AcharyaChanakya/simple-wikipedia huggingface dataset:
Melting point is the temperature at which a solid changes to liquid. Most alloys do not have a single melting point. They have a melting range in which the alloy is a mixture of solid and liquid stages. The temperature at which melting just starts is called solidus and the temperature at which the melting is just finished is called liquidus.
The term alloy means a mixture of atoms in which the main substance or the primary constituent is a metal. This primary metal is called the "base" or "matrix".
If an alloy has only two types of atoms, like copper-nickel alloy, then such an alloy is called "binary alloy". If an alloy has three types of atoms, like iron, nickel and chromium, then it is called a "ternary alloy". An alloy with four types of atoms is called a "quaternary alloy" and an alloy with five types of atoms is called a "quinary alloy".
Different varieties or forms of alloys can be made from the same constituent materials (substances from which the alloy is formed). These different forms or varieties can be formed by using different amounts of the constituents. The whole range of possible varieties of an alloy is called a "system". All the forms of alloy having only two constituents are called a "binary system". All forms of an alloy having three constituents are called a "ternary system".
There are some common alloys:
Material is what everything that you can touch is made of. Even material that is too small to touch, is called material. We use materials to make things. We can also call material "physical substances."
"Raw" material is materials such as ores which we can clean and mix with other materials to make another material like steel, for example. Cotton is a raw material used to make textiles, which are materials to make clothes.
The brain is the part of the body which lets animals make sense of things. It gets input from sense organs, and changes behavior in response to this information. In humans, the brain also controls our use of language, and is capable of abstract thought. The brain is the main control centre of the whole body. The brain is made up of special cells called nerves, which are connected with each other and with other nerves in our body. In all animals the delicate brain is protected in some way. In ourselves, and all vertebrates, it is protected by the bones of the skull.
The brain does the thinking, learning, and feeling for the body. For humans, it is the source of consciousness. The brain also controls basic autonomic body actions, like breathing, digestion, heartbeat, that happen automatically. These activities, and much else, are governed by unconscious functions of the brain and nervous system. All the information about the world gathered by our senses is sent through nerves into the brain, allowing us to see, hear, smell, taste and feel things. The brain processes this information, and we experience it as pictures, sounds, and so on. The brain also uses nerves to tell the body what to do, for example by telling muscles to move or our heart to beat faster.
This is generally true but some activity is caused by the spinal cord directly, for example, reflex actions do not involve the brain. In lower animals, a good deal is done without their brain being involved.
All vertebrates have brains and, over time, their brains have evolved to become more complex. Some simple animals, however, like sponges, do not have anything like a brain. Segmented invertebrates have ganglions in each segment, and a ring of nervous tissue around the alimentary canal at the front. This acts to bring sense data from the front into play with the movement of the body.
In mammals, the brain is made of three main parts: the cerebrum, the cerebellum and the brainstem. The surface of the cerebrum is the cerebral cortex, which all vertebrates have. Mammals also have an extra layer, the neocortex. This is the key to the behaviour which is typical of mammals, especially humans.
The cortex has sensory, motor, and association areas. The sensory areas are the areas that receive and process information from the senses. The motor areas control voluntary movements, especially fine movements performed by the hand. The right half of the motor area controls the left side of the body, and vice versa. Association areas produce a meaningful experience of the world, and supports abstract thinking and language. This enables us to interact effectively. Most connections are from one area of the cortex to another, rather than to subcortical areas; The figure may be as high as 99%.
The cerebellum coordinates muscles so they work together. It is also the centre of maintaining position and balance, a vital part of movement helping with simple motor skills.
The brain stem is at the back of the brain (actually underneath it in humans). It joins the rest of the brain with the spinal cord. It has lots of different parts that control different jobs in the body: for instance, the brain stem controls breathing, heartbeat, sneezing, eye blinking, and swallowing. Body temperature and hunger are also controlled by parts of the brain stem.
The volume of the human brain (relative to the size of the whole body) is very large, compared to that of most other animals. The human brain also has a very large surface (called cortex) for its size, which is possible because it is very wrinkled. If the human cortex were flattened, it would be close to a square meter in area. Some other animals also have very wrinkled brains, such as dolphins and elephants. Here is a rule of thumb: the larger an animal is, the larger its brain will be. Even allowing for that, the human brain, and in particular the neocortex, is very large. We know it increased in size four-fold over the last several million years of evolution. There are ideas about why this happened, but no-one is quite sure. Most theories suggest complex social activity and the evolution of language would make a larger brain advantageous. As an additional note, Einstein's brain weighed only 1,230 grams, which is less than the average adult male brain (about 1,400 grams). The detailed organisation of a brain obviously matters, but in ways which are not understood at present.
A human brain accounts for about 2% of the body's weight, but it uses about 20% of its energy. It has about 50–100 billion nerve cells (also called neurons), and roughly the same number of support cells, called "glia". The job of neurons is to receive and send information to and from the rest of the body, while glia provide nutrients and guide blood flow to the neurons, allowing them to do their job. Each nerve cell has contact with as many as 10,000 other nerve cells through connections called synapses.
