title: Scottish people

text: Historically, Scottish people have spoken many different languages and dialects. The Pictish language, Norse, Norman-French and Brythonic languages have been spoken by forebears of Scottish people. However, none of these is in use today. The remaining three major languages of the Scottish people are English, Scots (various dialects) and Gaelic. Of these three, English is the most common form as a first language. There are some other minority languages of the Scottish people, such as Spanish, used by the population of Scots in Argentina.


title: Scottish people

text: The Norn language was spoken in the Northern Isles into the early modern period – the current Shetland and Orcadian dialects are heavily influenced by it to this day.


title: Scottish people

text: There is still debate whether Scots is a dialect or a language in its own right, as there is no clear line to define the two. Scots is usually regarded as a midway between the two, as it is highly mutually intelligible with English, particularly the dialects spoken in the North of England as well as those spoken in Scotland, but is treated as a language in some laws.


title: Scottish people

text: After the Union of Crowns in 1603, the Scottish Court moved with James VI & I to London and English vocabulary began to be used by the Scottish upper classes. With the introduction of the printing press, spellings became standardised. Scottish English, a Scottish variation of southern English English, began to replace the Scots language. Scottish English soon became the dominant language. By the end of the 17th century, Scots had practically ceased to exist, at least in literary form. While Scots remained a commonly spoken language, the southern Scottish English dialect was the preferred language for publications from the 18th century to the present day. Today most Scottish people speak Scottish English, which has some distinctive vocabulary and may be influenced to varying degrees by Scots.


title: Scottish people

text: Lowland Scots, also known as Lallans or Doric, is a language of Germanic origin. It has its roots in Northern Middle English. After the wars of independence, the English used by Lowland Scots speakers evolved in a different direction from that of Modern English. Since 1424, this language, known to its speakers as "Inglis", was used by the Scottish Parliament in its statutes. By the middle of the 15th century, the language's name had changed from "Inglis" to "Scottis". The reformation, from 1560 onwards, saw the beginning of a decline in the use of Scots forms. With the establishment of the Protestant Presbyterian religion, and lacking a Scots translation of the Bible, they used the Geneva Edition. From that point on, God spoke English, not Scots. Scots continued to be used in official legal and court documents throughout the 18th century. However, due to the adoption of the southern standard by officialdom and the Education system the use of written Scots declined. Lowland Scots is still a popular spoken language with over 1.5 million Scots speakers in Scotland. Scots is used by about 30,000 Ulster Scots and is known in official circles as Ullans. In 1993, Ulster Scots was recognised, along with Scots, as a variety of the Scots language by the European Bureau for Lesser-Used Languages.


title: Scottish people

text: Scottish Gaelic is a Celtic language with similarities to Irish. Scottish Gaelic comes from Old Irish. It was originally spoken by the Gaels of Dál Riata and the Rhinns of Galloway, later being adopted by the Pictish people of central and eastern Scotland. Gaelic ("lingua Scottica", "Scottis") became the "de facto" language of the whole Kingdom of Alba. Meanwhile, Gaelic independently spread from Galloway into Dumfriesshire. It is unclear if the Gaelic of 12th-century Clydesdale and Selkirkshire came from Galloway or other parts of Scotland. The predominance of Gaelic began to decline in the 13th century, and by the end of the Middle Ages, Scotland was divided into two linguistic zones, the English/Scots-speaking Lowlands and the Gaelic-speaking Highlands and Galloway. Gaelic continued to be spoken widely throughout the Highlands until the 19th century. The Highland clearances actively discouraged the use of Gaelic, and caused the number of Gaelic speakers to fall. Many Gaelic speakers emigrated to countries such as Canada or moved to the industrial cities of lowland Scotland. Communities, where the language is still spoken natively, are restricted to the west coast of Scotland; especially the Hebrides. However, some Gaelic speakers also live in the cities of Glasgow and Edinburgh. A report in 2005 by the Registrar General for Scotland based on the 2001 UK Census showed about 92,400 people or 1.9% of the population can speak Gaelic, while the number of people able to read and write it rose by 7.5% and 10% respectively. Outwith Scotland, there are communities of Scottish Gaelic speakers such as the Canadian Gaelic community; though their numbers have also been declining rapidly. The Gaelic language is recognised as a minority language by the European Union. The Scottish Parliament is also seeking to increase the use of Gaelic in Scotland through the Gaelic Language (Scotland) Act 2005. Gaelic is now used as a first language in some schools and is prominently seen in use on dual language road signs throughout the Gaelic-speaking parts of Scotland.


title: Scottish people

text: The modern people of Scotland remain a mix of different religions and no religion. Christianity is the largest faith in Scotland. In the 2011 census, 53.8% of the Scottish population identified as Christian. The Protestant and Catholic divisions still remain in the society. About 14.4 per cent of the population identifies as Catholic, according to the Scottish Household Survey for 2014. In Scotland the main Protestant body is the Church of Scotland which is Presbyterian. The high kirk for Presbyterians is St Giles' Cathedral. In the United States, people of Scottish and Scots-Irish descent are chiefly Protestant, especially in the US South, with many belonging to the Baptist or Methodist churches or various Presbyterian denominations.


title: Scottish people

text: According to the Social Scottish Attitudes research, 52% of Scottish people identified as having no religion in 2016. As a result, Scotland has thus become a secular and majority non-religious country, unique to the other UK countries.


title: Scottish people

text: The modern games of curling and golf originated in Scotland. Both sports are governed by bodies headquartered in Scotland, the World Curling Federation and the Royal and Ancient Golf Club of St Andrews respectively. Scots helped to popularise and spread the sport of association football; the first official international match was played in Glasgow between Scotland and England in 1872.


title: Scottish people

text: Many Scottish surnames have become anglicised over the centuries. This reflected the gradual spread of English, initially in the form of Early Scots, from around the 13th century onwards, through Scotland beyond its traditional area in the Lothians. It also reflected some deliberate political attempts to promote the English language in the outlying regions of Scotland, including following the Union of the Crowns under King James VI of Scotland and I of England in 1603, and then the Acts of Union of 1707 and the subsequent defeat of rebellions.


title: Scottish people

text: However, many Scottish surnames have remained predominantly Gaelic albeit written according to English orthographic practice (as with Irish surnames). Thus "MacAoidh" in Gaelic is "Mackay" in English, and "MacGill-Eain" in Gaelic is "MacLean" and so on. "Mac" (sometimes "Mc") is common as, effectively, it means "son of". "MacDonald", "MacDougal", "MacAulay", "Gilmore", "Gilmour", "MacKinley", "Macintosh", "MacKenzie", "MacNeill", "MacPherson", "MacLear", "MacAra", "Bruce", "Campbell", "Fraser", "Oliver", "Craig", "Lauder", "Menzies", "Stewart", "Galloway" and "Duncan" are just a few of many examples of traditional Scottish surnames. There are, of course, also the many surnames, like "Wallace" and "Morton", stemming from parts of Scotland which were settled by peoples other than the (Gaelic) Scots. The most common surnames in Scotland are "Smith" and "Brown", which each come from more than one origin: e.g. Smith might be a translation of Mac a' Ghobhainn (thence also e.g. MacGowan), and Brown can refer to the colour, or be akin to MacBrayne.


