title: Roman Empire

paragraphs: The Roman Empire was the largest empire of the ancient world. Its capital was Rome, and its empire was based in the Mediterranean. The Empire dates from 27 BC, when Octavian became the Emperor Augustus, until it fell in 476 AD, marking the end of the Ancient World and the beginning of the Middle Ages, or Dark Ages.

paragraphs: The empire was the third stage of Ancient Rome. Rome was first ruled by Roman kings, then by the Roman Republic, then by an emperor.

paragraphs: Many modern lands were once part of the Roman Empire, for example Britain (not Scotland), Spain, Portugal, France, Italy, Greece, Turkey, Germany, Egypt, Levant, Crimea, Switzerland, and the north coast of Africa. The main language of the Roman Empire was Latin with Greek as an important secondary language, especially in the Eastern provinces of the Empire.

paragraphs: The western half of the Roman Empire lasted for about 500 years till the barbarian general Odoacer deposed its final emperor Romulus Augustus. On the other hand, the eastern half, consisting of the Balkans, Anatolia, The Levant and Egypt, continued for about a thousand years more (the Levant and Egypt were lost to the Arabs in the 8th century). The eastern part was called the Byzantine Empire. Its capital was Constantinople, now called Istanbul.

paragraphs: In order to control their large empire, the Romans developed important ideas about law and government. They developed the best army in the world at that time, and ruled by force. They had fine engineering, and built roads, cities, and outstanding buildings. The Empire was divided into provinces, each with a governor plus civil and military support. Letters, both official and private, would constantly go to and from Rome.

paragraphs: Trade was most important for Rome, a city of more than a million people, by far the largest city in the world. They needed, and got, wheat from Egypt, tin from Britannia, grapes from Gaul, and so on. In return, the Romans built provincial capitals into fine cities, protected them from raids by barbarians, and provided education and career opportunities for young people in the provinces, such as jobs in the Roman Army.

paragraphs: In principle, emperors had absolute control, and could do as they pleased. In practice, they faced many difficult problems. They had a staff of what we call 'civil servants' and the advice of the Roman Senate. The emperor had to decide what were the most important issues facing the Empire, and what should be done about them. Most of them tried to do two sorts of thing. One was to do things to improve the life of Romans in peacetime. The other was to fight and defeat Rome's enemies. A wealthy empire always has enemies.

paragraphs: With kings and emperors, a big problem is the order of succession. Kings were sometimes followed by their eldest son, if he was capable of ruling. For Roman emperors, more often it would be an adopted son. It worked like this. The emperor would notice an outstanding young man from one of the best families. He would adopt him as his son. Before he died he would make clear whom he thought should succeed him, by making him a Roman consul, or by stating in his will that the younger man should succeed him. Sometimes this worked; sometimes it did not. Every now and then there would be a civil war between claimants to the throne.

paragraphs: An adopted son or two gave the emperor more choices. Some emperors had no son; some had sons who did not survive. Later on, emperors grew so weak that the Roman army would just pick one of their generals to be the next emperor. This often led to civil war. The life stories of the emperors can be found in List of Roman emperors.

paragraphs: The Romans fought many wars against other countries, and enjoyed watching violent sports. They enjoyed watching races between chariots pulled by horses, and fights between men using weapons (gladiators). Unlike in modern sports, the fighters were often killed in fights. Romans enjoyed these shows in the Colosseum.

paragraphs: The Romans had great civil engineering. They built many large public buildings and villas, aqueducts to carry water, stone bridges and roads. Some of these things can still be seen today. Many famous writers were Romans, including Cicero and Virgil.

paragraphs: The New Testament of the Bible tells about the Romans in the life of Jesus Christ. During Jesus' life, the Romans, who were pagans, ruled his country. Later, several emperors tried to destroy Christianity but they did not succeed. By 312 the emperor Galerius allowed people freedom to follow Christianity, and the next year, a general, Constantine, became emperor and converted to Christianity.

paragraphs: The city of Rome was taken over several times by barbarians, notably in 410 when the Goths sacked the city (looting). The last Western Roman emperor, Romulus Augustus, resigned in 476 . The Roman Empire would last another 1,000 years as the Byzantine Empire in the east.

paragraphs: The main coin of the Roman Empire was the silver denarius. Later denarii were smaller.

paragraphs: Various reasons have been given for the fall of Rome. Edward Gibbon wrote "The Decline and Fall of the Roman Empire" in which he investigated various ideas. Chief among them was (in his opinion) was the effect of Christianity on the ability of the Empire to defend itself militarily.

paragraphs: Other historians blame the unstable system of leadership. In a 50-year period, only 2 out of 22 emperors died a natural death. Most of the emperors were assassinated.


title: Regime

paragraphs: A regime is the leader and other people who run a government of a sovereign state.

paragraphs: There are many kinds of regimes. They can achieve power in many ways. Depending on the time and place and local civics like the electoral system, they can lose power in many ways too. The most common way for a regime to lose power was a coup, invasion or revolution until the 20th century. After that it became very dangerous and difficult to use these methods. Peaceful regime change is usually by an election - this method is now used by more than half the people on the Earth. It is called representative democracy. Such regimes are often called administrations to make it clear they are not dictators, and since the executive branch does not have all the power itself - it may share it with a legislative branch. Also the judicial branch is separate. The courts are not usually considered part of the regime.

paragraphs: However, some things are the same no matter how the regime achieved power:

paragraphs: When many regimes negotiate at the United Nations or World Trade Organization, it does not matter at all how each regime got its power. It matters only that they can agree and make everyone in their country do as the agreement says.

paragraphs: When someone wants a regime to change in another country, they usually are not able to do this by any means other than violence or interfering in its election. This is common if a regime is threatened by another regime.


title: River

paragraphs: A river is a stream of water that flows through a channel in the surface of the ground. The passage where the river flows is called the river bed and the earth on each side is called a river bank. A river begins on high ground or in hills or mountains and flows down from the high ground to the lower ground, because of gravity. A river begins as a small stream, and gets bigger the farther it flows.

paragraphs: The start of a river only counts when lava is in form "source" or "head water". The part of the river that is near the source is called a 'young' river. A young river is often in a V-shaped river bed, and flows quickly downhill over stones, and around big rocks. Young rivers often have lots of small waterfalls and rapids. As the rivers travel downhill they begin to erode the ground taking small bits of soft rock and soil.

paragraphs: The middle part of a river is called a mature river. A mature river makes a riverbed that is U-shaped. It might be very deep and run fast. It sweeps over small rocks and boulders, and makes big turns around hills and mountains. It is much wider than a young river, but not as wide as an old river. To cross over a mature river, people use bridges. Many cities and towns are built on the banks of mature rivers. Many farms that keep animals such as dairy cows, horses and sheep are along mature rivers because the animals can drink from the river every day.

paragraphs: A river usually ends by flowing into an ocean, a lake or a bigger river. The place where the river flows out into a bigger body of water is called the 'mouth' of the river.

paragraphs: As a river flows towards its mouth, the countryside around the river often changes from hilly to flat. As it flows over the flat land the river becomes wider and slower. A wide slow river is called an 'old river'. An old river often floods across the land after there is lots of rain at the headwaters. An old river slowly builds up its banks on either side; the high banks are called levees. An old river often meanders (twists and turns), and sometimes, after a flood, it leaves lakes behind which are called ox-bows or billabongs. Old rivers are the most useful type of river for growing crops. Corn, rice, fruit, cotton, hay, tobacco and sugar are some of the crops that are grown near old rivers.

paragraphs: The shape of the mouth depends on the conditions of the sea where it flows. If there is a strong tide where the river meets the sea, the river forms an estuary. An estuary is a wide, funnel-like mouth of the river. The fresh water of the river mixes slowly with the salt water, becoming brackish water – somewhat salty water. Many kinds of fish, clams, molluscs and other sealife live at estuaries. Many of the world's largest cities and harbours are at estuaries.

paragraphs: Where a river flows out to the sea, it sometimes flows very slowly through sandy or muddy land, making lots of little islands as it flows. The main stream of the river gets broken into many parts that spread out into a triangle shape like the Greek letter delta. When this happens, it is called the delta of the river. Deltas are often places that are not good for towns or farms but are very good for birds and other wildlife and fishing. Deltas are often made into wildlife reserves. Not all rivers have deltas. There are famous deltas on the Nile River, the Amazon River, the Mekong River, the Mississippi River and the Danube River.

paragraphs: Some rivers flow underground through caves. Underground rivers form in places where there are lots of cracks in the rocks above, so that in rainy weather, the water runs downs and collects in small underground streams. Sometimes the underground water trickles or gushes out of the ground to form a small spring of water. In other places, where there are caves, the small underground streams run together to form a river. The river can sometimes run through deep wide underground caverns. While many underground rivers flow gently, some underground rivers flow fast and have rapids, particularly after heavy rain. Many underground rivers flow out through a cave mouth to become an ordinary river.

paragraphs: The water in rivers is "fresh water" that has come from rain, snow and from underground streams. It can usually be drunk safely by people unless it is too dirty because of mud or human pollution. People and animals need fresh water to drink, so they often live by the side of a river.


title: Right angle

paragraphs: A right angle is an angle with a measurement of 90 degrees. When two lines cross each other so that all the angles have the same size, the result is four right angles. The top of the letter T is at right angles to the vertical line. Walls of buildings are usually at right angles to the floor. Two things that are at right angles are called "perpendicular" or "orthogonal". This is expressed using the formula_1 symbol (such as in formula_2).

paragraphs: Planes (flat surfaces) can also meet at right angles. In a building, a wall and a floor are said to be perpendicular to each other, and they have a right angle. It also can be called a square angle.


