximating polynomials. Construction of this machine was never completed; Babbage had conflicts with his chief engineer, Joseph Clement, and ultimately the British government withdrew its funding for the project. During this project, Babbage realised that a much more general design, the Analytical Engine, was possible. The work on the design of the Analytical Engine started in c. 1833. The input, consisting of programs ("formulae") and data, was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. For output, the machine would have a printer, a curve plotter, and a bell. The machine would also be able to punch numbers onto cards to be read in later. It employed ordinary base-10 fixed-point arithmetic. There was to be a store (that is, a memory) capable of holding 1,000 numbers of 40 decimal digits each (ca. 16.6 kB). An arithmetic unit (the "mill") would be able to perform all four arithmetic operations, plus comparisons and optionally square roots. Initially (1838) it was conceived as a difference engine curved back upon itself, in a generally circular layout, with the long store exiting off to one side. Later drawings (1858) depict a regularised grid layout. Like the central processing unit (CPU) in a modern computer, the mill would rely upon its own internal procedures, to be stored in the form of pegs inserted into rotating drums called "barrels", to carry out some of the more complex instructions the user's program might specify. The programming language to be employed by users was akin to modern day assembly languages. Loops and conditional branching were possible, and so the language as conceived would have been Turing-complete as later defined by Alan Turing. Three different types of punch cards were used: one for arithmetical operations, one for numerical constants, and one for load and store operations, transferring numbers from the store to the arithmetical unit or back. There were three separate readers for the three types of cards. Babbage developed some two dozen programs for the Analytical Engine between 1837 and 1840, and one program later. These programs treat polynomials, iterative formulas, Gaussian elimination, and Bernoulli numbers. In 1842, the Italian mathematician Luigi Federico Menabrea published a description of the engine in French, based on lectures Babbage gave when he visited Turin in 1840. In 1843, the description was translated into English and extensively annotated by Ada Lovelace, who had become interested in the engine eight years earlier. In recognition of her additions to Menabrea's paper, which included a way to calculate Bernoulli numbers using the machine (widely considered to be the first complete computer program), she has been described as the first computer programmer. Construction Late in his life, Babbage sought ways to build a simplified version of the machine, and assembled a small part of it before his death in 1871. In 1878, a committee of the British Association for the Advancement of Science described the Analytical Engine as "a marvel of mechanical ingenuity", but recommended against constructing it. The committee acknowledged the usefulness and value of the machine, but could not estimate the cost of building it, and were unsure whether the machine would function correctly after being built. Intermittently from 1880 to 1910, Babbage's son Henry Prevost Babbage was constructing a part of the mill and the printing apparatus. In 1910, it was able to calculate a (faulty) list of multiples of pi. This constituted only a small part of the whole engine; it was not programmable and had no storage. (Popular images of this section have sometimes been mislabelled, implying that it was the entire mill or even the entire engine.) Henry Babbage's "Analytical Engine Mill" is on display at the Science Museum in London. Henry also proposed building a demonstration version of the full engine, with a smaller storage capacity: "perhaps for a first machine ten (columns) would do, with fifteen wheels in each". Such a version could manipulate 20 numbers of 25 digits each, and what it could be told to do with those numbers could still be impressive. "It is only a question of cards and time", wrote Henry Babbage in 1888, "... and there is no reason why (twenty thousand) cards should not be used if necessary, in an Analytical Engine for the purposes of the mathematician". In 1991, the London Science Museum built a complete and working specimen of Babbage's Difference Engine No. 2, a design that incorporated refinements Babbage discovered during the development of the Analytical Engine. This machine was built using materials and engineering tolerances that would have been available to Babbage, quelling the suggestion that Babbage's designs could not have been produced using the manufacturing technology of his time. In October 2010, John Graham-Cumming started a "Plan 28" campaign to raise funds by "public subscription" to enable serious historical and academic study of Babbage's plans, with a view to then build and test a fully working virtual design which will then in turn enable construction of the physical Analytical Engine. As of May 2016, actual construction had not been attempted, since no consistent understanding could yet be obtained from Babbage's original design drawings. In particular it was unclear whether it could handle the indexed variables which were required for Lovelace's Bernoulli program. By 2017, the "Plan 28" effort reported that a searchable database of all catalogued material was available, and an initial review of Babbage's voluminous Scribbling Books had been completed. Many of Babbage's original drawings have been digitized and are publicly available online. Instruction set Babbage is not known to have written down an explicit set of instructions for the engine in the manner of a modern processor manual. Instead he showed his programs as lists of states during their execution, showing what operator was run at each step with little indication of how the control flow would be guided. Allan G. Bromley has assumed that the card deck could be read in forwards and backwards directions as a function of conditional branching after testing for conditions, which would make the engine Turing-complete: ...the cards could be ordered to move forward and reverse (and hence to loop)... The introduction for the first time, in 1845, of user operations for a variety of service functions including, most importantly, an effective system for user control of looping in user programs. There is no indication how the direction of turning of the operation and variable cards is specified. In the absence of other evidence I have had to adopt the minimal default assumption that both the operation and variable cards can only be turned backward as is necessary to implement the loops used in Babbage's sample programs. There would be no mechanical or microprogramming difficulty in placing the direction of motion under the control of the user. In their emulator of the engine, Fourmilab say: The Engine's Card Reader is not constrained to simply process the cards in a chain one after another from start to finish. It can, in addition, directed by the very cards it reads and advised by whether the Mill's run-up lever is activated, either advance the card chain forward, skipping the intervening cards, or backward, causing previously-read cards to be processed once again. This emulator does provide a written symbolic instruction set, though this has been constructed by its authors rather than based on Babbage's original works. For example, a factorial program would be written as: N0 6 N1 1 N2 1 × L1 L0 S1 – L0 L2 S0 L2 L0 CB?11 where the CB is the conditional branch instruction or "combination card" used to make the control flow jump, in this case backward by 11 cards. Influence Predicted influence Babbage understood that the existence of an automatic computer would kindle interest in the field now known as algorithmic efficiency, writing in his Passages from the Life of a Philosopher, "As soon as an Analytical Engine exists, it will necessarily guide the future course of the science. Whenever any result is sought by its aid, the question will then arise—By what course of calculation can these results be arrived at by the machine in the shortest time?" Computer science From 1872 Henry continued diligently with his father's work and then intermittently in retirement in 1875. Percy Ludgate wrote about the engine in 1914 and published his own design for an Analytical Engine in 1908. It was drawn up in detail, but never built, and the drawings have never been found. Ludgate's engine would be much smaller (about ) than Babbage's, and hypothetically would be capable of multiplying two 20-decimal-digit numbers in about six seconds. In his Essays on Automatics (1913) Leonardo Torres y Quevedo designed a Babbage type of calculating machine that used electromechanical parts which included floating point number representations and built an early prototype in 1920. Vannevar Bush's paper Instrumental Analysis (1936) included several references to Babbage's work. In the same year he started the Rapid Arithmetical Machine project to investigate the problems of constructing an electronic digital computer. Despite this groundwork, Babbage's work fell into historical obscurity, and the Analytical Engine was unknown to builders of electromechanical and electronic computing machines in the 1930s and 1940s when they began their work, resulting in the need to re-invent many of the architectural innovations Babbage had proposed. Howard Aiken, who built the quickly-obsoleted electromechanical calculator, the Harvard Mark I, between 1937 and 1945, praised Babbage's work likely as a way of enhancing his own stature, but knew nothing of the Analytical Engine's architecture during the construction of the Mark I, and considered his visit to the constructed portion of the Analytical Engine "the greatest disappointment of my life". The Mark I showed no influence from the Analytical Engine and lacked the Analytical Engine's most prescient architectural feature, conditional branching. J. Presper Eckert and John W. Mauchly similarly were not aware of the details of Babbage's Analytical Engine work prior to the completion of their design for the first electronic general-purpose computer, the ENIAC. Comparison to other early computers If the Analytical Engine had been built, it would have been digital, programmable and Turing-complete. It would, however, have been very slow. Luigi Federico Menabrea reported in Sketch of the Analytical Engine: "Mr. Babbage believes he can, by his engine, form the product of two numbers, each containing twenty figures, in three minutes". By comparison the Harvard Mark I could perform the same task in just six seconds. A modern PC can do the same thing in well under a billionth of a second. In popular culture The cyberpunk novelists William Gibson and Bruce Sterling co-authored a steampunk novel of alternative history titled The Difference Engine in which Babbage's difference and Analytical Engines became available to Victorian society. The novel explores the consequences and implications of the early introduction of computational technology. Moriarty by Modem, a short story by Jack Nimersheim, describes an alternative history where Babbage's Analytical Engine was indeed completed and had been deemed highly classified by the British government. The characters of Sherlock Holmes and Moriarty had in reality been a set of prototype programs written for the Analytical Engine. This short story follows Holmes as his program is implemented on modern computers and he is forced to compete against his nemesis yet again in the modern counterparts of Babbage's Analytical Engine. A similar setting is used by Sydney Padua in the webcomic The Thrilling Adventures of Lovelace and Babbage. It features an alternative history where Ada Lovelace and Babbage have built the Analytical Engine and use it to fight crime at Queen Victoria's request. The comic is based on thorough research on the biographies of and correspondence between Babbage and Lovelace, which is then twisted for humorous effect. The Orion's Arm online project features the Machina Babbagenseii, fully sentient Babbage-inspired mechanical computers. Each is the size of a large asteroid, only capable surviving in microgravity conditions, and processes data at 0.5% the speed of a human brain. References Bibliography External links The Babbage Papers, Science Museum archive The Analytical Engine at Fourmilab, includes historical documents and online simulations Image of a later Plan of Analytical Engine with grid layout (1858) First working Babbage "barrel" actually assembled, circa 2005 Special issue, IEEE Annals of the History of Computing, Volume 22, Number 4, October–December 2000 Babbage, Science Museum, London Plan 28: Building Charles Babbage's Analytical Engine Charles Babbage Computer-related introductions in 1837 English inventions Mechanical calculators Mechanical computers One-of-a-kind computers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1293

https://en.wikipedia.org/wiki/Alfred%20Lawson

Alfred Lawson

Alfred William Lawson (March 24, 1869 – November 29, 1954) was a professional baseball player, aviator and utopian philosopher. He was a baseball player, manager, and league promoter from 1887 through 1916 and went on to play a pioneering role in the U.S. aircraft industry. He published two early aviation trade journals. He is frequently cited as the inventor of the airliner and was awarded several of the first air mail contracts, which he ultimately could not fulfill. He founded the Lawson Aircraft Company in Green Bay, Wisconsin, to build military training aircraft and later the Lawson Airplane Company in South Milwaukee, Wisconsin, to build airliners. The crash of his ambitious Lawson L-4 "Midnight Liner" during its trial flight takeoff on May 8, 1921, ended his best chance for commercial aviation success. In 1904, he wrote a utopian novel, Born Again, in which he developed the philosophy which later became Lawsonomy. Baseball career (1888–1907) He made one start for the Boston Beaneaters and two for the Pittsburgh Alleghenys during the 1890 season. His minor league playing career lasted through 1895. He later managed in the minors from 1905 to 1907. Union Professional League In 1908, he started a new professional baseball league known as the Union Professional League. The league took the field in April but folded one month later owing to financial difficulties. Aviation career (1908–1928) An early advocate or rather evangelist of aviation, in October 1908 Lawson started the magazine Fly to stimulate public interest and educate readers in the fundamentals of the new science of aviation. It sold for 10 cents a copy from newsstands across the country. In 1910, moving to New York City, he renamed the magazine Aircraft and published it until 1914. The magazine chronicled the technical developments of the early aviation pioneers. Lawson was the first advocate for commercial air travel, coining the term "airline." He also advocated for a strong American flying force, lobbying Congress in 1913 to expand its appropriations for Army aircraft. In early 1913, he learned to fly the Sloan-Deperdussin and the Moisant-Bleriot monoplanes, becoming an accomplished pilot. Later that year he bought a Thomas flying boat and became the first air commuter regularly flying from his country house in Seidler's Beach, New Jersey, to the foot of 75th Street in New York City (about 35 miles). In 1917, utilizing the knowledge gained from ten years of advocating aviation, he built his first airplane, the Lawson Military Tractor 1 (MT-1) trainer, and founded the Lawson Aircraft Corporation. The company's plant was sited at Green Bay, Wisconsin. There he secured a contract and built the Lawson MT-2. He also designed the steel fuselage Lawson Armored Battler, which never got beyond the drafting board, given doubts within the Army aviation community and the signing of the armistice. After the war, in 1919 Lawson started a project to build America's first airline. He secured financial backing, and in five months he had built and demonstrated in flight his biplane airliner, the 18-passenger Lawson L-2. He demonstrated its capabilities in a 2000-mile multi-city tour from Milwaukee to Chicago-Toledo-Cleveland-Buffalo-Syracuse-New york City-Washington, D.C.-Collinsville-Dayton-Chicago and back to Milwaukee, creating a buzz of positive press. The publicity allowed him to secure an additional $1 million to build the 26-passenger Midnight Liner. The aircraft crashed on takeoff on its maiden flight. In late 1920, he secured government contracts for three airmail routes and to deliver ten war planes, but owing to the fall 1920 recession, he could not secure the necessary $100,000 in cash reserves called for in the contracts and had to decline them. In 1926, he started his last airliner, the 56-seat, two-tier Lawson super airliner. In this phase of his life, he was considered one of the leading thinkers in the budding American commercial aviation community, but his troubles with getting financial backing for his ideas led him to turn to economics, philosophy, and organization. Lawsonomy (1929–1954) In the 1920s, Lawson promoted health practices, including vegetarianism, and claimed to have found the secret of living to 200. He also developed his own highly unusual theories of physics, according to which such concepts as "penetrability", "suction and pressure" and "zig-zag-and-swirl" were discoveries on par with Einstein's theory of relativity. He published numerous books on these concepts, all set in a distinctive typography. He later propounded his own philosophy, Lawsonomy, and the Lawsonian religion. He also developed, during the Great Depression, the populist economic theory of "Direct Credits", according to which banks are the cause of all economic woes, the oppressors of both capital and labour. Lawson believed that the government should replace banks as the provider of loans to business and workers. He predicted the worldwide adoption of Lawsonian principles once "everybody understands this subject". His rallies and lectures attracted thousands of listeners in the early 1930s, mainly in the upper Midwest, but by the late 1930s the crowds had dwindled. His claims about his own greatness became increasingly hyperbolic. The Lawsonomy trilogy, considered by Lawson himself to be his intellectual masterpiece, is full of such self-referential statements as "About every two thousand years a new teacher with advanced intellectual equipment appears upon earth to lead the people a step or two nearer the one God of everybody". In 1943, he founded the Humanity Benefactor Foundation and University of Lawsonomy in Des Moines, on the site of Des Moines University, to spread his teachings and offer the degree of "Knowledgian", but after various IRS and other investigations it was closed and finally sold in 1954, the year of Lawson's death. His financial arrangements remain mysterious to this day, and in later years he seems to have owned little property, moving from city to city as a guest of his farflung acolytes. In 1952, he was brought before a United States Senate investigative committee on allegations that his organization had bought war surplus machines and then sold them for a profit, despite claiming non-profit status. His attempt to explain Lawsonomy to the senators ended in mutual frustration and bafflement. A farm near Racine, Wisconsin, is the only remaining university facility, although a tiny handful of churches may yet survive in places such as Wichita, Kansas. The large sign, formerly reading "University of Lawsonomy", was a familiar landmark for motorists in the region for many years and was visible from Interstate 94 about north of the Illinois state line, on the east side of the highway. A storm in the spring of 2009 destroyed the sign, although the supporting posts are still visible. On the northbound side of Interstate 94, a sign on the roof of the building nearest the freeway said "Study Natural Law" until being shingled over in October 2014. In 2018, the Town of Mount Pleasant paid $933,000 to purchase the property on the northbound side of Interstate 94 for the Foxconn project. All remaining buildings were demolished and removed. Lawsonomy maintains a small following to this day. See also List of topics characterized as pseudoscience References Further reading Henry, Lyell D. Zig-Zag-and Swirl: Alfred W. Lawson's Quest for Greatness. Iowa City: University of Iowa Press, 1991. Kossy, Donna. Kooks: A Guide to the Outer Limits of Human Belief. 2nd ed. Los Angeles: Feral House, 2001. Kuntz, Jerry. Baseball Fiends and Flying Machines: The Many Lives and Outrageous Times of George and Alfred Lawson. Jefferson, North Carolina: McFarland Publishing, 2009. Lawson, Alfred. Lawsonomy, vols. 1-3. Detroit: Humanity Benefactor Foundation, 1935–1939. External links Lawson Demo Flight Departed 93 Years Ago at Wisconsin Aviation Hall of Fame What in the heck is the University of Lawsonomy? – article about Lawson in a Milwaukee-area magazine End of flight – newspaper article about 1921 loss of first Lawson Airliner "ASME Milwaukee – History & Heritage" The Alfred W. Lawson papers at the American Heritage Center 1869 births 1954 deaths Lawsonomy Boston Beaneaters players Pittsburgh Alleghenys players Major League Baseball pitchers 19th-century baseball players Bloomington Blues players Wilmington Blue Hens players Harrisburg Ponies players Oakland Colonels players Pendleton Ho Hos players Spokane Bunchgrassers players Atlanta Firecrackers players Troy Trojans (minor league) players Sandusky Sandies players Albany Senators players Pawtucket Maroons players Norfolk Clams players Norfolk Crows players Sportspeople from London Minor league baseball managers Major League Baseball players from England Fitchburg (minor league baseball) players

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1298

https://en.wikipedia.org/wiki/Ames%2C%20Iowa

Ames, Iowa

Ames () is a city in Story County, Iowa, United States, located approximately north of Des Moines in central Iowa. It is best known as the home of Iowa State University (ISU), with leading agriculture, design, engineering, and veterinary medicine colleges. A United States Department of Energy national laboratory, Ames Laboratory, is located on the ISU campus. In 2020, Ames had a population of 66,427, making it the state's ninth largest city. Iowa State University was home to 33,391 students as of fall 2019, which make up approximately one half of the city's population. Ames also hosts United States Department of Agriculture (USDA) sites: the largest federal animal disease center in the United States, USDA's Agricultural Research Service's National Animal Disease Center (NADC), as well as, one of two national USDA sites for the Animal and Plant Health Inspection Service (APHIS), which comprises the National Veterinary Services Laboratory and the Center for Veterinary Biologics. Ames also hosts the headquarters for the Iowa Department of Transportation. History The city was formed in 1864 as a station stop on the Cedar Rapids and Missouri Railroad and was named after 19th century U.S. Congressman Oakes Ames of Massachusetts, who was influential in the building of the transcontinental railroad. Ames was founded by local resident Cynthia Olive Duff (née Kellogg) and railroad magnate John Insley Blair, near a location that was deemed favorable for a railroad crossing of the Skunk River. Geography Ames is located along the western edge of Story County, roughly north of the state capital, Des Moines, near the intersection of Interstate 35 and U.S. Route 30. A smaller highway, U.S. Route 69, passes through the town. Also passing through Ames is the cross country line of the Union Pacific Railroad and two small streams (the South Skunk River and Ioway Creek). According to the United States Census Bureau, the city has a total area of , of which is land and is water. Campustown Campustown is the neighborhood directly south of Iowa State University Central Campus bordered by Lincoln Way on the north. Campustown is a high-density mixed-use neighborhood that is home to many student apartments, nightlife venues, restaurants, and numerous other establishments, most of which are unique to Ames. Climate Ames has a humid continental climate (Köppen climate classification Dfa). On average, the warmest month is July and the coldest is January. The highest recorded temperature was in 1988 and the lowest was in 1996. Demographics 2010 census As of the census of 2010, there were 58,965 people, 22,759 households, and 9,959 families residing in the city. The population density was . There were 23,876 housing units at an average density of . The racial makeup of the city was 84.5% White, 3.4% African American, 0.2% Native American, 8.8% Asian, 1.1% from other races, and 2.0% from two or more races. Hispanic or Latino of any race were 3.4% of the population. There were 22,759 households, of which 19.1% had children under the age of 18 living with them, 35.6% were married couples living together, 5.4% had a female householder with no husband present, 2.7% had a male householder with no wife present, and 56.2% were non-families. 30.5% of all households were made up of individuals, and 6.2% had someone living alone who was 65 years of age or older. The average household size was 2.25 and the average family size was 2.82. The median age in the city was 23.8 years. 13.4% of residents were under the age of 18; 40.5% were between the ages of 18 and 24; 22.9% were from 25 to 44; 15% were from 45 to 64; and 8.1% were 65 years of age or older. The gender makeup of the city was 53.0% male and 47.0% female. 2000 census As of the census of 2000, there were 50,731 people, 18,085 households, and 8,970 families residing in the city. The population density was 2,352.3 people per square mile (908.1/km2). There were 18,757 housing units at an average density of 869.7 per square mile (335.7/km2). The racial makeup of the city was 87.34% White, 7.70% Asian, 2.65% African American, 0.04% Native American, 0.76% Pacific Islander and other races, and 1.36% from two or more races. Hispanic or Latino of any race were 1.98% of the population. There were 18,085 households, out of which 22.3% had children under the age of 18 living with them, 42.0% were married couples living together, 5.3% had a female householder with no husband present, and 50.4% were non-families. 28.5% of all households were made up of individuals, and 5.9% had someone living alone who was 65 years of age or older. The average household size was 2.30 and the average family size was 2.85. Age spread: 14.6% under the age of 18, 40.0% from 18 to 24, 23.7% from 25 to 44, 13.9% from 45 to 64, and 7.7% who were 65 years of age or older. The median age was 24 years. For every 100 females, there were 109.3 males. For every 100 females age 18 and over, there were 109.9 males. The median income for a household in the city was $36,042, and the median income for a family was $56,439. Males had a median income of $37,877 versus $28,198 for females. The per capita income for the city was $18,881. About 7.6% of families and 20.4% of the population were below the poverty line, including 9.2% of those under age 18 and 4.1% of those age 65 or over. Metropolitan area The U.S. Census Bureau designates the Ames MSA as encompassing all of Story County. While Ames is the largest city in Story County, the county seat is in the nearby city of Nevada, east of Ames. Ames metropolitan statistical area combined with the Boone, Iowa micropolitan statistical area (Boone County, Iowa) make up the larger Ames-Boone combined statistical area. Ames is the larger principal city of the Combined Statistical Area that includes all of Story County, Iowa and Boone County, Iowa. which had a combined population of 106,205 at the 2000 census. Economy Ames is home of Iowa State University of Science and Technology, a public land-grant and space-grant research university, and member of the prestigious Association of American Universities. At its founding in 1858, Iowa State was formerly known as the Iowa State College of Agriculture and Mechanic Arts. Ames is the home of the closely allied U.S. Department of Agriculture's National Animal Disease Center (See Ames strain), the U.S. Department of Energy's Ames Laboratory (a major materials research and development facility), and the main offices of the Iowa Department of Transportation. State and Federal institutions are the largest employers in Ames. Other area employers include a 3M manufacturing plant; Danfoss Power Solutions, a hydraulics manufacturer; Barilla, a pasta manufacturer; Ball, a manufacturer of canning jars and plastic bottles; Workiva, a global cloud computing company; Renewable Energy Group, America's largest producer of biomass-based diesel; and the National Farmers Organization. The Iowa State University Research Park is a not-for-profit, business development incubator located in Ames, and affiliated with Iowa State University. In 2015, Ames was ranked in the top 15 "Cities That Have Done the Best Since the Recession" by Bloomberg Businessweek. The Bureau of Labor Statistics ranked Ames and Boulder, CO as having the lowest unemployment rate (2.5%) of any metropolitan area in the US in 2016. By June 2018, unemployment in Ames had fallen even further, to 1.5%, and wage increases for workers were not keeping pace with rising rents. Top employers According to Ames's 2020 Comprehensive Annual Financial Report, the top employers in the city are: Arts and culture Velma Wallace Rayness Ames, Iowa was home to Gerard M. and Velma Wallace Rayness. Both artists taught art and were nationally recognized artists. Their art was exhibited nationally as well as abroad. Gerard died in the 1940s. Velma Wallace Rayness died in 1977. Velma Wallace Rayness usually signed her paintings "V.W. Rayness". Ames Historical Society Collects, preserves, and provides access to evidence of the history of Ames and its immediate vicinity from pre-settlement times to the present. Brunnier Art Museum (Scheman Building) Ames Public Library The Ames Public Library is a Carnegie library founded on October 20, 1904. It currently has 1,386,273 items in circulations, including 799,349 books and 586,924 multimedia items. The Octagon Center for the Arts The Center includes galleries, art classes, art studios, and retail shop. They sponsor the local street fair, The Octagon Arts Festival. Also have the Annual National Juried Exhibition Clay, Fiber, Paper Glass Metal, Wood. The Space for Ames Formally known as the Ames Progressive, The Space for Ames was a community space that served as an art gallery, music venue and classroom for community workshops. Popular culture The city is featured in the bestselling book The Girls from Ames written by Wall Street Journal columnist Jeffrey Zaslow. It examines the lives and friendships of several young girls who grew up in Ames and have moved on with their adult lives but still remain close. The city was featured in the episode "Heartache" of the television show Supernatural. The character "Kate Austen" from the television show Lost is from Ames. Sports Iowa Sports Foundation The Iowa State Cyclones play a variety of sports in the Ames area. The Iowa State Cyclones football team plays at Jack Trice Stadium in Ames. Also, the Cyclones' Men's and Women's Basketball teams and Volleyball teams play at Hilton Coliseum just across the street from Jack Trice Stadium. The Iowa State Cyclones are a charter member of the Big 12 Conference in all sports and compete in NCAA Division I-A. The Iowa State Women's Tennis is also well known and very successful. The Ames Figure Skating Club provides recreational to professional level skating opportunities. The club sponsors the Learn to Skate Program. Coaches provide on and off ice lessons or workshops. The club hosts the figure skating portion of the Iowa Games competition every summer. In the fall the club hosts Cyclone Country Championships. The Ames ISU ice arena also hosts the Iowa State Cyclones hockey team. The arena also hosts the Ames Little Cyclones hockey program for high school students and children in elementary or middle school. Education Much of the city is served by the Ames Community School District. A portion of northern Ames is zoned to the Gilbert Community School District. Public high school in Ames Ames High School: Grades 9–12 Public elementary/middle schools in Ames David Edwards Elementary: K-5 Abbie Sawyer Elementary School: Grades K-5 Kate Mitchell Elementary School: Grades K-5 Warren H. Meeker Elementary School: Grades K-5 Gertrude Fellows Elementary School: Grades K-5 Ames Middle School: Grades 6–8 Gilbert CSD students are zoned to Gilbert High School. Private schools in Ames Ames Christian School Saint Cecilia School (preK – 5th grade) Iowa State University Iowa State University of Science and Technology, more commonly known as Iowa State University (ISU), is a public land-grant and space-grant research university located in Ames. Iowa State University is the birthplace of the Atanasoff–Berry Computer, the world's first electronic digital computer. Iowa State has produced a number of astronauts, scientists, Nobel laureates, and Pulitzer Prize winners. Until 1945 it was known as the Iowa State College of Agriculture and Mechanic Arts. The university is a member of the American Association of Universities and the Big 12 Conference. ISU is the nation's first designated land-grant university In 1856, the Iowa General Assembly enacted legislation to establish the State Agricultural College and Model Farm. Story County was chosen as the location on June 21, 1859, from proposals by Johnson, Kossuth, Marshall, Polk, and Story counties. When Iowa accepted the provisions of the Morrill Act of 1862, Iowa State became the first institution in nation designated as a land-grant college. The institution was coeducational from the first preparatory class admitted in 1868. The formal admitting of students began the following year, and the first graduating class of 1872 consisted of 24 men and 2 women. The first building on the Iowa State campus was Farm House. Built in the 1860s, it currently serves as a museum and National Historic Landmark. Today, Iowa State has over 60 notable buildings, including Beardshear Hall, Morrill Hall, Memorial Union, Catt Hall, Curtiss Hall, Carver Hall, Parks Library, the Campanile, Hilton Coliseum, C.Y. Stephens Auditorium, Fisher Theater, Jack Trice Stadium, Lied Recreation Center, numerous residence halls, and many buildings specific to ISU's many different majors and colleges. The official mascot for ISU is Cy the Cardinal. The official school colors are cardinal and gold. The Iowa State Cyclones play in the NCAA's Division I-A as a member of the Big 12 Conference. Media Online and newsprint Ames Tribune, Tuesday-Sunday paper produced in Ames. Iowa State Daily, independent student newspaper produced at Iowa State University. The Des Moines Register also provides extensive coverage of Iowa news and sports to Ames. Story County Sun, weekly newspaper that covers the entire county published in Ames. Radio stations licensed to Ames KURE, student radio operated at Iowa State University. WOI-FM, Iowa Public Radio's flagship "Studio One" station, broadcasting an NPR news format during the day and a music format in the evening, owned and operated at Iowa State University. WOI (AM), Iowa Public Radio's flagship station delivering a 24-hour news format consisting mainly of NPR programming, owned and operated at Iowa State University. KOEZ, Adult Contemporary station licensed to Ames, but operated in Des Moines. KCYZ, Hot Adult Contemporary station owned and operated by Clear Channel in Ames. KASI, news/talk station owned and operated by Clear Channel in Ames. KNWM-FM, Contemporary Christian Madrid/Ames station owned and operated by the University of Northwestern – St. Paul - simulcast with KNWI-FM Osceola/Des Moines KHOI, Community Radio station licensed to Story City with studios in Ames. KHOI broadcasts music and local public affairs programs and is affiliated with the Pacifica Radio network. Ames is also served by stations in the Des Moines media market, which includes Clear Channel's 50,000-watt talk station WHO, music stations KAZR, KDRB, KGGO, KKDM, KHKI, KIOA, KJJY, KRNT, KSPZ and KSTZ, talk station KWQW, and sports stations KXNO and KXNO-FM. Television Like radio, Ames is served by the Des Moines media market. WOI-DT, the ABC affiliate in central Iowa, was originally owned and operated by Iowa State University until the 1990s. The station is still licensed to Ames, but studio's are located in West Des Moines. Other stations serving Ames include KCCI, KDIN-TV, WHO-DT, KCWI-TV, KDMI, KDSM-TV and KFPX-TV. Channel 12 is owned by the City of Ames and overseen by the City Manager's Office. The channel broadcasts meetings for city council as well as other city government councils and boards. Channel 12 also produces its own original content focused on news and other happenings in Ames. Channel 12 has won various regional and national awards including a NATOA Government Programming Award and a Telly Award. Channel 12's goals are "To provide quality programming to the citizens of Ames that educates and informs about city government issues" and "To provide live coverage and rebroadcasts of council and commission meetings." Channel 16 serves as Ames' public access TV channel. "The purpose of Ames Public Access TV (Channel 16) is to provide residents the opportunity to broadcast locally produced programs on cable television. APATV provides cablecasting of non-commercial, public access programming independently produced by professionals or non-professionals in either a VHS or DVD format. This service is provided on a first-come-first-served, non-discriminatory, non monopolistic basis. Other services include video messaging to serve as a community calendar." Infrastructure Transportation The town is served by U.S. Highways 30 and 69 and Interstate 35. Ames is the only town in Iowa with a population of greater than 50,000 that does not have a state highway serving it. , Ames currently has three roundabouts constructed on University Avenue/530th Avenue. The first is at the intersection of Airport Road (Oakwood Rd.) and University Avenue, the second at the intersection of Cottonwood Road and 530th Avenue and the third at Collaboration Place and 530th Avenue. Ames was serviced by the Fort Dodge, Des Moines and Southern Railroad via a branch from Kelley to Iowa State and to downtown Ames. The tracks were removed in the 1960s. The Chicago and North Western Transportation Company twin mainline runs east and west bisecting the town and running just south of the downtown business district. The C&NW used to operate a branch to Des Moines. This line was removed in the 1980s when the Spine Line through the nearby city of Nevada was purchased from the Rock Island Railroad after its bankruptcy. The Union Pacific, successor to the C&NW, still runs 60–70 trains a day through Ames on twin mainlines, which leads to some traffic delays. There is also a branch to Eagle Grove that leaves Ames to the north. The Union Pacific maintains a small yard called Ames Yard east of Ames between Ames and Nevada. Ames has been testing automatic train horns at several of its crossings. These directional horns which are focused down the streets are activated when the crossing signals turn on and are shut off after the train crosses the crossing. This system cancels out the need for the trains to blow their horns. Train noise had been a problem in the residential areas to the west and northwest of downtown. Ames Municipal Airport is located southeast of the city. The current (and only) fixed-base operator is Hap's Air Service, a company which has been based at the airport since 1975. The airport has two runways – 01/19, which is , and 13/31, which is . The City of Ames offers a transit system throughout town, called CyRide, that is funded jointly by Iowa State University, the ISU Government of the Student Body, and the City of Ames. Rider fares are subsidized through this funding, and are free for children under five. Students pay a set cost as part of their tuition. In 2009, the Ames metropolitan statistical area (MSA) ranked as the third highest in the United States for percentage of commuters who walked to work (10.4 percent). Ames has the headquarters of the Iowa Department of Transportation. Health care Ames is served by Mary Greeley Medical Center, a 220-bed regional referral hospital which is adjacent to McFarland Clinic PC, central Iowa's largest physician-owned multi-specialty clinic, and also Iowa Heart Center. Parks and recreation On September 10, 2019 the City of Ames proposed a $29,000,000 bond for building a fitness center called the Healthy Life Center. It failed to pass. Iowa State University owns the land it was to be built on. Notable people This is a list of notable people associated with Ames, Iowa arranged by career and in alphabetical order. Acting Evan Helmuth, actor (Fever Pitch, The Devil Inside) Artists and photographers John E. Buck, sculptor Margaret Lloyd, opera singer Laurel Nakadate, American video artist, filmmaker and photographer Velma Wallace Rayness (1896–1977), author and artist, painted "Roof Tops in Fall" Brian Smith, Pulitzer Prize-winning photographer, born July 16, 1959 Musicians John Darnielle, musician from indie rock band The Mountain Goats; former Ames resident Envy Corps, indie rock band Leslie Hall, electronic rap musician/Gem Sweater collector, born in Ames in 1981 Peter Schickele, musician, born in Ames in 1935 Richie Hayward, drummer and founding member of the band Little Feat; former Ames resident and graduate of Ames High School Journalists Robert Bartley, editorial page editor of The Wall Street Journal and a Presidential Medal of Freedom recipient; raised in Ames and ISU graduate Wally Bruner, ABC News journalist and television host Michael Gartner, former president of NBC News; retired to own and publish the Ames Tribune Politicians Ruth Bascom, Mayor of Eugene, Oregon Edward Mezvinsky, former U.S. Congressman; father-in-law of Chelsea Clinton; raised in Ames Bee Nguyen, Georgia (U.S. state) state representative Bob Walkup, Mayor of Tucson, Arizona Lee Teng-hui, President of the Republic of China, ISU graduate Henry A. Wallace, 11th United States Secretary of Agriculture, 10th United States Secretary of Commerce, and 33rd Vice President of the United States, ISU graduate; lived in Ames from 1892 - 1896 Sports Harrison Barnes, NBA player, 2015 NBA champion, 2016 U.S. Olympic gold medalist, Ames HS graduate Joe Burrow, NFL player, 2019 Heisman Trophy Award Winner, 2020 CFP National Championship Winner. Born in Ames, but grew up in The Plains, Ohio Juan Sebastián Botero, soccer player Kip Corrington, NFL player Dick Gibbs, NBA player, Ames HS graduate Terry Hoage, NFL player Fred Hoiberg, retired NBA basketball player; raised in Ames, ISU graduate, former ISU basketball coach, former coach of the Chicago Bulls and current Nebraska men’s basketball coach. Doug McDermott, basketball player, Ames HS graduate Cael Sanderson, U.S. Olympic gold medalist; undefeated, four-time NCAA wrestling champion; former ISU wrestling coach and alumnus Herb Sies, pro football player and coach Billy Sunday, evangelist and Major League Baseball player; born in Ames in 1863 Fred Tisue, Olympian water polo player Scientists George Washington Carver, inventor, Iowa State University alumnus and professor Laurel Blair Salton Clark, astronaut, died on STS-107 Charles W. "Chuck" Durham, civil engineer, philanthropist, civic leader, former CEO and chairman Emeritus of HDR, Inc.; raised in Ames Lyle Goodhue, scientist, lived and studied here 1925–1934 Dan Shechtman, awarded 2011 Nobel Prize in Chemistry for "the discovery of quasicrystals"; Professor of Materials Science at Iowa State University (2004–present) and Associate at the Department of Energy's Ames Laboratory George W. Snedecor, statistician, founder of first academic department of statistics in the United States at Iowa State University Writers and poets Ann Cotten, poet, born in Ames, grew up in Vienna Brian Evenson, author Jane Espenson, writer and producer for television, including Buffy the Vampire Slayer and Star Trek: The Next Generation, grew up in Ames Michelle Hoover, author, born in Ames Meg Johnson, poet and dancer Fern Kupfer, author Joseph Geha, author Ted Kooser, U.S. Poet Laureate; raised in Ames and ISU graduate John Madson, freelance naturalist of tallgrass prairie ecosystems Sara Paretsky, author of the V.I. Warshawski mysteries; born in Ames in 1947 Jane Smiley, Pulitzer Prize-winning novelist; former instructor at ISU (1981–1996); used ISU as the basis for her novel Moo Neal Stephenson, author, grew up in Ames Hugh Young, coauthor of University Physics textbook Lincoln Peirce, cartoonist/writer of the Big Nate comics and books Other Neva Morris, at her death (2010) second-oldest person in the world and oldest American at the age of 114 years; lived in Ames her entire life Nate Staniforth, magician Other topics Awards and Accolades No. 1 Best U.S. Job Market (CNBC, 2018) No. 1 Best College Towns in America (24/7 Wall St., 2018) No. 1 Top Cities for Career Opportunities in 2018 (SmartAsset, 2018) No. 2 Top 10 Best College Towns (Livability, 2018) Top 5 Small Metro Areas for Retirees to Age Successfully (Investopedia, 2018) The Most Fitness Friendly Places of 2018 (SmartAsset, 2017) Best Public High School in the State (24/7 Wall St., 2017) Technology Community of the Year (Technology Association of Iowa, 2017) Top 5 Small Metro Areas for Successful Aging (NCOA, 2017) Top 3 Cities Where Job Growth is Happening (NationalSwell, 2017) Best School District in Iowa (Business Insider, 2017) Best School District in the State (Niche, 2017) No. 8 of the 25 Best Cities for Entrepreneurs (Entrepreneur Magazine, 2017) Best Places to Live 2016 (Money, 2016) Best Small Cities for New Grads (Online Degrees, 2016) Most Charitable Cities (The Beacon, 2016) No. 9 of the Top 10 College Towns to Live In (SmartAsset, 2016) Top 10 Cities for Career Opportunities in 2016 (SmartAsset, 2016) No. 3 Healthiest Cities in America (24/7 Wall St., 2016) Best College in Iowa, Iowa State University (Money, 2016) No. 3 Best College Towns in America (Business Insider, 2016) No. 5 Medium City of Top U.S. Cities for Public Transportation (Save on Energy, 2016) U.S. City with the Lowest Unemployment Rate (Forbes, 2016) No. 4 Best Small City to Make a Living (MoneyGeek, 2016) No. 35 of the Top 100 Best Places to Live in 2016 (Livability.com, 2016) No. 3 Best-Performing Small Cities: Where America's Jobs are Created and Sustained List (Milken Institute, 2015) No. 8 Best Cities in America to Get a Job in 2015 (Business Insider, 2015) No. 1 of the 15 Cities That Have Done the Best Since the Recession (Bloomberg, 2015) Top 25 Nationally, Best Places for STEM Grads (Nerdwallet, 2015) No. 8 Best Towns for Millennials in America (Niche Rankings, 2015) No. 1 Best College Town in 2014 (Livability.com, 2014) In 2010, Ames was ranked ninth on CNNMoney's "Best Places to Live" list. Politics Iowa is a political "battleground state" that has trended slightly Republican in recent years, and Ames, like Iowa City, trends Democratic. Iowa is the first caucus state and Ames is a college town. It is the site of many political appearances, debates and events, especially during election years. From 1979 through 2011, Ames was the location of the Ames Straw Poll, which was held every August prior to a presidential election year in which the Republican presidential nomination was undecided (meaning there was no Republican president running for re-election—as in 2011, 2007, 1999, 1995, 1987, and 1979). The poll would gauge support for the various Republican candidates amongst attendees of a fundraising dinner benefiting the Iowa Republican Party. The straw poll was frequently seen by national media and party insiders as a first test of organizational strength in Iowa. In 2015, the straw poll was to be moved to nearby Boone before the Iowa Republican Party eventually decided to cancel it altogether. See also Ames process North Grand Mall Reiman Gardens References External links Official Ames City Website Ames Campustown official site The Main Street Cultural District City Data Detailed Statistical Data and more about Ames Cities in Iowa Cities in Story County, Iowa Populated places established in 1864 1864 establishments in Iowa

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1309

https://en.wikipedia.org/wiki/Almost%20all

Almost all

In mathematics, the term "almost all" means "all but a negligible amount". More precisely, if is a set, "almost all elements of " means "all elements of but those in a negligible subset of ". The meaning of "negligible" depends on the mathematical context; for instance, it can mean finite, countable, or null. In contrast, "almost no" means "a negligible amount"; that is, "almost no elements of " means "a negligible amount of elements of ". Meanings in different areas of mathematics Prevalent meaning Throughout mathematics, "almost all" is sometimes used to mean "all (elements of an infinite set) but finitely many". This use occurs in philosophy as well. Similarly, "almost all" can mean "all (elements of an uncountable set) but countably many". Examples: Almost all positive integers are greater than 1,000,000,000,000. Almost all prime numbers are odd (as 2 is the only exception). Almost all polyhedra are irregular (as there are only nine exceptions: the five platonic solids and the four Kepler–Poinsot polyhedra). If P is a nonzero polynomial, then P(x) ≠ 0 for almost all x (if not all x). Meaning in measure theory When speaking about the reals, sometimes "almost all" can mean "all reals but a null set". Similarly, if S is some set of reals, "almost all numbers in S" can mean "all numbers in S but those in a null set". The real line can be thought of as a one-dimensional Euclidean space. In the more general case of an n-dimensional space (where n is a positive integer), these definitions can be generalised to "all points but those in a null set" or "all points in S but those in a null set" (this time, S is a set of points in the space). Even more generally, "almost all" is sometimes used in the sense of "almost everywhere" in measure theory, or in the closely related sense of "almost surely" in probability theory. Examples: In a measure space, such as the real line, countable sets are null. The set of rational numbers is countable, and thus almost all real numbers are irrational. As Georg Cantor proved in his first set theory article, the set of algebraic numbers is countable as well, so almost all reals are transcendental. Almost all reals are normal. The Cantor set is null as well. Thus, almost all reals are not members of it even though it is uncountable. The derivative of the Cantor function is 0 for almost all numbers in the unit interval. It follows from the previous example because the Cantor function is locally constant, and thus has derivative 0 outside the Cantor set. Meaning in number theory In number theory, "almost all positive integers" can mean "the positive integers in a set whose natural density is 1". That is, if A is a set of positive integers, and if the proportion of positive integers in A below n (out of all positive integers below n) tends to 1 as n tends to infinity, then almost all positive integers are in A. More generally, let S be an infinite set of positive integers, such as the set of even positive numbers or the set of primes, if A is a subset of S, and if the proportion of elements of S below n that are in A (out of all elements of S below n) tends to 1 as n tends to infinity, then it can be said that almost all elements of S are in A. Examples: The natural density of cofinite sets of positive integers is 1, so each of them contains almost all positive integers. Almost all positive integers are composite. Almost all even positive numbers can be expressed as the sum of two primes. Almost all primes are isolated. Moreover, for every positive integer , almost all primes have prime gaps of more than both to their left and to their right; that is, there is no other primes between and . Meaning in graph theory In graph theory, if A is a set of (finite labelled) graphs, it can be said to contain almost all graphs, if the proportion of graphs with n vertices that are in A tends to 1 as n tends to infinity. However, it is sometimes easier to work with probabilities, so the definition is reformulated as follows. The proportion of graphs with n vertices that are in A equals the probability that a random graph with n vertices (chosen with the uniform distribution) is in A, and choosing a graph in this way has the same outcome as generating a graph by flipping a coin for each pair of vertices to decide whether to connect them. Therefore, equivalently to the preceding definition, the set A contains almost all graphs if the probability that a coin flip-generated graph with n vertices is in A tends to 1 as n tends to infinity. Sometimes, the latter definition is modified so that the graph is chosen randomly in some other way, where not all graphs with n vertices have the same probability, and those modified definitions are not always equivalent to the main one. The use of the term "almost all" in graph theory is not standard; the term "asymptotically almost surely" is more commonly used for this concept. Example: Almost all graphs are asymmetric. Almost all graphs have diameter 2. Meaning in topology In topology and especially dynamical systems theory (including applications in economics), "almost all" of a topological space's points can mean "all of the space's points but those in a meagre set". Some use a more limited definition, where a subset only contains almost all of the space's points if it contains some open dense set. Example: Given an irreducible algebraic variety, the properties that hold for almost all points in the variety are exactly the generic properties. This is due to the fact that in an irreducible algebraic variety equipped with the Zariski topology, all nonempty open sets are dense. Meaning in algebra In abstract algebra and mathematical logic, if U is an ultrafilter on a set X, "almost all elements of X" sometimes means "the elements of some element of U". For any partition of X into two disjoint sets, one of them will necessarily contain almost all elements of X. It is possible to think of the elements of a filter on X as containing almost all elements of X, even if it isn't an ultrafilter. Proofs See also Almost Almost everywhere Almost surely References Primary sources Secondary sources Mathematical terminology

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1317

https://en.wikipedia.org/wiki/Antimatter

Antimatter

In modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding particles in "ordinary" matter. Minuscule numbers of antiparticles are generated daily at particle acceleratorstotal artificial production has been only a few nanogramsand in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling. Theoretically, a particle and its antiparticle (for example, a proton and an antiproton) have the same mass, but opposite electric charge, and other differences in quantum numbers. For example, a proton has positive charge, while an antiproton has negative charge. A collision between any particle and its anti-particle partner leads to their mutual annihilation, giving rise to various proportions of intense photons (gamma rays), neutrinos, and sometimes less-massive particleantiparticle pairs. The majority of the total energy of annihilation emerges in the form of ionizing radiation. If surrounding matter is present, the energy content of this radiation will be absorbed and converted into other forms of energy, such as heat or light. The amount of energy released is usually proportional to the total mass of the collided matter and antimatter, in accordance with the notable mass–energy equivalence equation, . Antimatter particles bind with each other to form antimatter, just as ordinary particles bind to form normal matter. For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom. The nuclei of antihelium have been artificially produced, albeit with difficulty, and are the most complex anti-nuclei so far observed. Physical principles indicate that complex antimatter atomic nuclei are possible, as well as anti-atoms corresponding to the known chemical elements. There is strong evidence that the observable universe is composed almost entirely of ordinary matter, as opposed to an equal mixture of matter and antimatter. This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics. The process by which this inequality between matter and antimatter particles developed is called baryogenesis. Definitions Antimatter particles can be defined by their negative baryon number or lepton number, while "normal" (non-antimatter) matter particles have a positive baryon or lepton number. These two classes of particles are the antiparticle partners of each other. A "positron" is the antimatter equivalent of the "electron". The French term contra-terrene led to the initialism "C.T." and the science fiction term "seetee", as used in such novels as Seetee Ship. Conceptual history The idea of negative matter appears in past theories of matter that have now been abandoned. Using the once popular vortex theory of gravity, the possibility of matter with negative gravity was discussed by William Hicks in the 1880s. Between the 1880s and the 1890s, Karl Pearson proposed the existence of "squirts" and sinks of the flow of aether. The squirts represented normal matter and the sinks represented negative matter. Pearson's theory required a fourth dimension for the aether to flow from and into. The term antimatter was first used by Arthur Schuster in two rather whimsical letters to Nature in 1898, in which he coined the term. He hypothesized antiatoms, as well as whole antimatter solar systems, and discussed the possibility of matter and antimatter annihilating each other. Schuster's ideas were not a serious theoretical proposal, merely speculation, and like the previous ideas, differed from the modern concept of antimatter in that it possessed negative gravity. The modern theory of antimatter began in 1928, with a paper by Paul Dirac. Dirac realised that his relativistic version of the Schrödinger wave equation for electrons predicted the possibility of antielectrons. These were discovered by Carl D. Anderson in 1932 and named positrons from "positive electron". Although Dirac did not himself use the term antimatter, its use follows on naturally enough from antielectrons, antiprotons, etc. A complete periodic table of antimatter was envisaged by Charles Janet in 1929. The Feynman–Stueckelberg interpretation states that antimatter and antiparticles are regular particles traveling backward in time. Notation One way to denote an antiparticle is by adding a bar over the particle's symbol. For example, the proton and antiproton are denoted as and , respectively. The same rule applies if one were to address a particle by its constituent components. A proton is made up of quarks, so an antiproton must therefore be formed from antiquarks. Another convention is to distinguish particles by positive and negative electric charge. Thus, the electron and positron are denoted simply as and respectively. To prevent confusion, however, the two conventions are never mixed. Properties Theorized anti-gravitational properties of antimatter are currently being tested at the AEGIS experiment at CERN. Antimatter coming in contact with matter will annihilate both while leaving behind pure energy. Research is needed to study the possible gravitational effects between matter and antimatter, and between antimatter and antimatter. However research is difficult considering when the two meet they annihilate, along with the current difficulties of capturing and containing antimatter. There are compelling theoretical reasons to believe that, aside from the fact that antiparticles have different signs on all charges (such as electric and baryon charges), matter and antimatter have exactly the same properties. This means a particle and its corresponding antiparticle must have identical masses and decay lifetimes (if unstable). It also implies that, for example, a star made up of antimatter (an "antistar") will shine just like an ordinary star. This idea was tested experimentally in 2016 by the ALPHA experiment, which measured the transition between the two lowest energy states of antihydrogen. The results, which are identical to that of hydrogen, confirmed the validity of quantum mechanics for antimatter. Origin and asymmetry Most matter observable from the Earth seems to be made of matter rather than antimatter. If antimatter-dominated regions of space existed, the gamma rays produced in annihilation reactions along the boundary between matter and antimatter regions would be detectable. Antiparticles are created everywhere in the universe where high-energy particle collisions take place. High-energy cosmic rays impacting Earth's atmosphere (or any other matter in the Solar System) produce minute quantities of antiparticles in the resulting particle jets, which are immediately annihilated by contact with nearby matter. They may similarly be produced in regions like the center of the Milky Way and other galaxies, where very energetic celestial events occur (principally the interaction of relativistic jets with the interstellar medium). The presence of the resulting antimatter is detectable by the two gamma rays produced every time positrons annihilate with nearby matter. The frequency and wavelength of the gamma-rays indicate that each carries 511 keV of energy (that is, the rest mass of an electron multiplied by c2). Observations by the European Space Agency's INTEGRAL satellite may explain the origin of a giant antimatter cloud surrounding the galactic center. The observations show that the cloud is asymmetrical and matches the pattern of X-ray binaries (binary star systems containing black holes or neutron stars), mostly on one side of the galactic center. While the mechanism is not fully understood, it is likely to involve the production of electron–positron pairs, as ordinary matter gains kinetic energy while falling into a stellar remnant. Antimatter may exist in relatively large amounts in far-away galaxies due to cosmic inflation in the primordial time of the universe. Antimatter galaxies, if they exist, are expected to have the same chemistry and absorption and emission spectra as normal-matter galaxies, and their astronomical objects would be observationally identical, making them difficult to distinguish. NASA is trying to determine if such galaxies exist by looking for X-ray and gamma-ray signatures of annihilation events in colliding superclusters. In October 2017, scientists working on the BASE experiment at CERN reported a measurement of the antiproton magnetic moment to a precision of 1.5 parts per billion. It is consistent with the most precise measurement of the proton magnetic moment (also made by BASE in 2014), which supports the hypothesis of CPT symmetry. This measurement represents the first time that a property of antimatter is known more precisely than the equivalent property in matter. Antimatter quantum interferometry has been first demonstrated in the L-NESS Laboratory of R. Ferragut in Como (Italy), by a group led by M. Giammarchi. Natural production Positrons are produced naturally in β+ decays of naturally occurring radioactive isotopes (for example, potassium-40) and in interactions of gamma quanta (emitted by radioactive nuclei) with matter. Antineutrinos are another kind of antiparticle created by natural radioactivity (β− decay). Many different kinds of antiparticles are also produced by (and contained in) cosmic rays. In January 2011, research by the American Astronomical Society discovered antimatter (positrons) originating above thunderstorm clouds; positrons are produced in terrestrial gamma-ray flashes created by electrons accelerated by strong electric fields in the clouds. Antiprotons have also been found to exist in the Van Allen Belts around the Earth by the PAMELA module. Antiparticles are also produced in any environment with a sufficiently high temperature (mean particle energy greater than the pair production threshold). It is hypothesized that during the period of baryogenesis, when the universe was extremely hot and dense, matter and antimatter were continually produced and annihilated. The presence of remaining matter, and absence of detectable remaining antimatter, is called baryon asymmetry. The exact mechanism that produced this asymmetry during baryogenesis remains an unsolved problem. One of the necessary conditions for this asymmetry is the violation of CP symmetry, which has been experimentally observed in the weak interaction. Recent observations indicate black holes and neutron stars produce vast amounts of positron-electron plasma via the jets. Observation in cosmic rays Satellite experiments have found evidence of positrons and a few antiprotons in primary cosmic rays, amounting to less than 1% of the particles in primary cosmic rays. This antimatter cannot all have been created in the Big Bang, but is instead attributed to have been produced by cyclic processes at high energies. For instance, electron-positron pairs may be formed in pulsars, as a magnetized neutron star rotation cycle shears electron-positron pairs from the star surface. Therein the antimatter forms a wind that crashes upon the ejecta of the progenitor supernovae. This weathering takes place as "the cold, magnetized relativistic wind launched by the star hits the non-relativistically expanding ejecta, a shock wave system forms in the impact: the outer one propagates in the ejecta, while a reverse shock propagates back towards the star." The former ejection of matter in the outer shock wave and the latter production of antimatter in the reverse shock wave are steps in a space weather cycle. Preliminary results from the presently operating Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station show that positrons in the cosmic rays arrive with no directionality, and with energies that range from 10 GeV to 250 GeV. In September, 2014, new results with almost twice as much data were presented in a talk at CERN and published in Physical Review Letters. A new measurement of positron fraction up to 500 GeV was reported, showing that positron fraction peaks at a maximum of about 16% of total electron+positron events, around an energy of 275 ± 32 GeV. At higher energies, up to 500 GeV, the ratio of positrons to electrons begins to fall again. The absolute flux of positrons also begins to fall before 500 GeV, but peaks at energies far higher than electron energies, which peak about 10 GeV. These results on interpretation have been suggested to be due to positron production in annihilation events of massive dark matter particles. Cosmic ray antiprotons also have a much higher energy than their normal-matter counterparts (protons). They arrive at Earth with a characteristic energy maximum of 2 GeV, indicating their production in a fundamentally different process from cosmic ray protons, which on average have only one-sixth of the energy. There is an ongoing search for larger antimatter nuclei, such as antihelium nuclei (that is, anti-alpha particles), in cosmic rays. The detection of natural antihelium could imply the existence of large antimatter structures such as an antistar. A prototype of the AMS-02 designated AMS-01, was flown into space aboard the on STS-91 in June 1998. By not detecting any antihelium at all, the AMS-01 established an upper limit of 1.1×10−6 for the antihelium to helium flux ratio. AMS-02 revealed in December 2016 that it had discovered a few signals consistent with antihelium nuclei amidst several billion helium nuclei. The result remains to be verified, and the team is currently trying to rule out contamination. Artificial production Positrons Positrons were reported in November 2008 to have been generated by Lawrence Livermore National Laboratory in larger numbers than by any previous synthetic process. A laser drove electrons through a gold target's nuclei, which caused the incoming electrons to emit energy quanta that decayed into both matter and antimatter. Positrons were detected at a higher rate and in greater density than ever previously detected in a laboratory. Previous experiments made smaller quantities of positrons using lasers and paper-thin targets; newer simulations showed that short bursts of ultra-intense lasers and millimeter-thick gold are a far more effective source. Antiprotons, antineutrons, and antinuclei The existence of the antiproton was experimentally confirmed in 1955 by University of California, Berkeley physicists Emilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics. An antiproton consists of two up antiquarks and one down antiquark (). The properties of the antiproton that have been measured all match the corresponding properties of the proton, with the exception of the antiproton having opposite electric charge and magnetic moment from the proton. Shortly afterwards, in 1956, the antineutron was discovered in proton–proton collisions at the Bevatron (Lawrence Berkeley National Laboratory) by Bruce Cork and colleagues. In addition to antibaryons, anti-nuclei consisting of multiple bound antiprotons and antineutrons have been created. These are typically produced at energies far too high to form antimatter atoms (with bound positrons in place of electrons). In 1965, a group of researchers led by Antonino Zichichi reported production of nuclei of antideuterium at the Proton Synchrotron at CERN. At roughly the same time, observations of antideuterium nuclei were reported by a group of American physicists at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Antihydrogen atoms In 1995, CERN announced that it had successfully brought into existence nine hot antihydrogen atoms by implementing the SLAC/Fermilab concept during the PS210 experiment. The experiment was performed using the Low Energy Antiproton Ring (LEAR), and was led by Walter Oelert and Mario Macri. Fermilab soon confirmed the CERN findings by producing approximately 100 antihydrogen atoms at their facilities. The antihydrogen atoms created during PS210 and subsequent experiments (at both CERN and Fermilab) were extremely energetic and were not well suited to study. To resolve this hurdle, and to gain a better understanding of antihydrogen, two collaborations were formed in the late 1990s, namely, ATHENA and ATRAP. In 1999, CERN activated the Antiproton Decelerator, a device capable of decelerating antiprotons from to  – still too "hot" to produce study-effective antihydrogen, but a huge leap forward. In late 2002 the ATHENA project announced that they had created the world's first "cold" antihydrogen. The ATRAP project released similar results very shortly thereafter. The antiprotons used in these experiments were cooled by decelerating them with the Antiproton Decelerator, passing them through a thin sheet of foil, and finally capturing them in a Penning–Malmberg trap. The overall cooling process is workable, but highly inefficient; approximately 25 million antiprotons leave the Antiproton Decelerator and roughly 25,000 make it to the Penning–Malmberg trap, which is about or 0.1% of the original amount. The antiprotons are still hot when initially trapped. To cool them further, they are mixed into an electron plasma. The electrons in this plasma cool via cyclotron radiation, and then sympathetically cool the antiprotons via Coulomb collisions. Eventually, the electrons are removed by the application of short-duration electric fields, leaving the antiprotons with energies less than . While the antiprotons are being cooled in the first trap, a small cloud of positrons is captured from radioactive sodium in a Surko-style positron accumulator. This cloud is then recaptured in a second trap near the antiprotons. Manipulations of the trap electrodes then tip the antiprotons into the positron plasma, where some combine with antiprotons to form antihydrogen. This neutral antihydrogen is unaffected by the electric and magnetic fields used to trap the charged positrons and antiprotons, and within a few microseconds the antihydrogen hits the trap walls, where it annihilates. Some hundreds of millions of antihydrogen atoms have been made in this fashion. In 2005, ATHENA disbanded and some of the former members (along with others) formed the ALPHA Collaboration, which is also based at CERN. The ultimate goal of this endeavour is to test CPT symmetry through comparison of the atomic spectra of hydrogen and antihydrogen (see hydrogen spectral series). In 2016, a new antiproton decelerator and cooler called ELENA (Extra Low ENergy Antiproton decelerator) was built. It takes the antiprotons from the antiproton decelerator and cools them to 90 keV, which is "cold" enough to study. This machine works by using high energy and accelerating the particles within the chamber. More than one hundred antiprotons can be captured per second, a huge improvement, but it would still take several thousand years to make a nanogram of antimatter. Most of the sought-after high-precision tests of the properties of antihydrogen could only be performed if the antihydrogen were trapped, that is, held in place for a relatively long time. While antihydrogen atoms are electrically neutral, the spins of their component particles produce a magnetic moment. These magnetic moments can interact with an inhomogeneous magnetic field; some of the antihydrogen atoms can be attracted to a magnetic minimum. Such a minimum can be created by a combination of mirror and multipole fields. Antihydrogen can be trapped in such a magnetic minimum (minimum-B) trap; in November 2010, the ALPHA collaboration announced that they had so trapped 38 antihydrogen atoms for about a sixth of a second. This was the first time that neutral antimatter had been trapped. On 26 April 2011, ALPHA announced that they had trapped 309 antihydrogen atoms, some for as long as 1,000 seconds (about 17 minutes). This was longer than neutral antimatter had ever been trapped before. ALPHA has used these trapped atoms to initiate research into the spectral properties of the antihydrogen. The biggest limiting factor in the large-scale production of antimatter is the availability of antiprotons. Recent data released by CERN states that, when fully operational, their facilities are capable of producing ten million antiprotons per minute. Assuming a 100% conversion of antiprotons to antihydrogen, it would take 100 billion years to produce 1 gram or 1 mole of antihydrogen (approximately atoms of anti-hydrogen). However, CERN only produces 1% of the anti-matter Fermilab does, and neither are designed to produce anti-matter. According to Gerald Jackson, using technology already in use today we are capable of producing and capturing 20 grams of anti-matter particles per year at a yearly cost of 670 million dollars per facility. Antihelium Antihelium-3 nuclei () were first observed in the 1970s in proton–nucleus collision experiments at the Institute for High Energy Physics by Y. Prockoshkin's group (Protvino near Moscow, USSR) and later created in nucleus–nucleus collision experiments. Nucleus–nucleus collisions produce antinuclei through the coalescence of antiprotons and antineutrons created in these reactions. In 2011, the STAR detector reported the observation of artificially created antihelium-4 nuclei (anti-alpha particles) () from such collisions. The Alpha Magnetic Spectrometer on the International Space Station has, as of 2021, recorded eight events that seem to indicate the detection of antihelium-3. Preservation Antimatter cannot be stored in a container made of ordinary matter because antimatter reacts with any matter it touches, annihilating itself and an equal amount of the container. Antimatter in the form of charged particles can be contained by a combination of electric and magnetic fields, in a device called a Penning trap. This device cannot, however, contain antimatter that consists of uncharged particles, for which atomic traps are used. In particular, such a trap may use the dipole moment (electric or magnetic) of the trapped particles. At high vacuum, the matter or antimatter particles can be trapped and cooled with slightly off-resonant laser radiation using a magneto-optical trap or magnetic trap. Small particles can also be suspended with optical tweezers, using a highly focused laser beam. In 2011, CERN scientists were able to preserve antihydrogen for approximately 17 minutes. The record for storing antiparticles is currently held by the TRAP experiment at CERN: antiprotons were kept in a Penning trap for 405 days. A proposal was made in 2018, to develop containment technology advanced enough to contain a billion anti-protons in a portable device to be driven to another lab for further experimentation. Cost Scientists claim that antimatter is the costliest material to make. In 2006, Gerald Smith estimated $250 million could produce 10 milligrams of positrons (equivalent to $25 billion per gram); in 1999, NASA gave a figure of $62.5 trillion per gram of antihydrogen. This is because production is difficult (only very few antiprotons are produced in reactions in particle accelerators) and because there is higher demand for other uses of particle accelerators. According to CERN, it has cost a few hundred million Swiss francs to produce about 1 billionth of a gram (the amount used so far for particle/antiparticle collisions). In comparison, to produce the first atomic weapon, the cost of the Manhattan Project was estimated at $23 billion with inflation during 2007. Several studies funded by the NASA Institute for Advanced Concepts are exploring whether it might be possible to use magnetic scoops to collect the antimatter that occurs naturally in the Van Allen belt of the Earth, and ultimately, the belts of gas giants, like Jupiter, hopefully at a lower cost per gram. Uses Medical Matter–antimatter reactions have practical applications in medical imaging, such as positron emission tomography (PET). In positive beta decay, a nuclide loses surplus positive charge by emitting a positron (in the same event, a proton becomes a neutron, and a neutrino is also emitted). Nuclides with surplus positive charge are easily made in a cyclotron and are widely generated for medical use. Antiprotons have also been shown within laboratory experiments to have the potential to treat certain cancers, in a similar method currently used for ion (proton) therapy. Fuel Isolated and stored antimatter could be used as a fuel for interplanetary or interstellar travel as part of an antimatter-catalyzed nuclear pulse propulsion or another antimatter rocket. Since the energy density of antimatter is higher than that of conventional fuels, an antimatter-fueled spacecraft would have a higher thrust-to-weight ratio than a conventional spacecraft. If matter–antimatter collisions resulted only in photon emission, the entire rest mass of the particles would be converted to kinetic energy. The energy per unit mass () is about 10 orders of magnitude greater than chemical energies, and about 3 orders of magnitude greater than the nuclear potential energy that can be liberated, today, using nuclear fission (about per fission reaction or ), and about 2 orders of magnitude greater than the best possible results expected from fusion (about for the proton–proton chain). The reaction of of antimatter with of matter would produce (180 petajoules) of energy (by the mass–energy equivalence formula, ), or the rough equivalent of 43 megatons of TNT – slightly less than the yield of the 27,000 kg Tsar Bomba, the largest thermonuclear weapon ever detonated. Not all of that energy can be utilized by any realistic propulsion technology because of the nature of the annihilation products. While electron–positron reactions result in gamma ray photons, these are difficult to direct and use for thrust. In reactions between protons and antiprotons, their energy is converted largely into relativistic neutral and charged pions. The neutral pions decay almost immediately (with a lifetime of 85 attoseconds) into high-energy photons, but the charged pions decay more slowly (with a lifetime of 26 nanoseconds) and can be deflected magnetically to produce thrust. Charged pions ultimately decay into a combination of neutrinos (carrying about 22% of the energy of the charged pions) and unstable charged muons (carrying about 78% of the charged pion energy), with the muons then decaying into a combination of electrons, positrons and neutrinos (cf. muon decay; the neutrinos from this decay carry about 2/3 of the energy of the muons, meaning that from the original charged pions, the total fraction of their energy converted to neutrinos by one route or another would be about ). Weapons Antimatter has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it will ever be feasible. Nonetheless, the U.S. Air Force funded studies of the physics of antimatter in the Cold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. See also References Further reading External links Freeview Video 'Antimatter' by the Vega Science Trust and the BBC/OU CERN Webcasts (RealPlayer required) What is Antimatter? (from the Frequently Asked Questions at the Center for Antimatter–Matter Studies) FAQ from CERN with information about antimatter aimed at the general reader, posted in response to antimatter's fictional portrayal in Angels & Demons Antimatter at Angels and Demons, CERN What is direct CP-violation? Animated illustration of antihydrogen production at CERN from the Exploratorium. Particle physics Quantum field theory Fictional power sources Articles containing video clips

