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Every radioactive element or isotope has a half-life. This is how long it takes half of any sample of atoms of that type to decay into a different isotope or element. Creation of atoms Nearly all the hydrogen atoms in the Universe, most of the helium atoms, and some of the lithium atoms were made soon after the Big Bang. Even today, about 90% of all atoms in the Universe are hydrogen.

All other atoms come from nuclear fusion in stars, or sometimes from cosmic rays that hit atoms. At the start of their life, all stars fuse hydrogen to make helium. The least massive stars, red dwarfs, are expected to stop there. All other stars will then fuse helium to make carbon and oxygen. In stars like the Sun, the temperature and pressure are too low to make larger atoms. But more massive stars continue fusion, until they create iron (atomic number 26) or nickel (atomic number 28). Atoms can also grow larger when neutrons or protons hit them. This could happen inside stars or in supernovae. Most atoms on Earth were made by a star that existed before the Sun. People make very large atoms by smashing together smaller atoms in particle accelerators. However, these atoms often decay very quickly. Oganesson (element 118) has a half-life of 0.00089 seconds. Even larger atoms may be created in the future.

Related pages Atomic physics, for more detail about the physics of atoms Atomic theory, for more detail about the history Exotic atom, an atom with different parts instead of protons, neutrons, and electrons Quantum mechanics, the study of small particles and how they interact with energy States of matter, the different forms in which atoms or molecules can be found Sources References Bibliography Other websites Atom (science) -Citizendium General information on atomic structure Chemistry Nuclear physics

Astronomy is the scientific study of celestial bodies. That means stars, galaxies, planets, moons, asteroids, comets and nebulae are studied, as are supernovae explosions, gamma ray bursts, and cosmic microwave background radiation. Astronomy concerns the development, physics, chemistry, meteorology and movement of celestial bodies. The big questions are the structure and development of the universe. Astronomy is one of the oldest sciences. The patterns in the night sky were called constellations by the Arabs. They used the positions of the stars to navigate, and to find when was the best time to plant crops. Astrophysics is an important part of astronomy. A related subject, cosmology, is concerned with studying the universe as a whole, and the way the universe changed over time. Astronomy is not the same as astrology, a belief that the motion of the stars and the planets may affect human lives.

There are two main types of astronomy, observational and theoretical astronomy. Observational astronomy uses telescopes and cameras to observe or look at stars, galaxies and other astronomical objects. Theoretical astronomy explains what we see. It predicts what might happen. Observations show whether the predictions work. The main work of astronomy is to explain puzzling features of the universe. For many years the most important issue was the motions of planets. Many other topics are now studied. Day-time astronomy is possible. First, there's the Sun, but observing directly is dangerous. It is too bright, and can burn your eyes and can cause permanent blindness. To look at the Sun you need proper shields and equipment. Some other individual bright stars and planets can be seen during daylight hours through a telescope or a powerful pair of binoculars. History of astronomy

Ancient history Early astronomers used only their eyes to look at the stars. They made maps of the constellations and stars for religious reasons and calendars to work out the time of year. Early civilisations such as the Maya people and the Ancient Egyptians built simple observatories and drew maps of the stars positions. They also began to think about the place of Earth in the universe. For a long time people thought Earth was the center of the universe, and that the planets, the stars and the sun went around it. This is known as geocentrism. Astronomy is from the Greek astron (ἄστρον) meaning "star" and nomos (nόμος) meaning "law")

Ancient Greeks tried to explain the motions of the sun and stars by taking measurements. A mathematician named Eratosthenes was the first who measured the size of the Earth and proved that the Earth is a sphere. A theory by another mathematician named Aristarchus was, that the sun is the center and the Earth is moving around it. This is known as heliocentrism. Only a few people thought it was right. The rest continued to believe in the geocentric model. Most of the names of constellations and stars come from Greeks of that time. Arabic astronomers made many advancements during the Middle Ages including improved star maps and ways to estimate the size of the Earth. They also learned from the ancients by translating Greek books into Arabic. Renaissance to modern era

During the renaissance a priest named Nicolaus Copernicus thought, from looking at the way the planets moved, that the Earth was not the center of everything. Based on previous works, he said that the Earth was a planet and all the planets moved around the sun. This brought back the old idea of heliocentrism. Galileo Galilei built his own telescopes, and used them to look more closely at the stars and planets for the first time. He agreed with Copernicus. The Catholic Church thought Galileo was wrong. He spent the rest of his life under house arrest. Heliocentric ideas were soon improved by Johannes Kepler and Isaac Newton, who invented the theory of gravity. After Galileo, people made better telescopes and used them to see farther objects such as the planets Uranus and Neptune. They also saw how stars were similar to our Sun, but in a range of colours and sizes. They also saw thousands of other faraway objects such as galaxies and nebulae.

Modern era The 20th century after 1920 saw important changes in astronomy. In the early 1920s it began to be accepted that the galaxy in which we live, the Milky Way, is not the only galaxy. The existence of other galaxies was settled by Edwin Hubble, who identified the Andromeda nebula as a different galaxy. It was also Hubble who proved that the universe was expanding. There were many other galaxies at large distances and they are receding, moving away from our galaxy. That was completely unexpected. In 1931, Karl Jansky discovered radio emission from outside the Earth when trying to isolate a source of noise in radio communications, marking the birth of radio astronomy and the first attempts at using another part of the electromagnetic spectrum to observe the sky. Those parts of the electromagnetic spectrum that the atmosphere did not block were now opened up to astronomy, allowing more discoveries to be made.

The opening of this new window on the Universe saw the discovery of entirely new things, for example pulsars, which sent regular pulses of radio waves out into space. The waves were first thought to be alien in origin because the pulses were so regular that (so it was thought) it implied an artificial source. The period after World War II saw more observatories. Large and accurate telescopes were built and operated at good observing sites, usually by governments. For example, Bernard Lovell began radio astronomy at Jodrell Bank using leftover military radar equipment. By 1957, the site had the largest steerable radio telescope in the world. Similarly, the end of the 1960s saw the start of the building of dedicated observatories at Mauna Kea in Hawaii, a good site for visible and infra-red telescopes thanks to its high altitude and clear skies. The next great revolution in astronomy was thanks to the birth of rocketry. This allowed telescopes to be placed in space on satellites.

Space telescopes gave access, for the first time in history, to the entire electromagnetic spectrum including rays that had been blocked by the atmosphere. The X-rays, gamma rays, ultraviolet light and parts of the infra-red spectrum were all opened to astronomy as observing telescopes were launched. As with other parts of the spectrum, new discoveries were made. From 1970s satellites were launched to be replaced with more accurate and better satellites, causing the sky to be mapped in nearly all parts of the electromagnetic spectrum. Discoveries Discoveries broadly come in two types: bodies and phenomena. Bodies are things in the Universe, whether it is a planet like our Earth or a galaxy like our Milky Way. Phenomena are events and happenings in the Universe. Bodies For convenience, this section has been divided by where these astronomical bodies may be found: those found around stars are solar bodies, those inside galaxies are galactic bodies and everything else larger are cosmic bodies.