A neuron (or neurone) is a nerve cell that carries electrical impulses. Neurons are the basic units of our nervous system.
Neurons have a cell body ("soma" or "cyton"), dendrites and an axon. Dendrites and axons are nerve fibers. There are about 86 billion neurons in the human brain, which is about 10% of all brain cells. The human brain has about 16 billion neurons in the cerebral cortex. The neurons are supported by glial cells and astrocytes.
Neurons are connected to one another, but they do not actually touch each other. Instead they have tiny gaps called synapses. These gaps are chemical synapses or electrical synapses which pass the signal from one neuron to the next.
There are three classes of neurons: motor neurons, sensory neurons and interneurons.
Mature neurons never divide: that is the general rule. They do not undergo cell division. In most cases, neurons are generated by special types of stem cells. A type of glial cell, called astrocytes, have also been seen to turn into neurons. In humans, neurogenesis (the origin of new nerve cells) largely ceases during adulthood but in two brain areas, the hippocampus and the olfactory bulb, there is strong evidence for substantial numbers of new neurons.
The largest part of the human brain by far is the neocortex. It has at least ~10 neurons which stay with us from cradle to grave.
The Middle East is a large area of land in the eastern hemisphere. The lands of the Arabian Peninsula and some of the lands of the eastern Mediterranean are part of the Middle East. The Middle East's population is mostly Muslim. The name of the Middle East comes from its position to the east of Europe and to the west of the Far East.
It is normal for the modern countries of Arabia (Saudi Arabia, Oman, Yemen, Bahrain, Jordan, Kuwait, and the United Arab Emirates) to be counted with the modern countries of Iraq, Syria, Lebanon, and Palestine (the State of Palestine and Israel) as part of the Middle East.
The name "Middle East" does not always have the same meaning, and the size of the area is not always the same. When the name Middle East started to be common, it was the name for the lands in between the Near East and the Far East. The Indian subcontinent was part of the Middle East at that time. Now, parts of south-west Asia and northern Africa can count as the Middle East. The land between Egypt and Iran is a common definition. Many countries in the Middle East today are also part of the Near East. Sometimes, people name countries that are far away from these countries as countries in the Middle East. These countries can be in North Africa (like Morocco) and the Indian subcontinent (like Pakistan). This area also has the name Greater Middle East.
Many ancient civilizations began in the Fertile Crescent in the Middle East. These were Sumer, Babylonia and Assyria in the area called Mesopotamia. The Abrahamic religions that believe in one God also started in the Middle East. (Judaism and Christianity began in ancient Palestine and Islam began in Arabia.) Today, the Middle East is the homeland of Arabs, Turks, Persians, Kurds, and Jews, among many other ethnic groups. Islam is the most common religion in the Middle East. Islam came to most of the Middle East's lands in the 7th century AD, during the first Muslim conquests of the Sasanian Empire and of the Roman Empire's lands.
Today, the Middle East is very important because much of the petroleum that other countries use comes from here. There are also many arguments and wars, such as the conflict between Sunni and Shia, the Israeli–Palestinian conflict, and the Syrian civil war.
Warsaw (In Polish: "Warszawa") is the capital of Poland in Masovian Voivodeship. It is also the biggest city in that country. There are about 2,000,000 people living there (1,726,581 as of 31 March 2014). People from Warsaw are called "Varsovians".
There are other names for Warsaw. For example, (Latin, Spanish) and "Varsóvia" (Portuguese), (French), (Italian), (German, Dutch), /"Varshe" (Yiddish), (Lithuanian), (Hungarian) and "Varšava" (Czech)
Warsaw is near the middle of Poland on both sides of the Vistula river, and about 350 km (225 miles) from the Baltic Sea. It is about 100 m (325 ft) above sea level. Warsaw has a humid continental climate ("Dfb" in the Koeppen climate classification).
Warsaw is home to four universities and 62 colleges, and many theatres and art galleries.
People began living here in the 13th century. By the 15th century, Warsaw had grown enough to be called a city. It became the capital of Poland in 1596.
The city was destroyed several times in its history, but every time it was rebuilt. The most important of these times was during the Second World War. Poland had been occupied by Germany between 1939 and 1944. On 1 August 1944, the people of Warsaw started fighting to free their city.
There are lot of attractions in the capital of Poland. The most famous monument of Warsaw is Palace of Culture and Science. There is a palace in Wilanów. The king of Poland John III Sobieski lived there. Many people like going to the Museum of Warsaw Uprising. The uprising started in 1944 during World War II
-Athens, Greece
-Chicago, USA
- Rio de Janerio, Brazil
- The Hague, The Netherlands
Hindu–Arabic numeral system
The Hindu–Arabic numeral system, sometimes known as Hindu–Arabic numbers, is the system of numbers used by almost all the world today. It is a positional notation system. This system has ten basic symbols, they are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. It represent numbers in the decimal number system. The Hindu–Arabic numeral system was first developed by the Hindus. Later, It was introduced to the western world by the Arabs. The Hindu–Arabic numeral system is one of the few numeral systems that use a place value system. This system is now commonly used all over the world.