title: Reward

paragraphs: A reward is getting something good for doing a given task. It needs someone who has the power to give the good thing. It is the opposite of punishment.

paragraphs: Ideas like risk and reward, reward and punishment are based on the idea that people do things, or avoid doing things, to get rewards. In psychology there is another idea that this is not true. This other idea says that training (conditioning) and emotions (affective factors) are much more important than the rewards or punishments given by others.

paragraphs: In trying to catch criminals and other bad people, the government often offers money to people. This money is given to people who may capture the criminal, or give information that helps the police catch them. For example, after the Eureka Stockade rebellion in Ballarat, Victoria in 1854, the government offered a big reward of 400 pounds for the capture of the people who had started it.

paragraphs: In 2001, the US government offered a big reward of 2.5 million dollars for help in capturing the person who had sent anthrax in letters to a newspaper journalist and 2 senators. Anthrax is a disease which can kill people.


title: Ranch

paragraphs: A ranch is a large farm for raising cows, horses, sheep or other livestock. The word "ranch" is from the Spanish word "rancho". It is used in American and Canadian English.

paragraphs: A ranch may be on private or public land. The desert areas of the western United States have many ranches, because there is much land that is not very good for crops. There are also many in desert areas of Australia, where they are called stations. Someone who takes care of the livestock may be called a stockman or cowboy.


title: Sport utility vehicle

paragraphs: A sport utility vehicle (SUV) is a type of vehicle. It is built as a rugged vehicle for cargo and passenger carrying. Originally SUVs were not designed to be fuel efficient but modern designs are getting better fuel mileage. In 2014 US sales of SUVs were over five million vehicles.

paragraphs: The typical SUV is a two-box design. Unlike a pickup truck (US term) that has an open cargo box the SUV has an enclosed cargo/passenger compartment. It has upright seating for five to seven passengers. It has an open interior with no trunk. It is often built on a pickup truck chassis for towing capacity, and usually has four wheel drive. Only about 15% of SUV owners ever go off-road. According to Jeep Wrangler brand manager Kevin Metz, 60% of Jeep Wrangler owners go off-road while around 80% of Rubicon owners do.

paragraphs: A similar class of vehicle is the CUV crossover, a common UK term. That is built on a car chassis. Often it uses a Unibody chassis instead of the heavier body-on-frame design of SUVs. Crossover vehicles often have all-wheel-drive instead of four-wheel drive. Crossovers are usually lighter than SUVs and get better fuel mileage. In general, when referring to an SUV, many include crossovers. However it is incorrect to refer to an SUV on a truck frame as a crossover.

paragraphs: Early SUVs were built like light commercial and light wheeled military utility vehicles. Famous examples were the World War Jeep (US), and the Land Rover (UK).

paragraphs: The term "sport utility vehicle" came into popular use in the late 1980s. Until then, they were marketed as station wagons. An early example of marketing a civilian off-roader as a "sports utility" is the two-door pickup version of the 1966 Ford Bronco. In 1974 Jeep used the term "sport(s) utility vehicle" exactly in their brochures for the 1st generation Jeep Cherokee.

paragraphs: Many kinds of off-roading in the USA are centered around SUVs.

paragraphs: There are many reasons why SUVs have become popular. One reason is the comfort of their large cabins. Many models can carry almost as much as a minivan. Another reason is the driver sits higher than other cars, giving better all-round vision. SUVs with truck frames are heavier (sometimes much heavier) than standard cars. Their size gives them an image of safety.

paragraphs: Men aren't the only targets of SUV and CUV ads. For example, some ads for the Subaru Forester are deliberately aimed at women buyers. Roughly 35 to 40 percent of SUV buyers are women. Ads commonly show SUVs driving across boulders or perched on a mountain peak. Advertisers know that one important reason many people buy SUVs is image.

paragraphs: Practicality for larger families is a consideration. Not only can the vehicle take a family of five or six, plus luggage, but also the family dog (who often has a special compartment at the back). On the other hand, the vehicle doesn't fit standard parking spaces. That can be quite a problem in, for example, the UK. The alternative, when groups of more than four travel, is to take more than one standard size car.

paragraphs: In Australia and Europe SUVs are often called 4 wheel drives (4X4) or 4WDs.


title: Substance

paragraphs: Substance ["sub'-stuns"] is the material, or matter, of which something is made. Substances are physical things that can be seen, touched, or measured. They are made up of one or more elemental parts. Iron, aluminium, water and air are examples of substances.

paragraphs: The main problem of a clear definition of what the substance is that if, for example, to consider not just the universe (cosmos), being and non-being, and in general all, the question arises, what is the constant basic principle (attribute) is the basis of the substance, which generally consists of all (that is, matter, mind, senses, space, soul, and so on).

paragraphs: The Latin word substantia - a translation of the Greek word for the essence (ousia), and in Latin to describe the essence of using the word essentia. In ancient philosophy substance is treated as a substrate, the first principle of all things (for example, "water" of Thales, the "fire" of Heraclitus).

paragraphs: In modern times, the concept of substance is treated and spread widely. The first view is connected with an ontological understanding of substance as ultimate bases being (Francis Bacon, Benedict Spinoza, Gottfried Wilhelm Leibniz). Central category of metaphysics in philosophy substance is identified as with God and with nature and determined as the cause of itself (Latin causa sui). The main characteristics (attributes) of a substance from Benedict Spinoza are thinking and stretch. By analogy with the philosophy of Benedict Spinoza substance considered in the light of the concept of René Descartes and Leibniz. The first substance is a unity of subject and object, and the second - the same atoms are simple beings who lose their stretch, but receive attribute aspirations (Fr. appetition) and multiplicity. Thanks Leibniz substance begins to associate with matter.

paragraphs: The second point of view on the substance - an epistemological understanding of the concept, its capabilities and the need for scientific knowledge (John Locke, David Hume). Immanuel Kant believed that the law under which any change in the substance of events and the number of stored it in nature remains the same, can be attributed to the "analogies of experience." Georg Wilhelm Friedrich Hegel defined substance as the integrity of changing, transient side of things, as a "major step in the development of the will." For Arthur Schopenhauer substance - matter for David Hume - a fiction, the coexistence properties.


title: Symbol

paragraphs: A symbol is a drawing, shape, or object that represents an idea, object, or amount of something.

paragraphs: The most common symbols are letters, which are symbols of words and sounds. A symbol can be an actual object (such as the cross, a symbol of Christianity or a scepter, a symbol of royalty and power), or a certain color or pattern. Symbols are used often in poetry and other types of literature, sometimes as metaphors or similes.

paragraphs: A national emblem is a symbol for a certain country.

paragraphs: There are thousands of symbols that are recognized by most people all over the world, and many more that are limited to certain regions, religions, sciences, etc.. Some of the best known ones are listed below.


title: September

paragraphs: September (Sep.) is the ninth month of the year in the Gregorian calendar, coming between August and October. It has 30 days. Its name comes from the Latin word "sept" for "seven" (it was the seventh month of the year, before January and February were added to the beginning of the year.)

paragraphs: September always begins on the same day of the week as December, but never ends on the same day of the week as any other month.

paragraphs: In the old Roman calendar, September was the seventh month, which is where it got its name ("Septem" means "seventh"). The ninth month at the time was November ("Novem" means "ninth"). With Julius Caesar's calendar reform, September became the ninth month, with 30 days. September comes after August and before October.

paragraphs: September begins on the same day of week as December every year, as each other's first days are 13 weeks (91 days) apart. No other month in any year, common or leap year, ends on the same day of the week as September.

paragraphs: In common years, September starts on the same day of the week as April and July of the previous year, and in leap years, October of the previous year. In common years, September finishes on the same day of the week as April and December of the previous year, and in leap years, July of the previous year. In leap years and years immediately after that, September starts on the same day of the week as January of the previous year.

paragraphs: In years immediately before common years, September starts on the same day of the week as June of the following year, and in years immediately before leap years, March and November of the following year. In years immediately before common years, September finishes on the same day of the week as March and June of the following year, and in years immediately before leap years, August and November of the following year.

paragraphs: September is one of two months to have an equinox (the other is March, its seasonal equivalent in both hemispheres), where both day and night are roughly of equal length, occurring either on the 22nd or 23rd, halfway between the June and December solstices. In the Northern Hemisphere, Autumn (Fall) begins in this month, while in the Southern Hemisphere, this is the beginning of Spring. For meteorologists, the people who study the weather, these seasons begin on September 1 in those hemispheres. In most Northern Hemisphere countries, school starts in this month, following the summer holidays.

paragraphs: In Ancient Greece, September was called "Boedromion". The Anglo-Saxons called it "Gerstmonath", meaning "Barley month", referring to the harvest. In other countries, it is referred to as "Autumn Month", such as in Finland (Syyskuu) and German-speaking parts of Switzerland (Herbstmonat).

paragraphs: Ethiopian New Year occurs in September. Jewish New Year also often occurs in this month.


title: Sound

paragraphs: We can define a sound wave as a disturbance which travels through some medium.

paragraphs: Sound is the term to describe what is heard when sound waves pass through a medium to the ear. All sounds are made by vibrations of molecules through which the sound travels. For instance, when a drum or a cymbal is struck, the object vibrates. These vibrations make air molecules move. Sound waves move away from their sound source (where they came from), traveling on the air molecules. When the vibrating air molecules reach our ears, the eardrum vibrates, too. The bones of the ear vibrate in the same way that of the object that started the sound wave.

paragraphs: These vibrations let you hear different sounds. Even music is vibrations. Irregular vibrations are noise. People can make very complex sounds. We use them for speech.