Solar Planets Asteroids Comets Galactic Stars Diffuse Objects: Nebulas Clusters Compact Stars: White dwarf stars Neutron stars Black holes Cosmic Galaxies Galaxy clusters Superclusters Phenomena Burst events are those where there is a sudden change in the heavens that disappears quickly. These are called bursts because they are normally associated with large explosions producing a "burst" of energy. They include: Supernovas Novas Periodic events are those that happen regularly in a repetitive way. The name periodic comes from period, which is the length of time required for a wave to complete one cycle. Periodic phenomena include: Pulsars Variable stars

Noise phenomena tend to relate to things that happened a long time ago. The signal from these events bounce around the Universe until it seems to come from everywhere and varies little in intensity. In this way, it is "noise", the background signal that pervades every instrument used for astronomy. The most common example of noise is static seen on analogue televisions. The principal astronomical example is: cosmic background radiation. Methods

Methods Instruments Telescopes are the main tool of observing. They take all the light in a big area and put in into a small area. This is like making your eyes very big and powerful. Astronomers use telescopes to look at things that are far away and dim. Telescopes make objects look bigger, closer, brighter. Spectrometers study the different wavelengths of light. This shows what something is made of. Many telescopes are in satellites. They are space observatories. The Earth’s atmosphere blocks some parts of the electromagnetic spectrum, but special telescopes above the atmosphere can detect that radiation. Radio astronomy uses radio telescopes. Aperture synthesis combines smaller telescopes to create a phased array, which works like a telescope as big as the distance between the smaller telescopes.

Techniques There are way astronomers can get better pictures of the heavens. Light from a distant source reaches a sensor and gets measured, normally by a human eye or a camera. For very dim sources, there may not be enough light particles coming from the source for it to be seen. One technique that astronomers have for making it visible is using integration (which is like longer exposures in photography). Integration Astronomical sources do not move much: only the rotation and movement of the Earth causes them to move across the heavens. As light particles reach the camera over time, they hit the same place making it brighter and more visible than the background, until it can be seen.

Telescopes at most observatories (and satellite instruments) can normally track a source as it moves across the heavens, making the star appear still to the telescope and allowing longer exposures. Also, images can be taken on different nights so exposures span hours, days or even months. In the digital era, digitised pictures of the sky can be added together by computer, which overlays the images after correcting for movement. Adaptive optics Adaptive optics means changing the shape of the mirror or lens while looking at something, to see it better. Data analysis Data analysis is the process of getting more information out of an astronomical observation than by simply looking at it. The observation is first stored as data. This data then has various techniques used to analyse it.

Fourier analysis Fourier analysis in mathematics can show if an observation (over a length of time) is changing periodically (changes like a wave). If so, it can extract the frequencies and the type of wave pattern, and find many things including new planets. Subfields of astronomy Pulsars pulse regularly in radio waves. These turned out to be similar to some (but not all) of a type of bright source in X-rays called a Low-mass X-ray binary. It turned out that all pulsars and some LMXBs are neutron stars and that the differences were due to the environment in which the neutron star was found. Those LMXBs that were not neutron stars turned out to be black holes. This section attempts to provide an overview of the important fields of astronomy. Solar astronomy

Solar astronomy Solar astronomy is the study of the Sun. The Sun is the closest star to Earth at around 92 million (92,000,000) miles away. It is the easiest to observe in detail. Observing the Sun can help us understand how other stars work and are formed. Changes in the Sun can affect the weather and climate on Earth. A stream of charged particles called the Solar wind is constantly sent off from the Sun. The Solar wind hitting the Earth's magnetic field causes the northern lights. Stellar Astronomy Stellar Astronomy, sometimes generally stellar astrophysics is the scientific study of stars, their formation, evolution and fate (stellar evolution). In the most basic sense,Stellar Astronomy attempts to answer the questions to the universe's most common phenomena — stars. Heavily relating with Galactic and Planetary Astronomy.

Planetary astronomy Planetary astronomy is the study of planets, moons, dwarf planets, comets and asteroids as well as other small objects that orbit stars. The planets of our own Solar System have been studied in depth by many visiting spacecraft such as Cassini-Huygens (Saturn) and the Voyager 1 and 2. Galactic astronomy Galactic astronomy is the study of distant galaxies. Studying distant galaxies is a good way of learning about our own galaxy, as the gases and stars in our own galaxy make it difficult to observe. Galactic astronomers try to understand the structure of galaxies and how they are formed by using different types of telescopes and computer simulations.

Gravitational wave astronomy Gravitational wave astronomy is the study of the Universe in the gravitational wave spectrum. So far, all astronomy that has been done has used the electromagnetic spectrum. Gravitational waves are ripples in spacetime emitted by very dense objects changing shape, which include white dwarves, neutron stars and black holes. Because no one has been able to detect gravitational waves directly, the impact of gravitational wave astronomy has been limited. Unsolved problems Great discoveries also produce unsolved problems. This is just a short-list: Dark matter and dark energy: what are they? Ultimate fate of the Universe? What will it be? Why is lithium 4 times less than predicted? Origin of supermassive black holes. The source of ultra-high energy cosmic rays. The existence of life elsewhere. Related pages Asteroid Astrobiology Black hole Comet Galaxy Meteor Planet Planetarium Satellite (natural) Solar system Star Universe References Other websites

Other websites Astronomy site specifically designed for kids and their parents. Astronomy Picture of the Day

Architecture is the process of designing structures and buildings. It uses both art and engineering. Examples include houses, churches, hotels, office buildings, roads, viaducts, tunnels and bridges. Architecture is the profession of an architect. Usually, a person must study at an institution of higher education (university) to become an architect. There were architects long before there was higher education. They learnt by being an apprentice to an established architect. Architecture can do small designs, such as for a garage, or large designs, such as for a whole city. The capital cities of Brasília, and Canberra were designed. Architects often work with structural engineers to make structurally sound buildings. History

History In the past, people built huts and wood houses to protect themselves from the weather. For safety, they were often close together. Great civilizations like the Ancient Egyptians built large temples and structures, like the Great Pyramids of Giza. The Ancient Greeks and Romans made what we now call "Classical Architecture". The Romans, working over 2000 years ago, copied the arch from the Etruscans, who copied it from the Mesopotamians.

Classical architecture was formal, and it always obeyed laws. It used symmetry, which really means balance, and it used proportion between shapes. The Golden Mean was a rule which said, (to put it simply) if you are making a room, or any other thing, it will work best if you always make the long side 1.6 times as long as the short side. There are many 'laws' in classical architecture, like how high the middle of an arched bridge needs to be (which depends on how wide the bridge needs to be). These laws were learned from thousands of years of experience and they are often used today. However, today more notice is taken of specific facts, such as what wind speeds occur once or twice in a century. Several bridges have blown down because that was not properly taken into consideration. In some parts of the world, like India, the architecture is famous for carving the stone on temples and palaces. Different architectural styles occur in China, Japan, Southeast Asia, Africa, Mexico, and Central and South America.

Architects in Western Europe in the Middle Ages made Romanesque architecture, then Gothic architecture. Gothic buildings have tall, pointed windows and arches. Many churches have Gothic architecture. Castles were also built at this time. In Eastern Europe, churches usually had domes. People added their own ideas and decoration to the Classical Architecture of the past. The Renaissance brought a return to classical ideas.

In the late 18th century with the Industrial Revolution, people began to invent machines to make things quickly and cheaply. Many factories and mills were built during, or after this revolution. Decades later, in the Victorian era, architects like George Fowler Jones and Decimus Burton still followed the Gothic style to build new churches. Up to this point, buildings were limited in size and style by the strength of the wood and masonry used to construct them. Gothic cathedrals were among the largest buildings because the gothic arch when combined with buttresses allowed stone buildings to be built taller. For example, the cathedral in Ulm, Germany is over 500 feet tall. However, building with stone has its limits, and building too tall could result in collapse. This happened to the Beauvais Cathedral, which was never completed.