They originated in India in the 6th or 7th century and were introduced to Europe through the writings of Middle Eastern mathematicians, especially al-Khwarizmi and al-Kindi, about the 12th century. They are very different from previous methods of counting, such as the abacus, and paved the way for the development of algebra. In the past many other systems were used. Fibonacci popularized the Hindu–Arabic numeral system to the Western World.
Point (geometry)
A point is a precise position in space. Imagine touching a piece of paper with a sharp pencil or pen, without making any sideways movement. We know where the point is, but it has no size to speak of.
In geometry, a point has no size, but has a position. This means it has no volume, area or length. We usually represent a point by a small cross 'X' or by a small dot (a small, round shape). Points are always labelled by capital letters (A, B, C...X, Y, Z). It is one of the most fundamental but undefined terms in geometry.
In general, two points can be:
and are always:
Three points can be:
Four points can be:
A line is the path of one point moving. A line has length but no width. A line is a type of geometric figure.
A line is made up of an endless number of points.
A line can be straight or curved. In geometry, the word "line" means a "straight line". A straight line is the shortest distance between two points. A straight line is the line traced by a point moving in a direction that does not change.
A "curved line" is sometimes called a curve. The edge of a circle is not straight and is an example of a curve.
A "line segment" is part of a line. Here is an example of a straight line segment:
Lines can get their names from any two points on the line. For example, if a line contains two distinct points, named formula_1 and formula_2, then the line can be called either formula_3, or formula_4.
Sometimes, lines are also named with just one symbol. In which case, a letter such as formula_5 might be used.
Two lines can be:
Plane (mathematics)
A plane is a perfectly flat surface extending in all directions. It can be thought of as the ceiling of a room, only extended into all directions infinitely. A plane has two dimensions: length and width. All planes are flat surfaces. If a surface is not flat, it is called a "curved surface".
The tool "plane" can be used to create a flat, level surface like the mathematical plane—hence the name.
In geometry, a plane is made up of an infinite number of lines (or points). It has no depth. It is absolutely flat and infinitely large.
A "plane figure" is part of a plane. It is named by the capital letters (such as A, B, C, ...X, Y, Z) that are put at its corners. Sometimes, a single capital pi formula_1 is also used to refer to a plane. A plane can also be named after three points that are not all on the same line.
In general, two planes can be:
In mathematics, a plane is a fundamental two-dimensional object. Intuitively, it looks like a flat infinite sheet of paper. There are several definitions of the plane. They are equivalent in the sense of Euclidean geometry, but they can be extended in different ways to define objects in other areas of mathematics. The only two-dimensional figure in our three-dimensional world is a shadow.
In some areas of mathematics, such as plane geometry or 2D computer graphics, the whole space in which the work is carried out is a single plane. In such situations, the definite article is used: "the plane". Many fundamental tasks in geometry, trigonometry and graphing are performed in the two dimensional space, or in other words, in the plane.
A plane is a surface such that, given any three distinct points on the surface, the surface also contains all of the straight lines that pass through any two of them.
One can introduce a Cartesian coordinate system on a given plane in order to label every point on it with a unique ordered pair, which is composed of two numbers and is the coordinate of the point.
Within any Euclidean space, a plane is uniquely determined by any of the following combinations:
When two straight lines come together, they make an angle. The two lines are called the "sides" of the angle, and they meet at a point. A flat surface (called a plane) also forms an angle when it meets another.
To represent an angle, Greek letters such as formula_1 (alpha), formula_2 (beta), formula_3 (gamma) and formula_4 (theta) are sometimes used. An angle indicates the space between its sides, or the amount of rotation needed to make one side coincide the other.
To measure the size of an angle, we use units called degrees. A degree is a standard unit and we use the symbol ° after a number to show that it is a number of degrees. We can use a decimal number or a fraction for part of a degree, but a degree can also be divided into 60 minutes (1° = 60'), and a minute can be divided into 60 seconds (1' = 60"). So 22.5°, 22° and 22° 30' are all the same angle.
In mathematics, angles can also be (and often are) measured in radians instead of degrees, by using the conversion factor formula_5 (for example, formula_6). Yet another unit of angle is gradian, with formula_7.
Angles are studied in geometry, where an angle where edges meet is often called a vertex. For example, the three sides of a triangle are its "edges" and two of the edges meet at each "vertex". Similarly, two of the six sides (or "faces") of a cube meet at each of its twelve edges, and three edges meet at each of its eight corners (or vertices, which is the plural version of "vertex").
•In a zero angle the lines lie one upon the other thus creating a 0° angle aka the zero angle.
