title: George W. Bush

paragraphs: George Walker Bush (born July 6, 1946) is an American politician and businessman who was the 43rd President of the United States from 2001 to 2009. He is a Republican. He has a ranch in Crawford, Texas, which is near Waco. He is the son of former U.S. President George H. W. Bush and former U.S. First Lady Barbara Bush. He was Governor of Texas from 1995 to 2000.

paragraphs: Although he originally planned to focus his presidency on programs like education and stay out of foreign wars, the 9/11 terrorist attacks resulted in him changing his perspective. Since then, Bush created the Department of Homeland Security and sent the military to invade countries like Afghanistan and Iraq. In his opinion, the best way to deal with terrorism was to strike before the terrorists could.

paragraphs: Bush was born at Yale New Haven Hospital in New Haven, Connecticut. Bush grew up in Midland, Texas. He went to a high school called Phillips Academy in Andover, Massachusetts, and graduated in 1964. He went to school at Yale University from 1964 until he graduated in 1968, with a bachelor's degree in history. He joined the Texas Air National Guard in 1968 (part of the United States National Guard) during the Vietnam War and became a fighter pilot but did not fight in the war. He left the Texas Air National Guard in 1973. In 1975 Bush earned an MBA from Harvard University.

paragraphs: On November 5, 1977, Bush married Laura Welch. In 1978, Bush tried to get elected to Congress in West Texas, but lost. After that, he ran some oil companies and was one of the owners of the Texas Rangers baseball team. He thought about trying to become the commissioner of Major League Baseball, but went into politics instead. Bush is a Methodist. In 1994, he was elected to be Governor of Texas, defeating incumbent Democratic Governor Ann Richards.

paragraphs: Bush declared his candidacy for the 1994 Texas gubernatorial election. His campaign focused on four themes: welfare reform, tort reform, crime reduction, and education improvement. After easily winning the Republican primary, Bush faced popular Democratic incumbent Governor Ann Richards. Bush won the general election with 53.5 percent against Richards' 45.9 percent.

paragraphs: Bush used a budget surplus to push through Texas's largest tax-cut, $2 billion. He extended government funding for organizations providing education of the dangers of alcohol and drug use and abuse, and helping to reduce domestic violence.

paragraphs: In 1998, Bush won re-election with a record 69 percent of the vote. He became the first governor in Texas history to be elected to two consecutive four-year terms.

paragraphs: Throughout Bush's first term, national attention focused on him as a potential future presidential candidate. Following his re-election, speculation soared. Within a year, he decided to seek the 2000 Republican presidential nomination.

paragraphs: Bush ran against then-Vice President Al Gore in the 2000 United States presidential election. More than 100 million people voted on November 7, 2000. But the election was very close. When they began counting the votes, it became clear that whoever got the most votes in the state of Florida would win the election. But there were many issues with the ballots in Florida. Gore sued to get Florida to count the votes again. For more than a month no one knew who won the election. The Supreme Court made a decision to stop recounting votes. Gore decided to accept his loss on December 13 and Bush was declared the winner.

paragraphs: While he was President, George W. Bush signed the No Child Left Behind Act into law. It was an education reform bill.

paragraphs: Bush was the first President of the United States to deliver a speech in both Spanish and in English.

paragraphs: He added Part D to Medicare, which gives older people free medicine if they can not afford it.

paragraphs: He also signed very large tax cuts (many of them were for the middle and lower class) during his presidency.

paragraphs: Bush did not approve of abortion. In 2004, he signed the Unborn Victims Of Violence Act which made it so that if a pregnant woman is murdered, her murderer can also be charged with killing the fetus that the woman was carrying.

paragraphs: His first foreign policy test came when an American spy plane crashed in China. Bush peacefully negotiated the release of the plane crew.

paragraphs: Eight months after Bush became president, the September 11 attacks occurred. Because of this, President Bush declared a War on Terrorism.

paragraphs: Bush tried to do many things to stop another terrorist attack from happening. He ordered an invasion of Afghanistan in 2002. He did this because the leaders of Afghanistan were helping Osama bin Laden, who was responsible for attacking America on September 11, 2001. Almost ten years later, on May 2, 2011 bin Laden was killed on orders of President Barack Obama. The war in Afghanistan (2001–present) has not ended yet. Bush asked Congress to do more to stop terrorism. As a result, Congress passed a law that created the Department Of Homeland Security, a government department which tries to prevent terrorist attacks from happening. It also responds to emergencies such as floods or diseases.

paragraphs: He signed the Patriot Act (which allowed the government to listen to people's phone calls so it can track down terrorists which try to communicate with each other).

paragraphs: After Saddam refused to cooperate with the United Nations weapons inspectors and the United States Congress authorized Bush to invade Iraq if its government did not cooperate with the weapons inspectors, Bush decided on the Gulf War in 2003 with several allies. Saddam Hussein was removed from power, and Iraq turned into a democracy. Over 100,000 people were killed in this war.

paragraphs: In the 2004 presidential election, Bush won again with a majority of votes. His opponent was Massachusetts Senator John Kerry, a Democrat.

paragraphs: In 2005, Hurricane Katrina (the most destructive hurricane in American history) happened. It caused over 1800 deaths and caused billions of dollars of destruction. George W. Bush signed several acts into law which would help Hurricane Katrina victims.

paragraphs: In the Iraq War, no weapons of mass destruction were found, and the Bush Administration was criticized for being wrong about Iraq having weapons of mass destruction. Bush added more American troops to Iraq (which was called "the surge") to speed up the war. The surge was successful, and in result, Iraq had less violence.

paragraphs: Although the economy was doing very well during much of his presidency, in early 2008, the economy was slowing down. Bush signed a bill into law which would gave $600 to every American citizen, hoping that people would go out and spend the money so that it would prevent a recession (a bad economy) from happening.

paragraphs: Later in 2008, stock market crashed and the country fell into its worst recession since the Great Depression. Bush helped create a 700 billion dollar bailout, which would give money to corporations (large businesses) to prevent them from being bankrupt and to try to prevent the recession from getting worse.

paragraphs: Bush publicly supported Republican candidate John McCain during the 2008 presidential election, but Barack Obama won the election.

paragraphs: During the last few days he was President, Bush gave his farewell address. He was succeeded by Barack Obama.

paragraphs: After his presidency, Bush stayed away from the spotlight and did not want much attention. He said that he was not going to criticize President Obama. He began to build his presidential library in 2010. It was open to the public in 2013.

paragraphs: After over a year and a half of saying little in public, in November of 2010, Bush appeared on several television interviews and released a book called "Decision Points". The book focuses on fourteen big decisions he made, including quitting drinking, running for president, Hurricane Katrina, invading Iraq, and his response to the financial meltdown in 2008.

paragraphs: On May 2, 2011, President Obama called Bush, who was at a restaurant with his wife, to inform him that Osama bin Laden had been killed. The Bushes joined the Obamas in New York City to mark the tenth anniversary of the September 11, 2001, terrorist attacks. At the Ground Zero memorial, Bush read a letter that President Abraham Lincoln wrote to a widow who lost five sons during the Civil War.

paragraphs: On August 6, 2013, Bush was successfully treated for a coronary artery blockage with a stent. The blockage had been found during an annual medical examination.


title: Organic compound

paragraphs: Organic compounds are carbon-based compounds. Organic compounds contain carbon bonds in which at least one carbon atom is covalently linked to an atom of another type (usually hydrogen, oxygen or nitrogen). Most polymers are organic compounds.

paragraphs: The name "" is a historical name from the 19th century.

paragraphs: People believed that only living things could make organic compounds and "dead" things (such as minerals) could make inorganic compounds. However, Friedrich Wöhler proved this wrong by synthesizing urea, a well-known organic compound.

paragraphs: There are natural organic compounds, and synthetic ones. Their structure may be described by using names, and making diagrams.

paragraphs: One way of showing the molecule is by drawing its structural formula. Because molecules can have complicated structures, people have made ways to show them in simple language. One way is to use line diagrams. Each atom is shown by a letter, and connected by a line to each atom with which it is has a covalent bond. One line means a single bond, two lines means a double bond and so on.

paragraphs: Because there is in an infinite number of possible organic compounds, language is needed to give a unique name to each one. The International Union of Pure and Applied Chemistry, or IUPAC, made a system for doing this. Although an IUPAC name makes every single possible molecule unique, the names are often long and complicated, so in everyday life, "trivial" names--unofficial but widely understood names--are used, such as the trivial names Paracetamol, Tylenol, and Acetaminophen, which are used for a compound whose IUPAC name is "N-(4-hydroxyphenyl) acetamide". Some of these trivial names are trademarks.

paragraphs: Natural compounds are compounds made by plants or animals. These could also be made in a lab, but many of these compounds are taken from nature because it is easier and less expensive to do it that way. Commonnatural compounds are: amino acids, proteins, carbohydrates, many antibiotics like Penicillin and Amoxicillin.

paragraphs: Synthetic compounds are those made by people. Sometimes, this is done by taking something natural and changing the molecule in a small way, such as making glycerin from vegetable oils. Other compounds are synthesized in long, complicated reactions with many steps. Plastics are sometimes mostly natural, and other kinds are manufactured.

paragraphs: Since a compound is often first discovered in nature instead of being made on purpose in a lab, people may know the compound exists, and even know what it does sometimes, but not know exactly what atoms it is made of and how it is arranged. There are several ways of taking an unknown compound and finding out this structure:


title: Coal

paragraphs: Coal is a hard rock which can be burned as a solid fossil fuel. It is mostly carbon but also contains hydrogen, sulphur, oxygen and nitrogen. It is a sedimentary rock formed from peat, by the pressure of rocks laid down later on top.

paragraphs: Peat, and therefore coal, is formed from the remains of plants which lived millions of years ago in tropical wetlands, such as those of the late Carboniferous period (the Pennsylvanian). Also wood heated in an airless space can make charcoal, which is like coal.

