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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 (⅙), and the possibility of getting a 5 is also one in six, so the chances of getting a 3 then a 5 is ⅙×⅙=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 ⅙×⅙×⅙=⅟216 or 0.00463, which is a much lower 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. |
Probability experiment |
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. |
Protein |
Proteins are long-chain molecules built from small units known as amino acids. They are joined together with peptide bonds. |
They are biochemical compounds consisting 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: |
Proteins are formed via a process called "Protein synthesis". In this process the cell reads the genetic information of the DNA and translates it into a protein. In eukaryotes, this process begins in the Nucleus and ends in the ribosome. In procaryotes all of it is done in the cytoplasm. The general concept is exactly the same for every living being. |
Proteins have different functions depending on their shape. 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 also in the human body. |
Muscles contain a lot 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. |
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. |
Proteins are necessary in an animal's diets, since animals 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. |
The scientist Jöns Jacob Berzelius gave proteins their name, but many other scientists have studied proteins. |
Periodic table |
The periodic table of the chemical elements is a list of known chemical elements. 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. cesium 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. |
The version of the periodic table shown above is the one most used. Other widespread versions are shown below: |
Physiology |
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. |
Planet |
A planet is a large object such as Venus or Earth that orbits a star. Planets are smaller than stars, and they do not produce light. Jupiter is the biggest planet in the Solar System. |
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 of those in the Solar System. As of June 2017, we know of 3,610 other planets. These newly found planets are orbiting other stars: they are "extrasolar" planets. Sometimes people call them "exoplanets". |
The planets are composed of material quite different from the Sun. The Sun is almost entirely composed of hydrogen, and some helium. Its energy comes from the conversion of hydrogen to helium. In contrast, the "terrestrial" planets are composed almost entirely of larger atoms and molecules which "cannot" have come from the Sun. It follows, therefore, that the material which forms those planets must have come from another source or sources. Those sources were the atoms formed in supernovae explosions by much larger and much shorter-lived stars in the Sun's neighbourhood as it moved in the galaxy. This material was captured by the Sun's gravity and pulled along to become the basic material out of which the planets condensed. The same considerations apply to other planetary systems in the galaxy. |
The gas giants are composed of hydrogen gas from the same source as the Sun, plus (at their centres) higher "metallic" elements like the terrestrial planets. This is known from the drive-by data gathered by satellites, and by drive-into probes like the Galileo (spacecraft). There is a huge amount of data collected about each planet. The data is stored on computer files, and there are summary volumes in print. |
The planets in the Solar System have names of Greek or Roman gods, apart from 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. |
Here is a list of planets in the Solar System. They are ordered by how close they are to the Sun, nearest first. |
Astronomers speak about "major" (or true) planets, and minor planets, which are smaller objects that go around the Sun. Some examples of "minor planets" are asteroids, comets, and trans-Neptunian objects. |
Planets in the Solar System are of three sorts: |
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). |
Political problems of China |
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. |
The following territories are claimed by China (PRC and/or ROC) and by another country or more. |
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." |
Police |
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. |
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" (men only), "policewomen" (women only), "peace officers", "constables", "rangers" or "civil guards". In a sheriff's office, they are known as "sheriff's deputies" or "deputies" for short. In Ireland they are known by the Irish language word "gardaí" ("garda" if singular) or as "guards". |
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. |
The police deal with: |
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. |
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. |
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. |
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 communicate using radio devices. The radios can be on both the uniform and in the patrol vehicle. |
Pi |
The number () 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. |
is commonly defined as the ratio of a circle's circumference to its diameter : |
Pi is often written as , or the Greek letter π as a shortcut. Pi is also an irrational number, meaning it cannot be written as a fraction (formula_2), 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 formula_3, 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 formula_4 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. |
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 π, 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. |
There are different ways to calculate many digits of π. 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 C (circumference) = π × (diameter). To find the area of a circle, use the formula π (radius²). This formula is sometimes written as formula_5, where "r" is the variable for the radius of any circle and "A" is the variable for the area of that circle. |
To calculate the circumference of a circle with an error of 1 mm: |
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 started during 2001. |
Proper noun |
A proper noun or proper name is a noun representing a unique thing (such as "London", "Jupiter", "John Hunter", or "Toyota"), as opposed to a common noun, which represents a class of things (for example, "city", "planet", "person" or "corporation"). Proper nouns are the only nouns in English which have the first letter capitalized. |
In English, proper nouns are not normally preceded by an article or other limiting modifier (such as "any" or "some"), and are used to denote a particular person, place, or object without regard to any descriptive meaning the word or phrase may have (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. |
Plastic |
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. |
Product stewardship |
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. |
Legal requirements vary: the bottle itself may be considered simple property of the purchaser of the contents, or, the purchaser may have some obligation to return the bottle to some depot so it can be recycled or re-used. For the more toxic items, it is more likely that returning it is required: |
This principle is applied very broadly beyond bottles to paint and automobile parts such as tires. When purchasing paint or tires in many places, one simultaneously pays for the disposal of the toxic waste they become. In some countries, such as Germany, law requires attention to the comprehensive outcome of the whole extraction, production, distribution, use and waste of a product, and holds those profiting from these legally responsible for any outcome along the way. This is also the trend in the UK and EU generally. In the United States, there have been many class action suits that are effectively product stewardship liability - holding companies responsible for things the product does, which it was never advertised to do. |
Rather than let liability for these problems be taken up by the public sector or be haphazardly assigned one issue at a time to companies via lawsuits, many accounting reform efforts focus on achieving full cost accounting. This is the financial reflection of the comprehensive outcome - noting the gains and losses to all parties involved, not just those investing or purchasing. Such moves have made moral purchasing more attractive, as it avoids liability and future lawsuits. |
So these are partial implementations of a strict service economy ideal. |
Those who advocate these measures are concerned with the later phases of product lifecycle and the comprehensive outcome of the whole production process. It is considered a pre-requisite to a strict service economy interpretation of (fictional, national, legal) "commodity" and "product" relationships. |
Peace |
Peace is a time without any fights or wars. In a larger sense, peace (or peacefulness) can mean a state of harmony, quiet or calm that is not disturbed by anything at all, like a still pond with no ripples. |
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