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1327

https://en.wikipedia.org/wiki/Antiparticle

Antiparticle

In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the antielectron (which is often referred to as positron). While the electron has a negative electric charge, the positron has a positive electric charge, and is produced naturally in certain types of radioactive decay. The opposite is also true: the antiparticle of the positron is the electron. Some particles, such as the photon, are their own antiparticle. Otherwise, for each pair of antiparticle partners, one is designated as the normal particle (the one that occurs in matter usually interacted with in daily life). The other (usually given the prefix "anti-") is designated the antiparticle. Particle–antiparticle pairs can annihilate each other, producing photons; since the charges of the particle and antiparticle are opposite, total charge is conserved. For example, the positrons produced in natural radioactive decay quickly annihilate themselves with electrons, producing pairs of gamma rays, a process exploited in positron emission tomography. The laws of nature are very nearly symmetrical with respect to particles and antiparticles. For example, an antiproton and a positron can form an antihydrogen atom, which is believed to have the same properties as a hydrogen atom. This leads to the question of why the formation of matter after the Big Bang resulted in a universe consisting almost entirely of matter, rather than being a half-and-half mixture of matter and antimatter. The discovery of charge parity violation helped to shed light on this problem by showing that this symmetry, originally thought to be perfect, was only approximate. Because charge is conserved, it is not possible to create an antiparticle without either destroying another particle of the same charge (as is for instance the case when antiparticles are produced naturally via beta decay or the collision of cosmic rays with Earth's atmosphere), or by the simultaneous creation of both a particle and its antiparticle, which can occur in particle accelerators such as the Large Hadron Collider at CERN. Although particles and their antiparticles have opposite charges, electrically neutral particles need not be identical to their antiparticles. The neutron, for example, is made out of quarks, the antineutron from antiquarks, and they are distinguishable from one another because neutrons and antineutrons annihilate each other upon contact. However, other neutral particles are their own antiparticles, such as photons, Z0 bosons,  mesons, and hypothetical gravitons and some hypothetical WIMPs. History Experiment In 1932, soon after the prediction of positrons by Paul Dirac, Carl D. Anderson found that cosmic-ray collisions produced these particles in a cloud chamber— a particle detector in which moving electrons (or positrons) leave behind trails as they move through the gas. The electric charge-to-mass ratio of a particle can be measured by observing the radius of curling of its cloud-chamber track in a magnetic field. Positrons, because of the direction that their paths curled, were at first mistaken for electrons travelling in the opposite direction. Positron paths in a cloud-chamber trace the same helical path as an electron but rotate in the opposite direction with respect to the magnetic field direction due to their having the same magnitude of charge-to-mass ratio but with opposite charge and, therefore, opposite signed charge-to-mass ratios. The antiproton and antineutron were found by Emilio Segrè and Owen Chamberlain in 1955 at the University of California, Berkeley. Since then, the antiparticles of many other subatomic particles have been created in particle accelerator experiments. In recent years, complete atoms of antimatter have been assembled out of antiprotons and positrons, collected in electromagnetic traps. Dirac hole theory Solutions of the Dirac equation contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many negative energy states available. To prevent this unphysical situation from happening, Dirac proposed that a "sea" of negative-energy electrons fills the universe, already occupying all of the lower-energy states so that, due to the Pauli exclusion principle, no other electron could fall into them. Sometimes, however, one of these negative-energy particles could be lifted out of this Dirac sea to become a positive-energy particle. But, when lifted out, it would leave behind a hole in the sea that would act exactly like a positive-energy electron with a reversed charge. These holes were interpreted as "negative-energy electrons" by Paul Dirac and mistakenly identified with protons in his 1930 paper A Theory of Electrons and Protons However, these "negative-energy electrons" turned out to be positrons, and not protons. This picture implied an infinite negative charge for the universe—a problem of which Dirac was aware. Dirac tried to argue that we would perceive this as the normal state of zero charge. Another difficulty was the difference in masses of the electron and the proton. Dirac tried to argue that this was due to the electromagnetic interactions with the sea, until Hermann Weyl proved that hole theory was completely symmetric between negative and positive charges. Dirac also predicted a reaction  +  →  + , where an electron and a proton annihilate to give two photons. Robert Oppenheimer and Igor Tamm, however, proved that this would cause ordinary matter to disappear too fast. A year later, in 1931, Dirac modified his theory and postulated the positron, a new particle of the same mass as the electron. The discovery of this particle the next year removed the last two objections to his theory. Within Dirac's theory, the problem of infinite charge of the universe remains. Some bosons also have antiparticles, but since bosons do not obey the Pauli exclusion principle (only fermions do), hole theory does not work for them. A unified interpretation of antiparticles is now available in quantum field theory, which solves both these problems by describing antimatter as negative energy states of the same underlying matter field i.e. particles moving backwards in time. Particle–antiparticle annihilation If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles. Reactions such as  +  →  (the two-photon annihilation of an electron-positron pair) are an example. The single-photon annihilation of an electron-positron pair,  +  → , cannot occur in free space because it is impossible to conserve energy and momentum together in this process. However, in the Coulomb field of a nucleus the translational invariance is broken and single-photon annihilation may occur. The reverse reaction (in free space, without an atomic nucleus) is also impossible for this reason. In quantum field theory, this process is allowed only as an intermediate quantum state for times short enough that the violation of energy conservation can be accommodated by the uncertainty principle. This opens the way for virtual pair production or annihilation in which a one particle quantum state may fluctuate into a two particle state and back. These processes are important in the vacuum state and renormalization of a quantum field theory. It also opens the way for neutral particle mixing through processes such as the one pictured here, which is a complicated example of mass renormalization. Properties Quantum states of a particle and an antiparticle are interchanged by the combined application of charge conjugation , parity and time reversal . and are linear, unitary operators, is antilinear and antiunitary, . If denotes the quantum state of a particle with momentum and spin whose component in the z-direction is , then one has where denotes the charge conjugate state, that is, the antiparticle. In particular a massive particle and its antiparticle transform under the same irreducible representation of the Poincaré group which means the antiparticle has the same mass and the same spin. If , and can be defined separately on the particles and antiparticles, then where the proportionality sign indicates that there might be a phase on the right hand side. As anticommutes with the charges, , particle and antiparticle have opposite electric charges q and -q. Quantum field theory This section draws upon the ideas, language and notation of canonical quantization of a quantum field theory. One may try to quantize an electron field without mixing the annihilation and creation operators by writing where we use the symbol k to denote the quantum numbers p and σ of the previous section and the sign of the energy, E(k), and ak denotes the corresponding annihilation operators. Of course, since we are dealing with fermions, we have to have the operators satisfy canonical anti-commutation relations. However, if one now writes down the Hamiltonian then one sees immediately that the expectation value of H need not be positive. This is because E(k) can have any sign whatsoever, and the combination of creation and annihilation operators has expectation value 1 or 0. So one has to introduce the charge conjugate antiparticle field, with its own creation and annihilation operators satisfying the relations where k has the same p, and opposite σ and sign of the energy. Then one can rewrite the field in the form where the first sum is over positive energy states and the second over those of negative energy. The energy becomes where E0 is an infinite negative constant. The vacuum state is defined as the state with no particle or antiparticle, i.e., and . Then the energy of the vacuum is exactly E0. Since all energies are measured relative to the vacuum, H is positive definite. Analysis of the properties of ak and bk shows that one is the annihilation operator for particles and the other for antiparticles. This is the case of a fermion. This approach is due to Vladimir Fock, Wendell Furry and Robert Oppenheimer. If one quantizes a real scalar field, then one finds that there is only one kind of annihilation operator; therefore, real scalar fields describe neutral bosons. Since complex scalar fields admit two different kinds of annihilation operators, which are related by conjugation, such fields describe charged bosons. Feynman–Stueckelberg interpretation By considering the propagation of the negative energy modes of the electron field backward in time, Ernst Stueckelberg reached a pictorial understanding of the fact that the particle and antiparticle have equal mass m and spin J but opposite charges q. This allowed him to rewrite perturbation theory precisely in the form of diagrams. Richard Feynman later gave an independent systematic derivation of these diagrams from a particle formalism, and they are now called Feynman diagrams. Each line of a diagram represents a particle propagating either backward or forward in time. In Feynman diagrams, anti-particles are shown traveling backwards in time. This technique is the most widespread method of computing amplitudes in quantum field theory today. Since this picture was first developed by Stueckelberg, and acquired its modern form in Feynman's work, it is called the Feynman–Stueckelberg interpretation of antiparticles to honor both scientists. See also List of particles Gravitational interaction of antimatter Parity, charge conjugation and time reversal symmetry CP violations Quantum field theory Baryogenesis, baryon asymmetry and Leptogenesis One-electron universe Paul Dirac Notes References External links Antimatter

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1335

https://en.wikipedia.org/wiki/Associative%20property

Associative property

In mathematics, the associative property is a property of some binary operations, which means that rearranging the parentheses in an expression will not change the result. In propositional logic, associativity is a valid rule of replacement for expressions in logical proofs. Within an expression containing two or more occurrences in a row of the same associative operator, the order in which the operations are performed does not matter as long as the sequence of the operands is not changed. That is (after rewriting the expression with parentheses and in infix notation if necessary), rearranging the parentheses in such an expression will not change its value. Consider the following equations: Even though the parentheses were rearranged on each line, the values of the expressions were not altered. Since this holds true when performing addition and multiplication on any real numbers, it can be said that "addition and multiplication of real numbers are associative operations". Associativity is not the same as commutativity, which addresses whether the order of two operands affects the result. For example, the order does not matter in the multiplication of real numbers, that is, , so we say that the multiplication of real numbers is a commutative operation. However, operations such as function composition and matrix multiplication are associative, but (generally) not commutative. Associative operations are abundant in mathematics; in fact, many algebraic structures (such as semigroups and categories) explicitly require their binary operations to be associative. However, many important and interesting operations are non-associative; some examples include subtraction, exponentiation, and the vector cross product. In contrast to the theoretical properties of real numbers, the addition of floating point numbers in computer science is not associative, and the choice of how to associate an expression can have a significant effect on rounding error. Definition Formally, a binary operation ∗ on a set S is called associative if it satisfies the associative law: (x ∗ y) ∗ z = x ∗ (y ∗ z) for all x, y, z in S. Here, ∗ is used to replace the symbol of the operation, which may be any symbol, and even the absence of symbol (juxtaposition) as for multiplication. (xy)z = x(yz) = xyz for all x, y, z in S. The associative law can also be expressed in functional notation thus: . Generalized associative law If a binary operation is associative, repeated application of the operation produces the same result regardless of how valid pairs of parentheses are inserted in the expression. This is called the generalized associative law. For instance, a product of four elements may be written, without changing the order of the factors, in five possible ways: If the product operation is associative, the generalized associative law says that all these formulas will yield the same result. So unless the formula with omitted parentheses already has a different meaning (see below), the parentheses can be considered unnecessary and "the" product can be written unambiguously as As the number of elements increases, the number of possible ways to insert parentheses grows quickly, but they remain unnecessary for disambiguation. An example where this does not work is the logical biconditional . It is associative, thus A(BC) is equivalent to (AB)C, but ABC most commonly means (AB and BC), which is not equivalent. Examples Some examples of associative operations include the following. The concatenation of the three strings "hello", " ", "world" can be computed by concatenating the first two strings (giving "hello ") and appending the third string ("world"), or by joining the second and third string (giving " world") and concatenating the first string ("hello") with the result. The two methods produce the same result; string concatenation is associative (but not commutative). In arithmetic, addition and multiplication of real numbers are associative; i.e., Because of associativity, the grouping parentheses can be omitted without ambiguity. The trivial operation (that is, the result is the first argument, no matter what the second argument is) is associative but not commutative. Likewise, the trivial operation (that is, the result is the second argument, no matter what the first argument is) is associative but not commutative. Addition and multiplication of complex numbers and quaternions are associative. Addition of octonions is also associative, but multiplication of octonions is non-associative. The greatest common divisor and least common multiple functions act associatively. Taking the intersection or the union of sets: If M is some set and S denotes the set of all functions from M to M, then the operation of function composition on S is associative: Slightly more generally, given four sets M, N, P and Q, with h: M to N, g: N to P, and f: P to Q, then as before. In short, composition of maps is always associative. Consider a set with three elements, A, B, and C. The following operation: {| class="wikitable" style="text-align:center" |- ! × !! A !! B !! C |- ! A | A || A || A |- ! B | A || B || C |- ! C | A || A || A |} is associative. Thus, for example, A(BC)=(AB)C = A. This operation is not commutative. Because matrices represent linear functions, and matrix multiplication represents function composition, one can immediately conclude that matrix multiplication is associative. Propositional logic Rule of replacement In standard truth-functional propositional logic, association, or associativity are two valid rules of replacement. The rules allow one to move parentheses in logical expressions in logical proofs. The rules (using logical connectives notation) are: and where "" is a metalogical symbol representing "can be replaced in a proof with". Truth functional connectives Associativity is a property of some logical connectives of truth-functional propositional logic. The following logical equivalences demonstrate that associativity is a property of particular connectives. The following are truth-functional tautologies. Associativity of disjunction: Associativity of conjunction: Associativity of equivalence: Joint denial is an example of a truth functional connective that is not associative. Non-associative operation A binary operation on a set S that does not satisfy the associative law is called non-associative. Symbolically, For such an operation the order of evaluation does matter. For example: Subtraction Division Exponentiation Vector cross product Also although addition is associative for finite sums, it is not associative inside infinite sums (series). For example, whereas Some non-associative operations are fundamental in mathematics. They appear often as the multiplication in structures called non-associative algebras, which have also an addition and a scalar multiplication. Examples are the octonions and Lie algebras. In Lie algebras, the multiplication satisfies Jacobi identity instead of the associative law; this allows abstracting the algebraic nature of infinitesimal transformations. Other examples are quasigroup, quasifield, non-associative ring, and commutative non-associative magmas. Nonassociativity of floating point calculation In mathematics, addition and multiplication of real numbers is associative. By contrast, in computer science, the addition and multiplication of floating point numbers is not associative, as rounding errors are introduced when dissimilar-sized values are joined together. To illustrate this, consider a floating point representation with a 4-bit mantissa: (1.0002×20 + 1.0002×20) + 1.0002×24 = 1.0002×2 + 1.0002×24 = 1.002×24 1.0002×20 + (1.0002×20 + 1.0002×24) = 1.0002×2 + 1.0002×24 = 1.002×24 Even though most computers compute with a 24 or 53 bits of mantissa, this is an important source of rounding error, and approaches such as the Kahan summation algorithm are ways to minimise the errors. It can be especially problematic in parallel computing. Notation for non-associative operations In general, parentheses must be used to indicate the order of evaluation if a non-associative operation appears more than once in an expression (unless the notation specifies the order in another way, like ). However, mathematicians agree on a particular order of evaluation for several common non-associative operations. This is simply a notational convention to avoid parentheses. A left-associative operation is a non-associative operation that is conventionally evaluated from left to right, i.e., while a right-associative operation is conventionally evaluated from right to left: Both left-associative and right-associative operations occur. Left-associative operations include the following: Subtraction and division of real numbers: Function application: This notation can be motivated by the currying isomorphism. Right-associative operations include the following: Exponentiation of real numbers in superscript notation: Exponentiation is commonly used with brackets or right-associatively because a repeated left-associative exponentiation operation is of little use. Repeated powers would mostly be rewritten with multiplication: Formatted correctly, the superscript inherently behaves as a set of parentheses; e.g. in the expression the addition is performed before the exponentiation despite there being no explicit parentheses wrapped around it. Thus given an expression such as , the full exponent of the base is evaluated first. However, in some contexts, especially in handwriting, the difference between , and can be hard to see. In such a case, right-associativity is usually implied. Function definition Using right-associative notation for these operations can be motivated by the Curry–Howard correspondence and by the currying isomorphism. Non-associative operations for which no conventional evaluation order is defined include the following. Exponentiation of real numbers in infix notation: Knuth's up-arrow operators: Taking the cross product of three vectors: Taking the pairwise average of real numbers: Taking the relative complement of sets is not the same as . (Compare material nonimplication in logic.) History William Rowan Hamilton seems to have coined the term "associative property" around 1844, a time when he was contemplating the non-associative algebra of the Octonions he had learned about from John T. Graves See also Light's associativity test Telescoping series, the use of addition associativity for cancelling terms in an infinite series A semigroup is a set with an associative binary operation. Commutativity and distributivity are two other frequently discussed properties of binary operations. Power associativity, alternativity, flexibility and N-ary associativity are weak forms of associativity. Moufang identities also provide a weak form of associativity. References Properties of binary operations Elementary algebra Functional analysis Rules of inference

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1344

https://en.wikipedia.org/wiki/Apple%20I

Apple I

The Apple Computer 1, originally released as the Apple Computer and known later as the Apple I, or Apple-1, is a desktop computer released by the Apple Computer Company (now Apple Inc.) in 1976. It was designed by Steve Wozniak. The idea of selling the computer came from Wozniak's friend and co-founder Steve Jobs. The Apple I was Apple's first product, and to finance its creation, Jobs sold his only motorized means of transportation, a VW Microbus, for a few hundred dollars (Wozniak later said that Jobs planned instead to use his bicycle to get around), and Wozniak sold his HP-65 calculator for $500. Wozniak demonstrated the first prototype in July 1976 at the Homebrew Computer Club in Palo Alto, California. Production was discontinued on September 30, 1977, after the June 10, 1977 introduction of its successor, the Apple II, which Byte magazine referred to as part of the "1977 Trinity" of personal computing (along with the PET 2001 from Commodore Business Machines and the TRS-80 Model I from Tandy Corporation). History On March 5, 1975, Steve Wozniak attended the first meeting of the Homebrew Computer Club in Gordon French's garage. He was so inspired that he immediately set to work on what would eventually become the Apple I computer. After building it for himself and showing it at the club, he and Steve Jobs gave out schematics (technical designs) for the computer to interested club members and even helped some of them build and test out copies. Then, Steve Jobs suggested that they design and sell a single etched and silkscreened circuit board—just the bare board, with no electronic parts—that people could use to build the computers. Wozniak calculated that having the board design laid out would cost $1,000 and manufacturing would cost another $20 per board; he hoped to recoup his costs if 50 people bought the boards for $40 each. To fund this small venture—their first company—Jobs sold his van and Wozniak sold his HP-65 calculator. Very soon after, Steve Jobs arranged to sell "something like 50" completely-built computers to the Byte Shop (a computer store in Mountain View, California) at $500 each. To fulfill the $25,000 order, they obtained $20,000 in parts at 30 days net and delivered the finished product in 10 days. The Apple I went on sale in July 1976 at a price of , because Wozniak "liked repeating digits" and because of a one-third markup on the $500 wholesale price. The first unit produced was used in a high school math class, and donated to Liza Loop's public-access computer center. About 200 units were produced, and all but 25 were sold within nine or ten months. In April 1977, the price was dropped to $475. It continued to be sold through August 1977, despite the introduction of the Apple II in April 1977, which began shipping in June of that year. In October 1977, the Apple I was officially discontinued and removed from Apple's price list. As Wozniak was the only person who could answer most customer support questions about the computer, the company offered Apple I owners discounts and trade-ins for Apple IIs to persuade them to return their computers. These recovered boards were then destroyed by Apple, contributing to their rarity today. Overview Wozniak's design originally used a Motorola 6800 processor, which cost $175, but when MOS Technology introduced the much cheaper 6502 microprocessor ($25) he switched. The Apple I CPU ran at 1.022,727 MHz, a fraction (2⁄7) of the NTSC color carrier which simplified video circuitry. Memory used the new 4K bit DRAM chips, and was 4K Bytes, expandable to 8KB on board, or 64KB externally The board was designed to use the next generation of 16K bit memory chips when they became available. An optional $75 plug-in cassette interface card allowed users to store programs on ordinary audio cassette tapes. A BASIC interpreter, originally written by Wozniak, was provided that let users easily write programs and play simple games. An onboard AC power supply was included. The Apple I's built-in computer terminal circuitry was distinctive. All one needed was a keyboard and a television set. The Apple 1 did not come with a case. It was either used as-is or some chose to build custom (mostly wooden) cases. Competing machines such as the Altair 8800 generally were programmed with front-mounted toggle switches and used indicator lights (red LEDs, most commonly) for output, and had to be extended with separate hardware to allow connection to a computer terminal or a teletypewriter machine. This made the Apple I an innovative machine for its day. Collectors' item As of February 2022, 62 Apple-1 computers have been confirmed to exist and according to not verified information 20 more a likely exist. 41 1st batch, 39 2nd batch and 2 unknown versions. Most are now in working condition. An Apple I reportedly sold for US$50,000 at auction in 1999. In 2008, the website Vintage Computing and Gaming reported that Apple I owner Rick Conte was looking to sell his unit and was "expecting a price in excess of $15,000 U.S." The site later reported Conte had donated the unit to the Maine Personal Computer Museum in 2009. A unit was sold in September 2009 for $17,480 on eBay. A unit belonging to early Apple Computer engineers Dick and Cliff Huston was sold on March 23, 2010, for $42,766 on eBay. In November 2010, an Apple I sold for £133,250 ($210,000) at Christie's auction house in London. The high price was likely due to the rare documents and packaging offered in the sale in addition to the computer, including the original packaging (with the return label showing Steve Jobs' parents' address, the original Apple Computer Inc "headquarters" being their garage), a personally typed and signed letter from Jobs (answering technical questions about the computer), and the original invoice showing "Steven" as the salesman. The computer was brought to Polytechnic University of Turin where it was fixed and used to run the BASIC programming language. On June 15, 2012, a working Apple I was sold at auction by Sotheby's for a then-record $374,500, more than double the expected price. This unit is on display at the Nexon Computer Museum in Jeju City, South Korea. In October 2012, a non-working Apple I from the estate of former Apple Computer employee Joe Copson was put up for auction by Christie's, but found no bidder who was willing to pay the starting price of US$80,000 (£50,000). Copson's board had previously been listed on eBay in December 2011, with a starting bid of $170,000 and failed to sell. Following the Christie's auction, the board was restored to working condition by computer historian Corey Cohen. Copson's Apple I was once again listed on eBay, where it sold for US$236,100.03 on April 23, 2015. On November 24, 2012, a working Apple I was sold at auction by Auction Team Breker for €400,000 (US$515,000). On May 25, 2013, a functioning 1976 model was sold for a then-record €516,000 (US$668,000) in Cologne. Auction Team Breker said "an unnamed Asian client" bought the Apple I. This particular unit has Wozniak's signature. An old business transaction letter from Jobs also was included, as well as the original owner's manual. On June 24, 2013, an Apple I was listed by Christie's as part of a special online-only auction lot called "First Bytes: Iconic Technology From the Twentieth Century." Bidding ran through July 9, 2013. The unit sold for $390,000. In November 2013, a working unit speculated to have been part of the original lot of 50 boards delivered to the Byte Shop was listed by Auction Team Breker for €180,000 ($242,820), but failed to sell during the auction. Immediately following the close of bidding, a private collector purchased it for €246,000 ($330,000). This board was marked "01-0046," matching the numbering placed on other units sold to the Byte Shop and included the original operation manuals, software cassettes, and shipping box autographed by Steve Wozniak. The board also bears Wozniak's signature. In October 2014, a working, early Apple I was sold at auction for $905,000 to the Henry Ford Museum in Dearborn, Michigan. The sale included the keyboard, monitor, cassette decks and a manual. The auction was run by Bonhams. On December 13, 2014, a fully functioning, early Apple I was sold at auction for $365,000 by auction house Christie's. The sale included a keyboard, custom case, original manual and a check labeled "Purchased July 1976 from Steve Jobs in his parents' garage in Los Altos". On May 30, 2015, a woman reportedly dropped off boxes of electronics for disposal at an electronics recycling center in the Silicon Valley of Northern California. Included in the items removed from her garage after the death of her husband was an original Apple I computer, which the recycling firm sold for $200,000 to a private collector. It is the company's practice to give back 50% of the proceeds to the original owner when an item is sold, so they want to find the mystery donor. On September 21, 2015, an Apple I bearing the Byte Shop number 01-0059 was listed by Bonhams Auctions as part of their "History of Science and Technology" auction with a starting bid of US$300,000. The machine was described as, "in near perfect condition." The owner, Tom Romkey, "...only used the Apple-1 once or twice, and ...set it on a shelf, and did not touch it again." The machine did not sell. However, Glenn and Shannon Dellimore, the co-founders of GLAMGLOW, a beauty company which they sold to Estee Lauder Companies, bought it after the auction through Bonhams Auction house. On the 40th Anniversary of Apple Computers 2016 the Dellimore's working Apple-1 went on loan and on display in 'Artifact' at the V&A Museum in London, England. On August 26, 2016, (the 40th Anniversary year of Apple Computers), the rarest Apple-1 in existence, an Apple-I prototype made and hand-built by Steve Jobs himself (according to Apple-1 expert Corey Cohen) and dubbed the 'Holy Grail' of computers was sold for $815,000 to winning bidders Glenn and Shannon Dellimore, the co-founders of cosmetics firm Glamglow, in an auction by Charitybuzz. The for-profit internet company that raises funds for nonprofit organizations declared that ten percent of the proceeds will go to the Leukemia and Lymphoma Society, based in New York. On April 15, 2017, an Apple I removed from Steve Jobs's office by Apple quality control engineer Don Hutmacher was placed on display at Living Computers: Museum + Labs. This Apple I was modified by Dan Kottke and Bill Fernandez. This previously unknown unit was purchased from Hutmacher's heirs for an undisclosed amount. On September 25, 2018, a functioning Apple I was purchased at a Dallas auction for $375,000 by an anonymous buyer. On May 23, 2019, an Apple I was purchased through Christie's auction house in London for £371,000. This Apple I is uniquely built into the bottom half of a briefcase and the lot included a modified cassette interface card, Panasonic RQ-309DS cassette tape recorder, SWTPC PR-40 alphanumeric printer, Sanyo VM4209 monitor and Motorola M6800 microprocessor. On March 12, 2020, a fully-functional Apple I was purchased at a Boston auction for $458,711. The lot included the original board with a Synertek CPU, Apple Cassette Interface, display case, keyboard kit, power supply, monitor and manuals. On November 9, 2021, one sold with user manuals and Apple software on two cassette tapes for $500,000 (many wrote 400,000 and forgot the premium), originally purchased by a college professor then sold to his student for $650. Serial numbers Both Steve Jobs and Steve Wozniak have stated that Apple did not assign serial numbers to the Apple l. Several boards have been found with numbered stickers affixed to them, which appear to be inspection stickers from the PCB manufacturer/assembler. A batch of boards is known to have numbers hand-written in black permanent marker on the back; these usually appear as "01-00##". Until January 2022, it was unknown who wrote the serial number on Apple of the 1st batch. As of January 2022, 29 Apple-1s with a serial number are known. The highest known number is . Neither the Apple company founders, nor Paul Terrell (founder of the Byte Shop), nor various Byte Shop employees remembered the originator. These numbers are sometimes incorrectly referred to as ‘Byte Shop numbers’. That was just a theory, which is now disproved. After several years of research and collecting type specimens, Achim Baqué (the curator of the Apple-1 Registry), had two original Apple-1s subjected to forensic analysis by PSA Los Angeles. The results were conclusive for both Apple-1s. It is the handwriting of Steve Jobs. The story was published on (February 10, 2022) during a Zoom meeting on the occasion of the World Computer Day. The story and ‘Letter of Authenticity’ were published same day. Museums displaying an original Apple 1 Computer United States American Computer & Robotics Museum in Bozeman, Montana Computer History Museum in Mountain View, California Computer Museum of America in Roswell, Georgia Smithsonian Museum of American History in Washington, DC Living Computers: Museum + Labs in Seattle, Washington System Source Computer Museum in Hunt Valley, Maryland Australia Powerhouse Museum in Sydney, New South Wales Germany Heinz Nixdorf MuseumsForum in Paderborn (working condition) Deutsches Museum in Munich (working condition) United Kingdom Science Museum, London in London, United Kingdom South Korea Nexon Computer Museum in Jeju Island, South Korea Switzerland ENTER Computer Museum in Solothurn, Switzerland Clones and replicas Several Apple I clones and replicas have been released in recent years. These are all created by hobbyists and marketed to the hobbyist/collector community. Availability is usually limited to small runs in response to demand. Replica 1: Created by Vince Briel. A software-compatible clone, produced using modern components, released in 2003 at a price of around $150. PE6502: Created by Jason Putnam. A single board computer kit made with all through-hole and current production components. Runs Apple 1 "Integer BASIC", a clone of AppleSoft BASIC (floating point capable), Wozmon and Krusader- all built-in ROM. 32k of RAM, and a Parallax Propeller terminal. Software compatible with the Apple 1. A-One: Created by Frank Achatz, also using modern components. RC6502 Apple I Replica, which uses a modern or period CPU and MC6821 PIA, and usually modern RAM and ROM. The system is modular, with multiple boards plugging into a backplane, but a single-board version (using an Arduino Nano to replace the keyboard and video hardware with a serial interface) is also available. Obtronix Apple I reproduction: Created by Steve Gabaly, using original components or equivalents thereof. Sold through eBay. Mimeo 1: Created by Mike Willegal. A hardware kit designed to replicate a real Apple I as accurately possible. Buyers are expected to assemble the kits themselves. Newton 1: Created by Michael Ng and released in 2012. Similar to the Mimeo 1, but is made using the same materials and same obsolete processing technique commonly used in the 1970s. Over 400 bare boards, kits and assembled boards were sold. There are Newton NTI and non-NTI versions available. Brain Board, a plug-in firmware board for the Apple II that, with the optional "Wozanium Pack" program, can emulate a functional Apple-1. Replica by MDesk. An accurate PCB copy of original Apple 1 was researched in 2012–2014. A few PCBs without components were sold for $26 in 2014. SmartyKit 1 computer kit: created by Sergey Panarin with package design by Greg Chemeris and released in 2019. A hardware kit on breadboards designed to replicate a real Apple I with modern components (ROM, RAM, Arduino controllers for video and keyboard) and real 6502 CPU. Made to teach anyone how to build a computer and how it works. Was presented at CES 2020 in Las Vegas and then featured in Apple Insider, WIRED, Tom's Hardware. Emulation Apple 1js, a web-based Apple I emulator written in JavaScript. MESS, a multi-system emulator able to emulate the Apple I. OpenEmulator, an accurate emulator of the Apple I, the ACI (Apple Cassette Interface) and CFFA1 expansion card. Pom1, an open source Apple I emulator for Microsoft Windows, Arch Linux and Android devices. Apple 1 Emulator, an emulator for the SAM Coupé home computer. CocoaPom, a Java-based emulator with a Cocoa front-end for Macintosh. Sim6502, an Apple I emulator for Macintosh. Green Delicious Apple-1, an emulator for the Commodore 64. See also Computer museums History of computer science History of computing References Citations Sources Price, Rob (1987). So Far: The First Ten Years of a Vision. Cupertino, Calif.: Apple Computer. . Owad, Tom (2005). Apple I Replica Creation: Back to the Garage. Rockland, Mass.: Syngress Publishing. . External links Apple I Computer specifications Bugbook Computer Museum blog. Apple 1 display. Apple I Owners Club Apple I Operational Manual German making-of article to recreate the Apple I Operational Manual Apple I project on www.sbprojects.com Apple 1 Computer Registry Macintosh Prehistory: The Apple I John Calande III blog – Building the Apple I clone, including corrections on the early history of Apple Computer Apple 1 | Cameron's Closet – includes display of the Apple 1's character set on real hardware, compared to on most emulators Computer-related introductions in 1976 Apple II family Apple Inc. hardware Early microcomputers 6502-based home computers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1349

https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer

Atanasoff–Berry computer

The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. Limited by the technology of the day, and execution, the device has remained somewhat obscure. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the first electronic ALU (arithmetic logic unit) which is integrated into every modern processor's design. Its unique contribution was to make computing faster by being the first to use vacuum tubes to do the arithmetic calculations. Prior to this, slower electro-mechanical methods were used by the Harvard Mark I and Konrad Zuse's machines. The first electronic, programmable, digital machine, the Colossus computer from 1943 to 1945, used similar tube-based technology as ABC. Overview Conceived in 1937, the machine was built by Iowa State College mathematics and physics professor John Vincent Atanasoff with the help of graduate student Clifford Berry. It was designed only to solve systems of linear equations and was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was not perfected, and when John Vincent Atanasoff left Iowa State College for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. The computer was designated an IEEE Milestone in 1990. Atanasoff and Berry's computer work was not widely known until it was rediscovered in the 1960s, amidst patent disputes over the first instance of an electronic computer. At that time ENIAC, that had been created by John Mauchly and J. Presper Eckert, was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff. When, in the mid-1970s, the secrecy surrounding the British World War II development of the Colossus computers that pre-dated ENIAC, was lifted and Colossus was described at a conference in Los Alamos, New Mexico, in June 1976, John Mauchly and Konrad Zuse were reported to have been astonished. Design and construction According to Atanasoff's account, several key principles of the Atanasoff–Berry computer were conceived in a sudden insight after a long nighttime drive to Rock Island, Illinois, during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing, regenerative capacitor memory, and a separation of memory and computing functions. The mechanical and logic design was worked out by Atanasoff over the next year. A grant application to build a proof of concept prototype was submitted in March 1939 to the Agronomy department, which was also interested in speeding up computation for economic and research analysis. $5,000 of further funding () to complete the machine came from the nonprofit Research Corporation of New York City. The ABC was built by Atanasoff and Berry in the basement of the physics building at Iowa State College during 1939–1942. The initial funds were released in September, and the 11-tube prototype was first demonstrated in October 1939. A December demonstration prompted a grant for construction of the full-scale machine. The ABC was built and tested over the next two years. A January 15, 1941, story in the Des Moines Register announced the ABC as "an electrical computing machine" with more than 300 vacuum tubes that would "compute complicated algebraic equations" (but gave no precise technical description of the computer). The system weighed more than . It contained approximately of wire, 280 dual-triode vacuum tubes, 31 thyratrons, and was about the size of a desk. It was not programmable, which distinguishes it from more general machines of the same era, such as Konrad Zuse's 1941 Z3 and the Colossus computers of 1943–1945. Nor did it implement the stored-program architecture, first implemented in the Manchester Baby of 1948, required for fully general-purpose practical computing machines. The machine was, however, the first to implement three critical ideas that are still part of every modern computer: Using binary digits to represent all numbers and data. Performing all calculations using electronics rather than wheels, ratchets, or mechanical switches. Organizing a system in which computation and memory are separated. The memory of the Atanasoff–Berry computer was a system called regenerative capacitor memory, which consisted of a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and two spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second. Data was represented as 50-bit binary fixed-point numbers. The electronics of the memory and arithmetic units could store and operate on 60 such numbers at a time (3000 bits). The alternating current power-line frequency of 60 Hz was the primary clock rate for the lowest-level operations. The arithmetic logic functions were fully electronic, implemented with vacuum tubes. The family of logic gates ranged from inverters to two- and three-input gates. The input and output levels and operating voltages were compatible between the different gates. Each gate consisted of one inverting vacuum-tube amplifier, preceded by a resistor divider input network that defined the logical function. The control logic functions, which only needed to operate once per drum rotation and therefore did not require electronic speed, were electromechanical, implemented with relays. The ALU operated on only one bit of each number at a time; it kept the carry/borrow bit in a capacitor for use in the next AC cycle. Although the Atanasoff–Berry computer was an important step up from earlier calculating machines, it was not able to run entirely automatically through an entire problem. An operator was needed to operate the control switches to set up its functions, much like the electro-mechanical calculators and unit record equipment of the time. Selection of the operation to be performed, reading, writing, converting to or from binary to decimal, or reducing a set of equations was made by front-panel switches and, in some cases, jumpers. There were two forms of input and output: primary user input and output and an intermediate results output and input. The intermediate results storage allowed operation on problems too large to be handled entirely within the electronic memory. (The largest problem that could be solved without the use of the intermediate output and input was two simultaneous equations, a trivial problem.) Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50-bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these units, primarily attributed to lack of control of the sheets' material characteristics. In retrospect, a solution could have been to add a parity bit to each number as written. This problem was not solved by the time Atanasoff left the university for war-related work. Primary user input was decimal, via standard IBM 80-column punched cards, and output was decimal, via a front-panel display. Function The ABC was designed for a specific purpose the solution of systems of simultaneous linear equations. It could handle systems with up to 29 equations, a difficult problem for the time. Problems of this scale were becoming common in physics, the department in which John Atanasoff worked. The machine could be fed two linear equations with up to 29 variables and a constant term and eliminate one of the variables. This process would be repeated manually for each of the equations, which would result in a system of equations with one fewer variable. Then the whole process would be repeated to eliminate another variable. George W. Snedecor, the head of Iowa State's Statistics Department, was very likely the first user of an electronic digital computer to solve real-world mathematics problems. He submitted many of these problems to Atanasoff. Patent dispute On June 26, 1947, J. Presper Eckert and John Mauchly were the first to file for patent on a digital computing device (ENIAC), much to the surprise of Atanasoff. The ABC had been examined by John Mauchly in June 1941, and Isaac Auerbach, a former student of Mauchly's, alleged that it influenced his later work on ENIAC, although Mauchly denied this. The ENIAC patent did not issue until 1964, and by 1967 Honeywell sued Sperry Rand in an attempt to break the ENIAC patents, arguing that the ABC constituted prior art. The United States District Court for the District of Minnesota released its judgement on October 19, 1973, finding in Honeywell v. Sperry Rand that the ENIAC patent was a derivative of John Atanasoff's invention. Campbell-Kelly and Aspray conclude: The case was legally resolved on October 19, 1973, when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry computer. Judge Larson explicitly stated: Herman Goldstine, one of the original developers of ENIAC wrote: Replica The original ABC was eventually dismantled in 1948, when the university converted the basement to classrooms, and all of its pieces except for one memory drum were discarded. In 1997, a team of researchers led by Dr. Delwyn Bluhm and John Gustafson from Ames Laboratory (located on the Iowa State University campus) finished building a working replica of the Atanasoff–Berry computer at a cost of $350,000 (equivalent to $ in ). The replica ABC was on display in the first floor lobby of the Durham Center for Computation and Communication at Iowa State University and was subsequently exhibited at the Computer History Museum. See also History of computing hardware List of vacuum-tube computers Mikhail Kravchuk References Bibliography External links The Birth of the ABC Reconstruction of the ABC, 1994-1997 John Gustafson, Reconstruction of the Atanasoff-Berry Computer The ENIAC patent trial Honeywell v. Sperry Rand Records, 1846-1973, Charles Babbage Institute, University of Minnesota. The Atanasoff-Berry Computer In Operation (YouTube) 1940s computers One-of-a-kind computers Vacuum tube computers Computer-related introductions in 1942 History of computing hardware Iowa State University Serial computers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1363

https://en.wikipedia.org/wiki/Andr%C3%A9-Marie%20Amp%C3%A8re

André-Marie Ampère

André-Marie Ampère (, ; ; 20 January 177510 June 1836) was a French physicist, mathematician and lay catholic who was one of the founders of the science of classical electromagnetism, which he referred to as "electrodynamics". He is also the inventor of numerous applications, such as the solenoid (a term coined by him) and the electrical telegraph. As an autodidact, Ampère was a member of the French Academy of Sciences and professor at the École polytechnique and the Collège de France. The SI unit of measurement of electric current, the ampere, is named after him. His name is also one of the 72 names inscribed on the Eiffel Tower. Early life André-Marie Ampère was born on 20 January 1775 to Jean-Jacques Ampère, a prosperous businessman, and Jeanne Antoinette Desutières-Sarcey Ampère, during the height of the French Enlightenment. He spent his childhood and adolescence at the family property at Poleymieux-au-Mont-d'Or near Lyon. Jean-Jacques Ampère, a successful merchant, was an admirer of the philosophy of Jean-Jacques Rousseau, whose theories of education (as outlined in his treatise Émile) were the basis of Ampère's education. Rousseau believed that young boys should avoid formal schooling and pursue instead an "education direct from nature." Ampère's father actualized this ideal by allowing his son to educate himself within the walls of his well-stocked library. French Enlightenment masterpieces such as Georges-Louis Leclerc, comte de Buffon's Histoire naturelle, générale et particulière (begun in 1749) and Denis Diderot and Jean le Rond d'Alembert's Encyclopédie (volumes added between 1751 and 1772) thus became Ampère's schoolmasters. The young Ampère, however, soon resumed his Latin lessons, which enabled him to master the works of Leonhard Euler and Daniel Bernoulli. French Revolution In addition, Ampère used his access to the latest books to begin teaching himself advanced mathematics at age 12. In later life Ampère claimed that he knew as much about mathematics and science when he was eighteen as ever he knew, but as a polymath, his reading embraced history, travels, poetry, philosophy, and the natural sciences. His mother was a devout Catholic, so Ampère was also initiated into the Catholic faith along with Enlightenment science. The French Revolution (1789–99) that began during his youth was also influential: Ampère's father was called into public service by the new revolutionary government, becoming a justice of the peace in a small town near Lyon. When the Jacobin faction seized control of the Revolutionary government in 1792, his father Jean-Jacques Ampère resisted the new political tides, and he was guillotined on 24 November 1793, as part of the Jacobin purges of the period. In 1796, Ampère, met Julie Carron, and in 1799 they were married. Ampère took his first regular job in 1799 as a mathematics teacher, which gave him the financial security to marry Carron and father his first child, Jean-Jacques (named after his father), the next year. (Jean-Jacques Ampère eventually achieved his own fame as a scholar of languages.) Ampère's maturation corresponded with the transition to the Napoleonic regime in France, and the young father and teacher found new opportunities for success within the technocratic structures favoured by the new French First Consul. In 1802, Ampère was appointed a professor of physics and chemistry at the École Centrale in Bourg-en-Bresse, leaving his ailing wife and infant son Jean-Jacques Antoine Ampère in Lyon. He used his time in Bourg to research mathematics, producing Considérations sur la théorie mathématique de jeu (1802; "Considerations on the Mathematical Theory of Games"), a treatise on mathematical probability that he sent to the Paris Academy of Sciences in 1803. Teaching career After the death of his wife in July 1803, Ampère moved to Paris, where he began a tutoring post at the new École Polytechnique in 1804. Despite his lack of formal qualifications, Ampère was appointed a professor of mathematics at the school in 1809. As well as holding positions at this school until 1828, in 1819 and 1820 Ampère offered courses in philosophy and astronomy, respectively, at the University of Paris, and in 1824 he was elected to the prestigious chair in experimental physics at the Collège de France. In 1814, Ampère was invited to join the class of mathematicians in the new Institut Impérial, the umbrella under which the reformed state Academy of Sciences would sit. Ampère engaged in a diverse array of scientific inquiries during the years leading up to his election to the academy—writing papers and engaging in topics from mathematics and philosophy to chemistry and astronomy, which was customary among the leading scientific intellectuals of the day. Ampère claimed that "at eighteen years he found three culminating points in his life, his First Communion, the reading of Antoine Leonard Thomas's "Eulogy of Descartes", and the Taking of the Bastille. On the day of his wife's death he wrote two verses from the Psalms, and the prayer, 'O Lord, God of Mercy, unite me in Heaven with those whom you have permitted me to love on earth.' In times of duress he would take refuge in the reading of the Bible and the Fathers of the Church." For a time he took into his family the young student Frédéric Ozanam (1813–1853), one of the founders of the Conference of Charity, later known as the Society of Saint Vincent de Paul. Through Ampère, Ozanam had contact with leaders of the neo-Catholic movement, such as François-René de Chateaubriand, Jean-Baptiste Henri Lacordaire, and Charles Forbes René de Montalembert. Ozanam was beatified by Pope John Paul II in 1998. Work in electromagnetism In September 1820, Ampère's friend and eventual eulogist François Arago showed the members of the French Academy of Sciences the surprising discovery of Danish physicist Hans Christian Ørsted that a magnetic needle is deflected by an adjacent electric current. Ampère began developing a mathematical and physical theory to understand the relationship between electricity and magnetism. Furthering Ørsted's experimental work, Ampère showed that two parallel wires carrying electric currents attract or repel each other, depending on whether the currents flow in the same or opposite directions, respectively - this laid the foundation of electrodynamics. He also applied mathematics in generalizing physical laws from these experimental results. The most important of these was the principle that came to be called Ampère's law, which states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents. Ampère also applied this same principle to magnetism, showing the harmony between his law and French physicist Charles Augustin de Coulomb's law of electric action. Ampère's devotion to, and skill with, experimental techniques anchored his science within the emerging fields of experimental physics. Ampère also provided a physical understanding of the electromagnetic relationship, theorizing the existence of an "electrodynamic molecule" (the forerunner of the idea of the electron) that served as the component element of both electricity and magnetism. Using this physical explanation of electromagnetic motion, Ampère developed a physical account of electromagnetic phenomena that was both empirically demonstrable and mathematically predictive. In 1827, Ampère published his magnum opus, Mémoire sur la théorie mathématique des phénomènes électrodynamiques uniquement déduite de l’experience (Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience), the work that coined the name of his new science, electrodynamics, and became known ever after as its founding treatise. In 1827, Ampère was elected a Foreign Member of the Royal Society and in 1828, a foreign member of the Royal Swedish Academy of Science. Probably the highest recognition came from James Clerk Maxwell, who in his "Treatise on Electricity and Magnetism", named Ampère “the Newton of electricity”. Honours 8.10.1825: Member of the Royal Academy of Science, Letters and Fine Arts of Belgium. Legacy In recognition of his contribution to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of electrical measurement, along with the coulomb, volt, ohm, watt and farad, which are named, respectively, after Ampère's contemporaries Charles-Augustin de Coulomb of France, Alessandro Volta of Italy, Georg Ohm of Germany, James Watt of Scotland and Michael Faraday of England. Ampère's name is one of the 72 names inscribed on the Eiffel Tower. Several items are named after Ampère; many streets and squares, schools, a Lyon metro station, a graphics processing unit microarchitecture, a mountain on the moon and an electric ferry in Norway. Writings Considérations sur la théorie mathématique du jeu, Perisse, Lyon Paris 1802, online lesen im Internet-Archiv Partial translations: Magie, W.M. (1963). A Source Book in Physics. Harvard: Cambridge MA. pp. 446–460. . Complete translations: References Further reading (EPUB) External links Ampère and the history of electricity – a French-language, edited by CNRS, site with Ampère's correspondence (full text and critical edition with links to manuscripts pictures, more than 1000 letters), an Ampère bibliography, experiments, and 3D simulations Ampère Museum – a French-language site from the museum in Poleymieux-au-Mont-d'or, near Lyon, France "Société des Amis d'André-Marie Ampère", a French society dedicated to maintain the memory of André-Marie Ampère and in charge of the Ampère Museum. Catholic Encyclopedia on André Marie Ampère Electrical units history. 1775 births 1836 deaths Scientists from Lyon Electrostatics 19th-century French physicists People associated with electricity Independent scientists French Roman Catholics Collège de France faculty Foreign Members of the Royal Society Fellows of the Royal Society of Edinburgh Members of the French Academy of Sciences Members of the Royal Academy of Belgium Members of the Royal Swedish Academy of Sciences Honorary members of the Saint Petersburg Academy of Sciences Burials at Montmartre Cemetery Magneticians

