title: Angel

paragraphs: 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.

paragraphs: Angels are powerful, smart spirits that obey God's commands and praise him with singing and they have male (masculine)gender, but without any sex. They sometimes appear to humans in 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: It describes the sound of their wings, "like the roar of rushing waters."

paragraphs: Ezekiel 10:5-7 ; Ezekiel 10:8 reveals that they have hands like a man under their wings .

paragraphs: Ezekiel 1:7 KJV reveals that they look like man but are different because they have "straight feet" and four wings and four faces.

paragraphs: Ezekiel ch 1, and 10 describe the cherubim creatures ascending and descending from the earth with wheels. Ezekiel 1:14-20 ; Ezekiel 10:16

paragraphs: 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.

paragraphs: They are often shown in art as having wings and a halo. The wings represent their speed, and the halo represents their holiness.

paragraphs: The cherubim in art always appear as baby faced angels with very small non useful wings.

paragraphs: 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.

paragraphs: 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.

paragraphs: The study of Angels is called Angelology.


title: Ad hominem

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: It is most of the time considered to be a weak and poor argument. In courts and in diplomacy ad hominems are not appreciated.

paragraphs: 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.

paragraphs: In logic, a proof is something that starts with premises, and goes through a few logical arguments, to reach a conclusion.

paragraphs: 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.


title: Native American

paragraphs: Native Americans (also called Aboriginal Americans, American Indians, Amerindians or indigenous peoples of America) are the people and their descendants, who were in the Americas when Europeans arrived. There are many different tribes of Native American people, with many different languages. There are more than three million Native Americans in Canada and the U.S. combined. About 51 million Native Americans live in Latin America.

paragraphs: 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.

paragraphs: 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 or killed by settlers who took their lands.

paragraphs: 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.

paragraphs: The earliest peoples 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.

paragraphs: 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.

paragraphs: Native Americans are divided into many small nations, called First Nations in Canada and tribes elsewhere.

paragraphs: According to the 2010 United States census, 0.9% of Americans say they are Native American, 2.9 million people, and 1.7% 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.

paragraphs: In the United States, most Native Americans live in cities. About 28% of Native Americans live on reservations. Many Native Americans are poor, and 24% are extremely poor. They tend to be the targets of violence more than white people are.


title: Apple

paragraphs: The apple tree ("Malus domestica") is a tree that grows fruit (such as apples) in the rose family best known for its juicy, tasty fruit. It is grown worldwide as a fruit tree. It is considered to be a low-cost fruit harvestable all over the world.

paragraphs: The tree originated in Central Asia. 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.

paragraphs: Apples are generally propagated 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 7,500 known cultivars of apples, with a range of desired characteristics. Different cultivars are bred for various tastes and uses: cooking, eating raw and cider production are the most common uses.

paragraphs: 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.

paragraphs: Worldwide production of apples in 2013 was 90.8 million tonnes. China grew 49% of the total.

paragraphs: The apple has a small, leaf-shedding tree that grows up to tall. The apple tree has a broad crown with thick twigs.

paragraphs: The leaves are alternately arranged simple ovals. They are 5 to 12 centimetres long and 3–6centimetres (1.2–2.4in) 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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 apple drinks.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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 may well be a different type. This means that the tree which would grow from planting would be a mixture of two. 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 only create apples of the type needed.

paragraphs: There are more than 7,500 known cultivars of apples. Different cultivars are available for temperate and subtropical climates. One large collection of over 2,100 apple cultivars is at the National Fruit Collection in England. Most of these cultivars 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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. 'Apple Day' is celebrated each October 21 in many countries.

paragraphs: Many apples are grown in temperate parts of the United States and Canada. In many areas where apple growing is important, people have huge celebrations:

paragraphs: There are lots of different varieties of apples, including:

paragraphs: Apples are in the group Maloideae. It is a subfamily of the family "Rosaceae". They are in the same subfamily as pears. Its family is the family of rose like plants, and roses are in the family.


title: Abrahamic religion

paragraphs: 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, Yazidi, 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

paragraphs: 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. They are also all ethical monotheistic religions. This means they have rules that they have to follow.


title: Algebra

paragraphs: Algebra (from Arabic: الجبر, transliterated "al-jabr", meaning "reunion of broken parts") is a part of mathematics (often called math in the United States and maths or numeracy in the United Kingdom ). It uses variables to represent a value that is not yet known. When an equals sign (=) is used, this is called an equation. A very simple equation using a variable is: 2 + 3 = x. In this example, x = 5, or it could also be said that "x equals five". This is called "solving for x".