Towards the end of the 19th Century with a second Industrial Revolution, steel became much cheaper. Architects began to use inventions like metal girders and reinforced concrete to build. An example is the Eiffel Tower in Paris. Buildings can now be built taller than ever before. We call them skyscrapers. This new technology has made us free from traditional limitations, and because of the new possibilities presented by these materials, many traditional methods of construction and ideas about style were reevaluated, replaced, or abandoned. Cheap, strong glass soon brought transparent exterior walls, especially for office buildings.

Modernism is the name for the architectural style which developed because of these new building technologies, and its beginnings can been seen as early as 1890. Modernism can also refer to a specific group of architects and buildings from the early to late 20th century, and so may not be the proper term to use for many building built since then, which are sometimes called "post-modern". Many of the world's greatest structures were built by modern-day architects such as Frank Lloyd Wright; Sir Hugh Casson; Norman Foster; I. M. Pei; Adrian Smith; Edward Durell Stone; Frank Gehry; Fazlur Khan; Gottfried Böhm; and Bruce Graham. Related pages Acoustics Architect Art Building code Building materials Earthquake engineering List of buildings Pattern language Skyscraper Structural Engineering World Heritage Sites References Other websites

Other websites American Institute of Architects Australian Institute of Architects Royal Institute of British Architects Royal Architectural Institute of Canada New Zealand Institute of Architects Architecture Citizendium

Anatomy is the study of the bodies of people and other animals. Anatomy is the study of the inside of the body and outside the body. Anatomy notes the position and structure of organs such as muscles, glands and bones. A person who studies anatomy is an anatomist. The history of anatomy dates back to 1600 BC when Egyptians began studying human anatomy. They discovered the functions of many organs like the liver, spleen, kidneys, heart etc. and were the first to discover the structure and functions of the lymphatic system. For long periods the dissection of deceased people was forbidden, and correct ideas about human anatomy was a long time coming. Academic human anatomists are usually employed by universities, medical schools and teaching hospitals. They are often involved in teaching and research. Gross anatomy studies parts of the body that are big enough to see. Micro-anatomy studies smaller parts.

Body systems There are different organ systems, such as the cardiovascular system, also known as the circulatory system (the system that gets blood around the body), the muscular system (the system that contains muscles), the nervous system (the system that controls the nerves,and the brain) and the skeleton (the bones). Anatomy, physiology and biochemistry are similar basic medical sciences. Related pages Anatomical terms of location Medicine Zoology Comparative anatomy Organ (anatomy) Gray's Anatomy Vesalius William Harvey References

An asteroid is a minor planet that orbits within the inner solar system. It is a small object in the Solar System that travels around the Sun. It is like a planet but smaller. They range from very small (smaller than a car) to 600 miles (1000 km) across. A few asteroids have asteroid moon. The name "asteroid" means "like a star" in the ancient Greek language. Asteroids may look like small stars in the sky, but they really do move around the Sun. Like planets, asteroids do not make their own light. Because of this, some people think "asteroids" is not a good name, and think that the name "planetoid" ("like a planet") would be a better name.

Giuseppe Piazzi found the first asteroid, in 1801. He called it Ceres, and it is the biggest object in the asteroid belt. Others, like Juno, Pallas, and Vesta were found later. In the 1850s, so many had been found that they were numbered by a Minor planet designation starting with 1 Ceres. Today, astronomers using computerized telescopes find thousands of asteroids every month. Asteroid impact prediction is one of their purposes. Asteroids are the leftover rock and other material from the formation of the Solar System. These rocks were too small to come together to make a planet. Some are made of carbon or metal. Depending on what's on the surface, they are classified into various asteroid spectral types including Type M (metal), Type S (stone), and Type C (carbon).

Most asteroids in our Solar System are in the asteroid belt between Mars and Jupiter. Many are not in the main asteroid belt. The ones that come close to Earth are called Near-Earth asteroids. Some scientists think asteroids striking the Earth killed off all the dinosaurs and caused some of the other extinction events. References

Afghanistan, officially the Islamic Emirate of Afghanistan (Pashto/Dari: ), is a country in Central Asia. It borders with Pakistan in the south and east, Iran in the west, Turkmenistan, Uzbekistan and Tajikistan in the north, and China in the far northeast. Kabul is the country's capital city. Afghanistan is currently governed by the Taliban, after the collapse of the internationally recognized Islamic Republic of Afghanistan on 15 August 2021. In early times people passed through it with animals and other goods as it connected China and India with Central Asia and the Middle East. More recently, Afghanistan has been damaged by many years of war. There are not enough jobs. The country is around in size. There are 40.976 million people in Afghanistan. There are about 3 million Afghan refugees (people who had to leave the country) who are in Pakistan and Iran for some time. In 2011, its capital, Kabul, had about 3,691,400 people living in it.

United Nations Human Rights Council decided in October to appoint (an independent expert, or) United Nations special rapporteur on "Afghanistan to [find out about, or] probe violations carried out by the Taliban and" others who are now part of a [big] conflict, media said. Geography Afghanistan has many mountains. The mountains are called the Hindu Kush and Himalayas. The tallest mountain in Afghanistan is Mount Nowshak. There are plains (which have soil that is good for growing plants) and foothills. Parts of the country are also dry, especially the Registan Desert. Afghanistan has snow and glaciers in the mountains. Amu Darya is the big water stream, or river. The country has an abundance of a valuable stone called lapis lazuli, which was also used to decorate the tomb of the Egyptian pharaoh Tutankhamun. Climate Afghanistan has a continental climate with hot summers and cold winters. Having no water sometimes causes problems for farmers. Sandstorms happen a lot in the desert. Plants and animals

Southern Afghanistan has not many plants because it is dry. There are more plants where there is more water. Mountains have forests of pine and fir, cedar, oak, walnut, alder, and ash trees. Afghanistan's wild animals live in the mountains. There are wolves, foxes, jackals, bears, and wild goats, gazelles, wild dogs, camels, and wild cats such as the snow leopard in the country. The birds are falcons, eagles and vultures. The Rhesus Macaque and the red flying squirrel are also in Afghanistan. Many years of war, hunting, and years of no water have killed animals in Afghanistan. There used to be tigers in Afghanistan, but now there aren't any. Bears and wolves are almost gone. People and culture Many people have moved through or invaded the land of Afghanistan. Today's people of Afghanistan are known as Afghans. They have many traits passed down from these previous peoples.

The largest group of people are the Pashtuns. These make up about half the population. Tajiks are the second-largest ethnic group, making up about one-fifth of the population. Before the 20th century, Tajiks were called Sarts and some come from the Iranian peoples. Most Pashtuns are also related to the Iranian peoples. Some Pashtuns and Tajiks marry each other but at the same time they are rivals. The third-largest group are the Hazaras. They are native to the Hazaristan area in central Afghanistan. The country's other groups include the Uzbek, Aimaq, Turkmen, Nuristani, Baloch, Pashayi and a few others. Dari-Persian and Pashto are the official languages of Afghanistan. Many people speak both languages. Both are Indo-European languages from the Iranian languages sub-family. They are usually written with the Arabic alphabet. Uzbek and Turkmen are widely spoken in the north and Nuristani and Pashai are spoken in the east. Around 99% of all Afghans follow the religion of Islam.

Afghanistan is a largely rural country. This means there are only a few major cities. About one fifth of the population live in cities. Kabul, the capital, is the largest city. It is south of the Hindu Kush range and alongside the Kabul River. Other cities in Afghanistan include Kandahar, Herat, Mazar-e Sharif, and Jalalabad. The rural population is made up of farmers and nomads. The farmers live mainly in small villages along the rivers. The nomads live in tents while moving from place to place with their animals and belongings. Some people live in the high central mountains. Some live in the deserts in the south and southwest. Millions of people left Afghanistan to get away from the wars that happened in the late 20th and early 21st centuries. Most of them lived in neighboring Pakistan and Iran.