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1368

https://en.wikipedia.org/wiki/Assembly%20language

Assembly language

In computer programming, assembly language (or assembler language), sometimes abbreviated asm, is any low-level programming language in which there is a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly language usually has one statement per machine instruction (1:1), but constants, comments, assembler directives, symbolic labels of, e.g., memory locations, registers, and macros are generally also supported. Assembly code is converted into executable machine code by a utility program referred to as an assembler. The term "assembler" is generally attributed to Wilkes, Wheeler and Gill in their 1951 book The Preparation of Programs for an Electronic Digital Computer, who, however, used the term to mean "a program that assembles another program consisting of several sections into a single program". The conversion process is referred to as assembly, as in assembling the source code. The computational step when an assembler is processing a program is called assembly time. Assembly language may also be called symbolic machine code. Because assembly depends on the machine code instructions, each assembly language is specific to a particular computer architecture. Sometimes there is more than one assembler for the same architecture, and sometimes an assembler is specific to an operating system or to particular operating systems. Most assembly languages do not provide specific syntax for operating system calls, and most assembly languages can be used universally with any operating system, as the language provides access to all the real capabilities of the processor, upon which all system call mechanisms ultimately rest. In contrast to assembly languages, most high-level programming languages are generally portable across multiple architectures but require interpreting or compiling, a much more complicated task than assembling. Assembly language syntax Assembly language uses a mnemonic to represent, e.g., each low-level machine instruction or opcode, each directive, typically also each architectural register, flag, etc. Some of the mnemonics may be built in and some user defined. Many operations require one or more operands in order to form a complete instruction. Most assemblers permit named constants, registers, and labels for program and memory locations, and can calculate expressions for operands. Thus, programmers are freed from tedious repetitive calculations and assembler programs are much more readable than machine code. Depending on the architecture, these elements may also be combined for specific instructions or addressing modes using offsets or other data as well as fixed addresses. Many assemblers offer additional mechanisms to facilitate program development, to control the assembly process, and to aid debugging. Some are column oriented, with specific fields in specific columns; this was very common for machines using punched cards in the 1950s and early 1960s. Some assemblers have free-form syntax, with fields separated by delimiters, e.g., punctuation, white space. Some assemblers are hybrid, with, e.g., labels, in a specific column and other fields separated by delimiters; this became more common than column oriented syntax in the 1960s. IBM System/360 All of the IBM assemblers for System/360, by default, have a label in column 1, fields separated by delimiters in columns 2-71, a continuation indicator in column 72 and a sequence number in columns 73-80. The delimiter for label, opcode, operands and comments is spaces, while individual operands are separated by commas and parentheses. Terminology A macro assembler is an assembler that includes a macroinstruction facility so that (parameterized) assembly language text can be represented by a name, and that name can be used to insert the expanded text into other code. Open code refers to any assembler input outside of a macro definition. A cross assembler (see also cross compiler) is an assembler that is run on a computer or operating system (the host system) of a different type from the system on which the resulting code is to run (the target system). Cross-assembling facilitates the development of programs for systems that do not have the resources to support software development, such as an embedded system or a microcontroller. In such a case, the resulting object code must be transferred to the target system, via read-only memory (ROM, EPROM, etc.), a programmer (when the read-only memory is integrated in the device, as in microcontrollers), or a data link using either an exact bit-by-bit copy of the object code or a text-based representation of that code (such as Intel hex or Motorola S-record). A high-level assembler is a program that provides language abstractions more often associated with high-level languages, such as advanced control structures (IF/THEN/ELSE, DO CASE, etc.) and high-level abstract data types, including structures/records, unions, classes, and sets. A microassembler is a program that helps prepare a microprogram, called firmware, to control the low level operation of a computer. A meta-assembler is "a program that accepts the syntactic and semantic description of an assembly language, and generates an assembler for that language", or that accepts an assembler source file along with such a description and assembles the source file in accordance with that description. "Meta-Symbol" assemblers for the SDS 9 Series and SDS Sigma series of computers are meta-assemblers. Sperry Univac also provided a Meta-Assembler for the UNIVAC 1100/2200 series. inline assembler (or embedded assembler) is assembler code contained within a high-level language program. This is most often used in systems programs which need direct access to the hardware. Key concepts Assembler An assembler program creates object code by translating combinations of mnemonics and syntax for operations and addressing modes into their numerical equivalents. This representation typically includes an operation code ("opcode") as well as other control bits and data. The assembler also calculates constant expressions and resolves symbolic names for memory locations and other entities. The use of symbolic references is a key feature of assemblers, saving tedious calculations and manual address updates after program modifications. Most assemblers also include macro facilities for performing textual substitution – e.g., to generate common short sequences of instructions as inline, instead of called subroutines. Some assemblers may also be able to perform some simple types of instruction set-specific optimizations. One concrete example of this may be the ubiquitous x86 assemblers from various vendors. Called jump-sizing, most of them are able to perform jump-instruction replacements (long jumps replaced by short or relative jumps) in any number of passes, on request. Others may even do simple rearrangement or insertion of instructions, such as some assemblers for RISC architectures that can help optimize a sensible instruction scheduling to exploit the CPU pipeline as efficiently as possible. Assemblers have been available since the 1950s, as the first step above machine language and before high-level programming languages such as Fortran, Algol, COBOL and Lisp. There have also been several classes of translators and semi-automatic code generators with properties similar to both assembly and high-level languages, with Speedcode as perhaps one of the better-known examples. There may be several assemblers with different syntax for a particular CPU or instruction set architecture. For instance, an instruction to add memory data to a register in a x86-family processor might be add eax,[ebx], in original Intel syntax, whereas this would be written addl (%ebx),%eax in the AT&T syntax used by the GNU Assembler. Despite different appearances, different syntactic forms generally generate the same numeric machine code. A single assembler may also have different modes in order to support variations in syntactic forms as well as their exact semantic interpretations (such as FASM-syntax, TASM-syntax, ideal mode, etc., in the special case of x86 assembly programming). Number of passes There are two types of assemblers based on how many passes through the source are needed (how many times the assembler reads the source) to produce the object file. One-pass assemblers go through the source code once. Any symbol used before it is defined will require "errata" at the end of the object code (or, at least, no earlier than the point where the symbol is defined) telling the linker or the loader to "go back" and overwrite a placeholder which had been left where the as yet undefined symbol was used. Multi-pass assemblers create a table with all symbols and their values in the first passes, then use the table in later passes to generate code. In both cases, the assembler must be able to determine the size of each instruction on the initial passes in order to calculate the addresses of subsequent symbols. This means that if the size of an operation referring to an operand defined later depends on the type or distance of the operand, the assembler will make a pessimistic estimate when first encountering the operation, and if necessary, pad it with one or more "no-operation" instructions in a later pass or the errata. In an assembler with peephole optimization, addresses may be recalculated between passes to allow replacing pessimistic code with code tailored to the exact distance from the target. The original reason for the use of one-pass assemblers was memory size and speed of assembly – often a second pass would require storing the symbol table in memory (to handle forward references), rewinding and rereading the program source on tape, or rereading a deck of cards or punched paper tape. Later computers with much larger memories (especially disc storage), had the space to perform all necessary processing without such re-reading. The advantage of the multi-pass assembler is that the absence of errata makes the linking process (or the program load if the assembler directly produces executable code) faster. Example: in the following code snippet, a one-pass assembler would be able to determine the address of the backward reference BKWD when assembling statement S2, but would not be able to determine the address of the forward reference FWD when assembling the branch statement S1; indeed, FWD may be undefined. A two-pass assembler would determine both addresses in pass 1, so they would be known when generating code in pass 2. B ... EQU * ... EQU * ... B High-level assemblers More sophisticated high-level assemblers provide language abstractions such as: High-level procedure/function declarations and invocations Advanced control structures (IF/THEN/ELSE, SWITCH) High-level abstract data types, including structures/records, unions, classes, and sets Sophisticated macro processing (although available on ordinary assemblers since the late 1950s for, e.g., the IBM 700 series and IBM 7000 series, and since the 1960s for IBM System/360 (S/360), amongst other machines) Object-oriented programming features such as classes, objects, abstraction, polymorphism, and inheritance See Language design below for more details. Assembly language A program written in assembly language consists of a series of mnemonic processor instructions and meta-statements (known variously as declarative operations, directives, pseudo-instructions, pseudo-operations and pseudo-ops), comments and data. Assembly language instructions usually consist of an opcode mnemonic followed by an operand, which might be a list of data, arguments or parameters. Some instructions may be "implied," which means the data upon which the instruction operates is implicitly defined by the instruction itself—such an instruction does not take an operand. The resulting statement is translated by an assembler into machine language instructions that can be loaded into memory and executed. For example, the instruction below tells an x86/IA-32 processor to move an immediate 8-bit value into a register. The binary code for this instruction is 10110 followed by a 3-bit identifier for which register to use. The identifier for the AL register is 000, so the following machine code loads the AL register with the data 01100001. 10110000 01100001 This binary computer code can be made more human-readable by expressing it in hexadecimal as follows. B0 61 Here, B0 means 'Move a copy of the following value into AL, and 61 is a hexadecimal representation of the value 01100001, which is 97 in decimal. Assembly language for the 8086 family provides the mnemonic MOV (an abbreviation of move) for instructions such as this, so the machine code above can be written as follows in assembly language, complete with an explanatory comment if required, after the semicolon. This is much easier to read and to remember. MOV AL, 61h ; Load AL with 97 decimal (61 hex) In some assembly languages (including this one) the same mnemonic, such as MOV, may be used for a family of related instructions for loading, copying and moving data, whether these are immediate values, values in registers, or memory locations pointed to by values in registers or by immediate (a.k.a direct) addresses. Other assemblers may use separate opcode mnemonics such as L for "move memory to register", ST for "move register to memory", LR for "move register to register", MVI for "move immediate operand to memory", etc. If the same mnemonic is used for different instructions, that means that the mnemonic corresponds to several different binary instruction codes, excluding data (e.g. the 61h in this example), depending on the operands that follow the mnemonic. For example, for the x86/IA-32 CPUs, the Intel assembly language syntax MOV AL, AH represents an instruction that moves the contents of register AH into register AL. The hexadecimal form of this instruction is: 88 E0 The first byte, 88h, identifies a move between a byte-sized register and either another register or memory, and the second byte, E0h, is encoded (with three bit-fields) to specify that both operands are registers, the source is AH, and the destination is AL. In a case like this where the same mnemonic can represent more than one binary instruction, the assembler determines which instruction to generate by examining the operands. In the first example, the operand 61h is a valid hexadecimal numeric constant and is not a valid register name, so only the B0 instruction can be applicable. In the second example, the operand AH is a valid register name and not a valid numeric constant (hexadecimal, decimal, octal, or binary), so only the 88 instruction can be applicable. Assembly languages are always designed so that this sort of unambiguousness is universally enforced by their syntax. For example, in the Intel x86 assembly language, a hexadecimal constant must start with a numeral digit, so that the hexadecimal number 'A' (equal to decimal ten) would be written as 0Ah or 0AH, not AH, specifically so that it cannot appear to be the name of register AH. (The same rule also prevents ambiguity with the names of registers BH, CH, and DH, as well as with any user-defined symbol that ends with the letter H and otherwise contains only characters that are hexadecimal digits, such as the word "BEACH".) Returning to the original example, while the x86 opcode 10110000 (B0) copies an 8-bit value into the AL register, 10110001 (B1) moves it into CL and 10110010 (B2) does so into DL. Assembly language examples for these follow. MOV AL, 1h ; Load AL with immediate value 1 MOV CL, 2h ; Load CL with immediate value 2 MOV DL, 3h ; Load DL with immediate value 3 The syntax of MOV can also be more complex as the following examples show. MOV EAX, [EBX] ; Move the 4 bytes in memory at the address contained in EBX into EAX MOV [ESI+EAX], CL ; Move the contents of CL into the byte at address ESI+EAX MOV DS, DX ; Move the contents of DX into segment register DS In each case, the MOV mnemonic is translated directly into one of the opcodes 88-8C, 8E, A0-A3, B0-BF, C6 or C7 by an assembler, and the programmer normally does not have to know or remember which. Transforming assembly language into machine code is the job of an assembler, and the reverse can at least partially be achieved by a disassembler. Unlike high-level languages, there is a one-to-one correspondence between many simple assembly statements and machine language instructions. However, in some cases, an assembler may provide pseudoinstructions (essentially macros) which expand into several machine language instructions to provide commonly needed functionality. For example, for a machine that lacks a "branch if greater or equal" instruction, an assembler may provide a pseudoinstruction that expands to the machine's "set if less than" and "branch if zero (on the result of the set instruction)". Most full-featured assemblers also provide a rich macro language (discussed below) which is used by vendors and programmers to generate more complex code and data sequences. Since the information about pseudoinstructions and macros defined in the assembler environment is not present in the object program, a disassembler cannot reconstruct the macro and pseudoinstruction invocations but can only disassemble the actual machine instructions that the assembler generated from those abstract assembly-language entities. Likewise, since comments in the assembly language source file are ignored by the assembler and have no effect on the object code it generates, a disassembler is always completely unable to recover source comments. Each computer architecture has its own machine language. Computers differ in the number and type of operations they support, in the different sizes and numbers of registers, and in the representations of data in storage. While most general-purpose computers are able to carry out essentially the same functionality, the ways they do so differ; the corresponding assembly languages reflect these differences. Multiple sets of mnemonics or assembly-language syntax may exist for a single instruction set, typically instantiated in different assembler programs. In these cases, the most popular one is usually that supplied by the CPU manufacturer and used in its documentation. Two examples of CPUs that have two different sets of mnemonics are the Intel 8080 family and the Intel 8086/8088. Because Intel claimed copyright on its assembly language mnemonics (on each page of their documentation published in the 1970s and early 1980s, at least), some companies that independently produced CPUs compatible with Intel instruction sets invented their own mnemonics. The Zilog Z80 CPU, an enhancement of the Intel 8080A, supports all the 8080A instructions plus many more; Zilog invented an entirely new assembly language, not only for the new instructions but also for all of the 8080A instructions. For example, where Intel uses the mnemonics MOV, MVI, LDA, STA, LXI, LDAX, STAX, LHLD, and SHLD for various data transfer instructions, the Z80 assembly language uses the mnemonic LD for all of them. A similar case is the NEC V20 and V30 CPUs, enhanced copies of the Intel 8086 and 8088, respectively. Like Zilog with the Z80, NEC invented new mnemonics for all of the 8086 and 8088 instructions, to avoid accusations of infringement of Intel's copyright. (It is questionable whether such copyrights can be valid, and later CPU companies such as AMD and Cyrix republished Intel's x86/IA-32 instruction mnemonics exactly with neither permission nor legal penalty.) It is doubtful whether in practice many people who programmed the V20 and V30 actually wrote in NEC's assembly language rather than Intel's; since any two assembly languages for the same instruction set architecture are isomorphic (somewhat like English and Pig Latin), there is no requirement to use a manufacturer's own published assembly language with that manufacturer's products. Language design Basic elements There is a large degree of diversity in the way the authors of assemblers categorize statements and in the nomenclature that they use. In particular, some describe anything other than a machine mnemonic or extended mnemonic as a pseudo-operation (pseudo-op). A typical assembly language consists of 3 types of instruction statements that are used to define program operations: Opcode mnemonics Data definitions Assembly directives Opcode mnemonics and extended mnemonics Instructions (statements) in assembly language are generally very simple, unlike those in high-level languages. Generally, a mnemonic is a symbolic name for a single executable machine language instruction (an opcode), and there is at least one opcode mnemonic defined for each machine language instruction. Each instruction typically consists of an operation or opcode plus zero or more operands. Most instructions refer to a single value or a pair of values. Operands can be immediate (value coded in the instruction itself), registers specified in the instruction or implied, or the addresses of data located elsewhere in storage. This is determined by the underlying processor architecture: the assembler merely reflects how this architecture works. Extended mnemonics are often used to specify a combination of an opcode with a specific operand, e.g., the System/360 assemblers use as an extended mnemonic for with a mask of 15 and ("NO OPeration" – do nothing for one step) for with a mask of 0. Extended mnemonics are often used to support specialized uses of instructions, often for purposes not obvious from the instruction name. For example, many CPU's do not have an explicit NOP instruction, but do have instructions that can be used for the purpose. In 8086 CPUs the instruction is used for , with being a pseudo-opcode to encode the instruction . Some disassemblers recognize this and will decode the instruction as . Similarly, IBM assemblers for System/360 and System/370 use the extended mnemonics and for and with zero masks. For the SPARC architecture, these are known as synthetic instructions. Some assemblers also support simple built-in macro-instructions that generate two or more machine instructions. For instance, with some Z80 assemblers the instruction is recognized to generate followed by . These are sometimes known as pseudo-opcodes. Mnemonics are arbitrary symbols; in 1985 the IEEE published Standard 694 for a uniform set of mnemonics to be used by all assemblers. The standard has since been withdrawn. Data directives There are instructions used to define data elements to hold data and variables. They define the type of data, the length and the alignment of data. These instructions can also define whether the data is available to outside programs (programs assembled separately) or only to the program in which the data section is defined. Some assemblers classify these as pseudo-ops. Assembly directives Assembly directives, also called pseudo-opcodes, pseudo-operations or pseudo-ops, are commands given to an assembler "directing it to perform operations other than assembling instructions". Directives affect how the assembler operates and "may affect the object code, the symbol table, the listing file, and the values of internal assembler parameters". Sometimes the term pseudo-opcode is reserved for directives that generate object code, such as those that generate data. The names of pseudo-ops often start with a dot to distinguish them from machine instructions. Pseudo-ops can make the assembly of the program dependent on parameters input by a programmer, so that one program can be assembled in different ways, perhaps for different applications. Or, a pseudo-op can be used to manipulate presentation of a program to make it easier to read and maintain. Another common use of pseudo-ops is to reserve storage areas for run-time data and optionally initialize their contents to known values. Symbolic assemblers let programmers associate arbitrary names (labels or symbols) with memory locations and various constants. Usually, every constant and variable is given a name so instructions can reference those locations by name, thus promoting self-documenting code. In executable code, the name of each subroutine is associated with its entry point, so any calls to a subroutine can use its name. Inside subroutines, GOTO destinations are given labels. Some assemblers support local symbols which are often lexically distinct from normal symbols (e.g., the use of "10$" as a GOTO destination). Some assemblers, such as NASM, provide flexible symbol management, letting programmers manage different namespaces, automatically calculate offsets within data structures, and assign labels that refer to literal values or the result of simple computations performed by the assembler. Labels can also be used to initialize constants and variables with relocatable addresses. Assembly languages, like most other computer languages, allow comments to be added to program source code that will be ignored during assembly. Judicious commenting is essential in assembly language programs, as the meaning and purpose of a sequence of binary machine instructions can be difficult to determine. The "raw" (uncommented) assembly language generated by compilers or disassemblers is quite difficult to read when changes must be made. Macros Many assemblers support predefined macros, and others support programmer-defined (and repeatedly re-definable) macros involving sequences of text lines in which variables and constants are embedded. The macro definition is most commonly a mixture of assembler statements, e.g., directives, symbolic machine instructions, and templates for assembler statements. This sequence of text lines may include opcodes or directives. Once a macro has been defined its name may be used in place of a mnemonic. When the assembler processes such a statement, it replaces the statement with the text lines associated with that macro, then processes them as if they existed in the source code file (including, in some assemblers, expansion of any macros existing in the replacement text). Macros in this sense date to IBM autocoders of the 1950s. Macro assemblers typically have directives to, e.g., define macros, define variables, set variables to the result of an arithmetic, logical or string expression, iterate, conditionally generate code. Some of those directives may be restricted to use within a macro definition, e.g., MEXIT in HLASM, while others may be permitted within open code (outside macro definitions), e.g., AIF and COPY in HLASM. In assembly language, the term "macro" represents a more comprehensive concept than it does in some other contexts, such as the pre-processor in the C programming language, where its #define directive typically is used to create short single line macros. Assembler macro instructions, like macros in PL/I and some other languages, can be lengthy "programs" by themselves, executed by interpretation by the assembler during assembly. Since macros can have 'short' names but expand to several or indeed many lines of code, they can be used to make assembly language programs appear to be far shorter, requiring fewer lines of source code, as with higher level languages. They can also be used to add higher levels of structure to assembly programs, optionally introduce embedded debugging code via parameters and other similar features. Macro assemblers often allow macros to take parameters. Some assemblers include quite sophisticated macro languages, incorporating such high-level language elements as optional parameters, symbolic variables, conditionals, string manipulation, and arithmetic operations, all usable during the execution of a given macro, and allowing macros to save context or exchange information. Thus a macro might generate numerous assembly language instructions or data definitions, based on the macro arguments. This could be used to generate record-style data structures or "unrolled" loops, for example, or could generate entire algorithms based on complex parameters. For instance, a "sort" macro could accept the specification of a complex sort key and generate code crafted for that specific key, not needing the run-time tests that would be required for a general procedure interpreting the specification. An organization using assembly language that has been heavily extended using such a macro suite can be considered to be working in a higher-level language since such programmers are not working with a computer's lowest-level conceptual elements. Underlining this point, macros were used to implement an early virtual machine in SNOBOL4 (1967), which was written in the SNOBOL Implementation Language (SIL), an assembly language for a virtual machine. The target machine would translate this to its native code using a macro assembler. This allowed a high degree of portability for the time. Macros were used to customize large scale software systems for specific customers in the mainframe era and were also used by customer personnel to satisfy their employers' needs by making specific versions of manufacturer operating systems. This was done, for example, by systems programmers working with IBM's Conversational Monitor System / Virtual Machine (VM/CMS) and with IBM's "real time transaction processing" add-ons, Customer Information Control System CICS, and ACP/TPF, the airline/financial system that began in the 1970s and still runs many large computer reservation systems (CRS) and credit card systems today. It is also possible to use solely the macro processing abilities of an assembler to generate code written in completely different languages, for example, to generate a version of a program in COBOL using a pure macro assembler program containing lines of COBOL code inside assembly time operators instructing the assembler to generate arbitrary code. IBM OS/360 uses macros to perform system generation. The user specifies options by coding a series of assembler macros. Assembling these macros generates a job stream to build the system, including job control language and utility control statements. This is because, as was realized in the 1960s, the concept of "macro processing" is independent of the concept of "assembly", the former being in modern terms more word processing, text processing, than generating object code. The concept of macro processing appeared, and appears, in the C programming language, which supports "preprocessor instructions" to set variables, and make conditional tests on their values. Unlike certain previous macro processors inside assemblers, the C preprocessor is not Turing-complete because it lacks the ability to either loop or "go to", the latter allowing programs to loop. Despite the power of macro processing, it fell into disuse in many high level languages (major exceptions being C, C++ and PL/I) while remaining a perennial for assemblers. Macro parameter substitution is strictly by name: at macro processing time, the value of a parameter is textually substituted for its name. The most famous class of bugs resulting was the use of a parameter that itself was an expression and not a simple name when the macro writer expected a name. In the macro: foo: macro a load a*b the intention was that the caller would provide the name of a variable, and the "global" variable or constant b would be used to multiply "a". If foo is called with the parameter a-c, the macro expansion of load a-c*b occurs. To avoid any possible ambiguity, users of macro processors can parenthesize formal parameters inside macro definitions, or callers can parenthesize the input parameters. Support for structured programming Packages of macros have been written providing structured programming elements to encode execution flow. The earliest example of this approach was in the Concept-14 macro set, originally proposed by Harlan Mills (March 1970), and implemented by Marvin Kessler at IBM's Federal Systems Division, which provided IF/ELSE/ENDIF and similar control flow blocks for OS/360 assembler programs. This was a way to reduce or eliminate the use of GOTO operations in assembly code, one of the main factors causing spaghetti code in assembly language. This approach was widely accepted in the early 1980s (the latter days of large-scale assembly language use). IBM's High Level Assembler Toolkit includes such a macro package. A curious design was A-natural, a "stream-oriented" assembler for 8080/Z80, processors from Whitesmiths Ltd. (developers of the Unix-like Idris operating system, and what was reported to be the first commercial C compiler). The language was classified as an assembler because it worked with raw machine elements such as opcodes, registers, and memory references; but it incorporated an expression syntax to indicate execution order. Parentheses and other special symbols, along with block-oriented structured programming constructs, controlled the sequence of the generated instructions. A-natural was built as the object language of a C compiler, rather than for hand-coding, but its logical syntax won some fans. There has been little apparent demand for more sophisticated assemblers since the decline of large-scale assembly language development. In spite of that, they are still being developed and applied in cases where resource constraints or peculiarities in the target system's architecture prevent the effective use of higher-level languages. Assemblers with a strong macro engine allow structured programming via macros, such as the switch macro provided with the Masm32 package (this code is a complete program): include \masm32\include\masm32rt.inc ; use the Masm32 library .code demomain: REPEAT 20 switch rv(nrandom, 9) ; generate a number between 0 and 8 mov ecx, 7 case 0 print "case 0" case ecx ; in contrast to most other programming languages, print "case 7" ; the Masm32 switch allows "variable cases" case 1 .. 3 .if eax==1 print "case 1" .elseif eax==2 print "case 2" .else print "cases 1 to 3: other" .endif case 4, 6, 8 print "cases 4, 6 or 8" default mov ebx, 19 ; print 20 stars .Repeat print "*" dec ebx .Until Sign? ; loop until the sign flag is set endsw print chr$(13, 10) ENDM exit end demomain Use of assembly language Historical perspective Assembly languages were not available at the time when the stored-program computer was introduced. Kathleen Booth "is credited with inventing assembly language" based on theoretical work she began in 1947, while working on the ARC2 at Birkbeck, University of London following consultation by Andrew Booth (later her husband) with mathematician John von Neumann and physicist Herman Goldstine at the Institute for Advanced Study. In late 1948, the Electronic Delay Storage Automatic Calculator (EDSAC) had an assembler (named "initial orders") integrated into its bootstrap program. It used one-letter mnemonics developed by David Wheeler, who is credited by the IEEE Computer Society as the creator of the first "assembler". Reports on the EDSAC introduced the term "assembly" for the process of combining fields into an instruction word. SOAP (Symbolic Optimal Assembly Program) was an assembly language for the IBM 650 computer written by Stan Poley in 1955. Assembly languages eliminate much of the error-prone, tedious, and time-consuming first-generation programming needed with the earliest computers, freeing programmers from tedium such as remembering numeric codes and calculating addresses. Assembly languages were once widely used for all sorts of programming. However, by the 1980s (1990s on microcomputers), their use had largely been supplanted by higher-level languages, in the search for improved programming productivity. Today, assembly language is still used for direct hardware manipulation, access to specialized processor instructions, or to address critical performance issues. Typical uses are device drivers, low-level embedded systems, and real-time systems. Historically, numerous programs have been written entirely in assembly language. The Burroughs MCP (1961) was the first computer for which an operating system was not developed entirely in assembly language; it was written in Executive Systems Problem Oriented Language (ESPOL), an Algol dialect. Many commercial applications were written in assembly language as well, including a large amount of the IBM mainframe software written by large corporations. COBOL, FORTRAN and some PL/I eventually displaced much of this work, although a number of large organizations retained assembly-language application infrastructures well into the 1990s. Most early microcomputers relied on hand-coded assembly language, including most operating systems and large applications. This was because these systems had severe resource constraints, imposed idiosyncratic memory and display architectures, and provided limited, buggy system services. Perhaps more important was the lack of first-class high-level language compilers suitable for microcomputer use. A psychological factor may have also played a role: the first generation of microcomputer programmers retained a hobbyist, "wires and pliers" attitude. In a more commercial context, the biggest reasons for using assembly language were minimal bloat (size), minimal overhead, greater speed, and reliability. Typical examples of large assembly language programs from this time are IBM PC DOS operating systems, the Turbo Pascal compiler and early applications such as the spreadsheet program Lotus 1-2-3. Assembly language was used to get the best performance out of the Sega Saturn, a console that was notoriously challenging to develop and program games for. The 1993 arcade game NBA Jam is another example. Assembly language has long been the primary development language for many popular home computers of the 1980s and 1990s (such as the MSX, Sinclair ZX Spectrum, Commodore 64, Commodore Amiga, and Atari ST). This was in large part because interpreted BASIC dialects on these systems offered insufficient execution speed, as well as insufficient facilities to take full advantage of the available hardware on these systems. Some systems even have an integrated development environment (IDE) with highly advanced debugging and macro facilities. Some compilers available for the Radio Shack TRS-80 and its successors had the capability to combine inline assembly source with high-level program statements. Upon compilation, a built-in assembler produced inline machine code. Current usage There have always been debates over the usefulness and performance of assembly language relative to high-level languages. Although assembly language has specific niche uses where it is important (see below), there are other tools for optimization. , the TIOBE index of programming language popularity ranks assembly language at 11, ahead of Visual Basic, for example. Assembler can be used to optimize for speed or optimize for size. In the case of speed optimization, modern optimizing compilers are claimed to render high-level languages into code that can run as fast as hand-written assembly, despite the counter-examples that can be found. The complexity of modern processors and memory sub-systems makes effective optimization increasingly difficult for compilers, as well as for assembly programmers. Moreover, increasing processor performance has meant that most CPUs sit idle most of the time, with delays caused by predictable bottlenecks such as cache misses, I/O operations and paging. This has made raw code execution speed a non-issue for many programmers. There are some situations in which developers might choose to use assembly language: Writing code for systems with that have limited high-level language options such as the Atari 2600, Commodore 64, and graphing calculators. Programs for these computers of 1970s and 1980s are often written in the context of demoscene or retrogaming subcultures. Code that must interact directly with the hardware, for example in device drivers and interrupt handlers. In an embedded processor or DSP, high-repetition interrupts require the shortest number of cycles per interrupt, such as an interrupt that occurs 1000 or 10000 times a second. Programs that need to use processor-specific instructions not implemented in a compiler. A common example is the bitwise rotation instruction at the core of many encryption algorithms, as well as querying the parity of a byte or the 4-bit carry of an addition. A stand-alone executable of compact size is required that must execute without recourse to the run-time components or libraries associated with a high-level language. Examples have included firmware for telephones, automobile fuel and ignition systems, air-conditioning control systems, security systems, and sensors. Programs with performance-sensitive inner loops, where assembly language provides optimization opportunities that are difficult to achieve in a high-level language. For example, linear algebra with BLAS or discrete cosine transformation (e.g. SIMD assembly version from x264). Programs that create vectorized functions for programs in higher-level languages such as C. In the higher-level language this is sometimes aided by compiler intrinsic functions which map directly to SIMD mnemonics, but nevertheless result in a one-to-one assembly conversion specific for the given vector processor. Real-time programs such as simulations, flight navigation systems, and medical equipment. For example, in a fly-by-wire system, telemetry must be interpreted and acted upon within strict time constraints. Such systems must eliminate sources of unpredictable delays, which may be created by (some) interpreted languages, automatic garbage collection, paging operations, or preemptive multitasking. However, some higher-level languages incorporate run-time components and operating system interfaces that can introduce such delays. Choosing assembly or lower level languages for such systems gives programmers greater visibility and control over processing details. Cryptographic algorithms that must always take strictly the same time to execute, preventing timing attacks. Modify and extend legacy code written for IBM mainframe computers. Situations where complete control over the environment is required, in extremely high-security situations where nothing can be taken for granted. Computer viruses, bootloaders, certain device drivers, or other items very close to the hardware or low-level operating system. Instruction set simulators for monitoring, tracing and debugging where additional overhead is kept to a minimum. Situations where no high-level language exists, on a new or specialized processor for which no cross compiler is available. Reverse-engineering and modifying program files such as: existing binaries that may or may not have originally been written in a high-level language, for example when trying to recreate programs for which source code is not available or has been lost, or cracking copy protection of proprietary software. Video games (also termed ROM hacking), which is possible via several methods. The most widely employed method is altering program code at the assembly language level. Assembly language is still taught in most computer science and electronic engineering programs. Although few programmers today regularly work with assembly language as a tool, the underlying concepts remain important. Such fundamental topics as binary arithmetic, memory allocation, stack processing, character set encoding, interrupt processing, and compiler design would be hard to study in detail without a grasp of how a computer operates at the hardware level. Since a computer's behavior is fundamentally defined by its instruction set, the logical way to learn such concepts is to study an assembly language. Most modern computers have similar instruction sets. Therefore, studying a single assembly language is sufficient to learn: I) the basic concepts; II) to recognize situations where the use of assembly language might be appropriate; and III) to see how efficient executable code can be created from high-level languages. Typical applications Assembly language is typically used in a system's boot code, the low-level code that initializes and tests the system hardware prior to booting the operating system and is often stored in ROM. (BIOS on IBM-compatible PC systems and CP/M is an example.) Assembly language is often used for low-level code, for instance for operating system kernels, which cannot rely on the availability of pre-existing system calls and must indeed implement them for the particular processor architecture on which the system will be running. Some compilers translate high-level languages into assembly first before fully compiling, allowing the assembly code to be viewed for debugging and optimization purposes. Some compilers for relatively low-level languages, such as Pascal or C, allow the programmer to embed assembly language directly in the source code (so called inline assembly). Programs using such facilities can then construct abstractions using different assembly language on each hardware platform. The system's portable code can then use these processor-specific components through a uniform interface. Assembly language is useful in reverse engineering. Many programs are distributed only in machine code form which is straightforward to translate into assembly language by a disassembler, but more difficult to translate into a higher-level language through a decompiler. Tools such as the Interactive Disassembler make extensive use of disassembly for such a purpose. This technique is used by hackers to crack commercial software, and competitors to produce software with similar results from competing companies. Assembly language is used to enhance speed of execution, especially in early personal computers with limited processing power and RAM. Assemblers can be used to generate blocks of data, with no high-level language overhead, from formatted and commented source code, to be used by other code. See also Compiler Comparison of assemblers Disassembler Hexadecimal Instruction set architecture Little man computer – an educational computer model with a base-10 assembly language Nibble Typed assembly language Notes References Further reading (2+xiv+270+6 pages) Kann, Charles W. (2021). "Introduction to Assembly Language Programming: From Soup to Nuts: ARM Edition" ("An online book full of helpful ASM info, tutorials and code examples" by the ASM Community, archived at the internet archive.) External links Unix Assembly Language Programming Linux Assembly PPR: Learning Assembly Language NASM – The Netwide Assembler (a popular assembly language) Assembly Language Programming Examples Authoring Windows Applications In Assembly Language Assembly Optimization Tips by Mark Larson The table for assembly language to machine code Assembly language Computer-related introductions in 1949 Embedded systems Low-level programming languages Programming language implementation Programming languages created in 1949

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1404

https://en.wikipedia.org/wiki/AV

AV

AV and variants may refer to: Arts and entertainment A.V. (film), a 2005 Hong Kong film directed by Pang Ho-Cheung Adult video, a pornographic film Audiovisual, possessing both a sound and a visual component AV The Hunt, a 2020 Turkish thriller film directed by Emre Akay Businesses and organizations America Votes, an American 501(c)4 organization that promotes progressive causes Anonymous for the Voiceless, a grassroots animal rights organisation specialising in street activism Aston Villa F.C., an English football club AV Akademikerverlag GmbH & Co. KG, an imprint of the German group VDM Publishing Avaya, a technology company formerly listed on the New York Stock Exchange with symbol "AV" Avianca (IATA airline code AV) Aviva, British insurance company, listed on the New York Stock Exchange and London Stock Exchange as "AV" AeroVironment, manufacturer of unmanned military aircraft and systems Amusement Vision, Former name of "Ryu Ga Gotoku Studio" used from 2000 to 2005 Places Anguilla (FIPS 10-4 and obsolete NATO digram AV) Antelope Valley, a valley in Southern California where pronghorn antelope are said to have once lived Province of Avellino, a province of Italy in the ISO 3166-2:IT code Science and technology Anatomy and medicine Aerobic vaginitis, vaginal infection associated with overgrowth of aerobic bacteria Arteriovenous (disambiguation) Atrioventricular (disambiguation) Electronics and computing Access violation, a computer software error Age verification, system for checking a user's age Antivirus software, used to prevent, detect and remove malicious software Audio and video connector, a cable between two devices Analog video Fluid dynamics Annular velocity Apparent viscosity Vehicles AV (cyclecar) Bavarian A V, an 1853 steam locomotive model AV, the designation for "seaplane tender" in the United States Navy's ship classification system Autonomous cars (known as autonomous vehicles) Other uses in science and technology A-type main-sequence star, in astronomy, abbreviated AV Aperture value mode, in photography Other uses Alternative vote, an electoral system used to elect a single winner from a field of more than two candidates Approval voting, a non-ranking vote system Authorised Version of the Bible (also known as King James Version) Av, a month in the Hebrew calendar av, the Avar language (ISO 639-1 code) Av. or Ave, an abbreviation for Avenue (disambiguation) Ꜹ or AV from Latin aurum (avrvm), a numismatic abbreviation for "gold" A.V. the putative mark of ébéniste Adam Weisweiler Aviation, abbreviated Av, in military use See also A5 (disambiguation) α5 (disambiguation) AV idol, a type of Japanese porn star

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1408

https://en.wikipedia.org/wiki/Alcuin

Alcuin

Alcuin of York (; ; 735 – 19 May 804) – also called Ealhwine, Alhwin, or Alchoin – was an English scholar, clergyman, poet, and teacher from York, Northumbria. He was born around 735 and became the student of Archbishop Ecgbert at York. At the invitation of Charlemagne, he became a leading scholar and teacher at the Carolingian court, where he remained a figure in the 780s and 790s. "The most learned man anywhere to be found", according to Einhard's Life of Charlemagne (c. 817–833), he is considered among the most important intellectual architects of the Carolingian Renaissance. Among his pupils were many of the dominant intellectuals of the Carolingian era. During this period, he perfected Carolingian minuscule, an easily read manuscript hand using a mixture of upper- and lower-case letters. Latin paleography in the eighth century leaves little room for a single origin of the script, and sources contradict his importance as no proof has been found of his direct involvement in the creation of the script. Carolingian minuscule was already in use before Alcuin arrived in Francia. Most likely he was responsible for copying and preserving the script while at the same time restoring the purity of the form. Alcuin wrote many theological and dogmatic treatises, as well as a few grammatical works and a number of poems. In 796, he was made abbot of Marmoutier Abbey, in Tours, where he remained until his death. Biography Background Alcuin was born in Northumbria, presumably sometime in the 730s. Virtually nothing is known of his parents, family background, or origin. In common hagiographical fashion, the Vita Alcuini asserts that Alcuin was "of noble English stock", and this statement has usually been accepted by scholars. Alcuin's own work only mentions such collateral kinsmen as Wilgils, father of the missionary saint Willibrord; and Beornrad (also spelled Beornred), abbot of Echternach and bishop of Sens. Willibrord, Alcuin and Beornrad were all related by blood. In his Life of St Willibrord, Alcuin writes that Wilgils, called a paterfamilias, had founded an oratory and church at the mouth of the Humber, which had fallen into Alcuin's possession by inheritance. Because in early Anglo-Latin writing paterfamilias ("head of a family, householder") usually referred to a ("churl"), Donald A. Bullough suggests that Alcuin's family was of ("churlish") status: i.e., free but subordinate to a noble lord, and that Alcuin and other members of his family rose to prominence through beneficial connections with the aristocracy. If so, Alcuin's origins may lie in the southern part of what was formerly known as Deira. York The young Alcuin came to the cathedral church of York during the golden age of Archbishop Ecgbert and his brother, the Northumbrian King Eadberht. Ecgbert had been a disciple of the Venerable Bede, who urged him to raise York to an archbishopric. King Eadberht and Archbishop Ecgbert oversaw the re-energising and reorganisation of the English church, with an emphasis on reforming the clergy and on the tradition of learning that Bede had begun. Ecgbert was devoted to Alcuin, who thrived under his tutelage. The York school was renowned as a centre of learning in the liberal arts, literature, and science, as well as in religious matters. From here, Alcuin drew inspiration for the school he would lead at the Frankish court. He revived the school with the trivium and quadrivium disciplines, writing a codex on the trivium, while his student Hraban wrote one on the quadrivium. Alcuin graduated to become a teacher during the 750s. His ascendancy to the headship of the York school, the ancestor of St Peter's School, began after Aelbert became Archbishop of York in 767. Around the same time, Alcuin became a deacon in the church. He was never ordained a priest. Though no real evidence shows that he took monastic vows, he lived as if he had. In 781, King Elfwald sent Alcuin to Rome to petition the pope for official confirmation of York's status as an archbishopric and to confirm the election of the new archbishop, Eanbald I. On his way home, he met Charlemagne (whom he had met once before), this time in the Italian city of Parma. Charlemagne Alcuin's intellectual curiosity allowed him to be reluctantly persuaded to join Charlemagne's court. He joined an illustrious group of scholars whom Charlemagne had gathered around him, the mainsprings of the Carolingian Renaissance: Peter of Pisa, Paulinus of Aquileia, Rado, and Abbot Fulrad. Alcuin would later write, "the Lord was calling me to the service of King Charles". Alcuin became master of the Palace School of Charlemagne in Aachen () in 782. It had been founded by the king's ancestors as a place for the education of the royal children (mostly in manners and the ways of the court). However, Charlemagne wanted to include the liberal arts, and most importantly, the study of religion. From 782 to 790, Alcuin taught Charlemagne himself, his sons Pepin and Louis, as well as young men sent to be educated at court, and the young clerics attached to the palace chapel. Bringing with him from York his assistants Pyttel, Sigewulf, and Joseph, Alcuin revolutionised the educational standards of the Palace School, introducing Charlemagne to the liberal arts and creating a personalised atmosphere of scholarship and learning, to the extent that the institution came to be known as the 'school of Master Albinus'. In this role as adviser, he took issue with the emperor's policy of forcing pagans to be baptised on pain of death, arguing, "Faith is a free act of the will, not a forced act. We must appeal to the conscience, not compel it by violence. You can force people to be baptised, but you cannot force them to believe." His arguments seem to have prevailed – Charlemagne abolished the death penalty for paganism in 797. Charlemagne gathered the best men of every land in his court, and became far more than just the king at the centre. It seems that he made many of these men his closest friends and counsellors. They referred to him as 'David', a reference to the Biblical king David. Alcuin soon found himself on intimate terms with Charlemagne and the other men at court, where pupils and masters were known by affectionate and jesting nicknames. Alcuin himself was known as 'Albinus' or 'Flaccus'. While at Aachen, Alcuin bestowed pet names upon his pupils – derived mainly from Virgil's Eclogues. According to the Encyclopædia Britannica, "He loved Charlemagne and enjoyed the king's esteem, but his letters reveal that his fear of him was as great as his love." Return to Northumbria and back to Francia In 790, Alcuin returned from the court of Charlemagne to England, to which he had remained attached. He dwelt there for some time, but Charlemagne then invited him back to help in the fight against the Adoptionist heresy, which was at that time making great progress in Toledo, the old capital of the Visigoths and still a major city for the Christians under Islamic rule in Spain. He is believed to have had contacts with Beatus of Liébana, from the Kingdom of Asturias, who fought against Adoptionism. At the Council of Frankfurt in 794, Alcuin upheld the orthodox doctrine against the views expressed by Felix of Urgel, an heresiarch according to the Catholic Encyclopaedia. Having failed during his stay in Northumbria to influence King Æthelred in the conduct of his reign, Alcuin never returned home. He was back at Charlemagne's court by at least mid-792, writing a series of letters to Æthelred, to Hygbald, Bishop of Lindisfarne, and to Æthelhard, Archbishop of Canterbury in the succeeding months, dealing with the Viking attack on Lindisfarne in July 793. These letters and Alcuin's poem on the subject, , provide the only significant contemporary account of these events. In his description of the Viking attack, he wrote: "Never before has such terror appeared in Britain. Behold the church of St Cuthbert, splattered with the blood of God's priests, robbed of its ornaments." Tours and death In 796, Alcuin was in his 60s. He hoped to be free from court duties and upon the death of Abbot Itherius of Saint Martin at Tours, Charlemagne put Marmoutier Abbey into Alcuin's care, with the understanding that he should be available if the king ever needed his counsel. There, he encouraged the work of the monks on the beautiful Carolingian minuscule script, ancestor of modern Roman typefaces. Alcuin died on 19 May 804, some 10 years before the emperor, and was buried at St. Martin's Church under an epitaph that partly read: The majority of details on Alcuin's life come from his letters and poems. Also, autobiographical sections are in Alcuin's poem on York and in the Vita Alcuini, a hagiography written for him at Ferrières in the 820s, possibly based in part on the memories of Sigwulf, one of Alcuin's pupils. Carolingian Renaissance figure and legacy Mathematician The collection of mathematical and logical word problems entitled Propositiones ad acuendos juvenes ("Problems to Sharpen Youths") is sometimes attributed to Alcuin. In a 799 letter to Charlemagne, the scholar claimed to have sent "certain figures of arithmetic for the joy of cleverness", which some scholars have identified with the Propositiones. The text contains about 53 mathematical word problems (with solutions), in no particular pedagogical order. Among the most famous of these problems are: four that involve river crossings, including the problem of three anxious brothers, each of whom has an unmarried sister whom he cannot leave alone with either of the other men lest she be defiled (Problem 17); the problem of the wolf, goat, and cabbage (Problem 18); and the problem of "the two adults and two children where the children weigh half as much as the adults" (Problem 19). Alcuin's sequence is the solution to one of the problems of that book. Literary influence Alcuin made the abbey school into a model of excellence and many students flocked to it. He had many manuscripts copied using outstandingly beautiful calligraphy, the Carolingian minuscule based on round and legible uncial letters. He wrote many letters to his English friends, to Arno, bishop of Salzburg and above all to Charlemagne. These letters (of which 311 are extant) are filled mainly with pious meditations, but they form an important source of information as to the literary and social conditions of the time and are the most reliable authority for the history of humanism during the Carolingian age. Alcuin trained the numerous monks of the abbey in piety, and in the midst of these pursuits, he died. Alcuin is the most prominent figure of the Carolingian Renaissance, in which three main periods have been distinguished: in the first of these, up to the arrival of Alcuin at the court, the Italians occupy a central place; in the second, Alcuin and the English are dominant; in the third (from 804), the influence of Theodulf the Visigoth is preponderant. Alcuin also developed manuals used in his educational work – a grammar and works on rhetoric and dialectics. These are written in the form of a dialogue, and in two of them the interlocutors are Charlemagne and Alcuin. He wrote several theological treatises: a De fide Trinitatis, and commentaries on the Bible. Alcuin is credited with inventing the first known question mark, though it did not resemble the modern symbol. Alcuin transmitted to the Franks the knowledge of Latin culture, which had existed in Anglo-Saxon England. A number of his works still exist. Besides some graceful epistles in the style of Venantius Fortunatus, he wrote some long poems, and notably he is the author of a history (in verse) of the church at York, Versus de patribus, regibus et sanctis Eboracensis ecclesiae. At the same time, he is noted for making one of the only explicit comments on Old English poetry surviving from the early Middle Ages, in a letter to one Speratus, the bishop of an unnamed English see (possibly Unwona of Leicester): ("Let God's words be read at the episcopal dinner-table. It is right that a reader should be heard, not a harpist, patristic discourse, not pagan song. What has Hinield to do with Christ?"). Use of homoerotic language in writings Historian John Boswell cited Alcuin's writings as demonstrating a personal outpouring of his internalized homosexual feelings. Others agree that Alcuin at times "comes perilously close to communicating openly his same-sex desires", and this reflects the erotic subculture of the Carolingian monastic school, but also perhaps a 'queer space' where "erotic attachment and affections may be safely articulated". According to David Clark, passages in some of Alcuin's writings can be seen to display homosocial desire, even possibly homoerotic imagery. However, he argues that it is not possible to necessarily determine whether they were the result of an outward expression of erotic feelings on the part of Alcuin. The interpretation of homosexual desire has been disputed by Allen Frantzen, who identifies Alcuin's language with that of medieval Christian amicitia or friendship. Douglas Dales and Rowan Williams say "the use of language drawn [by Alcuin] from the Song of Songs transforms apparently erotic language into something within Christian friendship – 'an ordained affection. Alcuin was also a close friend of Charlemagne's sister Gisela, Abbess of Chelles, and he hailed her as "a noble sister in the bond of sweet love". He wrote to Charlemagne's daughters Rotrudis and Bertha, "the devotion of my heart specially tends towards you both because of the familiarity and dedication you have shown me". He dedicated the last two books of his commentary on John's gospel to them both. Despite inconclusive evidence of Alcuin's personal passions, he was clear in his own writings that the men of Sodom had been punished with fire for "sinning against nature with men" – a view commonly held by the Church at the time. Such sins, argued Alcuin, were therefore more serious than lustful acts with women, for which the earth was cleansed and revivified by the water of the Flood, and merit to be "withered by flames unto eternal barrenness". Legacy Alcuin is remembered in the Church of England with a Lesser Festival on 20 May, the first available day after the day of his death (as Dunstan is celebrated on 19 May). Alcuin College, one of the colleges of the University of York, England, is named after him. In January 2020, Alcuin was the subject of the BBC Radio 4 programme In Our Time. Quotations : "Remember to care for the soul more than the body, since the former remains, the latter perishes." : "And do not listen to those who keep saying, 'The voice of the people is the voice of God', because the tumult of the crowd is always close to madness." "In the morning, at the height of my powers, I sowed the seed in Britain; now in the evening when my blood is growing cold, I am still sowing in France, hoping both will grow, by the grace of God, giving some the honey of the holy scriptures, making others drunk on the old wine of ancient learning..." Selected works For a complete census of Alcuin's works, see Marie-Hélène Jullien and Françoise Perelman, eds., Clavis scriptorum latinorum medii aevi: Auctores Galliae 735–987. Tomus II: Alcuinus. Turnhout: Brepols, 1999. Poetry Carmina, ed. Ernst Dümmler, MGH Poetae Latini aevi Carolini I. Berlin: Weidmann, 1881. 160–351. Godman, Peter, tr., Poetry of the Carolingian Renaissance. Norman, University of Oklahoma Press, 1985. 118–149. Stella, Francesco, tr., comm., La poesia carolingia, Firenze: Le Lettere, 1995, pp. 94–96, 152–61, 266–67, 302–307, 364–371, 399–404, 455–457, 474–477, 503–507. Isbell, Harold, tr.. The Last Poets of Imperial Rome. Baltimore: Penguin, 1971. Poem on York, Versus de patribus, regibus et sanctis Euboricensis ecclesiae, ed. and tr. Peter Godman, The Bishops, Kings, and Saints of York. Oxford: Clarendon Press, 1982. De clade Lindisfarnensis monasterii, "On the destruction of the monastery of Lindisfarne" (Carmen 9, ed. Dümmler, pp. 229–235). Letters Of Alcuin's letters, just over 310 have survived. Epistolae, ed. Ernst Dümmler, MGH Epistolae IV.2. Berlin: Weidmann, 1895. 1–493. Jaffé, Philipp, Ernst Dümmler, and W. Wattenbach, eds. Monumenta Alcuiniana. Berlin: Weidmann, 1873. 132–897. Chase, Colin, ed. Two Alcuin Letter-books. Toronto: Pontifical Institute of Mediaeval Studies, 1975. Allott, Stephen, tr. Alcuin of York, c. AD 732 to 804. His life and letters. York: William Sessions, 1974. Sturgeon, Thomas G., tr. The Letters of Alcuin: Part One, the Aachen Period (762–796). Harvard University PhD thesis, 1953. Didactic works Ars grammatica. PL 101: 854–902. De orthographia, ed. H. Keil, Grammatici Latini VII, 1880. 295–312; ed. Sandra Bruni, Alcuino de orthographia. Florence: SISMEL, 1997. De dialectica. PL 101: 950–976. Disputatio regalis et nobilissimi juvenis Pippini cum Albino scholastico "Dialogue of Pepin, the Most Noble and Royal Youth, with the Teacher Albinus", ed. L. W. Daly and W. Suchier, Altercatio Hadriani Augusti et Epicteti Philosophi. Urbana, IL: University of Illinois Press, 1939. 134–146; ed. Wilhelm Wilmanns, "Disputatio regalis et nobilissimi juvenis Pippini cum Albino scholastico". Zeitschrift für deutsches Altertum 14 (1869): 530–555, 562. Disputatio de rhetorica et de virtutibus sapientissimi regis Carli et Albini magistri, ed. and tr. Wilbur Samuel Howell, The Rhetoric of Alcuin and Charlemagne. New York: Russell and Russell, 1965 (1941); ed. C. Halm, Rhetorici Latini Minores. Leipzig: Teubner, 1863. 523–550. De virtutibus et vitiis (moral treatise dedicated to Count Wido of Brittany, 799–800). PL 101: 613–639 (transcript available online). A new critical edition is being prepared for the Corpus Christianorum, Continuatio Medievalis. De animae ratione (ad Eulaliam virginem) (written for Gundrada, Charlemagne's cousin). PL 101: 639–650. De Cursu et Saltu Lunae ac Bissexto, astronomical treatise. PL 101: 979–1002. (?) Propositiones ad acuendos iuvenes, ed. Menso Folkerts, "Die alteste mathematische Aufgabensammlung in lateinischer Sprache: Die Alkuin zugeschriebenen Propositiones ad acuendos iuvenes; Überlieferung, Inhalt, Kritische Edition", in idem, Essays on Early Medieval Mathematics: The Latin Tradition. Aldershot: Ashgate, 2003. Theology Compendium in Canticum Canticorum: Alcuino, Commento al Cantico dei cantici – con i commenti anonimi Vox ecclesie e Vox antique ecclesie, ed. Rossana Guglielmetti, Firenze, SISMEL 2004 Quaestiones in Genesim. PL 100: 515–566. De Fide Sanctae Trinitatis et de Incarnatione Christi; Quaestiones de Sancta Trinitate, ed. E. Knibbs and E. Ann Matter (Corpus Christianorum – Continuatio Mediaevalis 249: Brepols, 2012) Hagiography Vita II Vedastis episcopi Atrebatensis. Revision of the earlier Vita Vedastis by Jonas of Bobbio. Patrologia Latina 101: 663–682. Vita Richarii confessoris Centulensis. Revision of an earlier anonymous life. MGH Scriptores Rerum Merovingicarum 4: 381–401. Vita Willibrordi archiepiscopi Traiectensis, ed. W. Levison, Passiones vitaeque sanctorum aevi Merovingici. MGH Scriptores Rerum Merovingicarum 7: 81–141. See also Propositiones ad Acuendos Juvenes Carolingian art Carolingian Empire Category: Carolingian period Correctory Codex Vindobonensis 795 References Notes Citations Sources Allott, Stephen. Alcuin of York, his life and letters </ Dales, Douglas J. 'Accessing Alcuin: A Master Bibliography' (James Clarke & Co., Cambridge, 2013), Diem, Albrecht, 'The Emergence of Monastic Schools. The Role of Alcuin', in: Luuk A. J. R. Houwen and Alasdair A. McDonald (eds.), Alcuin of York. Scholar at the Carolingian Court, Groningen 1998 (Germania Latina, vol. 3), pp. 27–44. Duckett, Eleanor Shipley. Carolingian Portraits, (1962) Ganshof, F.L. The Carolingians and the Frankish Monarchy Godman, Peter. Poetry of the Carolingian Renaissance Lorenz, Frederick. The life of Alcuin (Thomas Hurst, 1837). McGuire, Brian P. Friendship, and Community: The Monastic Experience Murphy, Richard E. Alcuin of York: De Virtutibus et Vitiis, Virtues and Vices. Stehling, Thomas. Medieval Latin Love Poems of Male Love and Friendship. Stella, Francesco, "Alkuins Dichtung" in Alkuin von York und die geistige Grundlegung Europas , Sankt Gallen, Verlag am Klosterhof, 2010, pp. 107–28. Throop, Priscilla, trans. Alcuin: His Life; On Virtues and Vices; Dialogue with Pepin (Charlotte, VT: MedievalMS, 2011) West, Andrew Fleming. Alcuin and the Rise of the Christian Schools (C. Scribner's Sons, 1912) External links Alcuin's book, Problems for the Quickening of the Minds of the Young Introduction to Alcuin's writings by Robert Levine and Whitney Bolton The Alcuin Society Anglo-Saxon York on History of York site Corpus Christianorum, Continuatio Mediaevalis: new critical editions in preparation Corpus Grammaticorum Latinorum: complete texts and full bibliography The Life of Alcuin by Dr. Frederick Lorenz 730s births 804 deaths 8th-century astronomers 8th-century Christian theologians 8th-century English writers 8th-century Frankish writers 8th-century Latin writers 8th-century mathematicians 8th-century philosophers 8th-century poets 9th-century Christian monks 9th-century Christian theologians 9th-century English writers 9th-century philosophers Anglo-Saxon poets Anglo-Saxon saints Anglo-Saxon writers Carolingian poets Christian hagiographers Deacons English monks Grammarians of Latin LGBT and Catholicism Latin texts of Anglo-Saxon England Medieval chancellors (government) Medieval English mathematicians Medieval English theologians Medieval Latin poets Medieval LGBT history Medieval linguists People from York Saints of the Carolingian Empire Scholastic philosophers Sources on Germanic paganism Writers of the Carolingian Empire Anglican saints

