Aarushhh/wikipedia-simple-splitted huggingface dataset:
Plato had led the focused application of geometry, developed by Euclid, to explain the natural world. Yet by his view of nature, Plato regarded astronomy as similar to seeking a theoretical proof in geometry—abstract and not the real world—whereupon the mind's insights derived from a quest to hold other truths through the mind's probing of ethics and aesthetics would yield discovery of truths within the realm of Forms, outside space and time.

Aristotle's answer 

Aristotle, a student of Plato, answered the problem of universals differently. Aristotle explained that universals are concepts corresponding to traits borne and shared by the particular things themselves. Aristotle did not regard all reality as visible, as he recognized existence of souls, yet regarded souls as unobserved parts of the visible world, real in itself. Aristotelianism largely shaped the course of Western thought.
Aristotle developed a more or less full description and explanation of the natural world and developed logic—syllogistic logic—to derive conclusions of the relations among things. Aristotle's grounding in the visible world was a metaphysical approach that suggested what evolved by some 2000 years later into empirical science.

Platonism 
 
Some mathematicians and physicists are Platonists, for instance Max Tegmark and Roger Penrose. Yet today's Platonists usually view entities within the visible world as real, and simply regard universal abstractions like numbers, sets, propositions, and geometry as corresponding to real and timeless entities that also exist, though pure Platonists regard only the Forms or their realm as real.

By way of string theory and the holographic principle, some physicists conjecture that Plato's allegory of the cave approximates the natural world's structure. Tegmark, who regards only the mathematical structure of the universe as real, has been called a radical Platonist.

Notes
Notes

Philosophical movements and positions
Reality
A paradox is a sentence in logic that cannot be true but also cannot be false. It is self-contradictory. Many famous problems of this kind exist.

Liar's paradox
A famous paradox is called the liar's paradox. It is the simple sentence "This sentence is a lie", or equivalently, "This statement is false."

If the sentence is true, then it is a lie as it says.  But if it is a lie, it cannot be true. A lie cannot also be a truth. So the sentence being true makes it a lie.

On the other hand, if the sentence is a lie, then it is not as it says: it is true.  But that is just what the sentence says, which makes the content of the sentence true.  So the sentence being a lie makes it true.

This paradox is not just in English, but in any language. It is true of mathematics as well.  Paradox can never be removed from any symbol system that makes claims about itself.
Other examples
Another example is the statement that "there is no cabal".  Only a cabal can know if there is no cabal, so this is either a guess, or, it is a cabal trying to pretend it does not exist.

Not all paradoxes are true logical paradoxes, since they can also be common-sense-defying statements that appear true. Some famous examples of this kind of paradox include:
 Zeno's paradoxes of motion
 Simpson's paradox in statistics
 Grandfather paradox
Banach–Tarski paradox

Informal uses of "paradox" 
A paradox can also arise in ethics. Assuming power over others may sometimes be required to protect them while diminishing their right to autonomy. This is an ethical dilemma but not a logical paradox.

Related pages
 Contradiction
 Dilemma
 Irony
 Oxymoron
 Buttered cat paradox
 Thought experiment

References
A potato is a vegetable, the Solanum tuberosum. It is a small plant with large leaves. The part of the potato that people eat is a tuber that grows under the ground.

A potato has a lot of starch and other carbohydrates. Potato usually has a light-brown or yellowish skin and is white or yellow inside. If the potato gets light on it, the tuber turns green and will be poisonous.

History 
The potato came from the high and cool areas of the Andes mountains. It was grown as a food crop thousands of years ago. When Spanish conquistadores came to South America in the 1500s, they took potatoes back to Europe.

It took nearly 200 years for the potato to become a widely grown crop. In the 1780s the farmers in Ireland began growing potatoes because they grew well in the poor soils. They also have most of the vitamins that people need to live. When a potato plague destroyed the crop in 1845, the Irish Potato Famine killed many people.
The potato plant is now grown in many parts of the world. Captain William Bligh planted potatoes on Bruny Island, Tasmania in 1792. In Australia they are now the largest vegetable crop.

Name origin 
The English word "potato" comes from the Spanish word "patata". The Royal Spanish Academy says the Spanish word is a hybrid of the Taíno  ('sweet potato') and the Quechua  ('potato').

Types 
 Yukon Gold – developed in Canada
 Norgleam
 Bismark
 Coliban
 Russet
 Pontiac
 Sequoia
 Desiree – cream colored flesh, red skin
 Bintje
 Irish grown

Scientists in Germany have used genetic engineering to make a potato called the Amflora, which could be grown to make starch for making other things in factories.
Cooking 
Potatoes are almost always eaten cooked. People cook potatoes by boiling, baking, roasting, or frying them. French fries or "chips" are potatoes cut into long pieces and fried until they are soft. Potato chips, often called crisps, are potatoes cut into very thin round pieces and fried until they are hard.

References 

Solanum
Plants are one of five big groups (kingdoms) of living things. They are autotrophic eukaryotes, which means they have complex cells, and make their own food. Usually, they cannot move (not counting growth).