•An angle greater than 0° but less than 90° is called an acute angle.
•An angle of 90° is called a right angle.
An angle greater than 90° but less than 180° is called an obtuse angle.
•An angle that measures 180° is called a straight angle.
An angle greater than 180° and less than 360° is called a reflex angle.
•An angle that has a made or full circle/ completed 360° is called a full or complete angle.
Supplementary angles are two angles with the sum equal to 180°, and complementary angles are two angles with the sum equal to one right angle (90°). On the other hand, two angles that sum to one full circle (360°) are sometimes called explementary angles, or conjugate angles.
People usually use a protractor to measure and draw angles. Sometimes, people use a 360° protractor to measure angles.
List of astronomers
Famous astronomers include:
Other scientists whose work had an impact on astronomy and astrophysics:
Instrument makers, illustrators, etc.:
List of astrophysicists
An astrophysicist is a person whose profession is astrophysics.
List of walls
This is a list of famous walls.
List of vegetables
Some vegetables which are botanically fruits (such as tomatoes) are considered to be vegetables in the culinary (eating) sense. This is why they appear in this article. For sources, see individual pages.
List of terrorist incidents
The following is a list by date of acts and failed attempts that can be considered terrorism.
Note: there is no single official definition of terrorism in common use. Events listed here are commonly called terrorism, or meet some of the commonly used parts of the definition.
See also: aircraft hijacking, Palestinian terrorism, American terrorism, Israeli terrorism, IRA, suicide bombing, List of massacres, assassinations, Dupont Plaza Hotel, GIA
List of telescope types
Astronomical telescopes are divided into subgroups. All telescopes work by collecting electromagnetic radiation and focussing it into an image which may be seen or photographed. The purpose is to see things which are far away in the universe.
The traditional types all work to collect visible light from the sky. Recent types may work outside the visible spectrum. They all have their different advantages and disadvantages and they are used in different areas of astronomy.
Dioptrics.
Telescopes which create their image with an objective that is a convex lens (refractors) are said to be "dioptric" telescopes.
Catoptrics.
Optical systems using mirrors: uses reflected light to form the image.
Catadioptric telescopes use corrector lenses to fix problems in a reflector.
List of shipwrecks
This list of shipwrecks is of those sunken ships whose remains have been found.
List of religions
This is a list of religions and spiritual traditions. Some entries are written more than once.
A group of monotheistic traditions often grouped together because all refer to a patriarch named Abraham.
These religions are those of African cultures who have settled outside of Africa (diaspora). They are also sometimes called Creole religions. They include a number of related religions that developed in the Americas among African slaves and their descendants in various countries of the Caribbean Islands and Latin America, as well as parts of the southern United States. The traditions come from African traditional religions, especially of West and Central Africa.
Religions that have idea of Dharma.
"Main article:" "Sikhism"
Traditionally, these faiths have all been classified as pagan religions, but modern scholars prefer the terms "indigenous", "primal", "folk", or "ethnic".
Traditional religions of the Native American peoples.
List of national parks in Africa
List of languages
This is a partial list of natural languages, arranged alphabetically.
List of endangered languages
A list of endangered languages (with fewer than 1000 speakers or with very fast decline).
In order to judge if a language is actually endangered, the number of speakers is less important than the distribution among age cohorts. There may be 200,000 mother tongue speakers of the Breton language over 50 years of age, but fewer than 2,000 under 25 years of age - thus it is likely Breton will die out in the next half century. On the other hand, while there are 30,000 Ladin language speakers left, almost all children still learn it as their mother tongue - thus Ladin is not endangered in the 21st century.
This is a list of emotions (feelings) felt by humans.
Robert Plutchik's theory defines that the eight basic emotions are:
This theory says that the emotions are:
Charles Darwin's "The Expressions of the Emotions in Man and Animals" was a landmark work which is still used as a source. The following list is taken from the chapter-headings in the book.
The book is famous as being the first scientific book which used photographs as a major part of the evidence. Emotions, Darwin decided, were behavioural traits which evolved. He pointed out how the human face is adapted to show many of these emotions: it has muscles for facial movements which are not possible in other mammals. On the other hand, other mammals do have ways of showing many of these emotions.
Ekman has taken this idea a step further by studying the way people try to hide their emotions. He filmed the tell-tale glimpses of brief moments when true emotion is shown on a person's face.
An academic study using self-reporting of subjects distinguished 27 discrete emotions named as in the following list:
List of earthquakes
The following is a list of major earthquakes:
"The Richter scale was adopted in 1935, and was used in the above table also about earlier earthquakes at a merely indicative title. Earthquakes' effects were once measured after the Mercalli scale, which regards the practical damages that a seismic event causes to infrastructures and houses, and a sort of comparison between the two scale is now in use, especially for ancient events."
List of disasters
This is a list of disasters, both natural and man-made.