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1418

https://en.wikipedia.org/wiki/Absolute%20zero

Absolute zero

Absolute zero is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15 degrees on the Celsius scale (International System of Units), which equals −459.67 degrees on the Fahrenheit scale (United States customary units or Imperial units). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition. It is commonly thought of as the lowest temperature possible, but it is not the lowest enthalpy state possible, because all real substances begin to depart from the ideal gas when cooled as they approach the change of state to liquid, and then to solid; and the sum of the enthalpy of vaporization (gas to liquid) and enthalpy of fusion (liquid to solid) exceeds the ideal gas's change in enthalpy to absolute zero. In the quantum-mechanical description, matter (solid) at absolute zero is in its ground state, the point of lowest internal energy. The laws of thermodynamics indicate that absolute zero cannot be reached using only thermodynamic means, because the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically, and a system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state at absolute zero. The kinetic energy of the ground state cannot be removed. Scientists and technologists routinely achieve temperatures close to absolute zero, where matter exhibits quantum effects such as Bose–Einstein condensate, superconductivity and superfluidity. Thermodynamics near absolute zero At temperatures near , nearly all molecular motion ceases and ΔS = 0 for any adiabatic process, where S is the entropy. In such a circumstance, pure substances can (ideally) form perfect crystals with no structural imperfections as T → 0. Max Planck's strong form of the third law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The original Nernst heat theorem makes the weaker and less controversial claim that the entropy change for any isothermal process approaches zero as T → 0: The implication is that the entropy of a perfect crystal approaches a constant value. An adiabat is a state with constant entropy, typically represented on a graph as a curve in a manner similar to isotherms and isobars. The Nernst postulate identifies the isotherm T = 0 as coincident with the adiabat S = 0, although other isotherms and adiabats are distinct. As no two adiabats intersect, no other adiabat can intersect the T = 0 isotherm. Consequently no adiabatic process initiated at nonzero temperature can lead to zero temperature. (≈ Callen, pp. 189–190) A perfect crystal is one in which the internal lattice structure extends uninterrupted in all directions. The perfect order can be represented by translational symmetry along three (not usually orthogonal) axes. Every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. For substances that exist in two (or more) stable crystalline forms, such as diamond and graphite for carbon, there is a kind of chemical degeneracy. The question remains whether both can have zero entropy at T = 0 even though each is perfectly ordered. Perfect crystals never occur in practice; imperfections, and even entire amorphous material inclusions, can and do get "frozen in" at low temperatures, so transitions to more stable states do not occur. Using the Debye model, the specific heat and entropy of a pure crystal are proportional to T 3, while the enthalpy and chemical potential are proportional to T 4. (Guggenheim, p. 111) These quantities drop toward their T = 0 limiting values and approach with zero slopes. For the specific heats at least, the limiting value itself is definitely zero, as borne out by experiments to below 10 K. Even the less detailed Einstein model shows this curious drop in specific heats. In fact, all specific heats vanish at absolute zero, not just those of crystals. Likewise for the coefficient of thermal expansion. Maxwell's relations show that various other quantities also vanish. These phenomena were unanticipated. Since the relation between changes in Gibbs free energy (G), the enthalpy (H) and the entropy is thus, as T decreases, ΔG and ΔH approach each other (so long as ΔS is bounded). Experimentally, it is found that all spontaneous processes (including chemical reactions) result in a decrease in G as they proceed toward equilibrium. If ΔS and/or T are small, the condition ΔG < 0 may imply that ΔH < 0, which would indicate an exothermic reaction. However, this is not required; endothermic reactions can proceed spontaneously if the TΔS term is large enough. Moreover, the slopes of the derivatives of ΔG and ΔH converge and are equal to zero at T = 0. This ensures that ΔG and ΔH are nearly the same over a considerable range of temperatures and justifies the approximate empirical Principle of Thomsen and Berthelot, which states that the equilibrium state to which a system proceeds is the one that evolves the greatest amount of heat, i.e., an actual process is the most exothermic one. (Callen, pp. 186–187) One model that estimates the properties of an electron gas at absolute zero in metals is the Fermi gas. The electrons, being fermions, must be in different quantum states, which leads the electrons to get very high typical velocities, even at absolute zero. The maximum energy that electrons can have at absolute zero is called the Fermi energy. The Fermi temperature is defined as this maximum energy divided by Boltzmann's constant, and is on the order of 80,000 K for typical electron densities found in metals. For temperatures significantly below the Fermi temperature, the electrons behave in almost the same way as at absolute zero. This explains the failure of the classical equipartition theorem for metals that eluded classical physicists in the late 19th century. Relation with Bose–Einstein condensate A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of weakly interacting bosons confined in an external potential and cooled to temperatures very near absolute zero. Under such conditions, a large fraction of the bosons occupy the lowest quantum state of the external potential, at which point quantum effects become apparent on a macroscopic scale. This state of matter was first predicted by Satyendra Nath Bose and Albert Einstein in 1924–25. Bose first sent a paper to Einstein on the quantum statistics of light quanta (now called photons). Einstein was impressed, translated the paper from English to German and submitted it for Bose to the Zeitschrift für Physik, which published it. Einstein then extended Bose's ideas to material particles (or matter) in two other papers. Seventy years later, in 1995, the first gaseous condensate was produced by Eric Cornell and Carl Wieman at the University of Colorado at Boulder NIST-JILA lab, using a gas of rubidium atoms cooled to 170 nanokelvin (nK) (). A record cold temperature of 450 ± 80 picokelvin (pK) () in a BEC of sodium atoms was achieved in 2003 by researchers at Massachusetts Institute of Technology (MIT). The associated black-body (peak emittance) wavelength of 6,400 kilometers is roughly the radius of Earth. Absolute temperature scales Absolute, or thermodynamic, temperature is conventionally measured in kelvin (Celsius-scaled increments) and in the Rankine scale (Fahrenheit-scaled increments) with increasing rarity. Absolute temperature measurement is uniquely determined by a multiplicative constant which specifies the size of the degree, so the ratios of two absolute temperatures, T2/T1, are the same in all scales. The most transparent definition of this standard comes from the Maxwell–Boltzmann distribution. It can also be found in Fermi–Dirac statistics (for particles of half-integer spin) and Bose–Einstein statistics (for particles of integer spin). All of these define the relative numbers of particles in a system as decreasing exponential functions of energy (at the particle level) over kT, with k representing the Boltzmann constant and T representing the temperature observed at the macroscopic level. Negative temperatures Temperatures that are expressed as negative numbers on the familiar Celsius or Fahrenheit scales are simply colder than the zero points of those scales. Certain systems can achieve truly negative temperatures; that is, their thermodynamic temperature (expressed in kelvins) can be of a negative quantity. A system with a truly negative temperature is not colder than absolute zero. Rather, a system with a negative temperature is hotter than any system with a positive temperature, in the sense that if a negative-temperature system and a positive-temperature system come in contact, heat flows from the negative to the positive-temperature system. Most familiar systems cannot achieve negative temperatures because adding energy always increases their entropy. However, some systems have a maximum amount of energy that they can hold, and as they approach that maximum energy their entropy actually begins to decrease. Because temperature is defined by the relationship between energy and entropy, such a system's temperature becomes negative, even though energy is being added. As a result, the Boltzmann factor for states of systems at negative temperature increases rather than decreases with increasing state energy. Therefore, no complete system, i.e. including the electromagnetic modes, can have negative temperatures, since there is no highest energy state, so that the sum of the probabilities of the states would diverge for negative temperatures. However, for quasi-equilibrium systems (e.g. spins out of equilibrium with the electromagnetic field) this argument does not apply, and negative effective temperatures are attainable. On 3 January 2013, physicists announced that for the first time they had created a quantum gas made up of potassium atoms with a negative temperature in motional degrees of freedom. History One of the first to discuss the possibility of an absolute minimal temperature was Robert Boyle. His 1665 New Experiments and Observations touching Cold, articulated the dispute known as the primum frigidum. The concept was well known among naturalists of the time. Some contended an absolute minimum temperature occurred within earth (as one of the four classical elements), others within water, others air, and some more recently within nitre. But all of them seemed to agree that, "There is some body or other that is of its own nature supremely cold and by participation of which all other bodies obtain that quality." Limit to the "degree of cold" The question whether there is a limit to the degree of coldness possible, and, if so, where the zero must be placed, was first addressed by the French physicist Guillaume Amontons in 1702, in connection with his improvements in the air thermometer. His instrument indicated temperatures by the height at which a certain mass of air sustained a column of mercury—the volume, or "spring" of the air varying with temperature. Amontons therefore argued that the zero of his thermometer would be that temperature at which the spring of the air was reduced to nothing. He used a scale that marked the boiling point of water at +73 and the melting point of ice at +, so that the zero was equivalent to about −240 on the Celsius scale. Amontons held that the absolute zero cannot be reached, so never attempted to compute it explicitly. The value of −240 °C, or "431 divisions [in Fahrenheit's thermometer] below the cold of freezing water" was published by George Martine in 1740. This close approximation to the modern value of −273.15 °C for the zero of the air thermometer was further improved upon in 1779 by Johann Heinrich Lambert, who observed that might be regarded as absolute cold. Values of this order for the absolute zero were not, however, universally accepted about this period. Pierre-Simon Laplace and Antoine Lavoisier, in their 1780 treatise on heat, arrived at values ranging from 1,500 to 3,000 below the freezing point of water, and thought that in any case it must be at least 600 below. John Dalton in his Chemical Philosophy gave ten calculations of this value, and finally adopted −3,000 °C as the natural zero of temperature. Lord Kelvin's work After James Prescott Joule had determined the mechanical equivalent of heat, Lord Kelvin approached the question from an entirely different point of view, and in 1848 devised a scale of absolute temperature that was independent of the properties of any particular substance and was based on Carnot's theory of the Motive Power of Heat and data published by Henri Victor Regnault. It followed from the principles on which this scale was constructed that its zero was placed at −273 °C, at almost precisely the same point as the zero of the air thermometer. This value was not immediately accepted; values ranging from to , derived from laboratory measurements and observations of astronomical refraction, remained in use in the early 20th century. The race to absolute zero With a better theoretical understanding of absolute zero, scientists were eager to reach this temperature in the lab. By 1845, Michael Faraday had managed to liquefy most gases then known to exist, and reached a new record for lowest temperatures by reaching . Faraday believed that certain gases, such as oxygen, nitrogen, and hydrogen, were permanent gases and could not be liquefied. Decades later, in 1873 Dutch theoretical scientist Johannes Diderik van der Waals demonstrated that these gases could be liquefied, but only under conditions of very high pressure and very low temperatures. In 1877, Louis Paul Cailletet in France and Raoul Pictet in Switzerland succeeded in producing the first droplets of liquid air . This was followed in 1883 by the production of liquid oxygen by the Polish professors Zygmunt Wróblewski and Karol Olszewski. Scottish chemist and physicist James Dewar and Dutch physicist Heike Kamerlingh Onnes took on the challenge to liquefy the remaining gases, hydrogen and helium. In 1898, after 20 years of effort, Dewar was first to liquefy hydrogen, reaching a new low-temperature record of . However, Kamerlingh Onnes, his rival, was the first to liquefy helium, in 1908, using several precooling stages and the Hampson–Linde cycle. He lowered the temperature to the boiling point of helium . By reducing the pressure of the liquid helium he achieved an even lower temperature, near 1.5 K. These were the coldest temperatures achieved on Earth at the time and his achievement earned him the Nobel Prize in 1913. Kamerlingh Onnes would continue to study the properties of materials at temperatures near absolute zero, describing superconductivity and superfluids for the first time. Very low temperatures The average temperature of the universe today is approximately , or about -270.42 degrees celsius, based on measurements of cosmic microwave background radiation. Absolute zero cannot be achieved, although it is possible to reach temperatures close to it through the use of cryocoolers, dilution refrigerators, and nuclear adiabatic demagnetization. The use of laser cooling has produced temperatures of less than a billionth of a kelvin. At very low temperatures in the vicinity of absolute zero, matter exhibits many unusual properties, including superconductivity, superfluidity, and Bose–Einstein condensation. To study such phenomena, scientists have worked to obtain even lower temperatures. In November 2000, nuclear spin temperatures below 100 pK were reported for an experiment at the Helsinki University of Technology's Low Temperature Lab in Espoo, Finland. However, this was the temperature of one particular degree of freedom—a quantum property called nuclear spin—not the overall average thermodynamic temperature for all possible degrees in freedom. In February 2003, the Boomerang Nebula was observed to have been releasing gases at a speed of for the last 1,500 years. This has cooled it down to approximately 1 K, as deduced by astronomical observation, which is the lowest natural temperature ever recorded. In May 2005, the European Space Agency proposed research in space to achieve femtokelvin temperatures. In May 2006, the Institute of Quantum Optics at the University of Hannover gave details of technologies and benefits of femtokelvin research in space. In January 2013, physicist Ulrich Schneider of the University of Munich in Germany reported to have achieved temperatures formally below absolute zero ("negative temperature") in gases. The gas is artificially forced out of equilibrium into a high potential energy state, which is, however, cold. When it then emits radiation it approaches the equilibrium, and can continue emitting despite reaching formal absolute zero; thus, the temperature is formally negative. In September 2014, scientists in the CUORE collaboration at the Laboratori Nazionali del Gran Sasso in Italy cooled a copper vessel with a volume of one cubic meter to for 15 days, setting a record for the lowest temperature in the known universe over such a large contiguous volume. In June 2015, experimental physicists at MIT cooled molecules in a gas of sodium potassium to a temperature of 500 nanokelvin, and it is expected to exhibit an exotic state of matter by cooling these molecules somewhat further. In 2017, Cold Atom Laboratory (CAL), an experimental instrument was developed for launch to the International Space Station (ISS) in 2018. The instrument has created extremely cold conditions in the microgravity environment of the ISS leading to the formation of Bose–Einstein condensates. In this space-based laboratory, temperatures as low as 1 picokelvin ( K) temperatures are projected to be achievable, and it could further the exploration of unknown quantum mechanical phenomena and test some of the most fundamental laws of physics. The current world record for effective temperatures was set in 2021 at 38 picokelvin (pK), or 0.000000000038 of a kelvin, through matter-wave lensing of rubidium Bose–Einstein condensates. See also Charles's law Heat International Temperature Scale of 1990 Orders of magnitude (temperature) Thermodynamic temperature Triple point Ultracold atom Kinetic energy Entropy References Further reading BIPM Mise en pratique - Kelvin - Appendix 2 - SI Brochure External links "Absolute zero": a two part NOVA episode originally aired January 2008 "What is absolute zero?" Lansing State Journal Cold Cryogenics Temperature

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1419

https://en.wikipedia.org/wiki/Adiabatic%20process

Adiabatic process

In thermodynamics, an adiabatic process (Greek: adiábatos, "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work. As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings. In meteorology and oceanography, adiabatic cooling produces condensation of moisture or salinity, oversaturating the parcel. Therefore, the excess must be removed. There, the process becomes a pseudo-adiabatic process whereby the liquid water or salt that condenses is assumed to be removed upon formation by idealized instantaneous precipitation. The pseudoadiabatic process is only defined for expansion because a compressed parcel becomes warmer and remains undersaturated. Description A process without transfer of heat to or from a system, so that , is called adiabatic, and such a system is said to be adiabatically isolated. The assumption that a process is adiabatic is a frequently made simplifying assumption. For example, the compression of a gas within a cylinder of an engine is assumed to occur so rapidly that on the time scale of the compression process, little of the system's energy can be transferred out as heat to the surroundings. Even though the cylinders are not insulated and are quite conductive, that process is idealized to be adiabatic. The same can be said to be true for the expansion process of such a system. The assumption of adiabatic isolation is useful and often combined with other such idealizations to calculate a good first approximation of a system's behaviour. For example, according to Laplace, when sound travels in a gas, there is no time for heat conduction in the medium, and so the propagation of sound is adiabatic. For such an adiabatic process, the modulus of elasticity (Young's modulus) can be expressed as , where is the ratio of specific heats at constant pressure and at constant volume ( ) and is the pressure of the gas. Various applications of the adiabatic assumption For a closed system, one may write the first law of thermodynamics as : , where denotes the change of the system's internal energy, the quantity of energy added to it as heat, and the work done by the system on its surroundings. If the system has such rigid walls that work cannot be transferred in or out (), and the walls are not adiabatic and energy is added in the form of heat (), and there is no phase change, then the temperature of the system will rise. If the system has such rigid walls that pressure–volume work cannot be done, but the walls are adiabatic (), and energy is added as isochoric (constant volume) work in the form of friction or the stirring of a viscous fluid within the system (), and there is no phase change, then the temperature of the system will rise. If the system walls are adiabatic () but not rigid (), and, in a fictive idealized process, energy is added to the system in the form of frictionless, non-viscous pressure–volume work (), and there is no phase change, then the temperature of the system will rise. Such a process is called an isentropic process and is said to be "reversible". Ideally, if the process were reversed the energy could be recovered entirely as work done by the system. If the system contains a compressible gas and is reduced in volume, the uncertainty of the position of the gas is reduced, and seemingly would reduce the entropy of the system, but the temperature of the system will rise as the process is isentropic (). Should the work be added in such a way that friction or viscous forces are operating within the system, then the process is not isentropic, and if there is no phase change, then the temperature of the system will rise, the process is said to be "irreversible", and the work added to the system is not entirely recoverable in the form of work. If the walls of a system are not adiabatic, and energy is transferred in as heat, entropy is transferred into the system with the heat. Such a process is neither adiabatic nor isentropic, having , and according to the second law of thermodynamics. Naturally occurring adiabatic processes are irreversible (entropy is produced). The transfer of energy as work into an adiabatically isolated system can be imagined as being of two idealized extreme kinds. In one such kind, no entropy is produced within the system (no friction, viscous dissipation, etc.), and the work is only pressure-volume work (denoted by ). In nature, this ideal kind occurs only approximately because it demands an infinitely slow process and no sources of dissipation. The other extreme kind of work is isochoric work (), for which energy is added as work solely through friction or viscous dissipation within the system. A stirrer that transfers energy to a viscous fluid of an adiabatically isolated system with rigid walls, without phase change, will cause a rise in temperature of the fluid, but that work is not recoverable. Isochoric work is irreversible. The second law of thermodynamics observes that a natural process, of transfer of energy as work, always consists at least of isochoric work and often both of these extreme kinds of work. Every natural process, adiabatic or not, is irreversible, with , as friction or viscosity are always present to some extent. Adiabatic heating and cooling The adiabatic compression of a gas causes a rise in temperature of the gas. Adiabatic expansion against pressure, or a spring, causes a drop in temperature. In contrast, free expansion is an isothermal process for an ideal gas. Adiabatic heating occurs when the pressure of a gas is increased by work done on it by its surroundings, e.g., a piston compressing a gas contained within a cylinder and raising the temperature where in many practical situations heat conduction through walls can be slow compared with the compression time. This finds practical application in diesel engines which rely on the lack of heat dissipation during the compression stroke to elevate the fuel vapor temperature sufficiently to ignite it. Adiabatic heating occurs in the Earth's atmosphere when an air mass descends, for example, in a katabatic wind, Foehn wind, or chinook wind flowing downhill over a mountain range. When a parcel of air descends, the pressure on the parcel increases. Because of this increase in pressure, the parcel's volume decreases and its temperature increases as work is done on the parcel of air, thus increasing its internal energy, which manifests itself by a rise in the temperature of that mass of air. The parcel of air can only slowly dissipate the energy by conduction or radiation (heat), and to a first approximation it can be considered adiabatically isolated and the process an adiabatic process. Adiabatic cooling occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand, thus causing it to do work on its surroundings. When the pressure applied on a parcel of gas is reduced, the gas in the parcel is allowed to expand; as the volume increases, the temperature falls as its internal energy decreases. Adiabatic cooling occurs in the Earth's atmosphere with orographic lifting and lee waves, and this can form pileus or lenticular clouds. Snowfall in a hot desert is one of such contradictory phenomenon to be seen, but snow has been recorded several times in the Sahara Desert over the last decades, most recently in January 2022. Adiabatic cooling does not have to involve a fluid. One technique used to reach very low temperatures (thousandths and even millionths of a degree above absolute zero) is via adiabatic demagnetisation, where the change in magnetic field on a magnetic material is used to provide adiabatic cooling. Also, the contents of an expanding universe can be described (to first order) as an adiabatically cooling fluid. (See heat death of the universe.) Rising magma also undergoes adiabatic cooling before eruption, particularly significant in the case of magmas that rise quickly from great depths such as kimberlites. In the Earth's convecting mantle (the asthenosphere) beneath the lithosphere, the mantle temperature is approximately an adiabat. The slight decrease in temperature with shallowing depth is due to the decrease in pressure the shallower the material is in the Earth. Such temperature changes can be quantified using the ideal gas law, or the hydrostatic equation for atmospheric processes. In practice, no process is truly adiabatic. Many processes rely on a large difference in time scales of the process of interest and the rate of heat dissipation across a system boundary, and thus are approximated by using an adiabatic assumption. There is always some heat loss, as no perfect insulators exist. Ideal gas (reversible process) The mathematical equation for an ideal gas undergoing a reversible (i.e., no entropy generation) adiabatic process can be represented by the polytropic process equation where is pressure, is volume, and for this case , where being the specific heat for constant pressure, being the specific heat for constant volume, is the adiabatic index, and is the number of degrees of freedom (3 for monatomic gas, 5 for diatomic gas and collinear molecules e.g. carbon dioxide). For a monatomic ideal gas, , and for a diatomic gas (such as nitrogen and oxygen, the main components of air), . Note that the above formula is only applicable to classical ideal gases and not Bose–Einstein or Fermi gases. For reversible adiabatic processes, it is also true that where T is an absolute temperature. This can also be written as Example of adiabatic compression The compression stroke in a gasoline engine can be used as an example of adiabatic compression. The model assumptions are: the uncompressed volume of the cylinder is one litre (1 L = 1000 cm3 = 0.001 m3); the gas within is the air consisting of molecular nitrogen and oxygen only (thus a diatomic gas with 5 degrees of freedom, and so ); the compression ratio of the engine is 10:1 (that is, the 1 L volume of uncompressed gas is reduced to 0.1 L by the piston); and the uncompressed gas is at approximately room temperature and pressure (a warm room temperature of ~27 °C, or 300 K, and a pressure of 1 bar = 100 kPa, i.e. typical sea-level atmospheric pressure). so the adiabatic constant for this example is about 6.31 Pa m4.2. The gas is now compressed to a 0.1 L (0.0001 m3) volume, which we assume happens quickly enough that no heat enters or leaves the gas through the walls. The adiabatic constant remains the same, but with the resulting pressure unknown We can now solve for the final pressure or 25.1 bar. This pressure increase is more than a simple 10:1 compression ratio would indicate; this is because the gas is not only compressed, but the work done to compress the gas also increases its internal energy, which manifests itself by a rise in the gas temperature and an additional rise in pressure above what would result from a simplistic calculation of 10 times the original pressure. We can solve for the temperature of the compressed gas in the engine cylinder as well, using the ideal gas law, PV = nRT (n is amount of gas in moles and R the gas constant for that gas). Our initial conditions being 100 kPa of pressure, 1 L volume, and 300 K of temperature, our experimental constant (nR) is: We know the compressed gas has  = 0.1 L and  = , so we can solve for temperature: That is a final temperature of 753 K, or 479 °C, or 896 °F, well above the ignition point of many fuels. This is why a high-compression engine requires fuels specially formulated to not self-ignite (which would cause engine knocking when operated under these conditions of temperature and pressure), or that a supercharger with an intercooler to provide a pressure boost but with a lower temperature rise would be advantageous. A diesel engine operates under even more extreme conditions, with compression ratios of 16:1 or more being typical, in order to provide a very high gas temperature, which ensures immediate ignition of the injected fuel. Adiabatic free expansion of a gas For an adiabatic free expansion of an ideal gas, the gas is contained in an insulated container and then allowed to expand in a vacuum. Because there is no external pressure for the gas to expand against, the work done by or on the system is zero. Since this process does not involve any heat transfer or work, the first law of thermodynamics then implies that the net internal energy change of the system is zero. For an ideal gas, the temperature remains constant because the internal energy only depends on temperature in that case. Since at constant temperature, the entropy is proportional to the volume, the entropy increases in this case, therefore this process is irreversible. Derivation of P–V relation for adiabatic heating and cooling The definition of an adiabatic process is that heat transfer to the system is zero, . Then, according to the first law of thermodynamics, where is the change in the internal energy of the system and is work done by the system. Any work () done must be done at the expense of internal energy , since no heat is being supplied from the surroundings. Pressure–volume work done by the system is defined as However, does not remain constant during an adiabatic process but instead changes along with . It is desired to know how the values of and relate to each other as the adiabatic process proceeds. For an ideal gas (recall ideal gas law ) the internal energy is given by where is the number of degrees of freedom divided by 2, is the universal gas constant and is the number of moles in the system (a constant). Differentiating equation (a3) yields Equation (a4) is often expressed as because . Now substitute equations (a2) and (a4) into equation (a1) to obtain factorize : and divide both sides by : After integrating the left and right sides from to and from to and changing the sides respectively, Exponentiate both sides, substitute with , the heat capacity ratio and eliminate the negative sign to obtain Therefore, and At the same time, the work done by the pressure–volume changes as a result from this process, is equal to Since we require the process to be adiabatic, the following equation needs to be true By the previous derivation, Rearranging (b4) gives Substituting this into (b2) gives Integrating we obtain the expression for work, Substituting in second term, Rearranging, Using the ideal gas law and assuming a constant molar quantity (as often happens in practical cases), By the continuous formula, or Substituting into the previous expression for , Substituting this expression and (b1) in (b3) gives Simplifying, Derivation of discrete formula and work expression The change in internal energy of a system, measured from state 1 to state 2, is equal to At the same time, the work done by the pressure–volume changes as a result from this process, is equal to Since we require the process to be adiabatic, the following equation needs to be true By the previous derivation, Rearranging (c4) gives Substituting this into (c2) gives Integrating we obtain the expression for work, Substituting in second term, Rearranging, Using the ideal gas law and assuming a constant molar quantity (as often happens in practical cases), By the continuous formula, or Substituting into the previous expression for , Substituting this expression and (c1) in (c3) gives Simplifying, Graphing adiabats An adiabat is a curve of constant entropy in a diagram. Some properties of adiabats on a P–V diagram are indicated. These properties may be read from the classical behaviour of ideal gases, except in the region where PV becomes small (low temperature), where quantum effects become important. Every adiabat asymptotically approaches both the V axis and the P axis (just like isotherms). Each adiabat intersects each isotherm exactly once. An adiabat looks similar to an isotherm, except that during an expansion, an adiabat loses more pressure than an isotherm, so it has a steeper inclination (more vertical). If isotherms are concave towards the north-east direction (45°), then adiabats are concave towards the east north-east (31°). If adiabats and isotherms are graphed at regular intervals of entropy and temperature, respectively (like altitude on a contour map), then as the eye moves towards the axes (towards the south-west), it sees the density of isotherms stay constant, but it sees the density of adiabats grow. The exception is very near absolute zero, where the density of adiabats drops sharply and they become rare (see Nernst's theorem). The right diagram is a P–V diagram with a superposition of adiabats and isotherms: The isotherms are the red curves and the adiabats are the black curves. The adiabats are isentropic. Volume is the horizontal axis and pressure is the vertical axis. Etymology The term adiabatic () is an anglicization of the Greek term ἀδιάβατος "impassable" (used by Xenophon of rivers). It is used in the thermodynamic sense by Rankine (1866), and adopted by Maxwell in 1871 (explicitly attributing the term to Rankine). The etymological origin corresponds here to an impossibility of transfer of energy as heat and of transfer of matter across the wall. The Greek word ἀδιάβατος is formed from privative ἀ- ("not") and διαβατός, "passable", in turn deriving from διά ("through"), and βαῖνειν ("to walk, go, come"). Conceptual significance in thermodynamic theory The adiabatic process has been important for thermodynamics since its early days. It was important in the work of Joule because it provided a way of nearly directly relating quantities of heat and work. Energy can enter or leave a thermodynamic system enclosed by walls that prevent mass transfer only as heat or work. Therefore, a quantity of work in such a system can be related almost directly to an equivalent quantity of heat in a cycle of two limbs. The first limb is an isochoric adiabatic work process increasing the system's internal energy; the second, an isochoric and workless heat transfer returning the system to its original state. Accordingly, Rankine measured quantity of heat in units of work, rather than as a calorimetric quantity . In 1854, Rankine used a quantity that he called "the thermodynamic function" that later was called entropy, and at that time he wrote also of the "curve of no transmission of heat", which he later called an adiabatic curve. Besides its two isothermal limbs, Carnot's cycle has two adiabatic limbs. For the foundations of thermodynamics, the conceptual importance of this was emphasized by Bryan, by Carathéodory, and by Born. The reason is that calorimetry presupposes a type of temperature as already defined before the statement of the first law of thermodynamics, such as one based on empirical scales. Such a presupposition involves making the distinction between empirical temperature and absolute temperature. Rather, the definition of absolute thermodynamic temperature is best left till the second law is available as a conceptual basis. In the eighteenth century, the law of conservation of energy was not yet fully formulated or established, and the nature of heat was debated. One approach to these problems was to regard heat, measured by calorimetry, as a primary substance that is conserved in quantity. By the middle of the nineteenth century, it was recognized as a form of energy, and the law of conservation of energy was thereby also recognized. The view that eventually established itself, and is currently regarded as right, is that the law of conservation of energy is a primary axiom, and that heat is to be analyzed as consequential. In this light, heat cannot be a component of the total energy of a single body because it is not a state variable but, rather, a variable that describes a transfer between two bodies. The adiabatic process is important because it is a logical ingredient of this current view. Divergent usages of the word adiabatic This present article is written from the viewpoint of macroscopic thermodynamics, and the word adiabatic is used in this article in the traditional way of thermodynamics, introduced by Rankine. It is pointed out in the present article that, for example, if a compression of a gas is rapid, then there is little time for heat transfer to occur, even when the gas is not adiabatically isolated by a definite wall. In this sense, a rapid compression of a gas is sometimes approximately or loosely said to be adiabatic, though often far from isentropic, even when the gas is not adiabatically isolated by a definite wall. Quantum mechanics and quantum statistical mechanics, however, use the word adiabatic in a very different sense, one that can at times seem almost opposite to the classical thermodynamic sense. In quantum theory, the word adiabatic can mean something perhaps near isentropic, or perhaps near quasi-static, but the usage of the word is very different between the two disciplines. On the one hand, in quantum theory, if a perturbative element of compressive work is done almost infinitely slowly (that is to say quasi-statically), it is said to have been done adiabatically. The idea is that the shapes of the eigenfunctions change slowly and continuously, so that no quantum jump is triggered, and the change is virtually reversible. While the occupation numbers are unchanged, nevertheless there is change in the energy levels of one-to-one corresponding, pre- and post-compression, eigenstates. Thus a perturbative element of work has been done without heat transfer and without introduction of random change within the system. For example, Max Born writes "Actually, it is usually the 'adiabatic' case with which we have to do: i.e. the limiting case where the external force (or the reaction of the parts of the system on each other) acts very slowly. In this case, to a very high approximation that is, there is no probability for a transition, and the system is in the initial state after cessation of the perturbation. Such a slow perturbation is therefore reversible, as it is classically." On the other hand, in quantum theory, if a perturbative element of compressive work is done rapidly, it randomly changes the occupation numbers of the eigenstates, as well as changing their shapes. In that theory, such a rapid change is said not to be adiabatic, and the contrary word diabatic is applied to it. One might guess that perhaps Clausius, if he were confronted with this, in the now-obsolete language he used in his day, would have said that "internal work" was done and that 'heat was generated though not transferred'. Furthermore, in atmospheric thermodynamics, a diabatic process is one in which heat is exchanged. In classical thermodynamics, such a rapid change would still be called adiabatic because the system is adiabatically isolated, and there is no transfer of energy as heat. The strong irreversibility of the change, due to viscosity or other entropy production, does not impinge on this classical usage. Thus for a mass of gas, in macroscopic thermodynamics, words are so used that a compression is sometimes loosely or approximately said to be adiabatic if it is rapid enough to avoid heat transfer, even if the system is not adiabatically isolated. But in quantum statistical theory, a compression is not called adiabatic if it is rapid, even if the system is adiabatically isolated in the classical thermodynamic sense of the term. The words are used differently in the two disciplines, as stated just above. See also Fire piston Heat burst Related physics topics First law of thermodynamics Entropy (classical thermodynamics) Adiabatic conductivity Adiabatic lapse rate Total air temperature Magnetic refrigeration Related thermodynamic processes Cyclic process Isobaric process Isenthalpic process Isentropic process Isochoric process Isothermal process Polytropic process Quasistatic process References General Broholm, Collin. "Adiabatic free expansion". Physics & Astronomy @ Johns Hopkins University. N.p., 26 Nov. 1997. Web. 14 Apr. Nave, Carl Rod. "Adiabatic Processes". HyperPhysics. N.p., n.d. Web. 14 Apr. 2011. . Thorngren, Dr. Jane R.. "Adiabatic Processes". Daphne – A Palomar College Web Server. N.p., 21 July 1995. Web. 14 Apr. 2011. . External links Article in HyperPhysics Encyclopaedia Thermodynamic processes Atmospheric thermodynamics Entropy

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1449

https://en.wikipedia.org/wiki/Alan%20Kay

Alan Kay

Alan Curtis Kay (born May 17, 1940) is an American computer scientist. He has been elected a Fellow of the American Academy of Arts and Sciences, the National Academy of Engineering, and the Royal Society of Arts. He is best known for his pioneering work on object-oriented programming and windowing graphical user interface (GUI) design. He was awarded the Turing award in 2003. He was the president of the Viewpoints Research Institute before its closure in 2018, and an adjunct professor of computer science at the University of California, Los Angeles. He is also on the advisory board of TTI/Vanguard. Until mid-2005, he was a senior fellow at HP Labs, a visiting professor at Kyoto University, and an adjunct professor at the Massachusetts Institute of Technology (MIT). Kay is also a former professional jazz guitarist, composer, and theatrical designer. He also is an amateur classical pipe organist. Early life and work In an interview on education in America with the Davis Group Ltd., Kay said: Originally from Springfield, Massachusetts, Kay's family relocated several times due to his father's career in physiology before ultimately settling in the New York metropolitan area when he was nine. He attended Brooklyn Technical High School. Having accumulated enough credits to graduate, Kay then attended Bethany College in Bethany, West Virginia. He majored in biology and minored in mathematics. Thereafter, Kay taught guitar in Denver, Colorado for a year and hastily enlisted in the United States Air Force when the local draft board inquired about his nonstudent status. Assigned as a computer programmer (a rare billet usually filled by women due to the secretarial connotations of the field in the era) after passing an aptitude test, he devised an early cross-platform file transfer system. Following his discharge, Kay enrolled at the University of Colorado Boulder, earning a Bachelor of Science (B.S.) in mathematics and molecular biology in 1966. In the autumn of 1966, he began graduate school at the University of Utah College of Engineering. He earned a Master of Science (M.S.) in electrical engineering in 1968, and then a Doctor of Philosophy (Ph.D.) in computer science in 1969. His doctoral dissertation, FLEX: A Flexible Extendable Language, described the invention of a computer language named FLEX. While there, he worked with "fathers of computer graphics" David C. Evans (who had been recently recruited from the University of California, Berkeley to start Utah's computer science department) and Ivan Sutherland (best known for writing such pioneering programs as Sketchpad). Their mentorship greatly inspired Kay's evolving views on objects and programming. As he grew busier with research for the Defense Advanced Research Projects Agency (DARPA), he ended his musical career. In 1968, he met Seymour Papert and learned of the programming language Logo, a dialect of Lisp optimized for educational purposes. This led him to learn of the work of Jean Piaget, Jerome Bruner, Lev Vygotsky, and of constructionist learning, further influencing his professional orientation. Leaving Utah as an associate professor of computer science in 1969, Kay became a visiting researcher at the Stanford Artificial Intelligence Laboratory in anticipation of accepting a professorship at Carnegie Mellon University. Instead, in 1970, he joined the Xerox PARC research staff in Palo Alto, California. Throughout the decade, he developed prototypes of networked workstations using the programming language Smalltalk. These inventions were later commercialized by Apple in their Lisa and Macintosh computers. Along with some colleagues at PARC, Kay is one of the fathers of the idea of object-oriented programming (OOP), which he named. Some of the original object-oriented concepts, including the use of the words 'object' and 'class', had been developed for Simula 67 at the Norwegian Computing Center. Later he said: I'm sorry that I long ago coined the term "objects" for this topic because it gets many people to focus on the lesser idea. The big idea is "messaging". While at PARC, Kay conceived the Dynabook concept, a key progenitor of laptop and tablet computers and the e-book. He is also the architect of the modern overlapping windowing graphical user interface (GUI). Because the Dynabook was conceived as an educational platform, Kay is considered to be one of the first researchers into mobile learning; many features of the Dynabook concept have been adopted in the design of the One Laptop Per Child educational platform, with which Kay is actively involved. Recognition and recent work From 1981 to 1984, Kay was the chief scientist at Atari. In 1984, he became an Apple Fellow. Following the closure of the Apple Advanced Technology Group in 1997, he was recruited by his friend Bran Ferren, head of research and development at Disney, to join Walt Disney Imagineering as a Disney Fellow. He remained there until Ferren left to start Applied Minds Inc with Imagineer Danny Hillis, leading to the cessation of the Fellows program. In 2001, he founded Viewpoints Research Institute, a nonprofit organization dedicated to children, learning, and advanced software development. For its first ten years, Kay and his Viewpoints group were based at Applied Minds in Glendale, California, where he and Ferren continued to work together on various projects. Kay was also a senior fellow at Hewlett-Packard until HP disbanded the Advanced Software Research Team on July 20, 2005. Squeak, Etoys, and Croquet In December 1995, while still at Apple, Kay collaborated with many others to start the open source Squeak version of Smalltalk, and he continues to work on it. As part of this effort, in November 1996, his team began research on what became the Etoys system. More recently he started, along with David A. Smith, David P. Reed, Andreas Raab, Rick McGeer, Julian Lombardi, and Mark McCahill, the Croquet Project, an open source networked 2-D and 3-D environment for collaborative work. Tweak In 2001, it became clear that the Etoy architecture in Squeak had reached its limits in what the Morphic interface infrastructure could do. Andreas Raab was a researcher working in Kay's group, then at Hewlett-Packard. He proposed defining a "script process" and providing a default scheduling mechanism that avoids several more general problems. The result was a new user interface, proposed to replace the Squeak Morphic user interface in the future. Tweak added mechanisms of islands, asynchronous messaging, players and costumes, language extensions, projects, and tile scripting. Its underlying object system is class-based, but to users (during programming) it acts as if it were prototype-based. Tweak objects are created and run in Tweak project windows. Children's machine In November 2005, at the World Summit on the Information Society, the MIT research laboratories unveiled a new laptop computer, for educational use around the world. It has many names: the $100 Laptop, the One Laptop per Child program, the Children's Machine, and the XO-1. The program was begun and is sustained by Kay's friend Nicholas Negroponte, and is based on Kay's Dynabook ideal. Kay is a prominent co-developer of the computer, focusing on its educational software using Squeak and Etoys. Reinventing programming Kay has lectured extensively on the idea that the computer revolution is very new, and all of the good ideas have not been implemented universally. Lectures at OOPSLA 1997 conference and his ACM Turing award talk, entitled "The Computer Revolution Hasn't Happened Yet" were informed by his experiences with Sketchpad, Simula, Smalltalk, and the bloated code of commercial software. On August 31, 2006, Kay's proposal to the United States National Science Foundation (NSF) was granted, thus funding Viewpoints Research Institute for several years. The proposal title was: STEPS Toward the Reinvention of Programming: A compact and Practical Model of Personal Computing as a Self-exploratorium. A sense of what Kay is trying to do comes from this quote, from the abstract of a seminar on this, given at Intel Research Labs, Berkeley: "The conglomeration of commercial and most open source software consumes in the neighborhood of several hundreds of millions of lines of code these days. We wonder: how small could be an understandable practical "Model T" design that covers this functionality? 1M lines of code? 200K LOC? 100K LOC? 20K LOC?" Awards and honors Alan Kay has received many awards and honors. Among them: 2001: UdK 01-Award in Berlin, Germany for pioneering the GUI; J-D Warnier Prix D'Informatique; NEC C&C Prize 2002: Telluride Tech Festival Award of Technology in Telluride, Colorado 2003: ACM Turing Award "For pioneering many of the ideas at the root of contemporary object-oriented programming languages, leading the team that developed Smalltalk, and for fundamental contributions to personal computing." 2004: Kyoto Prize; Charles Stark Draper Prize with Butler W. Lampson, Robert W. Taylor and Charles P. Thacker 2012: UPE Abacus Award awarded to individuals who have provided extensive support and leadership for student-related activities in the computing and information disciplines, Honorary doctorates: 2002: Kungliga Tekniska Högskolan (Royal Institute of Technology) in Stockholm 2005: Georgia Institute of Technology 2005: Columbia College Chicago awarded Doctor of Humane Letters, Honoris Causa 2007: Laurea Honoris Causa in Informatica, Università di Pisa, Italy 2008: University of Waterloo 2009: Kyoto University 2010: Universidad de Murcia 2017: University of Edinburgh Honorary Professor, Berlin University of the Arts Elected fellow of: American Academy of Arts and Sciences 1997: National Academy of Engineering for inventing the concept of portable personal computing. Royal Society of Arts 1999: Computer History Museum "for his fundamental contributions to personal computing and human-computer interface development." 2008: Association for Computing Machinery "For fundamental contributions to personal computing and object-oriented programming." 2011: Hasso Plattner Institute His other honors include the J-D Warnier Prix d'Informatique, the ACM Systems Software Award, the NEC Computers & Communication Foundation Prize, the Funai Foundation Prize, the Lewis Branscomb Technology Award, and the ACM SIGCSE Award for Outstanding Contributions to Computer Science Education. See also List of pioneers in computer science References External links Viewpoints Research Institute "There is no information content in Alan Kay" 2012 1940 births American computer programmers American computer scientists Apple Inc. employees Apple Fellows Atari people Computer science educators Draper Prize winners Fellows of the American Association for the Advancement of Science Fellows of the Association for Computing Machinery Hewlett-Packard people Human–computer interaction researchers Living people Massachusetts Institute of Technology faculty Open source advocates People from Springfield, Massachusetts Programming language designers Scientists at PARC (company) Turing Award laureates University of California, Los Angeles faculty University of Colorado Boulder alumni University of Utah alumni

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1451

https://en.wikipedia.org/wiki/APL%20%28programming%20language%29

APL (programming language)

APL (named after the book A Programming Language) is a programming language developed in the 1960s by Kenneth E. Iverson. Its central datatype is the multidimensional array. It uses a large range of special graphic symbols to represent most functions and operators, leading to very concise code. It has been an important influence on the development of concept modeling, spreadsheets, functional programming, and computer math packages. It has also inspired several other programming languages. History Mathematical notation A mathematical notation for manipulating arrays was developed by Kenneth E. Iverson, starting in 1957 at Harvard University. In 1960, he began work for IBM where he developed this notation with Adin Falkoff and published it in his book A Programming Language in 1962. The preface states its premise: This notation was used inside IBM for short research reports on computer systems, such as the Burroughs B5000 and its stack mechanism when stack machines versus register machines were being evaluated by IBM for upcoming computers. Iverson also used his notation in a draft of the chapter A Programming Language, written for a book he was writing with Fred Brooks, Automatic Data Processing, which would be published in 1963. In 1979, Iverson received the Turing Award for his work on APL. Development into a computer programming language As early as 1962, the first attempt to use the notation to describe a complete computer system happened after Falkoff discussed with William C. Carter his work to standardize the instruction set for the machines that later became the IBM System/360 family. In 1963, Herbert Hellerman, working at the IBM Systems Research Institute, implemented a part of the notation on an IBM 1620 computer, and it was used by students in a special high school course on calculating transcendental functions by series summation. Students tested their code in Hellerman's lab. This implementation of a part of the notation was called Personalized Array Translator (PAT). In 1963, Falkoff, Iverson, and Edward H. Sussenguth Jr., all working at IBM, used the notation for a formal description of the IBM System/360 series machine architecture and functionality, which resulted in a paper published in IBM Systems Journal in 1964. After this was published, the team turned their attention to an implementation of the notation on a computer system. One of the motivations for this focus of implementation was the interest of John L. Lawrence who had new duties with Science Research Associates, an educational company bought by IBM in 1964. Lawrence asked Iverson and his group to help use the language as a tool to develop and use computers in education. After Lawrence M. Breed and Philip S. Abrams of Stanford University joined the team at IBM Research, they continued their prior work on an implementation programmed in FORTRAN IV for a part of the notation which had been done for the IBM 7090 computer running on the IBSYS operating system. This work was finished in late 1965 and later named IVSYS (for Iverson system). The basis of this implementation was described in detail by Abrams in a Stanford University Technical Report, "An Interpreter for Iverson Notation" in 1966, the academic aspect of this was formally supervised by Niklaus Wirth. Like Hellerman's PAT system earlier, this implementation did not include the APL character set but used special English reserved words for functions and operators. The system was later adapted for a time-sharing system and, by November 1966, it had been reprogrammed for the IBM System/360 Model 50 computer running in a time-sharing mode and was used internally at IBM. Hardware A key development in the ability to use APL effectively, before the wide use of cathode ray tube (CRT) terminals, was the development of a special IBM Selectric typewriter interchangeable typing element with all the special APL characters on it. This was used on paper printing terminal workstations using the Selectric typewriter and typing element mechanism, such as the IBM 1050 and IBM 2741 terminal. Keycaps could be placed over the normal keys to show which APL characters would be entered and typed when that key was struck. For the first time, a programmer could type in and see proper APL characters as used in Iverson's notation and not be forced to use awkward English keyword representations of them. Falkoff and Iverson had the special APL Selectric typing elements, 987 and 988, designed in late 1964, although no APL computer system was available to use them. Iverson cited Falkoff as the inspiration for the idea of using an IBM Selectric typing element for the APL character set. Many APL symbols, even with the APL characters on the Selectric typing element, still had to be typed in by over-striking two extant element characters. An example is the grade up character, which had to be made from a delta (shift-H) and a Sheffer stroke (shift-M). This was necessary because the APL character set was much larger than the 88 characters allowed on the typing element, even when letters were restricted to upper-case (capitals). Commercial availability The first APL interactive login and creation of an APL workspace was in 1966 by Larry Breed using an IBM 1050 terminal at the IBM Mohansic Labs near Thomas J. Watson Research Center, the home of APL, in Yorktown Heights, New York. IBM was chiefly responsible for introducing APL to the marketplace. The first publicly available version of APL was released in 1968 for the IBM 1130. IBM provided APL\1130 for free but without liability or support. It would run in as little as 8k 16-bit words of memory, and used a dedicated 1 megabyte hard disk. APL gained its foothold on mainframe timesharing systems from the late 1960s through the early 1980s, in part because it would support multiple users on lower-specification systems that had no dynamic address translation hardware. Additional improvements in performance for selected IBM System/370 mainframe systems included the APL Assist Microcode in which some support for APL execution was included in the processor's firmware, as distinct from being implemented entirely by higher-level software. Somewhat later, as suitably performing hardware was finally growing available in the mid- to late-1980s, many users migrated their applications to the personal computer environment. Early IBM APL interpreters for IBM 360 and IBM 370 hardware implemented their own multi-user management instead of relying on the host services, thus they were their own timesharing systems. First introduced for use at IBM in 1966, the APL\360 system was a multi-user interpreter. The ability to programmatically communicate with the operating system for information and setting interpreter system variables was done through special privileged "I-beam" functions, using both monadic and dyadic operations. In 1973, IBM released APL.SV, which was a continuation of the same product, but which offered shared variables as a means to access facilities outside of the APL system, such as operating system files. In the mid-1970s, the IBM mainframe interpreter was even adapted for use on the IBM 5100 desktop computer, which had a small CRT and an APL keyboard, when most other small computers of the time only offered BASIC. In the 1980s, the VSAPL program product enjoyed wide use with Conversational Monitor System (CMS), Time Sharing Option (TSO), VSPC, MUSIC/SP, and CICS users. In 1973–1974, Patrick E. Hagerty directed the implementation of the University of Maryland APL interpreter for the 1100 line of the Sperry UNIVAC 1100/2200 series mainframe computers. At the time, Sperry had nothing. In 1974, student Alan Stebbens was assigned the task of implementing an internal function. Xerox APL was available from June 1975 for Xerox 560 and Sigma 6, 7, and 9 mainframes running CP-V and for Honeywell CP-6. In the 1960s and 1970s, several timesharing firms arose that sold APL services using modified versions of the IBM APL\360 interpreter. In North America, the better-known ones were IP Sharp Associates, Scientific Time Sharing Corporation (STSC), Time Sharing Resources (TSR), and The Computer Company (TCC). CompuServe also entered the market in 1978 with an APL Interpreter based on a modified version of Digital Equipment Corp and Carnegie Mellon's, which ran on DEC's KI and KL 36-bit machines. CompuServe's APL was available both to its commercial market and the consumer information service. With the advent first of less expensive mainframes such as the IBM 4300, and later the personal computer, by the mid-1980s, the timesharing industry was all but gone. Sharp APL was available from IP Sharp Associates, first as a timesharing service in the 1960s, and later as a program product starting around 1979. Sharp APL was an advanced APL implementation with many language extensions, such as packages (the ability to put one or more objects into a single variable), file system, nested arrays, and shared variables. APL interpreters were available from other mainframe and mini-computer manufacturers also, notably Burroughs, Control Data Corporation (CDC), Data General, Digital Equipment Corporation (DEC), Harris, Hewlett-Packard (HP), Siemens, Xerox and others. Garth Foster of Syracuse University sponsored regular meetings of the APL implementers' community at Syracuse's Minnowbrook Conference Center in Blue Mountain Lake, New York. In later years, Eugene McDonnell organized similar meetings at the Asilomar Conference Grounds near Monterey, California, and at Pajaro Dunes near Watsonville, California. The SIGAPL special interest group of the Association for Computing Machinery continues to support the APL community. Microcomputers On microcomputers, which became available from the mid 1970s onwards, BASIC became the dominant programming language. Nevertheless, some microcomputers provided APL instead - the first being the Intel 8008-based MCM/70 which was released in 1974 and which was primarily used in education. Another machine of this time was the VideoBrain Family Computer, released in 1977, which was supplied with its dialect of APL called APL/S. The Commodore SuperPET, introduced in 1981, included an APL interpreter developed by the University of Waterloo. In 1976, Bill Gates claimed in his Open Letter to Hobbyists that Microsoft Corporation was implementing APL for the Intel 8080 and Motorola 6800 but had "very little incentive to make [it] available to hobbyists" because of software piracy. It was never released. APL2 Starting in the early 1980s, IBM APL development, under the leadership of Jim Brown, implemented a new version of the APL language that contained as its primary enhancement the concept of nested arrays, where an array can contain other arrays, and new language features which facilitated integrating nested arrays into program workflow. Ken Iverson, no longer in control of the development of the APL language, left IBM and joined I. P. Sharp Associates, where one of his major contributions was directing the evolution of Sharp APL to be more in accord with his vision. APL2 was first released for CMS and TSO in 1984. The APL2 Workstation edition (Windows, OS/2, AIX, Linux, and Solaris) followed later. As other vendors were busy developing APL interpreters for new hardware, notably Unix-based microcomputers, APL2 was almost always the standard chosen for new APL interpreter developments. Even today, most APL vendors or their users cite APL2 compatibility, as a selling point for those products. IBM cites its use for problem solving, system design, prototyping, engineering and scientific computations, expert systems, for teaching mathematics and other subjects, visualization and database access. Modern implementations Various implementations of APL by APLX, Dyalog, et al., include extensions for object-oriented programming, support for .NET Framework, XML-array conversion primitives, graphing, operating system interfaces, and lambda calculus expressions. Derivative languages APL has formed the basis of, or influenced, the following languages: A and A+, an alternative APL, the latter with graphical extensions. FP, a functional programming language. Ivy, an interpreter for an APL-like language developed by Rob Pike, and which uses ASCII as input. J, which was also designed by Iverson, and which uses ASCII with digraphs instead of special symbols. K, a proprietary variant of APL developed by Arthur Whitney. LYaPAS, a Soviet extension to APL. MATLAB, a numerical computation tool. Nial, a high-level array programming language with a functional programming notation. Polymorphic Programming Language, an interactive, extensible language with a similar base language. S, a statistical programming language (usually now seen in the open-source version known as R). Speakeasy, a numerical computing interactive environment. Wolfram Language, the programming language of Mathematica. Language characteristics Character set APL has been criticized and praised for its choice of a unique, non-standard character set. Some who learn it become ardent adherents. In the 1960s and 1970s, few terminal devices or even displays could reproduce the APL character set. The most popular ones employed the IBM Selectric print mechanism used with a special APL type element. One of the early APL line terminals (line-mode operation only, not full screen) was the Texas Instruments TI Model 745 (circa 1977) with the full APL character set which featured half and full duplex telecommunications modes, for interacting with an APL time-sharing service or remote mainframe to run a remote computer job, called an RJE. Over time, with the universal use of high-quality graphic displays, printing devices and Unicode support, the APL character font problem has largely been eliminated. However, entering APL characters requires the use of input method editors, keyboard mappings, virtual/on-screen APL symbol sets, or easy-reference printed keyboard cards which can frustrate beginners accustomed to other programming languages. With beginners who have no prior experience with other programming languages, a study involving high school students found that typing and using APL characters did not hinder the students in any measurable way. In defense of APL, it requires fewer characters to type, and keyboard mappings become memorized over time. Special APL keyboards are also made and in use today, as are freely downloadable fonts for operating systems such as Microsoft Windows. The reported productivity gains assume that one spends enough time working in the language to make it worthwhile to memorize the symbols, their semantics, and keyboard mappings, not to mention a substantial number of idioms for common tasks. Design Unlike traditionally structured programming languages, APL code is typically structured as chains of monadic or dyadic functions, and operators acting on arrays. APL has many nonstandard primitives (functions and operators) that are indicated by a single symbol or a combination of a few symbols. All primitives are defined to have the same precedence, and always associate to the right. Thus, APL is read or best understood from right-to-left. Early APL implementations (circa 1970 or so) had no programming loop-flow control structures, such as do or while loops, and if-then-else constructs. Instead, they used array operations, and use of structured programming constructs was often not necessary, since an operation could be performed on a full array in one statement. For example, the iota function (ι) can replace for-loop iteration: ιN when applied to a scalar positive integer yields a one-dimensional array (vector), 1 2 3 ... N. More recent implementations of APL generally include comprehensive control structures, so that data structure and program control flow can be clearly and cleanly separated. The APL environment is called a workspace. In a workspace the user can define programs and data, i.e., the data values exist also outside the programs, and the user can also manipulate the data without having to define a program. In the examples below, the APL interpreter first types six spaces before awaiting the user's input. Its own output starts in column one. The user can save the workspace with all values, programs, and execution status. APL uses a set of non-ASCII symbols, which are an extension of traditional arithmetic and algebraic notation. Having single character names for single instruction, multiple data (SIMD) vector functions is one way that APL enables compact formulation of algorithms for data transformation such as computing Conway's Game of Life in one line of code. In nearly all versions of APL, it is theoretically possible to express any computable function in one expression, that is, in one line of code. Because of the unusual character set, many programmers use special keyboards with APL keytops to write APL code. Although there are various ways to write APL code using only ASCII characters, in practice it is almost never done. (This may be thought to support Iverson's thesis about notation as a tool of thought.) Most if not all modern implementations use standard keyboard layouts, with special mappings or input method editors to access non-ASCII characters. Historically, the APL font has been distinctive, with uppercase italic alphabetic characters and upright numerals and symbols. Most vendors continue to display the APL character set in a custom font. Advocates of APL claim that the examples of so-called write-only code (badly written and almost incomprehensible code) are almost invariably examples of poor programming practice or novice mistakes, which can occur in any language. Advocates also claim that they are far more productive with APL than with more conventional computer languages, and that working software can be implemented in far less time and with far fewer programmers than using other technology. They also may claim that because it is compact and terse, APL lends itself well to larger-scale software development and complexity, because the number of lines of code can be reduced greatly. Many APL advocates and practitioners also view standard programming languages such as COBOL and Java as being comparatively tedious. APL is often found where time-to-market is important, such as with trading systems. Terminology APL makes a clear distinction between functions and operators. Functions take arrays (variables or constants or expressions) as arguments, and return arrays as results. Operators (similar to higher-order functions) take functions or arrays as arguments, and derive related functions. For example, the sum function is derived by applying the reduction operator to the addition function. Applying the same reduction operator to the maximum function (which returns the larger of two numbers) derives a function which returns the largest of a group (vector) of numbers. In the J language, Iverson substituted the terms verb for function and adverb or conjunction for operator. APL also identifies those features built into the language, and represented by a symbol, or a fixed combination of symbols, as primitives. Most primitives are either functions or operators. Coding APL is largely a process of writing non-primitive functions and (in some versions of APL) operators. However a few primitives are considered to be neither functions nor operators, most noticeably assignment. Some words used in APL literature have meanings that differ from those in both mathematics and the generality of computer science. Syntax APL has explicit representations of functions, operators, and syntax, thus providing a basis for the clear and explicit statement of extended facilities in the language, and tools to experiment on them. Examples Hello, world This displays "Hello, world": 'Hello, world'A design theme in APL is to define default actions in some cases that would produce syntax errors in most other programming languages. The 'Hello, world' string constant above displays, because display is the default action on any expression for which no action is specified explicitly (e.g. assignment, function parameter). Exponentiation Another example of this theme is that exponentiation in APL is written as , which indicates raising 2 to the power 3 (this would be written as in some other languages and in FORTRAN and Python). Many languages use to signify multiplication, as in , but APL chooses to use . However, if no base is specified (as with the statement in APL, or in other languages), most programming languages one would see this as a syntax error. APL, however, assumes the missing base to be the natural logarithm constant e, and interprets as . Simple statistics Suppose that is an array of numbers. Then gives its average. Reading right-to-left, gives the number of elements in X, and since is a dyadic operator, the term to its left is required as well. It is surrounded by parentheses since otherwise X would be taken (so that the summation would be of — each element of X divided by the number of elements in X), and gives the sum of the elements of X. Building on this, the following expression computes standard deviation: Naturally, one would define this expression as a function for repeated use rather than rewriting it each time. Further, since assignment is an operator, it can appear within an expression, so the following would place suitable values into T, AV and SD: Pick 6 lottery numbers This following immediate-mode expression generates a typical set of Pick 6 lottery numbers: six pseudo-random integers ranging from 1 to 40, guaranteed non-repeating, and displays them sorted in ascending order: x[⍋x←6?40] The above does a lot, concisely, although it may seem complex to a new APLer. It combines the following APL functions (also called primitives and glyphs): The first to be executed (APL executes from rightmost to leftmost) is dyadic function ? (named deal when dyadic) that returns a vector consisting of a select number (left argument: 6 in this case) of random integers ranging from 1 to a specified maximum (right argument: 40 in this case), which, if said maximum ≥ vector length, is guaranteed to be non-repeating; thus, generate/create 6 random integers ranging from 1-40. This vector is then assigned (←) to the variable x, because it is needed later. This vector is then sorted in ascending order by a monadic ⍋ function, which has as its right argument everything to the right of it up to the next unbalanced close-bracket or close-parenthesis. The result of ⍋ is the indices that will put its argument into ascending order. Then the output of ⍋ is used to index the variable x, which we saved earlier for this purpose, thereby selecting its items in ascending sequence. Since there is no function to the left of the left-most x to tell APL what to do with the result, it simply outputs it to the display (on a single line, separated by spaces) without needing any explicit instruction to do that. ? also has a monadic equivalent called roll, which simply returns one random integer between 1 and its sole operand [to the right of it], inclusive. Thus, a role-playing game program might use the expression ?20 to roll a twenty-sided die. Prime numbers The following expression finds all prime numbers from 1 to R. In both time and space, the calculation complexity is (in Big O notation). (~R∊R∘.×R)/R←1↓⍳R Executed from right to left, this means: Iota ⍳ creates a vector containing integers from 1 to R (if R= 6 at the start of the program, ⍳R is 1 2 3 4 5 6) Drop first element of this vector (↓ function), i.e., 1. So 1↓⍳R is 2 3 4 5 6 Set R to the new vector (←, assignment primitive), i.e., 2 3 4 5 6 The / replicate operator is dyadic (binary) and the interpreter first evaluates its left argument (fully in parentheses): Generate outer product of R multiplied by R, i.e., a matrix that is the multiplication table of R by R (°.× operator), i.e., Build a vector the same length as R with 1 in each place where the corresponding number in R is in the outer product matrix (∈, set inclusion or element of or Epsilon operator), i.e., 0 0 1 0 1 Logically negate (not) values in the vector (change zeros to ones and ones to zeros) (∼, logical not or Tilde operator), i.e., 1 1 0 1 0 Select the items in R for which the corresponding element is 1 (/ replicate operator), i.e., 2 3 5 (Note, this assumes the APL origin is 1, i.e., indices start with 1. APL can be set to use 0 as the origin, so that ι6 is 0 1 2 3 4 5, which is convenient for some calculations.) Sorting The following expression sorts a word list stored in matrix X according to word length: X[⍋X+.≠' ';] Game of Life The following function "life", written in Dyalog APL, takes a boolean matrix and calculates the new generation according to Conway's Game of Life. It demonstrates the power of APL to implement a complex algorithm in very little code, but it is also very hard to follow unless one has advanced knowledge of APL. life ← {⊃1 ⍵ ∨.∧ 3 4 = +/ +⌿ ¯1 0 1 ∘.⊖ ¯1 0 1 ⌽¨ ⊂⍵} HTML tags removal In the following example, also Dyalog, the first line assigns some HTML code to a variable txt and then uses an APL expression to remove all the HTML tags (explanation): txt←'<html><body><p>This is <em>emphasized</em> text.</p></body></html>' {⍵ /⍨ ~{⍵∨≠\⍵}⍵∊'<>'} txt This is emphasized text. Naming APL derives its name from the initials of Iverson's book A Programming Language, even though the book describes Iverson's mathematical notation, rather than the implemented programming language described in this article. The name is used only for actual implementations, starting with APL\360. Adin Falkoff coined the name in 1966 during the implementation of APL\360 at IBM: APL is occasionally re-interpreted as Array Programming Language or Array Processing Language, thereby making APL into a backronym. Logo There has always been cooperation between APL vendors, and joint conferences were held on a regular basis from 1969 until 2010. At such conferences, APL merchandise was often handed out, featuring APL motifs or collection of vendor logos. Common were apples (as a pun on the similarity in pronunciation of apple and APL) and the code snippet which are the symbols produced by the classic APL keyboard layout when holding the APL modifier key and typing "APL". Despite all these community efforts, no universal vendor-agnostic logo for the programming language emerged. As popular programming languages increasingly have established recognisable logos, Fortran getting one in 2020, British APL Association launched a campaign in the second half of 2021, to establish such a logo for APL. Use APL is used for many purposes including financial and insurance applications, artificial intelligence, neural networks and robotics. It has been argued that APL is a calculation tool and not a programming language; its symbolic nature and array capabilities have made it popular with domain experts and data scientists who do not have or require the skills of a computer programmer. APL is well suited to image manipulation and computer animation, where graphic transformations can be encoded as matrix multiplications. One of the first commercial computer graphics houses, Digital Effects, produced an APL graphics product named Visions, which was used to create television commercials and animation for the 1982 film Tron. Latterly, the Stormwind boating simulator uses APL to implement its core logic, its interfacing to the rendering pipeline middleware and a major part of its physics engine. Today, APL remains in use in a wide range of commercial and scientific applications, for example investment management, asset management, health care, and DNA profiling, and by hobbyists. Notable implementations APL\360 The first implementation of APL using recognizable APL symbols was APL\360 which ran on the IBM System/360, and was completed in November 1966 though at that time remained in use only within IBM. In 1973 its implementors, Larry Breed, Dick Lathwell and Roger Moore, were awarded the Grace Murray Hopper Award from the Association for Computing Machinery (ACM). It was given "for their work in the design and implementation of APL\360, setting new standards in simplicity, efficiency, reliability and response time for interactive systems." In 1975, the IBM 5100 microcomputer offered APL\360 as one of two built-in ROM-based interpreted languages for the computer, complete with a keyboard and display that supported all the special symbols used in the language. Significant developments to APL\360 included CMS/APL, which made use of the virtual storage capabilities of CMS and APLSV, which introduced shared variables, system variables and system functions. It was subsequently ported to the IBM System/370 and VSPC platforms until its final release in 1983, after which it was replaced by APL2. APL\1130 In 1968, APL\1130 became the first publicly available APL system, created by IBM for the IBM 1130. It became the most popular IBM Type-III Library software that IBM released. APL*Plus and Sharp APL APL*Plus and Sharp APL are versions of APL\360 with added business-oriented extensions such as data formatting and facilities to store APL arrays in external files. They were jointly developed by two companies, employing various members of the original IBM APL\360 development team. The two companies were I. P. Sharp Associates (IPSA), an APL\360 services company formed in 1964 by Ian Sharp, Roger Moore and others, and STSC, a time-sharing and consulting service company formed in 1969 by Lawrence Breed and others. Together the two developed APL*Plus and thereafter continued to work together but develop APL separately as APL*Plus and Sharp APL. STSC ported APL*Plus to many platforms with versions being made for the VAX 11, PC and UNIX, whereas IPSA took a different approach to the arrival of the personal computer and made Sharp APL available on this platform using additional PC-XT/360 hardware. In 1993, Soliton Incorporated was formed to support Sharp APL and it developed Sharp APL into SAX (Sharp APL for Unix). , APL*Plus continues as APL2000 APL+Win. In 1985, Ian Sharp, and Dan Dyer of STSC, jointly received the Kenneth E. Iverson Award for Outstanding Contribution to APL. APL2 APL2 was a significant re-implementation of APL by IBM which was developed from 1971 and first released in 1984. It provides many additions to the language, of which the most notable is nested (non-rectangular) array support. The entire APL2 Products and Services Team was awarded the Iverson Award in 2007. In 2021, IBM sold APL2 to Log-On Software, who develop and sell the product as Log-On APL2. APLGOL In 1972, APLGOL was released as an experimental version of APL that added structured programming language constructs to the language framework. New statements were added for interstatement control, conditional statement execution, and statement structuring, as well as statements to clarify the intent of the algorithm. It was implemented for Hewlett-Packard in 1977. Dyalog APL Dyalog APL was first released by British company Dyalog Ltd. in 1983 and, , is available for AIX, Linux (including on the Raspberry Pi), macOS and Microsoft Windows platforms. It is based on APL2, with extensions to support object-oriented programming and functional programming. Licences are free for personal/non-commercial use. In 1995, two of the development team - John Scholes and Peter Donnelly - were awarded the Iverson Award for their work on the interpreter. Gitte Christensen and Morten Kromberg were joint recipients of the Iverson Award in 2016. NARS2000 NARS2000 is an open-source APL interpreter written by Bob Smith, a prominent APL developer and implementor from STSC in the 1970s and 1980s. NARS2000 contains advanced features and new datatypes and runs natively on Microsoft Windows, and other platforms under Wine. It is named after a development tool from the 1980s, NARS (Nested Arrays Research System). APLX APLX is a cross-platform dialect of APL, based on APL2 and with several extensions, which was first released by British company MicroAPL in 2002. Although no longer in development or on commercial sale it is now available free of charge from Dyalog. GNU APL GNU APL is a free implementation of Extended APL as specified in ISO/IEC 13751:2001 and is thus an implementation of APL2. It runs on Linux (including on the Raspberry Pi), macOS, several BSD dialects, and on Windows (either using Cygwin for full support of all its system functions or as a native 64-bit Windows binary with some of its system functions missing). GNU APL uses Unicode internally and can be scripted. It was written by Jürgen Sauermann. Richard Stallman, founder of the GNU Project, was an early adopter of APL, using it to write a text editor as a high school student in the summer of 1969. Interpretation and compilation of APL APL is traditionally an interpreted language, having language characteristics such as weak variable typing not well suited to compilation. However, with arrays as its core data structure it provides opportunities for performance gains through parallelism, parallel computing, massively parallel applications, and very-large-scale integration (VLSI), and from the outset APL has been regarded as a high-performance language - for example, it was noted for the speed with which it could perform complicated matrix operations "because it operates on arrays and performs operations like matrix inversion internally". Nevertheless, APL is rarely purely interpreted and compilation or partial compilation techniques that are, or have been, used include the following: Idiom recognition Most APL interpreters support idiom recognition and evaluate common idioms as single operations. For example, by evaluating the idiom BV/⍳⍴A as a single operation (where BV is a Boolean vector and A is an array), the creation of two intermediate arrays is avoided. Optimised bytecode Weak typing in APL means that a name may reference an array (of any datatype), a function or an operator. In general, the interpreter cannot know in advance which form it will be and must therefore perform analysis, syntax checking etc. at run-time. However, in certain circumstances, it is possible to deduce in advance what type a name is expected to reference and then generate bytecode which can be executed with reduced run-time overhead. This bytecode can also be optimised using compilation techniques such as constant folding or common subexpression elimination. The interpreter will execute the bytecode when present and when any assumptions which have been made are met. Dyalog APL includes support for optimised bytecode. Compilation Compilation of APL has been the subject of research and experiment since the language first became available; the first compiler is considered to be the Burroughs APL-700 which was released around 1971. In order to be able to compile APL, language limitations have to be imposed. APEX is a research APL compiler which was written by Robert Bernecky and is available under the GNU Public License. The STSC APL Compiler is a hybrid of a bytecode optimiser and a compiler - it enables compilation of functions to machine code provided that its sub-functions and globals are declared, but the interpreter is still used as a runtime library and to execute functions which do not meet the compilation requirements. Standards APL has been standardized by the American National Standards Institute (ANSI) working group X3J10 and International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC), ISO/IEC Joint Technical Committee 1 Subcommittee 22 Working Group 3. The Core APL language is specified in ISO 8485:1989, and the Extended APL language is specified in ISO/IEC 13751:2001. References Further reading An APL Machine (1970 Stanford doctoral dissertation by Philip Abrams) A Personal History Of APL (1982 article by Michael S. Montalbano) A Programming Language by Kenneth E. Iverson APL in Exposition by Kenneth E. Iverson Brooks, Frederick P.; Kenneth Iverson (1965). Automatic Data Processing, System/360 Edition. . History of Programming Languages, chapter 14 Video The Origins of APL - a 1974 talk show style interview with the original developers of APL. APL demonstration - a 1975 live demonstration of APL by Professor Bob Spence, Imperial College London. Conway's Game Of Life in APL - a 2009 tutorial by John Scholes of Dyalog Ltd. which implements Conway's Game of Life in a single line of APL. 50 Years of APL - a 2009 introduction to APL by Graeme Robertson. External links Online resources TryAPL.org, an online APL primer APL Wiki APL2C, a source of links to APL compilers Providers Log-On APL2 Dyalog APL APLX APL2000 NARS2000 GNU APL OpenAPL User groups and societies Finland: Finnish APL Association (FinnAPL) France: APL et J Germany: APL-Germany e.V. Japan: Japan APL Association (JAPLA) Sweden: Swedish APL User Group (SwedAPL) Switzerland: Swiss APL User Group (SAUG) United Kingdom: The British APL Association United States: ACM SIGPLAN chapter on Array Programming Languages (SIGAPL) .NET programming languages APL programming language family Array programming languages Command shells Dynamic programming languages Dynamically typed programming languages Functional languages IBM software Programming languages created in 1964 Programming languages with an ISO standard Programming languages