paragraphs: Coal can be burned for energy or heat. About two-thirds of the coal mined today is burned in power stations to make electricity. Like oil, when coal is burned its carbon joins with oxygen in the air and makes a lot of carbon dioxide, which causes climate change. Because of that and other air pollution from coal most countries are turning to new sources of energy, such as solar power. But new coal power plants are still being built in some parts of the world, such as China.

paragraphs: Coal can be roasted (heated very hot in a place where there is no oxygen) to produce coke. Coke can be used in smelting to reduce metals from their ores.

paragraphs: Coal was the most important fuel of the Industrial Revolution. Coal was an important part of rail freight in the UK in the 20th century, forming the greater part of several companies' freight volume. Early in the 21st century most coal fired power stations in the United Kingdom and several other countries were closed to reduce greenhouse gas emissions.

paragraphs: Under suitable conditions, plant material is transformed step by step into

paragraphs: Diamond is commonly believed to be the end result of this process, but this is not true. Diamond is carbon but is not formed from coal.

paragraphs: Coal contains impurities. The particular impurities determine the use. Coking coal has little ash or sulfur or phosphorus. Those would spoil the iron made by the blast furnace.

paragraphs: Coal, when burnt, gives off almost a third more carbon dioxide per unit of energy than oil, and 80% more than natural gas. Almost half of the carbon dioxide from people is because of burning coal so it is the biggest single cause of global warming. Coal contributes to acid rain and smog, especially when burned without scrubbers. Burning coal releases toxic chemicals, including soot, mercury, and carbon monoxide, which contribute to diseases such as cancer and asthma in both humans and wild animals. Coal mining, especially mountaintop removal mining, can damage large areas of land and destroy natural habitats. Higher grades of coal burn more cleanly than lower grades, although they still pollute more than other fuels. In addition to air pollution, burning coal produces toxic coal ash, which can cause water pollution if it is accidentally released into the environment. There are several underground mine fires burning throughout the world. These underground fires release toxic smoke into the air, and can also cause the ground above to collapse. The city of Centralia, Pennsylvania was evacuated and is now abandoned due to an underground coal mine fire.

paragraphs: It is difficult to give exact figures for the effects of coal on health. It is claimed that because of coal every year over 800,000 people die early and millions of people get ill. Coal miners often get pneumoconiosis (black lung disease) from exposure to coal dust.

paragraphs: Opposition to coal pollution was one of the main reasons the modern environmental movement started in the 19th century.

paragraphs: Peak coal means the year in which most coal is mined or burned. Many countries have already passed their peak coal years, for example Germany in 1985 and the United States in 2008. Now those countries are mining and burning less coal. But China still mines a lot of coal and is helping a few countries, like Pakistan, mine more coal and build more coal-fired power stations. So the peak coal year for the world "may" have passed.

paragraphs: Compared to other non-renewable sources of energy, coal is inefficient and produces high amounts of greenhouse gases. Coal is commonly found and cheap.

paragraphs: The world's top coal producer is China, which produces about 4 billions tonnes each year, followed in order by India, United States, Australia, Indonesia and Russia with less than a billion tonnes each. The largest exporter by far is Australia and the largest importers are China, India and Japan.

paragraphs: In some cultures, Santa Claus brings coal to misbehaved children for Christmas. This legend comes from Victorian times when it was common to burn coal in the fireplace, rather than wood. Children who did not receive toys would at least get coal to stay warm.


title: Petroleum

paragraphs: Petroleum, (from Greek πέτρα - rock and έλαιο - oil) also called crude oil, is a thick and black liquid. It is a natural material mainly made of hydrocarbons. Most petroleum is found by drilling down through rocks on land or off-shore on the continental shelf. Major producers are in the Middle East, the Americas, and Russia. It is the most important world fuel source. It supplies 38% of the world's energy and is also used to make petrochemicals.

paragraphs: Crude oil is a mixture of many different chemicals (mostly hydrocarbons), most of which burn well. It is separated into simpler, more useful mixtures by fractional distillation in oil refineries to give separate chemicals such as gasoline (or "petrol") for cars, kerosene for airplanes and bitumen for roads. The bitumen gives crude oil its dark black color; most of the other chemicals in crude are slightly yellow or colorless.

paragraphs: Petroleum can be easily transported by pipeline and oil tanker. Refined petroleum is used as fuels; mainly gasoline ("petrol") for cars, diesel fuel for diesel engines used in trucks, trains and ships, kerosene fuel for jets and as lubricants.

paragraphs: Petroleum resource is limited and non-renewable. Some believe it will run out within 70 years after a peak oil early in the 21st century.

paragraphs: Burning petroleum or other fossil fuel adds the carbon in the oil to the oxygen in the air to create carbon dioxide, which is an air pollutant. The carbon can be removed from the carbon dioxide by plants.

paragraphs: There is a lot of crude oil left underground. Oil companies quote "reserves" which some people confuse with the actual amount of oil underground, but are more to do with the cost of extracting it by oil wells. Most of the crude left underground is in the Middle East which is not a politically stable part of the world. Some governments with lots of oil reserves work together through OPEC to keep production low and prices high. Politicians in countries that burn much oil complain about high oil prices, because voters complain. However many environmentalists worry about damage being done by using oil as a fuel source (especially global warming) and are therefore happy when prices are kept high so that people use less oil.


title: Natural gas

paragraphs: Natural gas is a mixture of gases. It consists mainly of hydrocarbons. The main component is methane. Natural gas is often found in the ground, either alone or together with petroleum. Landfills and natural processes produce a little methane. Usually it is transported to users in a pipeline.

paragraphs: Most natural gas is burnt as a fuel to produce energy. It burns with a clean blue flame, causing little pollution.

paragraphs: Natural gas is burned to produce electricity, to cook and to heat buildings. It is also used as fuel for natural gas vehicles for transport. When natural gas is burned in a power station it boils water into steam that spins a steam turbine that turns a generator to make electricity. Some power stations use natural gas in a gas turbine.

paragraphs: Natural gas is also converted into many different industrial chemicals. It is the most common feedstock for making pure hydrogen. Hydrogen is used as fuel in fuel cells, and to make ammonia. Ammonia is used as a fuel, as a fertilizer for crops, and for making many other things. Natural gas is also converted into monomers to make many plastic products.


title: Energy

paragraphs: In physics, energy is the capacity to do work; the influence required to perform an action. The amount of energy in a system is the amount of change that can be made to it.

paragraphs: Energy is a property that is not created or destroyed, although energy can change in detectable form. This is a rule that is commonly understood as the "conservation law of energy". In respects to this rule, the total amount of energy that exists within an isolated system will always be the same, no matter what changes have been made to it.

paragraphs: In the early 20th century, scientist were able to discover that matter itself can be created from energy and vice versa. This is just another change of form. After these discoveries, the conservation law of energy was extended to become the conservation law of matter and energy: matter and energy can neither be created from nothing nor destroyed to the point of complete erasure from reality. Albert Einstein was the first to mathematically derive this in the formula E = mc.

paragraphs: Matter can be created from energy or converted into energy through the use of processes, such as nuclear fission or nuclear fusion.

paragraphs: Scientists have identified many types of energy, and found that they can be changed from one kind into another. For example:

paragraphs: Energy can be measured. The amount of energy a thing has can be given a number.

paragraphs: As in other kinds of measurements, there are measurement units. The units of measurement for measuring energy are used to make the numbers meaningful.

paragraphs: The SI unit for both energy and work is the joule (J). It is named after James Prescott Joule. 1 joule is equal to 1 newton-metre. In terms of SI base units, 1 J is equal to 1 kg m s. It is most often used in science, though particle physics often uses the electronvolt.

paragraphs: The measurement for electricity most often uses the kilowatt-hour (kW·h). One kW·h is equivalent to 3,600,000 J (3600 kJ or 3.6 MJ).


title: Jewel

paragraphs: Jewels (or gems or gemstones) are rare minerals. They usually have colours. They begin in a rough rock form but can be cut and polished to make jewellery.

paragraphs: However, some other non-mineral rocks (such as lapis lazuli) or organic materials can also be also used for jewelry and are called gemstones. These include amber or jet. Pearls and coral are sometimes also called gemstones.

paragraphs: Most gemstones are hard. Soft minerals are used in jewelry too, because of their luster that gives them value. Being rare (in short supply) also makes a gemstone valuable.

paragraphs: The Ancient Greeks began to decide which gems are precious and semi-precious. This continued in other cultures. In modern times, the precious stones are diamond, ruby, sapphire and emerald, with all other gemstones being semi-precious.


title: Xenon

paragraphs: Xenon is a non-metal chemical element. It has the chemical symbol Xe and atomic number 54. It is one of the few elements that are a gas at Standard temperature and pressure.

paragraphs: Sir William Ramsay and M. W. Travers discovered this element in 1898. The element's name came from the Greek word "xenos", which means 'stranger'.

paragraphs: Xenon belongs to the group of the noble gases. Noble gases are very unreactive. However, in 1962, chemists have found that xenon can react with fluorine under special conditions, such as high pressure and high temperature. It is not known why xenon behaves differently under these circumstances. There are also some compounds with oxygen. The gas is not very reactive, because if fulfills the octet rule. This means that a lot of energy is needed to remove an electron from xenon. This activation energy for xenon is 1172 kJ/mol. To remove a second electron from xenon, an energy of 2046.4 kJ/mol is needed.

paragraphs: Known oxidation states of xenon are 0, +1, +2, +4, +6 and +8. However, the most stable form is pure xenon, or the xenon's oxidation state of 0. Xenon has 8 stable isotopes and more than 30 unstable isotopes.

paragraphs: Xenon gas is used in electron tubes, bactericidal lamps, strobe lamps, and lamps used to excite ruby lasers.