Plants include familiar types such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 391,000 extant (living) species of plants.  Fungi and non-green algae are not classified as plants.

Most plants grow in the ground, with stems in the air and roots below the surface. Some float on water. The root part absorbs water and some nutrients the plant needs to live and grow. These climb the stem and reach the leaves. The evaporation of water from pores in the leaves pulls water through the plant. This is called transpiration.
A plant needs sunlight, carbon dioxide, minerals and water to make food by photosynthesis. A green substance in plants called chlorophyll traps the energy from the Sun needed to make food. Chlorophyll is mostly found in leaves, inside plastids, which are inside the leaf cells. The leaf can be thought of as a food factory. Leaves of plants vary in shape and size, but they are always the plant organ best suited to capture solar energy. Once the food is made in the leaf, it is transported to the other parts of the plant such as stems and roots.

The word "plant" can also mean the action of putting something in the ground. For example, farmers plant seeds in the field.

Types of plants
Green algae:
Chlorophyta
Charophyta
Land plants (embryophyte)
 Non-vascular plants (bryophytes):
 Liverworts
 Mosses
 Hornworts
 †Horneophytopsida
Vascular plants (tracheophytes)
 Lycopodiophyta—clubmosses
 Pteridophyta: the ferns
 Pteridopsida: the typical ferns
 Sphenopsida: the horsetails
 Marattiopsida: a divergent group of ferns

 Psilotopsida
sister-group to all other ferns
 †Rhyniophyta—rhyniophytes
 †Zosterophyllophyta—zosterophylls
 †Trimerophytophyta—trimerophytes
 †Progymnospermophyta
 Seed plants (spermatophytes)
 †Pteridospermatophyta: the seed ferns
 Pinophyta: the conifers
 Cycadophyta: the cycads
 Ginkgophyta: the ginkgos
 Gnetophyta: sister group to the Angiosperms
 Magnoliophyta or Angiosperms (flowering plants)
 Dicotyledons
 Monocotyledons
†Nematophytes

The plant food factory
At least some plant cells contain photosynthetic organelles (plastids) which enable them to make food for themselves. With sunlight, water, and carbon dioxide, the plastids make sugars, the basic molecules needed by the plant. Free oxygen (O2) is produced as a by-product of photosynthesis.

Later, in the cell cytoplasm, the sugars may be turned into amino acids for proteins, nucleotides for DNA and RNA, and carbohydrates such as starch. This process needs certain minerals: nitrogen, potassium, phosphorus, iron and magnesium.

Plant nutrients
Plant nutrition is the study of the chemical elements that are necessary for plant growth.
Macronutrients:
 N = Nitrogen (Carbohydrates, amino acids & glycolipids)
 P = Phosphorus (ATP and the energy cycle)
 K = Potassium (water regulation, opening and closing of stomata in some plant species)
 Ca = Calcium (transport of other nutrients)
 Mg = Magnesium (major constituent of chlorophyll, activator to various enzymes)
 S = Sulfur (some amino acids)
 Si = Silicon (cell walls)

Micronutrients (trace elements) include:
 Cl = Chlorine (osmosis and ion balance)
 Fe = Iron (photosynthesis ans enzyme co-factor)
 B = Boron (sugar transport and cell division)
 Mn = Manganese (building chloroplasts)
 Na = Sodium (various)
 Zn = Zinc (activator to many enzymes)
 Cu = Copper (photosynthesis)
 Ni=  Nickel (an enzyme)
 Mo = Molybdenum (enzyme co-factors)
Roots
The roots of plants perform two main functions. First, they anchor the plant to the ground. Second, they absorb water and various nutrients dissolved in water from the soil. Plants use the water to make food. The water also provides the plant with support. Plants that lack water become very limp and their stems cannot support their leaves. Plants which specialise in desert areas are called xerophytes or phreatophytes, depending on the type of root growth.

Water is transported from the roots to the rest of the plant through special vessels in the plant. When the water reaches the leaves, some of it evaporates into the air. Many plants need the help of fungi to make their roots work properly. This plant/fungi symbiosis is called mycorrhiza. Rhizobia bacteria in root nodules help some plants get nitrogen.

Flowering plant reproduction

Flowers and pollination
Flowers are the reproductive organ only of flowering plants (Angiosperms). The petals of a flower are often brightly colored and scented to attract insects and other pollinators. The stamen is the male part of the plant. It is composed of the filament (a stalk) that holds the anther, which produces the pollen. Pollen is needed for plants to produce seeds. The carpel is the female part of the flower. The top part of the carpel contains the stigma. The style is the neck of the carpel. The ovary is the swollen area at the bottom of the carpel. The ovary produces the seeds. The sepal is a leaf that protects a flower as a bud.

How pollen moves from one flower to another flower is called pollination. This transfer can happen in different ways. Insects such as bees are attracted to bright, scented flowers. When bees go into the flower to gather nectar, the spiky pollen sticks to their back legs. The sticky stigma on another flower catches the pollen when the bee lands or flies nearby it.
Some flowers use the wind to carry pollen. Their dangling stamens produce lots of pollen that is light enough to be carried by the wind. Their flowers are usually small and not highly coloured. The stigmas of these flowers are feathery and hang outside the flower to catch the pollen as it falls.