paragraphs: 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.

paragraphs: 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.

paragraphs: People who do algebra use the rules of numbers and mathematic operations used on numbers. The simplest are adding, subtracting, multiplying, and dividing. More advanced operations involve exponents, starting with squares and square roots.

paragraphs: Algebra was first used to solve equations and inequalities. Two examples are linear equations (the equation of a straight line, y=mx+b) and quadratic equations, which has variables that are squared (multiplied by itself, for example: 2*2, 3*3, or x*x).

paragraphs: Early forms of algebra were developed by the Babylonians and the 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 AD, and died around 840 AD. 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").

paragraphs: Here is a simple example of an algebra problem:

paragraphs: These are the steps you can use to solve the problem:

paragraphs: 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.

paragraphs: As in most parts of mathematics, adding "z" to "y" (or "y" plus "z") is written as "y" + "z".

paragraphs: Subtracting "z" from "y" (or "y" minus "z") is written as "y" − "z".

paragraphs: Dividing "y" by "z" (or "y" over "z": formula_1) is written as "y" ÷ "z" or y/z. "y"/"z" is more commonly used.

paragraphs: In algebra, multiplying "y" by "z" (or "y" times "z") can be written in 4 ways: "y × z", "y * z", "y·z", or just "yz". The multiplication symbol "×" is usually not used, because it looks too much like the letter x, which is often used as a variable. Also, when multiplying a larger expression, parentheses can be used: "y" ("z+1").

paragraphs: When we multiply a number and a letter in algebra, we write the number in front of the letter: 5 × "y" = 5"y". When the number is 1, then the 1 is not written because 1 times any number is that number (1 × "y" = "y") and so it is not needed.

paragraphs: As a side note, you do not have to use the letters "x" or "y" in algebra. Variables are just symbols that mean some unknown number or value, so you can use any variable. "x" and "y" are the most common, though.

paragraphs: An important part of algebra is the study of functions, since functions 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.

paragraphs: 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 y = mx + b. The variable "b" is the y-intercept of the graph (where the line crosses the vertical axis) and "m" 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 (x, y).

paragraphs: In some math problems like the equation for a line, there can be more than one variable ("x" and "y" 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 "x" and the dependent variable is written as "y", for example, in y = 3x + 1. This is often put on a graph, using an "x" axis (going left and right) and a "y" axis (going up and down). It can also be written in function form: f(x) = 3x + 1. So in this example, we could put in 5 for "x" and get y = 16. Put in 2 for "x" would get y=7. And 0 for "x" would get y=1. So there would be a line going thru the points (5,16), (2,7), and (0,1) as seen in the graph to the right.

paragraphs: If x 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.

paragraphs: 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.

paragraphs: '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 do not matter. When the operator of two terms is an addition, the 'commutative property of addition' is applicable. In algebraic terms, this gives formula_6.

paragraphs: Note that this does not apply for subtraction! (i.e. formula_7)

paragraphs: When the operator of two terms is an multiplication, the 'commutative property of multiplication' is applicable. In algebraic terms, this gives formula_8.

paragraphs: Note that this does not apply for division! (i.e. formula_9, when formula_10)

paragraphs: '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 formula_11. Note that this does not hold for subtraction, e.g. formula_12 (see the distributive property).

paragraphs: 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 formula_13. Note that this does not hold for division, e.g. formula_14.

paragraphs: The distributive property states that the multiplication of a number by another term can be distributed. For instance: formula_15. (Do "not "confuse this with the associative properties! For instance, formula_16.)

paragraphs: '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 the sum of any number and 0 is that number: formula_17. This also holds for subtraction: formula_18.

paragraphs: The multiplicative identity property states that the product of any number and 1 is that number: formula_19. This also holds for division: formula_20.

paragraphs: The additive inverse property is somewhat like the opposite of the additive identity property. When an operation is the sum of a number and its opposite, and it equals 0, that operation is a valid algebraic operation. Algebraically, it states the following: formula_21. Additive inverse of 1 is (-1).

paragraphs: The multiplicative inverse property entails that when an operation is the product of a number and its reciprocal, and it equals 1, that operation is a valid algebraic operation. Algebraically, it states the following: formula_22. Multiplicative inverse of 2 is 1/2.