paragraphs: It has the atomic mass of 131.294 and is the 5th inert gas in the inner gas group


title: Kuala Lumpur

paragraphs: Kuala Lumpur is the capital city of Malaysia and a Federal Territory. After Putrajaya was constructed in the late 1990s, the administrative capital has been moved there. Kuala Lumpur has one of the tallest buildings in the world, the Petronas Twin Towers.

paragraphs: Kuala Lumpur has a tropical rainforest climate ("Af" in the Koeppen climate classification).

paragraphs: The annual range of temperature in Kuala Lumpur is small, only 1°C. There is no distinct seasonal difference in temperature in the city. Kuala Lumpur is hot throughout the year. The annual mean temperature are 26.5 °C (79.7 °F).

paragraphs: The annual rainfall in Kuala Lumpur is high (2393mm). The rainfall distribution is even in the city, with heavy rainfall all the year. In April and November, the monthly rainfall is slightly higher.

paragraphs: Since Kuala Lumpur became a Federal Territory of Malaysia on February 1, 1972, the city has been led by seven mayors. They are:


title: Speed of light

paragraphs: The speed of light in empty space is a universal physical constant. This means it is the same everywhere in empty space and does not change with time. Physicists often use the letter to denote the speed of light in empty space (vacuum). It is exactly by definition. A photon (particle of light) travels at this speed in a vacuum.

paragraphs: According to special relativity, is the maximum speed at which all energy, matter, and physical information in the universe can travel. It is the speed of all massless particles such as photons, and associated fields—including electromagnetic radiation such as light—in a vacuum.

paragraphs: It is predicted by the current theory to be the speed of gravity (that is, gravitational waves). Such particles and waves travel at regardless of the motion of the source or the inertial frame of reference of the observer. In the theory of relativity, interrelates space and time, and appears in the famous equation of mass–energy equivalence .

paragraphs: The special theory of relativity is based on the prediction, so far upheld by observations, that the measured speed of light in a vacuum is the same whether or not the source of the light and the person doing the measuring are moving relative to each other. This is sometimes expressed as "the speed of light is independent of the reference frame."

paragraphs: This behavior is different from our common ideas about motion as shown by this example:

paragraphs: George is standing on the ground next to some train tracks (railroad). There is a train rushing by at . George throws a baseball at in the direction the train is moving. Tom, a passenger on the train, has a device (like a radar gun) to measure throwing speeds. Because he is on the train, Tom is already moving at in the direction of the throw, so Tom measures the speed of the ball as only .

paragraphs: In other words, the speed of the baseball, as measured by Tom on the train, depends on the speed of the train.

paragraphs: In the example above, the train was moving at 1/3 the speed of the ball, and the speed of the ball as measured on the train was 2/3 of the throwing speed as measured on the ground.

paragraphs: Now, repeat the experiment with light instead of a baseball; that is, George has a flashlight instead of throwing a baseball. George and Tom both have devices that are the same to measure the speed of light (instead of the radar gun in the baseball example).

paragraphs: George is standing on the ground next to some train tracks. There is a train rushing by at 1/3 the speed of light. George flashes a light beam in the direction the train is moving. George measures the speed of light as . Tom, a passenger on the train, measures the speed of the light beam. What speed does Tom measure?

paragraphs: Intuitively, one may think that the speed of the light from the flashlight as measured on the train should be 2/3 the speed measured on the ground, just like the speed of the baseball was 2/3. But in fact, the speed measured on the train is the full value, , not .

paragraphs: It sounds impossible, but that is what one measures.

paragraphs: A consequence of this fact that the speed of light is the same for all observers, is that nothing can go faster than the speed of light. Another consequence is that for objects that have mass, no matter how much energy is used to increase the speed of an object, it will get closer and closer, but it will never reach the speed of light. These ideas were discovered in the early 1900s by Albert Einstein, whose work completely changed our understanding of light.

paragraphs: Maxwell's equations predicted the speed of light and confirmed Michael Faraday's idea that light was an electromagnetic wave (a way that energy moves). From these equations, we find that the speed of light is related to the inverse of the square root of the permittivity of free space, "ε", and the permeability of free space, "μ":

paragraphs: The index of refraction of a clear material is the ratio between the speed of light in a vacuum and the speed of light in that material.

paragraphs: Ole Christensen Rømer used an astronomical measurement to make the first quantitative estimate of the speed of light. When measured from Earth, the periods of moons orbiting a distant planet are shorter when the Earth is approaching the planet than when the Earth is receding from it. The distance travelled by light from the planet (or its moon) to Earth is shorter when the Earth is at the point in its orbit that is closest to its planet than when the Earth is at the farthest point in its orbit, the difference in distance being the diameter of the Earth's orbit around the Sun. The observed change in the moon's orbital period is actually the difference in the time it takes light to traverse the shorter or longer distance. Rømer observed this effect for Jupiter's innermost moon Io, and he deduced that light takes 22 minutes to cross the diameter of the Earth's orbit.

paragraphs: Another method is to use the aberration of light, discovered and explained by James Bradley in the 18th century. This effect results from the vector addition of the velocity of light arriving from a distant source (such as a star) and the velocity of its observer (see diagram on the right). A moving observer thus sees the light coming from a slightly different direction and consequently sees the source at a position shifted from its original position. Since the direction of the Earth's velocity changes continuously as the Earth orbits the Sun, this effect causes the apparent position of stars to move around. From the angular difference in the position of stars, it is possible to express the speed of light in terms of the Earth's velocity around the Sun. This, with the known length of a year, can be easily converted to the time needed to travel from the Sun to the Earth. In 1729, Bradley used this method to derive that light travelled 10,210 times faster than the Earth in its orbit (the modern figure is 10,066 times faster) or, equivalently, that it would take light 8 minutes 12 seconds to travel from the Sun to the Earth.

paragraphs: Nowadays, the "light time for unit distance"—the inverse of "c" (1/c), expressed in seconds per astronomical unit—is measured by comparing the time for radio signals to reach different spacecraft in the Solar System. The position of spacecraft is calculated from the gravitational effects of the Sun and various planets. By combining many such measurements, a best fit value for the light time per unit distance is obtained. , the best estimate, as approved by the International Astronomical Union (IAU), is:

paragraphs: The relative uncertainty in these measurements is 0.02 parts per billion (2), as equivalent to the uncertainty in Earth-based measurements of length by interferometry. Since the metre is defined to be the length travelled by light in a certain time interval, the measurement of the light time for unit distance can also be interpreted as measuring the length of an AU in metres. The metre is considered to be a unit of proper length, whereas the AU is often used as a unit of observed length in a given frame of reference.

paragraphs: The finite speed of light is a major constraint on long-distance space travel. Supposing a journey to the other side of the Milky Way, the total time for a message and its reply would be about 200,000 years. Even more seriously, no spacecraft could travel faster than light, so all galactic-scale transport would be effectively one-way, and would take much longer than than any modern civilisation has existed.

paragraphs: The speed of light can also be of concern over very short distances. In supercomputers, the speed of light imposes a limit on how quickly data can be sent between processors. If a processor operates at 1 gigahertz, a signal can only travel a maximum of about in a single cycle. Processors must therefore be placed close to each other to minimize communication latencies; this can cause difficulty with cooling. If clock frequencies continue to increase, the speed of light will eventually become a limiting factor for the internal design of single chips.


title: Denial

paragraphs: Denial is a word used in psychology. It means that someone denies that something has happened or is happening although he really knows it is true. Usually this happens because admitting it would cause a lot of pain.

paragraphs: Denial is usually the first state of coping with loss. For example, if someone close to a person dies, the survivor's first feeling might be denial, or refusal to accept the fact that the person is really dead.

paragraphs: Denial, is also when you think that a team (like in football) will win a football match before its even started and refuse to accept the fact thet they could lose

paragraphs: Denial, is also when you refuse to accept the fact that someone else did something (like change something) when you 'think you know' it was a different person


title: Tokyo

paragraphs: Tokyo is the center of the Japanese government. The Imperial Palace is in Tokyo.

paragraphs: Tokyo is the center of business, trade, and industry of Japan and also of Asia. The city is the center of the largest metropolitan area in the world.

paragraphs: It became the capital city of Japan in the middle of 19th century, when its name changed from "Edo" to "Tokyo". Before then, Kyoto was the capital of Japan. The Emperor of Japan, or Tenno, lived in Kyoto. Edo was the place where the Tokugawa Shoguns lived. The city grew up under the control of the shoguns. Before then it was a small town on the sea. Edo means "the mouth of a river" in Japanese.

paragraphs: Tokyo was destroyed by fires started by the Great Kantō earthquake in 1923. It was also badly damaged by bombs during World War II. After Japan lost the war, the city was rebuilt.

paragraphs: Tokyo began as a small fishing village named Edo. Edo was in the old Musashi Province.

paragraphs: The Edo clan built walls to protect the town in the late 12th century. In 1457, Ōta Dōkan built Edo Castle. In 1590, Tokugawa Ieyasu made Edo his base. He became shogun in 1603, and the town became the center of his military government. This marked the beginning of the Edo period. During this time, Edo grew into one of the largest cities in the world. More than one million people lived there by the 18th century.

paragraphs: Edo was not the capital of Japan. The emperor lived in the capital, Kyoto. However, since the shogun was more powerful than the emperor throughout Japanese history, Edo had more power. After about 263 years, the Meiji Restoration removed the shogun from power. In 1869, the 17-year-old Emperor Meiji moved to Edo. The old Edo Castle became the Imperial Palace.

paragraphs: The Tokyo Prefecture and the city of Tokyo were established. This was the capital city until 1943.

paragraphs: In 1943, Tokyo City and the "associated municipalities of what was formerly (1869-1943)" combined into one.

paragraphs: Central Tokyo is built around major railway stations. Suburban railways were built relatively cheaply at street level. There are some expressways.

