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Self government The gold rushes of New South Wales and Victoria started in 1851 leading to large numbers of people arriving to search for gold. The population grew across south east Australia and made great wealth and industry. By 1853 the gold rushes had made some poor people very rich.

The transportation of convicts to Australia ended in the 1840s and 1850s and more changes came. The people in Australia wanted to run their own country, and not be told what to do from London. The first governments in the colonies were run by governors chosen by London. Soon the settlers wanted local government and more democracy. William Wentworth started the Australian Patriotic Association (Australia's first political party) in 1835 to demand democratic government. In 1840, the city councils started and some people could vote. New South Wales Legislative Council had its first elections in 1843, again with some limits on who could vote. In 1855, limited self-government was given by London to New South Wales, Victoria, South Australia and Tasmania. In 1855, the right to vote was given to all men over 21 in South Australia. The other colonies soon followed. Women were given the vote in the Parliament of South Australia in 1895 and they became the first women in the world allowed to stand in elections.

Australians had started parliamentary democracies all across the continent. But voices were getting louder for all of them to come together as one country with a national parliament. The Commonwealth of Australia Until 1901, Australia was not a nation, it was six separate colonies governed by Britain. They voted to join to form one new country, called the Commonwealth of Australia, in 1901. Australia was still part of the British Empire, and at first wanted only British or Europeans to come to Australia. But soon it had its own money, its own Army and its own Navy. In Australia at this time, the trade unions were very strong, and they started a political party, the Australian Labor Party. Australia passed many laws to help the workers.

In 1914, the First World War started in Europe. Australia joined in on the side of Britain against Germany, Austria-Hungary and the Ottoman Empire. Australian soldiers were sent to Gallipoli, in the Ottoman Empire. They fought bravely, but were beaten by the Turks. Today Australia remembers this battle every year on ANZAC Day. They also fought on the Western Front. More than 60,000 Australians and New Zealanders were killed. In 1932, the Sydney Harbour Bridge was opened. Australia had a really hard time in the Great Depression of the 1930s and joined Britain in a war against Nazi Germany when Hitler invaded Poland in 1939. But in 1941 lots of Australian soldiers were captured in the Fall of Singapore by Japan. Then Japan started attacking Australia and people worried about invasion. But with help from the United States Navy, the Japanese were stopped. After the war, Australia became a close friend of the United States and Japan.

When the war ended, Australia felt that it needed many more people to fill the country up and to work. So the government said it would take in people from Europe who had lost their homes in the war. It did things like building the Snowy Mountains Scheme. Over the next 25 years, millions of people came to Australia. They came especially from Italy and Greece, other countries in Europe. Later they also came from countries like Turkey and Lebanon. An important new party, the Liberal Party of Australia was made by Robert Menzies in 1944 and it won lots of elections from 1949 until in 1972, then Gough Whitlam won for the Labor Party. Whitlam made changes, but he made the Senate unhappy and the Governor-General sacked him and forced an election in 1975. Then Malcolm Fraser won a few elections for the Liberal Party.

In the 1960s many people began coming to Australia from China, Vietnam, Malaysia and other countries in Asia. Australia became more multicultural. In the 1950s and 1960s Australia became one of the richest countries in the world, helped by mining and wool. Australia started trading more with America, than Japan. Australia supported the United States in wars against dictatorships in Korea and Vietnam and later Iraq. Australian soldiers also helped the United Nations in countries like East Timor in 1999. In 1973, the famous Sydney Opera House opened. In the 1970s, 80s and 90s lots of Australian movies, actors and singers became famous around the world. In the year 2000, Sydney had the Summer Olympics. In the 1980s and 90s, the Labor Party under Bob Hawke and Paul Keating, then the Liberal Party under John Howard made lots of changes to the economy. Australia had a bad recession in 1991, but when other Western countries had trouble with their economies in 2008, Australia stayed strong.

Today Australia is a rich, peaceful and democratic country. But it still has problems. Around 4-5% of Australians could not get a job in 2010. A lot of land in Australia (like Uluru) has been returned to Aboriginal people, but lots of Aboriginals are still poorer than everybody else. Every year the government chooses a big number of new people from all around the world to come as immigrants to live in Australia. These people may come because they want to do business, or to live in a democracy, to join their family, or because they are refugees. Australia took 6.5 million immigrants in the 60 years after World War Two, including around 660,000 refugees. Julia Gillard became the first woman Prime Minister of Australia in 2010 when she replaced her Labor Party colleague Kevin Rudd (who later replaced her). Politics

Politics Australia is part of the Commonwealth of Nations. Australia is made up of six states, and two mainland territories. Each state and territory has its own Parliament and makes its own local laws. The Parliament of Australia sits in Canberra and makes laws for the whole country, also known as the Commonwealth or Federation. The Federal government is led by the Prime Minister of Australia, who is the member of Parliament chosen as leader. The current Prime Minister is Anthony Albanese. The leader of Australia is the Prime Minister, although the Governor-General represents the Queen of Australia, who is also the Queen of Great Britain, as head of state. The Governor-General, currently His Excellency David Hurley, is chosen by the Prime Minister. Culture

Culture Australia was colonised by people from Britain, but today people from all over the world live there. English is the main spoken language. Christianity is the main religion, though all religions are accepted and not everybody has a religion. Australia is multicultural: all its people are encouraged to keep their different languages, religions and ways of life, while also learning English and joining in with other Australians. Australia has many immigrants from different countries around the world. Famous Australian writers include the bush balladeers Banjo Paterson and Henry Lawson who wrote about life in the Australian bush. More modern famous writers include Peter Carey, Thomas Keneally and Colleen McCullough. In 1973, Patrick White won the Nobel Prize in Literature, the only Australian to have achieved this; he is seen as one of the great English-language writers of the twentieth century.

Australian music has had world-wide stars, for example the opera singers Nellie Melba and Joan Sutherland, the rock and roll bands Bee Gees, AC/DC and INXS, the folk-rocker Paul Kelly (musician), the pop singer Kylie Minogue and Australian country music stars Slim Dusty and John Williamson. Australian Aboriginal music is very special and very ancient: it has the famous didgeridoo woodwind instrument. Australian TV has produced many successful programs for home and overseas. Skippy the Bush Kangaroo, Home and Away and Neighbours are examples. It has had well known TV stars, such as Barry Humphries (Dame Edna Everage), Steve Irwin (The Crocodile Hunter) and The Wiggles. Major Australian subgroups such as the Bogan have been shown on Australian TV in shows such as Bogan Hunters and Kath & Kim.

Australia has two public broadcasters (the ABC and the multicultural SBS), three commercial television networks, three pay-TV services, and numerous public, non-profit television and radio stations. Each major city has its daily newspapers, and there are two national daily newspapers, The Australian and The Australian Financial Review.