Seed travelers
A plant produces many spores or seeds. Lower plants such as moss and ferns produce spores. The seed plants are the Gymnosperms and Angiosperms. If all the seeds fell to the ground besides the plant, the area might become overcrowded. There might not be enough water and minerals for all the seeds. Seeds usually have some way to get to new places. Some seeds can be dispersed by the wind or by water. Seeds inside juicy fruits are dispersed after being eaten. Sometimes, seeds stick to animals and are dispersed that way.

Fossils
The question of the earliest plant fossils depends on what is meant by the word "plant".
If by plants we mean phototrophs using chlorophyll, then cyanobacteria in stromatolites are the first fossils, 3,450 million years ago (mya) in the Archaean eon. The remarkable precision is possible because the fossils were sandwiched between lava flows that could be precisely dated from embedded zircon crystals.
If by plants we include all types of algae, then the earliest known red algae lived 1.6 billion years ago. Fossils of them were recently found in India.
If by plants we mean green plants, Viridiplantae, then the first fossils are green algae. This is probably the majority position amongst professional botanists. There is convincing evidence for the monophyly of charophyte green algae and embryophytes. There are still two choices:
Acritarchs (a group of organic-walled microfossils) may be reproductive cysts of green algae. If so, they are present in the Neoproterozoic era, 1000 mya.
Otherwise, there is a large increase in planktonic algae around 540 mya in the Cambrian period.
If by plants we mean land plants, the first fossils are in the Silurian.
By the Silurian, fossils of whole plants are preserved, including the lycophyte Baragwanathia. From the Devonian, detailed fossils of rhyniophytes have been found. Early fossils of these ancient plants show the individual cells within the plant tissue. The Devonian period also saw the evolution of the first tree in the fossil record, Wattezia. This fern-like tree had a trunk with  fronds, and produced spores.

The coal measures are a major source of Palaeozoic plant fossils, with many groups of plants in existence at this time. The spoil heaps of coal mines are the best places to collect; coal itself is the remains of fossilised plants, though structural detail of the plant fossils is rarely visible in coal. In the Fossil Forest at Victoria Park in Glasgow the stumps of Lepidodendron trees are found in their original growth positions.

Related pages
 Spore
 Seed
 Germination

References

Basic English 850 words
A prediction is a statement that someone makes about what they think is going to happen. It is often very helpful to know what is going to happen to help prepare for these future events. Predictions are based on the idea that two beginning positions that are like each other will have similar results. By watching something happen, it is possible to predict what will happen if something similar happens. Predictions are given by science or fortune tellers or horoscopes. 

The most common example of a prediction is the weather forecast. Studying how weather happens lets people predict what the weather will be by looking at what is currently happening. This is helpful because by knowing that it is going to rain, a person can wear the right clothes for it.

Nostradamus has made many predictions about the future.

Related pages 
Forecasting
Hypothesis

Future events
Probability is a part of applied mathematics. It has to do with chance, the study of things that might happen or might not happen.

For example, using probability, one can show that by throwing a coin up in the air and letting it land, half of the time it will land with one side facing up, and half of the time with the other side facing up. Many coins have a picture of the face of a famous person on one side, and something else on the other side. Often people call the side with the face "heads", and the other side "tails".

The probability (p) of an event E, written , is always between zero (impossible) and one (certain).

If we roll a die (plural: dice), then the chance that it will land on 1 is 1/6 (because there are 6 numbers on a die). Similarly, the chance it will land on 2 is also 1/6. The chance it will land on any number between 1 and 6 is 1, because every time we roll the die, it will always land on a number between 1 and 6.
Probability can be figured out using mathematics. For example, if one rolls six dice, the chance of them getting a number more than ten is not obvious, but can be figured out using math and science.

One of the most interesting things about chance is that to figure out the probability that two things will both happen, one usually multiply their two probabilities together. For example, suppose that one wants to know the probability of rolling two dice and getting a certain combination (it could be two 6s or a 3 then a 5, just any two). The possibility of getting a 3 is one in six (), and the possibility of getting a 5 is also one in six, so the chances of getting a 3 then a 5 is ×=⅟36. If that number is expressed as somewhere between 0 and 1, it equals 0.027...7, which is fairly low. The possibility of getting a 3, then a 5, and then a 2 would be ××=⅟216 or 0.00463, which is a much lower probability.
Ideas of probability 
People like Jacob Bernoulli, Pierre-Simon Laplace, or Christiaan Huygens used the word probability, as described above. Other people thought about frequencies; the notion of probability is usually called frequency probability.

Related pages 
List of mathematics topics
 Probability density function
 Probability distribution
 Probability space
Probability theory
 Random
 Random variable
Stochastic process

References

Probability theory
A probability experiment is a situation where chance affects the result of an experiment.  If the experiment can only have two outcomes, it is named Bernoulli trial. A coin flip is a probability experiment because chance affects whether a coin will land heads or tails when it is flipped.