paragraphs: Sound waves are longitudinal waves with two parts: "compression" and "rarefaction". Compression is the part of the sound waves where the molecules of air are pushed ("compressed") together. Rarefaction is the part of the waves where the molecules are far away from each other. Sound waves are a sequence of compression and rarefaction.

paragraphs: Sound waves can travel through solids, liquids, and gases, but they cannot travel through a vacuum (a place with nothing in it). This is why astronauts cannot talk to each other in space: they need a radio to hear each other. Sound can travel through water faster than through air; and even faster in solids like stone, iron, and steel. Sound travels at 335 metres (1,100 feet) per second in the air.

paragraphs: "Pitch" is the highness or lowness of sound. Pitch is how humans hear different frequencies. Frequency is determined by the number of vibrations per second. The highest key on a piano, for instance, vibrates 4,000 times per second. It has a frequency of 4000 hertz (Hz), or 4 kilohertz (kHz). Lower keys have lower frequencies. A note an octave higher than another note has twice the frequency of that note.

paragraphs: The intensity of a sound is how much sound energy goes through a square meter in one second. Sound waves with higher amplitude (bigger vibration) have higher intensity. The intensity of a sound is higher closer to the sound source. Farther away, it's less intense. The inverse-square law shows how sound intensity becomes smaller, farther from the source. "Inverse square" says that when distance gets multiplied by a number, sound intensity gets divided by that number squared (the number times itself). Thus, twice the distance means a quarter the intensity.

paragraphs: Sound intensities can be very different. They can range from 0.000000000001, which are barely heard, to 1 W/m (painfully loud). The decibel scale makes sound intensity numbers easier to work with. A 0.000000000001 W/m intensity is 0 dB (decibels). When the decibel number increases by 10, the intensity is ten times as much. So, a 1 W/m intensity is 120 dB.

paragraphs: Loudness is how people sense the intensity of sound. Loudness depends on sound intensity, sound frequency, and the person's hearing.

paragraphs: Audible sound has frequencies between 20 Hz to 20 kHz. Human beings can hear audible sound. Sound waves with frequency above 20 kHz are called ultrasound waves. Sound waves with frequency below 20 Hz are called infrasound waves. Human beings cannot hear ultrasound waves and infrasound waves, but some animals, like bats and dolphins, use them. Older people have an even smaller hearing range. People are best at hearing sounds between 1000 Hz and 6000 Hz.

paragraphs: When a sound source is moving towards someone, the frequency seems to increase. The same thing happens when someone moves toward the sound source. Frequency seems to decrease when someone moves away from a sound source. It also seems to decrease when the sound source moves away from someone. This is called the Doppler effect.

paragraphs: Halpern, Alvin, Erich Erlbach (1998). "Beginning Physics II: Waves, Electromagnetism, Optics, and Modern Physics," pg. 50-56


title: Society

paragraphs: Society is the term to describe human beings together (collective, the sum of their social networks and social interactions). The term comes from the Latin idea of "societas", or the connection between friends or allies (friend or ally being "Socinus"). It can also mean a specific group of people who interact, as well as a wider society of which they are members. People form societies in order to gain greater benefits as a group than would be possible separately. Many animals beside humans also do this, such as wolves or eusocial insects. Sociology is the name for the study of society.

paragraphs: A society is often considered in terms of citizenship, rights, and ethics. The strength and unity of any society's members' willingness to help each other is to be measured can be called social capital.

paragraphs: A social contract sets out the rules and roles for this kind of cooperation. One kind of social contract is a constitution – which outlines to some extent what society in a given state is intended to look like.


title: Suggestion

paragraphs: A suggestion is an idea that one suggests, or says is good for another (or others) to follow. Some people may agree to it, and some may disagree. If they disagree or have a different suggestion, the person who first suggested the idea will usually discuss with the other people and find a good conclusion that satisfies both and is good.


title: Spache Readability Formula

paragraphs: Spache Readability Formula is one method of finding out how hard a piece of writing is (its textual difficulty).

paragraphs: The method compares words in a text to a list of words which are familiar in everyday writing. The words that are not on the list are called "unfamiliar". The number of words per sentence are counted. This number and the percentage of unfamiliar words is put into a formula. The result is a reading age. Someone of this age should be able to read the text.

paragraphs: Spache works best on texts that are for children under the age of eight.

paragraphs: the formula; (0.141 * average sentence length)+(0.086 * percentage of difficult words)+0.839 = grade level

paragraphs: According to Oleander Solutions (), the revised Spache Formula is:


title: Sport

paragraphs: A sport is commonly defined as an athletic activity that involves a degree of competition, such as netball or basketball. Some games and many kinds of racing are called sports. A professional at a sport is called an athlete. Many people play sports with their friends. They need coaches to teach or train teams or individuals how to do better. Sports can be played indoors or outdoors and by individuals or teams.

paragraphs: For children, sports play an extremely important part in their lives by providing all round development of the child, physically, mentally and emotionally. It also helps them to be fit and keep them healthy.

paragraphs: Some people like to watch other people play sports. Those who watch others playing sports are called "fans". While some fans watch sports on television, others actually go to stadiums or other places where people pay to watch them in person. These fans are called "spectators".

paragraphs: People engage in many kinds of sports, for example:


title: Science

paragraphs: Science is what we do to find out about the natural world. Natural sciences include physics, chemistry, biology, geology and astronomy. Science uses mathematics and logic, which are sometimes called "formal sciences". Natural science makes observations and experiments. Science produces accurate facts, scientific laws and theories. 'Science' also refers to the large amount of knowledge that has been found using this process.

paragraphs: Research uses the scientific method. Scientific research uses hypotheses based on ideas or earlier knowledge, which can be categorized through different topics. Then those hypotheses are tested by experiments.

paragraphs: People who study and research science and try to find out everything about it are called scientists. Scientists study things by looking at them very carefully, by measuring them, and by doing experiments and tests. Scientists try to explain why things act the way they do, and predict what will happen.

paragraphs: Today, "science" usually refers to a way of pursuing knowledge, not just the knowledge itself. It is mainly about the phenomena of the material world. In the 17th and 18th centuries scientists increasingly sought to formulate knowledge in terms of "laws of nature" such as Newton's laws of motion. And over the course of the 19th century, the word "science" became increasingly associated with the scientific method itself, as a way to study the natural world, including physics, chemistry, geology and biology.

paragraphs: It was in the 19th century also that the term "scientist" was created by William Whewell. He meant it to distinguish those who sought knowledge on nature from those who sought other types of knowledge.

paragraphs: The scientific method is the name given to the methods used by scientists to find knowledge. The main features of the scientific method are:

paragraphs: A famous example of science in action was the expedition led by Arthur Eddington to Principe Island in Africa in 1919. He went there to record the positions of stars around the Sun during a solar eclipse. The observation of star positions showed that the apparent star positions close to the Sun were changed. In effect, the light passing the Sun was pulled towards the Sun by gravitation. This confirmed predictions of gravitational lensing made by Albert Einstein in the general theory of relativity, published in 1915. Eddington's observations were considered to be the first solid evidence in favour of Einstein's theory. Had the observations resulted differently, this would have counted against Einstein's theory, and perhaps refuted it (shown it was wrong).

paragraphs: Discoveries in fundamental science can be world-changing. For example:

paragraphs: Not everyone completely agrees about how science works. Some philosophers and scientists say that scientific theories are only accepted for the time being. They last so long as they are the best explanation. When theories no longer explain the data, they are discarded and replaced. Or, sometimes scientists will make a theory better rather than discard it, or they will keep on using the theory hoping that it will be made better eventually.

paragraphs: Science is a way to get knowledge by discarding what is not true.

paragraphs: Scientists must be very careful to make explanations that fit well with what they observe and measure. They compete to provide better explanations. An explanation might be interesting or pleasing, but if it does not agree with what other scientists really see and measure, they will try to find a better explanation.

paragraphs: Before a scientific article is published, other scientists read the article and decide whether the explanations make sense from the data. This is called peer review. After articles are published, other scientists will also check if the same experiments, observations or tests produce the same data again. Peer review and repeating experiments are the only way to be sure the knowledge is correct.

paragraphs: Science makes models of nature, models of our universe, and medicine. There are many different sciences with their own names. However it is not right to say "science says" any one thing. Science is a process, not just the facts and rules believed at one time.


title: Saint Lawrence River

paragraphs: The Saint Lawrence River (; Tuscarora: "Kahnawáʼkye"; Mohawk: "Kaniatarowanenneh", meaning "big waterway") is a big river in eastern North America. It flows between the Canadian province of Quebec & Ontario and the American state of New York, and through the major canadian city of Montreal. It is the third largest river in Canada.

paragraphs: The river drains water from the Great Lakes into the Atlantic Ocean. It is more than three thousand kilometres long. The river meets the Atlantic Ocean in a big "estuary" or bay, the biggest in the world; this is called the Gulf of Saint Lawrence.

paragraphs: The Canadian cities of Kingston, Montreal, Trois-Rivières and Quebec City are on this river. The Saint Lawrence Seaway allows ships to go up the river and through the Great Lakes right into the middle of North America.


title: Seville

paragraphs: Seville () is a big city in the South of Spain, in Europe. A big river called the Guadalquivir River goes through Seville.

paragraphs: The city of Seville is the capital of the Spanish region called Andalusia and of the province of Sevilla. The people who live in the city are called "Sevillanos" and there are almost a million of them: 700,000.

paragraphs: A very old story says that the city was started by the famous hero of Greece, named Hercules. The Romans when they came to Spain gave it the Latin name of Hispalis. Over time this changed to be spelled in English as "Seville". The Arab Moors took the city when they invaded the country, and you can still see a lot of the buildings they built during their 800-year stay in Spain (711-1492).