title: Scottish people

text: Anglicisation is not restricted to language. In his "Socialism: critical and constructive", published in 1921, future British Prime Minister Ramsay MacDonald wrote: "The Anglification of Scotland has been proceeding apace to the damage of its education, its music, its literature, its genius, and the generation that is growing up under this influence is uprooted from its past, and, being


title: Albinism

text: Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino.


title: Albinism

text: Varied use and interpretation of the terms mean that written reports of albinistic animals can be difficult to verify. Albinism can reduce the survivability of an animal; for example, it has been suggested that albino alligators have an average survival span of only 24 hours due to the lack of protection from UV radiation and their lack of camouflage to avoid predators. It is a common misconception that all albino animals have characteristic pink or red eyes (resulting from the lack of pigment in the iris allowing the blood vessels of the retina to be visible), however this is not the case for some forms of albinism. Familiar albino animals include in-bred strains of laboratory animals (rats, mice and rabbits), but populations of naturally occurring albino animals exist in the wild, e.g. Mexican cave tetra. Albinism is a well-recognized phenomenon in molluscs, both in the shell and in the soft parts. It has been claimed by some, e.g. that albinism can occur for a number of reasons aside from inheritance, including genetic mutations, diet, living conditions, age, disease, or injury. However, this is contrary to definitions where the condition is inherited.


title: Albinism

text: Oculocutaneous albinism (OCA) is a clearly defined set of seven types of genetic mutations which reduce or completely prevent the synthesis of eumelanin or pheomelanin, resulting in reduced pigmentation. Type I oculocutaneous albinism (OCA1a) is the form most commonly recognised as 'albino' as this results in a complete absence of melanin in the skin, hair/fur/feathers, and pink pupils, however this has led many to assume that all albinos are pure white with pink pupils, which is not the case.


title: Albinism

text: In plants, albinism is characterised by partial or complete loss of chlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes with photosynthesis, which can reduce survivability. Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".


title: Albinism

text: Biological pigments are substances produced by living organisms that have a colour resulting from selective colour absorption. What is perceived as a plant or animal's "colour" is the wavelengths of light that are not absorbed by the pigment, but instead are reflected. Biological pigments include plant pigments and flower pigments.


title: Albinism

text: Animals can appear coloured due to two mechanisms, pigments and structural colours. Animals may have both biological pigments and structural colours, for example, some butterflies with white wings.


title: Albinism

text: Many animal body-parts, such as skin, eyes, feathers, fur, hair, scales and cuticles, contain pigments in specialized cells called chromatophores. These cells are found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for colouration. The term chromatophore can also refer to coloured, membrane-associated vesicles found in some forms of photosynthetic bacteria. Chromatophores are largely responsible for generating skin and eye colour in poikilothermic animals and are generated in the neural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour under white light:


title: Albinism

text: Animals can also appear coloured due to structural colour, the result of coherent scattering perceived as iridescence. The structures themselves are colourless. Light typically passes through multiple layers and is reflected more than once. The multiple reflections compound one another and intensify the colours. Structural colour differs according to the observer's position whereas pigments appear the same regardless of the angle-of-view. Animals that show iridescence include mother of pearl seashells, fish, and peacocks. These are just a few examples of animals with this quality, but it is most pronounced in the butterfly family.


title: Albinism

text: The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments including porphyrins, carotenoids, anthocyanins and betalains.


title: Albinism

text: Definitions of albinism vary and are inconsistent. While they are clear and precise for humans and other mammals, this is because the majority of mammals have only one pigment, melanin. Many animals have pigments other than melanin, and some also have structural colours. Some definitions of albinism, whilst taking most taxa into account, ignore others. So, "a person or animal with very pale skin, white hair or fur, and pink eyes caused by a medical condition that they were born with" and "a person or animal with white skin and hair and pink eyes" do not include feathers, scales or cuticles of birds, fish and invertebrates, nor do they include plants. Some definitions are too broad to be of much use, e.g. "an animal or plant with a marked deficiency in pigmentation".


title: Albinism

text: Other definitions of albinism encompass most of the major animal taxa, but ignore the several other pigments that non-mammalian animals have and also structural colouration. For example, "Absence of the pigment melanin in the eyes, skin, hair, scales, or feathers." refers only to the pigment melanin.


title: Albinism

text: Because of the various uses of different terms applied to colouration, some authors have indicated that the colour of the eyes is the defining characteristic of albinism, e.g. "This leads to a good diagnostic feature with which to distinguish leucistic and albino individuals – the colour of the eye." However, there are multiple forms of albinism – currently seven types recognised for humans – most of which do not result in red or pink pupils.


title: Albinism

text: The term "partial albino" is sometimes used in the literature, however, it has been stated that "A common misnomer is 'partial albino' – this is not possible since albinism affects the whole plumage of a bird, not just part" and the definition of albinism precludes the possibility of "partial albinism" in which a mostly white bird shows some form of melanin pigmentation. "It is simply impossible, just like being 'partially pregnant' ". Conditions that are commonly termed "partial albino" include neural crest disorders such as piebaldism, Waardenburg syndrome, or other depigmentation conditions such as vitiligo. These conditions result from fundamentally different causes to the seven types of oculocutaneous albinism that have been identified in humans (and confirmed in some other animals) and the use of the term "partial albino" is therefore misleading.


title: Albinism

text: One definition states that "albinism, (from the Latin albus, meaning "white"), hereditary condition characterized by the absence of pigment in the eyes, skin, hair, scales, or feathers", however, this does not encompass invertebrates, nor does it include plants. Furthermore, it could be interpreted that "...absence of pigment..." does not include an absence of structural colours.


title: Albinism

text: The lack of clarity about the term is furthered when the name of an animal includes the term "albino" although the animals (clearly) do not have the condition. For example, the albino gaur has this name because it is ash-grey whereas other gaur are almost black.


title: Albinism

text: A clear definition appears to be – "Congenital absence of any pigmentation or colouration in a person, animal, or plant, resulting in white hair and pink eyes in mammals." Whilst this does not state specifically that non-mammalian albino animals (or plants) are white, this can be inferred from "...absence of any pigmentation or colouration..." Due to the varied use and interpretation of the term "albino", written reports of albinistic organisms can often not be verified.


title: Albinism

text: Melanin is an organic pigment that produces most of the colour seen in mammals. Depending on how it is created, melanin comes in two colour ranges, eumelanin (producing dark browns and blacks) and pheomelanin (producing light reddish tans and blondes). The dark and light melanins have their influence either alone or in conjunction, making either plain or multi-coloured coats. Sometimes, in a condition called agouti, they make multi-coloured individual hairs. The production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase. Mammals have a gene that codes for the presence of tyrosinase in cells – called the TYR gene. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal becomes an albino. Besides the TYR gene, several other genes can cause albinism. This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. In mice, a total of 100 genes are known to affect albinism.


title: Albinism

text: All the genetic traits for albinism are recessive traits. This means that their influence is hidden when paired with stronger traits. For the recessive albino trait to be expressed in a mammal, the offspring must inherit a recessive gene from both parents.