Australian movies have a long history. The world's first feature movie was the Australian movie The Story of the Kelly Gang of 1906. In 1933, In the Wake of the Bounty, directed by Charles Chauvel, had Errol Flynn as the main actor. Flynn went on to a celebrated career in Hollywood. The first Australian Oscar was won by the 1942 Kokoda Front Line!, directed by Ken G. Hall. In the 1970s and 1980s Australian movies and movie stars became world famous. There were movies like Picnic at Hanging Rock, Gallipoli (with Mel Gibson), The Man From Snowy River and Crocodile Dundee. Russell Crowe, Cate Blanchett and Heath Ledger became global stars during the 1990s and Australia starring Nicole Kidman and Hugh Jackman made a lot of money in 2008. Australia is a popular destination for business conferences and research, with Sydney one of the top 20 meeting destinations in the world. Sport

Sport is an important part of Australian culture because the climate is good for outdoor activities. 23.5% Australians over the age of 15 regularly take part in organised sporting activities. The most popular sports are Australian rules football, rugby league and cricket. In international sports, Australia has very strong teams in cricket, hockey, netball, rugby league and rugby union, and performs well in cycling, rowing and swimming. Local popular sports include Australian Rules Football, horse racing, soccer and motor racing. Australia has participated in every summer Olympic Games since 1896, and every Commonwealth Games. Australia has hosted the 1956 and 2000 Summer Olympics, and has ranked in the top five medal-winners since 2000. Australia has also hosted the 1938, 1962, 1982 and 2006 Commonwealth Games and are to host the 2018 Commonwealth Games

. Other major international events held regularly in Australia include the Australian Open, one of the four Grand Slam tennis tournaments, annual international cricket matches and the Formula One Australian Grand Prix. Corporate and government sponsorship of many sports and elite athletes is common in Australia. Televised sport is popular; some of the highest-rated television programs include the Summer Olympic Games and the grand finals of local and international football competitions.

The main sporting leagues for men are the AFL (Australian rules football), the NRL (rugby league), the A-League (soccer) and the NBL (basketball). For women, they are the AFLW (Australian rules football), ANZ Netball Championships (netball), the W-League (soccer) and WNBL (basketball). Famous Australian sports players include the cricketer Sir Donald Bradman, the swimmer Ian Thorpe, the cricketer Shane Warne and the athlete Cathy Freeman. Art festivals Just 60 years ago, Australia had only one big art festival. Now Australia has hundreds of smaller community-based festivals, and national and regional festivals that focus on specific art forms. Indigenous life Australia is home to many animals and plants that can be found nowhere else on Earth, except perhaps New Guinea. The platypus and the short-beaked echidna are unique, and are two of the only five surviving monotremes. Monotremes are only found in Australia and New Guinea.

Koalas, kangaroos, wombats, numbats and many others others, are marsupials. Most of the marsupials in the world are found only on the continent or on the neighbouring island of New Guinea. Wildfires from global warming in 2020 have reduced their population. Trees The gum trees are almost as remarkable as the animals. They are mainly Eucalypts and other gum trees. These are woody evergeens which make essential oils and are prone to fire. Sticky heavily scented gum squeezes out of their wood. The tribe has about 860 species. They are all native to Southeast Asia and Oceania. Most live in Australia. Until British settlement in Australia, these trees were almost entirely unknown. They had been separated from the Americas, Africa and much of Asia for millions of years. References Notes References Other websites Official website for australia travel Official website for Australia travel. Australia travel informations User generated guide to Australia.

Australasia Commonwealth realms English-speaking countries Federations 1901 establishments

American English or US English is the dialect of the English language spoken in the United States of America. It is different in some ways from other types of English, such as British English. Most types of American English came from local dialects in England. During the 18th and 19th centuries, pronunciation changed less in America than in England. Use Many people today know about American English even if they live in a country where another type of English is spoken. They hear and read American English through the media, for example movies, television, and the Internet, where the most common form of English is American English. Because people all over the world use the English language, it gets many new words. English has been changing in this way for hundreds of years. For example, the many millions who speak Indian English frequently add American English words to go along with its British English base and many other words from the various Indian languages.

Sometimes people learn American English as it is spoken in the US. For example, in telephone call centers in India and other places, people often learn American English to sound more like their customers who call from the US. These people often keep using American English in everyday life. Spelling There are many words that sound the same in both American and British English but have different spellings. British English often keeps more traditional ways of spelling words than American English.

Vocabulary There are also some words in American English that are a bit different from British English, e.g.: aeroplane is called "airplane" ladybird is called "ladybug" lift is called "elevator" toilet is called "bathroom", "restroom" or "comfort station" lorry is called "truck" nappies are called "diapers" petrol is called "gas" (or "gasoline") the boot of a car is called a "trunk" a dummy is called a "pacifier" trousers are called "pants" underground is called "subway" football is called "soccer" braces are "suspenders" ("suspenders" in British-English are a type of clothing worn around the lower leg to stop socks/sox from sagging, or around the upper leg by people wearing stockings)

Regional accents General American English is the kind most spoken in mass media. It more vigorously pronounces the letter "R" than some other kinds do. "R-dropping" is frequent in certain places where "r" sound is not pronounced after a vowel. For example as in the words "car" and "card" sounding like "cah" and "cahd". This occurs in the Boston area. Some regional accents of American English include Appalachian English - This is the stereotypical hillbilly accent. This accent is completely rhotic and can even have phantom Rs (in words they don't belong) General Southern - This is a range of accents which tend to be rhotic or semi-rhotic, have glide deletion (in which I is converted to broad A) Tidewater English - A non-rhotic (r-dropping) southern variety that also has a "Scottish" or "Canadian" raising of the "ow" diphthong in words like "house" "about" "brown", etc. Charleston and Savannah English - Almost extinct accents that are non-rhotic

Boston English (also east New England English) - This is the most famous non-rhotic American accent and what most other non-rhotic American varieties often get compared to. Other Bostonian features include limited Canadian raising of the "ow" diphthong (before voiceless consonants such as in words like "house" and "about"). New York City English - One of the most recognizable dialects in the US, NYC English is characterized by variable non-rhoticity or semi-rhoticity, a rounding of the long o sound ( making " coffee" and "thought" sound like "cawfee" and "thawt"). South Louisiana English - This group of non-rhotic accents can be heard in New Orleans and its surrounding areas and can be described as a combination between New York City English and Southern American English. Northern Midwest English - The accents of this area tend to sound a lot like Canadian English.

Valley girl and surfer dude - This accent is common to southern California and has features like " vocal fry" (creaky voice), and "upturn" at the ends of sentences. References Other websites American English -Citizendium

Aquaculture is the farming of fish, shrimp, abalones, algae, and other seafood. Aquaculture supplies fish, such as catfish, salmon, and trout. It was developed a few thousand years ago in China. Aquaculture supplies over 20% of all the seafood harvested. Fish farming has been practiced, in some parts of the world, for thousands of years. Goldfish originated about a thousand years ago in carp farms in China, and the Roman Empire farmed oysters and other seafood. Today, half of the seafood eaten in the U.S. is farmed. To help meet the growing global demand for seafood, aquaculture is growing fast. The environmental impact of fish farming varies widely, depending on the species being farmed, the methods used and where the farm is located. When good practices are used, it's possible to farm seafood in a way that has very little impact to the environment. Such operations limit habitat damage, disease, escapes of farmed fish and the use of wild fish as feed. References Aquaculture

An abbreviation is a shorter way to write a word or phrase. People use abbreviations for words that they write a lot. The English language occasionally uses the apostrophe mark ' to show that a word is written in a shorter way, but some abbreviations do not use this mark. More often, they use periods, especially the ones that come from the Latin language. Common Latin abbreviations include i.e. [id est] that is, e.g. [exempli gratia] for example, and et al. [et alia] and others. Some new abbreviations have been created by scientists, by workers in companies and governments, and by people using the Internet. People often think words are abbreviations when in fact they are acronyms.