Probability theory
Experiments
Proteins are long-chain molecules built from small units known as amino acids. They are joined with peptide bonds.

They are biochemical compounds of one or more polypeptides folded into a round or fibrous shape.

A polypeptide is a single linear polymer chain of amino acids. The sequence of amino acids in a polypeptide comes from the DNA sequence of a gene. The genetic code specifies 20 standard amino acids. Shortly after synthesis, some amino acids are chemically modified. This alters the folding, stability, activity, and function of the protein. Sometimes proteins have non-peptide groups attached, as cofactors.
Proteins are essential to all cells. Like other biological macromolecules (polysaccharides and nucleic acids), proteins take part in virtually every process in cells:
 Many proteins are enzymes that catalyze (help to happen) biochemical reactions and are vital to metabolism.
 Other proteins have structural or mechanical functions, such as in muscle and in cells. The cytoskeleton is a system of scaffolding that keeps cell shape.
 Other proteins are important in cell signalling, immune responses, and cell division

Formation 
Proteins are formed by a process called "protein synthesis". The cell reads the genetic information of the DNA and translates it into a protein. In eukaryotes, this process begins in the cell nucleus and ends in the ribosome. In prokaryotes all of it is done in the cytoplasm.
Proteins have different functions depending on their shape and sequence. They can be found in meat or muscle. They are used for growth and repair, as well as for strengthening the bones. They help to make tissue and cells. They are in animals, plants, fungi, bacteria, and in the human body.

Muscles are mostly made of protein. When protein is digested, it is broken down into amino acids. These amino acids can then be used to build new protein. Proteins form an important part in foods like milk, eggs, meat, fish, beans, spinach, and nuts. There are four factors that determine what a protein will do. The first is the order of the amino acids. There are 20 different types of amino acids. The second is the little twists in the chain. The third is how the entire structure is folded up. The fourth is whether it is made up of different sub-units. Haemoglobin molecules, for example, are made of four sub-units.
Damaging mutations 
Most proteins are enzymes, and mutations may slow them or stop them working. 50% of human cancers are caused by mutations in the tumour suppressor p53. p53 is a protein which regulates cell division.

Lifespan 
Once formed, proteins only exist for a certain period. Then they are and recycled by the cell's machinery. A protein's lifespan is measured by its half-life. This covers a wide range. They can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells.

Essential amino acids 
Proteins are necessary in an animal's diet, since they cannot make all the amino acids they need (they can make most of them). They must get certain amino acids from food. These are called the essential amino acids. Through digestion, animals break down ingested protein into free amino acids. The amino acids are then used in metabolism to make the enzymes and structures the body needs.
There are nine essential amino acids for humans, which are obtained from food. The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Meat contains all the essential amino acids humans need; most plants do not. However, eating a mixture of plants, such as both wheat and peanut butter, or rice and beans, provides all the essential amino acids needed. Soy products like tofu provide all the essential amino acids—as does quinoa—but these are not the only way to get the protein humans need.

Proteins were first described by the Dutch chemist Gerardus Johannes Mulder. Jöns Jacob Berzelius gave proteins their name. Hundreds of other scientists have studied proteins since him.

Related pages 
 Protein structure
 Protein folding
 Translation (genetics)

References

Other websites
 Protein from the Harvard School of Public Health
The periodic table is a table that puts all known chemical elements in a specific order. Elements that have similar characteristics are often put near each other.  In the table, the elements are placed in the order of their atomic numbers starting with the lowest number of one, hydrogen. The atomic number of an element is the same as the number of protons in that particular nucleus of an atom. In the periodic table the elements are arranged into periods and groups. A row of elements across the table is called a period. Each period has a number; from 1 to 8. Period 1 has only 2 elements in it: hydrogen and helium. Period 2 and Period 3 both have 8 elements. Other periods are longer. Elements in a period have consecutive atomic numbers.
A column of elements down the table is called a group. There are 18 groups in the standard periodic table.  Each group has a number: from 1 to 18. Elements in a group have electrons arranged in similar ways, according to the number of valency electrons, which gives them similar chemical properties (they behave in similar ways).  For example, group 18 is known as the noble gases because they are all gases and they do not combine with other atoms.

There are two systems of group numbers; one using Arabic numerals (1,2,3) and the other using Roman numerals (I, II, III). The Roman numeral names were used in most of the 20th century.  In 1990 the International Union of Pure and Applied Chemistry (IUPAC) decided to use the new system with Arabic numerals, to replace the two old group systems that used Roman numerals.
The periodic table has been used by chemists to observe patterns and relationships between elements. There are 3 main groups in the Periodic Table; metals, metalloids, and nonmetals. For example, elements to the bottom and far left of the table are the most metallic, and elements on the top right are the least metallic. (e.g. caesium is much more metallic than helium). There are also many other patterns and relationships.

The periodic table was invented by the Russian chemist Dmitry Ivanovich Mendeleyev (18341907). In his honor, element 101 was named after him, mendelevium.