paragraphs: In 1992 Seville was the place for the Expo 92. There is a beautiful bridge across the Guadalquivir River called "Puente del Alamillo". It was thought up by Santiago Calatrava a famous building expert.

paragraphs: Seville is famous for its hot summer weather.

paragraphs: Seville is the home town of two soccer teams, Sevilla FC (often simply called "El Sevilla") and Real Betis Balompié (often called "El Betis").


title: Salami

paragraphs: Salami is a sausage that first came from Italy. The name comes from the Italian salare meaning to make something salty.

paragraphs: The original salami was made from a mix of chopped pork and salt which was dried using air in a casing. People who are Muslim are not allowed to eat this type of salami because it is pork. Now there are many types of salamis made in some countries. Nearly all are seasoned with a combination of herbs and spices in addition to salt. Salamis are now sometimes smoked or cooked before air drying. Some kinds are made of beef while others mix beef and pork. Most, if not all Italian salamis have garlic in them, but few German kinds do, for example. Some, like a few salamis from Spain, include paprika or chili. The difference between some types is in how coarse or fine the meat is chopped. Some "light" salami might add turkey or chicken to reduce both fat and calories.

paragraphs: Many salamis are named after the city or region where they come from. Some examples are Arles, Genoese, Hungarian, and Milano salamis.


title: Special English

paragraphs: Special English is a simple form of the English language. It is used by a public radio station called Voice of America, run by the United States government in Special English programs every day. Its news and feature programs are read more slowly than usual, using fewer English words and simple grammar.

paragraphs: The contents of Special English programs are much easier to understand. Special English is clearer and simpler, and it uses shorter sentences. It can also help someone whose English is weak to improve his or her English. In some countries, for example China, Special English is popular among people learning English.

paragraphs: Special English was first used on October 19, 1959. Special English started in that year as one of radio programs by the Voice of America. This broadcasts adopt slow space and simple English in order to increase understanding for millions of listeners. It is now also known as "Learning English".

paragraphs: Special English started in 1959. It was developed as an experimental radio program to spread information on news and culture to people outside the United States. Programs on VOA use a simpler English within about 1,500 words. And reports are paced 1/3 slower than regular English in order to allow listeners to increase a better understanding. This means broadcasters speak at about two-thirds the speed of conversational English. But far from sounding like a record played at the wrong speed. It now deals with various topics to keep interest of listeners, such as news, business, science, and culture. Stories are written in clear.

paragraphs: To be a Special English broadcaster, he or she needs a complicated skill that takes months of training. The training includes a professional voice trainer who teaches how to breathe properly and pronounce clearly. A chief of Special English at VOA said, "People in this country have likely never heard of Special English," and also said, "and, if they have, they often don't understand the significance of it to people in other countries."

paragraphs: One VOA staff explains that the main goal of Special English is for the listener to understand the content of what is being broadcast, and to make steady progress in English. “There is a fine line between being simplified and simplistic,” he says. “We never want to cross that line.” So when necessary, more “advanced” English words are used and the meanings made clear, so the stories never suffer from incomplete information.

paragraphs: Students and teachers in other countries say Special English is a good learning tool.

paragraphs: VOA broadcast a program titled 'Willis Conover, the Voice of Jazz, Is Now Online" in the past, as Willis Conover became a famous host at Music USA.


title: Sausage

paragraphs: Sausage is a food made of ground-up or chopped-up meat. It often has spices in it and is covered in a casing. Traditionally, a sausage casing is made of animal intestine, but can sometimes be made of plastic. There are many forms of sausages, including hot dog, pepperoni, bologna, and salami.

paragraphs: Sausages often have meat from the animal's head, lips, cheeks, ears and other parts. Some have blood in them. Irish and English sausages normally have a lot of "rusk," or bread crumbs, and they are less meaty than sausages from other countries. Vegetarian or vegan sausages are often made of products other than animal products, such as tofu.

paragraphs: Sausages may be used as a meal, in a sandwich, or in other foods like stews. Sausages can be eaten as whole pieces, or they can be chopped up as already cooked pieces.

paragraphs: Many countries and regions have special kinds of sausage. Sausages are some of the oldest foods.

paragraphs: The word "sausage" was first used in English in the mid-15th century. During the mid-15th century, the word "sausage" was spelled as "sawsyge". The word "sawsyge" came from Old North French "saussiche" (Modern French "saucisse")". The French word came from Vulgar Latin "salsica" (sausage), from "salsicus" (seasoned with salt).


title: Slang

paragraphs: Slang are words that are informal. Usually each generation or social group has its own slang - for example, older people can have trouble understanding the slang of younger people. On the other hand, younger people often understand, but find silly or old-fashioned, the slang of older people.

paragraphs: Over time, language tends to get more complex, since new words enter much faster than old words leave. Over time, slang almost always becomes part of the language, and approved for use by all.

paragraphs: It has also happened that some words used in Anglo-Saxon for bodily functions became thought of as profanity or rude after they were replaced by Latinate words like "urinate", "defecate" and "copulate" - which polite people were supposed to use after the Norman conquest of England in 1066. This was in part a way of making poor people (who spoke Anglo-Saxon) all appear to be rude, while more powerful people (who spoke Norman) appeared to be polite - one way that etiquette can develop, and reinforce power structure. This is only one example from history of how racism can be a reason for defining one group's language as 'slang' and another as 'correct'.

paragraphs: Wanting to have rules of grammar that do not change and the same vocabulary used by everyone for better communication is another reason that is often given for defining one group's language as correct.

paragraphs: An "idiom" can be slang, but it can also be a metaphor that becomes part of the culture.

paragraphs: Two examples of slang are 'wassup' and 'dunnow'. 'Wassup' usually means 'What is up?' (as in, 'How are you?'), and 'dunnow' usually means 'I don't know'.


title: Social contract

paragraphs: A social contract or political contract is an agreement between the people of a state and the government of a state. The people agree to follow certain rules made by the government. These rules are usually called laws. Laws help to make sure people have rights and that their rights are protected. One kind of social contract is a constitution. A constitution says how decisions are made, and sets limits on the powers of leaders and other people who have authority.

paragraphs: In the Age of Enlightenment, philosophers John Locke and Jean-Jacques Rousseau wrote books about social contracts. They saw good government as coming from social contracts. Rousseau wrote a book called "The Social Contract". Both the United States Declaration of Independence and United States Constitution use the theory of social contracts.


title: Social capital

paragraphs: Social capital is the willingness of people to help each other.

paragraphs: It often replaces money which people would use to buy the same help.

paragraphs: Society works best when there is plenty of social capital. The less social capital there is, the more social problems there usually are. If there is no social capital, war and revolution often results.

paragraphs: People who have no money and cannot get help from society may have to agree to do things they do not want to do, or force others to do things they do not want to. Organized crime grows in this way, and so do forced labour and slavery.

paragraphs: Most ways of measuring social capital have to do with trust - people who trust that favours and help will be available when they need it will favour and help others more. Those who are seen as trying to get a free ride will get much less help. A social climber tries to earn social capital by making friends with those who have it but without actually helping. Some call this kind of person a social parasite. They are very hard to detect, unlike people who cheat or commit fraud. When there are too many of these kinds of people, especially when they are politicians, people begin to mistrust their government. Rather than work with a political party to change law, they may start to look for direct revenge for things.

paragraphs: Social capital is a lot like real capital. The more money a person or a society has, the easier it is to do things and the better off people are. The less money, the more difficult things become and the worse people feel.


title: Site

paragraphs: A site is a real fixed physical location where something will or has happened or a place where something is.

paragraphs: It is used very often in building trades to mean the place where a building will go up.

paragraphs: A gravesite is a place where a person will be buried after they die.

paragraphs: The words onsite and offsite refer to work that must take place on the site, or which can take place somewhere else. For instance, a prefabricated building can be "built offsite" and then "moved onsite".

paragraphs: "Site" is also a common abbreviation in net jargon for "website". In this case no real physical location exists other than the place where the computers are, and one "goes to the site" simply by using a web browser to "go to" that URL. This is a conceptual metaphor. It can be confusing. Someone who uses it is also likely using other jargon.


title: Subtraction

paragraphs: Subtraction is the arithmetic operation for finding the difference between two numbers, though it can also be generalized to other mathematical objects such as vectors and matrices. The special names of the numbers in a subtraction expression are, minuend - subtrahend = difference. For example, the expression 7 - 4 = 3 can be read as "seven minus four equals three," "seven take away four leaves three," or "four from seven leaves three."

paragraphs: If the minuend is less than the subtrahend, the difference will be a negative number. For example, 17 - 25 = -8 . This can be read as "Seventeen minus twenty-five equals negative eight."

paragraphs: Subtraction is how cash registers determine the change a buyer receives, when the buyer pays with more money than the purchase cost.


title: String theory

paragraphs: String theory is a set of attempts to model the four known fundamental interactions—gravitation, electromagnetism, strong nuclear force, weak nuclear force—together in one theory. This tries to resolve the alleged conflict between classical physics and quantum physics by "elementary units"—the one classical force: gravity, and a new quantum field theory of the other three fundamental forces.

paragraphs: Einstein had sought a unified field theory, a single model to explain the fundamental interactions or mechanics of the universe. Today's search is for a unified field theory that is "quantized" and that explains matter's structure, too. This is called the search for a theory of everything (TOE). The most prominent contender as a TOE is string theory converted into superstring theory with its six higher dimensions in addition to the four common dimensions (3D + time).

paragraphs: Some superstring theories seem to come together on a shared range of geometry that, according to string theorists, is apparently the geometry of space. The mathematical framework that unifies the multiple superstring theories upon that shared geometrical range is M-theory. Many string theorists are optimistic that M-theory explains our universe's very structure and perhaps explains how other universes, if they exist, are structured as part of a greater "multiverse". M theory/supergravity theory has 7 higher dimensions + 4D.