paragraphs: 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.

paragraphs: 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.

paragraphs: Many math problems are about physics and engineering. In many of these physics problems time is a variable. Time uses the letter "t". 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 "e", force is "f", mass is "m", acceleration is "a" and speed of light is sometimes "c". This is used in some famous equations, like f = ma and e=mc^2 (although more complex math beyond algebra was needed to come up with that last equation).


title: Atom

paragraphs: Atoms are very small pieces of matter. There are many different types of atoms, each with its own name, mass and size. These different types of atoms are called chemical elements. The chemical elements are organized on the periodic table. Examples of elements are hydrogen and gold.

paragraphs: Atoms are very small, but their exact size depends on the element. Atoms range from 0.1 to 0.5 nanometers in width. One nanometer is about 100,000 times smaller than the width of a human hair. This makes atoms impossible to see without special tools. Scientists discover how they work and interact with other atoms through experiments.

paragraphs: Atoms can join together to make molecules: for example, two hydrogen atoms and one oxygen atom combine to make a water molecule. When atoms join together it is called a chemical reaction.

paragraphs: Atoms are made up of three kinds of smaller particles, called protons, neutrons and electrons. The protons and neutrons are heavier, and stay in the middle of the atom, which is called the nucleus. The nucleus is surrounded by a cloud of light-weight electrons, these are attracted to the protons in the nucleus by the electromagnetic force because they have opposite electric charges.

paragraphs: The number of protons an atom has defines what chemical element it is, this number is sometimes called its atomic number. For example, hydrogen has one proton and sulfur has 16 protons. Because the mass of neutrons and protons is very similar, and the mass of electrons is very small, we can call the amount of protons and neutrons in an atom its atomic mass.

paragraphs: Atoms move faster when they are in their gas form (because they are free to move) than they do in liquid form and solid matter. In solid materials, the atoms are tightly packed next to each other so they vibrate, but are not able to move (there is no room) as atoms in liquids do.

paragraphs: The word "atom" comes from the Greek (ἀτόμος) "atomos", "indivisible", from (ἀ)-, "not," and τόμος, "a cut." The first historical mention of the word atom came from works by the Greek philosopher Democritus, around 400 BC. Atomic theory stayed as a mostly philosophical subject, with not much actual scientific investigation or study, until the development of chemistry in the 1650s.

paragraphs: In 1777 French chemist Antoine Lavoisier defined the term "element" for the first time. He said that an element was any basic substance that could not be broken down into other substances by the methods of chemistry. Any substance that could be broken down was a "compound".

paragraphs: In 1803, English philosopher John Dalton suggested that elements were tiny, solid balls made of 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. According to Dalton, in a certain compound, the atoms of the compound's elements always combine the same way.

paragraphs: In 1827, British scientist Robert Brown looked at pollen grains in water under his microscope. The pollen grains appeared to be jiggling. Brown used Dalton's atomic theory to describe patterns in the way they moved. This was called "brownian motion". In 1905 Albert Einstein used mathematics to prove that the seemingly random movements were caused by the reactions of atoms, and by doing this he conclusively proved the existence of the atom.

paragraphs: In 1869, Russian scientist Dmitri Mendeleev published the first version of the 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).

paragraphs: Elements in the same column, or period, usually have similar properties. For example, helium, neon, argon, krypton and xenon are all in the same column and have very similar properties. All these elements are gases that have no colour and no smell. Also, they are unable to combine with other atoms to form compounds. Together they are known as the noble gases.

paragraphs: The physicist J.J. Thomson was the first person to discover electrons. This happened while he was working with cathode rays in 1897. He realized they had a negative charge, unlike protons (positive) and neutrons (no charge). Thomson created the plum pudding model, which stated that an atom was like plum pudding: the dried fruit (electrons) were stuck in a mass of pudding (protons). In 1909, a scientist named Ernest Rutherford used the Geiger–Marsden experiment to prove that most of an atom is in a very small space called the atomic nucleus. Rutherford took a photo plate and covered it with gold foil, and 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 they make up only 1% of an atom's mass.

paragraphs: In 1913, Niels Bohr introduced the Bohr model. This model showed that electrons travel around the nucleus in fixed circular orbits. This was more accurate than the Rutherford model. However, it was still not completely right. Improvements to the Bohr model have been made since it was first introduced.