Standard periodic table 

Chemical Series of the Periodic Table

 Alkali metals
 Alkaline earths
 Lanthanides
 Actinides
 Transition metals
 Poor metals
 Metalloids/Semi metals/Half metals
 Nonmetals
 Halogens
 Noble gases
State at standard temperature and pressure. The colour of the number (atomic number) above the element symbol shows the state of the element at normal conditions.
 those in blue are gases
 those in green are liquids
 those in black are solid

Radioactivity

 Those with solid borders have stable isotopes (Primordial elements)
 Those with dashed borders have only radioactive naturally occurring isotopes
 Those with dotted borders do not occur naturally (Synthetic Elements)
 Those without borders are too radioactive to have been discovered yet.

Other arrangements of the Periodic Table 
The version of the periodic table shown above is the one most used.  Other widespread versions are shown below:
Other versions 
 The standard table provides the basics. It is shown above
 A vertical table for improved readability in web browsers
 The big table provides the basics plus full element names
 The huge table provides the basics plus full element names and atomic masses
 Electron configurations
 Metals and Non Metals
 List of elements: includes name, symbol, atomic number, atomic mass, group, and period; sortable by any of those
 List of elements by symbol
 List of elements by boiling point
 List of elements by melting point
 List of elements by density

Related pages 
 Periodic table group
 Periodic table period
Extended periodic table

Other websites 

 Periodic Table of the Elements – displays basic properties
 WebElements Periodic table
Physiology is the study of how living things work. Physiologists can study how organs of an organism work together to make things happen. In human beings, for example, the digestion of food hormones and other chemicals are made by the stomach, liver, and pancreas. Muscle contraction happens because of chemical messages made by nerves of that muscle. By learning how the body functions normally, physiologists and physicians can better understand what happens when organs do not function normally. For example, an understanding of how the thyroid gland functions has helped in treating goitre. Studies of the circulatory system and the nervous system have helped physicians understand and treat such illnesses like heart disease, stroke, and high blood pressure.

The field is usually divided into human physiology, animal physiology, and plant physiology.

References

Other websites 
 The Physiological Society
 Developmental physiology
 The American Physiological Society
A planet is a large object such as Venus or Earth that orbits a star. Planets are smaller than stars, and they do not make light. Jupiter is the biggest planet in the Solar System, while the smallest planet in the Solar System is Mercury.

Planets are shaped like a slightly squashed ball (called a spheroid). Objects that orbit planets are called satellites. A star and everything which orbits it are called a star system. 

There are eight planets in the Solar System. Pluto used to be called a planet, but in August 2006, the International Astronomical Union decided it was a dwarf planet instead. There are four more known dwarf planets in the Solar System, Ceres, Makemake, Eris and Haumea.

The name "planet" is from the Greek word πλανήτης (planetes), meaning "wanderers", or "things that move". Until the 1990s, people only knew the planets in the Solar System.
Origin of the planets 
The planets are made of elements that are very different from the Sun (which is mostly hydrogen). The Sun is mostly made up of hydrogen, with some helium. Its energy comes from converting hydrogen to helium. In contrast, the planets are mostly made up of larger atoms and molecules which could not have come from the Sun. The materials of planets must have come from another source or sources. Those sources were atoms made in earlier supernovae explosions near the Sun's path as it moved through its part of the Milky Way. The material captured by the Sun's gravity formed the planets. The same thing happened in other planetary systems in the galaxy.

The gas giants are made up of hydrogen gas like the Sun, plus (at their centres) metallic elements like the terrestrial planets.

Historical names
Historical names 

The planets in the Solar System have names of Greek or Roman gods, except for Earth, because people did not think Earth was a planet in old times. However, Earth is occasionally referred by the name of a Roman god: Terra. Other languages, for example Chinese, use different names. Moons also have names of gods and people from classical mythology. The names of the moons of Uranus are from the plays written by Shakespeare.

Planets 
Here is a list of planets in the Solar System from the closest to the farthest

Types of planets 
There are planets, and smaller objects that also go around the Sun. Some examples of smaller objects are asteroids, comets, and trans-Neptunian objects.
There are three types of planets in the Solar System. They are:
 Terrestrial or rocky: These are planets that are like Earth. They are mostly made up of rocks. They include: Mercury, Venus, Earth, Mars. 
 Jovian or gas giant: These planets are mostly made of gas in their outer layers. They all have metallic cores. They include: Jupiter, Saturn, Uranus, Neptune.
 Icy: These planets are mostly made of ice. It includes Pluto. Many objects in the Solar System that are not planets are also "icy". Examples are the icy moons of the outer planets of the Solar System (like Triton).

Related pages
 Formation and evolution of the Solar System
 List of planets
 Ice dwarfs

References

Planets
The People's Republic of China claims that the island of Taiwan is part of its territory, but the Republic of China (which was the government that controlled all of China from 1911 to 1949) still claims the land as theirs, and does still control Taiwan.

Many people say the government stops people from having freedom of speech, freedom of religion and other political rights that people in other countries have. China still has one-party rule, and is not a democracy.