History Afghanistan is in the path of important trade routes that connect southern and eastern Asia to Europe and the Middle East. Because of this, many empire builders have decided to rule over the area. Signs that these emperors were near Afghanistan still exist in many parts of the country. Afghanistan is near what used to be the Silk Road, so it has many cultures. From up to 8,000 years ago, the peoples of Afghanistan helped develop (create) major world religions, traded and exchanged many products, and sometimes controlled politics and culture in Asia. Prehistory

Prehistory Archaeologists digging a cave in what is now northeastern Afghanistan (in Badakhshan), discovered that people lived in the country as early as 100,000 years ago. They found the skull of a Neanderthal, or early human, as well as tools from about 30,000 years ago. In other parts of Afghanistan, archaeologists uncovered pottery and tools that are 4,000 to 11,000 years old—evidence that Afghans were among the first people in the world to grow crops and raise animals.

Farmers and herders settled in the plains surrounding the Hindu Kush as early as 7000 B.C. These people may have grown rich off the lapis lazuli they found along riverbeds, which they traded to early city sites to the west, across the Iranian plateau and Mesopotamia. As farms and villages grew and thrived in Afghanistan, these ancient people eventually invented irrigation (digging ditches for water so it flows to crops) that allowed them to grow crops on the northern Afghanistan desert plains. This civilization (advanced state of organization) is today called BMAC (Bactria–Margiana Archaeological Complex), or the "Oxus civilization".

The Oxus civilization expanded as far east as western edge of the Indus Valley during the period between 2200 and 1800 B.C. These people, who were the ancestors of the Indo-Aryans, used the term "Aryan" to identify their ethnicity, culture, and religion. Scholars know this when they read the ancient texts of these people; the Avesta of Iranic peoples and the Vedas of Indo-Aryans. Zoroaster, the founder of the Zoroastrian religion, the world's earliest monotheistic religion, (meaning a religion believing in one god) lived in the area (somewhere north of today's Afghanistan), around 1000 B.C. Ancient history

Ancient history Before the middle of the sixth century BCE, Afghanistan was held by the Medes. Then the Achaemenids took over control of the land and made it part of the Persian empire. Alexander the great defeated and conquered the Persian Empire in 330 BCE. He founded some cities in the area. The people used Macedonian culture and language. After Alexander, Greco-Bactrians, Scythians, Kushans, Parthians and Sassanians ruled the area. Kushans spread Buddhism from India in the 1st century BCE, and Buddhism remained an important religion in the area until the Islamic conquest in the 7th century CE. The Buddhas of Bamiyan were giant statues, a reminder of Buddhism in Afghanistan. They were destroyed by the Taliban in 2001. There were international protests. The Taliban believe that the ancient statues were un-Islamic and that they had a right to destroy them. Medieval history

Medieval history Arabs introduced Islam in the 7th century and slowly began spreading the new religion. In the 9th and 10th centuries, many local Islamic dynasties rose to power inside Afghanistan. One of the earliest was the Tahirids, whose kingdom included Balkh and Herat; they established independence from the Abbasids in 820. The Tahirids were succeeded in about 867 by the Saffarids of Zaranj in western Afghanistan. Local princes in the north soon became feudatories of the powerful Samanids, who ruled from Bukhara. From 872 to 999, north of the Hindu Kush in Afghanistan enjoyed a golden age under Samanid rule.

In the 10th century, the local Ghaznavids turned Ghazni into their capital and firmly established Islam throughout all areas of Afghanistan, except the Kafiristan region in the northeast. Mahmud of Ghazni, a great Ghaznavid sultan, conquered the Multan and Punjab region, and carried raids into the heart of India. Mohammed bin Abdul Jabbar Utbi (Al-Utbi), a historian from the 10th century, wrote that thousands of "Afghans" were in the Ghaznavid army. The Ghaznavid dynasty was replaced by the Ghorids of Ghor in the late 12th century, who reconquered Ghaznavid territory in the name of Islam and ruled it until 1206. The Ghorid army also included ethnic Afghans. Afghanistan was recognized as Khorasan, meaning "land of the rising sun," which was a prosperous and independent geographic region reaching as far as the Indus River.

All the major cities of modern Afghanistan were centers of science and culture in the past. The New Persian literature arose and flourished in the area. The early Persian poets such as Rudaki were from what is now Afghanistan. Moreover, Ferdowsi, the author of Shahnameh, the national epic of Iran, and Rumi, the famous Sufi poet, were also from modern-day Afghanistan. It has produced scientists such as Avicenna, Al-Farabi, Al-Biruni, Omar Khayyám, Al-Khwarizmi, and many others who are widely known for their important contributions in areas such as mathematics, astronomy, medicine, physics, geography, and geology. It remained the cultural capital of Persia until the devastating Mongol invasion in the 13th century.

Timur, the Turkic conqueror, took over in the end of the 14th century and began to rebuild cities in this region. Timur's successors, the Timurids (1405–1507), were great patrons of learning and the arts who enriched their capital city of Herat with fine buildings. Under their rule Afghanistan enjoyed peace and prosperity.

Between south of the Hindu Kush and the Indus River (today's Pakistan) was the native land of the Afghan tribes. They called this land "Afghanistan" (meaning "land of the Afghans"). The Afghans ruled the rich northern Indian subcontinent with their capital at Delhi. From the 16th to the early 18th century, Afghanistan was disputed between the Safavids of Isfahan and the Mughals of Agra who had replaced the Lodi and Suri Afghan rulers in India. The Safavids and Mughals occasionally oppressed the native Afghans but at the same time the Afghans used each empire to punish the other. In 1709, the Hotaki Afghans rose to power and completely defeated the Persian Empire. Then they marched towards the Mughals of India and nominally defeated them with the help of the Afsharid forces under Nader Shah Afshar.

In 1747, after Nader Shah of Persia was killed, a great leader named Ahmad Shah Durrani united all the different Muslim tribes and established the Afghan Empire (Durrani Empire). He is considered the founding father of the modern state of Afghanistan while Mirwais Hotak is the grandfather of the nation. Since the 1800s During the 1800s, Afghanistan became a buffer zone between two powerful empires, the British Indian Empire and the Russian Empire. As British India advanced into Afghanistan, Russia felt threatened and expanded southward across Central Asia. To stop the Russian advance, Britain tried to make Afghanistan part of its empire but the Afghans fought wars with British-led Indians from 1839 to 1842 and from 1878 to 1880. After the third war in 1919, Afghanistan under King Amanullah gained respect and recognition as a completely independent state.

The Kingdom of Afghanistan was a constitutional monarchy established in 1926. It was the successor state to the Emirate of Afghanistan. On 27 September 1934, during the reign of Zahir Shah, the Kingdom of Afghanistan joined the League of Nations. During World War II, Afghanistan remained neutral. It pursued a diplomatic policy of non-alignment. The creation of Pakistan in 1947 as its eastern neighbor created problems. In 1973, political crises led to the overthrow of the king. The country's new leader ended the monarchy and made Afghanistan a republic. In 1978, a Communist political party supported by the Soviet Union seized control of Afghanistan's government. This move sparked rebellions throughout the country. The government asked the Soviet Union for military assistance. The Soviets took advantage of the situation and invaded Afghanistan in December 1979.