paragraphs: Tokyo suffered two major catastrophes in the 20th century. The 1923 Great Kantō earthquake left 140,000 dead or missing. World War II was the other disaster for the city. The Bombing of Tokyo from 1944 through 1945 killed between 75,000 and 200,000 people and destroyed half the city. This was almost as much damage as the atomic bombs of Hiroshima and Nagasaki combined.

paragraphs: Tokyo was completely rebuilt after the war. The 1964 Summer Olympics were a major world event. New high-rise developments such as Sunshine 60 started in the 1970s.

paragraphs: Tokyo has a four-season climate with rainy summers and dry winters.

paragraphs: As of October 2007 about 8.7 million were living in Tokyo's 23 special wards. The number of people in Tokyo increases to over 15 million during the day. About 2.5 million workers and students enter the city everyday. The three central wards of Chiyoda, Chūō, and Minato increase the most. As of 2005, the regular population in those three areas was only 326,000 at night, but there are 2.4 million in those areas during the day.

paragraphs: Tokyo has many international residents. As of 2005, the most common groups in Tokyo are Chinese (123,661), Koreans (106,697), and Filipinos (31,077). Americans (18,848), British (7,696), Brazilian (5,300) and French (3,000) are less common.

paragraphs: The 23 special wards of Tokyo are the same area that had been called Tokyo City. On July 1, 1943, Tokyo City was merged with to become a special government area. This made the wards different from other wards in Japan. Other city wards are part of a larger city government, but these are not.

paragraphs: Each ward is a municipality with its own mayor and assembly like the other cities of Japan. The special wards often use the word city in their official English name, e.g. Chiyoda City.

paragraphs: The wards have a unique administrative relationship with the prefectural government. The Tokyo Metropolitan Government manages some public works such as water, sewer, and fire-fighting. To pay for these things, the prefecture collects the municipal taxes usually collected by a city.

paragraphs: Three wards of Tokyo make up the central part of the city. They are Chiyoda, Chūō and Minato.

paragraphs: Tokyo has many sight-seeing spots, but very few of them are old. There are very few buildings in Tokyo that are more than 50 years old. Popular places for visitors range from Tokyo Tower in the center of the city to Mount Takao out in the western countryside. Tokyo Sky Tree is a new tower and is the tallest in Japan. Traditional religious sights such as Meiji Shrine and Sensō-ji attract many tourists. The Imperial Palace can be seen in the middle of the city, but is not open to the public.

paragraphs: Tokyo is the cultural, business, and political center of the country. It is also the center of many transport systems. There are many air, rail, sea, and road links in and out of the city. Local subway and bus systems serve every part of the city.

paragraphs: Two commercial airports serve Tokyo. Haneda Airport is in the city limits next to Tokyo Bay. This airport is mostly for domestic travel. Most international flights to and from Tokyo go through Narita Airport in Chiba Prefecture.

paragraphs: Several Shinkansen super-express railway lines begin at Tokyo Station, including the Tōkaidō Shinkansen going west and Tōhoku Shinkansen going northeast. Tokyo Metro is the city's major subway system.

paragraphs: Tokyo has a busy international and domestic port, but more traffic goes through the nearby port of Yokohama. There are domestic ferries to the islands of Tokyo, but also to other parts of the country such as Hokkaido.

paragraphs: Many highways meet in Tokyo, including: the Chūō, Kan-Etsu, Tōhoku, and Tōmei Expressways. All highway distances in Japan start from zero at a marker in Nihonbashi, Tokyo.


title: Laozi

paragraphs: Laozi (Lao Tsu, Lao-Tze) was a Chinese philosopher best known for Taoism, the Tao Te Ching, and for becoming a deity of Taoism and Chinese folk religions. A legendary figure of Chinese culture, Laozi may have lived during the Warring States period. Laozi's work influenced anti-authoritarian and Legalist philosophers.

paragraphs: Laozi's personal name is supposedly "Li Er" (李尔). His courtesy name is "Boyang" (伯阳). A popular posthumous name is "Li Dan" "Lǐ Dān"). During the Tang dynasty, he was called the "Supremely Mysterious and Primordial Emperor" "Tàishàng Xuānyuán Huángdì").

paragraphs: Many people of the Li family say they descended from Laozi. For example, the emperors of the Tang dynasty claimed this. This family was known as the Longxi Li lineage (隴西李氏). Although these are questionable, they show Laozi's impact on Chinese culture.

paragraphs: Some philosophers don't think he was real. Some think the Daodejing was "a compilation of Taoist sayings by many hands".

paragraphs: The first mention to Laozi is in the "Records of the Grand Historian" by Sima Qian. In one account, he was an official who lived around the time of Confucius. His name was "Er Li" or "Dan Li", and he wrote some a book with two parts before leaving west. In another, he has the name "Lao Laizi", and the book has 15 parts. In a third, he appears as a royal astrologer named "Lao Dan" living at the time of Duke Xian during the Qin Dynasty. The oldest Daodejing writing comes from around 375 BCE.

paragraphs: According to traditional accounts, Laozi worked as the Keeper of the Archives (librarian) during the Zhou. He was able to study the works of the Yellow Emperor and other classics. Laozi never opened a school but still had many students. There is a story of his meeting with Confucius (most famously in the "Zhuangzi" ).

paragraphs: He may have come from the village of Chu Jen in Chu.

paragraphs: Taoist myths state that Laozi was born when his mother looked at a falling star. He remained in her womb for 62 years while his mother was leaning against a plum tree. The Chinese name Li 李 is the Chinese character for "plum". Laozi was said to have been born as a grown man with a full grey beard and long ears, symbols of wisdom and long life. Other myths state that he was reborn 13 times after his first life during the days of Fuxi. In his last birth as Laozi, he lived 999 years and spent his life traveling to reveal the "Tao".

paragraphs: In accounts where Laozi married, he was said to have had a son named Zong. They are separated when Zong is a child. Zong became a famous soldier and defeated many enemies. Laozi was teaching the Dao, and Zong learns Laozi is his father. Laozi says it is better to treat a beaten enemy with respect and that disrespect to the dead would cause his enemies to seek revenge. So Zong orders his soldiers to bury the enemy dead and hold funeral mournings. Lasting peace is then made.

paragraphs: Sima Qian says Laozi was tired of the moral decay in Chengzhou. The kingdom was declining. He traveled west and lived on the frontier until 80. He was recognized by the guard Yinxi at a western gate. Yinxi asked Laozi to write his wisdom. This became the Daodejing. But the present version of the text includes additions from later periods. In some versions of the tale, Yinxi liked the work so much that he became a student and left with Laozi, never to be seen again. In others, the "Old Master" traveled all the way to India and was the teacher of Siddhartha Gautama, the Buddha. Others say Laozi was the Buddha himself.

paragraphs: A seventh-century work, the "Sandong Zhunang" ("Pearly Bag of the Three Caverns"), said Laozi pretended to be a farmer when reaching the western gate, but was recognized by Yinxi, who asked to be taught by the great master. Yinxi wanted to find the "Tao" and said his long study of astrology allowed him to recognize Laozi. Yinxi was accepted by Laozi as a student. This shows the testing a seeker must undergo before being accepted as a student of a master.

paragraphs: Yinxi then trains. After completing the training, the two go to the western lands of the barbarians. They reached the highest religious rank in medieval Taoism called "Preceptor of the Three Caverns". Laozi is the perfect Taoist master and Yinxi is the ideal Taoist student. Laozi is the living"Tao" personified, teaching others for salvation.

paragraphs: The story of Laozi became religious since the Han dynasty. As Taoism became more popular, Laozi was worshipped as a god. The Way of the Celestial Masters became the first Taoist sect. Later Taoists view Laozi as the "Dao" in human form. Religious Taoism says that Laozi did not disappear after writing the Daodejing but spent his whole life traveling and revealing the Dao to others.

paragraphs: Laozi is traditionally regarded as the founder of Taoism. Popular Taoism typically presents the Jade Emperor as the main deity. Intellectual Taoists, such as the Celestial Masters sect, usually present Laozi ("Laojun", 老君, "Lord Lao") and the Three Pure Ones at the main gods.

paragraphs: Laozi is traditionally regarded as the author of the "Daodejing", but this is disputed. It is one of the most significant books in Chinese cosmogony. Like other ancient Chinese philosophers, Laozi often explains his ideas using paradox, analogy, ancient sayings, repetition, rhyme, and rhythm. In fact, the whole book can be read as an analogy: the ruler is the self, and the others and empire are the body, senses, and desires.

paragraphs: The "Daodejing" says the "Dao" is the source and ideal of all existence: it is unseen, very powerful but also very humble, being the root of all things. People have desires and free will. Many act "unnaturally", breaking the natural balance of the Dao. The Daodejing intends to lead students to "return" to their natural state, in harmony with Tao. Taoism views them language as biased and artificial and shows this through paradoxes.

paragraphs: Another example: technology may give a false sense of progress. Laozi says not to reject technology, but instead seek the calm state of "wu wei" (無爲), without desires. Laozi says rulers should keep their people ignorant or simple-minded. This may be political advice, but it could also be religious. The text uses terms like "valley spirit" ("gushen") and "soul" ("po").

paragraphs: "Wu wei" literally "non-action" or "not acting", is an important concept. The concept is multifaceted, and this is shown by how it can mean many different things and be translated in multiple ways; it can mean "not doing anything", "not forcing", "not acting" (as in movies or drama), "creating nothingness", "acting spontaneously", and "flowing with the moment".

paragraphs: It is used to explain "ziran" (自然), or harmony with the "Tao". It says all ambition originates from the same source. Laozi used the term to mean simplicity and humility as key virtues, in contrast to selfishness. Politically, it means avoiding war, harsh laws and heavy taxes. Some Taoists see a connection between "wu wei" and esoteric practices, such as "zuowang" (坐忘, "sitting in oblivion", emptying the mind of thought) found in the Zhuangzi.