Here are examples of common acronyms: The word "radar" is an acronym for "Radio Detection and Ranging". The name of the large computer company IBM comes from the words "International Business Machines". The name of the part of the United States government that sends rockets into outer space is NASA, from the words "National Aeronautics and Space Administration". When people using the Internet think that something is very funny, they sometimes write "LOL" to mean "Laughing Out Loud". People sometimes write "ASAP" for "As Soon As Possible". Other websites Acronym Finder - largest acronym site with many ways to search for acronyms and abbreviations in many languages. Over 10-year history. All Acronyms - a website with a large number of abbreviations and acronyms Acronyms Abbreviations and Slang - over 3 million different acronyms and abbreviations in searchable database SlangLang Abbreviations - Slang Words: 2,700 abbreviations and their meanings Linguistics

In many mythologies and religions, an angel is a good spirit. The word angel comes from the Greek word angelos which means "messenger". Angels appear frequently in the Old Testament, the New Testament, Qur'an and Aqdas. Different references to angels throughout the Bible suggest different kinds and ranks of angels, such as seraphs (Hebrew plural: seraphim) or cherubs (Hebrew plural: cherubim). This resulted in medieval theologians outlining a hierarchy of such divine messengers, including not only cherubs and seraphs, but also archangels, powers, principalities, dominions and thrones. The study of angels is called angelology.

In the Bible Angels are powerful spirits that obey God's commands. They sometimes appear to humans in a human form. They can deliver messages to people in person or in dreams. Angels that are named in the Bible are Michael (called a "chief prince"), Gabriel (known for telling Mary that she would be the mother of Jesus), and Raphael (in the Apocryphal Book of Tobit). The Ethiopian Book of Enoch also lists four Archangels which watch over the four quadrants of heaven; Michael, Raphael, Gabriel and Uriel. Lucifer is also known as an angel in the Bible. Types Cherubs are described as creatures which have four wings. Cherubim guard the Eden with a sword of fire. This suggests that the author of Genesis was aware of different types of angels. A Cherub is mentioned in Ezekiel 28:13-14, saying that the angel was in the Garden of God.

Ezekiel 28:13-14 13. Thou hast been in Eden the garden of God; every precious stone was thy covering, the sardius, topaz, and the diamond, the beryl, the onyx, and the jasper, the sapphire, the emerald, and the carbuncle and gold: the workmanship of thy tabrets and of thy pipes was prepared in thee in the day that thou wast created. 14. Thou art the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire. It describes the sound of their wings, "like the roar of rushing waters." Ezekiel 10:5-7 ; Ezekiel 10:8 reveals that they have hands like a man under their wings . Ezekiel 1:7 KJV reveals that they look like man but are different because they have "straight feet" and four wings and four faces. Ezekiel ch 1, and 10 describe the cherubim creatures ascending and descending from the earth with wheels. Ezekiel 1:14-20 ; Ezekiel 10:16

Ezekiel 10:9-13 describes what the wheels appeared to look like, and how they moved around, how they moved or flew through the sky quickly but turned not as they went; and how the inside workings of the wheels appeared to be "a wheel in the midst of a wheel" and that the color of the wheels was the color of "Amber" Stone. There are four separate wheels in both accounts, one for each single cherub which is there. Seraphs (Hebrew for "burning") are depicted as having six wings They are known for singing and praising God. They can shout so loud, they shake the temple. Archangels like Gabriel (Gospel of Luke 1:19) are the highest type of angel. They are considered saints in the Catholic church. However, in the King James Version of the Bible; they are another type of angel. In the Book of Revelation the Angel Michael casts the 'great dragon' Satan out of heaven and down to earth in a great battle between the good and bad angels, just before the Great Judgement of angels and man. (Revelation 12)

The Leviathan in Book of Job 41:19-21 has flame that goes: 'out of his mouth' like a dragon. Isaiah 30:6 also talks of a 'fiery flying serpent'. Compare Revelation 20:2: , where an angel: 'laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years'.

Religion Rabbinic Judaism In Judaism angels are created by God from fire. They fullfil tasks given by God. Rabbinic Judaism rejects earlier accounts on fallen angels who sinned by mating with humans. Instead, angels are servants of God. Still, not all angels are benevolent. Some angels are jealous of humans, because God loves them so much. Unlike angels, humans can overcome sin and repent. Angels cannot repent their sin, because they are already sinless. When the Bible speaks about the creation of humans in the plural, Judaism sometimes argues that God discussed his decision with the angels. But they make clear, it is God alone who creates humans. God only wanted to discuss with the angels to show that someone in power, should still try to value the opinion of people lower.

Islam

In Islam angels are created by God (Allah) before jinn and humans. Angels live in heaven and fullfil God's orders. Some angels deliver messages to humans and prophets, most famous among them is Gabriel. Other angels support humans with rain. Some angels don't have a task on earth, but dwell in heaven, for example, to praise God. Muslims disagree if angels can fail a task, but they agree that an angel never want to disobey. Sometimes angels might simply make mistakes on accident, like the angels Harut and Marut. But these angels are not considered evil, they just lose their rank as punishment, but can restore their rank later again. Not all angels are nice. God gives angels violent tasks too. For example, God orders angels to punish people in hell, not demons. Muslims believe hell is under God's control, and not the demon's. They believe hell is not only suffering, but also justice. Angels watch out that people don't escape their punishment

. While the benevolent angels are said to be created from light, some Muslims think the angels in hell are created from fire.

In art They are often shown in art as having wings and a halo. The wings represent their speed, and the halo represents their holiness. The cherubim in art always appear as baby faced angels with very small, non-useful wings. The cherubim statue or bronze casting of cherubim in the Temple of Solomon depicted them as two four winged creatures whose wings touched at the peak of the ark that they were making. The same cherubim creatures were said to be cast in gold on top of the Ark of the Covenant. Casting metal is one of the oldest forms of artwork, and was attempted by Leonardo da Vinci.

In literature Angels are generally held to be holy and virtuous, hence the term is used loosely to apply to anyone particularly good or kind, or having a good influence. In his novel Far From the Madding Crowd, Thomas Hardy chooses the name of an angel, Gabriel, for his kind and helpful hero. On the other hand, in his play Measure for Measure, Shakespeare's use of the name Angelo is ironic, since Angelo is a character who likes to see himself as virtuous, but who is concealing evil aspects of his nature. Fallen angels, who are no longer holy or virtuous, are also known as devils.

However, since angels are held to be spirits (that is, non-material beings), medieval theologians were faced with the problem of how humans could see a non-physical creature. Eventually a theory was put forward that angels must make themselves a body out of the nearest thing to the non-physical, i.e. from air. Hence in his famous poem Aire and Angels, the seventeenth century metaphysical poet John Donne uses this idea to write a cynical comment on women, whose love, he says, is like an angel's body of air, while men's love is like the real thing, the angel itself. Idea of Guardian angel From the era of the Romantics onwards, there has developed the widely held belief that everyone has an angel assigned to guard them. This concept is probably based on Jesus' comment in Matthew 18:10 regarding children, though it is not mentioned elsewhere in the Bible.

In superstitions Seeing repetitive numbers are thought to be associated with numerology, also referred to as angel numbers. It is believed that angels communicate with humans through repetitive appearances of numbers. Humanity has studied and used numbers since the dawn of time, and no matter what the culture is, there are certain numbers that hold specific value or meaning over other numbers. References Related pages Demigod Other websites

Ad hominem is a Latin word for a type of argument. It is a word often used in rhetoric. Rhetoric is the science of speaking well, and convincing other people of your ideas. Translated to English, ad hominem means against the person. In other words, when someone makes an ad hominem, they are attacking the person they are arguing against, instead of what they are saying. The term comes from the Latin word homo, which means human. Hominem is a gender neutral version of the word homo. In ancient Rome it referred to all free men, or in other words, all free human beings. Ad hominem can be a way to use reputation, rumors and hearsay to change the minds of other people listening. When a social network has already excluded or exiled one person, or applied a negative label to them, this can work more often. It is most of the time considered to be a weak and poor argument. In courts and in diplomacy ad hominems are not appreciated.