paragraphs: In 1925, chemist Frederick Soddy found that some elements in the periodic table had more than one kind of atom.

paragraphs: For example, any atom with 2 protons should be a helium atom. Usually, a helium nucleus also contains two neutrons. However, some helium atoms have only one neutron. This means they truly are helium, because an element is defined by the number of protons, but they are not normal helium, either. Soddy called an atom like this, with a different number of neutrons, an "isotope". To get the name of the isotope we look at how many protons and neutrons it has in its nucleus and add this to the name of the element. So a helium atom with two protons and one neutron is called helium-3, and a carbon atom with six protons and six neutrons is called carbon-12. However, when he developed his theory Soddy could not be certain neutrons actually existed. To prove they were real, physicist James Chadwick and a team of others created the mass spectrometer. The mass spectrometer actually measures the mass and weight of individual atoms. By doing this Chadwick proved that to account for all the weight of the atom, neutrons must exist.

paragraphs: In 1937, German chemist Otto Hahn became the first person to create nuclear fission in a laboratory. He discovered this by chance when he was shooting neutrons at a uranium atom, hoping to create a new isotope. However, he noticed that instead of a new isotope the uranium simply changed into a barium atom, a smaller atom than uranium. Apparently, Hahn had "broken" the uranium atom. This was the world's first recorded nuclear fission reaction. This discovery eventually led to the creation of the atomic bomb.

paragraphs: Further into the 20th century, physicists went deeper into the mysteries of the atom. Using particle accelerators they discovered that protons and neutrons were actually made of other particles, called quarks.

paragraphs: The most accurate model so far comes from the Schrödinger equation. Schrödinger realized 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 is used to find out where an electron is likely to be. This area is called the electron's orbital.

paragraphs: The complex atom is made up of three main particles; the proton, the neutron and the electron. The isotope of Hydrogen Hydrogen-1 has no neutrons, just the one proton and one electron. Protons have a positive electric charge and electrons have a negative charge. A positive hydrogen ion has no electrons, just the one proton. These two examples are the only known exceptions to the rule that all other atoms have at least one proton, one neutron and one electron each.

paragraphs: Electrons are by far the smallest of the three atomic particles, their mass and size is too small to be measured using current technology. They have a negative charge. Protons and neutrons are of similar size and weight to each other, protons are positively charged and neutrons have no charge.

paragraphs: Most atoms have a neutral charge; because the number of protons (positive) and electrons (negative) are the same, the charges balance out to zero. However, in ions (different number of electrons) this is not always the case, and they can have a positive or a negative charge. Protons and neutrons are made out of quarks, of two types; 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.

paragraphs: The nucleus is in the middle of an atom. It is made up of protons and neutrons. Usually in nature, two things with the same charge repel or shoot away from each other. So for a long time it was a mystery to scientists how the positively charged protons in the nucleus stayed together. They solved this by finding a particle called a "gluon". Its name comes from the word "glue" as gluons act like atomic glue, sticking the protons together using the "strong nuclear force". It is this force which also holds the quarks together that make up the protons and neutrons.

paragraphs: The number of neutrons in relation to protons defines whether the nucleus is stable or goes through radioactive decay. When there are too many neutrons or protons, the atom tries to make the numbers the same by getting rid of the extra particles. It does this by emitting radiation in the form of alpha, beta or gamma decay. Nuclei can change through other means too. Nuclear fission is when the nucleus splits into two smaller nuclei, releasing a lot of stored energy. This release of energy is what makes nuclear fission useful for making bombs and electricity, in the form of nuclear power.

paragraphs: The other way nuclei can change is through nuclear fusion, when two nuclei join together, or fuse, to make a heavier nucleus. This process requires extreme amounts of energy in order to overcome the electrostatic 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.

paragraphs: Electrons orbit, or travel around, the nucleus. They are called the atom's "electron cloud". They are attracted towards 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.

paragraphs: Around the nucleus, some electrons are further out than others, in different layers. These are called "electron shells". In most atoms the first shell has two electrons, and all after that have eight. Exceptions are rare, but they do happen and are difficult to predict. The further away the electron is from the nucleus, the weaker the pull of the nucleus on it. This is why bigger atoms, with more electrons, react more easily with other atoms.

paragraphs: The electromagnetism of the nucleus is not strong enough to hold onto their electrons and atoms lose electrons to the strong attraction of smaller atoms.