Up to this day, most nuclear incidents did not cause many deaths, except for the Chernobyl disaster and Windscale fire. Some of the incidents in the early nuclear age were not well documented or were kept secret. Here is a list of the "known" nuclear incidents.
An attack with much collateral damage may be considered a disaster, such as the attack on KdF Ship Wilhelm Gustloff, 1945, the worst or perhaps second worst maritime incident in history, in terms of loss of life in a single vessel (see also note at the end of the article RMS Titanic).
This is a list of disasters involving objects in flight or near-flight. See also: List of space disasters, List of accidents and incidents on commercial airliners, Incidents in Aviation
List of diseases
This is a list of common, well-known or infamous diseases. This is neither complete nor authoritative. This is not intended to be a list of rare diseases, nor is it a list of mental disorders.
This list includes both common names and technical names for diseases. This is deliberate; where multiple names are in common use for the same disease, all of those names should link to the main article for the disease
List of mental disorders
The following is a list of mental disorders.
List of communist parties
There are a number of communist parties around the world.
In world history, the Russian and Chinese communists are very important.
In Western Europe, the French, Spanish and Italian communist parties are the biggest. They have taken part in either local, regional or central government in those countries.
Some communist parties have different names, such as Socialist Party, Socialist Workers Party, or Workers Party. But most socialist parties are social democratic and not communist.
List of color topics
This is a list of color topics.
List of buildings
Famous or notable buildings with articles about them in Wikipedia include:
Index: A-B - C-D - E-I - J-O -
P-R - S - T-V - W - Y - Z
List of bridges
List of bridges is a work in progress.
List of bones of the human skeleton
A typical adult human skeleton consists of the following 206 bones. Some people have slightly more or fewer. Some bones are called "proximal" meaning nearer the torso, some as "intermediate" and some as "distal" meaning farther.
"In the skull (22)":
"In the middle ears (6):"
"In the throat (1):"
"In the shoulder girdle (4):"
"In the thorax (25)":
"In the vertebral column (24)":
"In the arms (6)":
"In the hands (54)":
"In the pelvis (4):"
"In the legs (8)":
"In the feet (52)":
The infant skeleton has the following bones in addition to those above:
Lists of astronomical objects
List of stars
List of nearest stars
This list of the nearest stars to Earth is by distance in light years (ly). These distances are taken from parallax data determined by the Research Consortium on Nearby Stars (or Recons).
The sources for this information were the Yale Parallax Catalog [Y], Hipparcos [H], Soderhjelm 1999 [S], Tinney 1996 [T]. Stars move, and so distances are as at present only.
Some 52 star systems beyond our own, the Solar System, lie within of the Sun. These systems contain 63 stars. 50 of these are red dwarfs, by far the most common type of star in the Milky Way. Much more massive stars, such as our own, make up the remaining 13. In addition to these "true" stars, scientists have identified 11 brown dwarfs (objects not quite massive enough to fuse hydrogen), and four white dwarfs. White dwarfs are extremely dense collapsed cores that remain after stars such as our Sun have exhausted all fusible hydrogen in their core and have slowly shed their outer layers. Despite the relative proximity of these 78 objects to Earth, only nine are bright enough in visible light to be visible to the naked eye from Earth, 6.5 apparent magnitude. All of these objects are currently moving in the Local Bubble, a region within the Orion–Cygnus Arm of the Milky Way.
This is a list of two types of planets: standard planets and dwarf planets, in the Solar System.
"See List of exoplanets"
Technically, there was never a scientific definition of the term "planet" before 2006. When the Greeks observed the sky thousands of years ago, they discovered objects that acted differently than stars. These points of light seemed to wander around the sky throughout the year. The term "planet" is derived from the Greek word "planetes" - meaning wanderer.
in 2006 the International Astronomical Union (IAU) convened a Planet Definition Committee, deliberated, and ultimately reached consensus on a new definition of planet which leaves us with the eight planets we today consider to comprise the Solar System (thus the exit of Pluto). That new definition: " A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit [meaning: 'there are no other bodies in its path that it must sweep up as it goes around the Sun'.]"
List of galaxies
List of galaxies and galaxy clusters. Because there are so many galaxies in the universe, this list has been divided into several categories.
The first catalog that catalogues galaxies is the Catalogue of Galaxies and of Clusters of Galaxies.
This is list of nearby galaxies to the Milky Way Galaxy, our galaxy. The first four listed below are part of the Local Group of galaxies, a galaxy group containing at least 50 galaxies, including the Milky Way and Andromeda.
This is list of farthest galaxy from Milky Way. Remember, the farther away from a galaxy, the greater the redshift of galaxy. Redshift is when object appear in a red color because the distance is farther away.
Note that the idea that the radius of the observable universe must amount to only 13.8 billion light-years (like the age of universe) is incorrect. Light travel distance (LTD) is time required for light to reach the observer.
(≈) means "almost equal to."