Ad hominems are not wrong every time. For example, when people think that someone can't be trusted, things that they have said previously can be doubted. What an ad hominem argument looks like In logic, a proof is something that starts with premises, and goes through a few logical arguments, to reach a conclusion. Normal (valid) proof All humans are mortal. Socrates is human. Therefore, Socrates is mortal. Ad hominem example Person A thinks abortion should be illegal. Person A is uneducated and poor. Therefore, abortion should not be illegal. In this example it can be seen that the (completely unrelated) fact that person A is uneducated and poor is used to prove that abortion should not be illegal. Related pages Fallacy for a list of other types of (false) rhetorical arguments. Latin words used in English

Native Americans (also called Aboriginal Americans, American Indians, Amerindians or indigenous peoples of the Americas) are the indigenous peoples and their descendants, who were in the Americas before Europeans arrived. Sometimes these people are called Indians, but this may be confusing, because it is the same word used for people from India. When Christopher Columbus explored, he did not know about the Americas. He was in the Caribbean but thought he was in the East Indies, so he called the people Indians. Today, some think that calling a Native American an Indian is racist. There are many different tribes of Native American people, with many different languages. Some tribes were hunter-gatherers who moved from place to place. Others lived in one place and built cities and kingdoms.

Many Native Americans died after the Europeans came to the Americas. There were diseases that came with the Europeans but were new to the Native Americans. There were battles with the Europeans. Many native people were hurt, killed, or forced to leave their homes by settlers who took their lands. Today, there are more than three million Native Americans in Canada and the U.S. combined. About 51 million more Native Americans live in Latin America. Many Native Americans still speak native languages and have their own cultural practices, while others have adopted some parts of Western culture. Many Native Americans face problems with discrimination and racism. Origins The ancestors of Native Americans came to the Americas from Asia. Some of them may have come to America 15,000 years ago when Alaska was connected to Siberia by the Bering land bridge.

The earliest people in the Americas came from Siberia when there was an ice bridge across the Bering Strait. The cold but mainly grassy plain which connected Siberia with Canada is called Beringia. It is reckoned that a few thousand people arrived in Beringia from eastern Siberia during the Last Glacial Maximum before moving into the Americas sometime after 16,500 years before the present (BP). This would have occurred as the American glaciers blocking the way southward melted, but before the bridge was covered by the sea about 11,000 years BP.

Before European colonization, Beringia was inhabited by the Yupik peoples on both sides of the straits. This culture remains in the region today, with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia. Native Americans are divided into many small nations, called First Nations in Canada and tribes elsewhere. Culture Each Native American tribe has their own culture. The cultures can be grouped together depending on region. For example, the tribes living in Mesoamerica have similar cultures. Food Native Americans ate many different things depending on where they lived. Native Americans from Mesoamerica introduced vanilla, avocados, and chocolate to the world.

Religion Before Europeans came, the native peoples of the Americans practiced many different religions. Each tribe had their own different beliefs. Today, many Native Americans practice Christianity, a religion that was brought to the Americas by Europeans. Meanwhile, others still practice their own religions. Languages Native Americans today speak over a thousand different languages. Some of these languages had writing systems before Europeans came. Many of these languages are endangered because more people are speaking European languages and not teaching Native American languages to their kids. Music Native Americans make musical instruments using the things around them. Art Native Americans made a lot of different art. Today North America

North America United States According to the 2010 United States census, 0.9% of Americans say they are Native American, 2.9 million people, and 0.8% of Americans say they are both Native American and something else. They are not evenly spread out through the United States. About a third of the people in Alaska are Native Alaskan and about a sixth of the people in Oklahoma are Native American. In the United States, most Native Americans live in cities. About 28% of Native Americans live on Indian reservations. Many Native Americans are poor, and 24% are extremely poor. The history of violence against Native Americans persists today in higher rates of violence against Native American people than white people. Mexico Many Mexicans are of Native American or mestizo ancestry. Mexico has the largest and most diverse Native American population in Latin America. Canada In the 2016 census, More than 1.67 million people in Canada identified as Indigenous, making them 4.9 per cent of Canada’s population.

Central America Guatemala About 40% of the people of Guatemala identify as Native American. Many indigenous groups in the country are descendants of the Maya. Many Native Americans in Guatemala are poor. Many of them have left the country to find better jobs elsewhere. South America Bolivia The majority of Bolivians belong to indigenous groups. Many are Aymara and Quechua. Peru Peru has a large indigenous population, around 80% of Peru's population identify as indigenous or mestizo. Indigenous activism In the later half of the 20th century, many Native Americans started to protest the unfair treatment they experienced from the societies they lived in. Some Native Americans have become famous in politics. For example, an Aymara man named Evo Morales was elected as president of Bolivia in 2005. He was the first indigenous presidential candidate in Bolivia and South America. Related pages First Nations Plains Indians Native Americans in the United States References

An apple is the edible fruit of a number of trees, known for its juicy, green, or red fruits. The tree (Malus spp.) is grown worldwide. Its fruit is low-cost, popular, and common all over the earth. Applewood is a type of wood that comes from this tree. The apple tree comes from southern Kazakhstan, Kyrgyzstan, Uzbekistan, and northwestern part of China. Apples have been grown for thousands of years in Asia and Europe. They were brought to North America by European settlers. Apples have religious and mythological significance in many cultures. Apples are generally grown by grafting, although wild apples grow readily from seed. Apple trees are large if grown from seed, but small if grafted onto roots (rootstock). There are more than 10000 known variants of apples, with a range of desired characteristics. Different variants are bred for various tastes and uses: cooking, eating raw and cider production are the most common uses.

Trees and fruit are attacked by fungi, bacteria and pests. In 2010, the fruit's genome was sequenced as part of research on disease control and selective breeding in apple production. Worldwide production of apples in 2013 was 90.8 million tonnes. China grew 49% of the total. Botanical information The apple has a small, leaf-shedding tree that grows up to tall. The apple tree has a broad crown with thick twigs. The leaves are alternately arranged simple ovals. They are 5 to 12 centimetres long and 3–6 centimetres (1.2–2.4 in) wide. It has a sharp top with a soft underside. Blossoms come out in spring at the same time that the leaves begin to bud. The flowers are white. They also have a slightly pink color. They are five petaled, and 2.5 to 3.5 centimetres (0.98 to 1.4 in) in diameter. The fruit matures in autumn. It is usually 5 to 9 centimetres (2.0 to 3.5 in) in diameter. There are five carpels arranged in a star in the middle of the fruit. Every carpel has one to three seeds.

Wild ancestors The wild ancestor of apple trees is Malus sieversii. They grow wild in the mountains of Central Asia in the north of Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China, and possibly also Malus sylvestris. Unlike domesticated apples, their leaves become red in autumn. They are being used recently to develop Malus domestica to grow in colder climates. History The apple tree was possibly the earliest tree to be cultivated. Its fruits have become better over thousands of years. It is said that Alexander the Great discovered dwarf apples in Asia Minor in 300 BC. Asia and Europe have used winter apples as an important food for thousands of years. From when Europeans arrived, Argentina and the United States have used apples as food as well. Apples were brought to North America in the 1600s. The first apple orchard on the North American continent was said to be near Boston in 1625. In the 1900s, costly fruit industries, where the apple was a very important species, began developing.