paragraphs: 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 has too many protons or neutrons. When this happens the nucleus has to get rid of the excess mass or particles. It does this through radiation. An atom that does this can be called "radioactive". Unstable atoms continue to be radioactive until they lose enough mass/particles that they become stable. All atoms above atomic number 82 (82 protons, lead) are radioactive.

paragraphs: There are three main types of radioactive decay; alpha, beta and gamma.

paragraphs: Every radioactive element or isotope has what is named a "half-life". This is how long it takes half of any sample of atoms of that type to decay until they become a different stable isotope or element. Large atoms, or isotopes with a big difference between the number of protons and neutrons will therefore have a long half life, because they must lose more neutrons to become stable.

paragraphs: Marie Curie discovered the first form of radiation. She found the element and named it radium. She was also the first female recipient of the Nobel Prize.

paragraphs: Frederick Soddy conducted an experiment to observe what happens as radium decays. He placed a sample in a light bulb and waited for it to decay. Suddenly, helium (containing 2 protons and 2 neutrons) appeared in the bulb, and from this experiment he discovered this type of radiation has a positive charge.

paragraphs: James Chadwick discovered the neutron, by observing decay products of different types of radioactive isotopes. Chadwick noticed that the atomic number of the elements was lower than the total atomic mass of the atom. He concluded that electrons could not be the cause of the extra mass because they barely have mass.

paragraphs: Enrico Fermi, used the neutrons to shoot them at uranium. He discovered that uranium decayed a lot faster than usual and produced a lot of alpha and beta particles. He also believed that uranium got changed into a new element he named hesperium.

paragraphs: Otto Hahn and Fritz Strassmann repeated Fermi's experiment to see if the new element hesperium was actually created. They discovered two new things Fermi did not observe. By using a lot of neutrons the nucleus of the atom would split, producing a lot of heat energy. Also the fission products of uranium were already discovered: thorium, palladium, radium, radon and lead.

paragraphs: Fermi then noticed that the fission of one uranium atom shot off more neutrons, which then split other atoms, creating chain reactions. He realised that this process is called nuclear fission and could create huge amounts of heat energy.

paragraphs: That very discovery of Fermi's led to the development of the first nuclear bomb code-named 'Trinity'.


title: Astronomy

paragraphs: Astronomy (from the Greek "astron" (ἄστρον) meaning "star" and "nomos" (nόμος) meaning "law") is the scientific study of celestial bodies such as stars, planets, comets, and galaxies

paragraphs: The objects studied include stars, galaxies, planets, moons, asteroids, comets and nebulae. Phenomena outside the Earth's atmosphere are also studied. That includes supernovae explosions, gamma ray bursts, and cosmic microwave background radiation. Astronomy concerns the development, physics, chemistry, meteorology and movement of celestial bodies, as well as the structure and development of the Universe.

paragraphs: Astronomy is one of the oldest sciences. Ancient people used the positions of the stars to navigate, and to find when was the best time to plant crops. Astronomy is very similar to astrophysics. 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", the belief that motion of the stars and the planets may affect human lives.

paragraphs: Since the 20th century there have been 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 uses maths and computer models to explain the observations and predict what might happen. Working together, theories predict what should happen and observations show whether the predictions work. The main work of astronomy is to explain puzzling features of the universe. For thousands of years the most important issue was the motions of planets; now many other topics are studied.

paragraphs: 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.

paragraphs: 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 in 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.

paragraphs: 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.

paragraphs: 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. A physicist called 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 decided that Galileo was wrong. He had to spend 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.

paragraphs: 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.

paragraphs: The 20th century after 1920 saw important changes in astronomy.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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 it implied an artificial source.

paragraphs: The period after World War 2 saw more observatories where large and accurate telescopes are built and operated at good observing sites, normally 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.

paragraphs: The next great revolution in astronomy was thanks to the birth of rocketry. This allowed telescopes to be placed in space on satellites.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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:

paragraphs: 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:

paragraphs: 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 resembles "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.

paragraphs: 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).

paragraphs: 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.

paragraphs: 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.

paragraphs: Adaptive optics means changing the shape of the mirror or lens while looking at something, to see it better.

paragraphs: 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 will then have various techniques used to analyse it.

paragraphs: 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.

paragraphs: A good example of a fields comes from pulsars which 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.