Territorial disputes 
The following territories are claimed by China (PRC and/or ROC) and by another country or more.

Diaoyu Islands (with Japan)
Nansha Archipelago (with Vietnam, Brunei, Malaysia, and the Philippines)
Xisha Archipelago (with Republic of China and Vietnam)
South Tibet - parts of Arunachal Pradesh (with Republic of India)
Aksai Chin - part of Kashmir (with Republic of India)
Lost territories (Unequal treaties) 
Unequal treaties were forced onto Asian countries when European imperialism reached Asia. 
The list includes claims from PRC and ROC, as well as unofficial historical claims.
Note: Japan's and Korea's unequal treaties have been resolved since the end of WWII.

 Mongolia (lost to independence)
 Tuva (lost to Russian Empire)
 Outer Manchuria (lost to Russian Empire)
 Kyrgyzstan (lost to Russian Empire)
 parts of Kazakhstan (lost to Russian Empire)
 parts of Myanmar (lost to British Empire)
 Bhutan (lost to British Empire)
Hong Kong (lost to British Empire) (returned to PRC with effect from 1 July 1997 under the Sino-British Joint Declaration)
 Macau (lost to Portugal) (transferred to PRC on 20 December 1999)
 Tonkin & Northern Annam (lost to France)
 Ryukyu Islands (lost to Japanese Empire)

Related pages 
1989 Tiananmen Square protests
List of Chinese dissidents
Movies banned in China
Websites blocked in China
Falun Gong

Politics of China
Police are a group of people whose job is to enforce laws, help with emergencies, solve crimes and protect property. A person who carries out this duty is known as a police officer.

They work out of a police station. Police are trained in first aid and rescue, because police officers are often one of the first people to get to a place where people are sick or injured, such as a car accident, or a fire.

Naming
A police agency may be called a police force, police department, police service, constabulary, civil guard or protective service. A gendarmerie is a police force that is part of the military, although its members rarely do actual military work.
Most police forces in the United States name themselves as "[Place] Police Department", such as New York City Police Department. State police forces are usually known as either "[State] Highway Patrol" or "[State] State Police". In the United Kingdom, most are "[Place] Police" or "[Place] Constabulary". In Canada and other English-speaking countries, "[Place] Police Service" is common. Ireland's police are called the Garda Síochána.

A law enforcement agency is any agency that enforces the law. In the United States, there are some law enforcement agencies that are not called police forces but carry out similar work, such as the Federal Bureau of Investigations. One common type is a sheriff's office (also sheriff's department), an agency that is led by a sheriff.

Those who carry out policing duties are known as police officers. They may also be known as policemen
Powers
The police have different powers to help them do their job. These powers are different in different countries. Most police officers have the power to arrest people, search people, and search houses/properties. They sometimes carry equipment such as guns, batons, tasers, or pepper spray. The area where police officers can use these powers is called their jurisdiction. If officers are outside of their jurisdiction, another police force with jurisdiction can then use their powers.
Duties
The police deal with:
 Preventing crime and protecting the public. They do this by patrolling on foot in uniform and in police cars. This can stop some forms of criminal behavior.
 Responding to crimes. When someone calls the police to say that a crime is happening, they must send some police officers to arrive at the scene very quickly. They will try to stop the crime and catch the person doing it.
 Investigating crime. This means that the police try to find out who did the crime.
 Arresting and detaining suspects. When the police believe that someone has committed a crime, the police arrest them, take them to the police station and ask them questions. However, it is the prosecutors and not the police who have the final say on whether a suspect gets charged.
To help with emergencies or problems that are not crimes. This may be car accidents, fires, or people who are sick, hurt or lost. The police work with firefighters, ambulances, and rescuers. They might direct traffic, help lost children, or give traffic tickets.
Parts of police departments
Most police departments have officers in two main groups: a "patrol" group with officers who wear uniforms, and a "detective" group with officers who wear normal clothing. 

Patrol officers travel through their area. They may travel by foot, on bicycle or motorcycle, or in marked cars. The cars have warning lights and sirens that can be used. The sirens make a loud sound. Patrol officers enforce motor vehicle and criminal laws. In some locations patrol officers manage the local jail.
Detectives work on investigations that are more complex. They try to find fraud, illegal drugs, and sex crimes like prostitution, human trafficking, and rape. Prostitution is not a crime in all countries.
Not all countries use the same words to describe these groups. In the United Kingdom, for example, patrol officers form the "uniform branch", while detectives work within the CID ("Criminal Investigation Department"). Also in the United Kingdom, not all police officers are armed, these police officers form an "Armed Response Unit" which comes under other names in different constabularies, in the Metropolitan Police Service, it falls under SFC (Specialist Firearms Command) which all MET Armed Police fall under  

Police uniforms, equipment and methods vary depending on the country. In some places, groups of police train for special jobs such as dealing with riots or dealing with highly dangerous criminals.
Police in different countries
Different countries have different ways of organizing their police. Some countries like South Africa, Ireland and New Zealand have just one police force. Other countries have more than one. France has two police forces, one for cities and another for rural areas. Chile also has two, one for patrol and another for investigations.