title: Albinism

text: Albinism occurs throughout the animal kingdom. The condition is most commonly seen in birds, reptiles and amphibians, but more rarely seen in mammals and other taxa. It is often difficult to explain occasional occurrences, especially when only one documented incidence has occurred, such as only one albino gorilla and one albino koala. In mammals, albinism occurs once in every 10,000 births, but in birds, the rate is once in every 1,764 births.


title: Albinism

text: Some species, such as white peacocks, swans and geese, are not believed to be true albinos, as they do not have red eyes, rather, their colouration is suggested to be the expression of a white fur or feather gene, not a lack of melanin.


title: Albinism

text: Melanin functions in the normal development of various parts of the eye, including the iris, retina, eye muscles, and optic nerve. The absence of melanin results in abnormal development of eyes and leads to problems with focusing, and depth perception. The eyes of albino animals appear red because the colour of the red blood cells in the retina can be seen through the iris, which has no pigment to obscure this. Some albino animals may have pale-blue eyes due to other colour generating processes. Albino vertebrates exposed to intense light typically lose photoreceptors due to apoptosis.


title: Albinism

text: In all albino mammals studied, the centre of the retina is under-developed and there is a deficit of rod cells; the central ganglion cell density is approximately 25% below normal (except for the gray squirrel). In nearly all mammals, the overwhelming majority of photoreceptors are rods rather than cones. Albinism specifically affects the rod cells, but the number and distribution of the cones is unaffected. In contrast, the retinas of birds are cone rich meaning that the vision of albino birds is affected less than albino mammals.


title: Albinism

text: Melanin protects the skin from ultra-violet radiation in sunlight. Melanosomes block harmful electromagnetic radiation from the sun while allowing beneficial frequencies to enter the body. This means some animals may die from UV radiation due to a lack of protection. Albino humans must use an excessive amount of sunscreen, even if the sun is hidden behind the clouds.


title: Albinism

text: Many animals with albinism lack their protective camouflage and are therefore less able to conceal themselves from their predators or prey: The survival rate of animals with albinism in the wild can be low, however, it has been stated that in studies where animals had many places to hide, predators captured albino and normally coloured animals at the same rate. Furthermore, albino animals may be excluded from families or other groups, or rejected as mates.


title: Albinism

text: The novelty of albino animals has occasionally led to their protection by groups such as the Albino Squirrel Preservation Society. They have also been protected in studies on their ecology, sociology and behaviour.


title: Albinism

text: Studies on medaka fish in the laboratory, i.e. with no predators, sufficient food supply, controlled temperatures, etc., found that albinos had considerably reduced viability; from 800 albino embryos, only 29 survived to full adulthood. Early studies on fish led some researchers to describe albinism as a "semi-lethal mutation".


title: Albinism

text: Pigmentation disorders such as albinism are occasionally associated with hearing impairments in mice, rats, guinea pigs and cats.


title: Albinism

text: Intentionally bred albinistic strains of some animal species are commonly used as model organisms in biomedical research and also as pets. Examples include the BALB/c mouse and Wistar and Sprague Dawley rat strains, laboratory rabbits and ferrets. Albino axolotl (an amphibian) are also used widely in the laboratory as their transparent skin allows observation of the underlying tissues during limb regeneration. Some researchers have argued that albino animals are not always the best choice for scientific studies due to the consequences of albinism (e.g. hearing and visual impairments).


title: Albinism

text: Many individual albino mammals are in captivity and were caught while young. It is doubtful whether these individuals would have survived to become adults without the protection and care they receive in captivity.


title: Albinism

text: It has been claimed that "Squirrels are the only known albino mammal to survive successfully in the wild". The retina of the squirrel ("Sciurus carolinensis") is unusual for mammals as it is rich in cones. Central cell densities are less than 5% lower in albino squirrels than in pigmented individuals. This relatively minor disruption to vision is thought to assist in the survivability of albino squirrels in the wild. This is supported by observations that the behaviour of albinos in the wild, e.g. leaping from branch to branch, is similar to pigmented squirrels.


title: Albinism

text: A 2012 survey of the literature reported that in India, there were several records of albino mammals including the tiger, lesser mouse-tailed bat, chital, common palm civet, northern palm squirrel, five-striped palm squirrel and wild boar.


title: Albinism

text: Albino macaques have been reported in several occasions including a toque macaque ("M. sinica"), rhesus macaque ("M. mulatta"), and bonnet macaque ("M. radiata").


title: Albinism

text: Albinism was observed in jungle cats ("Felis chaus") and jackals ("Canis aureus") along the coastline of the southern Western Ghats (Kerala and Kanyakumari coast, India). Albinism was observed in jungle cats from the Amaravila area of Trivandrum district in the Kerala State. Albinism in jackals was observed from the Polooni area in Malappuram district and Chaliyam area of Calicut district (Kerala). As albinism is observed in those areas where the density of these mammals is comparatively low, it is concluded that continuous inbreeding could be the reason for expression of albinism.


title: Albinism

text: A study on albinistic prairie voles ("Microtus ochrogaster") found that albinism in this species conferred an advantage for the males compared to the wild-type; albino males had higher mount frequencies than wild-type males. In addition, the albinos had greater differential fertilizing capacity.


title: Albinism

text: Albinism can also occur in marsupials and monotremes as well such as echidnas, kangaroos, koalas, possums, wallabies and wombats as well.


title: Albinism

text: The costs of albinism for marine mammals may include reduced heat absorption in colder waters, poor camouflage from predators, increased sensitivity to sunlight, and impaired visual communication. Despite the costs, some individuals do reach adult age and breeding status.


title: Albinism

text: Albino dolphins were first sighted in the Gulf of Mexico in 1962. Since 1994, three further individuals have been seen. These tend to be pink in colour due to blood vessels showing through the blubber and unpigmented skin.


title: Albinism

text: A report published in 2008 stated that in marine mammals, "anomalously white" individuals have been reported for 21 cetacean species and 7 pinniped species but there were no known reports of anomalously white sea otters ("Enhydra lutris") or sirenians.


title: Albinism

text: Whales and dolphins also may appear white if extensively scarred, or covered with a fungus, such as "Lacazia loboi".


title: Albinism

text: Famous albino mammals include Migaloo, a humpback whale living off the coast of Australia; Pinky, a bottlenose dolphin living in and around in Calcasieu Lake, Louisiana; Carolina Snowball, a popular albino bottlenose dolphin displayed at the Miami Seaquarium in the early 1960s; Snowflake, a Barcelona Zoo gorilla, and Mahpiya Ska, (Sioux for White Cloud), a buffalo in Jamestown, North Dakota, and inspiration for Herman Melville's novel "Moby-Dick", a sperm whale known as Mocha Dick.


title: Albinism

text: The most important pigments that determine plumage colouration in birds are melanines and carotenoids. The latter are ingested in food and transformed into colour pigments by enzymes. Aberrations in this pigmentation are mostly caused by food deficiencies and usually do not have a genetic basis. Well-known examples are flamingos, which owe their distinct pink colour to the presence of red carotenoids in their natural food. When these carotenoids are in short supply, these birds appear white after the next moult. Mutations causing changes in carotenoid-based colour pigments are rare; melanine mutations occur much more frequently. Two types of melanin, eumelanin and phaeomelanin, are present in birds. In the skin and eyes, only eumelanin is present. In some bird species, the colour is completely caused by eumelanin, however, both types of melanin are found in most species. In birds, albinism has been defined as "a total lack of both melanins in feathers, eyes and skin as a result of an inherited absence of tyrosinase", however, this ignores the effects of other pigments and structural colours.