In culture Paganism In Norse mythology, the goddess Iðunn gives apples to the gods in Prose Edda (written in the 13th century by Snorri Sturluson) that makes them young forever. English scholar H. R. Ellis Davidson suggests that apples were related to religious practices in Germanic paganism. It was from there, she claims, that Norse paganism developed. She points out that buckets of apples were discovered in the place of burial for the Oseberg ship in Norway. She also remarks that fruit and nuts (Iðunn having been described as changing into a nut in Skáldskaparmál) have been discovered in the early graves of the Germanic peoples in England. They have also been discovered somewhere else on the continent of Europe. She suggests that this may have had a symbolic meaning. Nuts are still a symbol of fertility in Southwest England.

Cooking Sometimes apples are eaten after they are cooked. Often, apples are eaten uncooked. Apples can also be made into drinks. Apple juice and apple cider are drinks made with apples. The flesh of the fruit is firm with a taste anywhere from sour to sweet. Apples used for cooking are sour, and need to be cooked with sugar, while other apples are sweet, and do not need cooking. There are some seeds at the core, that can be removed with a tool that removes the core, or by carefully using a knife. The scientific name of the apple tree genus in the Latin language is Malus. Most apples that people grow are of the Malus domestica species. Most apples are good to eat raw (not cooked), and are also used in many kinds of baked foods, such as apple pie. Apples are cooked until they are soft to make apple sauce.

Apples are also made into the drinks apple juice and cider. Usually, cider contains a little alcohol, about as much as beer. The regions of Brittany in France and Cornwall in England are known for their apple ciders. Apple variants If one wants to grow a certain type of apple, it is not possible to do this by planting a seed from the wanted type. The seed will have DNA from the apple that the seeds came from, but it will also have DNA from the apple flower that pollinated the seeds, which might be a different variant of apple. This means that the tree which would grow from planting would be a mixture of two, or a hybrid. In order to grow a certain type of apple, a small twig, or 'scion', is cut from the tree that grows the type of apple desired, and then added on to a specially grown stump called a rootstock. The tree that grows will create apples of the type needed.

There are more than 7,500 known variants of apples. Different variants are available for temperate and subtropical climates. One large collection of over 2,100 apple variants is at the National Fruit Collection in England. Most of these variants are grown for eating fresh (dessert apples). However, some are grown simply for cooking or making cider. Cider apples are usually too tart to eat immediately. However, they give cider a rich flavor that dessert apples cannot. Most popular apple cultivars are soft but crisp. Colorful skin, easy shipping, disease resistance, 'Red Delicious' apple shape, and popular flavor are also needed. Modern apples are usually sweeter than older cultivars. This is because popular tastes in apples have become different. Most North Americans and Europeans enjoy sweet apples. Extremely sweet apples with hardly any acid taste are popular in Asia and India. World production

World production Apples are grown around the world. China produces more than half of all commercially grown apples. In 2020/2021, China produced 44,066,000 metric tons. Other important producers were the European Union (EU) (11,719,000 metric tons, the United States (4,490,000 metric tons), and Turkey (4,300,000 metric tons). Total world production was 80,522,000 metric tons. In the United Kingdom In the United Kingdom there are about 3000 different types of apples. The most common apple type grown in England is the 'Bramley seedling', which is a popular cooking apple. Apple orchards are not as common as they were in the early 1900s, when apples were rarely brought in from other countries. Organizations such as Common Ground teach people about the importance of rare and local varieties of fruit.

In North America Many apples are grown in temperate parts of the United States and Canada. "Washington State currently produces over half the Nation's domestically grown apples and has been the leading apple-growing State since the early 1920s." New York and Michigan are the next two leading states in apple production. "The total reported area dedicated to the crop in the United States is 336,940 acres or 526.47 square miles." In many areas where apple growing is important, people have huge celebrations: Annapolis Valley Apple Blossom Festival - held five days every spring (May-June) in Nova Scotia Shenandoah Apple Blossom Festival - held six days every spring in Winchester, Virginia. Washington State Apple Blossom Festival - held two weeks every spring (April-May) in Wenatchee, Washington. Varieties of apples There are many different varieties of apples, including:

Aport Cox's Orange Pippin Fuji (apple) Gala Golden Delicious (sometimes called a Green Delicious Apple) Granny Smith Jonathan Jonagold McIntosh Pink Lady Red Delicious Winesap Yellow Sweeting, the first variety of the U.S. Family Apples are in the group Maloideae. This is a subfamily of the family Rosaceae. They are in the same subfamily as pears. References Further reading Potter D. et al 2007. Phylogeny and classification of Rosaceae. Plant Systematics and Evolution. 266 (1–2): 5–43. Other websites Basic English 850 words National symbols of Poland

An Abrahamic Religion is a religion whose followers believe in the prophet Abraham. They believe Abraham and his sons/grandsons hold an important role in human spiritual development. The best known Abrahamic religions are Judaism, Christianity and Islam. Smaller religious traditions sometimes included as Abrahamic religions are Samaritanism, Druze, Rastafari, Babism and Bahá'í Faith. Mandaeism (a religion that holds many Abrahamic beliefs) is not called Abrahamic because its followers think Abraham was a false prophet True Abrahamic religions are monotheistic (the belief that there is only one God). They also all believe that people should pray to God and worship God often. Among monotheistic religions, the Abrahamic religions have the world's largest number of followers. Religions Mythology

Algebra (from Arabic: الجبر‎, transliterated "al-jabr", meaning "reunion of broken parts") is a part of mathematics. It uses variables to represent a value that is not yet known or can be replaced with any value. When an equals sign (=) is used, this is called an equation. A very simple equation using a variable is: . In this example, , or it could also be said that " equals five". This is called solving for . Besides equations, there are inequalities (less than and greater than). A special type of equation is called the function. This is often used in making graphs because it always turns one input into one output. Algebra can be used to solve real problems because the rules of algebra work in real life and numbers can be used to represent the values of real things. Physics, engineering and computer programming are areas that use algebra all the time. It is also useful to know in surveying, construction and business, especially accounting.

People who do algebra use the rules of numbers and mathematical operations used on numbers. The simplest are adding, subtracting, multiplying, and dividing. More advanced operations involve exponents, starting with squares and square roots. Algebra was first used to solve equations and inequalities. Two examples are linear equations (the equation of a straight line, or ) and quadratic equations, which has variables that are squared (multiplied by itself, for example: , , or ).

History Early forms of algebra were developed by the Babylonians and Greek geometers such as Hero of Alexandria. However the word "algebra" is a Latin form of the Arabic word Al-Jabr ("casting") and comes from a mathematics book Al-Maqala fi Hisab-al Jabr wa-al-Muqabilah, ("Essay on the Computation of Casting and Equation") written in the 9th century by a Persian mathematician, Muhammad ibn Mūsā al-Khwārizmī, who was a Muslim born in Khwarizm in Uzbekistan. He flourished under Al-Ma'moun in Baghdad, Iraq through 813-833 CE, and died around 840 CE. The book was brought into Europe and translated into Latin in the 12th century. The book was then given the name "Algebra". (The ending of the mathematician's name, al-Khwarizmi, was changed into a word easier to say in Latin, and became the English word algorithm). Examples Here is a simple example of an algebra problem:

Sue has 12 candies, and Ann has 24 candies. They decide to share so that they have the same number of candies. How many candies will each have? These are the steps you can use to solve the problem:

To have the same number of candies, Ann has to give some to Sue. Let represent the number of candies Ann gives to Sue. Sue's candies, plus , must be the same as Ann's candies minus . This is written as: Subtract 12 from both sides of the equation. This gives: . (What happens on one side of the equal sign must happen on the other side too, for the equation to still be true. So in this case when 12 was subtracted from both sides, there was a middle step of . After a person is comfortable with this, the middle step is not written down.) Add to both sides of the equation. This gives: Divide both sides of the equation by 2. This gives . The answer is six. This mean that if Ann gives Sue 6 candies, they will have the same number of candies. To check this, put 6 back into the original equation wherever was: This gives , which is true. They each now have 18 candies.