paragraphs: Laozi and Zhuangzi influenced many people throughout Chinese history. Zhuangzi was Laozi's most famous follower. Zhuangzi had a great deal of influence on Chinese scholars, bureaucrats, and culture. Politicians have used Laozi's philosophies to deny serving their ruler. They valued humility in leadership and limited government. This was either out of morality or for their own political means. Some anti-authoritarian movements used Laozi teachings to represent the power of the weak.

paragraphs: Laozi supported limited government. Left-libertarians have been influenced by Laozi. In his 1937 book "Nationalism and Culture", the anarcho-syndicalist writer Rudolf Rocker praised Laozi's "gentle wisdom" and understanding that sometimes political power opposed culture and the community. In his 1910 article for the "Encyclopædia Britannica", Peter Kropotkin said Laozi was one of the earliest supporters for anarchism. Many anarchists like Ursula K. Le Guin have used Laozi to justify their beliefs. Le Guin writes that Laozi "does not see political power as magic. He sees rightful power as earned and wrongful power as usurped... He sees sacrifice of self or others as a corruption of power, and power as available to anyone who follows the Way. No wonder anarchists and Taoists make good friends."

paragraphs: Economist Murray Rothbard suggested that Laozi was the first libertarian, comparing Laozi's ideas to Friedrich Hayek's theory of spontaneous order. James A. Dorn agreed, arguing that Laozi like many liberals "argued that minimizing the role of government and letting individuals develop spontaneously would best achieve social and economic harmony." David Boaz quotes the "Daodejing" in his 1997 book "The Libertarian Reader". Philosopher Roderick Long argues that libertarianism in Taoism actually borrowed from earlier Confucian writers.


title: Brass

paragraphs: Brass is an alloy of copper and zinc. Some types of brass are called bronzes.

paragraphs: Brass has a golden appearance. It is harder than pure metals and resists corrosion. It costs more than zinc.

paragraphs: Brass is more malleable than bronze or zinc. The melting point of brass can be 900 to 940 °C or 1,650 to 1,720 °F, depending on what it is made of. The density of brass is 8.4 to 8.73 g/cm (0.303 to 0.315 lb/cu in).

paragraphs: Today, almost 90% of all brass alloys are recycled. Brass is not ferromagnetic. Brass scrap is collected and transported to the foundry. In the foundry, it is melted and recast into billets. The billets are heated and streched into the form and size that is wanted.

paragraphs: Brass will corrode when it is exposed to moisture, chlorides, acetates, ammonia, and some acids.

paragraphs: There are many brass alloys. They include:


title: Body

paragraphs: A body is the physical material of a person or organism. It is only used for organisms which are in one part or whole. There are organisms which change from single cells to whole organisms: for example, slime moulds. For them the term 'body' would mean the multicellular stage. Other uses:

paragraphs: The body of a dead person is also called a corpse or "cadaver". The dead bodies of vertebrate animals and insects are sometimes called "carcasses".

paragraphs: The human body has a head, neck, torso, two arms, two legs and the genitals of the groin, which differ between males and females.

paragraphs: The study of the workings of the body is physiology.

paragraphs: Here are the names of the body parts of a woman and a man.

paragraphs: The word body is sometimes used in other ways. For example, a lake is a body of water. The laws on a topic are a "body of law".


title: Alloy

paragraphs: An alloy is a uniform mixture. It is made up of two or more chemical elements, of which at least one is a metal. An alloy has properties different from the metals it is made of.

paragraphs: Most alloys are made by melting the metals, mixing them while they are liquid to form a solution, then leaving them to cool and turn solid again.

paragraphs: Combining a pure metal with one or more other metals or non-metals often makes it better. For example, steel is an alloy made from iron but it is stronger than iron. Physical properties like density, reactivity and electrical and thermal (heat) conductivity may not be much different than the elements (substances) which make the alloy. But, properties like strength can be very much different.

paragraphs: The first alloy to be discovered was Bronze. Bronze is made from copper and tin. Bronze was discovered a very long time ago in the prehistoric period. Then, bronze was being used for making tools and weapons. This period was known as Bronze Age. But, later better alloys were discovered which replaced bronze for making tools and weapons. Now, bronze is used for making ornaments, statues, and bells. Brass is another alloy made from copper and zinc.

paragraphs: Melting point is the temperature at which a solid changes to liquid. Most alloys do not have a single melting point. They have a melting range in which the alloy is a mixture of solid and liquid stages. The temperature at which melting just starts is called solidus and the temperature at which the melting is just finished is called liquidus.

paragraphs: The term alloy means a mixture of atoms in which the main substance or the primary constituent is a metal. This primary metal is called the "base" or "matrix".

paragraphs: If an alloy has only two types of atoms, like copper-nickel alloy, then such an alloy is called "binary alloy". If an alloy has three types of atoms, like iron, nickel and chromium, then it is called a "ternary alloy". An alloy with four types of atoms is called a "quaternary alloy" and an alloy with five types of atoms is called a "quinary alloy".

paragraphs: Different varieties or forms of alloys can be made from the same constituent materials (substances from which the alloy is formed). These different forms or varieties can be formed by using different amounts of the constituents. The whole range of possible varieties of an alloy is called a "system". All the forms of alloy having only two constituents are called a "binary system". All forms of an alloy having three constituents are called a "ternary system".


title: Material

paragraphs: Material is what everything that you can touch is made of. Even material that is too small to touch, is called material. We use materials to make things. We can also call material "physical substances."

paragraphs: "Raw" material is materials such as ores which we can clean and mix with other materials to make another material like steel, for example. Cotton is a raw material used to make textiles, which are materials to make clothes.


title: Brain

paragraphs: The brain is the part of the body which lets animals make sense of things. It gets input from sense organs, and changes behavior in response to this information. In humans, the brain also controls our use of language, and is capable of abstract thought. The brain is the main control centre of the whole body. The brain is made up of a special type of cells. They are connected with each other and with the nerves in our body. In all animals the delicate brain is protected in some way. In ourselves, and all vertebrates, it is protected by the bones of the skull.

paragraphs: The brain does the thinking, learning, and feeling for the body. For humans, it is the source of consciousness. The brain also controls basic autonomic body actions, like breathing, digestion, heartbeat, that happen automatically. These activities, and much else, are governed by unconscious functions of the brain and nervous system. All the information about the world gathered by our senses is sent through nerves into the brain, allowing us to see, hear, smell, taste and feel things. The brain processes this information, and we experience it as pictures, sounds, and so on. The brain also uses nerves to tell the body what to do, for example by telling muscles to move or our heart to beat faster.

paragraphs: This is generally true but some activity is caused by the spinal cord directly, for example, reflex actions do not involve the brain. In lower animals, a good deal is done without their brain being involved.

paragraphs: All vertebrates have brains and, over time, their brains have evolved to become more complex. Some simple animals, however, like sponges, do not have anything like a brain. Segmented invertebrates have ganglions in each segment, and a ring of nervous tissue around the alimentary canal at the front. This acts to bring sense data from the front into play with the movement of the body.

paragraphs: In mammals, the brain is made of three main parts: the cerebrum, the cerebellum and the brainstem. The surface of the cerebrum is the cerebral cortex, which all vertebrates have. Mammals also have an extra layer, the neocortex. This is the key to the behaviour which is typical of mammals, especially humans.

paragraphs: The cortex has sensory, motor, and association areas. The sensory areas are the areas that receive and process information from the senses. The motor areas control voluntary movements, especially fine movements performed by the hand. The right half of the motor area controls the left side of the body, and vice versa. Association areas produce a meaningful experience of the world, and supports abstract thinking and language. This enables us to interact effectively. Most connections are from one area of the cortex to another, rather than to subcortical areas; The figure may be as high as 99%.

paragraphs: The cerebellum coordinates muscles so they work together. It is also the centre of maintaining position and balance, a vital part of movement helping with simple motor skills.

paragraphs: The brain stem is at the back of the brain (actually underneath it in humans). It joins the rest of the brain with the spinal cord. It has lots of different parts that control different jobs in the body: for instance, the brain stem controls breathing, heartbeat, sneezing, eye blinking, and swallowing. Body temperature and hunger are also controlled by parts of the brain stem.

paragraphs: The volume of the human brain (relative to the size of the whole body) is very large, compared to that of most other animals. The human brain also has a very large surface (called cortex) for its size, which is possible because it is very wrinkled. If the human cortex were flattened, it would be close to a square meter in area. Some other animals also have very wrinkled brains, such as dolphins and elephants. Here is a rule of thumb: the larger an animal is, the larger its brain will be. Even allowing for that, the human brain, and in particular the neocortex, is very large. We know it increased in size four-fold over the last several million years of evolution. There are ideas about why this happened, but no-one is quite sure. Most theories suggest complex social activity and the evolution of language would make a larger brain advantageous. As an additional note, Einstein's brain weighed only 1,230 grams, which is less than the average adult male brain (about 1,400 grams). The detailed organisation of a brain obviously matters, but in ways which are not understood at present.

paragraphs: A human brain accounts for about 2% of the body's weight, but it uses about 20% of its energy. It has about 50–100 billion nerve cells (also called neurons), and roughly the same number of support cells, called "glia". The job of neurons is to receive and send information to and from the rest of the body, while glia provide nutrients and guide blood flow to the neurons, allowing them to do their job. Each nerve cell has contact with as many as 10,000 other nerve cells through connections called synapses.


title: Neuron

paragraphs: A neuron (or neurone) is a nerve cell that carries electrical impulses. Neurons are the basic units of our nervous system.

paragraphs: Neurons have a cell body ("soma" or "cyton"), dendrites and an axon. Dendrites and axons are nerve fibers. There are about 86 billion neurons in the human brain, which is about 10% of all brain cells. The human brain has about 16 billion neurons in the cerebral cortex. The neurons are supported by glial cells and astrocytes.