Most people in Afghanistan opposed the sudden Soviet presence in their country. For nearly a decade, anti-Communist Islamic forces known as Mujahideen were trained inside neighboring Pakistan to fight the Soviets and the Afghan government. The United States and other anti-Soviet countries supported the Mujahideen. In the long war, over one million Afghan civilians were killed. The Soviet Army also lost more than 15,000 soldiers in that war. Millions of Afghans left their country to stay safe in neighboring Pakistan and Iran. In 1989 the Soviet Army withdrew the last of its troops.

After the Soviets left in 1989, the Afghan Civil War started; different Afghan warlords began fighting for control of the country. The warlords received support from other countries, including neighboring Pakistan and Iran. A very conservative Islamic group known as the Taliban emerged in an attempt to end the civil war. By the late 1990s the Taliban had gained control over 95% of Afghanistan. A group known as the Northern Alliance, based in northern Afghanistan near the border with Tajikistan, continued to fight against the Taliban. The Taliban ruled Afghanistan according to their strict version of Islamic law. People whom the Taliban believed violated these laws were given cruel punishments. In addition, the Taliban completely restricted the rights of women. Because of such policies, most countries refused to recognize the Taliban government. Only Pakistan, Saudi Arabia and the United Arab Emirates (UAE) accepted them as the official government.

The Taliban also angered other countries by allowing suspected terrorists to live freely in Afghanistan. Among them were Osama bin Laden and members of the al-Qaeda terrorist network. In September 2001, the United States blamed bin Laden for the terrorist attacks on the World Trade Center in New York City and the Pentagon outside Washington, D.C. The Taliban refused to hand him over to the United States. In response, the United States and its allies launched a bombing campaign against al-Qaeda in October 2001. Within months the Taliban abandoned Kabul, and a new government led by Hamid Karzai came to power, but fighting between the Taliban and US-led armies continued. Taliban fighters have gone into Afghanistan from neighboring Pakistan. Afghans accuse Pakistan's military of being behind the Taliban militants but Pakistan has rejected this and stated that a stable Afghanistan is in Pakistan's own interest.

In December 2004, Hamid Karzai became the first democratically elected president of Afghanistan. NATO began rebuilding Afghanistan, including its military and government institutions. Many schools and colleges were built. Freedom for women has improved. Women can study, work, drive, and run for office. Many Afghan women work as politicians, some are ministers while at least one is a mayor. Others have opened businesses, or joined the military or police. Afghanistan's economy has also improved dramatically, and NATO agreed in 2012 to help the country for at least another 10 years after 2014. In the meantime, Afghanistan improved diplomatic ties with many countries in the world and continues. In August 2021, the Cabinet of Afghanistan lost its power. Most of the country fell to the Taliban on 15 August 2021 with President Ashraf Ghani escaping the country. As of 18 August 2021, the former government's last remaining holdout is the Panjshir Valley.

Government Since the Taliban captured Kabul on 15 August 2021, the governance of Afghanistan is disputed between the Islamic Emirate of Afghanistan and the Islamic Republic of Afghanistan. According to Transparency International, Afghanistan remains in the top most corrupt countries list. Provinces As of 2004, there are thirty-four provinces. Each province is divided into districts. (For cities see List of cities in Afghanistan.)

Relationship with other countries Russia's ambassador (Dmitrij Zjirnov) had a meeting with representatives from Taliban on 18 August 2021; Russia's embassy was still in operation (or open). An "Indian [ diplomat or] envoy to Qatar" had [at least one] meeting "with Taliban leader Stanekzai in Doha in late August", media said. A United States "team led by" [then] "Deputy Special Representative Tom West and [a] top USAID humanitarian official" had meetings, in Qatar in October, with Afghanistani officials. Women's rights was a subject during the talks.

Norway's ambassador visited Afghanistan - and had meetings with Taliban - during a two-day visit in the middle of January 2022. Representatives of the Taliban leadership will come to Norway and meet diplomats from different countries, during 23.-25. January. Also, Norway has stopped (as of 2022's first quarter) supporting with money - (to) the authorities of Afghanistan, media said. Previously, Norwegian diplomats had at least two meetings with Taliban in Doha, in 2021's fourth quarter; There are no political talks yet (as of 2021's fourth quarter); the talks are about humanitarian aid and evacuation. Turkey's foreign minister had a meeting (in Turkey) with "a delegation led by" foreign minister of Afghanistan, in 2021's fourth quarter. In Russia, a meeting about Afghanistan was held on October 20; "The participants [... were] India, USA, Afghanistan, China, Pakistan, Iran and Central Asian" countries, media said.

Diplomatic missions that still represent the Islamic Republic of Afghanistan The ambassador in Oslo, Norway does not recognize the Taliban-led government (as of 2021's fourth quarter). Related pages Government of Afghanistan Afghanistan at the Olympics Afghanistan national football team List of rivers of Afghanistan Saeeda Etebari, Afghan jeweler Wahida Amiri, Afghan activist Notes References Other websites Afghan Studies Center Least developed countries Members of the Organisation of Islamic Cooperation 1709 establishments Former British colonies Landlocked countries Afghanistan

Angola, officially the Republic of Angola, is a country in southern Africa. It shares borders with Namibia in the south, the Democratic Republic of the Congo in the north, and Zambia in the east. Its west border touches the Atlantic Ocean. Its coastline is 1600 kilometers. Angola's capital is Luanda. The country has many natural resources. Angola is the seventh largest country in Africa. The capital and most populated city of Angola is Luanda. Angola is a member state of the African Union, the Community of Portuguese Language Countries, the Latin Union, South Atlantic Peace and Cooperation Zone and the Southern African Development Community. History Portugal built up its power in Angola from the late 15th to the middle 20th century.

After independence there was a civil war from 1975 to 2002. Cuba and the Soviet Bloc supported the ruling People's Movement for the Liberation of Angola (MPLA). South Africa supported the insurgent National Union for the Total Independence of Angola (UNITA) until the end of apartheid. The war ended after the rebel leader Jonas Savimbi was killed. Geography Angola is the world's twenty-third largest country. Angola is bordered by Namibia to the south, Zambia to the east, the Democratic Republic of the Congo to the north-east, the Republic of the Congo via the exclave of Cabinda, and the South Atlantic Ocean to the west. Climate Angola's average temperature on the coast is in the winter and in the summer. It has two seasons; dry (May to October) and hot rainy (November to April). Demographics Angola had a population of 25,789,024 in 2014. Provinces Angola is divided into eighteen provinces. See List of settlements in Angola for the cities and towns in the country.

Related pages Angola at the Olympics Angola national football team List of rivers of Angola References Other websites Portuguese-speaking countries Least developed countries 1975 establishments in Africa

Argentina (officially the Argentine Republic) is a country in South America. Argentina is the second-largest country in South America and the eighth-largest country in the world. Spanish is the most spoken language, and the official language, but many other languages are spoken. There are minorities speaking Italian, German, English, Quechua and even Welsh in Patagonia. In eastern Argentina is Buenos Aires, the capital of Argentina, it is also one of the largest cities in the world. In order by number of people, the largest cities in Argentina are Buenos Aires, Córdoba, Rosario, Mendoza, La Plata, Tucumán, Mar del Plata, Salta, Santa Fe, and Bahía Blanca.

Argentina is between the Andes mountain range in the west and the southern Atlantic Ocean in the east and south. It is bordered by Paraguay and Bolivia in the north, Brazil and Uruguay in the northeast, and Chile in the west and south. It also claims the Falkland Islands (Spanish: Islas Malvinas) and South Georgia and the South Sandwich Islands. Most citizens of the Argentine Republic are descendants of immigrants from Europe. They are united by citizenship and not necessarily by ethnicity. Most Argentinians embrace both their ethnic origins and Argentinian nationality. History The name Argentina comes from the Latin argentum (silver) as the Spanish conquistadors believed the area had silver. In the Americas (South and North), Canada, US, Brazil and Argentina are the largest countries (in that order).