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1485

https://en.wikipedia.org/wiki/Alain%20de%20Lille

Alain de Lille

Alain de Lille (Alan of Lille) (Latin: Alanus ab Insulis; 11281202/03) was a French theologian and poet. He was born in Lille, some time before 1128. His exact date of death remains unclear as well, with most research pointing toward it being between 14 April 1202, and 5 April 1203. He is known for writing a number of works on that are based upon the teachings of the liberal arts, with one of his most renowned poems, De planctu Naturae (The Complaint of Nature), focusing on human nature in regard to sexual conduct. Although, Alain was widely known during his lifetime, there is not a great deal known about his personal life, with the majority of our knowledge of the theologian coming from the content of his works. Life Little is known of his life. Alain entered the schools no earlier than the late 1140s; first attending the school at Paris, and then at Chartres. He probably studied under masters such as Peter Abelard, Gilbert of Poitiers, and Thierry of Chartres. This is known through the writings of John of Salisbury, who is thought to have been a contemporary student of Alain of Lille. His earliest writings were probably written in the 1150s, and probably in Paris. Alain spent many years as a professor of Theology at the University of Paris and he attended the Lateran Council in 1179. Though the only accounts of his lectures seem to show a sort of eccentric style and approach, he was said to have been good friends with many other masters at the school in Paris, and taught there, as well as some time in southern France, into his old age. He afterwards inhabited Montpellier (he is sometimes called Alanus de Montepessulano), lived for a time outside the walls of any cloister, and finally retired to Cîteaux, where he died in 1202. He had a very widespread reputation during his lifetime, and his knowledge caused him to be called Doctor Universalis. Many of Alain's writings are unable to be exactly dated, and the circumstances and details surrounding his writing are often unknown as well. However, it does seem clear that his first notable work, Summa Quoniam Homines, was completed somewhere between 1155 and 1165, with the most conclusive date being 1160, and was probably developed through his lectures at the school in Paris. Among his very numerous works two poems entitle him to a distinguished place in the Latin literature of the Middle Ages; one of these, the De planctu naturae, is an ingenious satire on the vices of humanity. He created the allegory of grammatical "conjugation" which was to have its successors throughout the Middle Ages. The Anticlaudianus, a treatise on morals as allegory, the form of which recalls the pamphlet of Claudian against Rufinus, is agreeably versified and relatively pure in its latinity. Theology and philosophy As a theologian Alain de Lille shared in the mystic reaction of the second half of the 12th century against the scholastic philosophy. His mysticism, however, is far from being as absolute as that of the Victorines. In the Anticlaudianus he sums up as follows: Reason, guided by prudence, can unaided discover most of the truths of the physical order; for the apprehension of religious truths it must trust to faith. This rule is completed in his treatise, Ars catholicae fidei, as follows: Theology itself may be demonstrated by reason. Alain even ventures an immediate application of this principle, and tries to prove geometrically the dogmas defined in the Creed. This bold attempt is entirely factitious and verbal, and it is only his employment of various terms not generally used in such a connection (axiom, theorem, corollary, etc.) that gives his treatise its apparent originality. Alan's philosophy was a sort of mixture of Aristotelian logic and Neoplatonic philosophy. The Platonist seemed to outweigh the Aristotelian in Alan, but he felt strongly that the divine is all intelligibility and argued this notion through much Aristotelian logic combined with Pythagorean mathematics. Works and attributions One of Alain's most notable works was one he modeled after Boethius’ Consolation of Philosophy, to which he gave the title De Planctu Naturae, or The Plaint of Nature, and which was most likely written in the late 1160s. In this work, Alan uses prose and verse to illustrate the way in which nature defines its own position as inferior to that of God. He also attempts to illustrate the way in which humanity, through sexual perversion and specifically homosexuality, has defiled itself from nature and God. In Anticlaudianus, another of his notable works, Alan uses a poetical dialogue to illustrate the way in which nature comes to the realization of her failure in producing the perfect man. She has only the ability to create a soulless body, and thus she is "persuaded to undertake the journey to heaven to ask for a soul," and "the Seven Liberal Arts produce a chariot for her... the Five Senses are the horses". The Anticlaudianus was translated into French and German in the following century, and toward 1280 was re-worked into a musical anthology by Adam de la Bassée. One of Alan's most popular and widely distributed works is his manual on preaching, Ars Praedicandi, or The Art of Preaching. This work shows how Alan saw theological education as being a fundamental preliminary step in preaching and strove to give clergyman a manuscript to be "used as a practical manual" when it came to the formation of sermons and art of preaching. Alain wrote three very large theological textbooks, one being his first work, Summa Quoniam Homines. Another of his theological textbooks that strove to be more minute in its focus, is his De Fide Catholica, dated somewhere between 1185 and 1200, Alan sets out to refute heretical views, specifically that of the Waldensians and Cathars. In his third theological textbook, Regulae Caelestis Iuris, he presents a set of what seems to be theological rules; this was typical of the followers of Gilbert of Poitiers, of which Alan could be associated. Other than these theological textbooks, and the aforementioned works of the mixture of prose and poetry, Alan of Lille had numerous other works on numerous subjects, primarily including Speculative Theology, Theoretical Moral Theology, Practical Moral Theology, and various collections of poems. Alain de Lille has often been confounded with other persons named Alain, in particular with another Alanus (Alain, bishop of Auxerre), Alan, abbot of Tewkesbury, Alain de Podio, etc. Certain facts of their lives have been attributed to him, as well as some of their works: thus the Life of St Bernard should be ascribed to Alain of Auxerre and the Commentary upon Merlin to Alan of Tewkesbury. Alan of Lille was not the author of a Memoriale rerum difficilium, published under his name, nor of Moralium dogma philosophorum, nor of the satirical Apocalypse of Golias once attributed to him; and it is exceedingly doubtful whether the Dicta Alani de lapide philosophico really issued from his pen. On the other hand, it now seems practically demonstrated that Alain de Lille was the author of the Ars catholicae fidei and the treatise Contra haereticos. In his sermons on capital sins, Alain argued that sodomy and homicide are the most serious sins, since they call forth the wrath of God, which led to the destruction of Sodom and Gomorrah. His chief work on penance, the Liber poenitenitalis dedicated to Henry de Sully, exercised great influence on the many manuals of penance produced as a result of the Fourth Lateran Council. Alain's identification of the sins against nature included bestiality, masturbation, oral and anal intercourse, incest, adultery and rape. In addition to his battle against moral decay, Alan wrote a work against Islam, Judaism and Christian heretics dedicated to William VIII of Montpellier. List of known works Anticlaudianus Rhythmus de Incarnatione et de Septem Artibus De Miseria Mundi Quaestiones Alani Textes Summa Quoniam Homines Regulae Theologicae Hierarchia Alani De Fide Catholica: Contra Haereticos, Valdenses, Iudaeos et Paganos De Virtutibus, de Vitiis, de Donis Spiritus Sancti Liber Parabolarum Distinctiones Dictionum Theologicalium Elucidatio in Cantica Canticorum Glosatura super Cantica Expositio of the Pater Noster Expositiones of the Nicene and Apostolic Creeds Expositio Prosae de Angelis Quod non-est celebrandum bis in die Liber Poenitentialis De Sex Alis Cherubim Ars Praedicandi Sermones References Attribution: Translations Alan of Lille, A Concise Explanation of the Song of Songs in Praise of the Virgin Mary, trans Denys Turner, in Denys Turner, Eros and Allegory: Medieval Exegesis of the Song of Songs, (Kalamazoo, MI: Cistercian Publications, 1995), 291–308 The Plaint of Nature, translated by James J Sheridan, (Toronto: Pontifical Institute of Mediaeval Studies, 1980) Anticlaudian: Prologue, Argument and Nine Books, edited by W. H. Cornog, (Philadelphia, 1935) Further reading Alain de Lille: De planctu Naturae, ed. Nikolaus M. Häring, Studi Medievali 19 (1978), 797–879. Latin edition of the De planctu Naturae. Dynes, Wayne R. 'Alan of Lille.' in Encyclopedia of Homosexuality, Garland Publishing, 1990. p. 32. Alanus de insulis, Anticlaudianus, a c. di . M. Sannelli, La Finestra editrice, Lavis, 2004. Evans, G. R. (1983), Alan of Lille: The Frontiers of Theology in the Later Twelfth Century, Cambridge: Cambridge. . External links (Latin) Alanus ab Insulis, Anticlaudianus sive De officiis viri boni et perfecti (Latin) [http://www.thelatinlibrary.com/alanus/alanus1.html Alanus ab Insulis, Liber de planctu naturae] (Latin) Alanus ab Insulis, Omnis mundi creatura (Latin) Alanus ab Insulis, Distinctiones dictionum theologicalium (English) Alain of Lille, The Complaint of Nature. Translation of Liber de planctu naturae'' 12th-century philosophers 1110s births 1200s deaths People from Lille 12th-century Latin writers 12th-century Christian mystics Scholastic philosophers Roman Catholic mystics 12th-century French Catholic theologians Medieval Latin poets 12th-century French poets 12th-century French philosophers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1514

https://en.wikipedia.org/wiki/Albert%2C%20Duke%20of%20Prussia

Albert, Duke of Prussia

Albert of Prussia (; 17 May 149020 March 1568) was a German prince who was the 37th Grand Master of the Teutonic Knights, who after converting to Lutheranism, became the first ruler of the Duchy of Prussia, the secularized state that emerged from the former Monastic State of the Teutonic Knights. Albert was the first European ruler to establish Lutheranism, and thus Protestantism, as the official state religion of his lands. He proved instrumental in the political spread of Protestantism in its early stage, ruling the Prussian lands for nearly six decades (1510–1568). A member of the Brandenburg-Ansbach branch of the House of Hohenzollern, Albert became Grand Master, where his skill in political administration and leadership ultimately succeeded in reversing the decline of the Teutonic Order. But Albert, who was sympathetic to the demands of Martin Luther, rebelled against the Roman Catholic Church and the Holy Roman Empire by converting the Teutonic state into a Protestant and hereditary realm, the Duchy of Prussia, for which he paid homage to his uncle, Sigismund I, King of Poland. That arrangement was confirmed by the Treaty of Kraków in 1525. Albert pledged a personal oath to the King and in return was invested with the duchy for himself and his heirs. Albert's rule in Prussia was fairly prosperous. Although he had some trouble with the peasantry, the confiscation of the lands and treasures of the Catholic Church enabled him to propitiate the nobles and provide for the expenses of the newly established Prussian court. He was active in imperial politics, joining the League of Torgau in 1526, and acted in unison with the Protestants in plotting to overthrow Emperor Charles V after the issue of the Augsburg Interim in May 1548. Albert established schools in every town and founded Königsberg University in 1544. He promoted culture and arts, patronising the works of Erasmus Reinhold and Caspar Hennenberger. During the final years of his rule, Albert was forced to raise taxes instead of further confiscating now-depleted church lands, causing peasant rebellion. The intrigues of the court favourites Johann Funck and Paul Skalić also led to various religious and political disputes. Albert spent his final years virtually deprived of power and died at Tapiau on 20 March 1568. His son, Albert Frederick, succeeded him as Duke of Prussia. Albert's dissolution of the Teutonic State caused the founding of the Duchy of Prussia, paving the way for the rise of the House of Hohenzollern. Early life Albert was born in Ansbach in Franconia as the third son of Frederick I, Margrave of Brandenburg-Ansbach. His mother was Sophia, daughter of Casimir IV Jagiellon, Grand Duke of Lithuania and King of Poland, and his wife Elisabeth of Austria. He was raised for a career in the Church and spent some time at the court of Hermann IV of Hesse, Elector of Cologne, who appointed him canon of the Cologne Cathedral. Not only was he quite religious; he was also interested in mathematics and science and sometimes is claimed to have contradicted the teachings of the Church in favour of scientific theories. His career was forwarded by the Church, however, and institutions of the Catholic clerics supported his early advancement. Turning to a more active life, Albert accompanied Emperor Maximilian I to Italy in 1508 and after his return spent some time in the Kingdom of Hungary. Grand Master Duke Frederick of Saxony, Grand Master of the Teutonic Order, died in December 1510. Albert was chosen as his successor early in 1511 in the hope that his relationship to his maternal uncle, Sigismund I the Old, Grand Duke of Lithuania and King of Poland, would facilitate a settlement of the disputes over eastern Prussia, which had been held by the order under Polish suzerainty since the Second Peace of Thorn (1466). The new Grand Master, aware of his duties to the empire and to the papacy, refused to submit to the crown of Poland. As war over the order's existence appeared inevitable, Albert made strenuous efforts to secure allies and carried on protracted negotiations with Emperor Maximilian I. The ill-feeling, influenced by the ravages of members of the Order in Poland, culminated in a war which began in December 1519 and devastated Prussia. Albert was granted a four-year truce early in 1521. The dispute was referred to Emperor Charles V and other princes, but as no settlement was reached Albert continued his efforts to obtain help in view of a renewal of the war. For this purpose he visited the Diet of Nuremberg in 1522, where he made the acquaintance of the Reformer Andreas Osiander, by whose influence Albert was won over to Protestantism. The Grand Master then journeyed to Wittenberg, where he was advised by Martin Luther to abandon the rules of his order, to marry, and to convert Prussia into a hereditary duchy for himself. This proposal, which was understandably appealing to Albert, had already been discussed by some of his relatives; but it was necessary to proceed cautiously, and he assured Pope Adrian VI that he was anxious to reform the order and punish the knights who had adopted Lutheran doctrines. Luther for his part did not stop at the suggestion, but in order to facilitate the change made special efforts to spread his teaching among the Prussians, while Albert's brother, Margrave George of Brandenburg-Ansbach, laid the scheme before their uncle, Sigismund I the Old of Poland. Duke in Prussia After some delay Sigismund assented to the offer, with the provision that Prussia should be treated as a Polish fiefdom; and after this arrangement had been confirmed by a treaty concluded at Kraków, Albert pledged a personal oath to Sigismund I and was invested with the duchy for himself and his heirs on 10 February 1525. The Estates of the land then met at Königsberg and took the oath of allegiance to the new duke, who used his full powers to promote the doctrines of Luther. This transition did not, however, take place without protest. Summoned before the imperial court of justice, Albert refused to appear and was proscribed, while the order elected a new Grand Master, Walter von Cronberg, who received Prussia as a fief at the imperial Diet of Augsburg. As the German princes were experiencing the tumult of the Reformation, the German Peasants' War, and the wars against the Ottoman Turks, they did not enforce the ban on the duke, and agitation against him soon died away. In imperial politics Albert was fairly active. Joining the League of Torgau in 1526, he acted in unison with the Protestants, and was among the princes who banded and plotted together to overthrow Charles V after the issue of the Augsburg Interim in May 1548. For various reasons, however, poverty and personal inclination among others, he did not take a prominent part in the military operations of this period. The early years of Albert's rule in Prussia were fairly prosperous. Although he had some trouble with the peasantry, the lands and treasures of the church enabled him to propitiate the nobles and for a time to provide for the expenses of the court. He did something for the furtherance of learning by establishing schools in every town and by freeing serfs who adopted a scholastic life. In 1544, in spite of some opposition, he founded Königsberg University, where he appointed his friend Andreas Osiander to a professorship in 1549. Albert also paid for the printing of the Astronomical "Prutenic Tables" compiled by Erasmus Reinhold and the first maps of Prussia by Caspar Hennenberger. Osiander's appointment was the beginning of the troubles which clouded the closing years of Albert's reign. Osiander's divergence from Luther's doctrine of justification by faith involved him in a violent quarrel with Philip Melanchthon, who had adherents in Königsberg, and these theological disputes soon created an uproar in the town. The duke strenuously supported Osiander, and the area of the quarrel soon broadened. There were no longer church lands available with which to conciliate the nobles, the burden of taxation was heavy, and Albert's rule became unpopular. After Osiander's death in 1552, Albert favoured a preacher named Johann Funck, who, with an adventurer named Paul Skalić, exercised great influence over him and obtained considerable wealth at public expense. The state of turmoil caused by these religious and political disputes was increased by the possibility of Albert's early death and the need, should that happen, to appoint a regent, as his only son, Albert Frederick was still a mere youth. The duke was forced to consent to a condemnation of the teaching of Osiander, and the climax came in 1566 when the Estates appealed to King Sigismund II Augustus of Poland, Albert's cousin, who sent a commission to Königsberg. Skalić saved his life by flight, but Funck was executed. The question of the regency was settled, and a form of Lutheranism was adopted and declared binding on all teachers and preachers. Virtually deprived of power, the duke lived for two more years, and died at Tapiau on 20 March 1568 of the plague, along with his wife. Cornelis Floris de Vriendt designed his tomb within Königsberg Cathedral. Albert was a voluminous letter writer, and corresponded with many of the leading personages of the time. Legacy Albert was the first German noble to support Luther's ideas and in 1544 founded the University of Königsberg, the Albertina, as a rival to the Roman Catholic Krakow Academy. It was the second Lutheran university in the German states, after the University of Marburg. A relief of Albert over the Renaissance-era portal of Königsberg Castle's southern wing was created by Andreas Hess in 1551 according to plans by Christoph Römer. Another relief by an unknown artist was included in the wall of the Albertina's original campus. This depiction, which showed the duke with his sword over his shoulder, was the popular "Albertus", the symbol of the university. The original was moved to Königsberg Public Library to protect it from the elements, while the sculptor Paul Kimritz created a duplicate for the wall. Another version of the "Albertus" by Lothar Sauer was included at the entrance of the Königsberg State and Royal Library. In 1880 Friedrich Reusch created a sandstone bust of Albert at the Regierungsgebäude, the administrative building for Regierungsbezirk Königsberg. On 19 May 1891 Reusch premiered a famous statue of Albert at Königsberg Castle with the inscription: "Albert of Brandenburg, Last Grand Master, First Duke in Prussia". Albert Wolff also designed an equestrian statue of Albert located at the new campus of the Albertina. King's Gate contains a statue of Albert. Albert was oft-honored in the quarter Maraunenhof in northern Königsberg. Its main street was named Herzog-Albrecht-Allee in 1906. Its town square, König-Ottokar-Platz, was renamed Herzog-Albrecht-Platz in 1934 to match its church, the Herzog-Albrecht-Gedächtniskirche. Spouse and issue Albert married first, to Dorothea (1 August 150411 April 1547), daughter of King Frederick I of Denmark, in 1526. They had six children: Anna Sophia (11 June 15276 February 1591), married John Albert I, Duke of Mecklenburg-Güstrow. Katharina (b. and d. 24 February 1528). Frederick Albert (5 December 15291 January 1530). Lucia Dorothea (8 April 15311 February 1532). Lucia (3 February 1537May 1539). Albert (b. and d. March 1539). He married secondly to Anna Maria (1532–20 March 1568), daughter of Eric I, Duke of Brunswick-Lüneburg, in 1550. The couple had two children: Elisabeth (20 May 155119 February 1596). Albert Frederick (29 April 155318 August 1618), Duke of Prussia. Ancestors Notes References External links William Urban on the situation in Prussia K. P. Faber: Briefe Luthers an Herzog Albrecht (1811) letters of Martin Luther to Albrecht |- Dukes of Prussia Protestant monarchs 1490 births 1568 deaths 16th-century Dukes of Prussia Converts to Lutheranism from Roman Catholicism German people of Lithuanian descent German people of Polish descent German Lutherans Grand Masters of the Teutonic Order House of Hohenzollern People excommunicated by the Catholic Church People from Ansbach People from the Principality of Ansbach People from the Duchy of Prussia People of the Polish–Teutonic War (1519–1521) University of Königsberg Duchy of Prussia People of the Count's Feud

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1520

https://en.wikipedia.org/wiki/Aachen

Aachen

Aachen (; Aachen dialect: Oche ; French and traditional English: Aix-la-Chapelle; or Aquisgranum; ) is, with around 249,000 inhabitants, the 13th-largest city in North Rhine-Westphalia, and the 28th-largest city of Germany. It is the westernmost city in Germany, and borders Belgium and the Netherlands to the west, the Tri-border area. It is located between Maastricht (NL) and Liège (BE) in the west, and Bonn and Cologne, in the east. The Wurm River flows through the city, and together with Mönchengladbach, Aachen is the only larger German city in the drainage basin of the Meuse. Aachen is the seat of the City Region Aachen (). Aachen developed from a Roman settlement and thermae (bath complex), subsequently becoming the preferred medieval Imperial residence of Emperor Charlemagne of the Frankish Empire, and, from 936 to 1531, the place where 31 Holy Roman Emperors were crowned Kings of the Germans. One of Germany's leading institutes of higher education in technology, the RWTH Aachen University (Rheinisch-Westfälisch Technische Hochschule Aachen), is located in the city. Its university hospital Uniklinik RWTH Aachen is Europe's largest single-building hospital. Aachen's industries include science, engineering and information technology. In 2009, Aachen was ranked eighth among cities in Germany for innovation. The regional dialect spoken in the city is a Central Franconian, Ripuarian variant with strong Limburgish influences from the dialects in the neighbouring Netherlands. As a Rhenish city, Aachen is one of the main centres of carnival celebrations in Germany, along with Cologne, Mainz and Düsseldorf. The culinary speciality the city is best known for are Aachener Printen, a type of gingerbread. History Early history Flint quarries on the Lousberg, Schneeberg, and Königshügel, first used during Neolithic times (3000–2500 BC), attest to the long occupation of the site of Aachen, as do recent finds under the modern city's Elisengarten pointing to a former settlement from the same period. Bronze Age (around 1600 BC) settlement is evidenced by the remains of barrows (burial mounds) found, for example, on the Klausberg. During the Iron Age, the area was settled by Celtic peoples who were perhaps drawn by the marshy Aachen basin's hot sulphur springs where they worshipped Grannus, god of light and healing. Later, the 25-hectare Roman spa resort town of Aquae Granni was, according to legend, founded by Grenus, under Hadrian, around 124 AD. Instead, the fictitious founder refers to the Celtic god, and it seems it was the Roman 6th Legion at the start of the 1st century AD that first channelled the hot springs into a spa at Büchel, adding at the end of the same century the Münstertherme spa, two water pipelines, and a probable sanctuary dedicated to Grannus. A kind of forum, surrounded by colonnades, connected the two spa complexes. There was also an extensive residential area, part of it inhabited by a flourishing Jewish community. The Romans built bathhouses near Burtscheid. A temple precinct called Vernenum was built near the modern Kornelimünster/Walheim. Today, remains have been found of three bathhouses, including two fountains in the Elisenbrunnen and the Burtscheid bathhouse. Roman civil administration in Aachen eventually broke down as the baths and other public buildings (along with most of the villae rusticae of the surrounding countryside) were destroyed around AD 375 at the start of the migration period. The last Roman coin finds are from the time of Emperor Gratian (AD 375–383). Rome withdrew its troops from the area, but the town remained populated. By 470, the town came to be ruled by the Ripuarian Franks and subordinated to their capital, Cologne. Etymology The name Aachen is a modern descendant, like southern German , , meaning "river" or "stream", from Old High German , meaning "water" or "stream", which directly translates (and etymologically corresponds) to Latin , referring to the springs. The location has been inhabited by humans since the Neolithic era, about 5,000 years ago, attracted to its warm mineral springs. Latin figures in Aachen's Roman name , which meant "waters of Grannus", referring to the Celtic god of healing who was worshipped at the springs. This word became in Walloon and in French, and subsequently after Charlemagne had his palatine chapel built there in the late 8th century and then made the city his empire's capital. As a spa city, Aachen has the right to name itself Bad Aachen, but chooses not to, so it remains on the top of alphabetical lists. Aachen's name in French and German evolved in parallel. The city is known by a variety of different names in other languages: Dialect Aachen is at the western end of the Benrath line that divides High German to the south from the rest of the West Germanic speech area to the north. Aachen's local dialect is called and belongs to the Ripuarian language. Middle Ages After Roman times, Pepin the Short had a castle residence built in the town, due to the proximity of the hot springs and also for strategic reasons as it is located between the Rhineland and northern France. Einhard mentions that in 765–6 Pepin spent both Christmas and Easter at Aquis villa (), ("and [he] celebrated Christmas in the town Aquis, and similarly Easter") which must have been sufficiently equipped to support the royal household for several months. In the year of his coronation as king of the Franks, 768, Charlemagne came to spend Christmas at Aachen for the first time. He remained there in a mansion which he may have extended, although there is no source attesting to any significant building activity at Aachen in his time, apart from the building of the Palatine Chapel (since 1930, cathedral) and the Palace. Charlemagne spent most winters in Aachen between 792 and his death in 814. Aachen became the focus of his court and the political centre of his empire. After his death, the king was buried in the church which he had built; his original tomb has been lost, while his alleged remains are preserved in the Karlsschrein, the shrine where he was reburied after being declared a saint; his saintliness, however, was never officially acknowledged by the Roman Curia as such. In 936, Otto I was crowned king of East Francia in the collegiate church built by Charlemagne. During the reign of Otto II, the nobles revolted and the West Franks under Lothair raided Aachen in 978. Aachen was attacked again by Odo of Champagne, who attacked the imperial palace while Conrad II was absent. Odo relinquished it quickly and was killed soon afterwards. The palace and town of Aachen had fortifying walls built by order of Emperor Frederick Barbarossa between 1172 and 1176. Over the next 500 years, most kings of Germany destined to reign over the Holy Roman Empire were crowned in Aachen. The original audience hall built by Charlemagne was torn down and replaced by the current city hall in 1330. The last king to be crowned here was Ferdinand I in 1531. During the Middle Ages, Aachen remained a city of regional importance, due to its proximity to Flanders; it achieved a modest position in the trade in woollen cloths, favoured by imperial privilege. The city remained a free imperial city, subject to the emperor only, but was politically far too weak to influence the policies of any of its neighbours. The only dominion it had was over Burtscheid, a neighbouring territory ruled by a Benedictine abbess. It was forced to accept that all of its traffic must pass through the "Aachener Reich". Even in the late 18th century the Abbess of Burtscheid was prevented from building a road linking her territory to the neighbouring estates of the duke of Jülich; the city of Aachen even deployed its handful of soldiers to chase away the road-diggers. As an imperial city, Aachen held certain political privileges that allowed it to remain independent of the troubles of Europe for many years. It remained a direct vassal of the Holy Roman Empire throughout most of the Middle Ages. It was also the site of many important church councils, including the Council of 837 and the Council of 1166, a council convened by the antipope Paschal III. Manuscript production Aachen has proved an important site for the production of historical manuscripts. Under Charlemagne's purview, both the Ada Gospels and the Coronation Gospels may have been produced in Aachen. In addition, quantities of the other texts in the court library were also produced locally. During the reign of Louis the Pious (814–840), substantial quantities of ancient texts were produced at Aachen, including legal manuscripts such as the leges scriptorium group, patristic texts including the five manuscripts of the Bamberg Pliny Group. Finally, under Lothair I (840–855), texts of outstanding quality were still being produced. This however marked the end of the period of manuscript production at Aachen. 16th–18th centuries In 1598, following the invasion of Spanish troops from the Netherlands, Rudolf deposed all Protestant office holders in Aachen and even went as far as expelling them from the city. From the early 16th century, Aachen started to lose its power and influence. First the coronations of emperors were moved from Aachen to Frankfurt. This was followed by the religious wars and the great fire of 1656. After the destruction of most of the city in 1656, the rebuilding was mostly in the Baroque style. The decline of Aachen culminated in 1794, when the French, led by General Charles Dumouriez, occupied Aachen. In 1542, the Dutch humanist and physician Francis Fabricius published his study of the health benefits of the hot springs in Aachen. By the middle of the 17th century, the city had developed a considerable reputation as a spa, although this was in part because Aachen was then – and remained well into the 19th century – a place of high-level prostitution. Traces of this hidden agenda of the city's history are found in the 18th-century guidebooks to Aachen as well as to the other spas. The main indication for visiting patients, ironically, was syphilis; only by the end of the 19th century had rheumatism become the most important object of cures at Aachen and Burtscheid. Aachen was chosen as the site of several important congresses and peace treaties: the first congress of Aachen (often referred to as the Congress of Aix-la-Chapelle in English) on 2 May 1668, leading to the First Treaty of Aachen in the same year which ended the War of Devolution. The second congress ended with the second treaty in 1748, ending the War of the Austrian Succession. In 1789, there was a constitutional crisis in the Aachen government, and in 1794 Aachen lost its status as a free imperial city. 19th century On 9 February 1801, the Peace of Lunéville removed the ownership of Aachen and the entire "left bank" of the Rhine from Germany (the Holy Roman Empire) and granted it to France. In 1815, control of the town was passed to the Kingdom of Prussia through an agreement reached by the Congress of Vienna. The third congress took place in 1818, to decide the fate of occupied Napoleonic France. By the middle of the 19th century, industrialisation had swept away most of the city's medieval rules of production and commerce, although the entirely corrupt remains of the city's medieval constitution were kept in place (compare the famous remarks of Georg Forster in his Ansichten vom Niederrhein) until 1801, when Aachen became the "chef-lieu du département de la Roer" in Napoleon's First French Empire. In 1815, after the Napoleonic Wars, the Kingdom of Prussia took over within the new German Confederation. The city was one of its most socially and politically backward centres until the end of the 19th century. Administered within the Rhine Province, by 1880 the population was 80,000. Starting in 1838, the railway from Cologne to Belgium passed through Aachen. The city suffered extreme overcrowding and deplorable sanitary conditions until 1875, when the medieval fortifications were finally abandoned as a limit to building and new, better housing was built in the east of the city, where sanitary drainage was easiest. In December 1880, the Aachen tramway network was opened, and in 1895 it was electrified. In the 19th century and up to the 1930s, the city was important in the production of railway locomotives and carriages, iron, pins, needles, buttons, tobacco, woollen goods, and silk goods. 20th century World War II After World War I, Aachen was occupied by the Allies until 1930, along with the rest of German territory west of the Rhine. Aachen was one of the locations involved in the ill-fated Rhenish Republic. On 21 October 1923, an armed mob took over the city hall. Similar actions took place in Mönchen-Gladbach, Duisburg, and Krefeld. This republic lasted only about a year. Aachen was heavily damaged during World War II. According to Jörg Friedrich in The Fire (2008), two Allied air raids on 11 April and 24 May 1944 "radically destroyed" the city. The first killed 1,525, including 212 children, and bombed six hospitals. During the second, 442 aircraft hit two railway stations, killed 207, and left 15,000 homeless. The raids also destroyed Aachen-Eilendorf and Aachen-Burtscheid. The city and its fortified surroundings were laid siege to from 12 September to 21 October 1944 by the US 1st Infantry Division with the 3rd Armored Division assisting from the south. Around 13 October the US 2nd Armored Division played their part, coming from the north and getting as close as Würselen, while the 30th Infantry Division played a crucial role in completing the encirclement of Aachen on 16 October 1944. With reinforcements from the US 28th Infantry Division the Battle of Aachen continued involving direct assaults through the heavily defended city, which finally forced the German garrison to surrender on 21 October 1944. Aachen was the first German city to be captured by the Western Allies, and its residents welcomed the soldiers as liberators. What remained of the city was destroyed—in some areas completely—during the fighting, mostly by American artillery fire and demolitions carried out by the Waffen-SS defenders. Damaged buildings included the medieval churches of St. Foillan, St. Paul and St. Nicholas, and the Rathaus (city hall), although Aachen Cathedral was largely unscathed. Only 4,000 inhabitants remained in the city; the rest had followed evacuation orders. Its first Allied-appointed mayor, Franz Oppenhoff, was assassinated by an SS commando unit. History of Aachen Jews During the Roman period, Aachen was the site of a flourishing Jewish community. Later, during the Carolingian empire, a Jewish community lived near the royal palace. In 797, Isaac, a Jewish merchant, accompanied two ambassadors of Charlemagne to the court of Harun al-Rashid. He returned to Aachen in July 802, bearing an elephant called Abul-Abbas as a gift for the emperor. During the 13th century, many Jews converted to Christianity, as shown in the records of the Aachen Minster (today's Cathedral). In 1486, the Jews of Aachen offered gifts to Maximilian I during his coronation ceremony. In 1629, the Aachen Jewish community was expelled from the city. In 1667, six Jews were allowed to return. Most of the Aachen Jews settled in the nearby town of Burtscheid. On 16 May 1815, the Jewish community of the city offered an homage in its synagogue to the Prussian king, Friedrich Wilhelm III. A Jewish cemetery was acquired in 1851. 1,345 Jews lived in the city in 1933. The synagogue was destroyed during Kristallnacht in 1938. In 1939, after emigration and arrests, 782 Jews remained in the city. After World War II, only 62 Jews lived there. In 2003, 1,434 Jews were living in Aachen. In Jewish texts, the city of Aachen was called Aish or Ash (אש). 21st century The city of Aachen has developed into a technology hub as a by-product of hosting one of the leading universities of technology in Germany with the RWTH Aachen (Rheinisch-Westfälische Technische Hochschule), known especially for mechanical engineering, automotive and manufacturing technology as well as for its research and academic hospital Klinikum Aachen, one of the largest medical facilities in Europe. Geography Aachen is located in the middle of the Meuse–Rhine Euroregion, close to the border tripoint of Germany, the Netherlands, and Belgium. The town of Vaals in the Netherlands lies nearby at about from Aachen's city centre, while the Dutch city of Heerlen and Eupen, the capital of the German-speaking Community of Belgium, are both located about from Aachen city centre. Aachen lies near the head of the open valley of the Wurm (which today flows through the city in canalised form), part of the larger basin of the Meuse, and about north of the High Fens, which form the northern edge of the Eifel uplands of the Rhenish Massif. The maximum dimensions of the city's territory are from north to south, and from east to west. The city limits are long, of which border Belgium and the Netherlands. The highest point in Aachen, located in the far southeast of the city, lies at an elevation of above sea level. The lowest point, in the north, and on the border with the Netherlands, is at . Climate As the westernmost city in Germany (and close to the Low Countries), Aachen and the surrounding area belongs to a temperate climate zone (Cfb), with humid weather, mild winters, and warm summers. Because of its location north of the Eifel and the High Fens and its subsequent prevailing westerly weather patterns, rainfall in Aachen (on average 805 mm/year) is comparatively higher than, for example, in Bonn (with 669 mm/year). Another factor in the local weather forces of Aachen is the occurrence of Foehn winds on the southerly air currents, which results from the city's geographic location on the northern edge of the Eifel. Because the city is surrounded by hills, it suffers from inversion-related smog. Some areas of the city have become urban heat islands as a result of poor heat exchange, both because of the area's natural geography and from human activity. The city's numerous cold air corridors, which are slated to remain as free as possible from new construction, therefore play an important role in the urban climate of Aachen. The January average is , while the July average is . Precipitation is almost evenly spread throughout the year. Geology The geology of Aachen is very structurally heterogeneous. The oldest occurring rocks in the area surrounding the city originate from the Devonian period and include carboniferous sandstone, greywacke, claystone and limestone. These formations are part of the Rhenish Massif, north of the High Fens. In the Pennsylvanian subperiod of the Carboniferous geological period, these rock layers were narrowed and folded as a result of the Variscan orogeny. After this event, and over the course of the following 200 million years, this area has been continuously flattened. During the Cretaceous period, the ocean penetrated the continent from the direction of the North Sea up to the mountainous area near Aachen, bringing with it clay, sand, and chalk deposits. While the clay (which was the basis for a major pottery industry in nearby Raeren) is mostly found in the lower areas of Aachen, the hills of the Aachen Forest and the Lousberg were formed from upper Cretaceous sand and chalk deposits. More recent sedimentation is mainly located in the north and east of Aachen and was formed through tertiary and quaternary river and wind activities. Along the major thrust fault of the Variscan orogeny, there are over 30 thermal springs in Aachen and Burtscheid. Additionally, the subsurface of Aachen is traversed by numerous active faults that belong to the Rurgraben fault system, which has been responsible for numerous earthquakes in the past, including the 1756 Düren earthquake and the 1992 Roermond earthquake, which was the strongest earthquake ever recorded in the Netherlands. Demographics Aachen has 245,885 inhabitants (as of 31 December 2015), of whom 118,272 are female, and 127,613 are male. The unemployment rate in the city is, as of April 2012, 9.7 percent. At the end of 2009, the foreign-born residents of Aachen made up 13.6 percent of the total population. A significant portion of foreign residents are students at the RWTH Aachen University. Boroughs The city is divided into seven administrative districts, or boroughs, each with its own district council, district leader, and district authority. The councils are elected locally by those who live within the district, and these districts are further subdivided into smaller sections for statistical purposes, with each sub-district named by a two-digit number. The districts of Aachen, including their constituent statistical districts, are: Aachen-Mitte: 10 Markt, 13 Theater, 14 Lindenplatz, 15 St. Jakob, 16 Westpark, 17 Hanbruch, 18 Hörn, 21 Ponttor, 22 Hansemannplatz, 23 Soers, 24 Jülicher Straße, 25 Kalkofen, 31 Kaiserplatz, 32 Adalbertsteinweg, 33 Panneschopp, 34 Rothe Erde, 35 Trierer Straße, 36 Frankenberg, 37 Forst, 41 Beverau, 42 Burtscheid Kurgarten, 43 Burtscheid Abbey, 46 Burtscheid Steinebrück, 47 Marschiertor, 48 Hangeweiher Brand: 51 Brand Eilendorf: 52 Eilendorf Haaren: 53 Haaren (including Verlautenheide) Kornelimünster/Walheim: 61 Kornelimünster, 62 Oberforstbach, 63 Walheim Laurensberg: 64 Vaalserquartier, 65 Laurensberg Richterich: 88 Richterich Regardless of official statistical designations, there are 50 neighbourhoods and communities within Aachen, here arranged by district: Aachen-Mitte: Beverau, Bildchen, Burtscheid, Forst, Frankenberg, Grüne Eiche, Hörn, Lintert, Pontviertel, Preuswald, Ronheide, Rosviertel, Rothe Erde, Stadtmitte, Steinebrück, West Brand: Brand, Eich, Freund, Hitfeld, Niederforstbach Eilendorf: Eilendorf, Nirm Haaren: Haaren, Hüls, Verlautenheide Kornelimünster/Walheim: Friesenrath, Hahn, Kitzenhaus, Kornelimünster, Krauthausen, Lichtenbusch, Nütheim, Oberforstbach, Sief, Schleckheim, Schmithof, Walheim Laurensberg: Gut Kullen, Kronenberg, Laurensberg, Lemiers, Melaten, Orsbach, Seffent, Soers, Steppenberg, Vaalserquartier, Vetschau Richterich: Horbach, Huf, Richterich Neighbouring communities The following cities and communities border Aachen, clockwise from the northwest: Herzogenrath, Würselen, Eschweiler, Stolberg and Roetgen (which are all in the district of Aachen); Raeren, Kelmis and Plombières (Liège Province in Belgium) as well as Vaals, Gulpen-Wittem, Simpelveld, Heerlen and Kerkrade (all in Limburg Province in the Netherlands). Politics Mayor The current Mayor of Aachen is Sibylle Keupen, an independent endorsed by Alliance 90/The Greens, since 2020. The most recent mayoral election was held on 13 September 2020, with a runoff held on 27 September, and the results were as follows: ! rowspan=2 colspan=2| Candidate ! rowspan=2| Party ! colspan=2| First round ! colspan=2| Second round |- ! Votes ! % ! Votes ! % |- | bgcolor=| | align=left| Sibylle Keupen | align=left| Independent (Green) | 39,662 | 38.9 | 53,685 | 67.4 |- | bgcolor=| | align=left| Harald Baal | align=left| Christian Democratic Union | 25,253 | 24.8 | 26,003 | 32.6 |- | bgcolor=| | align=left| Mathias Dopatka | align=left| Social Democratic Party | 23,031 | 22.6 |- | bgcolor=| | align=left| Markus Mohr | align=left| Alternative for Germany | 3,387 | 3.3 |- | bgcolor=| | align=left| Wilhelm Helg | align=left| Free Democratic Party | 3,122 | 3.1 |- | bgcolor=| | align=left| Leo Deumens | align=left| The Left | 2,397 | 2.4 |- | bgcolor=| | align=left| Hubert vom Venn | align=left| Die PARTEI | 2,112 | 2.1 |- | bgcolor=| | align=left| Jörg Polzin | align=left| Independent | 938 | 0.9 |- | | align=left| Ralf Haupts | align=left| Independent Voters' Association Aachen | 932 | 0.9 |- | bgcolor=| | align=left| Matthias Achilles | align=left| Pirate Party Germany | 848 | 0.8 |- | bgcolor=| | align=left| Adonis Böving | align=left| Independent | 317 | 0.3 |- ! colspan=3| Valid votes ! 101,999 ! 99.2 ! 79,688 ! 99.3 |- ! colspan=3| Invalid votes ! 819 ! 0.8 ! 532 ! 0.7 |- ! colspan=3| Total ! 102,818 ! 100.0 ! 80,220 ! 100.0 |- ! colspan=3| Electorate/voter turnout ! 192,502 ! 53.4 ! 192,435 ! 41.7 |- | colspan=7| Source: State Returning Officer |} City council The Aachen city council governs the city alongside the Mayor. The most recent city council election was held on 13 September 2020, and the results were as follows: ! colspan=2| Party ! Votes ! % ! +/- ! Seats ! +/- |- | bgcolor=| | align=left| Alliance 90/The Greens (Grüne) | 34,712 | 34.1 | 17.5 | 20 | 7 |- | bgcolor=| | align=left| Christian Democratic Union (CDU) | 25,268 | 24.8 | 11.5 | 14 | 14 |- | bgcolor=| | align=left| Social Democratic Party (SPD) | 18,676 | 18.3 | 7.7 | 11 | 9 |- | bgcolor=| | align=left| Free Democratic Party (FDP) | 5,042 | 4.9 | 0.5 | 3 | ±0 |- | bgcolor=| | align=left| The Left (Die Linke) | 4,694 | 4.6 | 1.5 | 3 | 2 |- | bgcolor=| | align=left| Alternative for Germany (AfD) | 3,816 | 3.7 | 1.2 | 2 | ±0 |- | bgcolor=| | align=left| Volt Germany (Volt) | 3,784 | 3.7 | New | 2 | New |- | bgcolor=| | align=left| Die PARTEI (PARTEI) | 2,295 | 2.3 | 1.8 | 1 | 1 |- | | align=left| Independent Voters' Association Aachen (UWG) | 1,632 | 1.6 | 0.2 | 1 | ±0 |- | bgcolor=| | align=left| Pirate Party Germany (Piraten) | 1,226 | 1.2 | 2.2 | 1 | 2 |- | colspan=7 bgcolor=lightgrey| |- | bgcolor=| | align=left| Ecological Democratic Party (ÖDP) | 673 | 0.7 | New | 0 | New |- | | align=left| Voter Group | 45 | 0.0 | New | 0 | New |- ! colspan=2| Valid votes ! 101,863 ! 99.1 ! ! ! |- ! colspan=2| Invalid votes ! 918 ! 0.9 ! ! ! |- ! colspan=2| Total ! 102,781 ! 100.0 ! ! 58 ! 18 |- ! colspan=2| Electorate/voter turnout ! 192,502 ! 53.4 ! 0.7 ! ! |- | colspan=7| Source: State Returning Officer |} Main sights Cathedral Aachen Cathedral was erected on the orders of Charlemagne. Construction began c. AD 796, and it was, on completion c. 798, the largest cathedral north of the Alps. It was modelled after the Basilica of San Vitale, in Ravenna, Italy, and was built by Odo of Metz. Charlemagne also desired for the chapel to compete with the Lateran Palace, both in quality and authority. It was originally built in the Carolingian style, including marble covered walls, and mosaic inlay on the dome. On his death, Charlemagne's remains were interred in the cathedral and can be seen there to this day. The cathedral was extended several times in later ages, turning it into a curious and unique mixture of building styles. The throne and gallery portion date from the Ottonian, with portions of the original opus sectile floor still visible. The 13th century saw gables being added to the roof, and after the fire of 1656, the dome was rebuilt. Finally, a choir was added around the start of the 15th century. After Frederick Barbarossa canonised Charlemagne in 1165 the chapel became a destination for pilgrims. For 600 years, from 936 to 1531, Aachen Cathedral was the church of coronation for 30 German kings and 12 queens. The church built by Charlemagne is still the main attraction of the city. In addition to holding the remains of its founder, it became the burial place of his successor Otto III. In the upper chamber of the gallery, Charlemagne's marble throne is housed. Aachen Cathedral has been designated as a UNESCO World Heritage Site. Most of the marble and columns used in the construction of the cathedral were brought from Rome and Ravenna, including the sarcophagus in which Charlemagne was eventually laid to rest. A bronze bear from Gaul was placed inside, along with an equestrian statue from Ravenna, believed to be Theodric, in contrast to a wolf and a statue of Marcus Aurelius in the Capitoline. Bronze pieces such as the doors and railings, some of which have survived to present day, were cast in a local foundry. Finally, there is uncertainty surrounding the bronze pine cone in the chapel, and where it was created. Wherever it was made, it was also a parallel to a piece in Rome, this in Old St. Peter's Basilica. Cathedral Treasury Aachen Cathedral Treasury has housed, throughout its history, a collection of liturgical objects. The origin of this church treasure is in dispute as some say Charlemagne himself endowed his chapel with the original collection, while the rest were collected over time. Others say all of the objects were collected over time, from such places as Jerusalem and Constantinople. The location of this treasury has moved over time and was unknown until the 15th century when it was located in the Matthiaskapelle (St. Matthew's Chapel) until 1873, when it was moved to the Karlskapelle (Charles' Chapel). From there it was moved to the Hungarian Chapel in 1881 and in 1931 to its present location next to the Allerseelenkapelle (Poor Souls' Chapel). Only six of the original Carolingian objects have remained, and of those only three are left in Aachen: the Aachen Gospels, a diptych of Christ, and an early Byzantine silk. The Coronation Gospels and a reliquary burse of St. Stephen were moved to Vienna in 1798 and the Talisman of Charlemagne was given as a gift in 1804 to Josephine Bonaparte and subsequently to Rheims Cathedral. 210 documented pieces have been added to the treasury since its inception, typically to receive in return legitimisation of linkage to the heritage of Charlemagne. The Lothar Cross, the Gospels of Otto III and multiple additional Byzantine silks were donated by Otto III. Part of the Pala d'Oro and a covering for the Aachen Gospels were made of gold donated by Henry II. Frederick Barbarossa donated the candelabrum that adorns the dome and also once "crowned" the Shrine of Charlemagne, which was placed underneath in 1215. Charles IV donated a pair of reliquaries. Louis XI gave, in 1475, the crown of Margaret of York, and, in 1481, another arm reliquary of Charlemagne. Maximilian I and Charles V both gave numerous works of art by Hans von Reutlingen. Continuing the tradition, objects continued to be donated until the present, each indicative of the period of its gifting, with the last documented gift being a chalice from 1960 made by Ewald Mataré. Rathaus The Aachen Rathaus, (English: Aachen City Hall or Aachen Town Hall) dated from 1330, lies between two central squares, the Markt (marketplace) and the Katschhof (between city hall and cathedral). The coronation hall is on the first floor of the building. Inside one can find five frescoes by the Aachen artist Alfred Rethel which show legendary scenes from the life of Charlemagne, as well as Charlemagne's signature. Also, precious replicas of the Imperial Regalia are kept here. Since 2009, the city hall has been a station on the Route Charlemagne, a tour programme by which historical sights of Aachen are presented to visitors. At the city hall, a museum exhibition explains the history and art of the building and gives a sense of the historical coronation banquets that took place there. A portrait of Napoleon from 1807 by Louis-André-Gabriel Bouchet and one of his wife Joséphine from 1805 by Robert Lefèvre are viewable as part of the tour. As before, the city hall is the seat of the mayor of Aachen and of the city council, and annually the Charlemagne Prize is awarded there. Other sights The Grashaus, a late medieval house at the Fischmarkt, is one of the oldest non-religious buildings in central Aachen. It hosted the city archive, and before that, the Grashaus was the city hall until the present building took over this function. The Elisenbrunnen is one of the most famous sights of Aachen. It is a neo-classical hall covering one of the city's famous fountains. It is just a minute away from the cathedral. Just a few steps in a south-easterly direction lies the 19th-century theatre. Also of note are two remaining city gates, the Ponttor (Pont gate), northwest of the cathedral, and the Marschiertor (marching gate), close to the central railway station. There are also a few parts of both medieval city walls left, most of them integrated into more recent buildings, but some others still visible. There are even five towers left, some of which are used for housing. St. Michael's Church, Aachen was built as a church of the Aachen Jesuit Collegium in 1628. It is attributed to the Rhine mannerism, and a sample of a local Renaissance architecture. The rich façade remained unfinished until 1891, when the architect Peter Friedrich Peters added to it. The church is a Greek Orthodox church today, but the building is used also for concerts because of its good acoustics. The synagogue in Aachen, which was destroyed on the Night of Broken Glass (Kristallnacht), 9 November 1938, was reinaugurated on 18 May 1995. One of the contributors to the reconstructions of the synagogue was Jürgen Linden, the Lord Mayor of Aachen from 1989 to 2009. There are numerous other notable churches and monasteries, a few remarkable 17th- and 18th-century buildings in the particular Baroque style typical of the region, a synagogue, a collection of statues and monuments, park areas, cemeteries, among others. Among the museums in the town are the Suermondt-Ludwig Museum, which has a fine sculpture collection and the Aachen Museum of the International Press, which is dedicated to newspapers from the 16th century to the present. The area's industrial history is reflected in dozens of 19th- and early 20th-century manufacturing sites in the city. Economy Aachen is the administrative centre for the coal-mining industries in neighbouring places to the northeast. Products manufactured in Aachen include electrical goods, textiles, foodstuffs (chocolate and candy), glass, machinery, rubber products, furniture, metal products. Also in and around Aachen chemicals, plastics, cosmetics, and needles and pins are produced. Though once a major player in Aachen's economy, today glassware and textile production make up only 10% of total manufacturing jobs in the city. There have been a number of spin-offs from the university's IT technology department. Electric vehicle manufacturing In June 2010, Achim Kampker, together with Günther Schuh, founded a small company to develop Street Scooter GmbH; in August 2014, it was renamed StreetScooter GmbH. This was a privately organised research initiative at the RWTH Aachen University which later became an independent company in Aachen. Kampker was also the founder and chairman of the European Network for Affordable and Sustainable Electromobility. In May 2014, the company announced that the city of Aachen, the city council Aachen and the savings bank Aachen had ordered electric vehicles from the company. In late 2014, approximately 70 employees were manufacturing 200 vehicles annually in the premises of the Waggonfabrik Talbot, the former Talbot/Bombardier plant in Aachen. In December 2014 Deutsche Post DHL Group purchased the StreetScooter company, which became its wholly owned subsidiary. By April 2016, the company announced that it would produce 2000 of its electric vans branded Work in Aachen by the end of the year. In 2015, the electric vehicle start-up e.GO Mobile was founded by Günther Schuh, which started producing the e.GO Life electric passenger car and other vehicles in April 2019. In April 2016, StreetScooter GmbH announced that it would be scaling up to manufacture approximately 10,000 of the Work vehicles annually, starting in 2017, also in Aachen. If that goal is achieved, it will become the largest electric light utility vehicle manufacturer in Europe, surpassing Renault which makes the smaller Kangoo Z.E.. Culture In 1372, Aachen became the first coin-minting city in the world to regularly place an Anno Domini date on a general circulation coin, a groschen. The Scotch Club in Aachen was the first discothèque in Germany, opened from 19 October 1959 until 1992. Klaus Quirini as DJ Heinrich was the first DJ ever. The thriving Aachen black metal scene is among the most notable in Germany, with such bands as Nagelfar, The Ruins of Beverast, Graupel and Verdunkeln. The local speciality of Aachen is an originally hard type of sweet bread, baked in large flat loaves, called Aachener Printen. Unlike Lebkuchen, a German form of gingerbread sweetened with honey, Printen use a syrup made from sugar. Today, a soft version is sold under the same name which follows an entirely different recipe. Asteroid 274835 Aachen, discovered by amateur astronomer Erwin Schwab in 2009, was named after the city. The official was published by the Minor Planet Center on 8 November 2019 (). Education RWTH Aachen University, established as Polytechnicum in 1870, is one of Germany's Universities of Excellence with strong emphasis on technological research, especially for electrical and mechanical engineering, computer sciences, physics, and chemistry. The university clinic attached to the RWTH, the Klinikum Aachen, is the biggest single-building hospital in Europe. Over time, a host of software and computer industries have developed around the university. It also maintains a botanical garden (the Botanischer Garten Aachen). FH Aachen, Aachen University of Applied Sciences (AcUAS) was founded in 1971. The AcUAS offers a classic engineering education in professions such as mechatronics, construction engineering, mechanical engineering or electrical engineering. German and international students are educated in more than 20 international or foreign-oriented programmes and can acquire German as well as international degrees (Bachelor/Master) or Doppelabschlüsse (double degrees). Foreign students account for more than 21% of the student body. The Katholische Hochschule Nordrhein-Westfalen – Abteilung Aachen (Catholic University of Applied Sciences Northrhine-Westphalia – Aachen department) offers its some 750 students a variety of degree programmes: social work, childhood education, nursing, and co-operative management. It also has the only programme of study in Germany especially designed for mothers. The Hochschule für Musik und Tanz Köln (Cologne University of Music) is one of the world's foremost performing arts schools and one of the largest music institutions for higher education in Europe with one of its three campuses in Aachen. The Aachen campus substantially contributes to the Opera/Musical Theatre master's programme by collaborating with the Theater Aachen and the recently established musical theatre chair through the Rheinische Opernakademie. The German army's Technical School (Ausbildungszentrum Technik Landsysteme) is in Aachen. Sports The annual CHIO (short for the French term Concours Hippique International Officiel) is the biggest equestrian meeting of the world and among horsemen is considered to be as prestigious for equitation as the tournament of Wimbledon for tennis. Aachen hosted the 2006 FEI World Equestrian Games. The local football team Alemannia Aachen had a short run in Germany's first division, after its promotion in 2006. However, the team could not sustain its status and is now back in the fourth division. The stadium "Tivoli", opened in 1928, served as the venue for the team's home games and was well known for its incomparable atmosphere throughout the whole of the second division. Before the old stadium's demolition in 2011, it was used by amateurs, whilst the Bundesliga Club held its games in the new stadium "Neuer Tivoli" – meaning New Tivoli—a couple of metres down the road. The building work for the stadium which has a capacity of 32,960, began in May 2008 and was completed by the beginning of 2009. The Ladies in Black women's volleyball team (part of the "PTSV Aachen" sports club since 2013) has played in the first German volleyball league (DVL) since 2008. Transport Rail Aachen's railway station, the Hauptbahnhof (Central Station), was constructed in 1841 for the Cologne–Aachen railway line. In 1905 it was moved closer to the city centre. It serves main lines to Cologne, Mönchengladbach and Liège as well as branch lines to Heerlen, Alsdorf, Stolberg and Eschweiler. ICE high speed trains from Brussels via Cologne to Frankfurt am Main and Thalys trains from Paris to Cologne also stop at Aachen Central Station. Four RE lines and two RB lines connect Aachen with the Ruhrgebiet, Mönchengladbach, Spa (Belgium), Düsseldorf and the Siegerland. The Euregiobahn, a regional railway system, reaches several minor cities in the Aachen region. There are four smaller stations in Aachen: Aachen West, Aachen Schanz, Aachen-Rothe Erde and Eilendorf. Slower trains stop at these. Aachen West has gained in importance with the expansion of RWTH Aachen University. Intercity bus stations There are two stations for intercity bus services in Aachen: Aachen West station, in the north-west of the city, and Aachen Wilmersdorfer Straße, in the north-east. Public transport The first horse tram line in Aachen opened in December 1880. After electrification in 1895, it attained a maximum length of in 1915, becoming the fourth-longest tram network in Germany. Many tram lines extended to the surrounding towns of Herzogenrath, Stolberg, Alsdorf as well as the Belgian and Dutch communes of Vaals, Kelmis (then Altenberg) and Eupen. The Aachen tram system was linked with the Belgian national interurban tram system. Like many tram systems in Western Europe, the Aachen tram suffered from poorly-maintained infrastructure and was so deemed unnecessary and disrupting for car drivers by local politics. On 28 September 1974 the last line 15 (Vaals–Brand) operated for one last day and was then replaced by buses. A proposal to reinstate a tram/light rail system under the name Campusbahn was dropped after a referendum. Today, the ASEAG (Aachener Straßenbahn und Energieversorgungs-AG, literally "Aachen tram and power supply company") operates a bus network with 68 bus routes. Because of the location at the border, many bus routes extend to Belgium and the Netherlands. Lines 14 to Eupen, Belgium and 44 to Heerlen, Netherlands are jointly operated with Transport en Commun and Veolia Transport Nederland, respectively. ASEAG is one of the main participants in the Aachener Verkehrsverbund (AVV), a tariff association in the region. Along with ASEAG, city bus routes of Aachen are served by private contractors such as Sadar, Taeter, Schlömer, or DB Regio Bus. Line 350, which runs from Maastricht, also enters Aachen. Roads Aachen is connected to the Autobahn A4 (west-east), A44 (north-south) and A544 (a smaller motorway from the A4 to the Europaplatz near the city centre). There are plans to eliminate traffic jams at the Aachen road interchange. Airport Maastricht Aachen Airport is the main airport of Aachen and Maastricht. It is located around 15 nautical miles (28 km; 17 mi) northwest of Aachen. There is a shuttle-service between Aachen and the airport. Recreational aviation is served by the (formerly military) Aachen Merzbrück Airfield. Charlemagne Prize Since 1950, a committee of Aachen citizens annually awards the Charlemagne Prize () to personalities of outstanding service to the unification of Europe. It is traditionally awarded on Ascension Day at the City Hall. In 2016, the Charlemagne Award was awarded to Pope Francis. The International Charlemagne Prize of Aachen was awarded in the year 2000 to US president Bill Clinton, for his special personal contribution to co-operation with the states of Europe, for the preservation of peace, freedom, democracy and human rights in Europe, and for his support of the enlargement of the European Union. In 2004, Pope John Paul II's efforts to unite Europe were honoured with an "Extraordinary Charlemagne Medal", which was awarded for the only time ever. Literature Aix is the destination in Robert Browning's poem "How They Brought the Good News from Ghent to Aix", which was published in Dramatic Romances and Lyrics, 1845. The poem is a first-person narrative told, in breathless galloping meter, by one of three riders; an urgent midnight errand to deliver —"the news which alone could save Aix from her fate". Notable people Twin towns – sister cities Aachen is twinned with: Montebourg, France (1960) Reims, France (1967) Halifax, England (1979) Toledo, Spain (1985) Ningbo, China (1986) Naumburg, Germany (1988) Arlington County, United States (1993) Kostroma, Russia (2005) Sarıyer, Istanbul, Turkey (2013) Cape Town, South Africa (2017) See also Aachen (district) Aachen Prison Aachen tram Aachener Aachener Chronik Aachener Bachverein List of mayors of Aachen Council of Aachen Treaty of Aix-la-Chapelle (disambiguation) Maastricht Aachen Airport Notes References Sources Further reading External links Aachen (district) Belgium–Germany border crossings Catholic pilgrimage sites Cities in North Rhine-Westphalia 1st century Free imperial cities Jewish German history Matter of France Populated places established in the 1st century Rhineland Roman towns and cities in Germany 765 Spa towns in Germany