paragraphs: Neurons are connected to one another, but they do not actually touch each other. Instead they have tiny gaps called synapses. These gaps are chemical synapses or electrical synapses which pass the signal from one neuron to the next.

paragraphs: There are three classes of neurons: motor neurons, sensory neurons and interneurons.

paragraphs: Mature neurons never divide: that is the general rule. They do not undergo cell division. In most cases, neurons are generated by special types of stem cells. A type of glial cell, called astrocytes, have also been seen to turn into neurons. In humans, neurogenesis (the origin of new nerve cells) largely ceases during adulthood but in two brain areas, the hippocampus and the olfactory bulb, there is strong evidence for substantial numbers of new neurons.

paragraphs: The largest part of the human brain by far is the neocortex. It has at least~10 neurons which stay with us from cradle to grave.


title: Middle East

paragraphs: The Middle East, or West Asia and Egypt, is an area of land and group of countries in Southwest Asia and North Africa. Today, people usually call these countries "Middle Eastern" since they are in the Eastern Mediterranean or west of Central Asia.

paragraphs: Sometimes, people also include countries in North Africa and in South-central Asia as part of a Greater Middle East.

paragraphs: Ancient civilizations began in the Fertile Crescent in the Middle East. These were Sumer, Babylonia and Assyria in the area called Mesopotamia, and Ancient Egypt. The three Abrahamic religions that believe in one God also came from the Middle East. Judaism and Christianity began in ancient Israel and Islam began in Arabia.

paragraphs: Today, the Middle East is very important because much of the petroleum that other countries use comes from here. There are also many arguments and wars, such as the conflict between Sunni and Shia, the Israeli-Palestinian conflict, and the Syrian civil war.


title: Warsaw

paragraphs: Warsaw (In Polish: "Warszawa") is the capital of Poland in Masovian Voivodeship. It is also the biggest city in that country. There are about 2,000,000 people living there (1,726,581 as of 31 March 2014). People from Warsaw are called "Varsovians".

paragraphs: There are other names for Warsaw. For example, (Latin, Spanish) and "Varsóvia" (Portuguese), (French), (Italian), (German, Dutch), /"Varshe" (Yiddish), (Lithuanian), (Hungarian) and "Varšava" (Czech)

paragraphs: Warsaw is near the middle of Poland on both sides of the Vistula river, and about 350 km (225 miles) from the Baltic Sea. It is about 100 m (325 ft) above sea level. Warsaw has a humid continental climate ("Dfb" in the Koeppen climate classification).

paragraphs: Warsaw is home to four universities and 62 colleges, and many theatres and art galleries.

paragraphs: People began living here in the 13th century. By the 15th century, Warsaw had grown enough to be called a city. It became the capital of Poland in 1596.

paragraphs: The city was destroyed several times in its history, but every time it was rebuilt. The most important of these times was during the Second World War. Poland had been occupied by Germany between 1939 and 1944. On 1 August 1944, the people of Warsaw started fighting to free their city.

paragraphs: There are lot of attractions in the capital of Poland. The most famous monument of Warsaw is Palace of Culture and Science. There is a palace in Wilanów. The king of Poland John III Sobieski lived there. Many people like going to the Museum of Warsaw Uprising. The uprising started in 1944 during World War II


title: Hindu–Arabic numeral system

paragraphs: The Hindu–Arabic numeral system, sometimes known as Hindu–Arabic numbers, is the system of numbers used by almost all the world today. It is a positional notation system. This system has ten basic symbols, they are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. It represent numbers in the decimal number system. The Hindu–Arabic numeral system was first developed by the Hindus. Later, It was introduced to the western world by the Arabs. The Hindu–Arabic numeral system is one of the few numeral systems that use a place value system. This system is now commonly used all over the world.

paragraphs: They originated in India in the 6th or 7th century and were introduced to Europe through the writings of Middle Eastern mathematicians, especially al-Khwarizmi and al-Kindi, about the 12th century. They are very different from previous methods of counting, such as the abacus, and paved the way for the development of algebra. In the past many other systems were used.


title: Point (geometry)

paragraphs: A point is a precise position in space. Imagine touching a piece of paper with a sharp pencil or pen, without making any sideways movement. We know where the point is, but it has no size to speak of.

paragraphs: In geometry, a point has no size, but has a position. This means it has no volume, area or length. We usually represent a point by a small cross 'X' or by a small dot (a small, round shape). Points are always labelled by capital letters (A, B, C...X, Y, Z). It is one of the most fundamental but undefined terms in geometry.


title: Line

paragraphs: A line is the path of one point moving. A line has length but no width. A line is a type of geometric figure.

paragraphs: A line is made up of an endless number of points.

paragraphs: A "line segment" is part of a line. Here is an example of a straight line segment:

paragraphs: A line can be straight or curved. The word "line" usually means a "straight line". A straight line is the shortest distance between two points. A straight line is the line traced by a point moving in a direction that does not change.

paragraphs: A "curved line" is sometimes called a curve. The edge of a circle is not straight and is an example of a curve.

paragraphs: Lines can get their names from any two points on the line. For example, if a line contains two distinct points, named formula_1 and formula_2, then the line can be called either formula_3, or formula_4.

paragraphs: Sometimes, lines are also named with just one symbol. In which case, a letter such as formula_5 might be used.


title: Plane (mathematics)

paragraphs: A plane is a perfectly flat surface extending in all directions. It can be thought of as the ceiling of a room, only extended into all directions infinitely. A plane has two dimensions: length and width. All planes are flat surfaces. If a surface is not flat, it is called a "curved surface".

paragraphs: The tool "plane" can be used to create a flat, level surface like the mathematical plane—hence the name.

paragraphs: In geometry, a plane is made up of an infinite number of lines (or points). It has no depth. It is absolutely flat and infinitely large.

paragraphs: A "plane figure" is part of a plane. It is named by the capital letters (such as A, B, C, ...X, Y, Z) that are put at its corners. Sometimes, a single capital pi formula_1 is also used to refer to a plane. A plane can also be named after three points that are not all on the same line.

paragraphs: In mathematics, a plane is a fundamental two-dimensional object. Intuitively, it looks like a flat infinite sheet of paper. There are several definitions of the plane. They are equivalent in the sense of Euclidean geometry, but they can be extended in different ways to define objects in other areas of mathematics. The only two-dimensional figure in our three-dimensional world is a shadow.

paragraphs: In some areas of mathematics, such as plane geometry or 2D computer graphics, the whole space in which the work is carried out is a single plane. In such situations, the definite article is used: "the plane". Many fundamental tasks in geometry, trigonometry and graphing are performed in the two dimensional space, or in other words, in the plane.

paragraphs: A plane is a surface such that, given any three distinct points on the surface, the surface also contains all of the straight lines that pass through any two of them.

paragraphs: One can introduce a Cartesian coordinate system on a given plane in order to label every point on it with a unique ordered pair, which is composed of two numbers and is the coordinate of the point.

paragraphs: Within any Euclidean space, a plane is uniquely determined by any of the following combinations:


title: Angle

paragraphs: When two straight lines come together, they make an angle. The two lines are called the "sides" of the angle, and they meet at a point. A flat surface (called a plane) also forms an angle when it meets another.

paragraphs: To represent an angle, Greek letters such as formula_1 (alpha), formula_2 (beta), formula_3 (gamma) and formula_4 (theta) are sometimes used. An angle indicates the space between its sides, or the amount of rotation needed to make one side coincide the other.

paragraphs: To measure the size of an angle, we use units called degrees. A degree is a standard unit and we use the symbol ° after a number to show that it is a number of degrees. We can use a decimal number or a fraction for part of a degree, but a degree can also be divided into 60 minutes (1° = 60'), and a minute can be divided into 60 seconds (1' = 60"). So 22.5°, 22° and 22° 30' are all the same angle.

paragraphs: In mathematics, angles can also be (and often are) measured in radians instead of degrees, by using the conversion factor formula_5 (for example, formula_6). Yet another unit of angle is gradian, with formula_7.

paragraphs: Angles are studied in geometry, where an angle where edges meet is often called a vertex. For example, the three sides of a triangle are its "edges" and two of the edges meet at each "vertex". Similarly, two of the six sides (or "faces") of a cube meet at each of its twelve edges, and three edges meet at each of its eight corners (or vertices, which is the plural version of "vertex").

paragraphs: An acute angle is an angle less than 90° (but more than 0°). A right angle is an angle equal to 90°. An obtuse angle is an angle greater than 90° but less than 180°. A straight angle (or straight line) is an angle equal to 180°. A reflex angle is an angle greater than 180° (but less than 360°).

paragraphs: Supplementary angles are two angles with the sum equal to 180°, and complementary angles are two angles with the sum equal to one right angle (90°). On the other hand, two angles that sum to one full circle (360°) are sometimes called explementary angles, or conjugate angles.

paragraphs: People usually use a protractor to measure and draw angles. Sometimes, people use a 360° protractor to measure angles.


title: Lists of tropical cyclone names

paragraphs: Tropical cyclones and subtropical cyclones are named by various warning centers to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin. Generally once storms produce sustained wind speeds of more than , names are assigned in order from predetermined lists depending on which basin they originate. However, standards vary from basin to basin: some tropical depressions are named in the Western Pacific, while tropical cyclones must have a significant amount of gale-force winds occurring around the centre before they are named in the Southern Hemisphere.

paragraphs: Before the formal start of naming, tropical cyclones were named after places, objects, or saints' feast days on which they occurred. The credit for the first usage of personal names for weather systems is generally given to the Queensland Government Meteorologist Clement Wragge, who named systems between 1887 and 1907. This system of naming weather systems subsequently fell into disuse for several years after Wragge retired, until it was revived in the latter part of World War II for the Western Pacific. Formal naming schemes and naming lists have subsequently been introduced and developed for the Eastern, Central, Western and Southern Pacific basins, as well as the Australian region, Atlantic Ocean and Indian Ocean.