paragraphs: Introductions to string theory that are designed for the general public must first explain physics. Some of the controversies over string theory result from misunderstandings about physics. A common misunderstanding even for scientists is the presumption that a theory is proved true in its "explanation" of the natural world wherever its "predictions" are successful. Another misunderstanding is that earlier physical scientists, including chemists, have already explained the world. This leads to the misunderstanding that string theorists began making strange hypotheses after they became unaccountably "set free from truth".

paragraphs: Newton's law of universal gravitation (UG), added to the three Galilean laws of motion and some other presumptions, was published in 1687. Newton's theory successfully modeled interactions among objects of a size we can see, a range of phenomena now called the "classical realm". Coulomb's law modeled electric attraction. Maxwell's electromagnetic field theory unified electricity and magnetism, while optics emerged from this field.

paragraphs: Light's speed remained about the same when measured by an observer traveling in its field, however, although "addition of velocities" predicted the field to be slower or faster "relative" to the observer traveling with or against it. So, versus the electromagnetic field, the observer kept losing speed. Still, this did not violate Galileo’s Principle of relativity that says the laws of mechanics work the same for all objects showing inertia.

paragraphs: By law of inertia, when no force is applied to an object, the object holds its velocity, which is speed "and" direction. An object either in "uniform motion", which is constant speed in an unchanging direction, or staying at rest, which is zero velocity, experiences inertia. This exhibits Galilean invariance—its mechanical interactions proceeding without variation—also called Galilean relativity since one cannot perceive whether one is at rest or in uniform motion.

paragraphs: In 1905, Einstein's special theory of relativity explained the accuracy of both Maxwell's electromagnetic field and Galilean relativity by stating that the field's speed is absolute—a universal constant—whereas both space and time are local phenomena "relative" to the object's energy. Thus, an object in relative motion shortens along the direction of its momentum (Lorentz contraction), and its unfolding of events slows (time dilation). A passenger on the object cannot detect the change, as all measuring devices aboard that vehicle have experienced length contraction and time dilation. Only an external observer experiencing relative rest measures the object in relative motion to be shortened along its travel pathway and its events slowed. Special relativity left Newton's theory—which states space and time as "absolute"—unable to explain gravitation.

paragraphs: By the equivalence principle, Einstein inferred that being under either gravitation or constant acceleration are indistinguishable experiences that might share a physical mechanism. The suggested mechanism was "progressive" length contraction and time dilation—a consequence of the local energy density within 3D space—establishing a progressive tension within a rigid object, relieving its tension by moving toward the location of greatest energy density. Special relativity would be a limited case of a gravitational field. Special relativity would apply when the energy density across 3D space is uniform, and so the gravitational field is scaled uniformly from location to location, why an object experiences no acceleration and thus no gravitation.

paragraphs: In 1915, Einstein's general theory of relativity newly explained gravitation with 4D spacetime modeled as a Lorentzian manifold. Time is one dimension merged with the three space dimensions, as every "event" in 3D space—2D horizontally and 1D vertically—entails a point along a 1D time axis. Even in everyday life, one states or implies both. One says or at least means, "Meet me at building 123 Main Street intersecting Franklin Street in apartment 3D on 10 October 2012 at 9:00PM". By omitting or missing the time coordinate, one arrives at the correct location in space when the sought event is absent—it is in the past or future at perhaps 6:00PM or 12:00AM.

paragraphs: By converging space and time and presuming both relative to the energy density in the vicinity, and by setting the only "constant" or absolute as not even mass but as light speed in a vacuum, general relativity revealed the natural world's previously unimagined balance and symmetry. Every object is always moving at light speed along a straight line—its equivalent, on a curved surface, called "geodesic" or "worldline"—the one pathway of least resistance like a free fall through 4D spacetime whose geometry "curves" in the vicinity of mass/energy.

paragraphs: An object at light speed in a vacuum is moving at maximal rate through 3D space but exhibits no evolution of events—it is frozen in time—whereas an object motionless in 3D space flows fully along 1D time, experiencing the maximal rate of events' unfolding. The displayed universe is relative to a given location, yet once the mass/energy in that vicinity is stated, Einstein's equations predict what is occurring—or did occur or will occur—anywhere in the universe. The popularized notion that "relative" in Einstein's theory suggests "subjective" or "arbitrary" was to some regret of Einstein, who later thought he ought have to named it "general theory".

paragraphs: The electromagnetic field's messenger particles, photons, carry an image timelessly across the universe while observers within this field have enough flow through time to decode this image and react by moving within 3D space, yet can never outrun this timeless image. The universe's state under 400 000 years after the presumed big bang that began our universe is thought to be displayed as the cosmic microwave background (CMB).

paragraphs: In 1915, the universe was thought to be entirely what we now call the Milky Way galaxy and to be static. Einstein operated his recently published equations of the gravitational field, and discovered the consequence that the universe was expanding or shrinking. (The theory is operable in either direction—time invariance.) He revised the theory add a "cosmological constant" to arbitrarily balance the universe. Nearing 1930, Edwin Hubble's telescopic data, interpreted through general relativity, revealed the universe was expanding.

paragraphs: In 1916 while on a World War I battlefield, Karl Schwarzschild operated Einstein's equations, and the Schwarzschild solution predicted black holes. Decades later, astrophysicists identified a supermassive black hole in the center of perhaps every galaxy. Black holes seem to lead galaxy formation and maintenance by regulating star formation and destruction.

paragraphs: In the 1930s, it was noticed that according to general relativity, galaxies would fall apart unless surrounded by invisible matter holding a galaxy together, and by the 1970s dark matter began to be accepted. In 1998 it was inferred that the universe's expansion, not slowing, is accelerating, indicating a vast energy density—enough to accelerate both visible matter and dark matter—throughout the universe, a vast field of dark energy. Apparently, under 5% of the universe's composition is known, while the other 95% is mysterious—dark matter and dark energy.

paragraphs: By the 1920s, to probe the operating of the electromagnetic field at minuscule scales of space and time, quantum mechanics (QM) was developed. Yet electrons—the matter particles that interact with the photons that are the electromagnetic field's force carriers—would appear to defy mechanical principles altogether. None could predict a quantum particle's location from moment to moment.

paragraphs: In the slit experiment, an electron would travel through one hole placed in front of it. Yet a single electron would travel simultaneously though multiple holes, however many were placed in front of it. The single electron would leave on the detection board an interference pattern as if the single particle were a wave that had passed through all the holes simultaneously. And yet this occurred only when unobserved. If light were shone on the expected event, the photon's interaction with the field would set the electron to a single position.

paragraphs: By the uncertainty principle, any quantum particle's exact location and momentum cannot be determined with certainty, however. The particle's interaction with the observation/measurement instrument deflects the particle such that greater determination of its position yields lower determination of its momentum, and vice versa.

paragraphs: By extending quantum mechanics across a field, a consistent pattern emerged. From location to adjacent location, the probability of the particle existing there would rise and fall like a wave of probability—a rising and falling probability density. When unobserved, any quantum particle enters superposition, such that even a single particle fills the entire field, however large. Yet the particle is not "definitely" anywhere in the field, but there at a definite "probability" in relation to whether it was had been at the adjacent location. The waveform of Maxwell's electromagnetic field was generated by an accumulation of probabilistic events. Not the particles, but the mathematical form, was constant.

paragraphs: Setting the field to special relativity permitted prediction of the complete electromagnetic field. Thus arose relativistic quantum field theory (QFT). Of the electromagnetic field, it is relativistic quantum electrodynamics (QED). Of the weak and electromagnetic fields together, it is relativistic electroweak theory (EWT). Of the strong field, it is relativistic quantum chromodynamics (QCD). Altogether, this became the Standard Model of particle physics.

paragraphs: When the Standard Model is set to general relativity in order to include mass, probability densities of infinity appear. This is presumed incorrect, as probability ordinarily ranges from 0 to 1—0% to 100% probability. Some theoretical physicists suspect that the problem is in the Standard Model, which represents each particle by a zero-dimensional point that in principle can be infinitely small. Yet in quantum physics, the Planck's constant is the minimum energy unit that a field can be divided into, perhaps a clue to the smallest size a particle can be. So there is a quest to "quantize" gravity—to develop a theory of quantum gravity.

paragraphs: String conjectures that on the microscopic scale, Einstein's 4D spacetime is a field of Calabi-Yau manifolds, each containing 6 space dimensions curled up, thus not extended into the 3 space dimensions presented to the classical realm. In string theory, each quantum particle is replaced by a 1D string of vibrating energy whose length is the Planck length. As the string moves, it traces width, and thus becomes 2D, a worldsheet. As a string vibrates and moves within the 6D Calabi-Yau space, the string becomes a quantum particle. With this approach, the hypothetical graviton—predicted to explain general relativity—emerges easily.

paragraphs: String theory began as bosonic string theory, whose 26 dimensions act as many fewer. Yet this modeled only bosons, which are energy particles, while omitting fermions, which are matter particles. So bosonic string theory could not explain matter. Yet by adding supersymmetry to bosonic string theory, fermions were achieved, and string theory became "super"string theory, explaining matter, too.

paragraphs: String theory's claim that all molecules are "strings of energy" has drawn harsh criticism. There are many versions of string theory, none quite successfully predicting the observational data explained by the Standard Model. M theory is now known to have countless solutions, often predicting things strange and unknown to exist. Some allege that string theorists select only the desired predictions.

paragraphs: The allegation that string theory makes no testable predictions is false, as it makes many. No theory—a predictive and perhaps explanatory model of some domain of natural phenomena—is verifiable. All conventional physical theories until the Standard Model have made claims about unobservable aspects of the natural world. Even the Standard Model has various interpretations as to the natural world. When the Standard Model is operated, it is often made a version with supersymmetry, doubling the number of particle species so far identified by particle physicists.