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1576

https://en.wikipedia.org/wiki/Afonso%20de%20Albuquerque

Afonso de Albuquerque

Afonso de Albuquerque, 1st Duke of Goa (; 1453 – 16 December 1515) was a Portuguese general, admiral, and statesman. He served as viceroy of Portuguese India from 1509 to 1515, during which he expanded Portuguese influence across the Indian Ocean and built a reputation as a fierce and skilled military commander. Albuquerque advanced the three-fold Portuguese grand scheme of combating Islam, spreading Christianity, and securing the trade of spices by establishing a Portuguese Asian empire. Among his achievements, Albuquerque managed to conquer Goa and was the first European of the Renaissance to raid the Persian Gulf, and he led the first voyage by a European fleet into the Red Sea. He is generally considered a highly effective military commander, and "probably the greatest naval commander of the age", given his successful strategy — he attempted to close all the Indian Ocean naval passages to the Atlantic, Red Sea, Persian Gulf, and to the Pacific, transforming it into a Portuguese mare clausum. He was appointed head of the "fleet of the Arabian and Persian sea" in 1506. Many of the conflicts in which he was directly involved took place in the Indian Ocean, in the Persian Gulf regions for control of the trade routes, and on the coasts of India. It was his military brilliance in these initial campaigns that enabled Portugal to become the first global empire in history. He led the Portuguese forces in numerous battles, including the conquest of Goa in 1510 and the capture of Malacca in 1511. During the last five years of his life, he turned to administration, where his actions as the second governor of Portuguese India were crucial to the longevity of the Portuguese Empire. He oversaw the expeditions that resulted in the establishment of diplomatical contacts with Thailand through his envoy Duarte Fernandes, with Pegu in Myanmar, with Timor and the Moluccas through a voyage headed by António de Abreu and Francisco Serrão and laid the path for European trade with Ming China through Rafael Perestrello. He also aided in establishing diplomatic relations with Ethiopia, and established diplomatic ties with Persia during the Safavid dynasty. Throughout his career, he received epithets such as "the Terrible", "the Great", "the Lion of the Seas", "the Portuguese Mars", and "the Caesar of the East". Early life Afonso de Albuquerque was born in 1453 in Alhandra, near Lisbon. He was the second son of Gonçalo de Albuquerque, Lord of Vila Verde dos Francos, and Dona Leonor de Menezes. His father held an important position at court and was connected by remote illegitimate descent with the Portuguese monarchy. He was a descendant of King Denis’s illegitimate son, Afonso Sanches, Lord of Albuquerque. He was educated in mathematics and Latin at the court of Afonso V of Portugal, where he befriended Prince John, the future King John II of Portugal. Early military service In 1471, under the command of Afonso V, he was present at the conquest of Tangier and Arzila in Morocco, serving there as an officer for some years. In 1476 he accompanied Prince John in wars against Castile, including the Battle of Toro. He participated in the campaign on the Italian peninsula in 1480 to assist Ferdinand I of Naples in repelling the Ottoman invasion of Otranto. On his return in 1481, when Prince John was crowned as King John II, Albuquerque was made Master of the Horse and chief equerry (estribeiro-mor) to the King, a post which he held throughout John's reign. In 1489 he returned to military campaigning in North Africa, as commander of defense in the Graciosa fortress, an island in the river Luco near the city of Larache. In 1490 Albuquerque was part of the guard of King John II. He returned to Arzila in 1495, where his younger brother Martim died fighting by his side. First expedition to India, 1503 When King Manuel I of Portugal ascended to the throne following the death of John, he held a cautious attitude towards Albuquerque, who was a close friend of his predecessor and seventeen years Manuel's senior. Eight years later, on 6 April 1503 Albuquerque was sent on his first expedition to India together with his cousin Francisco de Albuquerque. Each commanded three ships, sailing with Duarte Pacheco Pereira and Nicolau Coelho. They engaged in several battles against the forces of the Zamorin of Calicut (Calecute, Kozhikode) and succeeded in establishing the King of Cochin (Cohim, Kochi) securely on his throne. In return, the King gave them permission to build the Portuguese fort Immanuel (Fort Kochi) and establish trade relations with Quilon (Coulão, Kollam). This laid the foundation for the eastern Portuguese Empire. Second expedition to India, 1506 Albuquerque returned home in July 1504, and was well received by King Manuel I. After he assisted with the creation of a strategy for the Portuguese efforts in the east, King Manuel entrusted him with the command of a squadron of five vessels in the fleet of sixteen sailing for India in early 1506, headed by Tristão da Cunha. The aim of the expedition was to conquer Socotra and build a fortress there, hoping to close the trade in the Red Sea. Albuquerque went as "chief-captain for the Coast of Arabia", sailing under da Cunha's orders until reaching Mozambique. He carried a sealed letter with a secret mission ordered by the King: after fulfilling the first mission, he was to replace the first viceroy of India, Francisco de Almeida, whose term ended two years later. Before departing, he legitimized his son Brás ("Braz" in the old Portuguese spelling, born to a common Portuguese woman named Joana Vicente in 1500), and made his will. First conquest of Socotra and Ormuz, 1507 The fleet left Lisbon on 6 April 1506. Albuquerque piloted his ship himself, having lost his appointed pilot on departure. In Mozambique Channel, they rescued Captain João da Nova, who had encountered difficulties on his return from India; da Nova and his ship, the Frol de la mar, joined da Cunha's fleet. From Malindi, da Cunha sent envoys to Ethiopia, which at the time was thought to be closer to India than it actually is, under the aegis of Albuquerque. After failing to reach Ethiopia, he managed to land the envoys in Filuk. After successful attacks on Arab cities on the East African coast, the expedition conquered the island of Socotra and built a fortress at Suq, hoping to establish a base to stop the Red Sea commerce to the Indian Ocean. However, Socotra was abandoned four years later, as it was eventually realised to be a poor location for a base. At Socotra, they parted ways: Tristão da Cunha sailed for India, where he would relieve the Portuguese besieged at Cannanore, while Afonso took seven ships and 500 men to Ormuz in the Persian Gulf, one of the chief eastern centers of commerce. On his way, he conquered the cities of Curiati (Kuryat), Muscat in July 1507, and Khor Fakkan, accepting the submission of the cities of Kalhat and Sohar. He arrived at Ormuz on 25 September and soon captured the city, which agreed to become a tributary state of the Portuguese king. Hormuz was then a tributary state of Shah Ismail of Persia. In a famous episode, shortly after its conquest Albuquerque was confronted by Persian envoys, who demanded the payment of the due tribute from him instead. He ordered them to be given a stock of cannonballs, arrows and weapons, retorting that "such was the currency struck in Portugal to pay the tribute demanded from the dominions of King Manuel". According to Brás de Albuquerque, it was Shah Ismael who coined the term "Lion of the seas", addressing Albuquerque as such. Afonso began building the Fort of Our Lady of Victory (later renamed Fort of Our Lady of the Conception), engaging his men of all ranks in the work. However, some of his officers revolted against the heavy work and climate and, claiming that Afonso was exceeding his orders, departed for India. With the fleet reduced to two ships and left without supplies, he was unable to maintain his position for long. Forced to abandon Ormuz in January 1508, he raided coastal villages to resupply the settlement of Socotra, returned to Ormuz, and then headed to India. Arrest at Cannanore, 1509 Afonso arrived at Cannanore on the Malabar coast in December 1508, where he opened before the viceroy, Dom Francisco de Almeida, the sealed letter which he had received from the King, and which named him as governor to succeed Almeida. The viceroy, supported by the officers who had abandoned Afonso at Ormuz, had a matching royal order, but declined to yield, protesting that his term ended only in January and stating his intention to avenge his son's death by fighting the Mamluk fleet of Mirocem, refusing Afonso's offer to fight the Mamluk fleet himself. Afonso avoided confrontation, which could have led to civil war, and moved to Kochi, India, to await further instruction from the King, maintaining his own entourage. Increasingly isolated, he wrote to Diogo Lopes de Sequeira, who arrived in India with a new fleet, but was ignored as Sequeira joined Almeida. At the same time, Afonso refused approaches from opponents of Almeida who encouraged him to seize power. On 3 February 1509, Almeida fought the naval Battle of Diu against a joint fleet of Mamluks, Ottomans, the Zamorin of Calicut, and the Sultan of Gujarat, regarding it as personal revenge for the death of his son. His victory was decisive: the Ottomans and Mamluks abandoned the Indian Ocean, easing the way for Portuguese rule there for the next century. In August, after a petition from Afonso's former officers with the support of Diogo Lopes de Sequeira claiming him unfit for governance, Afonso was sent in custody to St. Angelo Fort in Cannanore. There he remained under what he considered to be imprisonment. Governor of Portuguese India, 1509–1515 Afonso was released after three months' confinement, on the arrival at Cannanore of Marshal of Portugal Fernando Coutinho with a large fleet. Coutinho was the most important Portuguese noble ever to visit India up to that point, and he brought an armada of fifteen ships and 3,000 men sent by the King to defend Afonso's rights, and to take Calicut. On 4 November 1509, Afonso became the second Governor of Portuguese India, a position he would hold until his death. Almeida set off to return to Portugal, though he would be killed before he got there in a skirmish with the Khoekhoe. Upon his assuming office, Afonso intended to dominate the Muslim world and control the Spice trade. Initially King Manuel I and his council in Lisbon tried to distribute the power, outlining three areas of jurisdiction in the Indian Ocean. In 1509, the nobleman Diogo Lopes de Sequeira was sent with a fleet to Southeast Asia, to seek an agreement with Sultan Mahmud Shah of Malacca, but failed and returned to Portugal. To Jorge de Aguiar was given the region between the Cape of Good Hope and Gujarat. He was succeeded by Duarte de Lemos, but left for Cochin and then for Portugal, leaving his fleet to Afonso. Conquest of Goa, 1510 In January 1510, obeying the orders from the King and aware of the absence of the Zamorin, Afonso advanced on Calicut. The attack was initially successful, but unravelled when Marshal Coutinho, infuriated by Albuquerque's success against Calicut and desiring glory for himself, attacked the Zamorin's palace against Albuquerque's advice, and was ambushed. During the retreat, Afonso was badly wounded and was forced to flee to the ships, barely escaping with his life, while Coutinho was killed. Soon after the failed attack, Afonso assembled a fleet of 23 ships and 1200 men. Contemporary reports state that he wanted to fight the Egyptian Mamluk Sultanate fleet in the Red Sea or return to Hormuz. However, he had been informed by Timoji (a privateer in the service of the Hindu Vijayanagara Empire) that it would be easier to fight them in Goa, where they had sheltered after the Battle of Diu, and also of the illness of the Sultan Yusuf Adil Shah, and war between the Deccan sultanates. So he relied on surprise in the capture of Goa from the Sultanate of Bijapur. A first assault took place in Goa from 4 March to 20 May 1510. After initial occupation, feeling unable to hold the city given the poor condition of its fortifications, the cooling of Hindu residents' support and insubordination among his ranks following an attack by Ismail Adil Shah, Afonso refused a truce offered by the Sultan and abandoned the city in August. His fleet was scattered, and a palace revolt in Kochi hindered his recovery, so he headed to Fort Anjediva. New ships arrived from Portugal, which were intended for the nobleman Diogo Mendes de Vasconcelos at Malacca, who had been given a rival command of the region. Three months later, on 25 November Afonso reappeared at Goa with a renovated fleet. Diogo Mendes de Vasconcelos was compelled to accompany him with the reinforcements for Malacca and about 300 Malabari reinforcements from Cannanore. In less than a day, they took Goa from Ismail Adil Shah and his Ottoman allies, who surrendered on 10 December. It is estimated that 6000 of the 9000 Muslim defenders of the city died, either in the fierce battle in the streets or by drowning while trying to escape. Afonso regained the support of the Hindu population, although he frustrated the initial expectations of Timoji, who aspired to become governor. Afonso rewarded him by appointing him chief "Aguazil" of the city, an administrator and representative of the Hindu and Muslim people, as a knowledgeable interpreter of the local customs. He then made an agreement to lower the yearly tribute. In Goa, Afonso established the first Portuguese mint in the East, after Timoja's merchants had complained of the scarcity of currency, taking it as an opportunity to solidify the territorial conquest. The new coin, based on the existing local coins, showed a cross on the obverse and an armillary sphere (or "esfera"), King Manuel's badge, on the reverse. Gold cruzados or manueis, silver esferas and alf-esferas, and bronze "leais" were issued. Albuquerque founded at Goa the Hospital Real de Goa or Royal Hospital of Goa, by the Church of Santa Catarina. Upon hearing that the doctors were extorting the sickly with excessive fees, Albuquerque summoned them, declaring that "You charge a physicians' pay and don't know what disease the men who serve our lord the King suffer from. Thus, I want to teach you what is it that they die from" and put them to work building the city walls all day till nightfall before releasing them. Despite constant attacks, Goa became the center of Portuguese India, with the conquest triggering the compliance of neighbouring kingdoms: the Sultan of Gujarat and the Zamorin of Calicut sent embassies, offering alliances and local grants to fortify. Afonso then used Goa to secure the Spice trade in favor of Portugal and sell Persian horses to Vijayanagara and Hindu princes in return for their assistance. Conquest of Malacca, 1511 Afonso explained to his armies why the Portuguese wanted to capture Malacca: "The King of Portugal has often commanded me to go to the Straits, because...this was the best place to intercept the trade which the Moslems...carry on in these parts. So it was to do Our Lord's service that we were brought here; by taking Malacca, we would close the Straits so that never again would the Moslems be able to bring their spices by this route.... I am very sure that, if this Malacca trade is taken out of their hands, Cairo and Mecca will be completely lost." (The Commentaries of the Great Afonso de Albuquerque) In February 1511, through a friendly Hindu merchant, Nina Chatu, Afonso received a letter from Rui de Araújo, one of the nineteen Portuguese held at Malacca since 1509. It urged moving forward with the largest possible fleet to demand their release, and gave details of the fortifications. Afonso showed it to Diogo Mendes de Vasconcelos, as an argument to advance in a joint fleet. In April 1511, after fortifying Goa, he gathered a force of about 900 Portuguese, 200 Hindu mercenaries and about eighteen ships. He then sailed to Malacca against orders and despite the protest of Diogo Mendes, who claimed command of the expedition. Afonso eventually centralized the Portuguese government in the Indian Ocean. After the Malaccan conquest he wrote a letter to the King to explain his disagreement with Diogo Mendes, suggesting that further divisions could be harmful to the Portuguese in India. Under his command was Ferdinand Magellan, who had participated in the failed embassy of Diogo Lopes de Sequeira in 1509. After a false start towards the Red Sea, they sailed to the Strait of Malacca. It was the richest city that the Portuguese tried to take, and a focal point in the trade network where Malay traders met Gujarati, Chinese, Japanese, Javanese, Bengali, Persian and Arabic, among others, described by Tomé Pires as of invaluable richness. Despite its wealth, it was mostly a wooden-built city, with few masonry buildings but was defended by a mercenary force estimated at 20,000 men and more than 2000 pieces of artillery. Its greatest weakness was the unpopularity of the government of Sultan Mahmud Shah, who favoured Muslims, arousing dissatisfaction amongst other merchants. Afonso made a bold approach to the city, his ships decorated with banners, firing cannon volleys. He declared himself lord of all the navigation, demanded the Sultan release the prisoners and pay for damages, and demanded consent to build a fortified trading post. The Sultan eventually freed the prisoners, but was unimpressed by the small Portuguese contingent. Afonso then burned some ships at the port and four coastal buildings as a demonstration. The city being divided by the Malacca River, the connecting bridge was a strategic point, so at dawn on 25 July the Portuguese landed and fought a tough battle, facing poisoned arrows, taking the bridge in the evening. After fruitlessly waiting for the Sultan's reaction, they returned to the ships and prepared a junk (offered by Chinese merchants), filling it with men, artillery and sandbags. Commanded by António de Abreu, it sailed upriver at high tide to the bridge. The day after, all had landed. After a fierce fight during which the Sultan appeared with an army of war elephants, the defenders were dispersed and the Sultan fled. Afonso waited for the reaction of the Sultan. Merchants approached, asking for Portuguese protection. They were given banners to mark their premises, a sign that they would not be looted. On 15 August, the Portuguese attacked again, but the Sultan had fled the city. Under strict orders, they looted the city, but respected the banners. Afonso prepared Malacca's defenses against a Malay counterattack, building a fortress, assigning his men to shifts and using stones from the mosque and the cemetery. Despite the delays caused by heat and malaria, it was completed in November 1511, its surviving door now known as "A Famosa" ('the famous'). It was possibly then that Afonso had a large stone engraved with the names of the participants in the conquest. To quell disagreements over the order of the names, he had it set facing the wall, with the single inscription Lapidem quem reprobaverunt aedificantes (Latin for "The stone the builders rejected", from David's prophecy, Psalm 118:22–23) on the front. He settled the Portuguese administration, reappointing Rui de Araújo as factor, a post assigned before his 1509 arrest, and appointing rich merchant Nina Chatu to replace the previous Bendahara. Besides assisting in the governance of the city and first Portuguese coinage, he provided the junks for several diplomatic missions. Meanwhile, Afonso arrested and had executed the powerful Javanese merchant Utimuti Raja who, after being appointed to a position in the Portuguese administration as representative of the Javanese population, had maintained contacts with the exiled royal family. Shipwreck on the Flor de la mar, 1511 On 20 November 1511 Afonso sailed from Malacca to the coast of Malabar on the old Flor de la Mar carrack that had served to support the conquest of Malacca. Despite its unsound condition, he used it to transport the treasure amassed in the conquest, given its large capacity. He wanted to give the court of King Manuel a show of Malaccan treasures. There were also the offers from the Kingdom of Siam (Thailand) to the King of Portugal and all his own fortune. On the voyage the Flor de la Mar was wrecked in a storm, and Afonso barely escaped drowning. Missions from Malacca Embassies to Pegu, Sumatra and Siam, 1511 Most Muslim and Gujarati merchants having fled the city, Afonso invested in diplomatic efforts demonstrating generosity to Southeast Asian merchants, like the Chinese, to encourage good relations with the Portuguese. Trade and diplomatic missions were sent to continental kingdoms: Rui Nunes da Cunha was sent to Pegu (Burma), from where King Binyaram sent back a friendly emissary to Kochi in 1514 and Sumatra, Sumatran kings of Kampar and Indragiri sending emissaries to Afonso accepting the new power, as vassal states of Malacca. Knowing of Siamese ambitions over Malacca, Afonso sent Duarte Fernandes in a diplomatic mission to the Kingdom of Siam (Thailand), returning in a Chinese junk. He was one of the Portuguese who had been arrested in Malacca, having gathered knowledge about the culture of the region. There he was the first European to arrive, establishing amicable relations between the kingdom of Portugal and the court of the King of Siam Ramathibodi II, returning with a Siamese envoy bearing gifts and letters to Afonso and the King of Portugal. Expedition to the "spice islands" (Maluku islands), 1512 In November, after having secured Malacca and learning the location of the then secret "spice islands", Afonso sent three ships to find them, led by trusted António de Abreu with deputy commander Francisco Serrão. Malay sailors were recruited to guide them through Java, the Lesser Sunda Islands and the Ambon Island to Banda Islands, where they arrived in early 1512. There they remained for a month, buying and filling their ships with nutmeg and cloves. António de Abreu then sailed to Amboina whilst Serrão sailed towards the Moluccas, but he was shipwrecked near Seram. Sultan Abu Lais of Ternate heard of their stranding, and, seeing a chance to ally himself with a powerful foreign nation, brought them to Ternate in 1512 where they were permitted to build a fort on the island, the , built in 1522. Return to Cochin and Goa Afonso returned from Malacca to Cochin, but could not sail to Goa as it faced a serious revolt headed by the forces of Ismael Adil Shah, the Sultan of Bijapur, commanded by Rasul Khan and his countrymen. During Afonso's absence from Malacca, Portuguese who opposed the taking of Goa had waived its possession, even writing to the King that it would be best to let it go. Held up by the monsoon and with few forces available, Afonso had to wait for the arrival of reinforcement fleets headed by his nephew D. Garcia de Noronha, and Jorge de Mello Pereira. While at Cochin, Albuquerque started a school. In a private letter to King Manuel I, he stated that he had found a chest full of books with which to teach the children of married Portuguese settlers (casados) and Christian converts, of which there were about a hundred, to read and write. On 10 September 1512, Afonso sailed from Cochin to Goa with fourteen ships carrying 1,700 soldiers. Determined to recapture the fortress, he ordered trenches dug and a wall breached. But on the day of the planned final assault, Rasul Khan surrendered. Afonso demanded the fort be handed over with its artillery, ammunition and horses, and the deserters to be given up. Some had joined Rasul Khan when the Portuguese were forced to flee Goa in May 1510, others during the recent siege. Rasul Khan consented, on condition that their lives be spared. Afonso agreed and he left Goa. He did spare the lives of the deserters, but had them horribly mutilated. One such renegade was Fernão Lopes, bound for Portugal in custody, who escaped at the island of Saint Helena and led a 'Robinson Crusoe' life for many years. After such measures the town became the most prosperous Portuguese settlement in India. Campaign in the Red Sea, 1513 In December 1512 an envoy from Ethiopia arrived at Goa. Mateus was sent by the regent queen Eleni, following the arrival of the Portuguese from Socotra in 1507, as an ambassador for the king of Portugal in search of a coalition to help face growing Muslim influence. He was received in Goa with great honour by Afonso, as a long-sought "Prester John" envoy. His arrival was announced by King Manuel to Pope Leo X in 1513. Although Mateus faced the distrust of Afonso's rivals, who tried to prove he was some impostor or Muslim spy, Afonso sent him to Portugal. The King is described as having wept with joy at their report. In February 1513, while Mateus was in Portugal, Afonso sailed to the Red Sea with a force of about 1000 Portuguese and 400 Malabaris. He was under orders to secure that channel for Portugal. Socotra had proved ineffective to control the Red Sea entrance and was abandoned, and Afonso's hint that Massawa could be a good Portuguese base might have been influenced by Mateus' reports. Knowing that the Mamluks were preparing a second fleet at Suez, he wanted to advance before reinforcements arrived in Aden, and accordingly laid siege to the city. Aden was a fortified city, but although he had scaling ladders they broke during the chaotic attack. After half a day of fierce battle Afonso was forced to retreat. He cruised the Red Sea inside the Bab al-Mandab, with the first European fleet to have sailed this route. He attempted to reach Jeddah, but the winds were unfavourable and so he sheltered at Kamaran island in May, until sickness among the men and lack of fresh water forced him to retreat. In August 1513, after a second attempt to reach Aden, he returned to India with no substantial results. In order to destroy the power of Egypt, he wrote to King Manuel of the idea of diverting the course of the Nile river to render the whole country barren. He also intended to steal the body of the Islamic prophet, Muhammad, and hold it for ransom until all Muslims had left the Holy Land. Although Albuquerque's expedition failed to reach Suez, such an incursion into the Red Sea by a Christian fleet for the first time in history stunned the Muslim world, and panic spread in Cairo. Submission of Calicut Albuquerque achieved during his term a favourable end to hostilities between the Portuguese and the Zamorin of Calicut, which had lasted since the massacre of the Portuguese in Calicut in 1502. As naval trade faltered and vassals defected, with no foreseeable solutions to the conflict with the Portuguese, the court of the Zamorin fell to in-fighting. The ruling Zamorin was assassinated and replaced by a rival, under the instigation of Albuquerque, permitting peace talks to commence. The Portuguese were allowed to build a fortress in Calicut itself, and acquired rights to obtain as much pepper and ginger as they wished, at stipulated prices, and half the customs duties of Calicut as yearly tribute. Construction of the fortress began immediately, under the supervision of chief architect Tomás Fernandes. Administration and diplomacy in Goa, 1514 With peace concluded, in 1514 Afonso devoted himself to governing Goa and receiving embassies from Indian governors, strengthening the city and encouraging marriages of Portuguese men and local women. At that time, Portuguese women were barred from traveling overseas in order to maintain discipline among the men on board the ships. In 1511 under a policy which Afonso promulgated, the Portuguese government encouraged their explorers to marry local women. To promote settlement, the King of Portugal granted freeman status and exemption from Crown taxes to Portuguese men (known as casados, or "married men") who ventured overseas and married local women. With Afonso's encouragement, mixed marriages flourished. He appointed local people for positions in the Portuguese administration and did not interfere with local traditions (except "sati", the practice of immolating widows, which he banned). In March 1514 King Manuel sent to Pope Leo X a huge and exotic embassy led by Tristão da Cunha, who toured the streets of Rome in an extravagant procession of animals from the colonies and wealth from the Indies. His reputation reached its peak, laying foundations of the Portuguese Empire in the East. In early 1514, Afonso sent ambassadors to Gujarat's Sultan Muzaffar Shah II, ruler of Cambay, to seek permission to build a fort on Diu, India. The mission returned without an agreement, but diplomatic gifts were exchanged, including an Indian rhinoceros, Afonso sent the rhino to King Manuel, making it the first living example of a rhinoceros seen in Europe since the Roman Empire. Conquest of Ormuz and Illness In 1513, at Cannanore, Afonso was visited by a Persian ambassador from Shah Ismail I, who had sent ambassadors to Gujarat, Ormuz and Bijapur. The shah's ambassador to Bijapur invited Afonso to send back an envoy to Persia. Miguel Ferreira was sent via Ormuz to Tabriz, where he had several interviews with the shah about common goals on defeating the Mamluk sultan. At the same time, Albuquerque decided to conclude the effective conquest of Hormuz. He had learned that after the Portuguese retreat in 1507, a young king was reigning under the influence of a powerful Persian vizier, Reis Hamed, whom the king greatly feared. At Ormuz in March 1515, Afonso met the king and asked the vizier to be present. He then had him immediately stabbed and killed by his entourage, thus "freeing" the terrified king, so the island in the Persian Gulf yielded to him without resistance and remained a vassal state of the Portuguese Empire. Ormuz itself would not be Persian territory for another century, until an English-Persian alliance finally expelled the Portuguese in 1622. At Ormuz, Afonso met with Miguel Ferreira, returning with rich presents and an ambassador, carrying a letter from the Persian potentate Shah Ismael, inviting Afonso to become a leading lord in Persia. There he remained, engaging in diplomatic efforts, receiving envoys and overseeing the construction of the new fortress, while becoming increasingly ill. His illness was reported as early as September 1515. In November 1515, he embarked on a journey back to Goa. Death At this time, his political enemies at the Portuguese court were planning his downfall. They had lost no opportunity in stirring up the jealousy of King Manuel against him, insinuating that Afonso intended to usurp power in Portuguese India. While on his return voyage from Ormuz in the Persian Gulf, near the harbor of Chaul, he received news of a Portuguese fleet arriving from Europe, bearing dispatches announcing that he was to be replaced by his personal foe, Lopo Soares de Albergaria. Realizing the plot that his enemies had moved against him, profoundly disillusioned, he voiced his bitterness: "Grave must be my sins before the King, for I am in ill favor with the King for love of the men, and with the men for love of the King." Feeling himself near death, he donned the surcoat of the Order of Santiago, of which he was a knight, and drew up his will, appointed the captain and senior officials of Ormuz, and organized a final council with his captains to decide the main matters affecting the Portuguese State of India. He wrote a brief letter to King Manuel, asking him to confer onto his natural son "all of the high honors and rewards" that Afonso had received, and assuring Manuel of his loyalty. On 16 December 1515, Afonso de Albuquerque died within sight of Goa. As his death was known, in the city "great wailing arose", and many took to the streets to witness his body carried on a chair by his main captains, in a procession lit by torches amidst the crowd. Afonso's body was buried in Goa, according to his will, in the Church of Nossa Senhora da Serra (Our Lady of the Hill), which he had been built in 1513 to thank the Madonna for his escape from Kamaran island. That night, the population of Goa, both Hindu and Portuguese, gathered to mourn his death. In Portugal, King Manuel's zigzagging policies continued, still trapped by the constraints of real-time medieval communication between Lisbon and India and unaware that Afonso was dead. Hearing rumours that the Mamluk Sultan of Egypt was preparing a magnificent army at Suez to prevent the conquest of Ormuz, he repented of having replaced Afonso, and in March 1516 urgently wrote to Albergaria to return the command of all operations to Afonso and provide him with resources to face the Egyptian threat. He organized a new Portuguese navy in Asia, with orders that Afonso (if he was still in India), be made commander-in-chief against the Sultan of Cairo's armies. Manuel would afterwards learn that Afonso had died many months earlier, and that his reversed decision had been delivered many months too late. After 51 years, in 1566, his body was moved to Nossa Senhora da Graça church in Lisbon, which was ruined and rebuilt after the 1755 Great Lisbon earthquake. Legacy King Manuel I of Portugal was belatedly convinced of Afonso's loyalty, and endeavoured to atone for his lack of confidence in Afonso by heaping honours upon his son, Brás de Albuquerque (1500–1580), whom he renamed "Afonso" in memory of the father. Afonso de Albuquerque was a prolific writer, having sent numerous letters during his governorship, covering topics from minor issues to major strategies. In 1557 his son published his biography under the title Commentarios do Grande Affonso d'Alboquerque. In 1572, Afonso's actions were described in The Lusiads, the Portuguese main epic poem by Luís Vaz de Camões (Canto X, strophes 40–49). The poet praises his achievements, but has the muses frown upon the harsh rule of his men, of whom Camões was almost a contemporary fellow. In 1934, Afonso was celebrated by Fernando Pessoa in Mensagem, a symbolist epic. In the first part of this work, called "Brasão" (Coat-of-Arms), he relates Portuguese historical protagonists to each of the fields in the Portuguese coat-of-arms, Afonso being one of the wings of the griffin headed by Henry the Navigator, the other wing being King John II. A variety of mango, which was created by Portuguese Jesuits in Goa via grafting techniques, was named in his honour. Numerous homages have been paid to Afonso; he is featured in the Padrão dos Descobrimentos monument; there is a square named after him in Lisbon, which also features a bronze statue, and two Portuguese Navy ships have been named in his honour: the sloop NRP Afonso de Albuquerque (1884) and the warship NRP Afonso de Albuquerque. Titles and honours Captain-Major of the Sea of Arabia 2nd Governor of India 1st Duke of Goa A knight of the Portuguese Order of Saint James of the Sword Fidalgo of the Royal Household Notes References Citations Bibliography In other languages Albuquerque, Afonso de, D. Manuel I, António Baião, "Cartas para el-rei d". Manuel I", Editora Livraria Sá de Costa (1957) Primary sources (volume 6, chapter I) External links Paul Lunde, The coming of the Portuguese, 2006, Saudi Aramco World Portuguese explorers Explorers of Asia Viceroys of Portuguese India 1453 births 1515 deaths Portuguese admirals Portuguese colonial governors and administrators Portuguese generals Portuguese Renaissance writers People from Vila Franca de Xira Colonial Goa Colonial Kerala Maritime history of Portugal Portuguese in Kerala History of Kollam Shipwreck survivors 1510s in Portuguese India 16th-century Portuguese people

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1599

https://en.wikipedia.org/wiki/Alexander%20of%20Aphrodisias

Alexander of Aphrodisias

Alexander of Aphrodisias (; AD) was a Peripatetic philosopher and the most celebrated of the Ancient Greek commentators on the writings of Aristotle. He was a native of Aphrodisias in Caria, and lived and taught in Athens at the beginning of the 3rd century, where he held a position as head of the Peripatetic school. He wrote many commentaries on the works of Aristotle, extant are those on the Prior Analytics, Topics, Meteorology, Sense and Sensibilia, and Metaphysics. Several original treatises also survive, and include a work On Fate, in which he argues against the Stoic doctrine of necessity; and one On the Soul. His commentaries on Aristotle were considered so useful that he was styled, by way of pre-eminence, "the commentator" (). Life and career Alexander was a native of Aphrodisias in Caria (present-day Turkey) and came to Athens towards the end of the 2nd century. He was a student of the two Stoic, or possibly Peripatetic, philosophers Sosigenes and Herminus, and perhaps of Aristotle of Mytilene. At Athens he became head of the Peripatetic school and lectured on Peripatetic philosophy. Alexander's dedication of On Fate to Septimius Severus and Caracalla, in gratitude for his position at Athens, indicates a date between 198 and 209. A recently published inscription from Aphrodisias confirms that he was head of one of the Schools at Athens and gives his full name as Titus Aurelius Alexander. His full nomenclature shows that his grandfather or other ancestor was probably given Roman citizenship by the emperor Antoninus Pius, while proconsul of Asia. The inscription honours his father, also called Alexander and also a philosopher. This fact makes it plausible that some of the suspect works that form part of Alexander's corpus should be ascribed to his father. Commentaries Alexander composed several commentaries on the works of Aristotle, in which he sought to escape a syncretistic tendency and to recover the pure doctrines of Aristotle. His extant commentaries are on Prior Analytics (Book 1), Topics, Meteorology, Sense and Sensibilia, and Metaphysics (Books 1–5). The commentary on the Sophistical Refutations is deemed spurious, as is the commentary on the final nine books of the Metaphysics. The lost commentaries include works on the De Interpretatione, Posterior Analytics, Physics, On the Heavens, On Generation and Corruption, On the Soul, and On Memory. Simplicius of Cilicia mentions that Alexander provided commentary on the quadrature of the lunes, and the corresponding problem of squaring the circle. In April 2007, it was reported that imaging analysis had discovered an early commentary on Aristotle's Categories in the Archimedes Palimpsest, and Robert Sharples suggested Alexander as the most likely author. Original treatises There are also several extant original writings by Alexander. These include: On the Soul, Problems and Solutions, Ethical Problems, On Fate, and On Mixture and Growth. Three works attributed to him are considered spurious: Medical Questions, Physical Problems, and On Fevers. Additional works by Alexander are preserved in Arabic translation, these include: On the Principles of the Universe, On Providence, and Against Galen on Motion. On the Soul (De anima) is a treatise on the soul written along the lines suggested by Aristotle in his own De anima. Alexander contends that the undeveloped reason in man is material (nous hylikos) and inseparable from the body. He argued strongly against the doctrine of the soul's immortality. He identified the active intellect (nous poietikos), through whose agency the potential intellect in man becomes actual, with God. A second book is known as the Supplement to On the Soul (Mantissa). The Mantissa is a series of twenty-five separate pieces of which the opening five deal directly with psychology. The remaining twenty pieces cover problems in physics and ethics, of which the largest group deals with questions of vision and light, and the final four with fate and providence. The Mantissa was probably not written by Alexander in its current form, but much of the actual material may be his. Problems and Solutions (Quaestiones) consists of three books which, although termed "problems and solutions of physical questions," treat of subjects which are not all physical, and are not all problems. Among the sixty-nine items in these three books, twenty-four deal with physics, seventeen with psychology, eleven with logic and metaphysics, and six with questions of fate and providence. It is unlikely that Alexander wrote all of the Quaestiones, some may be Alexander's own explanations, while others may be exercises by his students. Ethical Problems was traditionally counted as the fourth book of the Quaestiones. The work is a discussion of ethical issues based on Aristotle, and contains responses to questions and problems deriving from Alexander's school. It is likely that the work was not written by Alexander himself, but rather by his pupils on the basis of debates involving Alexander. On Fate is a treatise in which Alexander argues against the Stoic doctrine of necessity. In On Fate Alexander denied three things - necessity (), the foreknowledge of fated events that was part of the Stoic identification of God and Nature, and determinism in the sense of a sequence of causes that was laid down beforehand () or predetermined by antecedents (). He defended a view of moral responsibility we would call libertarianism today. On Mixture and Growth discusses the topic of mixture of physical bodies. It is both an extended discussion (and polemic) on Stoic physics, and an exposition of Aristotelian thought on this theme. On the Principles of the Universe is preserved in Arabic translation. This treatise is not mentioned in surviving Greek sources, but it enjoyed great popularity in the Muslim world, and a large number of copies have survived. The main purpose of this work is to give a general account of Aristotelian cosmology and metaphysics, but it also has a polemical tone, and it may be directed at rival views within the Peripatetic school. Alexander was concerned with filling the gaps of the Aristotelian system and smoothing out its inconsistencies, while also presenting a unified picture of the world, both physical and ethical. The topics dealt with are the nature of the heavenly motions and the relationship between the unchangeable celestial realm and the sublunar world of generation and decay. His principal sources are the Physics (book 7), Metaphysics (book 12), and the Pseudo-Aristotelian On the Universe. On Providence survives in two Arabic versions. In this treatise, Alexander opposes the Stoic view that divine Providence extends to all aspects of the world; he regards this idea as unworthy of the gods. Instead, providence is a power that emanates from the heavens to the sublunar region, and is responsible for the generation and destruction of earthly things, without any direct involvement in the lives of individuals. Influence By the 6th century Alexander's commentaries on Aristotle were considered so useful that he was referred to as "the commentator" (). His commentaries were greatly esteemed among the Arabs, who translated many of them, and he is heavily quoted by Maimonides. In 1210, the Church Council of Paris issued a condemnation, which probably targeted the writings of Alexander among others. In the early Renaissance his doctrine of the soul's mortality was adopted by Pietro Pomponazzi (against the Thomists and the Averroists), and by his successor Cesare Cremonini. This school is known as Alexandrists. Alexander's band, an optical phenomenon, is named after him. Modern editions Several of Alexander's works were published in the Aldine edition of Aristotle, Venice, 1495–1498; his De Fato and De Anima were printed along with the works of Themistius at Venice (1534); the former work, which has been translated into Latin by Grotius and also by Schulthess, was edited by J. C. Orelli, Zürich, 1824; and his commentaries on the Metaphysica by H. Bonitz, Berlin, 1847. In 1989 the first part of his On Aristotle Metaphysics was published in English translation as part of the Ancient commentators project. Since then, other works of his have been translated into English. See also Alexander's band - an optical phenomenon associated with rainbows Free will in antiquity Notes Bibliography Translations M. Bergeron, Dufour (trans., comm.), 2009. De l’Âme. Textes & Commentaires. . Paris: Librairie Philosophique J. Vrin, 2008. 416 p. R. W. Sharples, 1990, Alexander of Aphrodisias: Ethical Problems. Duckworth. W. E. Dooley, 1989, Alexander of Aphrodisias: On Aristotle Metaphysics 1. Duckworth. W. E. Dooley, A. Madigan, 1992, Alexander of Aphrodisias: On Aristotle Metaphysics 2-3. Duckworth. A. Madigan, 1993, Alexander of Aphrodisias: On Aristotle Metaphysics 4. Duckworth. W. Dooley, 1993, Alexander of Aphrodisias: On Aristotle Metaphysics 5. Duckworth. E. Lewis, 1996, Alexander of Aphrodisias: On Aristotle Meteorology 4. Duckworth. E. Gannagé, 2005, Alexander of Aphrodisias: On Aristotle On Coming-to-Be and Perishing 2.2-5. Duckworth. A. Towey, 2000, Alexander of Aphrodisias: On Aristotle On Sense Perception. Duckworth. V. Caston, 2011, Alexander of Aphrodisias: On Aristotle On the Soul. Duckworth. J. Barnes, S. Bobzien, K. Flannery, K. Ierodiakonou, 1991, Alexander of Aphrodisias: On Aristotle Prior Analytics 1.1-7. Duckworth. I. Mueller, J. Gould, 1999, Alexander of Aphrodisias: On Aristotle Prior Analytics 1.8-13. Duckworth. I. Mueller, J. Gould, 1999, Alexander of Aphrodisias: On Aristotle Prior Analytics 1.14-22. Duckworth. I. Mueller, 2006, Alexander of Aphrodisias: On Aristotle Prior Analytics 1.23-31. Duckworth. I. Mueller, 2006, Alexander of Aphrodisias: On Aristotle Prior Analytics 1.32-46. Duckworth. J. M. Van Ophuijsen, 2000, Alexander of Aphrodisias: On Aristotle Topics 1. Duckworth. R. W. Sharples, 1983, Alexander of Aphrodisias: On Fate. Duckworth. R. W. Sharples, 1992, Alexander of Aphrodisias: Quaestiones 1.1-2.15. Duckworth. R. W. Sharples, 1994, Alexander of Aphrodisias: Quaestiones 2.16-3.15. Duckworth. R. W. Sharples, 2004, Alexander of Aphrodisias: Supplement to On the Soul. Duckworth. Charles Genequand, 2001, Alexander of Aphrodisias: On the Cosmos. Brill. Studies Fazzo, S. Aporia e sistema. La materia, la forma e il divino nelle Quaestiones di Alessandro di Afrodisia, Pisa: ETS, 2002. Flannery, Kevin L. Ways into the Logic of Alexander of Aphrodisias, Leiden: Brill, 1995. Gili, Luca. La sillogistica di Alessandro di Afrodisia. Sillogistica categorica e sillogistica modale nel commento agli "Analitici Primi" di Aristotele, Hildesheim: Georg Olms, 2011. Moraux, Paul. Der Aristotelismus bei den Griechen, Von Andronikos bis Alexander von Aphrodisias, III: Alexander von Aphrodisias, Berlin: Walter Gruyter, 2001. Rescher, Nicholas & Marmura, Michael E., The Refutation by Alexander of Aphrodisias of Galen's Treatise on the Theory of Motion, Islamabad: Islamic Research Institute, 1965. Todd, Robert B., 'Alexander of Aphrodisias on Stoic Physics. A Study of the "De Mixtione" with Preliminary Essays, Text, Translation and Commentary, Leiden: Brill, 1976. External links Alexander on Information Philosopher Online Greek texts: Scripta minora'', ed. Bruns Aristotelian commentaries: Metaphysics, Prior Analytics I, Topics, De sensu and Meteorology, In Aristotelis Metaphysica commentaria , Miscellanea 2nd-century Greek people 2nd-century philosophers Commentators on Aristotle Roman-era Peripatetic philosophers Roman-era philosophers in Athens Roman-era students in Athens People from Aphrodisias

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1620

https://en.wikipedia.org/wiki/Alexei%20Petrovich%2C%20Tsarevich%20of%20Russia

Alexei Petrovich, Tsarevich of Russia

Grand Duke Alexei Petrovich of Russia (28 February 1690 – 7 July 1718) was a Russian Tsarevich. He was born in Moscow, the son of Tsar Peter I and his first wife, Eudoxia Lopukhina. Alexei despised his father and repeatedly thwarted Peter's plans to raise him as successor to the throne. His brief defection to Austria scandalized the Russian government, leading to harsh repressions against Alexei and his associates. Alexei died after interrogation under torture, and his son Peter Alexeyevich became the new heir apparent. Childhood The young Alexei was brought up by his mother, who fostered an atmosphere of disdain towards his father, the Tsar. Alexei's relations with his father suffered from the hatred between his father and his mother, as it was very difficult for him to feel affection for his mother's worst persecutor. From the ages of 6 to 9, Alexei was educated by his tutor Vyazemsky, but after the removal of his mother by Peter the Great to the Suzdal Intercession Convent, Alexei was confined to the care of educated foreigners, who taught him history, geography, mathematics and French. Military career In 1703, Alexei was ordered to follow the army to the field as a private in an artillery regiment. In 1704, he was present at the capture of Narva. At this period, the preceptors of the Tsarevich had the highest opinion of his ability. Alexei had strong leanings towards archaeology and ecclesiology. However, Peter had wished his son and heir to dedicate himself to the service of new Russia, and demanded from him unceasing labour in order to maintain Russia's new wealth and power. Painful relations between father and son, quite apart from the prior personal antipathies, were therefore inevitable. It was an additional misfortune for Alexei that his father should have been too busy to attend to him just as he was growing up from boyhood to manhood. He was left in the hands of reactionary boyars and priests, who encouraged him to hate his father and wish for the death of the Tsar. In 1708, Peter sent Alexei to Smolensk to collect supplies and recruits, and after that to Moscow to fortify it against Charles XII of Sweden. At the end of 1709, Alexei went to Dresden for one year. There, he finished lessons in French, German, mathematics and fortification. After his education, Alexei married Princess Charlotte of Brunswick-Wolfenbüttel, whose family was connected by marriage to many of the great families of Europe (for example, Charlotte's sister Elizabeth was married to Holy Roman Emperor Charles VI, ruler of the Habsburg Monarchy). He met with Princess Charlotte, both were pleased with each other and the marriage went forward. In theory, Alexei could have refused the marriage, and he had been encouraged by his father to at least meet his intended. "Why haven't you written to tell me what you thought about her?" wrote Peter in a letter dated 13 August 1710. The marriage contract was signed in September. The wedding was celebrated at Torgau, Germany, on 14 October 1711 (O.S.). One of the terms of the marriage contract agreed to by Alexei was that while any forthcoming children were to be raised in the Orthodox faith, Charlotte herself was allowed to retain her Protestant faith, an agreement opposed by Alexei's followers. As for the marriage itself, the first 6 months went well but quickly became a failure within the next 6 months. Alexei was drunk constantly and Alexei pronounced his bride "pock-marked" and "too thin". He insisted on separate apartments and ignored her in public. Three weeks later, the bridegroom was hurried away by his father to Toruń to superintend the provisioning of the Russian troops in Poland. For the next twelve months Alexei was kept constantly on the move. His wife joined him at Toruń in December, but in April 1712 a peremptory ukase ordered him off to the army in Pomerania, and in the autumn of the same year he was forced to accompany his father on a tour of inspection through Finland. He had two children with Charlotte: Natalia Alexeievna Romanova (21 July 1714 – 3 December 1728) Peter Alexeyevich Romanov (23 October 1715 – 30 January 1730) Peter Alexeyevich would succeed as the Emperor Peter II in 1727. With his death in 1730, the direct male-line of the House of Romanov became extinct. After the birth of Natalia in 1714, Alexei brought his long-time Finnish serf mistress Afrosinia to live in the palace. Some historians speculate that it was his conservative powerbase's disapproval of his foreign, non-Orthodox bride, more so than her appearance, that caused Alexei to spurn Charlotte. Another influence was Alexander Kikin, a high-placed official who had fallen out with the Tsar and had been deprived of his estates. Flight Immediately on his return from Finland, Alexei was dispatched by his father to Staraya Russa and Lake Ladoga to see to the building of new ships. This was the last commission entrusted to him, since Peter had not been satisfied with his son's performance and his lack of enthusiasm. When Peter asked Alexei to show his progress in mechanics and mathematics, the son responded by shooting himself in the right hand, and Peter took no more interest in him. Nevertheless, Peter made one last effort to "reclaim" his son. On 22 October 1715 (O.S.), Charlotte died, after giving birth to a son, the grand-duke Peter, the future Emperor Peter II. On the day of the funeral, Peter sent Alexei a stern letter, urging him to take interest in the affairs of the state. Peter threatened to cut him off if he did not acquiesce in his father's plans. Alexei wrote a pitiful reply to his father, offering to renounce the succession in favour of his infant son Peter. Peter would agree but on the condition that Alexei remove himself as a dynastic threat and become a monk. While Alexei was pondering his options, on 26 August 1716 Peter wrote to Alexei from abroad, urging him, if he desired to remain tsarevich, to join him and the army without delay. Rather than face this ordeal, Alexei fled to Vienna and placed himself under the protection of his brother-in-law, the emperor Charles VI, who sent him for safety first to the Tirolean fortress of Ehrenberg (near Reutte), and finally to the castle of Sant'Elmo at Naples. He was accompanied throughout his journey by Afrosinia. That the emperor sincerely sympathized with Alexei, and suspected Peter of harbouring murderous designs against his son, is plain from his confidential letter to George I of Great Britain, whom he consulted on this delicate affair. Peter felt insulted: the flight of the tsarevich to a foreign potentate was a reproach and a scandal, and he had to be recovered and brought back to Russia at all costs. This difficult task was accomplished by Count Peter Tolstoi, the most subtle and unscrupulous of Peter's servants. Return Alexei would only consent to return on his father solemnly swearing, that if he came back he should not be punished in the least, but cherished as a son and allowed to live quietly on his estates and marry Afrosinia. On 31 January 1718, the tsarevich reached Moscow. Peter had already determined to institute a searching inquisition in order to get at the bottom of the mystery of the flight. On 18 February a "confession" was extorted from Alexei which implicated most of his friends, and he then publicly renounced the succession to the throne in favour of the baby grand-duke Peter Petrovich. A brutal reign of terror ensued, in the course of which the ex-tsaritsa Eudoxia was dragged from her monastery and publicly tried for alleged adultery, while all who had in any way befriended Alexei were impaled or broken on the wheel while having their flesh torn with red-hot pincers on their bare backs or bare feet slowly roasted over burning coals, and were otherwise lingeringly done to death. Alexei's servants were beheaded or had their tongues cut out. All this was done to terrorize the reactionaries and isolate the tsarevich. In April 1718 fresh confessions were extorted from, and in regard to, Alexei. This included the words of Afrosinia, who had turned state's evidence. "I shall bring back the old people..." Alexei is reported to have told her, "...and choose myself new ones according to my will; when I become sovereign I shall live in Moscow and leave Saint Petersburg simply as any other town; I won't launch any ships; I shall maintain troops only for defense, and won't make war on anyone; I shall be content with the old domains. In winter I shall live in Moscow, and in summer in Iaroslavl." Despite this and other hearsay evidence, there were no facts to go upon. The worst that could be brought against him was that he had wished his father's death. In the eyes of Peter, his son was now a self-convicted and most dangerous traitor, whose life was forfeit. But there was no getting over the fact that his father had sworn to pardon him and let him live in peace if he returned to Russia. The whole matter was solemnly submitted to a grand council of prelates, senators, ministers and other dignitaries on 13 June 1718 (O.S.). The clergy, for their part, declared the Tsarevich Alexei, "...had placed his Confidence in those who loved the ancient Customs, and that he had become acquainted with them by the Discourses they held, wherein they had constantly praised the ancient Manners, and spoke with Distaste of the Novelties his Father had introduced." Declaring this to be a civil rather than an ecclesiastical matter, the clergy left the matter to the tsar's own decision. At noon on 24 June (O.S.), the temporal dignitaries—the 126 members of both the Senate and magistrates that comprised the court—declared Alexei guilty and sentenced him to death. But the examination by torture continued, so desperate was Peter to uncover any possible collusion. On 19 June (O.S.), the weak and ailing tsarevich received twenty-five strokes with the knout, and then, on 24 June (O.S.), he was subject to fifteen more. On 26 June (O.S.), Alexei died in the Peter and Paul fortress in Saint Petersburg, two days after the senate had condemned him to death for conspiring rebellion against his father, and for hoping for the cooperation of the common people and the armed intervention of his brother-in-law, Emperor Charles VI. Ancestry References Attribution: Further reading Grey, Ian. "Peter the Great and the Tsarevich Alexei" History Today (Nov 1974), Vol. 24 Issue 11, pp 754–764, online. Matthew S. Anderson, Peter the Great (London: Thames and Hudson, 1978). Robert Nisbet Bain, The First Romanovs 1613–1725 (London, 1905). Robert K. Massie, Peter the Great, His Life and World (New York: Ballantine, 1981). B.H. Sumner, Peter the Great and the Emergence of Russia (London: 1950), pp 91–100. Fredrick Charles Weber, The Present State of Russia (2 vols.), (1723; reprint, London: Frank Cass and Co, 1968). Lindsey Hughes, Russia in the Age of Peter the Great (New Haven and London: Yale University Press, 1998). Simon Sebag Montefiore, The Romanovs 1613-1918 (London: Weidenfeld & Nicolson, 2016). External links 1690 births 1718 deaths People from Moscow House of Romanov Heirs apparent who never acceded Prisoners who died in Russian detention Russian people who died in prison custody 17th-century Russian people 18th-century Russian people Russian tsarevich