paragraphs: Within the North Atlantic Ocean, tropical or subtropical cyclones are named by the National Hurricane Center (NHC) when they are judged to have intensified into a tropical storm with winds of at least 65 km/h, (40 mph). Six lists of names are used in alphabetical order, and maintained by the World Meteorological Organization with them rotating on a yearly basis. Significant tropical cyclones have their names removed from the lists with a replacement name selected at the next World Meteorological Organization Regional Association IV Hurricane Committee meeting. If all of the names on a list are used, storms are named after the letters of the Greek alphabet (Alpha, Beta, Gamma, etc.). Greek names, unlike the names in the regular lists, cannot be removed. If a storm ever reached the magnitude that might otherwise have led to retirement, the storm would be listed with the retired names with a footnote indicating the Greek letter would still be available for future storms.

paragraphs: The names used this year (2019) will be reused again in 2025. (if none of them are retired)

paragraphs: Within the Eastern Pacific Ocean two offices of the United States National Weather Service assign names to tropical cyclones when they are judged to have intensified into a tropical storm with winds of at least 65 km/h, (40 mph). Tropical cyclones that become tropical storms between the coast of Americas and 140°W are named by the National Hurricane Center (NHC), whilst tropical cyclones intensifying into tropical storms between 140°W and 180° are named by the Central Pacific Hurricane Center (CPHC). Significant tropical cyclones have their names retired from the lists and a replacement name selected at the next World Meteorological Organization Regional Association IV Hurricane Committee meeting.

paragraphs: When a tropical depression intensifies into a tropical storm to the north of the Equator between the coastline of the Americas and 140°E then it will be named by the NHC. Six lists of names are maintained by the World Meteorological Organization with them rotating on a yearly basis. Significant tropical cyclones have their names retired from the lists with a replacement name selected at the next World Meteorological Organization Regional Association IV Hurricane Committee meeting. If all of the names on a list are used, storms are then named after the letters of the Greek alphabet (Alpha, Beta, Gamma, etc.). Greek names, unlike the names in the regular lists, cannot be retired. If a storm ever reached the magnitude that might otherwise have led to retirement, the storm would be listed with the retired names with a footnote indicating the Greek letter would still be available for future storms.

paragraphs: When a tropical depression intensifies into a tropical storm to the north of the Equator between 140°W and 180° it is named by the CPHC. Four lists of names are maintained by the World Meteorological Organization, rotating without regard to year, with the first name for a new year being the next name in sequence that was not used the previous year. Significant tropical cyclones have their names retired from the lists, with a replacement name selected at the next World Meteorological Organization Regional Association IV Hurricane Committee meeting. The last name to be used from this list was Omeka, whilst the next will be Pewa.

paragraphs: Within the Northwestern Pacific Ocean there are two separate agencies who assign names to tropical cyclones which often results in a cyclone having two names. The Japan national weather service names tropical cyclones should they be judged to have 10-minute sustained wind speeds of 65 km/h, (40 mph), to the north of the equator between the 180° and 100°E. The Philippine national weather service also assigns names to tropical cyclones which move into or form as a tropical depression in their area of responsibility located between 135°E and 115°E and between 5°E-25°E even if the cyclone has had a name assigned to it by the Japanese national weather service.

paragraphs: Tropical cyclones are named from the following lists by the Japanese national weather service, once they become a tropical storm. Names are contributed by members of the ESCAP/WMO Typhoon Committee. Each of the 14 nations or territories submitted 10 names, which are used in alphabetical order, by the English name of the country.

paragraphs: The Philippine national weather service uses its own naming scheme for tropical cyclones in their area of responsibility. PAGASA assigns names to tropical depressions that form within their area of responsibility, and any tropical cyclone that moves into their area of responsibility. Should the list of names for a given year prove to be insufficient, names are taken from a reserve list of names, with the first ten published every year.

paragraphs: Within this basin when a deep depression is judged to have become a Cyclonic Storm it will be named by the Indian national weather service. The list of names were selected between 2000 and 2004 by the countries of the WMO/ESCAP Panel on tropical cyclones, before the actual naming of tropical cyclones began in September 2004.

paragraphs: Within the South-west Indian Ocean, tropical and subtropical depressions that are judged to have 10-minute sustained windspeeds of 65 km/h, (40 mph) or more for at least 6 hours by the national weather service of Reunion Island are usually assigned a name. However it is the Mauritius and Madagascan national weather services who name the systems. The National weather service of Mauritius name the storm should it intensify into a moderate tropical storm between 55°E and 90°E; if the storm should intensify into a moderate tropical storm between 30°E and 55°E then the national weather service of Madagascar assigns the appropriate name to the storm. Tropical cyclones moving into this region from the Australian Region are renamed by the Sub-Regional Tropical Cyclone Advisory Center in Mauritius; however tropical cyclones moving into the Australian region do not get renamed. New name lists are used every year, whilst a name is normally only used once so thus no names are retired.

paragraphs: Within the Australian Region there are five different offices that assign names to tropical cyclones. However, as three of the offices are run by the Australian national weather service, only 3 lists of names are operated. A tropical depression is judged to have intensified into a tropical cyclone if winds reach 65 km/h, (40 mph) and it is clear that gales are occurring more than halfway around the center. Significant tropical cyclones have their names retired from the lists and a replacement name selected at the next World Meteorological Organization Regional Association V Tropical Cyclone Committee meeting.

paragraphs: When a tropical depression intensifies into a tropical cyclone between the Equator and 10°S and between 90°E and 125°E then it will be named by the Indonesian national weather service. Should a tropical low intensify into a tropical cyclone between the Equator and 10°S and between 141°E and 160°E are assigned names by the Tropical Cyclone Warning Center in Port Moresby, Papua New Guinea. Tropical Depressions intensifying into tropical cyclones in all other areas between 90°E and 160°E as well as the Equator and 40°S are named by the Australian national weather service. Should a tropical cyclone pass from one warning center to another it will retain its original name, except when moving into the South-West Indian Ocean where the Mauritius Meteorological Service will rename the system.

paragraphs: When a tropical depression intensifies into a tropical cyclone between the Equator and 10°S and between 90°E - 125°E, it will be named by the Indonesian Weather Service. Names are currently assigned in sequence from list A, while list B is a list of names that will replace names on list A that are retired.

paragraphs: When a tropical low intensifies into a tropical cyclone between 10°S and 40°S and between 90°E - 160°E, then it will be named by one of three Australian national weather service offices in Perth, Darwin, or Brisbane. Starting with Anika, the names are assigned in alphabetical order with the lists used in rotating order without regard to year.

paragraphs: When a tropical low intensifies into a tropical cyclone between the equator and 10°S and between 141°E - 160°E then it will be named by the Papua New Guinea's national weather service. Names from List A are assigned in a random order while list B details replacement names for list A which will be added in the bottom of list A to maintain the alphabetical order.

paragraphs: Within the Southern Pacific a tropical depression is judged to have reach tropical cyclone intensity should it reach winds of 65 km/h (40 mph), and it is evident that gales are occurring at least halfway around the center. Tropical depressions that should intensify into a tropical cyclone between the Equator and 25°S and between 160°E - 120°W are named by the Fiji national weather service. Should a Tropical Depression intensify to the south of 25°S between 160°E and 120°W, it will be named in conjunction with the Fijian national weather service by the New Zealand's national weather service. Significant tropical cyclones have their names retired from the lists and a replacement name selected at the next World Meteorological Organization Regional Association V Tropical Cyclone Committee meeting, whilst tropical cyclones that move into the Australian region will retain its original name.

paragraphs: Tropical cyclone formation is rare within the Mediterranean sea, South Atlantic and to the east of 120W in the Southern Pacific, as a result there are no official naming lists for these areas although in 2004 & 2010 when tropical cyclones formed within the South Atlantic they were named as Catarina and Anita.


title: Lists of astronomical objects

paragraphs: This is a partial list of the various lists of astronomical objects which either exist, or should exist, in Wikipedia.


title: Acid

paragraphs: An acid is a substance that can donate a hydrogen ion (H) (generally speaking, this will be a proton) to another substance. Acids have a pH less than 7.0.

paragraphs: A chemical can donate a proton if the hydrogen atom is attached to an electronegative atom like oxygen, nitrogen, or chlorine. Some acids are strong and others are weak. The weak acids hold on to some of their protons, while the strong acids let go of all of them. All acids will release hydrogen ions into solutions. The amount of ions that get released per molecule will determine if the acid is weak or strong. Weak acids are acids that partially release the hydrogen atoms that are attached. These acids, then, may lower pH by dissociation of hydrogen ions, but not completely. Weak acids generally have a pH value of 4-6 while strong acids have a pH value of 1 to 3.

paragraphs: A base is an acid's "chemical opposite." A base is a substance that will accept the acid's hydrogen atom. Bases are molecules that can split apart in water and release hydroxide ions.

paragraphs: Acids and bases typically exist together in equilibrium. This means that within a sample of an acid, some molecules will give up their protons and others will accept them. Even water is a mixture of an acidic ion, HO (called a hydronium ion) and a basic ion, OH (called a hydroxide ion). A hydronium ion will give up its proton to a hydroxide ion, forming two molecules of HO, which is neutral. This reaction happens continuously in a sample of water, but overall the sample is neutral because there are equal amounts of hydronium and hydroxide in the sample. For most reactions, however, the acids and bases are not present in equal amounts, and this imbalance is what allows a chemical reaction to occur.

paragraphs: Every acid has a conjugate base formed by removing the acid's proton. Hydrochloric acid (HCl), for example, is an acid and its conjugate base is a chlorine anion, or Cl. An acid and its conjugate base are opposite in strength. Since HCl is a strong acid, Cl is a weak base.