And other galaxies :
List of nearest galaxies
List of satellites of the Milky Way
List of satellites of Milky Way:
"Note: ly means light years"
List of comets
This is a list of some comets in the solar system.
Periodic comets visit us again and again. Non-periodic comets visit us only once. On this list there is a "P" in front of the periodic comets. In front of non-periodic comets there is a "C". There is sometimes a number in front of the "P": it shows the number of times people saw the periodic comet visiting us.
Periodic comets have a special place in astronomy, because their orbits are often the same. We know when they will visit us, and we can plan to watch them, and send space probes to look at them.
On August 24, 1994, the International Astronomical Union (IAU) standardized the way they name this type of comet. This system tells us which comet is which. The IAU chose the letter P for periodic comets and D for periodic comets that were lost or which broke into pieces.
Other letters are C for "non-periodic" comets, and X for comets where we do not know their orbits. It uses A for objects people say are asteroids. Each name starts with a number, so two comets have the same name.
List of stars with confirmed extrasolar planets
List of water sports
Many sports are played in water.
The following is a list of water sports, divided by category. This list is not complete. Some of the sports include only one part related to swimming, as for example Triathlon.
List of waterways
List of wave topics
This is a list of wave topics, by Wikipedia page.
List of waterfalls
This is a list of waterfalls.
List of tunnels
List of tallest structures in the world
This is a list of tallest structures in the world, past and present of any type. Most of the structures are television broadcasting masts. There are also the taller tower-type structures (like the CN Tower) and the taller high rise buildings (like the Sears Tower).
The list also includes some other structures like oil platforms, electrical towers, bridge towers, etc. List is organized by absolute height since it includes many different classes of structures.
This list includes quite a few masts. A mast is a man-made support structure, commonly used on sailing ships as support for sails, or on land as radio masts and towers used to support telecommunication equipment such as radio antennas ("aerials" in the UK).
There is often ambiguity between the terms "tower" and "mast". A tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guys. Both towers and masts have limited floor space and are non-building structures, as opposed to regular buildings which have greater floor space for occupancy. The terminology is further confused through misuse. Skyscrapers are often referred to as "towers" and some towers use the term "mast". Ironically, "skyscraper" has some etymology from references to high sailboat masts.
For practical purposes to keep the list to a reasonable length this part of list contains only notable structures.
This is an "incomplete" list of structures taller tha|N|1,148 feet (350 m) under construction. Please correct (by adding further one or by putting completed structures in the upper table, if current height is over 1,148 feet (350 m)).
The following table is a list of the current tallest structures by each continent thus sea oil platforms are not included (listed by geographic size):
The following table is a list of the all time tallest structures by each continent thus sea oil platforms are not included (listed by geographic size):
List of symbols
This is a list of graphical signs, icons, and symbols.
List of supermarkets
This is a list of supermarkets around the world.
see also, "List of Greek supermarkets"
"For full list, see Supermarkets in the United Kingdom"
"For full list, see Supermarkets in the United States"
An acid is a substance that can donate a hydrogen ion (H) (generally speaking, this will be a proton) to another substance. Acids have a pH less than 7.0.
A chemical can donate a proton if the hydrogen atom is attached to an electronegative atom like oxygen, nitrogen, or chlorine. Some acids are strong and others are weak. The weak acids hold on to some of their protons, while the strong acids let go of all of them. All acids will release hydrogen ions into solutions. The amount of ions that get released per molecule will determine if the acid is weak or strong. Weak acids are acids that partially release the hydrogen atoms that are attached. These acids, then, may lower pH by dissociation of hydrogen ions, but not completely. Weak acids generally have a pH value of 4-6 while strong acids have a pH value of 1 to 3.
A base is an acid's "chemical opposite." A base is a substance that will accept the acid's hydrogen atom. Bases are molecules that can split apart in water and release hydroxide ions.
Acids and bases typically exist together in equilibrium. This means that within a sample of an acid, some molecules will give up their protons and others will accept them. Even water is a mixture of an acidic ion, HO (called a hydronium ion) and a basic ion, OH (called a hydroxide ion). A hydronium ion will give up its proton to a hydroxide ion, forming two molecules of HO, which is neutral. This reaction happens continuously in a sample of water, but overall the sample is neutral because there are equal amounts of hydronium and hydroxide in the sample. For most reactions, however, the acids and bases are not present in equal amounts, and this imbalance is what allows a chemical reaction to occur.
Every acid has a conjugate base formed by removing the acid's proton. Hydrochloric acid (HCl), for example, is an acid and its conjugate base is a chlorine anion, or Cl. An acid and its conjugate base are opposite in strength. Since HCl is a strong acid, Cl is a weak base.
Acids can have different "strengths", some are more reactive than others. More reactive acids are often more dangerous.
Acids can have a lot of different properties depending on their molecular structure. Most acids have the following properties:
Acids can burn the skin, the severity of the burn depending on the type and concentration of the acid. These chemical burns require immediate medical attention.