title: Albinism

text: An albino bird has a white beak, white plumage, non-coloured skin, white talons and pink or red eyes.


title: Albinism

text: Albinism is only seen in about 1 of every 1,800 birds. The two most common species of albino birds are the common house martin and the American robin. Famous albino birds include "Snowdrop", a Bristol Zoo penguin.


title: Albinism

text: However, it has been argued that the definition of albinism precludes the possibility of "partial albinism" in which a mostly white bird shows some form of melanin pigmentation. "It is simply impossible, just like being 'partially pregnant'.


title: Albinism

text: As with other animals, it has been stated that for fish to be properly described as "albino", they must have a white body and pink or red eyes.


title: Albinism

text: Zebrafish have three types of chromatophores—iridophores, melanophores, and xanthophores—which produce silver, black, and yellow pigmentation respectively. Zebrafish that lack iridophores are known as "roy mutants", those that lack melanophores as "albino mutants", and those which lack both melanophores and iridophores are "ruby mutants". The gross eye morphology, feeding and swimming behaviours between wild-type and albino zebrafish were indistinguishable, except under dim or bright light or low contrast.


title: Albinism

text: In mammals, albinism is occasionally associated with hearing impairments. However, when tested, there was no differences in responses between wild-type and albinistic European wels catfish ("Silurus glanis") and South American bronze catfish ("Corydoras aeneus"). Similarly, Mexican blind cave fish ("Astyanax mexicanus") do not differ in hearing sensitivity from the normally pigmented and eyed surface-dwelling populations. Fish lack melanin in the inner ear, meaning that hearing in fishes is less likely to be affected by albinism than in mammals.


title: Albinism

text: There are several reports of total albinism in both freshwater and marine fish, however, frequently captured albino fish are only reported in aquarium magazines and local newspapers.


title: Albinism

text: The incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals (e.g. arsenic, cadmium, copper, mercury, selenium, zinc).


title: Albinism

text: In the wild, albinism is reasonably common in the teleosts, especially the Pleuronectiformes (flatfish), however, it is rarely reported in the elasmobranchs. Albinism has been reported in hagfish, lampreys, sharks, rays and numerous teleost fishes, e.g. catfishes, grunts or cyprinids.


title: Albinism

text: Albino and normally pigmented channel catfish ("Ictalurus punctatus") differ in their characteristics. Normal individuals of this species are superior to albinos in body weight and total length. Albinos crossed with other albinos require 11 days longer to spawn and produce smaller egg masses. These masses contain eggs of lighter weight with poorer hatchability than crosses of normal fish. The albino fish have lower survival rates than normal fish but dress-out percentages are nearly equal.


title: Albinism

text: Some wild cave fish have populations that are albinistic. The Mexican cave tetra is a species that has evolved specialized characteristics in a series of independent caves. One of these is albinism linked to the Oca2 gene, a known pigmentation gene, This trait has evolved independently in at least two caves.


title: Albinism

text: In the class Chondrichthyes, several species of naturally occurring albino rays and sharks have been recorded. Furthermore, an albino individual spotted ratfish ("Hydrolagus colliei") from the order Chimaeriformes has been reported.


title: Albinism

text: There are several reports of albino lampreys and it has been estimated that this occurs at a frequency of one in 100,000 normal individuals.


title: Albinism

text: Many reptiles labeled as albino are, in fact, not completely lacking in all colour pigments. They are actually amelanistic, not albino. Reptiles often possess at least two pigments. Among the most common are xanthin (yellow) and erythrin (red). An amelanistic reptile therefore, may still have pale yellow, orange, or red pigmentation.


title: Albinism

text: The California Academy of Science, in the Steinhart Aquarium, as of 2015, has on display an albino American alligator named "Claude". The alligator is partially blind because of lack of pigment in its eyes. The albino alligator hatched from the egg in 1995 in Florida, and was brought to the academy in 2008. This alligator would not have survived in the wild because its whiteness would have made it too easy a prey object. The only known albino alligators are in captivity. While extremely rare, white-coloured crocodiles and alligators do exist in other places. However, most of these animals are leucistic given that they have a general loss of pigmentation with some colour tinges remaining on their bodies although looking at first like other albino creatures, thus creating the misconception that the reptiles are albino themselves when they are not. Four such alligators are kept at the Gatorland theme park in the U.S. state of Florida. In Australia, a crocodile believed to be "part-albino" and nicknamed by people in the area as "Michael Jackson", attacked and killed a man.


title: Albinism

text: In snakes, partial absence of pigment is more common than absolute albinism. For snakes that are usually patterned in colours, they appear as a faint blue, peach or yellowish. In these cases, there has been a genetic mutation in the melanin and pigment delivery. The appearance comes from the inability for full colours to be present, such as black, red, brown and others. The eyes of an albino snake are typically red or pink. Albino snakes can remain in the sunlight for several hours with minimal harm. Corn snakes and snakes of larger types, such as a boa or diamondback snakes, are the most commonly affected by albinism often appearing to be a pinkish or yellowish colour.


title: Albinism

text: Albino tortoises and turtles are uncommon; Sulcata tortoises are the most likely type of turtle to express albinism. The shells have an almost yellow colouration and they have pink eyes. For turtles, a pure white colour is nearly impossible, even with albinism. Albino turtles can have a longer lifespan than many other albino animals; their hard shells help to prevent predation and other environmental challenges. Vision and sensory organs are slightly affected.


title: Albinism

text: In 2012, an albino anole was reported and photographed. In 2007, it was reported that an albino stumpy-tail lizard (possibly a shingleback lizard), approximately long and roughly 1 year old, had been found in Victoria, Australia.


title: Albinism

text: There are three known "albino" strains of leopard gecko, however, breeders state that albinos are generally recognized by their lack of black pigment and having red eyes is not a requirement to be considered an albino. These three strains are called "tremper albinos", "rainwater albinos" and "bell albinos".


title: Albinism

text: As with reptiles, many amphibians labeled as albino are, in fact, not completely lacking in all colour pigments. They are actually amelanistic, not albino. Amphibians have six types of chromatophore in their skin, i.e. melanophores, xanthophores, erythrophores, leucophores, cyanophores and iridophores. An amelanistic amphibian therefore, may still have various pigmentation.


title: Albinism

text: The incidence of albinism in frogs, salamanders, and newts is relatively higher than other taxa. It has been estimated that one in four hundred of these animals is albino. When albino tadpoles hatch, they are almost transparent. This may help camouflage them initially, however, after two weeks, when their hindlegs begin to emerge, they become milky white. A survey in 2001 found hundreds of tiny albino plains leopard frogs, but when the researcher returned a few months later, not a single albino adult could be found.