paragraphs: None can literally measure space, yet Newton postulated absolute space and time, and Newton's theory made explicit predictions, highly testable and predictively successful for 200 years, but the theory was still falsified as explanatory of nature. Physicists accept that there exists no such attractive force directly attracting matter to matter, let alone that the force traverses the universe instantly. Nevertheless, Newton's theory is still paradigmatic of science.

paragraphs: The idea of hidden dimensionality of space can seem occult. Some theorists of loop quantum gravity—a contender for quantum gravity—regard string theory as fundamentally misguided by presuming that space even has a shape until particles shape it. That is, they do not doubt that space takes various shapes, simply regard the particles as determining space's shape, not the other way around. The spacetime vortex predicted by general relativity is apparently confirmed.

paragraphs: If interpreted as naturally true, the Standard Model, representing a quantum particle as a 0D point, already indicates that spacetime is a sea of roiling shapes, quantum foam. String theorists tend to believe nature more elegant, a belief that loop theorist Lee Smolin dismisses as romantic while using biology's Modern Synthesis as a rhetorical device. Experiments to detect added spatial dimensions have so far failed, yet there is still the possibility that signs of them can emerge.

paragraphs: M theory has many trillions of solutions. Leonard Susskind, a leader of string theory, interprets string theory's plasticity of solutions as paradoxical support resolving the mystery of why "this" universe exists, as M theory shows it but a variant of a general pattern that always approximately results.

paragraphs: General relativity has brought many discoveries that in 1915 were all but unimaginable except in fiction. A solution of Einstein's equations that sought to explain quantum particles' dynamics, the Einstein-Rosen Bridge predicts a shortcut connecting two distant points in spacetime. Commonly called a wormhole, the Einstein-Rosen Bridge is doubted but not disproved, showing either that not all consequences of a theory must be accurate or that reality is quite bizarre in ways unobservable.

paragraphs: Even the Standard Model of particle physics suggests bizarre possibilities that populist accounts of science either omit or mention as unexplained curiosities. The theory conventionally receives the Copenhagen interpretation, whereby the field is only "possibilities", none real until an observer or instrument interacts with the field, whose wavefunction then collapses and leaves only its particle function, only the particles being real. Yet wavefunction collapse was merely assumed—neither experimentally confirmed nor even mathematically modeled—and no variance from either the wavefunction in the quantum realm or the particle function in the classical realm has been found.

paragraphs: In 1957 Hugh Everett described his "Relative state" interpretation. Everett maintained that the wavefunction does not collapse, and since all matter and interactions are presumed to be built up from quantum waveparticles, all possible variations of the quantum field—indicated by the mathematical equations—are "real" and simultaneously occurring but different courses of history. By this interpretation, whatever interacts with the field joins the field's state that is "relative" to the observer's state—itself a waveform in its own quantum field—while the two simply interact in a universal waveform never collapsing. By now, many physicists' interpretation of the apparent transition from the quantum to the classical realms is not wavefunction collapse, but quantum decoherence.

paragraphs: In decoherence, an interaction with the field takes the observer into only one determinant constellation of the quantum field, and so all observations align with that new, combined quantum state. Everett's thesis has inspired Many worlds interpretation, whereby within our universe are predicted to be virtually or potentially infinite parallel worlds that are real, yet each a minuscule distance from the other worlds. As each world's waveform is universal—not collapsing—and its mathematical relations are invariant, parallel worlds simply fill the gaps and do not touch.

paragraphs: Einstein doubted that black holes, as predicted by the Schwarzschild solution, are real. Some now conjecture that black holes do not exist as such but are dark energy, or that our universe is both—a black hole and dark energy. The Schwarzschild solution of Einstein's equations can be maximally extended to predict a black hole having a flip side—another universe emerging from a white hole. Perhaps our universe's big bang was half of a "big bounce", something's collapse down to a black hole, and our universe popping out its other side as a white hole.

paragraphs: Physicists widely doubt that quantum particles are truly 0D points as represented in Standard Model, which offers "formalism"—mathematical devices whose strokes predict phenomena of interest upon input of data—not "interpretation" of the mechanisms determining those phenomena. Yet string theorists do tend to optimistically conjecture that the strings are both real and explanatory, not merely predictive devices. It is far beyond the capacity of today's particle accelerators to propel any probing particles at energy levels high enough to overcome a quantum particle's own energy and determine whether it is a string. Yet this limitation also exists on testing other theories of quantum gravity. Developments suggest other strategies to "observe" the structure of quantum particles.

paragraphs: Paradoxically, even if testing confirmed that particles are strings of energy, that still would not conclusively prove even that particles are strings, since there could be other explanations, perhaps an unexpected warpage of space although the particle was a 0D point of true solidity. Even when predictions succeed, there are many possible explanations—the problem of underdetermination—and philosophers of science as well as some scientists do not accept even flawless predictive success as verification of the successful theory's explanations if these are posed as offering scientific realism, true description of the natural world.

paragraphs: Talk of particle physicists testing theoretical physicists' predicted particles by colliding particles in accelerators suggests that quantum particles are tiny Newtonian particles that experimentalists "crack" open to reveal their structure. Instead, when two particles, each of a certain mass—measured in terms of "energy" as electronvolts—are collided, they can combine into a particle of that combined mass/energy, and the generated particle is "observed" for correspondence with the prediction.

paragraphs: It is not controversial among physicists that all particles are "energy". Loop theorists, sometimes in rivalry with string theory, claim that spacetime itself converts into the particles. Matter's being a special variant of energy was a consequence of Einstein's special theory of relativity, and thereupon Einstein formalized the mass-energy equivalence, E=mc. When sufficiently energetic photons collide, they can combine and generate matter—matter creation. All particles have antiparticles, and atoms of matter have antiatoms of antimatter, whose union annihilates the particles and matter while leaving energy.

paragraphs: An inspiring development is discovery of mirror symmetry, whereby Calabi-Yau spaces tend to come in pairs such that solutions previously difficult within the extreme vibrational mode of one string can be solved by through the mirror Calabi-Yau space's geometry in its opposite range.

paragraphs: String theory is usually solved through conformal field theory, a quantum field theory on 2D space. It is confirmed that molecules can collapse to 2D. And the electron, long presumed an elementary particle, apparently splits into three entities separately carrying the electron's three degrees of freedom when the molecules that contain the electrons are channeled through a 1D pathway.


title: Scientist

paragraphs: A scientist is a person who studies or has mastered the field in science. A scientist tries to understand how our world, or other things, work. Scientists make observations, ask questions and do extensive research work in finding the answers to many questions others may not know about. Scientist has searched many things

paragraphs: Scientists may work in laboratories for governments, companies, schools and research institutions. Some scientists teach at universities and other places and train people to become scientists. Scientists often make experiments to find out more about reality, and sometimes may repeat experiments or use control groups. Scientists who are doing applied science try to use scientific knowledge to improve the world.

paragraphs: Scientists can work in different areas of science.


title: Soapbox

paragraphs: A soapbox is a temporary platform used to give a speech. During the 19th century, soap was transported in wooden boxes. When a person had new or unusual ideas, and wanted to talk to a crowd about them, sometimes he or she would stand on an empty soapbox so that everyone could see and hear the talk well.

paragraphs: People sometimes use the word "soapbox" to mean a place to say new or unusual things.


title: Supernatural

paragraphs: The word supernatural (from ) is used for things that some people believe are real, but that are not part of nature or inexplicable by the scientific laws of nature. Because we cannot prove whether these things are real, people often disagree about these things.

paragraphs: Some say that we should talk about things without talking about the supernatural, because we cannot prove that supernatural things are real. Other people say that although we cannot prove supernatural things in a scientific way, they are real. Some examples of supernatural things or examples are:


title: Spirit

paragraphs: A spirit is considered to be the part of a being that is not the body. Other words with the same meanings are soul and ghost. When a body is alive, it has a spirit in it. Death is when the spirit separates from the body.

paragraphs: Christians believe that spirits exist in Heaven or Hell. (See 1 Timothy 3:16, 4:1)

paragraphs: Spiritualists believe that spirits can talk with people, or change things in the world. Many religions forbid communicating with such spirits in any way, (see Leviticus 19:31) but a few include this as part of their practice.

paragraphs: Another use of "spirit" means the main purpose or meaning of a sentence or document. For example, the "spirit of a law" is the true meaning of the law which the creator wanted. This phrase is often used when the words and sentences of a law could mean more than one thing, but a judge must decide what meaning is correct.


title: Seed

paragraphs: A seed is the part of a seed plant which can grow into a new plant. It is a reproductive structure which disperses, and can survive for some time. A typical seed includes three basic parts: (1) an embryo, (2) a supply of nutrients for the embryo, and (3) a seed coat.

paragraphs: There are many different kinds of seeds. Some plants make a lot of seeds, some make only a few. Seeds are often hard and very small, but some are larger. The coconut is as big as a child's head, but it contains more than just a seed. At the start, seeds are "dormant" (resting inside their coat) for a while. When the seed is ready to develop, it needs water, air and warmth "but not sunlight" to become a seedling.

paragraphs: Seeds carry the food that helps the new plant begin to grow. This food store is in the endosperm, and/or in the cotyledons. Many kinds of seeds are good food for animals and people. The many kinds of grain that people grow, such as rice, wheat, and maize, are all seeds. Seeds are often inside fruits.