With practice, algebra can be used when faced with a problem that is too hard to solve any other way. Problems such as building a freeway, designing a cell phone, or finding the cure for a disease all require algebra. Writing algebra As in most parts of mathematics, adding to (or plus ) is written as ; subtracting from (or minus ) is written as ; and dividing by (or over ) is written as or . In algebra, multiplying by (or times ) can be written in 3 different ways: , or just . All of these notations mean the same thing: times . The symbol "" used in arithmetic is not used in algebra, because it looks too much like the letter , which is often used as a variable. When we multiply a number and a variable in algebra, we can simply write the number in front of the letter: . When the number is 1, then it is not written because 1 times any number is that number () and so it is not needed. And when it is 0, we can completely remove the terms, because 0 times any number is zero ().

As a side note, you do not have to use the letters or in algebra. Variables are just symbols that mean some unknown number or value, so you can use any letter for a variable (except (Euler's number) and (Imaginary unit), because these are mathematical constants). and are the most common, though. Functions and Graphs An important part of algebra is the study of functions, since they often appear in equations that we are trying to solve. A function is like a machine you can put a number (or numbers) into and get a certain number (or numbers) out. When using functions, graphs can be powerful tools in helping us to study the solutions to equations.

A graph is a picture that shows all the values of the variables that make the equation or inequality true. Usually this is easy to make when there are only one or two variables. The graph is often a line, and if the line does not bend or go straight up-and-down it can be described by the basic formula . The variable is the y-intercept of the graph (where the line crosses the vertical axis) and is the slope or steepness of the line. This formula applies to the coordinates of a graph, where each point on the line is written .

In some math problems like the equation for a line, there can be more than one variable ( and in this case). To find points on the line, one variable is changed. The variable that is changed is called the "independent" variable. Then the math is done to make a number. The number that is made is called the "dependent" variable. Most of the time the independent variable is written as and the dependent variable is written as , for example, in . This is often put on a graph, using an axis (going left and right) and a axis (going up and down). It can also be written in function form: . So in this example, we could put in 5 for and get . Put in 2 for would get . And 0 for would get . So there would be a line going through the points , , and as seen in the graph to the right. If has a power of 1, it is a straight line. If it is squared or some other power, it will be curved. If it uses an inequality ( or ), then usually part of the graph is shaded, either above or below the line.

Rules In algebra, there are a few rules that can be used for further understanding of equations. These are called the rules of algebra. While these rules may seem senseless or obvious, it is wise to understand that these properties do not hold throughout all branches of mathematics. Therefore, it will be useful to know how these axiomatic rules are declared, before taking them for granted. Before going on to the rules, reflect on two definitions that will be given. Opposite: the opposite of is . Reciprocal: the reciprocal of is . Commutative property of addition Commutative means that a function has the same result if the numbers are swapped around. In other words, the order of the terms in an equation does not matter. When two terms (addends) are being added, the commutative property of addition is applicable. In algebraic terms, this gives . Note that this does not apply for subtraction (i.e. except if ).

Commutative property of multiplication When two terms (factors) are being multiplied, the commutative property of multiplication is applicable. In algebraic terms, this gives . Note that this does not apply for division (i.e. , when and , except if ). Associative property of addition Associative refers to the grouping of numbers. The associative property of addition implies that, when adding three or more terms, it doesn't matter how these terms are grouped. Algebraically, this gives . Note that this does not hold for subtraction, e.g. (see distributive property). Associative property of multiplication The associative property of multiplication implies that, when multiplying three or more terms, it doesn't matter how these terms are grouped. Algebraically, this gives . Note that this does not hold for division, e.g. .

Distributive property The distributive property states that the multiplication of a term by another term can be distributed. For instance: . (Do not confuse this with the associative properties! For instance: .) Additive identity Identity refers to the property of a number that it is equal to itself. In other words, there exists an operation of two numbers so that it equals the variable of the sum. The additive identity property states that any number plus 0 is that number: . This also holds for subtraction: . Multiplicative identity The multiplicative identity property states that any number times 1 is that number: . This also holds for division: . Additive inverse property The additive inverse property is somewhat like the inverse of the additive identity. When we add a number and its opposite, the result is 0. Algebraically, it states the following: , which is the same as . For example, the additive inverse (or opposite) of 1 is -1.

Multiplicative inverse property The multiplicative inverse property means that when we multiply a number and its reciprocal, the result is 1. Algebraically, it states the following: , which is the same as . For example, the multiplicative inverse (or reciprocal) of 2 is 1/2. To get the reciprocal of a fraction, switch the numerator and the denominator: the reciprocal of is . Advanced Algebra In addition to "elementary algebra", or basic algebra, there are advanced forms of algebra, taught in colleges and universities, such as abstract algebra, linear algebra, and universal algebra. This includes how to use a matrix to solve many linear equations at once. Abstract algebra is the study of things that are found in equations, going beyond numbers to the more abstract with groups of numbers.

Many math problems are about physics and engineering. In many of these physics problems time is a variable. The letter used for time is . Using the basic ideas in algebra can help reduce a math problem to its simplest form making it easier to solve difficult problems. Energy is , force is , mass is , acceleration is and speed of light is sometimes . This is used in some famous equations, like and (although more complex math beyond algebra was needed to come up with that last equation). Related pages List of mathematics topics Order of operations Parabola Computer Algebra System References Other websites Khan Academy: Algebra theory and practice algebrarules.com: A free place to learn the basics of Algebra Khan Academy: Origins of Algebra, free online micro lectures Algebra

An atom is the basic unit of matter. All normal matter – everything that has mass – is made of atoms. This includes solids, liquids, and gases. The atom cannot be broken to parts by chemistry, so people once thought it was the smallest and simplest particle of matter. There are over 100 different kinds of atoms, called chemical elements. Each kind has the same basic structure, but a different number of parts. Atoms are very small, but their exact size depends on the type. Atoms are from 0.1 to 0.5 nanometers across. One nanometer is about 100,000 times smaller than the width of a human hair. This makes one atom impossible to see without special tools. Scientists learn how they work by doing experiments. Atoms are made of three kinds of subatomic particles. These are protons, neutrons, and electrons. Protons and neutrons have much more mass. They are in the middle of the atom, the nucleus. Lightweight electrons move quickly around them. The electromagnetic force holds the nucleus and electrons together.

Atoms with the same number of protons belong to the same chemical element. Examples of elements are carbon and gold. Atoms with the same number of protons, but different numbers of neutrons, are called isotopes. Usually an atom has the same number of electrons as protons. If an atom has more or less electrons than protons, it is called an ion, and has an electric charge. Atoms can join by chemical bonds. Many things are made of more than one kind of atom. These are chemical compounds or mixtures. A group of atoms connected by chemical bonds is called a molecule. For example, a water molecule is made of two hydrogen atoms and one oxygen atom. The forming or breaking of bonds is a chemical reaction.