The oldest signs of people in Argentina are in the Patagonia (Piedra Museo, Santa Cruz), and are more than 13,000 years old. In 1480 the Inca Empire conquered northwestern Argentina, making it part of the empire. In the northeastern area, the Guaraní developed a culture based on yuca and sweet potato however typical dishes all around Argentina are pasta, red wines (Italian influence) and beef. Other languages spoken are Italian, English and German. Lunfardo is Argentinean slang and is a mix of Spanish and Italian. Argentinians are said to speak Spanish with an Italian accent.

Argentina declared independent from Spain in 1816, and achieved it in a War led by José de San Martín in 1818. Many immigrants from Europe came to the country. By the 1920s it was the 7th wealthiest country in the world, but it began a decline after this. In the 1940s, following the "infamous decade" where the country's politics were not stable, Juan Peron came to power. Peron was one of the most important people in the country's history and many politicians today call themselves Peronist. Peron was forced out of power in 1955. After spending years in exile he returned to power in the 1970s. In 1976, the country was falling into chaos, and the military took power. This was not the first time the military had done this. Leading the new government was Jorge Rafael Videla. Videla was one of history's most brutal dictators. Thousands of people disappeared or were killed during his time as president. Videla retired in 1980.

One of his successors was another general turned dictator, Leopoldo Galtieri. By the time Galtieri was in office in 1981 the dictatorship became unpopular. To stir up support, Galtieri ordered an invasion of the Falkland Islands, starting the Falklands War. Argentina lost the war, and soon the country fell into chaos again. Galtieri was removed from power and eventually democracy was restored. Galtieri and Videla would be charged with "crimes against humanity" because of the mass murder and other crimes that they ordered as president. In the early 21st century Argentina is one of the most important countries in Latin America, though it still has many problems. It has a large economy and is influential in the "southern cone" of South America and a member of the G20 developing nations. Politics Argentina is a federal republic. The people of Argentina vote for a President to rule them and Senators and Deputies to speak for them and make laws for them. The President is Alberto Fernández since December 2019.

Administrative divisions Argentina is divided into 23 provinces (provincias; singular: provincia), and 1 city (commonly known as capital federal): Geography Argentina is almost 3,700 km long from north to south, and 1,400 km from east to west (maximum values). It can be divided into three parts: the Pampas in the central part of the country, Patagonia in the southern part down to Tierra del Fuego; and the Andes mountain range along the western border with Chile, with the highest point in the province of Mendoza. Cerro Aconcagua, at 6,960 metres (22,834 ft), is the Americas' highest mountain. The most important rivers include the River Plate, Paraguay, Bermejo, Colorado, Uruguay and the largest river, the Paraná. River Plate was incorrectly translated though, and should have been translated to English as River of (the) Silver. River Plate is also a famous Buenos Aires soccer team. See List of cities in Argentina for the many places people live in Argentina.

Other information The majority of the Argentineans are descendants of Europeans mainly from Spain, Italy, Germany, Ireland, France, other Europeans countries and Mestizo representing more than 90% of the total population of the country. More than 300,000 Roma gypsies live in Argentina. Since the 1990s, Romanian, Brazilian and Colombian gypsies arrived in Argentina. Football or soccer is the most popular sport, although the national sport of the country is Pato. Argentina has a number of highly ranked Polo players. Field hockey (for women) rugby and golf are also favorites. Argentina is a Christian country. Most of Argentina's people (80 percent) are Roman Catholic. Argentina also has the largest population of Jewish community after Israel and US. Middle Eastern immigrants who were Muslims converted to Catholicism, but there are still Muslims as well. Medicine is socialized and so is education, making Argentina's literacy rate about 98%. State University is free as well.

Related pages Argentina at the Olympics Argentina national football team List of rivers of Argentina References General information and maps Geography and tourism Pictures from Argentina grouped by provincia Other websites Argentina.gov.ar - Official national portal Gobierno Electrónico - Official government website Presidencia de la Nación - Official presidential website Honorable Senado de la Nación - Official senatorial website Honorable Cámara de Diputados de la Nación - Official lower house website Secretaría de Turismo de la Nación - Official tourism board website Spanish-speaking countries

Austria (, ; ), officially the Republic of Austria ( ), is a country in Central Europe. Around Austria there are the countries of Germany, Czech Republic, Slovakia, Hungary, Slovenia, Italy, Switzerland, and Liechtenstein. The people in Austria speak German, a few also speak Hungarian, Slovenian and Croatian. The capital of Austria is Vienna (Wien). History Austria is more than a thousand years old. Its history can be followed to the ninth century. At that time the first people moved to the land now known as Austria. The name "Ostarrichi" is first written in an official document from 996. Since then this word has developed into the Modern German word Österreich, which literally means "East Empire."

Ancient times There has been human settlement in the area that is now Austria for a long time. The first settlers go back to the Paleolithic age. That was the time of the Neanderthals. They left works of art such as the Venus of Willendorf. In the Neolithic age people were living there to dig for mineral resources, especially copper. Ötzi, a mummy found in a glacier between Austria and Italy, is from that time. In the Bronze Age people built bigger settlements and fortresses, especially where there were mineral resources. Salt mining began near Hallstatt. At that time, Celts began to form the first states. The Romans The Romans came 15 B.C. to Austria and made the Celtic Regnum Noricum to a province. Modern Austria was part of three provinces, Raetia, Noricum and Pannonia. The border in the north was the Danube.

Holy Roman Empire From the early Middle Ages, the area of modern-day Austria was a part of the Holy Roman Empire. The capital of the Holy Roman Empire was the Austrian city Vienna. The Austrian Habsburg family were the rulers of the Empire and the son of the Holy Roman Emperor held the title of Archduke of Austria. In 1806, France defeated the Holy Roman Empire and replaced it with the Confederation of the Rhine. Former Holy Roman Emperor Francis II became the Emperor of the new Austrian Empire, which later became Austria-Hungary. Modern history In 1914, Franz Ferdinand was assassinated in Sarajevo. Austria-Hungary declared war on Serbia and this led to World War I. In 1918, both Austria and Hungary became republics. They also both split into two separate countries. During World War II, Austria was part of Nazi Germany. It became independent in May 1945. Geography

Geography Austria is a mountainous country since it is partially in the Alps. Grossglockner is the tallest mountain in Austria. The high mountainous Alps in the west of Austria flatten somewhat into low lands and plains in the east of the country where the Danube flows. Climate Austria has a continental climate. The highest temperature ever recorded in Austria was , on 8 August 2013 in Bad Deutsch-Altenburg. The lowest temperature ever recorded in Austria was , on 19 February 1932 at Grünloch doline. Politics Austria is a democratic republic. The President of Austria is the head of state and the Chancellor of Austria is the head of government. It is a neutral state, that means it does not take part in wars with other countries. It has been in the United Nations since 1955 and in the European Union since 1995.

Austria is also a federal state and divided into nine states (): Burgenland (Burgenland) Carinthia (Kärnten) Lower Austria (Niederösterreich) Upper Austria (Oberösterreich) Salzburg(erland) (Salzburg) Styria (Steiermark) Tyrol (Tirol) Vorarlberg (Vorarlberg) Vienna (Wien) More information: States of Austria. Currently, the chancellor is Karl Nehammer The previous chancellor was Alexander Schallenberg (2021). Austria has been a member-state of the United Nations since 1955, the European Union since 1995 and OPEC since 2019. Culture Music and Arts Many famous composers were Austrians or born in Austria. There are Wolfgang Amadeus Mozart, Joseph Haydn, Franz Schubert, Anton Bruckner, Johann Strauss, Sr., Johann Strauss, Jr. and Gustav Mahler. In modern times there were Arnold Schoenberg, Anton Webern and Alban Berg, who belonged to the Second Viennese School.