Because acids donate hydrogen ions, all acids must have hydrogen in them.
Acids are important. Nucleic acids, such as DNA and RNA contain the genetic code. These molecules determine many characteristics of an organism, they are passed from the parents to offspring. DNA contains the plans how to build proteins which are made of amino acids.
Fatty acids and fatty acid derivatives are another group of carboxylic acids that play a significant role in biology. These contain long chains of hydrocarbons and a carboxylic acid group on one end. The cell membrane of nearly all organisms is primarily made up of a phospholipid bilayer, a micelle of hydrophobic fatty acid chains with polar, hydrophilic phosphate "head" groups.
In humans and many other animals, hydrochloric acid is a part of the gastric acid secreted within the stomach. It can help hydrolyze proteins and polysaccharides. It can also convert the inactive pro-enzyme, pepsinogen into the enzyme, pepsin. Some organisms produce acids for defense; for example, ants produce formic acid, and octopi produce a black acid called magneta.
Most acids can be found in nature. Some of these include the following:
White dwarf
A white dwarf is a compact star. Their matter is squashed together. Gravitation has pulled the atoms close together, and taken off their electrons. The mass of a white dwarf is similar to the mass of the Sun, but its volume is similar to that of the Earth.
White dwarfs are the final evolutionary state of all stars whose mass is not high enough to become a neutron star. Over 97% of the stars in the Milky Way will become white dwarf stars. After the hydrogen–fusing lifetime of a main-sequence star ends, it will expand to a red giant which fuses helium to carbon and oxygen in its core. If a red giant does not have enough mass to fuse carbon, around 1 billion K, inactive carbon and oxygen will build up at its center. After shedding its outer layers to form a planetary nebula, it will leave behind the core, which is the white dwarf.
The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. It is not supported by the heat of fusion against gravitational collapse.
A star like our Sun will become a white dwarf when it has run out of fuel. Near the end of its life, it will go through a red giant stage, and then lose most of its gas, until what is left contracts and becomes a young white dwarf.
White dwarfs were discovered in the 18th century. The first white dwarf star, called 40 Eridani B, was discovered on 31 January 1783 by William Herschel. It is part of a three star system called 40 Eridani.
The second white dwarf was discovered in 1862, but was at first thought to be a red dwarf. It was a small star near the star Sirius. This companion star, called Sirius B, had a surface temperature of about 25,000 kelvin, so it was thought of as a hot star. However, Sirius B was about 10,000 times fainter than the primary, Sirius A. Scientists have discovered that the mass of Sirius B is almost the same as that of the Sun. This means that once, Sirius B was a star similar to our own Sun.
In 1917, Adriaan van Maanen discovered a white dwarf which is called Van Maanen 2. It was the third white dwarf to be discovered. It is the closest white dwarf to Earth, except for Sirius B.
A white dwarf has low luminosity (total amount of light given off) but a very hot core. The core might be 10 K, while the surface is only 10 K.
A white dwarf is very hot when it is formed, but since it has no source of energy, it will gradually radiate away its energy and cool. This means that its radiation, which gives it a blue or white colour at the start, lessens over time. Over a very long time, a white dwarf will cool to temperatures at which it will no longer emit light. Unless the white dwarf gets matter from a companion star or some other source, its radiation comes from its stored heat. This is not replaced.
White dwarfs cool slowly for two reasons. They have an extremely small surface area to radiate this heat from, so they cool gradually, remaining hot for a long time. Also, they are very opaque. The degenerate matter that makes up the bulk of a white dwarf stops light and other electromagnetic radiation, so radiation does not carry away much energy.
Eventually, all white dwarfs will cool down into black dwarfs, so called because they lack the energy to create light. No black dwarfs exist yet because it takes longer than the current age of the universe for a white dwarf to cool down. A black dwarf is what will be left of the star after all of its energy (heat and light) is used up.
White dwarfs may re-ignite and explode as supernovas if they get more material. There is a maximum mass for a white dwarf to remain stable. This is known as the Chandrasekhar limit.
A dwarf might pull in material from a companion star, for example, bringing it over the Chandrasekhar limit. The extra mass would start a carbon-fusion reaction. Astronomers think this re-igniting might be the cause of Type Ia supernovas.
A beach is a landform along the coast of an ocean, sea, lake, or river. It usually consists of loose particles, such as sand, gravel, shingle, or pebbles. The particles of a beach are sometimes biological in origin, such as mollusc shells or bits of coral and sometimes bits of igneous rock, but the most common mineral in beaches is quartz.
Beaches are natural landing and launching places for boats, and landing craft are specially made for beaches.
People often use beaches for recreation. They swim, bask in the sun, or just relax. The most popular beaches have fine white or light-colored sand and warm water to swim in. Beaches are also used for diving or for seeing marine life.