paragraphs: A seed, though not active, is a tiny living thing. It contains the embryo of the future plant, which is not changing or developing: it is "dormant". The common idea is that the seed "sleeps" until it gets what it needs to wake up. That is not correct. Different seeds have different habits, no doubt adapted to their habitat. There are different kinds of resting stages in seeds:

paragraphs: When a seed germinates ("wakes up"), it begins to grow into a little plant called a "seedling". It uses the soft fleshy material inside the seed for nutrients (food) until it is ready to make food on its own using sunlight, water and air.

paragraphs: Most seeds germinate underground where there is no sunlight. The plant does not need the nutrients in soil for a few days or weeks, because the seed has all the things it needs to grow. Later, though, it will begin to need sunlight. If there is sunlight, the plant will use it to grow healthy. If there is no light, the plant will still grow for a while, but its plastids will not mature: the chlorophyll does not turn green. If the plant does not get enough light, it will eventually die. It needs light to make food for itself when the reserve in the seed runs out.

paragraphs: Seeds have been an important development in the reproduction and spread of conifers and flowering plants. Plants such as mosses, liverworts and ferns do not have seeds, and use unprotected spores and other methods to propagate themselves. Before the upper Devonian period, land plants, like modern ferns, reproduced by sending spores into the air. The spores would land and become new plants only in favourable conditions. Spores have little food stored, and may be just single cells rather than embryos.

paragraphs: The evolution of seeds changed the plant life cycle by freeing plants from the need for external water for sexual reproduction, and by providing protection and nutrients for the developing embryo. These functions allowed plants to expand beyond the immediate neighbourhood of water sources. They were able to exploit environments which were drier and more upland. This can be seen by the success of seed plants in important biological niches on land, from forests to grasslands both in hot and cold climates. The present-day seed plants are the Gymnosperms, with naked seeds, and the Angiosperms with covered seeds, usually fruits.

paragraphs: The first true seeds are from the upper Devonian 370–354 million years ago, which is probably the theatre of their first evolutionary radiation. The earliest seed-producing trees were in the forests of the Carboniferous period. The seed plants steadily became one of the most important elements of nearly all ecosystems.


title: Sail

paragraphs: A sail is a large piece of cloth on the top of some boats. The wind goes around the sail and makes the boat move through the water. The piece that the sail is attached to is called a mast. Some boats have many sails, and some have only one. Usually, small boats have only one sail, and bigger boats have more. Boats with sails are called "sailing boats". There are many different names for different kinds of sailing boats with different kinds of sails.

paragraphs: Before people made boats with engines that used coal or oil, sailing boats were an important way to travel across oceans. Now they are not so important for transport, but they are still used for recreation and competition.

paragraphs: Modern sails can be classified into three main categories:

paragraphs: High-performance yachts, in particular some catamarans such as the International C-Class Catamaran, have used or use rigid wing sails, which are said to perform better than traditional soft sails. In particular, a rigid wing sail was used by Stars and Stripes, the defender which won the 1988 America's Cup, and by USA-17, the challenger which won the 2010 America's Cup.

paragraphs: Most modern yachts, including bermuda rig, ketch and yawl boats, have a sail "inventory" which usually includes more than one of these types of sails. Although the mainsail is “permanently” hoisted while sailing, headsails and spinnakers can be changed depending on the particular weather conditions to allow better handling and speed.


Spanish


title: Skin

paragraphs: Skin is the outside covering of animals. The skin of different kinds of animals is very different. Many kinds of animals have hair or fur on their skin. Birds have feathers on their skin. Most fish, and reptiles, like snakes and lizards, have scales on their skin.

paragraphs: The skin of human beings usually has very small hairs on it that are hard to see. Some people have more hair, or hair that is easier to see, and some have less. People have hair that is longer and easier to see on some parts of their bodies, such as the tops of their heads and men's beards. The skin is actually the largest organ of the human body. Without our skin we would easily get infected with diseases and viruses. Keeping it clean is important to health.

paragraphs: The skin of cows can be made into leather. Leather is sometimes used to make shoes, bags, and balls.

paragraphs: Other things can be said to have "skins". People often say that fruits, such as apples and bananas, and vegetables, such as potatoes, have "skins".


title: Search engine

paragraphs: A search engine is a website that allows users to look up information on the World Wide Web (www). The search engine will achieve this by looking at many web pages to find matches to the user's search inputs. It will return results ranked by relevancy and popularity by the search engine. Some popular search-engines are Google, Yahoo!, Ask.com, Forestle and Bing. Older services include Webcrawler, Lycos, and Alta Vista.

paragraphs: To use a search engine you must enter at least one keyword in to the search box. Usually an on-screen button must be clicked on to submit the search. The search engine looks for matches between the keyword(s) entered and its database of websites and words.

paragraphs: After the user inputs their search or query into the search bar, a list of results will appear on the screen known as search engine results page (SERP). This list of webpages contains matches related to the user's query in a particular order determined by a ranking system. Most search engine will remove "spam" pages from the list of results to provide a better list of results. The user can then click on any of the links to go to that webpage.

paragraphs: Search engines are some of the most advanced websites on the web. They use special computer code to sort the web pages on SERPs. The most popular or highest quality web pages will be near the top of the list.

paragraphs: When a user types words into the search engine, it looks for web pages with those words. There could be thousands, or even millions, of web pages with those words. So, the search engine helps users by putting the web pages it thinks the user wants first.

paragraphs: Search engines are very useful to find information about anything quickly and easily. Using more keywords or different keywords improves the results of searches.

paragraphs: A search service may also include a portal with news, games, and more information besides a search engine. Yahoo! has a popular portal, and MSN Search is part of the MSN portal, while Google has a simple design on its front page. Search services usually work without charging money for finding sites, and are often supported with text or banner advertisements.


title: Sabbath in Christianity

paragraphs: Sabbath in Christianity is the day of rest and service to God. The idea of the Sabbath in Christianity comes directly from the idea

paragraphs: of the Sabbath (or Shabbat) in Judaism. In fact, the word Sabbath itself comes from the Hebrew word "Shabbat." Like the Jewish Sabbath (Shabbat), the Sabbath in Christianity comes from the Genesis story of Creation. But unlike Jews, most Christians have Sabbath on Sunday, not Saturday. They also rest, but not the same way as Jews. The exact way depends on the church denomination.

paragraphs: Most Christians honor the Sabbath on Sunday to remember the Resurrection of Jesus on the first day of the week on the Jewish calendar. They say that there is an analogy between the obligation of the Christian day of worship and the Sabbath-day ordinance. These two rules are not literally identical though. They say that this ordinance is no longer valid, because God has replaced his old creation by a new one. For this reason, the obligation to keep the Sabbath is not the same for Christians as for Jews. They say there are examples in the New Testament, and in other writings surviving from the first few centuries.

paragraphs: Some conservative Christians are "Sabbatarians". Most of these follow the Reformed traditions. Sabbatarians think the first day of the week or "Lord's Day" is the new Sabbath. This is because the 4th commandment has never been revoked and Sabbath-keeping is in any case a creation ordinance.

paragraphs: Still others believe that the Sabbath remains as a day of rest on the Saturday, reserving Sunday as a day of worship. In reference to Acts 20:7, the disciples came together on the first day of the week (Sunday) to break bread and to hear the preaching of the apostle Paul. This is not the first time Christians assembled together on a Sunday; Jesus appeared to the Christians on the "first day of the week" while they were in hiding. One can maintain this argument in that Jesus himself maintained the Sabbath, although not within the restrictions that were mandated by Jewish traditions; the Pharisees often tried Jesus by asking him if certain tasks were acceptable according to the Law. This would seem to show that while the Sabbath was still of importance to the Jews, Sunday was a separate day for worship and teaching from Scriptures.

paragraphs: The Seventh-day Adventists and other churches disagree with some of these views. They argue that the custom of meeting for worship on Sunday originated in paganism, specifically Sol Invictus and Mithraism (in which sun god worship took place on Sunday). This is therefore an explicit rejection of the commandment to keep the "seventh" day holy. Instead, they keep Saturday as the Sabbath as a memorial to God's work of creation believing that none of the Ten Commandments can ever be destroyed. Seventh-day Sabbatarians claim that the seventh day Sabbath was kept by the majority of Christian groups until the 2nd and 3rd century, by most until the 4th and 5th century, and a few thereafter, but because of opposition to Judaism after the Jewish-Roman wars, the original custom was gradually replaced by Sunday as the day of worship. The history of these changes is certainly not altogether lost regardless of any belief in a suppression of the facts by a conspiracy of the pagans of the Roman Empire and the clergy of the Catholic Church.

paragraphs: Jews had come to be hated in the Roman Empire after the Jewish-Roman wars. This led to the criminalization of the Jewish Sabbath. Hatred of Jews is apparent in the Council of Laodicea (4th Century AD) where Canon 37–38 states: "It is not lawful to receive portions sent from the feasts of Jews or heretics, nor to feast together with them." and "It is not lawful to receive unleavened bread from the Jews, nor to be partakers of their impiety." In keeping with this rejection of the Jews, this Roman council also criminalized the Jewish Sabbath as can be seen in Canon 29 of the Council Laodicea: "Christians must not Judaize by resting on the Sabbath, but must work on that day, rather honoring the Lord's Day; and, if they can, resting then as Christians. But if any shall be found to be judaizers, let them be excommunicated from Christ."

paragraphs: In the Gospel of Mark 2:28 Jesus says 'the Son of Man is lord even of the sabbath'.


title: Statistics

paragraphs: Statistics is a branch of applied mathematics dealing with data collection, organization, analysis, interpretation and presentation. Descriptive statistics summarize data. Inferential statistics make predictions. Statistics helps in the study of many other fields, such as science, medicine, economics, psychology, politics and marketing. Someone who works in statistics is called a statistician. In addition to being the name of a field of study, the word "statistics" also refers to numbers that are used to describe data or relationships.