paragraphs: Acids can have different "strengths", some are more reactive than others. More reactive acids are often more dangerous.

paragraphs: Acids can have a lot of different properties depending on their molecular structure. Most acids have the following properties:

paragraphs: Acids can burn the skin, the severity of the burn depending on the type and concentration of the acid. These chemical burns require immediate medical attention.

paragraphs: Because acids donate hydrogen ions, all acids must have hydrogen in them.

paragraphs: Acids are important. Nucleic acids, such as DNA and RNA contain the genetic code. These molecules determine many characteristics of an organism, they are passed from the parents to offspring. DNA contains the plans how to build proteins which are made of amino acids.

paragraphs: Fatty acids and fatty acid derivatives are another group of carboxylic acids that play a significant role in biology. These contain long chains of hydrocarbons and a carboxylic acid group on one end. The cell membrane of nearly all organisms is primarily made up of a phospholipid bilayer, a micelle of hydrophobic fatty acid chains with polar, hydrophilic phosphate "head" groups.

paragraphs: In humans and many other animals, hydrochloric acid is a part of the gastric acid secreted within the stomach. It can help hydrolyze proteins and polysaccharides. It can also convert the inactive pro-enzyme, pepsinogen into the enzyme, pepsin. Some organisms produce acids for defense; for example, ants produce formic acid, and octopi produce a black acid called magneta.

paragraphs: Most acids can be found in nature. Some of these include the following:


title: White dwarf

paragraphs: A white dwarf is a compact star. Their matter is squashed together. Gravitation has pulled the atoms close together, and taken off their electrons. The mass of a white dwarf is similar to the mass of the Sun, but its volume is similar to that of the Earth.

paragraphs: White dwarfs are the final evolutionary state of all stars whose mass is not high enough to become a neutron star. Over 97% of the stars in the Milky Way will become white dwarf stars. After the hydrogen–fusing lifetime of a main-sequence star ends, it will expand to a red giant which fuses helium to carbon and oxygen in its core. If a red giant does not have enough mass to fuse carbon, around 1 billion K, inactive carbon and oxygen will build up at its center. After shedding its outer layers to form a planetary nebula, it will leave behind the core, which is the white dwarf.

paragraphs: The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. It is not supported by the heat of fusion against gravitational collapse.

paragraphs: A star like our Sun will become a white dwarf when it has run out of fuel. Near the end of its life, it will go through a red giant stage, and then lose most of its gas, until what is left contracts and becomes a young white dwarf.

paragraphs: White dwarfs were discovered in the 18th century. The first white dwarf star, called 40 Eridani B, was discovered on 31 January 1783 by William Herschel. It is part of a three star system called 40 Eridani.

paragraphs: The second white dwarf was discovered in 1862, but was at first thought to be a red dwarf. It was a small star near the star Sirius. This companion star, called Sirius B, had a surface temperature of about 25,000 kelvin, so it was thought of as a hot star. However, Sirius B was about 10,000 times fainter than the primary, Sirius A. Scientists have discovered that the mass of Sirius B is almost the same as that of the Sun. This means that once, Sirius B was a star similar to our own Sun.

paragraphs: In 1917, Adriaan van Maanen discovered a white dwarf which is called Van Maanen 2. It was the third white dwarf to be discovered. It is the closest white dwarf to Earth, except for Sirius B.

paragraphs: A white dwarf has low luminosity (total amount of light given off) but a very hot core. The core might be 10 K, while the surface is only 10 K.

paragraphs: A white dwarf is very hot when it is formed, but since it has no source of energy, it will gradually radiate away its energy and cool. This means that its radiation, which gives it a blue or white colour at the start, lessens over time. Over a very long time, a white dwarf will cool to temperatures at which it will no longer emit light. Unless the white dwarf gets matter from a companion star or some other source, its radiation comes from its stored heat. This is not replaced.

paragraphs: White dwarfs cool slowly for two reasons. They have an extremely small surface area to radiate this heat from, so they cool gradually, remaining hot for a long time. Also, they are very opaque. The degenerate matter that makes up the bulk of a white dwarf stops light and other electromagnetic radiation, so radiation does not carry away much energy.

paragraphs: Eventually, all white dwarfs will cool down into black dwarfs, so called because they lack the energy to create light. No black dwarfs exist yet because it takes longer than the current age of the universe for a white dwarf to cool down. A black dwarf is what will be left of the star after all of its energy (heat and light) is used up.

paragraphs: White dwarfs may re-ignite and explode as supernovas if they get more material. There is a maximum mass for a white dwarf to remain stable. This is known as the Chandrasekhar limit.

paragraphs: A dwarf might pull in material from a companion star, for example, bringing it over the Chandrasekhar limit. The extra mass would start a carbon-fusion reaction. Astronomers think this re-igniting might be the cause of Type Ia supernovas.


title: Beach

paragraphs: A beach is a landform along the coast of an ocean, sea, lake, or river. It usually consists of loose particles, such as sand, gravel, shingle, or pebbles. The particles of a beach are sometimes biological in origin, such as mollusc shells or bits of coral and sometimes bits of igneous rock, but the most common mineral in beaches is quartz.

paragraphs: Beaches are natural landing and launching places for boats, and landing craft are specially made for beaches.

paragraphs: People often use beaches for recreation. They swim, bask in the sun, or just relax. The most popular beaches have fine white or light-colored sand and warm water to swim in. Beaches are also used for diving or for seeing marine life.

paragraphs: Among the world's most popular and well-known beaches are Aruba (Dutch Caribbean), Long Beach (Canada), Copacabana Beach (Brazil), Hot Water Beach (New Zealand), Megan Bay (St. Thomas), Kailua Beach (Hawaii), Zandvoort Beach (Netherlands), Jeffreys Bay (South Africa) and Bondi Beach (Australia).

paragraphs: Taking holidays on the beach is something of a British cultural export. Early railways in the 19th century took people to places they had never seen before. This tourism was made possible by the industrial revolution. Whole seaside resort towns grew to support visitors, where before there were just villages. Vacations at the sea became common all over the world.

paragraphs: Beaches are never static. They are always being built up or eroded, more quickly than other landforms. Over time the boundary between the land and the sea changes. New Romney, a small town in Kent, is one of the Cinque Ports, a mile from the sea. In Henry VIII's time it was a port on the south coast of England. The growth of Dungeness has cut it off from the sea. Dungeness is a huge shingle beach.


title: Mental illness

paragraphs: A mental illness is an illness of the mind. People with a mental illness may behave in strange ways or have strange thoughts in their view or the view of others. Mental illnesses can affect the day to day functioning of a person.

paragraphs: Mental illnesses develop during the life of a person. This may be linked to genes and experience. What is considered as a mental illness has changed over time. What is considered to be a mental illness may not be one in a different culture. The Diagnostic and Statistical Manual of Mental Disorders (DSM) by the American Psychiatric Association is used around the world.

paragraphs: People with a mental illness sometimes have problems dealing with other people, or struggle with daily functioning. Treatment and certain medications can help people with daily functioning.

paragraphs: In some cases, mental illnesses change the way the brain works. Many conditions which affect the brain are not mental illnesses, as they do not change the way in which people think: Neither epilepsy nor Parkinson's disease is a mental illness, yet both affect the brain.

paragraphs: According to the New Freedom Commission on Mental Health in the United States, the most common type of disability in the United States is major mental illnesses (which include major depression, bipolar disorder, personality disorders, body dysmorphic disorder, schizophrenia, and obsessive-compulsive disorder).

paragraphs: Thirty-three percent of North American adults will have a mental illness in a given year, according to the National Alliance on Mental Illness. But in more than half of these cases, the mental illness is not bad enough to disrupt daily life activities.

paragraphs: There is a genetic basis which makes some people more likely to develop mental illness. A study published in "The Lancet", a medical journal, found the same set of genetic markers in people with five different disorders: schizophrenia, bipolar disorder, autism, major depression, and attention deficit hyperactivity disorder (ADHD).

paragraphs: Some more controversial treatments include

paragraphs: Many counties have laws that permit to treat people against their will.

paragraphs: Even though the media show this differently, studies have shown that people with a severe mental illness are not necessarily violent. Statistically, violence is often caused by factors such as drug abuse, or those related to the personal, social and economic situation.

paragraphs: Findings show that people with a mental illness that live in the community will be victims of violence more often that they will be those starting or spreading it. A study that looked at people diagnosed with "severe mental illness" living in a US inner-city area found that a quarter of them had been victims of at least one violent crime over the course of a year; this proportion was eleven times higher than the average. For people which have been diagnosed with a mental illness it is more difficult to get a trial started, because fewer people believe them, and many people have a prejudice against people with a mental illness.

paragraphs: There are a few specific diagnoses which are defined by conduct problems and violence. These include conditions such as childhood conduct disorder, adult antisocial personality disorder or psychopathy. There are conflicting findings about how much specific symptoms are linked to an increase in violent behaviour. These symptoms include psychosis (hallucinations or delusions) that can occur in disorders such as schizophrenia, delusional disorder or mood disorder. The factors that lead to violent behaviour are more often demographic or economic in nature, such as being young, male, of lower socioeconomic status or of abusing drugs, including alcoholism, to which some people are particularly vulnerable.

paragraphs: Some studies show that disabled people are sometimes treated badly. For example, people with mental illness may deal with ableism. An example of ableism is insults, for example calling a mentally ill person a "retard".

paragraphs: High-profile cases have led to fears that serious crimes, such as homicide, have increased because people with certain mental illnesses are not treated in specialized institutions, but the evidence does not support this conclusion. Violence that does occur in relation to mental disorder (against the mentally ill or by the mentally ill) typically occurs in the context of complex social interactions, often in a family setting rather than between strangers. It is also an issue in health care settings and the wider community.