Among the world's most popular and well-known beaches are Aruba (Dutch Caribbean), Long Beach (Canada), Copacabana Beach (Brazil), Hot Water Beach (New Zealand), Megan Bay (St. Thomas), Kailua Beach (Hawaii), Zandvoort Beach (Netherlands), Jeffreys Bay (South Africa) and Bondi Beach (Australia).
Taking holidays on the beach is something of a British cultural export. Early railways in the 19th century took people to places they had never seen before. This tourism was made possible by the industrial revolution. Whole seaside resort towns grew to support visitors, where before there were just villages. Vacations at the sea became common all over the world.
Beaches are never static. They are always being built up or eroded, more quickly than other landforms. Over time the boundary between the land and the sea changes. New Romney, a small town in Kent, is one of the Cinque Ports, a mile from the sea. In Henry VIII's time it was a port on the south coast of England. The growth of Dungeness has cut it off from the sea. Dungeness is a huge shingle beach.
A mental illness is an illness of the mind. People with a mental illness may behave in strange ways or have strange thoughts in their view or the view of others. Mental illnesses can affect the day to day functioning of a person.
Mental illnesses develop during the life of a person. This may be linked to genes and experience. What is considered as a mental illness has changed over time. What is considered to be a mental illness may not be one in a different culture. The Diagnostic and Statistical Manual of Mental Disorders (DSM) by the American Psychiatric Association is used around the world.
People with a mental illness sometimes have problems dealing with other people, or struggle with daily functioning. Treatment and certain medications can help people with daily functioning.
In some cases, mental illnesses change the way the brain works. Many conditions which affect the brain are not mental illnesses, as they do not change the way in which people think: Neither epilepsy nor Parkinson's disease is a mental illness, yet both affect the brain.
According to the New Freedom Commission on Mental Health in the United States, the most common type of disability in the United States is major mental illnesses (which include major depression, bipolar disorder, personality disorders, body dysmorphic disorder, schizophrenia, and obsessive-compulsive disorder).
Thirty-three percent of North American adults will have a mental illness in a given year, according to the National Alliance on Mental Illness. But in more than half of these cases, the mental illness is not bad enough to disrupt daily life activities.
There is a genetic basis which makes some people more likely to develop mental illness. A study published in "The Lancet", a medical journal, found the same set of genetic markers in people with five different disorders: schizophrenia, bipolar disorder, autism, major depression, and attention deficit hyperactivity disorder (ADHD).
Mental illnesses can be treated by:
Some more controversial treatments include
Many counties have laws that permit to treat people against their will.
Even though the media show this differently, studies have shown that people with a severe mental illness are not necessarily violent. Statistically, violence is often caused by factors such as drug abuse, or those related to the personal, social and economic situation.
Findings show that people with a mental illness that live in the community will be victims of violence more often that they will be those starting or spreading it. A study that looked at people diagnosed with "severe mental illness" living in a US inner-city area found that a quarter of them had been victims of at least one violent crime over the course of a year; this proportion was eleven times higher than the average. For people which have been diagnosed with a mental illness it is more difficult to get a trial started, because fewer people believe them, and many people have a prejudice against people with a mental illness.
There are a few specific diagnoses which are defined by conduct problems and violence. These include conditions such as childhood conduct disorder, adult antisocial personality disorder or psychopathy. There are conflicting findings about how much specific symptoms are linked to an increase in violent behaviour. These symptoms include psychosis (hallucinations or delusions) that can occur in disorders such as schizophrenia, delusional disorder or mood disorder. The factors that lead to violent behaviour are more often demographic or economic in nature, such as being young, male, of lower socioeconomic status or of abusing drugs, including alcoholism, to which some people are particularly vulnerable.
Some studies show that disabled people are sometimes treated badly. For example, people with mental illness may deal with ableism. An example of ableism is insults, for example calling a mentally ill person a "retard".
High-profile cases have led to fears that serious crimes, such as homicide, have increased because people with certain mental illnesses are not treated in specialized institutions, but the evidence does not support this conclusion. Violence that does occur in relation to mental disorder (against the mentally ill or by the mentally ill) typically occurs in the context of complex social interactions, often in a family setting rather than between strangers. It is also an issue in health care settings and the wider community.
Depression (mental illness)
Depression (also called major depressive disorder, unipolar depression or clinical depression) is a mental illness. Many people think that depression just means a person is very sad. However, depression can cause many symptoms in the body as well as mood problems.
The ICD-10 is used around the world to diagnose people with illnesses like depression. According to the ICD-10, for a person to be diagnosed with depression, their symptoms have to last for at least two weeks. The symptoms must happen every day, or almost every day. These symptoms also have to cause problems in a person's life (like their work life, family life, social life, or other important parts of their life).
Usually, for depression to be diagnosed, a person must have five or more of these symptoms:
Most people who have not had depression do not completely understand its effects. Instead, they see it as simply being sad. Since it is not understood, many people criticize people with depression for not helping themselves.
Some people with depression die by suicide. Depression is one of the mental illnesses that can cause a person to have suicidal thoughts.