Some countries have two or more levels of police forces. For example, most policing in Australia is carried out by the six state police forces, but there is also the Australian Federal Police who police the whole country. Germany has a similar system. The United Kingdom and Switzerland have many local police forces and several national agencies, but no actual national police force. In Canada, local governments can choose to either run their own police force or give the job to a bigger one. So most Canadian cities have their own police, while most rural areas are policed by the Royal Canadian Mounted Police, which is also the national police.
The United States has over 17,000 law enforcement agencies. Many areas have four levels of law enforcement agencies. For example, Los Angeles has the Los Angeles Police Department but there are many other agencies that can work in the city. This includes the county-level Los Angeles Sheriff's Department, the state-level California Highway Patrol and over 100 federal (or national) law enforcement agencies.

Worldwide, police are a small percentage of the number of people they serve. On average there are 303.3 police officers per 100,000 people.

Equipment
In most countries, police officers carry guns during their normal duties. In the United Kingdom, New Zealand, Ireland and a few other countries, most police officers do not carry guns. Officers may also carry pepper spray, electric shock weapons (such as tasers), and batons for defense. Police officers also wear handcuffs to detain suspects.

Officers communicate using radio devices. The radios can be on both the uniform and in the patrol vehicle.
Related pages
Police officer
SWAT team
Law enforcement

References

Other websites
1860-1870 picture of  San Fransico Police man
Police History book  
Police Pictures links
Pi () () is a mathematical constant that is the ratio of a circle's circumference to its diameter. This produces a number, and that number is always the same. However, the number is rather strange. The number starts as 3.141592653589793... and continues without end. Numbers like this are called irrational numbers.

The diameter is the largest chord which can be fitted inside a circle. It passes through the center of the circle. The distance around a circle is known as the circumference. Even though the diameter and circumference are different for different circles, the number pi remains constant: its value never changes. This is because the relationship between the circumference and diameter is always the same.

Fundamentals

Definition

 is commonly defined as the ratio of a circle's circumference  to its diameter :

Approximate value
Approximate value

Pi is often written as . It is also an irrational number, meaning it cannot be written as a fraction (), where 'a' and 'b' are integers (whole numbers). This basically means that the digits of pi that are to the right of the decimal go forever—without repeating in a pattern, and that it is impossible to write the exact value of pi as a number. Pi can only be approximated, or measured to a value that is close enough for practical purposes.

A value close to pi is 3.141592653589793238462643... A common fraction approximation of pi is , which yields approximately 3.14285714. This approximation is 0.04% away from the true value of pi. While this approximation is accepted for most of its use in real life, the fraction  is more accurate (giving about 3.14159292), and can be used when a value closer to pi is needed. Computers can be used to get better approximations of pi.

In March 2019, Emma Haruka Iwao calculated the value of pi to 31.4 trillion digits.
History 
Mathematicians have known about pi for thousands of years, because they have been working with circles for the same amount of time. Civilizations as old as the Babylonians have been able to approximate pi to many digits, such as the fraction 25/8 and 256/81. Most historians believe that ancient Egyptians had no concept of pi, and that the correspondence is a coincidence.

The first written reference to pi dates to 1900 . Around 1650 , the Egyptian Ahmes gave a value in the Rhind Papyrus. The Babylonians were able to find that the value of pi was slightly greater than 3, by simply making a big circle and then sticking a piece of rope onto the circumference and the diameter, taking note of their distances, and then dividing the circumference by the diameter.
Knowledge of the number pi passed back into Europe and into the hands of the Hebrews, who made the number important in a section of the Bible called the Old Testament. After this, the most common way of trying to find pi was to draw a shape of many sides inside any circle, and use the area of the shape to find pi. The Greek philosopher Archimedes, for example, used a polygon shape that had 96 sides in order to find the value of pi, but the Chinese in 500  were able to use a polygon with 16,384 sides to find the value of pi. The Greeks, like Anaxagoras of Clazomenae, were also busy with finding out other properties of the circle, such as how to make squares of circles and squaring the number pi. Since then, many people have been trying to find out more and more exact values of pi.
In the 16th century, better and better ways of finding pi became available, such as the complicated formula that the French lawyer François Viète developed. The first use of the Greek symbol "π" was in an essay written in 1706 by William Jones.

A mathematician named Lambert also showed in 1761 that the number pi was irrational; that is, it cannot be written as a fraction by normal standards. Another mathematician named Lindeman was also able to show in 1882 that pi was part of the group of numbers known as transcendentals, which are numbers that cannot be the solution to a polynomial equation.

Pi can also be used for figuring out many other things beside circles. The properties of pi have allowed it to be used in many other areas of math besides geometry, the study of shapes. Some of these areas are complex analysis, trigonometry, and series.

Pi in real life 
There are different ways to calculate many digits of pi. This is of limited use though.
Pi can sometimes be used to work out the area or the circumference of any circle. To find the circumference of a circle, use the formula 2 × π × r (Radius). To find the area of a circle, use the formula π × r² (radius squared). This formula is sometimes written as , where A is the variable for the area.