Austria has many artists, there are Gustav Klimt, Oskar Kokoschka, Egon Schiele or Friedensreich Hundertwasser, Inge Morath or Otto Wagner and scienc. Food Famous Austrian dishes are Wiener Schnitzel, Apfelstrudel, Schweinsbraten, Kaiserschmarren, Knödel, Sachertorte and Tafelspitz. But you can also find a lot of local dishes like Kärntner Reindling (a kind of cake), Kärntner Nudeln (also called "Kärntner Kasnudeln", you may write it "...nudln" too), Tiroler Knödl (may be written "...knödel"; ), Tiroler Schlipfkrapfen (another kind of "Kärntner Nudeln"), Salzburger Nockerl (also may be written ..."Nockerln"), Steirisches Wurzelfleisch (..."Wurzlfleisch") or Sterz ("Steirischer Sterz").

UNESCO World Heritage Sites in Austria Historic Centre of Salzburg — 1996 Schönbrunn Palace — 1996 Hallstatt–Dachstein Salzkammergut Cultural Landscape — 1997 Semmering Railway — 1998 Historic Centre of Graz and Schloss Eggenberg — 1999 (extended in 2010) Wachau Cultural Landscape — 2000 Historic Centre of Vienna — 2001 Lake Neusiedl — 2001 Gallery Related pages List of rivers of Austria References Other websites Austria Maps European Union member states German-speaking countries Federations

Armenia (Armenian: Հայաստան, Hayastan), officially the Republic of Armenia, is a landlocked country located in the Armenian Highlands, spanning Eastern Europe and Western Asia. History The Hittites and Hayasa-Azzi may have played a significant role in the ethnicity of Armenians. It has an ancient cultural heritage. One of the earliest Armenian kingdoms such as Urartu was established in 860 BC and by the 6th century BC it was replaced by the Satrapy of Armenia. The Kingdom of Armenia reached its height under Tigranes the Great in the 1st century BC and became the first state in the world to adopt Christianity as its official religion in the late 3rd or early 4th century AD. The official date of state adoption of Christianity is 301.

Foreign invasion Between the 16th century and 19th century, the traditional Armenian homeland composed of Eastern Armenia and Western Armenia came under the rule of the Ottoman and Iranian empires, repeatedly ruled by either of the two over the centuries. By the 19th century, Eastern Armenia had been conquered by the Russian Empire, while most of the western parts of the traditional Armenian homeland remained under Ottoman rule.

20th century During World War I, Armenians living in their ancestral lands in the Ottoman Empire were systematically exterminated in the Armenian Genocide, perpetrated by Ottoman Young Turks. Around 1.5 million people were slaughtered and many more deported. In 1918, following the Russian Revolution, all non-Russian countries declared their independence after the Russian Empire ceased to exist, leading to the establishment of the First Republic of Armenia. By 1920, the state was incorporated into the Transcaucasian Socialist Federative Soviet Republic, and in 1922 became a founding member of the Soviet Union. In 1936, the Transcaucasian state was dissolved, transforming its constituent states, including the Armenian Soviet Socialist Republic, into full Union republics. The modern Republic of Armenia became independent in 1991 during the dissolution of the Soviet Union. 21st century

21st century Administrative divisions Armenia is divided into ten provinces, with the city of Yerevan having special administrative status as the country's capital. The chief executive in each of the ten provinces is the marzpet (marz governor), appointed by the government of Armenia. In Yerevan, the chief executive is the mayor, appointed by the president. , Armenia includes 915 communities, of which 49 are considered urban and 866 are considered rural. † 2011 censusSources: Area and population of provinces. Culture Armenia is a Christian majority country, with European and some wider Eurasian cultural influences. The Republic of Armenia recognises the Armenian Apostolic Church, the world's oldest national church, as the country's primary religious establishment. The unique Armenian alphabet was invented by Mesrop Mashtots in 405 AD.

Armenia is a member of the Council of Europe, the Eurasian Economic Union and the Collective Security Treaty Organization. Armenia supports the de facto independent Republic of Artsakh, which was proclaimed in 1991. Gallery References Notes Armenia Caucasus

Archaeology, or archeology, is the study of the human past. It looks at remains and objects left by the people who lived long ago. These remains may include old coins, tools, buildings, and inscriptions. Archaeologists, the people who study archaeology, use these remains to understand how people lived. Fieldwork When archaeologists do fieldwork, they look for remains, often by digging in the ground. As settlements (places where people lived in groups) change and grow, old buildings get buried. Usually, this is a natural process. A typical student project is to leave an object in a place where there is nothing going on. It will get covered rather quickly, because wind, water and plants will bury it. Sometimes buildings are deliberately buried to make way for new buildings. Ancient Rome, for example, is now up to 40 feet (12 metres) below the present city. This process of natural or man-made burial is why archaeological fieldwork involves digging, and is expensive and takes a long time.

When things are found, or even when nothing is found, the results of the fieldwork are taken back to a base. Short term, the base is often on or near the site. Longer term, the results will usually go to a university or museum. Everything is written down on paper or entered into a computer. Gradually, they build up a picture of what happened long ago. Archaeologists publish their research so others can understand what they learned. Fields of interest Archaeologists do not all study the same topics. They have specialties. Some fields of interest include Ancient Egypt (these specialists are called Egyptologists), Ancient China, or the Vikings. Archaeologists study every civilization that is known, especially the ones where there is no written history. They can study any time period. For example, one might study the beginning of human life in Africa, or study World War II. Marine archaeologists study things that are now underwater. They search for sunken ships or cities that have been lost under the sea.

Subdisciplines There are many different ways of doing archaeology. these depend on the methods used, the things studied, and the environment. Some of these subdisciplines overlap with each other. Marine archaeology Archaeology relating to oceans, seas and lakes is usually done underwater. It includes the study of sunken ships and submerged coastlines. "Maritime archaeology" is a part of this subdivision. It refers to the archaeological investigation of past ships and seafaring. A famous example of maritime archaeology is the recovery and restoration of the ship burial at Sutton Hoo. Ice-patch archaeology When a glacier melts, objects that were captured in it are revealed. The recovery and study of these objects is called "ice-patch archaeology". A famous example is Ötzi the Iceman.

Historical archaeology Historical archaeology deals with places, things, and issues from the past or present at or related to sites with written records or oral traditions. Or it can be defined as "the archaeological investigation of any past culture that has developed a literate tradition." A prominent example of historical archaeology is the work done at Colonial Williamsburg. Industrial archaeology This relatively new branch of archaeology consists of "the systematic study of structures and artefacts as a means of enlarging our understanding of the industrial past." Archaeozoology Archaeozoology, or zooarchaeology, is the study of the relationships between humans and animals in the archaeological record. This includes the study of bones, feathers, teeth and other body parts as well as their interpretation. Experimental archaeology This field involves attempts at replicating the actions and conditions of ancient cultures. Good examples are Butser Ancient Farm and Overton Down.