Atoms split if the forces inside are too weak to hold them together. This is what causes radioactivity. Atoms can also join to make larger atoms at very high temperatures, such as inside a star. These changes are studied in nuclear physics. Most atoms on Earth are not radioactive. They are rarely made, destroyed, or changed into another kind of atom. History The word "atom" comes from the Greek (ἀτόμος) "atomos", which means indivisible or uncuttable. One of the first people to use the word "atom" is the Greek philosopher Democritus, around 400 BC. He thought that everything was made of particles called atoms, which could not be divided into smaller pieces. Some Hindu, Jain, and Buddhist philosophers also had ideas like this. Atomic theory was a mostly philosophical subject, with not much scientific investigation or study, until the early 1800s.

In 1777 French chemist Antoine Lavoisier defined the term element as we now use it. He said that an element was any substance that could not be broken down into other substances by the methods of chemistry. Any substance which could be broken down was a compound. In 1803, English philosopher John Dalton suggested that elements were made of tiny, solid balls called atoms. Dalton believed that all atoms of the same element have the same mass. He said that compounds are formed when atoms of more than one element combine. In any one compound, the atoms would always combine in the same numbers.

In 1827, British scientist Robert Brown looked at pollen grains in water under his microscope. The pollen grains appeared to be shaking. Brown used Dalton's atomic theory to describe patterns in how they moved. This was called Brownian motion. In 1905 Albert Einstein used mathematics to prove that the pollen particles were being moved by the motion, or heat, of individual water molecules. By doing this, he proved that atoms are real without question. In 1869, Russian scientist Dmitri Mendeleev published the first periodic table. The periodic table groups elements by their atomic number (how many protons they have; this is usually the same as the number of electrons). Elements in the same column, or group, usually have similar qualities. For example, helium, neon, argon, krypton, and xenon are all in the same column and are very similar. All these elements are gases that have no color or smell. Also, they cannot combine with other atoms to form compounds. Together they are known as noble gases.

The physicist J.J. Thomson was the first person to discover electrons. This happened while he was working with cathode rays in 1897. He learned they had a negative charge, and the rest of the atom had a positive charge. Thomson made the plum pudding model, which said that an atom was like plum pudding: the dried fruit (electrons) were stuck in a mass of pudding (having a positive charge). In 1909, Ernest Rutherford used the Geiger–Marsden experiment to prove that most of an atom is in a very small space, the atomic nucleus. Rutherford took a photo plate and covered it with gold foil. He then shot alpha particles (made of two protons and two neutrons stuck together) at it. Many of the particles went through the gold foil, which proved that atoms are mostly empty space. Electrons are so small and fast-moving that they did not block the particles from going through. Rutherford later discovered protons in the nucleus.

In 1913, Niels Bohr created the Bohr model. This model showed that electrons travel around the nucleus in fixed circular orbits. This was better than the Rutherford model, but it was still not completely true. In 1925, chemist Frederick Soddy discovered that some elements had more than one kind of atom, called isotopes. Soddy believed that each different isotope of an element has a different mass. To prove this, chemist Francis William Aston built the mass spectrometer, which measures the mass of single atoms. Aston proved that Soddy was right. He also found that the mass of each atom is a whole number times the mass of the proton. This meant that there must be some particles in the nucleus other than protons. In 1932, physicist James Chadwick shot alpha particles at beryllium atoms. He saw that a particle shot out of the beryllium atoms. This particle had no charge, but about the same mass as a proton. He named this particle the neutron.

The best model so far comes from the Schrödinger equation. Schrödinger learned that the electrons exist in a cloud around the nucleus, called the electron cloud. In the electron cloud, it is impossible to know exactly where electrons are. The Schrödinger equation says where an electron is likely to be. This area is called the electron's orbital. In 1937, German chemist Otto Hahn became the first person to make nuclear fission in a laboratory. He discovered this by chance when shooting neutrons at a uranium atom, hoping to make a new isotope. However, instead of a new isotope, the uranium changed into a barium atom, a smaller atom than uranium. Hahn had "broken" the uranium atom. This was the world's first recorded nuclear fission reaction. This discovery led to the creation of the atomic bomb and nuclear power, where fission happens over and over again, creating a chain reaction.

Later in the 20th century, physicists went deeper into the mysteries of the atom. Using particle accelerators, they discovered that protons and neutrons were made of other particles, called quarks. Structure and parts Parts An atom is made of three main particles: the proton, the neutron, and the electron. Protons and neutrons have nearly the same size and mass (about grams). The mass of an electron is about 1800 times smaller (about grams). Protons have a positive charge, electrons have a negative charge, and neutrons have no charge. Most atoms have no charge. The number of protons (positive) and electrons (negative) are the same, so the charges balance out to zero. However, ions have a different number of electrons than protons, so they have a positive or negative charge.

Scientists believe that electrons are elementary particles: they are not made of any smaller pieces. Protons and neutrons are made of quarks of two kinds: up quarks and down quarks. A proton is made of two up quarks and one down quark, and a neutron is made of two down quarks and one up quark. Nucleus The nucleus is in the middle of the atom. It is made of protons and neutrons. The nucleus makes up more than 99.9% of the mass of the atom. However, it is very small: about 1 femtometer (10−15 m) across, which is around 100,000 times smaller than the width of an atom, so it has a very high density.

Usually in nature, two things with the same charge repel or shoot away from each other. So for a long time, scientists did not know how the positively charged protons in the nucleus stayed together. We now believe that the attraction between protons and neutrons comes from the strong nuclear force. This force also holds together the quarks that make up the protons and neutrons. Particles called mesons travel back and forth between protons and neutrons, and carry the force.

The number of neutrons in relation to protons defines whether the nucleus stays together or goes through radioactive decay. When there are too many neutrons or protons, the atom tries to make the numbers smaller or more equal by removing the extra particles. It sends out radiation in the form of alpha, beta, or gamma decay. Nuclei can also change in other ways. Nuclear fission is when the nucleus breaks into two smaller nuclei, releasing a lot of energy. This release of energy makes nuclear fission useful for making bombs, and electricity in the form of nuclear power. The other way nuclei can change is through nuclear fusion, when two nuclei join or fuse to make a larger nucleus. This process requires very high amounts of energy to overcome the electric repulsion between the protons, as they have the same charge. Such high energies are most common in stars like our Sun, which fuses hydrogen for fuel. However, once fusion happens, far more energy is released, because some of the mass becomes energy.

The energy needed to break a nucleus into protons and neutrons is called its nuclear binding energy. This energy can be converted to mass, as stated by Einstein's famous formula E = mc2. Medium-sized nuclei, such as iron-56 and nickel-62, have the highest binding energy per proton or neutron. They will probably not go through fission or fusion, because they cannot release energy in this way. Very small and very large atoms have low binding energy, so they are most willing to go through fission or fusion. Electrons Electrons orbit, or travel around, the nucleus. They are called the atom's electron cloud. They are attracted to the nucleus because of the electromagnetic force. Electrons have a negative charge, and the nucleus always has a positive charge, so they attract each other.

The Bohr model shows that some electrons are farther from the nucleus than others in different levels. These are called electron shells. Only the electrons in the outer shell can make chemical bonds. The number of electrons in the outer shell determines whether the atom is stable or which atoms it will bond with in a chemical reaction. If an atom has only one shell, it needs two electrons to be complete. Otherwise, the outer shell needs eight electrons to be complete.