paragraphs: The first known statistics are census data. The Babylonians did a census around 3500 BC, the Egyptians around 2500 BC, and the Ancient Chinese around 1000 BC.

paragraphs: Starting in the 16th century mathematicians such as Gerolamo Cardano developed probability theory, which made statistics a science. Since then, people have collected and studied statistics on many things. Trees, starfish, stars, rocks, words, almost anything that can be counted has been a subject of statistics.

paragraphs: Before we can describe the world with statistics, we must collect data. The data that we collect in statistics are called measurements. After we collect data, we use one or more numbers to describe each observation or measurement. For example, suppose that we want to find out how popular a certain TV show is. We can pick a group of people (called a "sample") out of the total population of viewers. Then we ask each viewer in the sample how often they watch the show. The sample is data that one can see, and the population is data that one cannot see (assuming that not every viewer in the population are asked). For another example, if we want to know whether a certain drug can help lower blood pressure, we could give the drug to people for some time and measure their blood pressure before and after.

paragraphs: Numbers that describe the data one can see are called descriptive statistics. Numbers that make predictions about the data one cannot see are called inferential statistics.

paragraphs: Descriptive statistics involves using numbers to describe features of data. For example, the average height of women in the United States is a descriptive statistic: it describes a feature (average height) of a population (women in the United States).

paragraphs: Once the results have been summarized and described, they can be used for prediction. This is called inferential statistics. As an example, the size of an animal is dependent on many factors. Some of these factors are controlled by the environment, but others are by inheritance. A biologist might therefore make a model that says that there is a high probability that the offspring will be small in size—if the parents were small in size. This model probably allows to predict the size in better ways than by just guessing at random. Testing whether a certain drug can be used to cure a certain condition or disease is usually done by comparing the results of people who are given the drug against those who are given a placebo.

paragraphs: Most often, we collect statistical data by doing surveys or experiments. For example, an opinion poll is one kind of survey. We pick a small number of people and ask them questions. Then, we use their answers as the data.

paragraphs: The choice of which individuals to take for a survey or data collection is important, as it directly influences the statistics. When the statistics are done, it can no longer be determined which individuals are taken. Suppose we want to measure the water quality of a big lake. If we take samples next to the waste drain, we will get different results than if the samples are taken in a far-away and hard-to-reach spot of the lake.

paragraphs: There are two kinds of problems which are commonly found when taking samples:

paragraphs: We can reduce chance errors by taking a larger sample, and we can avoid some bias by choosing randomly. However, sometimes large random samples are hard to take. And bias can happen if different people are not asked, or refuse to answer our questions, or if they know they are getting a fake treatment. These problems can be hard to fix. See standard error for more.

paragraphs: The middle of the data is called an average. The average tells us about a typical individual in the population. There are three kinds of average that are often used: the mean, the median and the mode.

paragraphs: The examples below use this sample data:

paragraphs: Where formula_2 are the data and formula_3 is the population size (see also Sigma Notation).

paragraphs: This means that one calculates the mean by adding up all the values, and then divide by the number of values. For the example above, the mean is:

paragraphs: The problem with the mean is that it does not tell anything about how the values are distributed. Values that are very large or very small change the mean a lot. In statistics, these extreme values might be errors of measurement, but sometimes the population really does contain these values. For example, if there are 10 people in a room who make $10 per day and 1 who makes $1,000,000 per day. The mean of the data is $90,918 per day. Even though it is the average amount, the mean in this case is not the amount any single person makes, and thus is not very useful for some purposes.

paragraphs: The mean described above is the "arithmetic mean". Other kinds are useful for some purposes.

paragraphs: The median is the middle item of the data. For a given data formula_5, this is sometimes written as formula_6. To find the median, we sort the data from the smallest number to the largest number, and then choose the number in the middle. If there is an even number of data, there will not be a number right in the middle, so we choose the two middle ones and calculate their mean. In our example above, there are 10 items of data, the two middle ones are "57" and "64", so the median is (57+64)/2 = 60.5.

paragraphs: As another example, like the income example presented for the mean, consider a room with 10 people who have incomes of $10, $20, $20, $40, $50, $60, $90, $90, $100, and $1,000,000. Here, the median is $55, because $55 is the average of the two middle numbers, $50 and $60. If the extreme value of $1,000,000 is ignored, the mean is $53. In this case, the median is close to the value obtained when the extreme value is thrown out. The median solves the problem of extreme values as described in the definition of mean above.

paragraphs: The mode is the most frequent item of data. For example, the most common letter in English is the letter "e". We would say that "e" is the mode of the distribution of the letters.

paragraphs: As another example, if there are 10 people in a room with incomes of $10, $20, $20, $40, $50, $60, $90, $90, $90, $100, and $1,000,000, then the mode is $90, because $90 occurs three times and all other values occur fewer than three times.

paragraphs: There can be more than one mode. For example, if there are 10 people in a room with incomes of $10, $20, $20, $20, $50, $60, $90, $90, $90, $100, and $1,000,000, the modes are $20 and $90. This is bi-modal, or has two modes. Bi-modality is very common, and it often indicates that the data is the combination of two different groups. For instance, the average height of all adults in the U.S. has a bi-modal distribution. This is because males and females have separate average heights of 1.763 m (5 ft 9 + 1⁄2 in) for men and 1.622 m (5 ft 4 in) for women. These peaks are apparent when both groups are combined.

paragraphs: The mode is the only form of average that can be used for data that can not be put in order.

paragraphs: Another thing we can say about a set of data is how spread out it is. A common way to describe the spread of a set of data is the standard deviation. If the standard deviation of a set of data is small, then most of the data is very close to the average. If the standard deviation is large, though, then a lot of the data is very different from the average.

paragraphs: The standard deviation of a sample is generally different from the standard deviation of its originating population . Because of that, we write formula_7 for population standard deviation, and formula_8 for sample standard deviation.

paragraphs: If the data follows the common pattern called the normal distribution, then it is very useful to know the standard deviation. If the data follows this pattern (we would say the data is "normally distributed"), about 68 of every 100 pieces of data will be off the average by less than the standard deviation. Not only that, but about 95 of every 100 measurements will be off the average by less than two times the standard deviation, and about 997 in 1000 will be closer to the average by less than three standard deviations.

paragraphs: We also can use statistics to find out that some percent, percentile, number, or fraction of people or things in a group do something or fit in a certain category.

paragraphs: For example, social scientists used statistics to find out that 49% of people in the world are males.

paragraphs: In order to support statisticians, many statistical software have been developed:


title: Speed

paragraphs: Speed is the distance of a moving object in a given amount of time. Speed is a measure of how fast something is moving. The average speed of an object in a certain time is the distance the object travelled divided by the time. Speed is also the distance covered by an object per unit time. Speed=distance/time

paragraphs: where formula_4 is the distance and formula_5 is the time that has gone by.

paragraphs: There are many units of measurement for speed. For example, an object's speed can be measured in

paragraphs: When an object changes speed, it gets faster or slower. If the speed of the object increases, it is called acceleration. If the object gets slower, and the speed decreases, it is called deceleration, or negative acceleration.


title: Server log

paragraphs: A server log records what is happening on a server at any time. For example, an HTTP server runs a web site.


title: Server

paragraphs: In net jargon, a server is a computer that serves many kinds of information to a user or client machine. Usually a server will only do a few things for many clients. Every type of thing a server does is called a service. Services are used by other computers that are called clients. The relationship between client and server is called a client-server relationship. For example, Wikipedia has web servers which have a service for sending web pages over the Internet. Your client computer talks to Wikipedia's web page service to get web pages for you. A server can also host internet games, share files, and give access to peripheral equipment such as printers. In simple words, the individual computers are connected to some powerful computers called servers. These store files and information in the form of website. With an Internet connection, different users anywhere in the world can access these files.

paragraphs: For servers and clients to talk to each other, they need to be connected to a network. They need to use the same communication protocol, a set way for machines to talk to other machines. It is like a language. For example, the Wikipedia server runs the HTTP to send web sites to your computer, and your computer uses the HTTP Protocol to ask Wikipedia for pages.

paragraphs: Usually, servers are specially made to be more powerful and reliable. They are usually more expensive than normal computers. Sometimes, servers can be clustered, which means many servers are working together to do one service.

paragraphs: The server might slow down if there are too many people accessing the server at the same time, resulting in a high load. An overloaded server might also shut itself down automatically.

paragraphs: In a peer-to-peer system, every computer is both a client and a server to the others. This is commonly put into file sharing and VOIP. However, this can help in attempts at piracy.

paragraphs: Typical server operating systems are Linux, FreeBSD, NetBSD, and OpenBSD. Unlike other computers, a server often has no monitor, keyboard, or mouse. When a server doesn't have to do very much, server software can run on a computer that is also doing other things.

paragraphs: A web server is a type of server that is used to host websites.

paragraphs: Examples of web server software include Apache or IIS. A web server can host one, or many, websites. The default port for a web server to listen to is port 80 (HTTP) or 443 (HTTPS).

paragraphs: Some web servers do other things than just serving a web page. For example, they may have something called SSI that makes building a website easier.

paragraphs: Web servers use services like CGI to let software on the server make web pages. Some of the programming languages that can use CGI are scripting languages like Perl, Python, PHP, or ASP. Some are compiled languages like C++ or Java.


title: Simile

paragraphs: A simile is a figure of speech that compares two different things, usually by using the words 'like' or 'as'. It is used to make a "direct and clear comparison between two things .Similes" may be confused with metaphors, which do the same kind of thing. Similes use comparisons, with the words 'like' or 'as'. Metaphors use indirect comparisons, without the words 'like' or 'as'.