title: Albinism

text: In European Salamandridae, albinism has been recorded in the fire salamander ("Salamandra salamandra"), gold-striped salamander ("Chioglossa lusitanica"), Italian crested newt ("Triturus carnifex"), marbled newt ("Triturus marmoratus"), Iberian ribbed newt ("Pleurodeles waltl"), alpine newt ("Ichthyosaura alpestris") and two sub-species of the smooth newt ("Lissotriton vulgaris vulgaris" and "Lissotriton vulgaris meridionalis").


title: Albinism

text: Genetic studies of albinism in amphibians have focused on mutations in the tyrosinase gene. The albino phenotype of the leopard frog ("Rana pipiens") has been attributed to a failure in post-translational control in a single recessive tyrosinase gene which still has some tyrosinase and DOPA oxidase activity. This is in contrast with mammals, some of which have mutations that show no tyrosinase or DOPA oxidase activity in albinos. The albino phenotype of the pond frog ("Pelophylax nigromaculatus") has been attributed to one of three mutations that created a dysfunctional tyrosinase. Two of those mutations involve an insertion of a thymine (T), a frameshift mutation, resulting in a truncated isoform of the TYR protein that is defective. The other mutation involves the deletion of a codon, three nucleotides that code for a lysine (Lys). In the wrinkled frog ("Glandirana rugosa") and in the rice frog ("Fejervarya kawamurai"), a substitution from a guanine (G) to an adenine (A) creates a missense mutation, in which a glycine (Gly) changes to an aspartic acid (Asp) and an arginine (Arg), respectively. These changes in the polypeptide chain causes a dysfunctional tyrosinase.


title: Albinism

text: Albinism in molluscs has been recognized to be a hereditary phenomenon at least since 1900. Albinism in molluscs can exist to a variable degree. Sometimes an individual snail has a normally pigmented body, but the shell is completely without the normal pigmentation because of a defect in the cells of the mantle. Shells of certain mollusc species can be translucent when they lack the normal pigmentation.


title: Albinism

text: The neurohormone [His7]-corazonin induces darkening of the cuticle of "Locusta migratoria". The Okinawa strain of this species is deficient in [His7]-corazonin and is albino. One of the typical features of "Locusta migratoria" is that they are gregarious locusts. However, the albino strain shows more solitarious behaviour.


title: Albinism

text: The "yellow" mutation in fruit flies is a mutation causing a congenital lack of normal pigment; it is a similar phenomenon to albinism in other organisms.


title: Albinism

text: The Japanese sea cucumber ("Apostichopus japonicus") is an echinoderm that is caught in the wild or cultivated for food.


title: Albinism

text: Normal Japanese sea cucumbers start to develop pigmentation when they are about 1 cm long. The upperside becomes a dull, yellowish -brown to maroon and the underside a light brown. The body walls of adult, albino Japanese sea cucumbers contain only 0.24% melanin compared to 3.12% in normal adults. The difference in melanin content becomes visually apparent at 60 days of age. The epidermis is thinner in the albinos and contains fewer melanocytes. Albino individuals are similar to normal individuals in growth rate, digestion rate and fertility.


title: Albinism

text: Astaxanthin is the main carotenoid in marine crustaceans (and fish). It has been shown that adding astaxanthin to the feed can improve the skin and muscle colour of marine organisms and thereby increase their commercial and ornamental value.


title: Albinism

text: "Albino" individuals of normally red citrus red mites ("Panonychus citri") occasionally appear in laboratory colonies, however, these still contain green and yellow pigments. This albinism does not affect mortality.


title: Albinism

text: In some animals, albinism-like conditions may affect other pigments or pigment-production mechanisms:


title: Albinism

text: In plants, albinism is characterised by partial or complete loss of chlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes with photosynthesis, which can reduce survivability. Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".


title: Albinism

text: Albino redwoods are rare examples of an albino tree with white needles; despite its lack of chlorophyll it may grow to substantial size as a parasite, usually on the base of the (normal) redwood tree from which it first grew. Only about sixty examples of albino redwoods are known. Additionally, an even smaller number of "chimeric" redwood trees have both normal and white needles.


title: Albinism

text: Albinism has frequently occurred in progeny of Black Tartarian, Bing and Hedelfingen varieties of sweet cherry.


title: Albinism

text: Some herbicides (e.g. glyphosate and triazines) can cause partial chlorosis in plants, even several seasons or years after applicating.


title: Albinism

text: The Albino Squirrel Preservation Society was founded at the University of Texas at Austin in 2001. Members of the society at the University of North Texas petitioned for an election to name their albino squirrel as the university's secondary mascot. The University of Louisville in Kentucky also has a documented population of albino squirrels.


title: Hysteria

text: Hysteria is a term used colloquially to mean ungovernable emotional excess and can refer to a temporary state of mind or emotion. In the nineteenth century, hysteria was considered a diagnosable physical illness in women. It is assumed that the basis for diagnosis operated under the belief that women are predisposed to mental and behavioral conditions; an interpretation of sex-related differences in stress responses. In the twentieth century, it shifted to being considered a mental illness. Many influential people such as Sigmund Freud and Jean-Martin Charcot dedicated research to hysteria patients.


title: Hysteria

text: Currently, most doctors practicing medicine do not accept hysteria as a medical diagnosis. The blanket diagnosis of hysteria has been fragmented into myriad medical categories such as epilepsy, histrionic personality disorder, conversion disorders, dissociative disorders, or other medical conditions. Furthermore, lifestyle choices, such as choosing not to wed, are no longer considered symptoms of psychological disorders such as hysteria.


title: Hysteria

text: The word hysteria originates from the Greek word for uterus, "hystera". The oldest record of hysteria dates back to 1900 BCE when Egyptians recorded behavioral abnormalities in adult women on the Kahun Papyrus. The Egyptians attributed the behavioral disturbances to a wandering uterusthus later dubbing the condition hysteria. To treat hysteria Egyptian doctors prescribed various medications. For example, doctors put strong smelling substances on the patients' vulvas to encourage the uterus to return to its proper position. Another tactic was to smell or swallow unsavory herbs to encourage the uterus to flee back to the lower part of the female's abdomen.


title: Hysteria

text: The ancient Greeks accepted the ancient Egyptians' explanation for hysteria; however, they included in their definition of hysteria the inability to bear children or the unwillingness to marry. Plato and Aristotle believed that hysteria, which Plato also called female madness, was directly related to these women’s lack of sexual activity and described the uterus as those who suffered from it as having a sad, bad, or melancholic uterus. In the 5th century BCE Hippocrates first used the term hysteria. Ancient Romans also attributed hysteria to an abnormality in the womb; however, discarded the traditional explanation of a wandering uterus. Instead, the ancient Romans credited hysteria to a disease of the womb or a disruption in reproduction (i.e., a miscarriage, menopause, etc.). Hysteria theories from the ancient Egyptians, ancient Greeks, and ancient Romans were the basis of the Western understanding of hysteria.


title: Hysteria

text: Between the fifth and thirteenth centuries, however, the increasing influence of Christianity in the Latin West altered medical and public understanding of hysteria. St. Augustine's writings suggested that human suffering resulted from sin, thus hysteria became perceived as satanic possession. With the shift in perception of hysteria came a shift in treatment options. Instead of admitting patients to a hospital, the church began treating patients through prayers, amulets, and exorcisms. At this time, writings such as Constantine the African’s "Viaticum" and "Pantegni", described women with hysteria as the cause of amor heroycus, a form of sexual desire so strong that it caused madness, rather than someone with a problem who should be cured.