Sites In many countries, governments and other groups of people protect important archaeological sites so they will not be destroyed and so that visitors can always come and see them. Sometimes archaeological sites are found when foundations are dug for new buildings. Archaeologists have to work quickly when this happens, because people who are building often don't have a lot of time. As soon as the archaeologists are done with their work, the remains that they have found will be covered over, unless they are very important. Related pages Archaeological site Civilization References Other websites Archaeology -Citizendium

The word application has several uses. In medicine, 'application' means putting some drug or ointment usually on the skin where it is absorbed into the human body. In computer software, an application is a type of program which is designed for a particular function. Example: word processing. It is most used to mean a Mobile app. In business or government, an application is a (usually paper) form filled out and handed in by a person seeking a privilege from a state or company, such as work, credit, some type of license or permit, or a place to live. At work, generally engineering, when dealing with certain materials or objects, an "application" is a purpose that material or object can be used for. Wood and steel have many applications.

Animals (or Metazoa) are living creatures with many cells. Animals get their energy from other living things. Usually, they eat them or are parasites. Animals, plants, fungi, and some other living things have complex cells, so they are grouped together as eukaryotes. The study of animals is called zoology. The study of ancient life is called palaeontology. Most animals are mobile, meaning they can move around. Animals take in oxygen, and give out carbon dioxide. This cellular respiration is part of their metabolism (chemical working). In both these ways they are different from plants. Also, the cells of animals have different cell membranes to other eukaryotes like plants and fungi. Plants are also multicellular eukaryotic organisms, but live by using light, water and basic elements to make their tissues.

Grouping animals There are many different types of animals. The common animals most people know are only about 3% of the animal kingdom. When biologists look at animals, they find things that certain animals have in common. They use this to group the animals in a biological classification. Several million species may exist, but biologists have only identified about one million. Animals can mainly be divided into two main groups: the invertebrates and the vertebrates. Vertebrates have a backbone, or spine; invertebrates do not. Vertebrates are the only group to have an adaptive immune system, which may be partly responsible for their size and success. Vertebrates are: Fish (or 'fishes': both ways are correct) Amphibia Reptiles Birds Mammals Some invertebrates are: Insects Spiders Crustacea Molluscs (like a snail or squid) worms jellyfish

Life styles The animal mode of nutrition is called heterotrophic because they get their food from other living organisms. Some animals eat only plants; they are called herbivores. Other animals eat only meat and are called carnivores. Animals that eat both plants and meat are called omnivores. Some animals get their energy from photosynthetic protists that live inside them. The environments animals live in vary greatly. By the process of evolution, animals adapt to the habitats they live in. A fish is adapted to its life in water and a spider is adapted to a life catching and eating insects. A mammal living on the savannahs of East Africa lives quite a different life from a dolphin or porpoise catching fish in the sea.

The fossil record of animals goes back about 600 million years to the Ediacaran period, or somewhat earlier. During the whole of this long time, animals have been constantly evolving, so that the animals alive on Earth today are very different from those on the edges of the sea-floor in the Ediacaran. Everyday language In scientific usage, humans are animals. But in everyday use, humans are often not regarded as animals. Related pages List of animal phyla Ethology, the study of animal behaviour References Basic English 850 words

Acceleration is a measure of how fast velocity changes. Acceleration is the change of velocity divided by the change of time. Acceleration is a vector, and therefore includes both a size and a direction. Acceleration is also a change in speed and direction, there is: Speed (a scalar quantity) (uses no direction) Distance is how far you traveled Time is how long it took you to travel Speed is how fast you are moving - Speed = Distance / Time Velocity (a vector quantity) (uses a direction) Displacement is how much your position has changed in what direction Velocity is how quickly your position is changing and in what direction Velocity = Displacement / Time The measurement of how fast acceleration changes is called jerk.

Examples An object was moving north at 10 meters per second. The object speeds up and now is moving north at 17 meters per second. The object has accelerated. An apple is falling down. It starts falling at 0 meters per second. At the end of the first second, the apple is moving at 9.8 meters per second. The apple has accelerated. At the end of the second second, the apple is moving down at 19.6 meters per second. The apple has accelerated again. Jane is walking east at 3 kilometers per hour. Jane's velocity does not change. Jane's acceleration is zero. Tom was walking east at 3 kilometers per hour. Tom turns and walks south at 3 kilometers per hour. Tom has had a nonzero acceleration. Sally was walking east at 3 kilometers per hour. Sally slows down. After, Sally walks east at 1.5 kilometers per hour. Sally has had a nonzero acceleration. Acceleration due to gravity Finding acceleration Acceleration is the rate of change of the velocity of an object. Acceleration can be found by using:

where is the velocity at the start is the velocity at the end is the time at the start is the time at the end Sometimes the change in velocity is written as Δ. Sometimes the change in time is written as Δt. In difficult situations, the acceleration can be calculated using mathematics: in calculus, acceleration is the derivative of the velocity (with respect to time), . Units of measurement Acceleration has its own units of measurement. For example, if velocity is measured in meters per second, and if time is measured in seconds, then acceleration is measured in meters per second squared (m/s2). Other words Acceleration can be positive or negative. When the acceleration is negative (but the velocity does not change direction), it is sometimes called deceleration. For example, when a car brakes it decelerates. Physicists usually only use the word "acceleration".

Newton's second law of motion Newton's laws of motion are rules for how things move. These rules are called "laws of motion". Isaac Newton is the scientist who first wrote down the main laws of motion. According to Newton's Second Law of Motion, the force something needs to accelerate an object depends on the object's mass (the amount of "stuff" the object is made from or how "heavy" it is). The formula of Newton's Second Law of Motion is , where is the acceleration, is the force, and the mass. This formula is very well-known, and it is very important in physics. Newton's Second Law of Motion, in short "Newton's Second Law", is often one of the first things that physics students learn. Deceleration Deceleration is negative or backwards acceleration. This means that something slows down instead of speeding up. For example, when a car brakes, it is decelerating. Basic physics ideas Mechanics

Black pudding is an English name for zwarte pudding. It is food made by cooking down the blood of any mammal (usually pigs or cattle) with meat, fat or filler until it is thick enough to congeal (become firm or solid) when cooled. Types of black pudding In Great Britain, blood sausage is called "black pudding". The ingredients include pig's blood, suet, bread, barley and oatmeal. Bury is well known for them. The most common kind of German Blutwurst is made from fatty pork meat, beef blood and filler such as barley. Though already cooked and "ready to eat" it is usually served warm. Other kinds of blood sausage include boudin noir (France), boudin rouge (Creole and Cajun) and morcilla (Spain).

History A legend says that blood sausage was invented in a bet between two Bavarian butchers drunk on the alcoholic drink absinthe during the 14th century. Homer's Odyssey from Ancient Greece says that "As when a man besides a great fire has filled a sausage with fat and blood and turns it this way and that and is very eager to get it quickly roasted...". Related pages Sausage References Sausage

A boot device is used to start a computer. It is named after a boot which fits on the foot. The word bootstrap is also closely related, and means, to use something simpler to get something more complex to make itself work better. It comes from the English phrase "pull yourself up by your own bootstraps." Before a computer can operate normally, it must have operating system instructions that tell it how to perform basic functions. A boot device loads the operating system into the memory of the computer.

Devices that can boot a computer are usually boot disks or boot drives (normally a hard drive or Solid State Drive, but can be a floppy disk, flash drive or a CD). Some network computers use boot chips that get the operating system over a network. Web phones also use such chips to identify the user to the mobile phone network. Boot card standards may let many users boot kiosk computers with full privacy and access to all application software they own. There are also boot boards or boot add-in cards that are more permanent than boot cards. Some people refer to the boot device as just a boot and non-boot devices as data devices, although it is not the computer but the operating system that cares about the difference between these. Origin The boot in boot device is the same as booting (or starting up). This is short for bootstrapping, or to start with simple stuff and make complex stuff out of it. Related pages Booting software Computer hardware