To calculate the circumference of a circle with an error of 1 mm:
 4 digits are needed for a radius of 30 meters
 10 digits for a radius equal to that of the earth
 15 digits for a radius equal to the distance from the earth to the sun.
20 digits for a radius equal to the distance from the earth to Polaris.
People generally celebrate March 14 as Pi Day, because March 14 is also written as 3/14, which represents the first three numbers 3.14 in the approximation of pi. Pi day was started in 1988 by physicist Larry Shaw at the San Francisco Exploratorium. On March 11, 2009, almost 21 years later  U.S. House Of Representatives passed a resolution proclaiming March 14 to be celebrated as National Pi Day every year.

Related pages
 List of numbers
 Irrational numbers
 Square root of 2
 Golden ratio
 E (mathematical constant)
 Squaring the circle
 Transcendental number

References 

Geometry
Irrational numbers
Transcendental numbers
Mathematical constants
A proper noun or proper name is a noun representing a unique thing (like London, Jupiter, John Hunter, or Toyota), unlike a common noun, which represents a type of thing (like city, planet, person or corporation). Proper nouns are the only nouns in English which always have the first letter capitalized.  

In English, proper nouns don't usually come after an article or other limiting modifier (such as any or some). They are used for a particular person, place, or object. For example, a town called "Newtown" may be, but does not necessarily have to be, a new [recently built] town).

Which nouns are considered proper names depends on language. For example, names of days and months are considered proper names in English, but not in Spanish, French, Swedish, Slovenian or Finnish, where they are not capitalized.

References 

Parts of speech

no:Substantiv#Egennavn vs. fellesnavn
A plastic is a material that can change its shape easily. Many things are made of plastics, usually because making them to the right shape is easy. There are many types of plastic. Some can be shaped only when they are freshly made; then they become hard.  Others are thermoplastic and can be softened by heating them. These plastics can be used for 3D printing, because the plastic will become soft enough to form into different shapes, and then become hard again when they cool down.  

Most plastics are man-made; they do not occur in nature. The process of making plastics is usually quite complicated. Most of the materials that are called plastic are polymers. Polymers are long chains of atoms bonded to each other. In most plastics, the long chain is a chain of carbon atoms with other atoms attached to them. The different atoms and the shape and length of the chains change how the plastic looks and works.
People experimented with plastics based on natural polymers for a very long time. Alexander Parkes, an English inventor (1813-1890), created an early form of plastic in 1855. It was hard but flexible and transparent. He called it "Parkesine" but now it is called "Celluloid."

Old plastics are usually thrown away and put in landfills. Some plastics release toxic fumes when heated. Some plastics are recycled so they won't become waste. Some plastics have other materials added to them, like glass, because they make the plastic stronger and stiffer.

Plastics are mostly petrochemicals, made from natural gas or from petroleum, a type of oil. Chemical engineers refine the petroleum which goes through a heating process. It develops ethylene and propylene, which are the chemical building blocks for many plastics. These chemicals are then combined with other chemicals to produce a polymer.
Today, some of these plastics are also being made without oil. Instead, other sources like plants and bacteria are used to make the plastic. These plastics are called bioplastics. They are useful because they can be eaten by other bacteria instead of throwing them away.

Well-known plastics, and their use 
 Polyamide (usually called nylon)  Women's stockings, gears, car parts, toothbrush bristles
 Polycarbonate – bulletproof glass, compact discs, DVDs.
 Polyethylene – tubes, bottles, shopping bags, milk jugs, body armor (made with polyethylene with especially long chains)
 Polyethylene terephtalate (called PET when used for bottles, and polyester when used for clothes or other materials)
 Polypropylene - food containers, chairs
 Polystyrene - CD cases, plastic cups, plastic forks and knives
 Polyurethane - rubber, foam, shiny coatings on wood and tile
 Polyvinyl chloride (called PVC, usually) - pipes (chemicals can make PVC softer for toys and cushions)
 Polylactic acid (PLA) - 3D printing

References
References

Polymers
Polymer chemistry
Product stewardship includes waste disposal measures in the distribution of an industrial product.  That is, paying for the safe and proper disposal when you pay for the product, and relying on those who sold it to you, to dispose of it.
The slightly more specific idea of product take-back means that the service of waste disposal is paid for at time of purchase.  It is often applied to paint, tires, and other goods that become toxic waste if not disposed of properly.  It is most familiar as the deposit bottle - where one pays for the loan of the bottle at the same time as one purchases what is inside it. The container deposit charged for a deposit bottle may be a fee to buy the bottle, separately from the fee to buy what it contains.  If one returns the bottle, the fee is returned, and the supplier must return the bottle for re-use or recycling.  If not, one has paid the fee, and presumably this can pay for landfill or litter control measures that dispose of say a broken bottle.  Also, since the same fee can be collected by anyone finding and returning the bottle, it is common for people to collect these and return them as a means of surviving.  This is quite common for instance among homeless people.