title: Hysteria

text: Trota de Ruggiero is considered the first female doctor in Christian Europe as well as the first gynecologist, though she could not become a magister. She recognized that women were often ashamed to go to a doctor with gynecological issues, and studied women’s diseases and attempted to avoid common misconceptions and prejudice of the era. She prescribed remedies such as mint for women suffering from hysteria. Hildegard of Bingen was another female doctor, whose work was part of an attempt to combine science and faith. She agreed with the theories of Hippocrates and suggested hysteria may be connected to the idea of original sin; She believed that men and women were both responsible for original sin, and could both suffer from hysteria. Furthermore, during the Renaissance period many patients of hysteria were prosecuted as witches and underwent interrogations, torture, exorcisms, and execution. During this time the common point of view was that women were inferior beings, connected to Aristotle’s ideas of male superiority. Saint Thomas Aquinas supported this idea and in his writing Summa Theologica stated “'some old women' are evil-minded; they gaze on children in a poisonous and evil way, and demons, with whom the witches enter into agreements, interacting through their eyes”. This time of fear of witches and sorcery is part of the rules of celibacy and chastity imposed on the clergy. Philippe Pinel believed that there was little difference between madness and healthy people, and believed that people should be treated if they were unwell. He considered hysteria a female disorder.


title: Hysteria

text: However, during the sixteenth and seventeenth centuries activists and scholars worked to change the perception of hysteria back to a medical condition. Particularly, French physician insisted that hysteria was a malady of the brain. In addition, in 1697, English physician Thomas Sydenham theorized that hysteria was an emotional condition, instead of a physical condition. Many physicians followed Lepois and Sydenham's lead and hysteria became disassociated with the soul and the womb. During this time period, science started to focalize hysteria in the central nervous system. As doctors developed a greater understanding of the human nervous system, the neurological model of hysteria was created, which further propelled the conception of hysteria as a mental disorder. Joseph Raulin published a work in 1748, associating hysteria with the air quality in cities, he suggested that men and women could both have hysteria, women would be more likely to have it due to laziness.


title: Hysteria

text: In 1859 Paul Briquet defined hysteria as a chronic syndrome manifesting in many unexplained symptoms throughout the body's organ systems. What Briquet described became known as Briquet's syndrome, or Somatization disorders, in 1971. Over a ten-year period, Briquet conducted 430 case studies of patients with hysteria. Following Briquet, Jean-Martin Charcot studied women in an asylum in France and used hypnosis as treatment. Charcot detailed the intricacies of hysteria, understanding it as being caused by patriarchy. He also mentored Pierre Janet, another French psychologist, who studied five of hysteria's symptoms (anesthesia, amnesia, abulia, motor control diseases, and character change) in depth and proposed that hysteria symptoms occurred due to a lapse in consciousness. Both Charcot and Janet inspired Freud's work. Freud theorized hysteria stemmed from childhood sexual abuse or repression, he and Charcot were among the first to apply hysteria to men, however he also believed that a side benefit of hysteria was an ability to manipulate those around the patient, specifically women who became skilled at handling those around her.


title: Hysteria

text: During the twentieth century, as psychiatry advanced in the West, anxiety and depression diagnoses began to replace hysteria diagnoses in Western countries. For example, from 1949 to 1978, annual admissions of hysteria patients in England and Wales decreased by roughly two thirds. With the decrease of hysteria patients in Western cultures came an increase in anxiety and depression patients. Theories for why hysteria diagnoses began to decline vary, but many historians infer that World WarII, along with the use of the diagnosis of shell-shock, westernization, and migration shifted Western mental health expectations. Twentieth-century western societies expected depression and anxiety manifest itself more in post World War II generations and displaced individuals; and thus, individuals reported or were diagnosed accordingly. In addition, medical advancements explained ailments that were previously attributed to hysteria such as epilepsy or infertility. World Wars caused military doctors to become focused on hysteria as during this time there seemed to be a rise in cases, especially under instances of high stress, in 1919 Arthur Frederick Hurst wrote that “many cases of gross hysterical symptoms occurred in soldiers who had no family or personal history of neuroses, and who were perfectly fit”. In 1970 Colin P. McEvedy and Alanson W. Beard suggested that Royal Free Disease (Royal Free Hospital outbreak, now also known as chronic fatigue), which mainly affected young women, was an epidemic of hysteria. They also said that hysteria had a historically negative connotation, however that should not prevent doctors from assessing symptoms of the patient. In 1980, after a gradual decline in diagnoses and reports, hysteria was removed from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM), which had included hysteria as a mental disorder from its second publication in 1968.


title: Hysteria

text: The term is still used in the twenty-first century, though not as a diagnosis. When used, it is often in social media to demean those who speak out against systematic violence such as misogyny or xenophobia, and suggest the person referred to is over-emotional, not stable, or having an unrealistic view of reality. It often implied the person can not be taken seriously.


title: Hysteria

text: In the late nineteenth century French neurologist Jean-Martin Charcot tackled what he referred to as "the great neurosis" or hysteria. Charcot theorized that hysteria was a hereditary, physiological disorder. He believed hysteria impaired areas of the brain which provoked the physical symptoms displayed in each patient. While Charcot believed hysteria was hereditary, he also thought that environmental factors such as stress could trigger hysteria in an individual.


title: Hysteria

text: Charcot published more than 120 case studies of patients who he diagnosed with hysteria, including Marie "Blanche" Whittman. Whittman was referred to as the "Queen of Hysterics," and remains the most famous patient of hysteria. To treat his patients, Charcot used hypnosis, which he determined was successful only when used on hysterics. Using patients as props, Charcot executed dramatic public demonstrations of hysterical patients and his cures for hysteria, which many suggest produced the hysterical phenomenon. Furthermore, Charcot noted similarities between demon possession and hysteria, and thus, he concluded "demonomania" was a form of hysteria.


title: Hysteria

text: In 1896 Sigmund Freud, an Austrian neurologist, published "The Aetiology of Hysteria". The paper explains how Freud believes his female patients' neurosis, which he labels hysteria, resulted from sexual abuse as children. Freud named the concept of physical symptoms resulting from childhood trauma: hysterical conversion. Freud hypothesized that in order to cure hysteria the patient must relive the experiences through imagination in the most vivid form while under light hypnosis. However, Freud later changed his theory. His new theory claimed that his patients imagined the instances of sexual abuse, which were instead repressed childhood fantasies. By 1905, Freud retracted the theory of hysteria resulting from repressed childhood fantasies. Freud was also one of the first noted psychiatrist to attribute hysteria to men. He diagnosed himself with hysteria, writing that he feared his work had exacerbated his condition.


title: Hysteria

text: For the most part, hysteria does not exist as a medical diagnosis in Western culture and has been replaced by other diagnoses such as conversion or functional disorders. The effects of hysteria as a diagnosable illness in the eighteenth and nineteenth centuries has had a lasting effect on the medical treatment of women's health. The term "hysterical", applied to an individual, can mean that they are emotional, irrationally upset, or frenzied. When applied to a situation not involving panic, hysteria means that that situation is uncontrollably amusingthe connotation being that it invokes hysterical laughter.