paragraphs: This section attempts to provide an overview of the important fields of astronomy, their period of importance and the terms used to describe them. It should be noted that astronomy in the Modern Era has been divided mainly by electromagnetic spectrum, although there is some evidence this is changing.

paragraphs: 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. Studying the Sun helped people understand how nuclear fusion works.

paragraphs: 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.

paragraphs: Galactic Astronomy is the study of distant galaxies. Studying distant galaxies is the best way of learning about our own galaxy, as the gases and stars in our own galaxy make it difficult to observe. Galactic Astronomers attempt to understand the structure of galaxies and how they are formed through the use of different types of telescopes and computer simulations.

paragraphs: 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 very limited.


title: Architecture

paragraphs: Architecture is the art and science of the design of structures or buildings such as houses, places of worship, and office buildings. Architecture is also the profession of an architect. Usually, a person must study at an institution of higher education (university) to become an architect. In ancient times, there were architects long before there was higher education.

paragraphs: Architecture can be about small designs, such as a garage, or large designs, such as a whole city. Architecture often overlaps with structural engineering, and architects and engineers often work together.

paragraphs: 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. The stone columns, which still hold up so many important buildings, like the Parthenon in Athens, were simply copied from the first wooden posts.

paragraphs: Classical Architecture was very formal, and it always obeyed laws. It used symmetry, which really means balance, and it used proportion which means keeping shapes in certain ways. The Golden Mean was a rule (or law) which said, (to put it very 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 as true today as they were 2000 years ago.

paragraphs: In some parts of the world, like India, the architecture is famous for carving the stone on temples and palaces. Different architectural styles were made in China, Japan, Southeast Asia, Africa, Mexico, and Central and South America.

paragraphs: Later, people 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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".

paragraphs: Many of the world's greatest structures were built by modern-day architects such as Frank Lloyd Wright, I. M. Pei, Adrian Smith, Edward Durell Stone, Frank Gehry, Fazlur Khan, Gottfried Böhm, and Bruce Graham.


title: Anatomy

paragraphs: 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.

paragraphs: 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.

paragraphs: For long periods the dissection of deceased people was forbidden, and correct ideas about human anatomy was a long time coming.

paragraphs: 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.

paragraphs: 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).

paragraphs: Anatomy, physiology and biochemistry are similar basic medical sciences.


title: Asteroid

paragraphs: An asteroid is a space rock. 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.

paragraphs: 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, while stars only seem to move because the Earth spins. 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.

paragraphs: 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 the purposes.

paragraphs: 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).

paragraphs: 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. Many scientists think asteroids striking the Earth killed off all the dinosaurs and caused some of the other extinction events.


title: Afghanistan

paragraphs: Afghanistan (officially called Islamic Republic of Afghanistan; , ) is a country located in Central Asia and South Asia. It has 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.

paragraphs: 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. This has resulted in there not being enough jobs.

paragraphs: The country is around in size or area. There are 30 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.

paragraphs: Afghanistan has many mountains. The mountains are called the Hindu Kush and Himalayas. The big mountain in Afghanistan is Mount Nowshak. There are plains (which have soil that is good for growing plants) and foothills. Part is also dry and called the Registan Desert.

paragraphs: Afghanistan has snow and glaciers in the mountains. Amu Darya is the big water stream, or river.

paragraphs: The country has a lot of a valuable stone called lapis lazuli, which was used to decorate the tomb of the Egyptian king Tutankhamun.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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. Almost all Afghans follow the religion of Islam.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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".

paragraphs: 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 Iranian people and the Vedas of Indo-Aryans.

paragraphs: 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.

paragraphs: Before the middle of the sixth century BCE, the land was held by the Medes.

paragraphs: 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 Greek culture and language. After Alexander, Greco-Bactrians, Scythians, Kushans, Parthians and Sassanians ruled the area.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: During the 1800s, Afghanistan became a buffer zone between two powerful empires, British India and Russia. 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: After the Soviets left, 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: Afghanistan is a newly formed democracy. Under the new constitution, the president and two vice presidents are elected every five years. The International Security Force Assistance (ISAF) helps the government maintain peace and rebuild the country.

paragraphs: The government still faces problems with the Taliban, internal security, and public services.

paragraphs: As of 2004, there are thirty-four provinces. Each province is divided into districts. (For cities see List of cities in Afghanistan.)


title: Angola

paragraphs: Angola, (), officially the Republic of Angola, is a country in southern Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city.

paragraphs: 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.

paragraphs: Portugal built up its power in Angola from the late 15th to the middle 20th century.

paragraphs: 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 anti-communist National Union for the Total Independence of Angola (UNITA). The war ended after the rebel leader was killed.

paragraphs: 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, and the South Atlantic Ocean to the west.

paragraphs: 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).

paragraphs: Angola had a population of 25,789,024 in 2014.

paragraphs: Angola is divided into eighteen provinces.

paragraphs: See List of settlements in Angola for the cities and towns in the country.


title: Argentina

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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).