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1624

https://en.wikipedia.org/wiki/Andrew%20Johnson

Andrew Johnson

Andrew Johnson (December 29, 1808July 31, 1875) was the 17th president of the United States, serving from 1865 to 1869. He assumed the presidency as he was vice president at the time of the assassination of Abraham Lincoln. Johnson was a Democrat who ran with Lincoln on the National Union ticket, coming to office as the Civil War concluded. He favored quick restoration of the seceded states to the Union without protection for the former slaves. This led to conflict with the Republican-dominated Congress, culminating in his impeachment by the House of Representatives in 1868. He was acquitted in the Senate by one vote. Johnson was born into poverty and never attended school. He was apprenticed as a tailor and worked in several frontier towns before settling in Greeneville, Tennessee. He served as alderman and mayor there before being elected to the Tennessee House of Representatives in 1835. After briefly serving in the Tennessee Senate, Johnson was elected to the House of Representatives in 1843, where he served five two-year terms. He became governor of Tennessee for four years, and was elected by the legislature to the Senate in 1857. In his congressional service, he sought passage of the Homestead Bill which was enacted soon after he left his Senate seat in 1862. Southern slave states seceded to form the Confederate States of America, including Tennessee, but Johnson remained firmly with the Union. He was the only sitting senator from a Confederate state who did not resign his seat upon learning of his state's secession. In 1862, Lincoln appointed him as Military Governor of Tennessee after most of it had been retaken. In 1864, Johnson was a logical choice as running mate for Lincoln, who wished to send a message of national unity in his re-election campaign; and became vice president after a victorious election in 1864. Johnson implemented his own form of Presidential Reconstruction, a series of proclamations directing the seceded states to hold conventions and elections to reform their civil governments. Southern states returned many of their old leaders and passed Black Codes to deprive the freedmen of many civil liberties, but Congressional Republicans refused to seat legislators from those states and advanced legislation to overrule the Southern actions. Johnson vetoed their bills, and Congressional Republicans overrode him, setting a pattern for the remainder of his presidency. Johnson opposed the Fourteenth Amendment which gave citizenship to former slaves. In 1866, he went on an unprecedented national tour promoting his executive policies, seeking to break Republican opposition. As the conflict grew between the branches of government, Congress passed the Tenure of Office Act restricting Johnson's ability to fire Cabinet officials. He persisted in trying to dismiss Secretary of War Edwin Stanton, but ended up being impeached by the House of Representatives and narrowly avoided conviction in the Senate. He did not win the 1868 Democratic presidential nomination and left office the following year. Johnson returned to Tennessee after his presidency and gained some vindication when he was elected to the Senate in 1875, making him the only former president to serve in the Senate. He died five months into his term. Johnson's strong opposition to federally guaranteed rights for black Americans is widely criticized; he is regarded by many historians as one of the worst presidents in American history. Early life and career Childhood Andrew Johnson was born in Raleigh, North Carolina, on December 29, 1808, to Jacob Johnson (1778–1812) and Mary ("Polly") McDonough (1783–1856), a laundress. He was of English, Scots-Irish, and Irish ancestry. He had a brother William, four years his senior, and an older sister Elizabeth, who died in childhood. Johnson's birth in a two-room shack was a political asset in the mid-19th century, and he would frequently remind voters of his humble origins. Jacob Johnson was a poor man, as had been his father, William Johnson, but he became town constable of Raleigh before marrying and starting a family. Both Jacob and Mary were illiterate, and had worked as tavern servants, while Johnson never attended school and grew up in poverty. Jacob died of an apparent heart attack while ringing the town bell, shortly after rescuing three drowning men, when his son Andrew was three. Polly Johnson worked as a washerwoman and became the sole support of her family. Her occupation was then looked down on, as it often took her into other homes unaccompanied. Since Andrew did not resemble either of his siblings, there are rumors that he may have been fathered by another man. Polly Johnson eventually remarried to a man named Turner Doughtry, who was as poor as she was. Johnson's mother apprenticed her son William to a tailor, James Selby. Andrew also became an apprentice in Selby's shop at age ten and was legally bound to serve until his 21st birthday. Johnson lived with his mother for part of his service, and one of Selby's employees taught him rudimentary literacy skills. His education was augmented by citizens who would come to Selby's shop to read to the tailors as they worked. Even before he became an apprentice, Johnson came to listen. The readings caused a lifelong love of learning, and one of his biographers, Annette Gordon-Reed, suggests that Johnson, later a gifted public speaker, learned the art as he threaded needles and cut cloth. Johnson was not happy at James Selby's, and after about five years, both he and his brother ran away. Selby responded by placing a reward for their return: "Ten Dollars Reward. Ran away from the subscriber, two apprentice boys, legally bound, named William and Andrew Johnson ... [payment] to any person who will deliver said apprentices to me in Raleigh, or I will give the above reward for Andrew Johnson alone." The brothers went to Carthage, North Carolina, where Andrew Johnson worked as a tailor for several months. Fearing he would be arrested and returned to Raleigh, Johnson moved to Laurens, South Carolina. He found work quickly, met his first love, Mary Wood, and made her a quilt as a gift. However, she rejected his marriage proposal. He returned to Raleigh, hoping to buy out his apprenticeship, but could not come to terms with Selby. Unable to stay in Raleigh, where he risked being apprehended for abandoning Selby, he decided to move west. Move to Tennessee Johnson left North Carolina for Tennessee, traveling mostly on foot. After a brief period in Knoxville, he moved to Mooresville, Alabama. He then worked as a tailor in Columbia, Tennessee, but was called back to Raleigh by his mother and stepfather, who saw limited opportunities there and who wished to emigrate west. Johnson and his party traveled through the Blue Ridge Mountains to Greeneville, Tennessee. Andrew Johnson fell in love with the town at first sight, and when he became prosperous purchased the land where he had first camped and planted a tree in commemoration. In Greeneville, Johnson established a successful tailoring business in the front of his home. In 1827, at the age of 18, he married 16-year-old Eliza McCardle, the daughter of a local shoemaker. The pair were married by Justice of the Peace Mordecai Lincoln, first cousin of Thomas Lincoln, whose son would become president. The Johnsons were married for almost 50 years and had five children: Martha (1828), Charles (1830), Mary (1832), Robert (1834), and Andrew Jr. (1852). Though she suffered from tuberculosis, Eliza supported her husband's endeavors. She taught him mathematics skills and tutored him to improve his writing. Shy and retiring by nature, Eliza Johnson usually remained in Greeneville during Johnson's political rise. She was not often seen during her husband's presidency; their daughter Martha usually served as official hostess. Johnson's tailoring business prospered during the early years of the marriage, enabling him to hire help and giving him the funds to invest profitably in real estate. He later boasted of his talents as a tailor, "my work never ripped or gave way". He was a voracious reader. Books about famous orators aroused his interest in political dialogue, and he had private debates on the issues of the day with customers who held opposing views. He also took part in debates at Greeneville College. Johnson's slaves In 1843, Johnson purchased his first slave, Dolly, who was 14 years old at the time. Soon after, he purchased Dolly's half-brother Sam. Dolly had three children—Liz, Florence and William. In 1857, Andrew Johnson purchased Henry, who was 13 at the time and would later accompany the Johnson family to the White House. Sam Johnson and his wife Margaret had nine children. Sam became a commissioner of the Freedmen's Bureau and was known for being a proud man who negotiated the nature of his work with the Johnson family. Notably, he received some monetary compensation for his labors and negotiated with Andrew Johnson to receive a tract of land which Andrew Johnson gave him for free in 1867. Ultimately, Johnson owned at least ten slaves. Andrew Johnson freed his slaves on August 8, 1863; they remained with him as paid servants. A year later, Johnson, as military governor of Tennessee, proclaimed the freedom of Tennessee's slaves. Sam and Margaret, Johnson's former slaves, lived in his tailor shop while he was president, without rent. As a sign of appreciation for proclaiming freedom, Andrew Johnson was given a watch by newly emancipated people in Tennessee inscribed with "…for his Untiring Energy in the Cause of Freedom". Political rise Tennessee politician Johnson helped organize a mechanics' (working men's) ticket in the 1829 Greeneville municipal election. He was elected town alderman, along with his friends Blackston McDannel and Mordecai Lincoln. Following the 1831 Nat Turner slave rebellion, a state convention was called to pass a new constitution, including provisions to disenfranchise free people of color. The convention also wanted to reform real estate tax rates, and provide ways of funding improvements to Tennessee's infrastructure. The constitution was submitted for a public vote, and Johnson spoke widely for its adoption; the successful campaign provided him with statewide exposure. On January 4, 1834, his fellow aldermen elected him mayor of Greeneville. In 1835, Johnson made a bid for election to the "floater" seat which Greene County shared with neighboring Washington County in the Tennessee House of Representatives. According to his biographer, Hans L. Trefousse, Johnson "demolished" the opposition in debate and won the election with almost a two to one margin. During his Greeneville days, Johnson joined the Tennessee Militia as a member of the 90th Regiment. He attained the rank of colonel, though while an enrolled member, Johnson was fined for an unknown offense. Afterwards, he was often addressed or referred to by his rank. In his first term in the legislature, which met in the state capital of Nashville, Johnson did not consistently vote with either the Democratic or the newly formed Whig Party, though he revered President Andrew Jackson, a Democrat and fellow Tennessean. The major parties were still determining their core values and policy proposals, with the party system in a state of flux. The Whig Party had organized in opposition to Jackson, fearing the concentration of power in the Executive Branch of the government; Johnson differed from the Whigs as he opposed more than minimal government spending and spoke against aid for the railroads, while his constituents hoped for improvements in transportation. After Brookins Campbell and the Whigs defeated Johnson for reelection in 1837, Johnson would not lose another race for thirty years. In 1839, he sought to regain his seat, initially as a Whig, but when another candidate sought the Whig nomination, he ran as a Democrat and was elected. From that time he supported the Democratic party and built a powerful political machine in Greene County. Johnson became a strong advocate of the Democratic Party, noted for his oratory, and in an era when public speaking both informed the public and entertained it, people flocked to hear him. In 1840, Johnson was selected as a presidential elector for Tennessee, giving him more statewide publicity. Although Democratic President Martin Van Buren was defeated by former Ohio senator William Henry Harrison, Johnson was instrumental in keeping Tennessee and Greene County in the Democratic column. He was elected to the Tennessee Senate in 1841, where he served a two-year term. He had achieved financial success in his tailoring business, but sold it to concentrate on politics. He had also acquired additional real estate, including a larger home and a farm (where his mother and stepfather took residence), and among his assets numbered eight or nine slaves. United States Representative (1843–1853) Having served in both houses of the state legislature, Johnson saw election to Congress as the next step in his political career. He engaged in a number of political maneuvers to gain Democratic support, including the displacement of the Whig postmaster in Greeneville, and defeated Jonesborough lawyer John A. Aiken by 5,495 votes to 4,892. In Washington, he joined a new Democratic majority in the House of Representatives. Johnson advocated for the interests of the poor, maintained an anti-abolitionist stance, argued for only limited spending by the government and opposed protective tariffs. With Eliza remaining in Greeneville, Congressman Johnson shunned social functions in favor of study in the Library of Congress. Although a fellow Tennessee Democrat, James K. Polk, was elected president in 1844, and Johnson had campaigned for him, the two men had difficult relations, and President Polk refused some of his patronage suggestions. Johnson believed, as did many Southern Democrats, that the Constitution protected private property, including slaves, and thus prohibited the federal and state governments from abolishing slavery. He won a second term in 1845 against William G. Brownlow, presenting himself as the defender of the poor against the aristocracy. In his second term, Johnson supported the Polk administration's decision to fight the Mexican War, seen by some Northerners as an attempt to gain territory to expand slavery westward, and opposed the Wilmot Proviso, a proposal to ban slavery in any territory gained from Mexico. He introduced for the first time his Homestead Bill, to grant to people willing to settle the land and gain title to it. This issue was especially important to Johnson because of his own humble beginnings. In the presidential election of 1848, the Democrats split over the slavery issue, and abolitionists formed the Free Soil Party, with former president Van Buren as their nominee. Johnson supported the Democratic candidate, former Michigan senator Lewis Cass. With the party split, Whig nominee General Zachary Taylor was easily victorious, and carried Tennessee. Johnson's relations with Polk remained poor; the President recorded of his final New Year's reception in 1849 that Johnson, due to national interest in new railroad construction and in response to the need for better transportation in his own district, also supported government assistance for the East Tennessee and Virginia Railroad. In his campaign for a fourth term, Johnson concentrated on three issues: slavery, homesteads and judicial elections. He defeated his opponent, Nathaniel G. Taylor, in August 1849, with a greater margin of victory than in previous campaigns. When the House convened in December, the party division caused by the Free Soil Party precluded the formation of the majority needed to elect a Speaker. Johnson proposed adoption of a rule allowing election of a Speaker by a plurality; some weeks later others took up a similar proposal, and Democrat Howell Cobb was elected. Once the Speaker election had concluded and Congress was ready to conduct legislative business, the issue of slavery took center stage. Northerners sought to admit California, a free state, to the Union. Kentucky's Henry Clay introduced in the Senate a series of resolutions, the Compromise of 1850, to admit California and pass legislation sought by each side. Johnson voted for all the provisions except for the abolition of slavery in the nation's capital. He pressed resolutions for constitutional amendments to provide for popular election of senators (then elected by state legislatures) and of the president (chosen by the Electoral College), and limiting the tenure of federal judges to 12 years. These were all defeated. A group of Democrats nominated Landon Carter Haynes to oppose Johnson as he sought a fifth term; the Whigs were so pleased with the internecine battle among the Democrats in the general election that they did not nominate a candidate of their own. The campaign included fierce debates: Johnson's main issue was the passage of the Homestead Bill; Haynes contended it would facilitate abolition. Johnson won the election by more than 1600 votes. Though he was not enamored of the party's presidential nominee in 1852, former New Hampshire senator Franklin Pierce, Johnson campaigned for him. Pierce was elected, but he failed to carry Tennessee. In 1852, Johnson managed to get the House to pass his Homestead Bill, but it failed in the Senate. The Whigs had gained control of the Tennessee legislature, and, under the leadership of Gustavus Henry, redrew the boundaries of Johnson's First District to make it a safe seat for their party. The Nashville Union termed this "Henry-mandering"; lamented Johnson, "I have no political future." Governor of Tennessee (1853–1857) If Johnson considered retiring from politics upon deciding not to seek reelection, he soon changed his mind. His political friends began to maneuver to get him the nomination for governor. The Democratic convention unanimously named him, though some party members were not happy at his selection. The Whigs had won the past two gubernatorial elections, and still controlled the legislature. That party nominated Henry, making the "Henry-mandering" of the First District an immediate issue. The two men debated in county seats the length of Tennessee before the meetings were called off two weeks before the August 1853 election due to illness in Henry's family. Johnson won the election by 63,413 votes to 61,163; some votes for him were cast in return for his promise to support Whig Nathaniel Taylor for his old seat in Congress. Tennessee's governor had little power: Johnson could propose legislation but not veto it, and most appointments were made by the Whig-controlled legislature. Nevertheless, the office was a "bully pulpit" that allowed him to publicize himself and his political views. He succeeded in getting the appointments he wanted in return for his endorsement of John Bell, a Whig, for one of the state's U.S. Senate seats. In his first biennial speech, Johnson urged simplification of the state judicial system, abolition of the Bank of Tennessee, and establishment of an agency to provide uniformity in weights and measures; the last was passed. Johnson was critical of the Tennessee common school system and suggested funding be increased via taxes, either statewide or county by county—a mixture of the two was passed. Reforms carried out during Johnson's time as governor included the foundation of the State's public library (making books available to all) and its first public school system, and the initiation of regular state fairs to benefit craftsmen and farmers. Although the Whig Party was on its final decline nationally, it remained strong in Tennessee, and the outlook for Democrats there in 1855 was poor. Feeling that reelection as governor was necessary to give him a chance at the higher offices he sought, Johnson agreed to make the run. Meredith P. Gentry received the Whig nomination. A series of more than a dozen vitriolic debates ensued. The issues in the campaign were slavery, the prohibition of alcohol, and the nativist positions of the Know Nothing Party. Johnson favored the first, but opposed the others. Gentry was more equivocal on the alcohol question, and had gained the support of the Know Nothings, a group Johnson portrayed as a secret society. Johnson was unexpectedly victorious, albeit with a narrower margin than in 1853. When the presidential election of 1856 approached, Johnson hoped to be nominated; some Tennessee county conventions designated him a "favorite son". His position that the best interests of the Union were served by slavery in some areas made him a practical compromise candidate for president. He was never a major contender; the nomination fell to former Pennsylvania senator James Buchanan. Though he was not impressed by either, Johnson campaigned for Buchanan and his running mate, John C. Breckinridge, who were elected. Johnson decided not to seek a third term as governor, with an eye towards election to the U.S. Senate. In 1857, while returning from Washington, his train derailed, causing serious damage to his right arm. This injury would trouble him in the years to come. United States Senator Homestead Bill advocate The victors in the 1857 state legislative campaign would, once they convened in October, elect a United States Senator. Former Whig governor William B. Campbell wrote to his uncle, "The great anxiety of the Whigs is to elect a majority in the legislature so as to defeat Andrew Johnson for senator. Should the Democrats have the majority, he will certainly be their choice, and there is no man living to whom the Americans and Whigs have as much antipathy as Johnson." The governor spoke widely in the campaign, and his party won the gubernatorial race and control of the legislature. Johnson's final address as governor gave him the chance to influence his electors, and he made proposals popular among Democrats. Two days later the legislature elected him to the Senate. The opposition was appalled, with the Richmond Whig newspaper referring to him as "the vilest radical and most unscrupulous demagogue in the Union". Johnson gained high office due to his proven record as a man popular among the small farmers and self-employed tradesmen who made up much of Tennessee's electorate. He called them the "plebeians"; he was less popular among the planters and lawyers who led the state Democratic Party, but none could match him as a vote-getter. After his death, one Tennessee voter wrote of him, "Johnson was always the same to everyone ... the honors heaped upon him did not make him forget to be kind to the humblest citizen." Always seen in impeccably tailored clothing, he cut an impressive figure, and had the stamina to endure lengthy campaigns with daily travel over bad roads leading to another speech or debate. Mostly denied the party's machinery, he relied on a network of friends, advisers, and contacts. One friend, Hugh Douglas, stated in a letter to him, "you have been in the way of our would be great men for a long time. At heart many of us never wanted you to be Governor only none of the rest of us Could have been elected at the time and we only wanted to use you. Then we did not want you to go to the Senate but the people would send you." The new senator took his seat when Congress convened in December 1857 (the term of his predecessor, James C. Jones, had expired in March). He came to Washington as usual without his wife and family; Eliza would visit Washington only once during Johnson's first time as senator, in 1860. Johnson immediately set about introducing the Homestead Bill in the Senate, but as most senators who supported it were Northern (many associated with the newly founded Republican Party), the matter became caught up in suspicions over the slavery issue. Southern senators felt that those who took advantage of the provisions of the Homestead Bill were more likely to be Northern non-slaveholders. The issue of slavery had been complicated by the Supreme Court's ruling earlier in the year in Dred Scott v. Sandford that slavery could not be prohibited in the territories. Johnson, a slaveholding senator from a Southern state, made a major speech in the Senate the following May in an attempt to convince his colleagues that the Homestead Bill and slavery were not incompatible. Nevertheless, Southern opposition was key to defeating the legislation, 30–22. In 1859, it failed on a procedural vote when Vice President Breckinridge broke a tie against the bill, and in 1860, a watered-down version passed both houses, only to be vetoed by Buchanan at the urging of Southerners. Johnson continued his opposition to spending, chairing a committee to control it. He argued against funding to build infrastructure in Washington, D.C., stating that it was unfair to expect state citizens to pay for the city's streets, even if it was the seat of government. He opposed spending money for troops to put down the revolt by the Mormons in Utah Territory, arguing for temporary volunteers as the United States should not have a standing army. Secession crisis In October 1859, abolitionist John Brown and sympathizers raided the federal arsenal at Harpers Ferry, Virginia (today West Virginia). Tensions in Washington between pro- and anti-slavery forces increased greatly. Johnson gave a major speech in the Senate in December, decrying Northerners who would endanger the Union by seeking to outlaw slavery. The Tennessee senator stated that "all men are created equal" from the Declaration of Independence did not apply to African Americans, since the Constitution of Illinois contained that phrase—and that document barred voting by African Americans. Johnson, by this time, was a wealthy man who owned 14 slaves. Johnson hoped that he would be a compromise candidate for the presidential nomination as the Democratic Party tore itself apart over the slavery question. Busy with the Homestead Bill during the 1860 Democratic National Convention in Charleston, South Carolina, he sent two of his sons and his chief political adviser to represent his interests in the backroom deal-making. The convention deadlocked, with no candidate able to gain the required two-thirds vote, but the sides were too far apart to consider Johnson as a compromise. The party split, with Northerners backing Illinois Senator Stephen Douglas while Southerners, including Johnson, supported Vice President Breckinridge for president. With former Tennessee senator John Bell running a fourth-party candidacy and further dividing the vote, the Republican Party elected its first president, former Illinois representative Abraham Lincoln. The election of Lincoln, known to be against the spread of slavery, was unacceptable to many in the South. Although secession from the Union had not been an issue in the campaign, talk of it began in the Southern states. Johnson took to the Senate floor after the election, giving a speech well received in the North, "I will not give up this government ... No; I intend to stand by it ... and I invite every man who is a patriot to ... rally around the altar of our common country ... and swear by our God, and all that is sacred and holy, that the Constitution shall be saved, and the Union preserved." As Southern senators announced they would resign if their states seceded, he reminded Mississippi Senator Jefferson Davis that if Southerners would only hold to their seats, the Democrats would control the Senate, and could defend the South's interests against any infringement by Lincoln. Gordon-Reed points out that while Johnson's belief in an indissoluble Union was sincere, he had alienated Southern leaders, including Davis, who would soon be the president of the Confederate States of America, formed by the seceding states. If the Tennessean had backed the Confederacy, he would have had small influence in its government. Johnson returned home when his state took up the issue of secession. His successor as governor, Isham G. Harris, and the legislature organized a referendum on whether to have a constitutional convention to authorize secession; when that failed, they put the question of leaving the Union to a popular vote. Despite threats on Johnson's life, and actual assaults, he campaigned against both questions, sometimes speaking with a gun on the lectern before him. Although Johnson's eastern region of Tennessee was largely against secession, the second referendum passed, and in June 1861, Tennessee joined the Confederacy. Believing he would be killed if he stayed, Johnson fled through the Cumberland Gap, where his party was in fact shot at. He left his wife and family in Greeneville. As the only member from a seceded state to remain in the Senate and the most prominent Southern Unionist, Johnson had Lincoln's ear in the early months of the war. With most of Tennessee in Confederate hands, Johnson spent congressional recesses in Kentucky and Ohio, trying in vain to convince any Union commander who would listen to conduct an operation into East Tennessee. Military Governor of Tennessee Johnson's first tenure in the Senate came to a conclusion in March 1862 when Lincoln appointed him military governor of Tennessee. Much of the central and western portions of that seceded state had been recovered. Although some argued that civil government should simply resume once the Confederates were defeated in an area, Lincoln chose to use his power as commander in chief to appoint military governors over Union-controlled Southern regions. The Senate quickly confirmed Johnson's nomination along with the rank of brigadier general. In response, the Confederates confiscated his land and his slaves, and turned his home into a military hospital. Later in 1862, after his departure from the Senate and in the absence of most Southern legislators, the Homestead Bill was finally enacted. Along with legislation for land-grant colleges and for the transcontinental railroad, the Homestead Bill has been credited with opening the American West to settlement. As military governor, Johnson sought to eliminate rebel influence in the state. He demanded loyalty oaths from public officials, and shut down all newspapers owned by Confederate sympathizers. Much of eastern Tennessee remained in Confederate hands, and the ebb and flow of war during 1862 sometimes brought Confederate control again close to Nashville. However, the Confederates allowed his wife and family to pass through the lines to join him. Johnson undertook the defense of Nashville as well as he could, though the city was continually harassed by cavalry raids led by General Nathan Bedford Forrest. Relief from Union regulars did not come until General William S. Rosecrans defeated the Confederates at Murfreesboro in early 1863. Much of eastern Tennessee was captured later that year. When Lincoln issued the Emancipation Proclamation in January 1863, declaring freedom for all slaves in Confederate-held areas, he exempted Tennessee at Johnson's request. The proclamation increased the debate over what should become of the slaves after the war, as not all Unionists supported abolition. Johnson finally decided that slavery had to end. He wrote, "If the institution of slavery ... seeks to overthrow it [the Government], then the Government has a clear right to destroy it". He reluctantly supported efforts to enlist former slaves into the Union Army, feeling that African Americans should perform menial tasks to release white Americans to do the fighting. Nevertheless, he succeeded in recruiting 20,000 black soldiers to serve the Union. Vice Presidency (1865) In 1860, Lincoln's running mate had been Senator Hannibal Hamlin of Maine. Although Hamlin had served competently, was in good health, and was willing to run again, Johnson emerged as running mate for Lincoln's reelection bid in 1864. Lincoln considered several War Democrats for the ticket in 1864, and sent an agent to sound out General Benjamin Butler as a possible running mate. In May 1864, the president dispatched General Daniel Sickles to Nashville on a fact-finding mission. Although Sickles denied that he was there either to investigate or interview the military governor, Johnson biographer Hans L. Trefousse believes that Sickles's trip was connected to Johnson's subsequent nomination for vice president. According to historian Albert Castel in his account of Johnson's presidency, Lincoln was impressed by Johnson's administration of Tennessee. Gordon-Reed points out that while the Lincoln-Hamlin ticket might have been considered geographically balanced in 1860, "having Johnson, the southern War Democrat, on the ticket sent the right message about the folly of secession and the continuing capacity for union within the country." Another factor was the desire of Secretary of State William Seward to frustrate the vice-presidential candidacy of fellow New Yorker and former senator Daniel S. Dickinson, a War Democrat, as Seward would probably have had to yield his place if another New Yorker became vice president. Johnson, once he was told by reporters the likely purpose of Sickles' visit, was active on his own behalf, delivering speeches and having his political friends work behind the scenes to boost his candidacy. To sound a theme of unity in 1864, Lincoln ran under the banner of the National Union Party, rather than that of the Republicans. At the party's convention in Baltimore in June, Lincoln was easily nominated, although there had been some talk of replacing him with a Cabinet officer or one of the more successful generals. After the convention backed Lincoln, former Secretary of War Simon Cameron offered a resolution to nominate Hamlin, but it was defeated. Johnson was nominated for vice president by C.M. Allen of Indiana with an Iowa delegate as seconder. On the first ballot, Johnson led with 200 votes to 150 for Hamlin and 108 for Dickinson. On the second ballot, Kentucky switched to vote for Johnson, beginning a stampede. Johnson was named on the second ballot with 491 votes to Hamlin's 17 and eight for Dickinson; the nomination was made unanimous. Lincoln expressed pleasure at the result, "Andy Johnson, I think, is a good man." When word reached Nashville, a crowd assembled and the military governor obliged with a speech contending his selection as a Southerner meant that the rebel states had not actually left the Union. Although it was unusual at the time for a national candidate to actively campaign, Johnson gave a number of speeches in Tennessee, Kentucky, Ohio, and Indiana. He also sought to boost his chances in Tennessee while reestablishing civil government by making the loyalty oath even more restrictive, in that voters would now have to swear that they opposed making a settlement with the Confederacy. The Democratic candidate for president, George McClellan, hoped to avoid additional bloodshed by negotiation, and so the stricter loyalty oath effectively disenfranchised his supporters. Lincoln declined to override Johnson, and their ticket took the state by 25,000 votes. Congress refused to count Tennessee's electoral votes, but Lincoln and Johnson did not need them, having won in most states that had voted, and easily secured the election. Now Vice President-elect, Johnson was eager to complete the work of reestablishing civilian government in Tennessee, although the timetable for the election of a new governor did not allow it to take place until after Inauguration Day, March 4. He hoped to remain in Nashville to complete his task, but was told by Lincoln's advisers that he could not stay, but would be sworn in with Lincoln. In these months, Union troops finished the retaking of eastern Tennessee, including Greeneville. Just before his departure, the voters of Tennessee ratified a new constitution, which abolished slavery, on February 22, 1865. One of Johnson's final acts as military governor was to certify the results. Johnson traveled to Washington to be sworn into office, although according to Gordon-Reed, "in light of what happened on March 4, 1865, it might have been better if Johnson had stayed in Nashville." Johnson may have been ill; Castel cited typhoid fever, though Gordon-Reed notes that there is no independent evidence for that diagnosis. On the evening of March 3, Johnson attended a party in his honor at which he drank heavily. Hung over the following morning at the Capitol, he asked Vice President Hamlin for some whiskey. Hamlin produced a bottle, and Johnson took two stiff drinks, stating "I need all the strength for the occasion I can have." In the Senate Chamber, Johnson delivered a rambling address as Lincoln, the Congress, and dignitaries looked on. Almost incoherent at times, he finally meandered to a halt, whereupon Hamlin hastily swore him in as vice president. Lincoln, who had watched sadly during the debacle, then went to his own swearing-in outside the Capitol, and delivered his acclaimed Second Inaugural Address. In the weeks after the inauguration, Johnson only presided over the Senate briefly, and hid from public ridicule at the Maryland home of a friend, Francis Preston Blair. When he did return to Washington, it was with the intent of leaving for Tennessee to reestablish his family in Greeneville. Instead, he remained after word came that General Ulysses S. Grant had captured the Confederate capital of Richmond, Virginia, presaging the end of the war. Lincoln stated, in response to criticism of Johnson's behavior, that "I have known Andy Johnson for many years; he made a bad slip the other day, but you need not be scared; Andy ain't a drunkard." Presidency (1865–1869) Accession On the afternoon of April 14, 1865, Lincoln and Johnson met for the first time since the inauguration. Trefousse states that Johnson wanted to "induce Lincoln not to be too lenient with traitors"; Gordon-Reed agrees. That night, President Lincoln was shot and mortally wounded at Ford's Theatre by John Wilkes Booth, a Confederate sympathizer. The shooting of the President was part of a conspiracy to assassinate Lincoln, Johnson, and Seward the same night. Seward barely survived his wounds, while Johnson escaped attack as his would-be assassin, George Atzerodt, got drunk instead of killing the vice president. Leonard J. Farwell, a fellow boarder at the Kirkwood House, awoke Johnson with news of Lincoln's shooting. Johnson rushed to the President's deathbed, where he remained a short time, on his return promising, "They shall suffer for this. They shall suffer for this." Lincoln died at 7:22 am the next morning; Johnson's swearing-in occurred between 10 and 11 am with Chief Justice Salmon P. Chase presiding in the presence of most of the Cabinet. Johnson's demeanor was described by the newspapers as "solemn and dignified". Some Cabinet members had last seen Johnson, apparently drunk, at the inauguration. At noon, Johnson conducted his first Cabinet meeting in the Treasury Secretary's office, and asked all members to remain in their positions. The events of the assassination resulted in speculation, then and subsequently, concerning Johnson and what the conspirators might have intended for him. In the vain hope of having his life spared after his capture, Atzerodt spoke much about the conspiracy, but did not say anything to indicate that the plotted assassination of Johnson was merely a ruse. Conspiracy theorists point to the fact that on the day of the assassination, Booth came to the Kirkwood House and left one of his cards with Johnson's private secretary, William A. Browning. The message on it was: "Don't wish to disturb you. Are you at home? J. Wilkes Booth." Johnson presided with dignity over Lincoln's funeral ceremonies in Washington, before his predecessor's body was sent home to Springfield, Illinois, for interment. Shortly after Lincoln's death, Union General William T. Sherman reported he had, without consulting Washington, reached an armistice agreement with Confederate General Joseph E. Johnston for the surrender of Confederate forces in North Carolina in exchange for the existing state government remaining in power, with private property rights (slaves) to be respected. This did not even grant freedom to those in slavery. This was not acceptable to Johnson or the Cabinet, who sent word for Sherman to secure the surrender without making political deals, which he did. Further, Johnson placed a $100,000 bounty (equivalent to $ in ) on Confederate President Davis, then a fugitive, which gave Johnson the reputation of a man who would be tough on the South. More controversially, he permitted the execution of Mary Surratt for her part in Lincoln's assassination. Surratt was executed with three others, including Atzerodt, on July 7, 1865. Reconstruction Background Upon taking office, Johnson faced the question of what to do with the former Confederacy. President Lincoln had authorized loyalist governments in Virginia, Arkansas, Louisiana, and Tennessee as the Union came to control large parts of those states and advocated a ten percent plan that would allow elections after ten percent of the voters in any state took an oath of future loyalty to the Union. Congress considered this too lenient; its own plan, requiring a majority of voters to take the loyalty oath, passed both houses in 1864, but Lincoln pocket vetoed it. Johnson had three goals in Reconstruction. He sought a speedy restoration of the states, on the grounds that they had never truly left the Union, and thus should again be recognized once loyal citizens formed a government. To Johnson, African-American suffrage was a delay and a distraction; it had always been a state responsibility to decide who should vote. Second, political power in the Southern states should pass from the planter class to his beloved "plebeians". Johnson feared that the freedmen, many of whom were still economically bound to their former masters, might vote at their direction. Johnson's third priority was election in his own right in 1868, a feat no one who had succeeded a deceased president had managed to accomplish, attempting to secure a Democratic anti-Congressional Reconstruction coalition in the South. The Republicans had formed a number of factions. The Radical Republicans sought voting and other civil rights for African Americans. They believed that the freedmen could be induced to vote Republican in gratitude for emancipation, and that black votes could keep the Republicans in power and Southern Democrats, including former rebels, out of influence. They believed that top Confederates should be punished. The Moderate Republicans sought to keep the Democrats out of power at a national level, and prevent former rebels from resuming power. They were not as enthusiastic about the idea of African-American suffrage as their Radical colleagues, either because of their own local political concerns, or because they believed that the freedman would be likely to cast his vote badly. Northern Democrats favored the unconditional restoration of the Southern states. They did not support African-American suffrage, which might threaten Democratic control in the South. Presidential Reconstruction Johnson was initially left to devise a Reconstruction policy without legislative intervention, as Congress was not due to meet again until December 1865. Radical Republicans told the President that the Southern states were economically in a state of chaos and urged him to use his leverage to insist on rights for freedmen as a condition of restoration to the Union. But Johnson, with the support of other officials including Seward, insisted that the franchise was a state, not a federal matter. The Cabinet was divided on the issue. Johnson's first Reconstruction actions were two proclamations, with the unanimous backing of his Cabinet, on May 29. One recognized the Virginia government led by provisional Governor Francis Pierpont. The second provided amnesty for all ex-rebels except those holding property valued at $20,000 or more; it also appointed a temporary governor for North Carolina and authorized elections. Neither of these proclamations included provisions regarding black suffrage or freedmen's rights. The President ordered constitutional conventions in other former rebel states. As Southern states began the process of forming governments, Johnson's policies received considerable public support in the North, which he took as unconditional backing for quick reinstatement of the South. While he received such support from the white South, he underestimated the determination of Northerners to ensure that the war had not been fought for nothing. It was important, in Northern public opinion, that the South acknowledge its defeat, that slavery be ended, and that the lot of African Americans be improved. Voting rights were less important—after all, only a handful of Northern states (mostly in New England) gave African-American men the right to vote on the same basis as whites, and in late 1865, Connecticut, Wisconsin, and Minnesota voted down African-American suffrage proposals by large margins. Northern public opinion tolerated Johnson's inaction on black suffrage as an experiment, to be allowed if it quickened Southern acceptance of defeat. Instead, white Southerners felt emboldened. A number of Southern states passed Black Codes, binding African-American laborers to farms on annual contracts they could not quit, and allowing law enforcement at whim to arrest them for vagrancy and rent out their labor. Most Southerners elected to Congress were former Confederates, with the most prominent being Georgia Senator-designate and former Confederate vice president Alexander Stephens. Congress assembled in early December 1865; Johnson's conciliatory annual message to them was well received. Nevertheless, Congress refused to seat the Southern legislators and established a committee to recommend appropriate Reconstruction legislation. Northerners were outraged at the idea of unrepentant Confederate leaders, such as Stephens, rejoining the federal government at a time when emotional wounds from the war remained raw. They saw the Black Codes placing African Americans in a position barely above slavery. Republicans also feared that restoration of the Southern states would return the Democrats to power. In addition, according to David O. Stewart in his book on Johnson's impeachment, "the violence and poverty that oppressed the South would galvanize the opposition to Johnson". Break with the Republicans: 1866 Congress was reluctant to confront the President, and initially only sought to fine-tune Johnson's policies towards the South. According to Trefousse, "If there was a time when Johnson could have come to an agreement with the moderates of the Republican Party, it was the period following the return of Congress". The President was unhappy about the provocative actions of the Southern states, and about the continued control by the antebellum elite there, but made no statement publicly, believing that Southerners had a right to act as they did, even if it was unwise to do so. By late January 1866, he was convinced that winning a showdown with the Radical Republicans was necessary to his political plans – both for the success of Reconstruction and for reelection in 1868. He would have preferred that the conflict arise over the legislative efforts to enfranchise African Americans in the District of Columbia, a proposal that had been defeated overwhelmingly in an all-white referendum. A bill to accomplish this passed the House of Representatives, but to Johnson's disappointment, stalled in the Senate before he could veto it. Illinois Senator Lyman Trumbull, leader of the Moderate Republicans and Chairman of the Judiciary Committee, was anxious to reach an understanding with the President. He ushered through Congress a bill extending the Freedmen's Bureau beyond its scheduled abolition in 1867, and the first Civil Rights Bill, to grant citizenship to the freedmen. Trumbull met several times with Johnson and was convinced the President would sign the measures (Johnson rarely contradicted visitors, often fooling those who met with him into thinking he was in accord). In fact, the President opposed both bills as infringements on state sovereignty. Additionally, both of Trumbull's bills were unpopular among white Southerners, whom Johnson hoped to include in his new party. Johnson vetoed the Freedman's Bureau bill on February 18, 1866, to the delight of white Southerners and the puzzled anger of Republican legislators. He considered himself vindicated when a move to override his veto failed in the Senate the following day. Johnson believed that the Radicals would now be isolated and defeated and that the moderate Republicans would form behind him; he did not understand that Moderates also wanted to see African Americans treated fairly. On February 22, 1866, Washington's Birthday, Johnson gave an impromptu speech to supporters who had marched to the White House and called for an address in honor of the first president. In his hour-long speech, he instead referred to himself over 200 times. More damagingly, he also spoke of "men ... still opposed to the Union" to whom he could not extend the hand of friendship he gave to the South. When called upon by the crowd to say who they were, Johnson named Pennsylvania Congressman Thaddeus Stevens, Massachusetts Senator Charles Sumner, and abolitionist Wendell Phillips, and accused them of plotting his assassination. Republicans viewed the address as a declaration of war, while one Democratic ally estimated Johnson's speech cost the party 200,000 votes in the 1866 congressional midterm elections. Although strongly urged by moderates to sign the Civil Rights Act of 1866, Johnson broke decisively with them by vetoing it on March 27. In his veto message, he objected to the measure because it conferred citizenship on the freedmen at a time when 11 out of 36 states were unrepresented in the Congress, and that it discriminated in favor of African Americans and against whites. Within three weeks, Congress had overridden his veto, the first time that had been done on a major bill in American history. The veto, often seen as a key mistake of Johnson's presidency, convinced moderates there was no hope of working with him. Historian Eric Foner, in his volume on Reconstruction, views it as "the most disastrous miscalculation of his political career". According to Stewart, the veto was "for many his defining blunder, setting a tone of perpetual confrontation with Congress that prevailed for the rest of his presidency". Congress also proposed the Fourteenth Amendment to the states. Written by Trumbull and others, it was sent for ratification by state legislatures in a process in which the president plays no part, though Johnson opposed it. The amendment was designed to put the key provisions of the Civil Rights Act into the Constitution, but also went further. The amendment extended citizenship to every person born in the United States (except Indians on reservations), penalized states that did not give the vote to freedmen, and most importantly, created new federal civil rights that could be protected by federal courts. It also guaranteed that the federal debt would be paid and forbade repayment of Confederate war debts. Further, it disqualified many former Confederates from office, although the disability could be removed — by Congress, not the president. Both houses passed the Freedmen's Bureau Act a second time, and again the President vetoed it; this time, the veto was overridden. By the summer of 1866, when Congress finally adjourned, Johnson's method of restoring states to the Union by executive fiat, without safeguards for the freedmen, was in deep trouble. His home state of Tennessee ratified the Fourteenth Amendment despite the President's opposition. When Tennessee did so, Congress immediately seated its proposed delegation, embarrassing Johnson. Efforts to compromise failed, and a political war ensued between the united Republicans on one side, and on the other, Johnson and his Northern and Southern allies in the Democratic Party. He called a convention of the National Union Party. Republicans had returned to using their previous identifier; Johnson intended to use the discarded name to unite his supporters and gain election to a full term, in 1868. The battleground was the election of 1866; Southern states were not allowed to vote. Johnson campaigned vigorously, undertaking a public speaking tour, known as the "Swing Around the Circle". The trip, including speeches in Chicago, St. Louis, Indianapolis, and Columbus, proved politically disastrous, with the President making controversial comparisons between himself and Christ, and engaging in arguments with hecklers. These exchanges were attacked as beneath the dignity of the presidency. The Republicans won by a landslide, increasing their two-thirds majority in Congress, and made plans to control Reconstruction. Johnson blamed the Democrats for giving only lukewarm support to the National Union movement. Radical Reconstruction Even with the Republican victory in November 1866, Johnson considered himself in a strong position. The Fourteenth Amendment had been ratified by none of the Southern or border states except Tennessee, and had been rejected in Kentucky, Delaware, and Maryland. As the amendment required ratification by three-quarters of the states to become part of the Constitution, he believed the deadlock would be broken in his favor, leading to his election in 1868. Once it reconvened in December 1866, an energized Congress began passing legislation, often over a presidential veto; this included the District of Columbia voting bill. Congress admitted Nebraska to the Union over a veto, and the Republicans gained two senators and a state that promptly ratified the amendment. Johnson's veto of a bill for statehood for Colorado Territory was sustained; enough senators agreed that a district with a population of 30,000 was not yet worthy of statehood to win the day. In January 1867, Congressman Stevens introduced legislation to dissolve the Southern state governments and reconstitute them into five military districts, under martial law. The states would begin again by holding constitutional conventions. African Americans could vote for or become delegates; former Confederates could not. In the legislative process, Congress added to the bill that restoration to the Union would follow the state's ratification of the Fourteenth Amendment, and completion of the process of adding it to the Constitution. Johnson and the Southerners attempted a compromise, whereby the South would agree to a modified version of the amendment without the disqualification of former Confederates, and for limited black suffrage. The Republicans insisted on the full language of the amendment, and the deal fell through. Although Johnson could have pocket vetoed the First Reconstruction Act as it was presented to him less than ten days before the end of the Thirty-Ninth Congress, he chose to veto it directly on March 2, 1867; Congress overruled him the same day. Also on March 2, Congress passed the Tenure of Office Act over the President's veto, in response to statements during the Swing Around the Circle that he planned to fire Cabinet secretaries who did not agree with him. This bill, requiring Senate approval for the firing of Cabinet members during the tenure of the president who appointed them and for one month afterwards, was immediately controversial, with some senators doubting that it was constitutional or that its terms applied to Johnson, whose key Cabinet officers were Lincoln holdovers. Impeachment Secretary of War Edwin Stanton was an able and hard-working man, but difficult to deal with. Johnson both admired and was exasperated by his War Secretary, who, in combination with General of the Army Grant, worked to undermine the president's Southern policy from within his own administration. Johnson considered firing Stanton, but respected him for his wartime service as secretary. Stanton, for his part, feared allowing Johnson to appoint his successor and refused to resign, despite his public disagreements with his president. The new Congress met for a few weeks in March 1867, then adjourned, leaving the House Committee on the Judiciary behind, charged with reporting back to the full House whether there were grounds for Johnson to be impeached. This committee duly met, examined the President's bank accounts, and summoned members of the Cabinet to testify. When a federal court released former Confederate president Davis on bail on May 13 (he had been captured shortly after the war), the committee investigated whether the President had impeded the prosecution. It learned that Johnson was eager to have Davis tried. A bipartisan majority of the committee voted down impeachment charges; the committee adjourned on June 3. Later in June, Johnson and Stanton battled over the question of whether the military officers placed in command of the South could override the civil authorities. The President had Attorney General Henry Stanbery issue an opinion backing his position that they could not. Johnson sought to pin down Stanton either as for, and thus endorsing Johnson's position, or against, showing himself to be opposed to his president and the rest of the Cabinet. Stanton evaded the point in meetings and written communications. When Congress reconvened in July, it passed a Reconstruction Act against Johnson's position, waited for his veto, overrode it, and went home. In addition to clarifying the powers of the generals, the legislation also deprived the President of control over the Army in the South. With Congress in recess until November, Johnson decided to fire Stanton and relieve one of the military commanders, General Philip Sheridan, who had dismissed the governor of Texas and installed a replacement with little popular support. Johnson was initially deterred by a strong objection from Grant, but on August 5, the President demanded Stanton's resignation; the secretary refused to quit with Congress out of session. Johnson then suspended him pending the next meeting of Congress as permitted under the Tenure of Office Act; Grant agreed to serve as temporary replacement while continuing to lead the Army. Grant, under protest, followed Johnson's order transferring Sheridan and another of the district commanders, Daniel Sickles, who had angered Johnson by firmly following Congress's plan. The President also issued a proclamation pardoning most Confederates, exempting those who held office under the Confederacy, or who had served in federal office before the war but had breached their oaths. Although Republicans expressed anger with his actions, the 1867 elections generally went Democratic. No seats in Congress were directly elected in the polling, but the Democrats took control of the Ohio General Assembly, allowing them to defeat for reelection one of Johnson's strongest opponents, Senator Benjamin Wade. Voters in Ohio, Connecticut, and Minnesota turned down propositions to grant African Americans the vote. The adverse results momentarily put a stop to Republican calls to impeach Johnson, who was elated by the elections. Nevertheless, once Congress met in November, the Judiciary Committee reversed itself and passed a resolution of impeachment against Johnson. After much debate about whether anything the President had done was a high crime or misdemeanor, the standard under the Constitution, the resolution was defeated by the House of Representatives on December 7, 1867, by a vote of 57 in favor to 108 opposed. Johnson notified Congress of Stanton's suspension and Grant's interim appointment. In January 1868, the Senate disapproved of his action, and reinstated Stanton, contending the President had violated the Tenure of Office Act. Grant stepped aside over Johnson's objection, causing a complete break between them. Johnson then dismissed Stanton and appointed Lorenzo Thomas to replace him. Stanton refused to leave his office, and on February 24, 1868, the House impeached the President for intentionally violating the Tenure of Office Act, by a vote of 128 to 47. The House subsequently adopted eleven articles of impeachment, for the most part alleging that he had violated the Tenure of Office Act, and had questioned the legitimacy of Congress. On March 5, 1868, the impeachment trial began in the Senate and lasted almost three months; Congressmen George S. Boutwell, Benjamin Butler and Thaddeus Stevens acted as managers for the House, or prosecutors, and William M. Evarts, Benjamin R. Curtis and former Attorney General Stanbery were Johnson's counsel; Chief Justice Chase served as presiding judge. The defense relied on the provision of the Tenure of Office Act that made it applicable only to appointees of the current administration. Since Lincoln had appointed Stanton, the defense maintained Johnson had not violated the act, and also argued that the President had the right to test the constitutionality of an act of Congress. Johnson's counsel insisted that he make no appearance at the trial, nor publicly comment about the proceedings, and except for a pair of interviews in April, he complied. Johnson maneuvered to gain an acquittal; for example, he pledged to Iowa Senator James W. Grimes that he would not interfere with Congress's Reconstruction efforts. Grimes reported to a group of Moderates, many of whom voted for acquittal, that he believed the President would keep his word. Johnson also promised to install the respected John Schofield as War Secretary. Kansas Senator Edmund G. Ross received assurances that the new, Radical-influenced constitutions ratified in South Carolina and Arkansas would be transmitted to the Congress without delay, an action which would give him and other senators political cover to vote for acquittal. One reason senators were reluctant to remove the President was that his successor would have been Ohio Senator Wade, the president pro tempore of the Senate. Wade, a lame duck who left office in early 1869, was a Radical who supported such measures as women's suffrage, placing him beyond the pale politically in much of the nation. Additionally, a President Wade was seen as an obstacle to Grant's ambitions. With the dealmaking, Johnson was confident of the result in advance of the verdict, and in the days leading up to the ballot, newspapers reported that Stevens and his Radicals had given up. On May 16, the Senate voted on the 11th article of impeachment, accusing Johnson of firing Stanton in violation of the Tenure of Office of Act once the Senate had overturned his suspension. Thirty-five senators voted "guilty" and 19 "not guilty", thus falling short by a single vote of the two-thirds majority required for conviction under the Constitution. Seven Republicans—Senators Grimes, Ross, Trumbull, William Pitt Fessenden, Joseph S. Fowler, John B. Henderson, and Peter G. Van Winkle—voted to acquit the President. With Stevens bitterly disappointed at the result, the Senate then adjourned for the Republican National Convention; Grant was nominated for president. The Senate returned on May 26 and voted on the second and third articles, with identical 35–19 results. Faced with those results, Johnson's opponents gave up and dismissed proceedings. Stanton "relinquished" his office on May 26, and the Senate subsequently confirmed Schofield. When Johnson renominated Stanbery to return to his position as Attorney General after his service as a defense manager, the Senate refused to confirm him. Allegations were made at the time and again later that bribery dictated the outcome of the trial. Even when it was in progress, Representative Butler began an investigation, held contentious hearings, and issued a report, unendorsed by any other congressman. Butler focused on a New York–based "Astor House Group", supposedly led by political boss and editor Thurlow Weed. This organization was said to have raised large sums of money from whiskey interests through Cincinnati lawyer Charles Woolley to bribe senators to acquit Johnson. Butler went so far as to imprison Woolley in the Capitol building when he refused to answer questions, but failed to prove bribery. Foreign policy Soon after taking office as president, Johnson reached an accord with Secretary of State William H. Seward that there would be no change in foreign policy. In practice, this meant that Seward would continue to run things as he had under Lincoln. Seward and Lincoln had been rivals for the nomination in 1860; the victor hoped that Seward would succeed him as president in 1869. At the time of Johnson's accession, the French had intervened in Mexico, sending troops there. While many politicians had indulged in saber rattling over the Mexican matter, Seward preferred quiet diplomacy, warning the French through diplomatic channels that their presence in Mexico was unacceptable. Although the President preferred a more aggressive approach, Seward persuaded him to follow his lead. In April 1866, the French government informed Seward that its troops would be brought home in stages, to conclude by November 1867. On August 14, 1866, Johnson and his cabinet gave a reception for Queen Emma of Hawaii who was returning to Hawaii after her trip to Britain and Europe. Seward was an expansionist, and sought opportunities to gain territory for the United States. After the loss of the Crimean War in the 1850s, the Russian government saw its North American colony (today Alaska) as a financial liability, and feared losing control to Britain whose troops would easily swoop in and annex the territory from neighboring Canada in any future conflict. Negotiations between Russia and the U.S. over the sale of Alaska were halted due to the outbreak of the Civil War, but after the U.S. victory in the war, talks resumed. Russia instructed its minister in Washington, Baron Eduard de Stoeckl, to negotiate a sale. De Stoeckl did so deftly, getting Seward to raise his offer from $5 million (coincidentally, the minimum that Russia had instructed de Stoeckl to accept) to $7 million, and then getting $200,000 added by raising various objections. This sum of $7.2 million is equivalent to $ in present-day terms. On March 30, 1867, de Stoeckl and Seward signed the treaty, working quickly as the Senate was about to adjourn. Johnson and Seward took the signed document to the President's Room in the Capitol, only to be told there was no time to deal with the matter before adjournment. The President summoned the Senate into session to meet on April 1; that body approved the treaty, 37–2. Emboldened by his success in Alaska, Seward sought acquisitions elsewhere. His only success was staking an American claim to uninhabited Wake Island in the Pacific, which would be officially claimed by the U.S. in 1898. He came close with the Danish West Indies as Denmark agreed to sell and the local population approved the transfer in a plebiscite, but the Senate never voted on the treaty and it expired. Another treaty that fared badly was the Johnson-Clarendon convention, negotiated in settlement of the Alabama Claims, for damages to American shipping from British-built Confederate raiders. Negotiated by the United States Minister to Britain, former Maryland senator Reverdy Johnson, in late 1868, it was ignored by the Senate during the remainder of the President's term. The treaty was rejected after he left office, and the Grant administration later negotiated considerably better terms from Britain. Administration and Cabinet Judicial appointments Johnson appointed nine Article III federal judges during his presidency, all to United States district courts; he did not appoint a justice to serve on the Supreme Court. In April 1866, he nominated Henry Stanbery to fill the vacancy left with the death of John Catron, but Congress eliminated the seat to prevent the appointment, and to ensure that he did not get to make any appointments eliminated the next vacancy as well, providing that the court would shrink by one justice when one next departed from office. Johnson appointed his Greeneville crony, Samuel Milligan, to the United States Court of Claims, where he served from 1868 until his death in 1874. Reforms initiated In June 1866, Johnson signed the Southern Homestead Act into law, believing that the legislation would assist poor whites. Around 28,000 land claims were successfully patented, although few former slaves benefitted from the law, fraud was rampant, and much of the best land was off-limits, reserved for grants to veterans or railroads. In June 1868, Johnson signed an eight-hour law passed by Congress that established an eight-hour workday for laborers and mechanics employed by the Federal Government. Although Johnson told members of a Workingmen's party delegation in Baltimore that he could not directly commit himself to an eight-hour day, he nevertheless told the same delegation that he greatly favoured the "shortest number of hours consistent with the interests of all". According to Richard F. Selcer, however, the good intentions behind the law were "immediately frustrated" as wages were cut by 20%. Completion of term Johnson sought nomination by the 1868 Democratic National Convention in New York in July 1868. He remained very popular among Southern whites, and boosted that popularity by issuing, just before the convention, a pardon ending the possibility of criminal proceedings against any Confederate not already indicted, meaning that only Davis and a few others still might face trial. On the first ballot, Johnson was second to former Ohio representative George H. Pendleton, who had been his Democratic opponent for vice president in 1864. Johnson's support was mostly from the South, and fell away as the ballots passed. On the 22nd ballot, former New York governor Horatio Seymour was nominated, and the President received only four votes, all from Tennessee. The conflict with Congress continued. Johnson sent Congress proposals for amendments to limit the president to a single six-year term and make the president and the Senate directly elected, and for term limits for judges. Congress took no action on them. When the President was slow to officially report ratifications of the Fourteenth Amendment by the new Southern legislatures, Congress passed a bill, again over his veto, requiring him to do so within ten days of receipt. He still delayed as much as he could, but was required, in July 1868, to report the ratifications making the amendment part of the Constitution. Seymour's operatives sought Johnson's support, but he long remained silent on the presidential campaign. It was not until October, with the vote already having taken place in some states, that he mentioned Seymour at all, and he never endorsed him. Nevertheless, Johnson regretted Grant's victory, in part because of their animus from the Stanton affair. In his annual message to Congress in December, Johnson urged the repeal of the Tenure of Office Act and told legislators that had they admitted their Southern colleagues in 1865, all would have been well. He celebrated his 60th birthday in late December with a party for several hundred children, though not including those of President-elect Grant, who did not allow his to go. On Christmas Day 1868, Johnson issued a final amnesty, this one covering everyone, including Davis. He also issued, in his final months in office, pardons for crimes, including one for Dr. Samuel Mudd, controversially convicted of involvement in the Lincoln assassination (he had set Booth's broken leg) and imprisoned in Fort Jefferson on Florida's Dry Tortugas. On March 3, the President hosted a large public reception at the White House on his final full day in office. Grant had made it known that he was unwilling to ride in the same carriage as Johnson, as was customary, and Johnson refused to go to the inauguration at all. Despite an effort by Seward to prompt a change of mind, he spent the morning of March 4 finishing last-minute business, and then shortly after noon rode from the White House to the home of a friend. Post-presidency (1869–1875) After leaving the presidency, Johnson remained for some weeks in Washington, then returned to Greeneville for the first time in eight years. He was honored with large public celebrations along the way, especially in Tennessee, where cities hostile to him during the war hung out welcome banners. He had arranged to purchase a large farm near Greeneville to live on after his presidency. Some expected Johnson to run for Governor of Tennessee or for the Senate again, while others thought that he would become a railroad executive. Johnson found Greeneville boring, and his private life was embittered by the suicide of his son Robert in 1869. Seeking vindication for himself, and revenge against his political enemies, he launched a Senate bid soon after returning home. Tennessee had gone Republican, but court rulings restoring the vote to some whites and the violence of the Ku Klux Klan suppressing the African-American vote, leading to a Democratic victory in the legislative elections in August 1869. Johnson was seen as a likely victor in the Senate election, although hated by Radical Republicans, and by some Democrats because of his wartime activities. Although he was at one point within a single vote of victory in the legislature's balloting, the Republicans eventually elected Henry Cooper over Johnson, 54–51. In 1872, there was a special election for an at-large congressional seat for Tennessee; Johnson initially sought the Democratic nomination, but when he saw that it would go to former Confederate general Benjamin F. Cheatham, decided to run as an independent. The former president was defeated, finishing third, but the split in the Democratic Party defeated Cheatham in favor of an old Johnson Unionist ally, Horace Maynard. In 1873, Johnson contracted cholera during an epidemic but recovered; that year he lost about $73,000 when the First National Bank of Washington went under, though he was eventually repaid much of the sum. Return to the Senate He began looking towards the next Senate election to take place in the legislature in early 1875. Johnson began to woo the farmers' Grange movement; with his Jeffersonian leanings, he easily gained their support. He spoke throughout the state in his final campaign tour. Few African Americans outside the large towns were now able to vote as Reconstruction faded in Tennessee, setting a pattern that would be repeated in the other Southern states; the white domination would last almost a century. In the Tennessee legislative elections in August, the Democrats elected 92 legislators to the Republicans' eight, and Johnson went to Nashville for the legislative session. When the balloting for the Senate seat began on January 20, 1875, he led with 30 votes, but did not have the required majority as three former Confederate generals, one former colonel, and a former Democratic congressman split the vote with him. Johnson's opponents tried to agree on a single candidate who might gain majority support and defeat him, but failed, and he was elected on January 26 on the 54th ballot, with a margin of a single vote. Nashville erupted in rejoicing; remarked Johnson, "Thank God for the vindication." Johnson's comeback garnered national attention, with the St. Louis Republican calling it "the most magnificent personal triumph which the history of American politics can show". At his swearing-in in the Senate on March 5, 1875, he was greeted with flowers, and sworn in alongside Hamlin (his predecessor as vice president) by incumbent Vice President Henry Wilson (who as senator had voted for Johnson's ouster). Many Republicans ignored Senator Johnson, though some, such as Ohio's John Sherman (who had voted for conviction), shook his hand. Johnson remains the only former president to serve in the Senate. He spoke only once in the short session, on March 22 lambasting President Grant for his use of federal troops in support of Louisiana's Reconstruction government. The former president asked, "How far off is military despotism?" and concluded his speech, "may God bless this people and God save the Constitution". Death Johnson returned home after the special session concluded. In late July 1875, convinced some of his opponents were defaming him in the Ohio gubernatorial race, he decided to travel there to give speeches. He began the trip on July 28, and broke the journey at his daughter Mary's farm near Elizabethton, where his daughter Martha was also staying. That evening he suffered a stroke, but refused medical treatment until the next day, when he did not improve and two doctors were sent for from Elizabethton. He seemed to respond to their ministrations, but suffered another stroke on the evening of July 30, and died early the following morning at the age of 66. President Grant had the "painful duty" of announcing the death of the only surviving past president. Northern newspapers, in their obituaries, tended to focus on Johnson's loyalty during the war, while Southern ones paid tribute to his actions as president. Johnson's funeral was held on August 3 in Greeneville. He was buried with his body wrapped in an American flag and a copy of the U.S. Constitution placed under his head, according to his wishes. The burial ground was dedicated as the Andrew Johnson National Cemetery in 1906, and with his home and tailor's shop, is part of the Andrew Johnson National Historic Site. Historical reputation and legacy According to Castel, "historians [of Johnson's presidency] have tended to concentrate to the exclusion of practically everything else upon his role in that titanic event [Reconstruction]". Through the remainder of the 19th century, there were few historical evaluations of Johnson and his presidency. Memoirs from Northerners who had dealt with him, such as former vice president Henry Wilson and Maine Senator James G. Blaine, depicted him as an obstinate boor who tried to favor the South in Reconstruction, but who was frustrated by Congress. According to historian Howard K. Beale in his journal article about the historiography of Reconstruction, "Men of the postwar decades were more concerned with justifying their own position than they were with painstaking search for truth. Thus [Alabama congressman and historian] Hilary Herbert and his corroborators presented a Southern indictment of Northern policies, and Henry Wilson's history was a brief for the North." The turn of the 20th century saw the first significant historical evaluations of Johnson. Leading the wave was Pulitzer Prize-winning historian James Ford Rhodes, who wrote of the former president: Rhodes ascribed Johnson's faults to his personal weaknesses, and blamed him for the problems of the postbellum South. Other early 20th-century historians, such as John Burgess, future president Woodrow Wilson and William Dunning, all Southerners, concurred with Rhodes, believing Johnson flawed and politically inept, but concluding that he had tried to carry out Lincoln's plans for the South in good faith. Author and journalist Jay Tolson suggests that Wilson "depict[ed Reconstruction] as a vindictive program that hurt even repentant southerners while benefiting northern opportunists, the so-called Carpetbaggers, and cynical white southerners, or Scalawags, who exploited alliances with blacks for political gain". Even as Rhodes and his school wrote, another group of historians was setting out on the full rehabilitation of Johnson, using for the first time primary sources such as his papers, provided by his daughter Martha before her death in 1901, and the diaries of Johnson's Navy Secretary, Gideon Welles, first published in 1911. The resulting volumes, such as David Miller DeWitt's The Impeachment and Trial of President Andrew Johnson (1903), presented him far more favorably than they did those who had sought to oust him. In James Schouler's 1913 History of the Reconstruction Period, the author accused Rhodes of being "quite unfair to Johnson", though agreeing that the former president had created many of his own problems through inept political moves. These works had an effect; although historians continued to view Johnson as having deep flaws which sabotaged his presidency, they saw his Reconstruction policies as fundamentally correct. Castel writes: Beale wondered in 1940, "is it not time that we studied the history of Reconstruction without first assuming, at least subconsciously, that carpetbaggers and Southern white Republicans were wicked, that Negroes were illiterate incompetents, and that the whole white South owes a debt of gratitude to the restorers of 'white supremacy'?" Despite these doubts, the favorable view of Johnson survived for a time. In 1942, Van Heflin portrayed the former president as a fighter for democracy in the Hollywood film Tennessee Johnson. In 1948, a poll of his colleagues by historian Arthur M. Schlesinger deemed Johnson among the average presidents; in 1956, one by Clinton L. Rossiter named him as one of the near-great Chief Executives. Foner notes that at the time of these surveys, "the Reconstruction era that followed the Civil War was regarded as a time of corruption and misgovernment caused by granting black men the right to vote". Earlier historians, including Beale, believed that money drove events, and had seen Reconstruction as an economic struggle. They also accepted, for the most part, that reconciliation between North and South should have been the top priority of Reconstruction. In the 1950s, historians began to focus on the African-American experience as central to Reconstruction. They rejected completely any claim of black inferiority, which had marked many earlier historical works, and saw the developing civil rights movement as a second Reconstruction; some writers stated they hoped their work on the postbellum era would advance the cause of civil rights. These authors sympathized with the Radical Republicans for their desire to help the African American, and saw Johnson as callous towards the freedman. In a number of works from 1956 onwards by such historians as Fawn Brodie, the former president was depicted as a successful saboteur of efforts to better the freedman's lot. These volumes included major biographies of Stevens and Stanton. Reconstruction was increasingly seen as a noble effort to integrate the freed slaves into society. In the early 21st century, Johnson is among those commonly mentioned as the worst presidents in U.S. history. According to historian Glenn W. Lafantasie, who believes Buchanan the worst president, "Johnson is a particular favorite for the bottom of the pile because of his impeachment ... his complete mishandling of Reconstruction policy ... his bristling personality, and his enormous sense of self-importance." Tolson suggests that "Johnson is now scorned for having resisted Radical Republican policies aimed at securing the rights and well-being of the newly emancipated African-Americans". Gordon-Reed notes that Johnson, along with his contemporaries Pierce and Buchanan, is generally listed among the five worst presidents, but states, "there have never been more difficult times in the life of this nation. The problems these men had to confront were enormous. It would have taken a succession of Lincolns to do them justice". Trefousse considers Johnson's legacy to be "the maintenance of white supremacy. His boost to Southern conservatives by undermining Reconstruction was his legacy to the nation, one that would trouble the country for generations to come". Gordon-Reed states of Johnson: See also Efforts to impeach Andrew Johnson Tennessee Johnson, a 1942 film about Andrew Johnson, depicting the events surrounding his impeachment Notes References Citations Sources vol 5 1864–66 online and vol 6 1866–72 online Primary sources Further reading Levine, Robert S. The Failed Promise: Reconstruction, Frederick Douglass, and the Impeachment of Andrew Johnson (2021) excerpt External links White House biography Andrew Johnson National Historic Site Andrew Johnson: A Resource Guide – Library of Congress Essays on Andrew Johnson and shorter essays on each member of his cabinet and First Lady, from the Miller Center of Public Affairs "Life Portrait of Andrew Johnson", from C-SPAN's American Presidents: Life Portraits, July 9, 1999 Text of a number of Johnson's speeches at the Miller Center of Public Affairs Andrew Johnson Personal Manuscripts and Letters – Shapell Manuscript Foundation Resolutions of Impeachment from the National Archives Tennessee State Library and Archives/Tennessee Virtual Archive/Andrew Johnson Collection/Andrew Johnson Bicentennial, 1808–2008 1808 births 1875 deaths 19th-century presidents of the United States 19th-century vice presidents of the United States 1860s in the United States Candidates in the 1860 United States presidential election Candidates in the 1868 United States presidential election 1864 United States vice-presidential candidates Presidents of the United States Vice presidents of the United States American people of English descent American people of Irish descent American people of Scotch-Irish descent Burials in Tennessee Democratic Party state governors of the United States Democratic Party United States senators American Freemasons Governors of Tennessee Impeached presidents of the United States Lincoln administration cabinet members Mayors of places in Tennessee Members of the Tennessee House of Representatives Members of the United States House of Representatives from Tennessee People from Greeneville, Tennessee Politicians from Raleigh, North Carolina People of the Reconstruction Era People of North Carolina in the American Civil War People of Tennessee in the American Civil War Andrew Johnson family Republican Party (United States) vice presidential nominees Southern Unionists in the American Civil War American tailors People associated with the assassination of Abraham Lincoln Tennessee city council members Tennessee Democrats Tennessee state senators Union Army generals Union political leaders United States senators from Tennessee Democratic Party members of the United States House of Representatives American slave owners People from Laurens, South Carolina Democratic Party presidents of the United States