title: Hysteria

text: According to Laura Briggs’s "The Race of Hysteria: “Overcivilization” and the “Savage” Woman in Late Nineteenth-Century Obstetrics and Gynecology," women could be categorized into three steps of civilization: the savage, the civilized, and the overcivilized. Referencing Edward Tylor’s conception that humans evolve through three stages: savage, barbarian, and civilized. Briggs believes that Hysteria was thought to be caused by overcivilization. Terms such as “savage” were reserved for people in extreme poverty or of minority descent (Africans, Asians, Indigenous, Jewish, etc). Because of this distinction between the civilized and the savage during the 19th Century, Hysteria was diagnosed as a disease among mostly middle and upper-class white women.


title: Hysteria

text: Many middle and upper-class white men, identified middle and upper-class white women as endangering the race with their low fertility, while non-white women, immigrants, and poor people had many children. During the 19th Century, white women were categorized as “weak, frail and nervous” which reflected the diagnosed symptoms for hysteria such as nervousness, fainting, and ill reproductive bodies. On the contrary, minority and impoverished women were seen as “strong, hardy, and prolifically fertile.” This caused worry among white men who feared that middle and upper-class white women were causing the depopulation of their race. This growing conception would later be coined, “race suicide” by Edward A. Ross.


title: Hysteria

text: As race suicide became a more recognizable fear in Europe and the U.S., many people attempted to solve it by targeting white women's nutrition, overeducation, sexual limbo, and physical health. Additionally, press and Nativist parties ushered a national concern by connecting the reproduction of white women to the reproduction of first and second generation immigrant woman.  “[Race suicide] pitted white women against the more-fecund women of supposedly ‘‘inferior’’ races supports interpretations of race suicide in terms of anti-immigrant sentiment.” As the white public became more unsettled by increased immigration and the declining birthrates of white children, white women were blamed if they lacked the “American ideal” of 4-6 children. Additionally, Immigrants from all minorities were the target of xenophobic remarks and eventually forced sterilization in the U.S. due to eugenics legislation.


title: Many-worlds interpretation

text: The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse. This implies that all possible outcomes of quantum measurements are physically realized in some "world" or universe. In contrast to some other interpretations, such as the Copenhagen interpretation, the evolution of reality as a whole in MWI is rigidly deterministic and local. Many-worlds is also called the relative state formulation or the Everett interpretation, after physicist Hugh Everett, who first proposed it in 1957. Bryce DeWitt popularized the formulation and named it "many-worlds" in the 1970s.


title: Many-worlds interpretation

text: In many-worlds, the subjective appearance of wavefunction collapse is explained by the mechanism of quantum decoherence. Decoherence approaches to interpreting quantum theory have been widely explored and developed since the 1970s, and have become quite popular. MWI is now considered a mainstream interpretation along with the other decoherence interpretations, collapse theories (including the Copenhagen interpretation), and hidden variable theories such as Bohmian mechanics.


title: Many-worlds interpretation

text: The many-worlds interpretation implies that there are most likely an uncountably infinite number of universes. It is one of a number of multiverse hypotheses in physics and philosophy. MWI views time as a many-branched tree, wherein every possible quantum outcome is realised. This is intended to resolve the measurement problem and thus some paradoxes of quantum theory, such as the EPR paradox and Schrödinger's cat, since every possible outcome of a quantum event exists in its own universe.


title: Many-worlds interpretation

text: The key idea of the many-worlds interpretation is that the unitary dynamics of quantum mechanics applies everywhere and at all times and so describes the whole universe. In particular, it models a measurement as a unitary transformation, a correlation-inducing interaction, between observer and object, without using a collapse postulate, and models observers as ordinary quantum-mechanical systems. This stands in sharp contrast to the Copenhagen interpretation, in which a measurement is a "primitive" concept, not describable by unitary quantum mechanics; in Copenhagen the universe is divided into a quantum and a classical domain, and the collapse postulate is central. MWI's main conclusion is that the universe (or multiverse in this context) is composed of a quantum superposition of an infinite or undefinable amount or number of increasingly divergent, non-communicating parallel universes or quantum worlds. Sometimes dubbed Everett worlds, each is a consistent and actualized alternative history or timeline.


title: Many-worlds interpretation

text: The many-worlds interpretation makes use of decoherence to explain the measurement process and the emergence of a quasi-classical world. Wojciech H. Zurek, one of decoherence theory's pioneers, stated: "Under scrutiny of the environment, only pointer states remain unchanged. Other states decohere into mixtures of stable pointer states that can persist, and, in this sense, exist: They are einselected." Zurek emphasizes that his work does not depend on a particular interpretation.


title: Many-worlds interpretation

text: The many-worlds interpretation shares many similarities with the decoherent histories interpretation, which also uses decoherence to explain the process of measurement or wavefunction collapse. MWI treats the other histories or worlds as real, since it regards the universal wavefunction as the "basic physical entity" or "the fundamental entity, obeying at all times a deterministic wave equation". Decoherent histories, on the other hand, needs only one of the histories (or worlds) to be real.


title: Many-worlds interpretation

text: Several authors, including Wheeler, Everett and Deutsch, call many-worlds a theory or metatheory, rather than just an interpretation. Everett argued that it was the "only completely coherent approach to explaining both the contents of quantum mechanics and the appearance of the world." Deutsch dismissed the idea that many-worlds is an "interpretation", saying that to call it an interpretation "is like talking about dinosaurs as an 'interpretation' of fossil records."


title: Many-worlds interpretation

text: In his 1957 doctoral dissertation, Everett proposed that, rather than relying on external observation for analysis of isolated quantum systems, one could mathematically model an object, as well as its observers, as purely physical systems within the mathematical framework developed by Paul Dirac, John von Neumann and others, discarding altogether the "ad hoc" mechanism of wave function collapse.


title: Many-worlds interpretation

text: Everett's original work introduced the concept of a relative state. Two (or more) subsystems, after a general interaction, become entangled. Everett noted that such entangled systems can be expressed as the sum of products of states, where the two or more subsystems are each in a state relative to each other. After a measurement or observation one of the pair (or triple...) is the measured, object or observed system, and one other member is the measuring apparatus (which may include an observer) having recorded the state of the measured system.


title: Many-worlds interpretation

text: In the example of Schrödinger's cat, after the box is opened, the entangled system is the cat, the poison vial and the observer. "One" relative triple of states would be the alive cat, the unbroken vial and the observer seeing an alive cat. "Another" relative triple of states would be the dead cat, the broken vial and the observer seeing a dead cat.


title: Many-worlds interpretation

text: The process of measurement or observation, or any correlation-inducing interaction, splits the system up into sets of relative states, where each set of relative states, forming a branch of the universal wavefunction, is consistent within itself, and all future measurements (including by multiple observers) will confirm this consistency.


title: Many-worlds interpretation

text: The many-worlds interpretation is DeWitt's popularisation of Everett, who had referred to the combined observer–object system as split by an observation, each split corresponding to the different or multiple possible outcomes of an observation. These splits generate a branching tree, where each branch is a set of all the states relative to each other. DeWitt introduced the term "world" to describe a single branch of that tree, which is a consistent history. All observations or measurements in any branch are consistent with each other.