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: Argentina is divided into 23 provinces ("provincias"; singular: "provincia"), and 1 city (commonly known as "capital federal"):

paragraphs: 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.

paragraphs: 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.

paragraphs: See List of cities in Argentina for the many places people live in Argentina.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: Medicine is socialized and so is education, making Argentina's literacy rate about 98%. State University is free as well.


title: Austria

paragraphs: Austria (; officially called 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. Currently, the chancellor is Sebastian Kurz. The previous chancellor was Brigitte Bierlein (2019). Austria has been a member-state of the United Nations since 1955 the European Union since 1995 and OPEC since 2019.

paragraphs: The people in Austria speak German, a few also speak Hungarian, Slovenian and Croatian. The capital of Austria is Vienna (Wien).

paragraphs: 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."

paragraphs: Austria is a democratic republic. 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.

paragraphs: Austria is also a federal state and divided into nine states ():

paragraphs: 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.

paragraphs: 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.

paragraphs: Austria was the Austrian Empire from about 800 to 1867 and was ruled by The House of Habsburg for most of that period. Between 1867 and 1918 it was a part of Austria-Hungary. Then it became a republic. The "First Republic" was from 1918 to 1938. From 1938 to 1945 Austria was part of Nazi Germany. The "Second Republic" was started in 1945.

paragraphs: Austria is a largely mountainous country since it is partially in the Alps. 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.

paragraphs: 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.

paragraphs: Austria has many artists, there are Gustav Klimt, Oskar Kokoschka, Egon Schiele or Friedensreich Hundertwasser, Inge Morath or Otto Wagner and scienc.

paragraphs: 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").


title: Armenia

paragraphs: Armenia is officially the Republic of Armenia. It is a country in the South Caucasus region of Eurasia. It is in Eastern Europe on the Armenian Highlands,

paragraphs: Armenia is bordered by Turkey to the west and Georgia to the north. The "de facto" independent Republic of Artsakh and Azerbaijan is to the east, and Iran and Azerbaijan's exclave of Nakhchivan to the south.

paragraphs: Armenia is a multi-party, democratic nation-state.

paragraphs: It has an ancient cultural heritage. 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.

paragraphs: 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.

paragraphs: During World War I, Armenians living in their ancestral lands in the Ottoman Empire were systematically exterminated in the Armenian Genocide. 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.

paragraphs: 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.

paragraphs: , Armenia includes 915 communities, of which 49 are considered urban and 866 are considered rural.

paragraphs: † 2011 censusSources: Area and population of provinces.

paragraphs: 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.

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


title: Archaeology

paragraphs: Archaeology, or archeology, is the study of the past by looking for the remains and objects left by the people who lived long ago. These remains can include old coins, tools, buildings, and inscriptions. Archaeologists, the people who study archaeology, use these remains to understand how people lived.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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."

paragraphs: 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.

paragraphs: This field involves attempts at replicating the actions and conditions of ancient cultures. Good examples are Butser Ancient Farm and Overton Down.

paragraphs: 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.

paragraphs: 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.


Application


title: Animal

paragraphs: Animals are eukaryotic organisms with many cells. They do not use light to get energy as plants do. Animals use different ways to get energy from other living things. They may eat other living things, though some are parasites or have photosynthetic protists as symbionts.

paragraphs: 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. The study of animals is called zoology.

paragraphs: Plants are also multicellular eukaryotic organisms, but live by using light, water and basic elements to make their tissues.

paragraphs: 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. They think several million species exist but they have only identified about one million.

paragraphs: Animals can mainly be divided into two main groups: the invertebrates and the vertebrates. Vertebrates have a backbone, or spine; invertebrates do not.

paragraphs: In scientific usage, humans are considered animals, in everyday nonscientific usage, humans are often not considered to be animals.

paragraphs: 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.

paragraphs: 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.

paragraphs: 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. The study of ancient life is called palaeontology.