The Bohr model is important because it has the idea of energy levels. The electrons in each shell have a certain amount of energy. Shells that are farther from the nucleus have more energy. When a small burst of energy called a photon hits an electron, the electron can jump into a higher-energy shell. This photon must carry exactly the right amount of energy to bring the electron to the new energy level. A photon is a burst of light, and the amount of energy determines the color of light. So each kind of atom will absorb certain colors of light, called the absorption spectrum. An electron can also send out, or emit, a photon, and fall into a lower energy shell. For the same reason, the atom will only send out certain colors of light, called the emission spectrum.

The complete picture is more complicated. Unlike the Earth moving around the Sun, electrons do not move in a circle. We cannot know the exact place of an electron. We only know the probability, or chance, that it will be in any place. Each electron is part of an orbital, which describes where it is likely to be. No more than two electrons can be in one orbital; these two electrons have different spin.

For each shell, numbered 1, 2, 3, and so on, there may be a number of different orbitals. These have different shapes, or point in different directions. Each orbital can be described by its three quantum numbers. The principal quantum number is the electron shell number. The azimuthal quantum number is represented by a letter: s, p, d, or f. Depending on the principal and azimuthal quantum numbers, the electron can have more or less energy. There is also a magnetic quantum number, but it does not usually affect the energy level. As more electrons are added, they join orbitals in order from lowest to highest energy. This order starts as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d. For example, a chlorine atom has 17 electrons. So, it will have: 2 electrons in the 1s orbital 2 electrons in the 2s orbital 6 electrons in the 2p orbitals 2 electrons in the 3s orbital 5 electrons in the 3p orbitals In other words, it has 2 electrons in the first shell, 8 in the second shell, and 7 in the third shell.

Properties Atomic number The number of protons in an atom is called its atomic number. Atoms of the same element have the same atomic number. For example, all carbon atoms have six protons, so the atomic number of carbon is six. Today, 118 elements are known. Depending on how the number is counted, 90 to 94 elements exist naturally on earth. All elements above number 94 have only been made by humans. These elements are organized on the periodic table. Atomic mass and weight Because protons and neutrons have nearly the same mass, and the mass of electrons is very small, we can call the number of protons and neutrons in an atom its mass number. Most elements have several isotopes with different mass numbers. To name an isotope, we use the name of the element, followed by its mass number. So an atom with six protons and seven neutrons is called carbon-13.

Sometimes, we need a more exact measurement. The exact mass of an atom is called its atomic mass. This is usually measured with the atomic mass unit (amu), also called the dalton. One amu is exactly 1/12 of the mass of a carbon-12 atom, which is grams. Hydrogen-1 has a mass of about 1 amu. The heaviest atom known, oganesson, has a mass of about 294 amu, or grams. The average mass of all atoms of a particular element is called its atomic weight. Size The size of an atom depends on the size of its electron cloud. Moving down the periodic table, more electron shells are added. As a result, atoms get bigger. Moving to the right on the periodic table, more protons are added to the nucleus. This more positive nucleus pulls electrons more strongly, so atoms get smaller. The biggest atom is caesium, which is about 0.596 nanometers wide according to one model. The smallest atom is helium, which is about 0.062 nanometers wide.

How atoms interact When atoms are far apart, they attract each other. This attraction is stronger for some kinds of atoms than others. At the same time, the heat, or kinetic energy, of atoms makes them always move. If the attraction is strong enough, relative to the amount of heat, atoms will form a solid. If the attraction is weaker, they will form a liquid, and if it is even weaker, they will form a gas. Chemical bonds are the strongest kinds of attraction between atoms. The movement of electrons explains all chemical bonds. Atoms usually bond with each other in a way that fills or empties their outer electron shell. The most reactive elements have an almost full or almost empty outer shell. Atoms with a full outer shell, called noble gases, do not usually form bonds. There are three main kinds of bonds: ionic bonds, covalent bonds, and metallic bonds.

In an ionic bond, one atom gives electrons to another atom. Each atom becomes an ion: an atom or group of atoms with a positive or negative charge. The positive ion (which has lost electrons) is called a cation; it is usually a metal. The negative ion (which has gained electrons) is called an anion; it is usually a nonmetal. Ionic bonding usually results in a regular network, or crystal, of ions held together. In a covalent bond, two atoms share electrons. This usually happens when both atoms are nonmetals. Covalent bonds often form molecules, ranging in size from two atoms to many more. They can also form large networks, such as glass or graphite. The number of bonds that an atom makes (its valency) is usually the number of electrons needed to fill its outer electron shell.

In a metallic bond, electrons travel freely between many metal atoms. Any number of atoms can bond this way. Metals conduct electric current because electric charge can easily flow through them. Atoms in metals can move past each other, so it is easy to bend, stretch, and change the shape of metals. All atoms attract each other by Van der Waals forces. These forces are weaker than chemical bonds. They are caused when electrons move to one side of an atom. This movement gives a negative charge to that side. It also gives a positive charge to the other side. When two atoms line up their sides with negative and positive charges, they will attract. Although atoms are mostly empty space, they cannot pass through each other. When two atoms are very close, their electron clouds will repel each other by the electromagnetic force.

Magnetism To understand how magnets work, we can look at the properties of the atom. Any magnet has a north and south pole, and a certain strength. The direction and strength of a magnet, together, are called its magnetic moment. Every electron also has a magnetic moment, like a tiny magnet. This comes from the electron's spin and its orbit around the nucleus. The magnetic moments for the electrons add up to a magnetic moment for the whole atom. This tells us how atoms act in a magnetic field. Every electron has one of two opposite spins. We can think of one as turning to the right, and the other as turning to the left. If every electron is paired with an electron with the opposite spin in the same orbital, the magnetic moments will cancel out to zero. Atoms like this are called diamagnetic. They are only weakly repelled by a magnetic field.

However, if some electrons are not paired, the atom will have a lasting magnetic moment: it will be paramagnetic or ferromagnetic. When atoms are paramagnetic, the magnetic moment of each atom points in a random direction. They are weakly attracted to a magnetic field. When atoms are ferromagnetic, the magnetic moments of nearby atoms act on each other. They point in the same direction. This means that the whole object is a magnet, and it can point in the direction of a magnetic field. Ferromagnetic materials, such as iron, cobalt, and nickel, are strongly attracted to a magnetic field. Radioactive decay

Radioactive decay Some elements, and many isotopes, have what is called an unstable nucleus. This means the nucleus is either too big to hold itself together, or it has too many protons or neutrons. When a nucleus is unstable, it has to eliminate the excess mass of particles. It does this through radiation. An atom that does this is called radioactive. Unstable atoms emit radiation until they lose enough particles in the nucleus to become stable. All atoms above atomic number 82 (82 protons, lead) are radioactive.

There are three main kinds of radioactive decay: alpha, beta, and gamma. Alpha decay is when the atom shoots out a particle having two protons and two neutrons. This is a helium-4 nucleus. The result is an element with an atomic number of two less than before. So, for example, if a uranium atom (atomic number 92) went through alpha decay, it would become thorium (atomic number 90). Alpha decay happens when an atom is too big and needs to lose some mass. Beta decay is when a neutron turns into a proton, or a proton turns into a neutron. In the first case, the atom shoots out an electron. In the second case, it shoots out a positron (like an electron but with a positive charge). The result is an element with one higher or one lower atomic number than before. Beta decay happens when an atom has either too many protons or too many neutrons.

Gamma decay is when an atom shoots out a gamma ray, or wave. It happens when there is a change in the energy of the nucleus. This is usually after a nucleus has gone through alpha or beta decay. There is no change in the atom's mass, or atomic number, only in the stored energy inside the nucleus, in the form of particle spin.