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics

1625

https://en.wikipedia.org/wiki/Aleksandr%20Solzhenitsyn

Aleksandr Solzhenitsyn

Aleksandr Isayevich Solzhenitsyn (11 December 1918 – 3 August 2008) was a Russian novelist, philosopher, historian, short story writer, and political prisoner. One of the most famous Soviet dissidents, Solzhenitsyn was an outspoken critic of communism and helped to raise global awareness of political repression in the Soviet Union (USSR), in particular the Gulag system. Solzhenitsyn was born into a family that defied the Soviet anti-religious campaign in the 1920s and remained devout members of the Russian Orthodox Church. While still young, Solzhenitsyn lost his faith in Christianity and became a firm believer in both atheism and Marxism–Leninism; in his later life, he gradually became a philosophically minded Eastern Orthodox Christian as a result of his experience in prison and the camps. While serving as a captain in the Red Army during World War II, Solzhenitsyn was arrested by the SMERSH and sentenced to eight years in the Gulag and then internal exile for criticizing Soviet leader Joseph Stalin in a private letter. As a result of the Khrushchev Thaw, Solzhenitsyn was released and exonerated. After he had returned to the Christian faith of his childhood, he pursued writing novels about repressions in the Soviet Union and his experiences. He published his first novel, One Day in the Life of Ivan Denisovich in 1962, with approval from Soviet leader Nikita Khrushchev, which was an account of Stalinist repressions. Solzhenitsyn's last work to be published in the Soviet Union was Matryona's Place in 1963. Following the removal of Khrushchev from power, the Soviet authorities attempted to discourage him from continuing to write. Solzhenitsyn continued to work on further novels and their publication in other countries including Cancer Ward in 1968, August 1914 in 1971, and The Gulag Archipelago in 1973, the publication of which outraged the Soviet authorities. In 1974 Solzhenitsyn lost his Soviet citizenship and was flown to West Germany. In 1976, he moved with his family to the United States, where he continued to write. In 1990, shortly before the dissolution of the Soviet Union, his citizenship was restored, and four years later he returned to Russia, where he remained until his death in 2008. He was awarded the 1970 Nobel Prize in Literature "for the ethical force with which he has pursued the indispensable traditions of Russian literature", and The Gulag Archipelago was a highly influential work that "amounted to a head-on challenge to the Soviet state", and sold tens of millions of copies. Biography Early years Solzhenitsyn was born in Kislovodsk (now in Stavropol Krai, Russia). His father was of Russian descent and his mother, Taisiya Zakharovna (née Shcherbak), was of Ukrainian descent. Her father had risen from humble beginnings to become a wealthy landowner, acquiring a large estate in the Kuban region in the northern foothills of the Caucasus. During World War I, Taisiya went to Moscow to study. While there she met and married Isaakiy Semyonovich Solzhenitsyn, a young officer in the Imperial Russian Army of Cossack origin and fellow native of the Caucasus region. The family background of his parents is vividly brought to life in the opening chapters of August 1914, and in the later Red Wheel novels. In 1918, Taisiya became pregnant with Aleksandr. On 15 June, shortly after her pregnancy was confirmed, Isaakiy was killed in a hunting accident. Aleksandr was raised by his widowed mother and his aunt in lowly circumstances. His earliest years coincided with the Russian Civil War. By 1930 the family property had been turned into a collective farm. Later, Solzhenitsyn recalled that his mother had fought for survival and that they had to keep his father's background in the old Imperial Army a secret. His educated mother (who never remarried) encouraged his literary and scientific learnings and raised him in the Russian Orthodox faith; she died in 1944. As early as 1936, Solzhenitsyn began developing the characters and concepts for a planned epic work on World War I and the Russian Revolution. This eventually led to the novel August 1914; some of the chapters he wrote then still survive. Solzhenitsyn studied mathematics and physics at Rostov State University. At the same time he took correspondence courses from the Moscow Institute of Philosophy, Literature and History, by this time heavily ideological in scope. As he himself makes clear, he did not question the state ideology or the superiority of the Soviet Union until he spent time in the camps. World War II During the war, Solzhenitsyn served as the commander of a sound-ranging battery in the Red Army, was involved in major action at the front, and was twice decorated. He was awarded the Order of the Red Star on 8 July 1944 for sound-ranging two German artillery batteries and adjusting counterbattery fire onto them, resulting in their destruction. A series of writings published late in his life, including the early uncompleted novel Love the Revolution!, chronicle his wartime experience and growing doubts about the moral foundations of the Soviet regime. While serving as an artillery officer in East Prussia, Solzhenitsyn witnessed war crimes against local German civilians by Soviet military personnel. Of the atrocities, Solzhenitsyn wrote: "You know very well that we've come to Germany to take our revenge" for Nazi atrocities committed in the Soviet Union. The noncombatants and the elderly were robbed of their meager possessions and women and girls were gang-raped. A few years later, in the forced labor camp, he memorized a poem titled "Prussian Nights" about a woman raped to death in East Prussia. In this poem, which describes the gang-rape of a Polish woman whom the Red Army soldiers mistakenly thought to be a German, the first-person narrator comments on the events with sarcasm and refers to the responsibility of official Soviet writers like Ilya Ehrenburg. In The Gulag Archipelago, Solzhenitsyn wrote, "There is nothing that so assists the awakening of omniscience within us as insistent thoughts about one's own transgressions, errors, mistakes. After the difficult cycles of such ponderings over many years, whenever I mentioned the heartlessness of our highest-ranking bureaucrats, the cruelty of our executioners, I remember myself in my Captain's shoulder boards and the forward march of my battery through East Prussia, enshrouded in fire, and I say: 'So were we any better?'" Imprisonment In February 1945, while serving in East Prussia, Solzhenitsyn was arrested by SMERSH for writing derogatory comments in private letters to a friend, Nikolai Vitkevich, about the conduct of the war by Joseph Stalin, whom he called "Khozyain" ("the boss"), and "Balabos" (Yiddish rendering of Hebrew baal ha-bayit for "master of the house"). He also had talks with the same friend about the need for a new organization to replace the Soviet regime. He was accused of anti-Soviet propaganda under Article 58 paragraph 10 of the Soviet criminal code, and of "founding a hostile organization" under paragraph 11. Solzhenitsyn was taken to the Lubyanka prison in Moscow, where he was interrogated. On 9 May 1945, it was announced that Germany had surrendered and all of Moscow broke out in celebrations with fireworks and searchlights illuminating the sky to celebrate the victory in the Great Patriotic War. From his cell in the Lubyanka, Solzhenitsyn remembered: "Above the muzzle of our window, and from all the other cells of the Lubyanka, and from all the windows of the Moscow prisons, we too, former prisoners of war and former front-line soldiers, watched the Moscow heavens, patterned with fireworks and crisscrossed with beams of searchlights. There was no rejoicing in our cells and no hugs and no kisses for us. That victory was not ours." On 7 July 1945, he was sentenced in his absence by Special Council of the NKVD to an eight-year term in a labour camp. This was the normal sentence for most crimes under Article 58 at the time. The first part of Solzhenitsyn's sentence was served in several work camps; the "middle phase", as he later referred to it, was spent in a sharashka (a special scientific research facility run by Ministry of State Security), where he met Lev Kopelev, upon whom he based the character of Lev Rubin in his book The First Circle, published in a self-censored or "distorted" version in the West in 1968 (an English translation of the full version was eventually published by Harper Perennial in October 2009). In 1950, he was sent to a "Special Camp" for political prisoners. During his imprisonment at the camp in the town of Ekibastuz in Kazakhstan, he worked as a miner, bricklayer, and foundry foreman. His experiences at Ekibastuz formed the basis for the book One Day in the Life of Ivan Denisovich. One of his fellow political prisoners, Ion Moraru, remembers that Solzhenitsyn spent some of his time at Ekibastuz writing. While there Solzhenitsyn had a tumor removed. His cancer was not diagnosed at the time. In March 1953, after his sentence ended, Solzhenitsyn was sent to internal exile for life at Birlik, a village in Baidibek District of South Kazakhstan. His undiagnosed cancer spread until, by the end of the year, he was close to death. In 1954, he was permitted to be treated in a hospital in Tashkent, where his tumor went into remission. His experiences there became the basis of his novel Cancer Ward and also found an echo in the short story "The Right Hand." It was during this decade of imprisonment and exile that Solzhenitsyn developed the philosophical and religious positions of his later life, gradually becoming a philosophically minded Eastern Orthodox Christian as a result of his experience in prison and the camps. He repented for some of his actions as a Red Army captain, and in prison compared himself to the perpetrators of the Gulag. His transformation is described at some length in the fourth part of The Gulag Archipelago ("The Soul and Barbed Wire"). The narrative poem The Trail (written without benefit of pen or paper in prison and camps between 1947 and 1952) and the 28 poems composed in prison, forced-labour camp, and exile also provide crucial material for understanding Solzhenitsyn's intellectual and spiritual odyssey during this period. These "early" works, largely unknown in the West, were published for the first time in Russian in 1999 and excerpted in English in 2006. Marriages and children On 7 April 1940, while at the university, Solzhenitsyn married Natalia Alekseevna Reshetovskaya. They had just over a year of married life before he went into the army, then to the Gulag. They divorced in 1952, a year before his release, because wives of Gulag prisoners faced loss of work or residence permits. After the end of his internal exile, they remarried in 1957, divorcing a second time in 1972. Reshetovskaya wrote negatively of Solzhenitsyn in her memoirs, accusing him of having affairs, and said of the relationship that "[Solzhenitsyn]'s despotism ... would crush my independence and would not permit my personality to develop." In 1973, Solzhenitsyn married his second wife, Natalia Dmitrievna Svetlova, a mathematician who had a son, Dmitri Turin, from a brief prior marriage. He and Svetlova (born 1939) had three sons: Yermolai (1970), Ignat (1972), and Stepan (1973). Dmitri Turin died on 18 March 1994, aged 32, at his home in New York City. After prison After Khrushchev's Secret Speech in 1956, Solzhenitsyn was freed from exile and exonerated. Following his return from exile, Solzhenitsyn was, while teaching at a secondary school during the day, spending his nights secretly engaged in writing. In his Nobel Prize acceptance speech he wrote that "during all the years until 1961, not only was I convinced I should never see a single line of mine in print in my lifetime, but, also, I scarcely dared allow any of my close acquaintances to read anything I had written because I feared this would become known." In 1960, aged 42, he approached Aleksandr Tvardovsky, a poet and the chief editor of the Novy Mir magazine, with the manuscript of One Day in the Life of Ivan Denisovich. It was published in edited form in 1962, with the explicit approval of Nikita Khrushchev, who defended it at the presidium of the Politburo hearing on whether to allow its publication, and added: "There's a Stalinist in each of you; there's even a Stalinist in me. We must root out this evil." The book quickly sold out and became an instant hit. In the 1960s, while he was publicly known to be writing Cancer Ward, he was simultaneously writing The Gulag Archipelago. During Khrushchev's tenure, One Day in the Life of Ivan Denisovich was studied in schools in the Soviet Union, as were three more short works of Solzhenitsyn's, including his short story "Matryona's Home", published in 1963. These would be the last of his works published in the Soviet Union until 1990. One Day in the Life of Ivan Denisovich brought the Soviet system of prison labour to the attention of the West. It caused as much of a sensation in the Soviet Union as it did in the West—not only by its striking realism and candor, but also because it was the first major piece of Soviet literature since the 1920s on a politically charged theme, written by a non-party member, indeed a man who had been to Siberia for "libelous speech" about the leaders, and yet its publication had been officially permitted. In this sense, the publication of Solzhenitsyn's story was an almost unheard of instance of free, unrestrained discussion of politics through literature. However, after Khrushchev had been ousted from power in 1964, the time for such raw exposing works came to an end. Later years in the Soviet Union Solzhenitsyn made an unsuccessful attempt, with the help of Tvardovsky, to have his novel Cancer Ward legally published in the Soviet Union. This required the approval of the Union of Writers. Though some there appreciated it, the work was ultimately denied publication unless it was to be revised and cleaned of suspect statements and anti-Soviet insinuations. After Khrushchev's removal in 1964, the cultural climate again became more repressive. Publishing of Solzhenitsyn's work quickly stopped; as a writer, he became a non-person, and, by 1965, the KGB had seized some of his papers, including the manuscript of The First Circle. Meanwhile, Solzhenitsyn continued to secretly and feverishly work on the most well-known of his writings, The Gulag Archipelago. The seizing of his novel manuscript first made him desperate and frightened, but gradually he realized that it had set him free from the pretenses and trappings of being an "officially acclaimed" writer, a status which had become familiar but which was becoming increasingly irrelevant. After the KGB had confiscated Solzhenitsyn's materials in Moscow, during 1965–67, the preparatory drafts of The Gulag Archipelago were turned into finished typescript in hiding at his friends' homes in Soviet Estonia. Solzhenitsyn had befriended Arnold Susi, a lawyer and former Minister of Education of Estonia in a Lubyanka Building prison cell. After completion, Solzhenitsyn's original handwritten script was kept hidden from the KGB in Estonia by Arnold Susi's daughter Heli Susi until the collapse of the Soviet Union. In 1969, Solzhenitsyn was expelled from the Union of Writers. In 1970, he was awarded the Nobel Prize in Literature. He could not receive the prize personally in Stockholm at that time, since he was afraid he would not be let back into the Soviet Union. Instead, it was suggested he should receive the prize in a special ceremony at the Swedish embassy in Moscow. The Swedish government refused to accept this solution because such a ceremony and the ensuing media coverage might upset the Soviet Union and damage Swedish-Soviet relations. Instead, Solzhenitsyn received his prize at the 1974 ceremony after he had been expelled from the Soviet Union. The Gulag Archipelago was composed from 1958 to 1967, and has sold over thirty million copies in thirty-five languages. It was a three-volume, seven-part work on the Soviet prison camp system, which drew from Solzhenitsyn's experiences and the testimony of 256 former prisoners and Solzhenitsyn's own research into the history of the Russian penal system. It discusses the system's origins from the founding of the Communist regime, with Vladimir Lenin having responsibility, detailing interrogation procedures, prisoner transports, prison camp culture, prisoner uprisings and revolts such as the Kengir uprising, and the practice of internal exile. Soviet and Communist studies historian and archival researcher Stephen G. Wheatcroft wrote that the book was essentially a "literary and political work", and "never claimed to place the camps in a historical or social-scientific quantitative perspective" but that in the case of qualitative estimates, Solzhenitsyn gave his high estimate as he wanted to challenge the Soviet authorities to show that "the scale of the camps was less than this." Historian J. Arch Getty wrote of Solzhenitsyn's methodology that "such documentation is methodically unacceptable in other fields of history", which gives priority to vague hearsay and leads towards selective bias. According to journalist Anne Applebaum, who has made extensive research on the Gulag, The Gulag Archipelago'''s rich and varied authorial voice, its unique weaving together of personal testimony, philosophical analysis, and historical investigation, and its unrelenting indictment of Communist ideology made it one of the most influential books of the 20th century. On 8 August 1971, the KGB allegedly attempted to assassinate Solzhenitsyn using an unknown chemical agent (most likely ricin) with an experimental gel-based delivery method. The attempt left him seriously ill but he survived. Although The Gulag Archipelago was not published in the Soviet Union, it was extensively criticized by the Party-controlled Soviet press. An editorial in Pravda on 14 January 1974 accused Solzhenitsyn of supporting "Hitlerites" and making "excuses for the crimes of the Vlasovites and Bandera gangs." According to the editorial, Solzhenitsyn was "choking with pathological hatred for the country where he was born and grew up, for the socialist system, and for Soviet people." During this period, he was sheltered by the cellist Mstislav Rostropovich, who suffered considerably for his support of Solzhenitsyn and was eventually forced into exile himself. Expulsion from the Soviet Union In a discussion of its options in dealing with Solzhenitsyn the members of the Politburo considered his arrest and imprisonment and his expulsion to a capitalist country willing to take him. Guided by KGB chief Yury Andropov, and following a statement from West German Chancellor Willy Brandt that Solzhenitsyn could live and work freely in West Germany, it was decided to deport the writer directly to that country. In the West On 12 February 1974, Solzhenitsyn was arrested and deported the next day from the Soviet Union to Frankfurt, West Germany and stripped of his Soviet citizenship. The KGB had found the manuscript for the first part of The Gulag Archipelago. U.S. military attaché William Odom managed to smuggle out a large portion of Solzhenitsyn's archive, including the author's membership card for the Writers' Union and his Second World War military citations. Solzhenitsyn paid tribute to Odom's role in his memoir Invisible Allies (1995). In West Germany, Solzhenitsyn lived in Heinrich Böll's house in . He then moved to Zürich, Switzerland before Stanford University invited him to stay in the United States to "facilitate your work, and to accommodate you and your family". He stayed at the Hoover Tower, part of the Hoover Institution, before moving to Cavendish, Vermont, in 1976. He was given an honorary literary degree from Harvard University in 1978 and on 8 June 1978 he gave a commencement address, condemning, among other things, the press, the lack of spirituality and traditional values, and the anthropocentrism of Western culture. On 19 September 1974, Yuri Andropov approved a large-scale operation to discredit Solzhenitsyn and his family and cut his communications with Soviet dissidents. The plan was jointly approved by Vladimir Kryuchkov, Philipp Bobkov, and Grigorenko (heads of First, Second and Fifth KGB Directorates). The residencies in Geneva, London, Paris, Rome and other European cities participated in the operation. Among other active measures, at least three StB agents became translators and secretaries of Solzhenitsyn (one of them translated the poem Prussian Nights), keeping the KGB informed regarding all contacts by Solzhenitsyn. The KGB also sponsored a series of hostile books about Solzhenitsyn, most notably a "memoir published under the name of his first wife, Natalia Reshetovskaya, but probably mostly composed by Service", according to historian Christopher Andrew. Andropov also gave an order to create "an atmosphere of distrust and suspicion between Pauk and the people around him" by feeding him rumors that the people around him were KGB agents, and deceiving him at every opportunity. Among other things, he continually received envelopes with photographs of car crashes, brain surgery and other disturbing imagery. After the KGB harassment in Zürich, Solzhenitsyn settled in Cavendish, Vermont, reduced communications with others. His influence and moral authority for the West diminished as he became increasingly isolated and critical of Western individualism. KGB and CPSU experts finally concluded that he alienated American listeners by his "reactionary views and intransigent criticism of the US way of life", so no further active measures would be required. Over the next 17 years, Solzhenitsyn worked on his dramatized history of the Russian Revolution of 1917, The Red Wheel. By 1992, four sections had been completed and he had also written several shorter works. Despite spending almost two decades in the United States, Solzhenitsyn did not become fluent in spoken English. He had, however, been reading English-language literature since his teens, encouraged by his mother. More importantly, he resented the idea of becoming a media star and of tempering his ideas or ways of talking in order to suit television. Solzhenitsyn's warnings about the dangers of Communist aggression and the weakening of the moral fiber of the West were generally well received in Western conservative circles (e.g. Ford administration staffers Dick Cheney and Donald Rumsfeld advocated on Solzhenitsyn's behalf for him to speak directly to President Gerald Ford about the Soviet threat), prior to and alongside the tougher foreign policy pursued by US President Ronald Reagan. At the same time, liberals and secularists became increasingly critical of what they perceived as his reactionary preference for Russian nationalism and the Russian Orthodox religion. Solzhenitsyn also harshly criticised what he saw as the ugliness and spiritual vapidity of the dominant pop culture of the modern West, including television and much of popular music: "...the human soul longs for things higher, warmer, and purer than those offered by today's mass living habits... by TV stupor and by intolerable music." Despite his criticism of the "weakness" of the West, Solzhenitsyn always made clear that he admired the political liberty which was one of the enduring strengths of Western democratic societies. In a major speech delivered to the International Academy of Philosophy in Liechtenstein on 14 September 1993, Solzhenitsyn implored the West not to "lose sight of its own values, its historically unique stability of civic life under the rule of law—a hard-won stability which grants independence and space to every private citizen." In a series of writings, speeches, and interviews after his return to his native Russia in 1994, Solzhenitsyn spoke about his admiration for the local self-government he had witnessed first hand in Switzerland and New England."The Cavendish Farewell" in Ericson (2009) pp. 606–07 He "praised 'the sensible and sure process of grassroots democracy, in which the local population solves most of its problems on its own, not waiting for the decisions of higher authorities.'" Solzhenitsyn's patriotism was inward-looking. He called for Russia to "renounce all mad fantasies of foreign conquest and begin the peaceful long, long long period of recuperation," as he put it in a 1979 BBC interview with Latvian-born BBC journalist Janis Sapiets. Return to Russia In 1990, his Soviet citizenship was restored, and, in 1994, he returned to Russia with his wife, Natalia, who had become a United States citizen. Their sons stayed behind in the United States (later, his eldest son Yermolai returned to Russia). From then until his death, he lived with his wife in a dacha in Troitse-Lykovo in west Moscow between the dachas once occupied by Soviet leaders Mikhail Suslov and Konstantin Chernenko. A staunch believer in traditional Russian culture, Solzhenitsyn expressed his disillusionment with post-Soviet Russia in works such as Rebuilding Russia, and called for the establishment of a strong presidential republic balanced by vigorous institutions of local self-government. The latter would remain his major political theme. Solzhenitsyn also published eight two-part short stories, a series of contemplative "miniatures" or prose poems, and a literary memoir on his years in the West The Grain Between the Millstones, translated and released as two works by the University of Notre Dame as part of the Kennan Institute's Solzhenitsyn Initiative. The first, Between Two Millstones, Book 1: Sketches of Exile (1974–1978), was translated by Peter Constantine and published in October 2018, the second, Book 2: Exile in America (1978–1994) translated by Clare Kitson and Melanie Moore and published in October 2020. Once back in Russia Solzhenitsyn hosted a television talk show program. Its eventual format was Solzhenitsyn delivering a 15-minute monologue twice a month; it was discontinued in 1995. Solzhenitsyn became a supporter of Vladimir Putin, who said he shared Solzhenitsyn's critical view towards the Russian Revolution. All of Solzhenitsyn's sons became U.S. citizens. One, Ignat, is a pianist and conductor. Another Solzhenitsyn son, Yermolai, works for the Moscow office of McKinsey & Company, a management consultancy firm, where he is a senior partner. Death Solzhenitsyn died of heart failure near Moscow on 3 August 2008, at the age of 89. A burial service was held at Donskoy Monastery, Moscow, on 6 August 2008. He was buried the same day in the monastery, in a spot he had chosen. Russian and world leaders paid tribute to Solzhenitsyn following his death. Views on history and politics On Christianity, Tsarism, and Russian nationalism According to William Harrison, Solzhenitsyn was an "arch-reactionary", who argued that the Soviet State "suppressed" traditional Russian and Ukrainian culture, called for the creation of a united Slavic state encompassing Russia, Ukraine, and Belarus, and who was a fierce opponent of Ukrainian independence. Harrison also alleged that Solzhenitsyn held Pan-Slavist and monarchist views. According to Harrison, "His historical writing is imbued with a hankering after an idealized Tsarist era when, seemingly, everything was rosy. He sought refuge in a dreamy past, where, he believed, a united Slavic state (the Russian empire) built on Orthodox foundations had provided an ideological alternative to western individualistic liberalism." In his writings and speeches, Solzhenitsyn, however, has sharply criticized the policies of every Tsar from the House of Romanov. A persistent theme in his criticism has been that the Romanovs preferred, like Nicholas I during the Hungarian Revolution of 1848, to intervene in the internal affairs of foreign countries while governing badly at home. Solzhenitsyn has also repeatedly denounced Tsar Alexis of Russia and Patriarch Nikon of Moscow for causing the Great Schism of 1666, which Solzhenitsyn says both divided and weakened the Russian Orthodox Church at a time when unity was desperately needed. Solzhenitsyn also attacked both the Tsar and the Patriarch for using excommunication, Siberian exile, imprisonment, torture, and even burning at the stake against the Old Believers, who rejected the liturgical changes which caused the Schism. Solzhenitsyn has also argued that the Dechristianization of Russian culture, which he considers most responsible for the Bolshevik Revolution, began in 1666, became much worse during the Reign of Tsar Peter the Great, and accelerated into an epidemic during The Enlightenment, the Romantic era, and the Silver Age. Expanding upon this theme, Solzhenitsyn once declared, "Over a half century ago, while I was still a child, I recall hearing a number of old people offer the following explanation for the great disasters that had befallen Russia: 'Men have forgotten God; that's why all this has happened. Since then I have spent well-nigh 50 years working on the history of our revolution; in the process I have read hundreds of books, collected hundreds of personal testimonies, and have already contributed eight volumes of my own toward the effort of clearing away the rubble left by that upheaval. But if I were asked today to formulate as concisely as possible the main cause of the ruinous revolution that swallowed up some 60 million of our people, I could not put it more accurately than to repeat: 'Men have forgotten God; that's why all this has happened.'" In an interview with Joseph Pearce, however, Solzhenitsyn commented, "[The Old Believers were] treated amazingly unjustly, because some very insignificant, trifling differences in ritual which were promoted with poor judgment and without much sound basis. Because of these small differences, they were persecuted in very many cruel ways, they were suppressed, they were exiled. From the perspective of historical justice, I sympathise with them and I am on their side, but this in no way ties in with what I have just said about the fact that religion in order to keep up with mankind must adapt its forms toward modern culture. In other words, do I agree with the Old Believers that religion should freeze and not move at all? Not at all!" When asked by Pearce for his opinions about the division within the Roman Catholic Church over the Second Vatican Council and the Mass of Paul VI, Solzhenitsyn replied, "A question peculiar to the Russian Orthodox Church is, should we continue to use Old Church Slavonic, or should we start to introduce more of the contemporary Russian language into the service? I understand the fears of both those in the Orthodox and in the Catholic Church, the wariness, the hesitation, and the fear that this is lowering the Church to the modern condition, the modern surroundings. I understand this, but alas, I fear that if religion does not allow itself to change, it will be impossible to return the world to religion because the world is incapable on its own of rising as high as the old demands of religion. Religion needs to come and meet it somewhat." Surprised to hear Solzhenitsyn, "so often perceived as an arch-traditionalist, apparently coming down on the side of the reformers", Pearce then asked Solzhenitsyn what he thought of the division caused within the Anglican Communion by the decision to ordain female priests. Solzhenitsyn replied, "Certainly there are many firm boundaries that should not be changed. When I speak of some sort of correlation between the cultural norms of the present, it is really only a small part of the whole thing." Solzhenitsyn then added, "Certainly, I do not believe that women priests is the way to go!" On Russia and the Jews OGPU officer Naftaly Frenkel, whom Solzhenitsyn identified as "a Turkish Jew born in Constantinople", is represented as having played a major role in the organisation of work in the Gulag. Solzhenitsyn claimed that Frenkel was the "nerve of the Archipelago". In his 1974 essay "Repentance and Self-Limitation in the Life of Nations", Solzhenitsyn urged "Russian Gentiles" and Jews alike to take moral responsibility for the "renegades" from both communities who enthusiastically embraced atheism and Marxism–Leninism and participated in the Red Terror and many other acts of torture and mass murder following the October Revolution. Solzhenitsyn argued that both Russian Gentiles and Jews should be prepared to treat the atrocities committed by Jewish and Gentile Bolsheviks as though they were the acts of their own family members, before their consciences and before God. Solzhenitsyn said that if we deny all responsibility for the crimes of our national kin, "the very concept of a people loses all meaning." In a review of Solzhenitsyn's novel August 1914 in The New York Times on 13 November 1985, Jewish American historian Richard Pipes wrote: "Every culture has its own brand of anti-Semitism. In Solzhenitsyn's case, it's not racial. It has nothing to do with blood. He's certainly not a racist; the question is fundamentally religious and cultural. He bears some resemblance to Fyodor Dostoyevsky, who was a fervent Christian and patriot and a rabid anti-Semite. Solzhenitsyn is unquestionably in the grip of the Russian extreme right's view of the Revolution, which is that it was the doing of the Jews". Award-winning Jewish novelist and the Holocaust survivor Elie Wiesel disagreed and wrote that Solzhenitsyn was "too intelligent, too honest, too courageous, too great a writer" to be an anti-Semite. In his 1998 book Russia in Collapse, Solzhenitsyn criticized the Russian far-right's obsession with anti-Semitic and anti-Masonic conspiracy theories. In 2001, Solzhenitsyn published a two-volume work on the history of Russian-Jewish relations (Two Hundred Years Together 2001, 2002). The book triggered renewed accusations of anti-Semitism. In the book, he repeated his call for Russian Gentiles and Jews to share responsibility for everything that happened in the Soviet Union. He also downplayed the number of victims of an 1882 pogrom despite current evidence, and failed to mention the infamous Beilis affair, a 1911 trial in Kiev where a Jew was accused of ritually murdering Christian children. He was also criticized for relying on outdated scholarship, ignoring current western scholarship, and for selectively quoting to strengthen his preconceptions, such as that the Jews were often treated better than non-Jewish Russians during the Soviet Union. Similarities between Two Hundred Years Together and an anti-Semitic essay titled "Jews in the USSR and in the Future Russia", attributed to Solzhenitsyn, have led to the inference that he stands behind the anti-Semitic passages. Solzhenitsyn himself explained that the essay consists of manuscripts stolen from him by the KGB, and then carefully edited to appear anti-Semitic, before being published, forty years before, without his consent.Cathy Young: Reply to Daniel J. Mahoney in Reason Magazine, August–September 2004. According to the historian Semyon Reznik, textological analyses have proven Solzhenitsyn's authorship. Criticism of communism Solzhenitsyn emphasized the significantly more oppressive character of the Soviet police state, in comparison to the Russian Empire of the House of Romanov. He asserted that Imperial Russia did not censor literature or the media to the extreme style of the Soviet Glavlit, that political prisoners typically were not forced into labor camps, and that the number of political prisoners and exiles was only one ten-thousandth of the numbers of prisoners and Exiles following the Bolshevik Revolution. He noted that the Tsar's secret police, the Okhrana, was only present in the three largest cities, and not at all in the Imperial Russian Army. Shortly before his return to Russia, Solzhenitsyn delivered a speech in Les Lucs-sur-Boulogne to commemorate the 200th anniversary of the Vendée Uprising. During his speech, Solzhenitsyn compared Lenin's Bolsheviks with the Jacobin Club during the French Revolution. He also compared the Vendean rebels with the Russian, Ukrainian, and Cossack peasants who rebelled against the Bolsheviks, saying that both were destroyed mercilessly by revolutionary despotism. He commented that, while the French Reign of Terror ended with the Thermidorian reaction and the toppling of the Jacobins and the execution of Maximilien Robespierre, its Soviet equivalent continued to accelerate until the Khrushchev thaw of the 1950s. According to Solzhenitsyn, Russians were not the ruling nation in the Soviet Union. He believed that all the traditional culture of all ethnic groups were equally oppressed in favor of atheism and Marxist–Leninism. Russian culture was even more repressed than any other culture in the Soviet Union, since the regime was more afraid of ethnic uprisings among Russian Christians than among any other ethnicity. Therefore, Solzhenitsyn argued, Russian nationalism and the Russian Orthodox Church should not be regarded as a threat by the West but rather as allies. Solzhenitsyn made a speaking tour after Francisco Franco's death, and "told liberals not to push too hard for changes because Spain had more freedoms now than the Soviet Union had ever known." As reported by The New York Times, he "blamed Communism for the death of 110 million Russians and derided those in Spain who complained of dictatorship." Solzhenitsyn recalled: "I had to explain to the people of Spain in the most concise possible terms what it meant to have been subjugated by an ideology as we in the Soviet Union had been, and give the Spanish to understand what a terrible fate they escaped in 1939", a reference to the Spanish Civil War between the Nationalists and the Republicans, which was not a common view at that time among American diplomats. For Winston Lord, a protégé of the then United States Secretary of State Henry Kissinger, Solzhenitsyn was "just about a fascist." According to Elisa Kriza, Solzhenitsyn held "benevolent views" on Franco's dictatorship and Francoist Spain because it was a Christian one, and his Christian worldview operated ideologically. In The Little Grain Managed to Land Between Two Millstones, Franco's Spain is "held up as a model of a proper Christian response to the evil of Bolshevism." According to Peter Brooke, Solzhenitsyn approached the position argued by Christian Dmitri Panin, with whom he had a fell out in exile, namely that evil "must be confronted by force, and the centralised, spiritually independent Roman Catholic Church is better placed to do it than Orthodoxy with its otherworldliness and tradition of subservience to the state." In "Rebuilding Russia", an essay first published in 1990 in Komsomolskaya Pravda, Solzhenitsyn urged the Soviet Union to grant independence to all the non-Slav republics, which he claimed were sapping the Russian nation and he called for the creation of a new Slavic state bringing together Russia, Ukraine, Belarus, and parts of Kazakhstan that he considered to be Russified. On post-Soviet Russia In some of his later political writings, such as Rebuilding Russia (1990) and Russia in Collapse (1998), Solzhenitsyn criticized the oligarchic excesses of the new Russian democracy, while opposing any nostalgia for Soviet Communism. He defended moderate and self-critical patriotism (as opposed to extreme nationalism). He also urged for local self-government similar to what he had seen in New England town meetings and in the cantons of Switzerland. He also expressed concern for the fate of the 25 million ethnic Russians in the "near abroad" of the former Soviet Union. In an interview with Joseph Pearce, Solzhenitsyn was asked whether he felt that the socioeconomic theories of E.F. Schumacher were, "the key to society rediscovering its sanity". He replied, "I do believe that it would be the key, but I don't think this will happen, because people succumb to fashion, and they suffer from inertia and it is hard to them to come round to a different point of view." Solzhenitsyn refused to accept Russia's highest honor, the Order of St. Andrew, in 1998. Solzhenitsyn later said: "In 1998, it was the country's low point, with people in misery; ... Yeltsin decreed I be honored the highest state order. I replied that I was unable to receive an award from a government that had led Russia into such dire straits." In a 2003 interview with Joseph Pearce, Solzhenitsyn said: "We are exiting from communism in a most unfortunate and awkward way. It would have been difficult to design a path out of communism worse than the one that has been followed." In a 2007 interview with Der Spiegel, Solzhenitsyn expressed disappointment that the "conflation of 'Soviet' and 'Russian'", against which he spoke so often in the 1970s, had not passed away in the West, in the ex-socialist countries, or in the former Soviet republics. He commented, "The elder political generation in communist countries is not ready for repentance, while the new generation is only too happy to voice grievances and level accusations, with present-day Moscow [as] a convenient target. They behave as if they heroically liberated themselves and lead a new life now, while Moscow has remained communist. Nevertheless, I dare [to] hope that this unhealthy phase will soon be over, that all the peoples who have lived through communism will understand that communism is to blame for the bitter pages of their history." On 20 September 2000, Solzhenitsyn met newly elected Russian President Vladimir Putin. In 2008, Solzhenitsyn praised Putin, saying Russia was rediscovering what it meant to be Russian. Solzhenitsyn also praised the Russian president Dmitry Medvedev as a "nice young man" who was capable of taking on the challenges Russia was facing. Criticism of the West Once in the United States, Solzhenitsyn sharply criticized the West. Solzhenitsyn criticized the Allies for not opening a new front against Nazi Germany in the west earlier in World War II. This resulted in Soviet domination and control of the nations of Eastern Europe. Solzhenitsyn claimed the Western democracies apparently cared little about how many died in the East, as long as they could end the war quickly and painlessly for themselves in the West. Delivering the commencement address at Harvard University in 1978, he called the United States "Dechristianized" and mired in boorish consumerism. The American people, he said, speaking in Russian through a translator, were also suffering from a "decline in courage" and a "lack of manliness." Few were willing to die for their ideals, he said. He also condemned the 1960s counterculture for forcing the United States federal government to accept a "hasty" capitulation in the Vietnam War. In a reference to the Communist governments in Southeast Asia's use of re-education camps, politicide, human rights abuses, and genocide following the Fall of Saigon, Solzhenitsyn said: "But members of the U.S. antiwar movement wound up being involved in the betrayal of Far Eastern nations, in a genocide and in the suffering today imposed on 30 million people there. Do those convinced pacifists hear the moans coming from there?" He also accused the Western news media of left-wing bias, of violating the privacy of celebrities, and of filling up the "immortal souls" of their readers with celebrity gossip and other "vain talk". He also said that the West erred in thinking that the whole world should embrace this as model. While faulting Soviet society for rejecting basic human rights and the rule of law, he also critiqued the West for being too legalistic: "A society which is based on the letter of the law and never reaches any higher is taking very scarce advantage of the high level of human possibilities." Solzhenitsyn also argued that the West erred in "denying [Russian culture's] autonomous character and therefore never understood it". Solzhenitsyn criticized the 2003 invasion of Iraq and accused the United States of the "occupation" of Kosovo, Afghanistan and Iraq. Solzhenitsyn was critical of NATO's eastward expansion towards Russia's borders. In 2006, Solzhenitsyn accused NATO of trying to bring Russia under its control; he claimed this was visible because of its "ideological support for the 'colour revolutions' and the paradoxical forcing of North Atlantic interests on Central Asia". In a 2006 interview with Der Spiegel he stated "This was especially painful in the case of Ukraine, a country whose closeness to Russia is defined by literally millions of family ties among our peoples, relatives living on different sides of the national border. At one fell stroke, these families could be torn apart by a new dividing line, the border of a military bloc." On the Holodomor Solzhenitsyn gave a speech to AFL–CIO in Washington, D.C., on 30 June 1975 in which he mentioned how the system created by the Bolsheviks in 1917 caused dozens of problems in the Soviet Union. He described how this system was responsible for the Holodomor: "It was a system which, in time of peace, artificially created a famine, causing 6 million people to die in the Ukraine in 1932 and 1933." Solzhenitsyn added, "they died on the very edge of Europe. And Europe didn't even notice it. The world didn't even notice it—6 million people!" Shortly before his death, Solzhenitsyn opined in an interview published 2 April 2008 in Izvestia that, while the famine in Ukraine was both artificial and caused by the state, it was no different than the Russian famine of 1921. Solzhenitsyn expressed the belief that both famines were caused by systematic armed robbery of the harvests from both Russian and Ukrainian peasants by Bolshevik units, which were under orders from the Politburo to bring back food for the starving urban population centers while refusing for ideological reasons to permit any private sale of food supplies in the cities or to give any payment to the peasants in return for the food that was seized. Solzhenitsyn further alleged that the theory that the Holodomor was a genocide which only victimized the Ukrainian people was created decades later by believers in an anti-Russian form of extreme Ukrainian nationalism. Solzhenitsyn also cautioned that the ultranationalists' claims risked being accepted without question in the West due to widespread ignorance and misunderstanding there of both Russian and Ukrainian history. Legacy The Aleksandr Solzhenitsyn Center in Worcester, Massachusetts promotes the author and hosts the official English-language website dedicated to him. In popular media Solzhenitsyn is the subject of the song "Mother Russia" by British progressive rock group Renaissance. Solzhenitsyn's philosophy plays a key role in the 2012 film Cloud Atlas, where a character previously kept ignorant and subservient is illegally educated, and is shown reading and quoting his works. In a 2001 episode of the NBC drama The West Wing titled "Somebody's Going to Emergency, Somebody's Going to Jail, Toby Ziegler sarcastically refers to the leader of a WTO protest as Solzhenitsyn. Television documentaries on Solzhenitsyn In October 1983, French literary journalist Bernard Pivot made an hour-long television interview with Solzhenitsyn at his rural home in Vermont, US. Solzhenitsyn discussed his writing, the evolution of his language and style, his family and his outlook on the future—and stated his wish to return to Russia in his lifetime, not just to see his books eventually printed there.Apostrophes: Alexandre Soljenitsyne répond à Bernard Pivot | Archive INA Ina Talk Shows Earlier the same year, Solzhenitsyn was interviewed on separate occasions by two British journalists, Bernard Levin and Malcolm Muggeridge. In 1998, Russian filmmaker Alexander Sokurov made a four-part television documentary, Besedy s Solzhenitsynym (The Dialogues with Solzhenitsyn). The documentary was shot in Solzhenitsyn's home depicting his everyday life and his reflections on Russian history and literature. In December 2009, the Russian channel Rossiya K broadcast the French television documentary L'Histoire Secrète de l'Archipel du Goulag (The Secret History of the Gulag Archipelago) made by Jean Crépu and Nicolas Miletitch and translated into Russian under the title Taynaya Istoriya "Arkhipelaga Gulag" (Тайная история "Архипелага ГУЛАГ"). The documentary covers events related to creation and publication of The Gulag Archipelago. Published works and speeches Also known as The Prisoner and the Camp Hooker or The Tenderfoot and the Tart. The beginning of a history of the birth of the USSR. Centers on the disastrous loss in the Battle of Tannenberg in August 1914, and the ineptitude of the military leadership. Other works, similarly titled, follow the story: see The Red Wheel (overall title). (3 vols.), not a memoir, but a history of the entire process of developing and administering a police state in the Soviet Union. . . ; separate publication of chapters on Vladimir Lenin, none of them published before this point, from The Red Wheel. The first of them was later incorporated into the 1984 edition of the expanded August 1914 (though it had been written at the same time as the original version of the novel) and the rest in November 1916 and March 1917. on Russian-Jewish relations since 1772, aroused ambiguous public response. See also More literature covering the Gulag system Ivan Bunin Czesław Miłosz Đoàn Văn Toại Lev Kopelev List of refugees Wei Jingsheng Yevgeny Zamyatin Notes References Sources Kriza, Elisa (2014) Alexander Solzhenitsyn: Cold War Icon, Gulag Author, Russian Nationalist? A Study of the Western Reception of his Literary Writings, Historical Interpretations, and Political Ideas. Stuttgart: Ibidem Press. Further reading Biographies Ostrovsky Alexander (2004). Солженицын: прощание с мифом (Solzhenitsyn: Farewell to the myth) – Moscow: «Yauza», Presscom. Reference works . ; Prof. Vittorio Strada, Dott. Julija Dobrovol'skaja. Anatoly Livry, « Soljénitsyne et la République régicide », Les Lettres et Les Arts, Cahiers suisses de critique littéraire et artistiques, Association de la revue Les Lettres et les Arts, Suisse, Vicques, 2011, pp. 70–72. http://anatoly-livry.e-monsite.com/medias/files/soljenitsine-livry-1.pdf . . . . . . . . External links The Nobel Prize in Literature 1970 Negative Analysis of Alexander Solzhenitsyn by the Stalin Society'' . Vermont Recluse Aleksandr Solzhenitsyn Der Spiegel interviews Alexander Solzhenitsyn: 'I Am Not Afraid of Death', 23 July 2007 As delivered text and video of Harvard Commencement Address at AmericanRhetoric.com The Solzhenitsyn Reader: New and Essential Writings, 1947–2005 1918 births 2008 deaths 20th-century historians 20th-century male writers 20th-century non-fiction writers 20th-century Russian short story writers Burials at Donskoy Monastery Censorship in the Soviet Union Christian novelists Christian writers Converts to Eastern Orthodoxy from atheism or agnosticism Critics of atheism Critics of Marxism Eastern Orthodox philosophers Full Members of the Russian Academy of Sciences Gulag detainees Inmates of Lefortovo Prison Members of the Serbian Academy of Sciences and Arts Nobel laureates in Literature People forcibly stripped of Soviet citizenship People from Cavendish, Vermont People from Kislovodsk People of the Cold War Prison writings Recipients of the Order of the Red Star Rostov State University alumni Russian anti-communists Russian exiles Russian historians Russian humanitarians Russian male novelists Russian male short story writers Russian monarchists Russian nationalists Russian Nobel laureates Russian Orthodox Christians from Russia Russian Orthodox Christians from the Soviet Union Russian people of Ukrainian descent Russian prisoners and detainees Russian writers of Ukrainian descent Sharashka inmates Soviet Army officers Soviet dissidents Soviet emigrants to Germany Soviet emigrants to Switzerland Soviet emigrants to the United States Soviet expellees Soviet male writers Soviet military personnel of World War II Soviet Nobel laureates Soviet non-fiction writers Soviet novelists Soviet prisoners and detainees Soviet psychiatric abuse whistleblowers Soviet rehabilitations Soviet short story writers Soviet whistleblowers Stalinism-era scholars and writers State Prize of the Russian Federation laureates Stateless people Television talk show hosts Templeton Prize laureates World War II poets Male non-fiction writers

mathematics, physics, machine learning, artificial intelligence, computer software, cybersecurity, computer systems, computer science

mathematics