title: Many-worlds interpretation

text: Under the many-worlds interpretation, the Schrödinger equation, or its quantum field theory, relativistic analog, holds all the time, everywhere. An observation or measurement is modelled by applying the wave equation to the entire system, comprising the observer "and" the object being observed. One consequence is that every observation can be thought of as causing the combined observer–object's wavefunction to change into a quantum superposition of two or more non-interacting branches, or split into many "worlds". Since many observation-like events have happened and are constantly happening, there are an enormous and growing number of simultaneously existing states.


title: Many-worlds interpretation

text: If a system is composed of two or more subsystems, the system's state will be a superposition of products of the subsystems' states. Each product of subsystem states in the overall superposition evolves over time independently of other products. Once the subsystems interact, their states have become correlated or entangled and can no longer be considered independent. In Everett's terminology, each subsystem state was now "correlated" with its "relative state", since each subsystem must now be considered relative to the other subsystems with which it has interacted.


title: Many-worlds interpretation

text: MWI removes the observer-dependent role in the quantum measurement process by replacing wavefunction collapse with quantum decoherence. Since the observer's role lies at the heart of most if not all "quantum paradoxes", this automatically resolves a number of problems, such as Schrödinger's cat thought experiment, the EPR paradox, von Neumann's "boundary problem", and others.


title: Many-worlds interpretation

text: Since the Copenhagen interpretation requires the existence of a classical domain beyond the one described by quantum mechanics, it has been criticized as inadequate for the study of cosmology. MWI was developed with the explicit goal of allowing quantum mechanics to be applied to the universe as a whole, making quantum cosmology possible.


title: Many-worlds interpretation

text: MWI is a realist, deterministic and local theory. It achieves this by removing wave function collapse, which is indeterministic and nonlocal, from the deterministic and local equations of quantum theory.


title: Many-worlds interpretation

text: MWI (like other, broader multiverse theories) provides a context for the anthropic principle, which may provide an explanation for the fine-tuned universe.


title: Many-worlds interpretation

text: MWI depends crucially on the linearity of quantum mechanics, which underpins the superposition principle. If the final theory of everything is non-linear with respect to wavefunctions, then many-worlds is invalid. All quantum field theories are linear and compatible with the MWI, a point emphasised by Everett as a motivation for the MWI. While quantum gravity or string theory may be non-linear in this respect, there is as yet no evidence of this.


title: Many-worlds interpretation

text: As with the other interpretations of quantum mechanics, the many-worlds interpretation is motivated by behavior that can be illustrated by the double-slit experiment. When particles of light (or anything else) pass through the double slit, a calculation assuming wavelike behavior of light can be used to identify where the particles are likely to be observed. Yet when the particles are observed in this experiment, they appear as particles (i.e., at definite places) and not as non-localized waves.


title: Many-worlds interpretation

text: Some versions of the Copenhagen interpretation of quantum mechanics proposed a process of "collapse" in which an indeterminate quantum system would probabilistically collapse down onto, or select, just one determinate outcome to "explain" this phenomenon of observation. Wavefunction collapse was widely regarded as artificial and "ad hoc", so an alternative interpretation in which the behavior of measurement could be understood from more fundamental physical principles was considered desirable.


title: Many-worlds interpretation

text: Everett's PhD work provided such an interpretation. He argued that for a composite system—such as a subject (the "observer" or measuring apparatus) observing an object (the "observed" system, such as a particle)—the claim that either the observer or the observed has a well-defined state is meaningless; in modern parlance, the observer and the observed have become entangled: we can only specify the state of one "relative" to the other, i.e., the state of the observer and the observed are correlated "after" the observation is made. This led Everett to derive from the unitary, deterministic dynamics alone (i.e., without assuming wavefunction collapse) the notion of a "relativity of states".


title: Many-worlds interpretation

text: Everett noticed that the unitary, deterministic dynamics alone entailed that after an observation is made each element of the quantum superposition of the combined subject–object wavefunction contains two "relative states": a "collapsed" object state and an associated observer who has observed the same collapsed outcome; what the observer sees and the state of the object have become correlated by the act of measurement or observation. The subsequent evolution of each pair of relative subject–object states proceeds with complete indifference as to the presence or absence of the other elements, "as if" wavefunction collapse has occurred, which has the consequence that later observations are always consistent with the earlier observations. Thus the "appearance" of the object's wavefunction's collapse has emerged from the unitary, deterministic theory itself. (This answered Einstein's early criticism of quantum theory, that the theory should define what is observed, not for the observables to define the theory.) Since the wavefunction merely appears to have collapsed then, Everett reasoned, there was no need to actually assume that it had collapsed. And so, invoking Occam's razor, he removed the postulate of wavefunction collapse from the theory.


title: Many-worlds interpretation

text: In 1985, David Deutsch proposed a variant of the Wigner's friend thought experiment as a test of many-worlds versus the Copenhagen interpretation. It consists of an experimenter (Wigner's friend) making a measurement on a quantum system in an isolated laboratory, and another experimenter (Wigner) who would make a measurement on the first one. According to the many-worlds theory, the first experimenter would end up in a macroscopic superposition of seeing one result of the measurement in one branch, and another result in another branch. The second experimenter could then interfere these two branches in order to test whether it is in fact in a macroscopic superposition or has collapsed into a single branch, as predicted by the Copenhagen interpretation. Since then Lockwood (1989), Vaidman and others have made similar proposals. These proposals require placing macroscopic objects in a coherent superposition and interfering them, a task currently beyond experimental capability.


title: Many-worlds interpretation

text: Since the many-worlds interpretation's inception, physicists have been puzzled about the role of probability in it. As put by Wallace, there are two facets to the question: the "incoherence problem", which asks why we should assign probabilities at all to outcomes that are certain to occur in some worlds, and the "quantitative problem", which asks why the probabilities should be given by the Born rule.


title: Many-worlds interpretation

text: Everett tried to answer these questions in the paper that introduced many-worlds. To address the incoherence problem, he argued that an observer who makes a sequence of measurements on a quantum system will in general have an apparently random sequence of results in their memory, which justifies the use of probabilities to describe the measurement process. To address the quantitative problem, Everett proposed a derivation of the Born rule based on the properties that a measure on the branches of the wavefunction should have. His derivation has been criticized as relying on unmotivated assumptions. Since then several other derivations of the Born rule in the many-worlds framework have been proposed. There is no consensus on whether this has been successful.


title: Many-worlds interpretation

text: DeWitt and Graham and Farhi et al., among others, have proposed derivations of the Born rule based on a frequentist interpretation of probability. They try to show that in the limit of infinitely many measurements no worlds would have relative frequencies that didn't match the probabilities given by the Born rule, but these derivations have been shown to be mathematically incorrect.


title: Many-worlds interpretation

text: A decision-theoretic derivation of the Born rule was produced by David Deutsch (1999) and refined by Wallace (2002–2009) and Saunders (2004). They consider an agent who takes part in a quantum gamble: the agent makes a measurement on a quantum system, branches as a consequence, and each of the agent's future selves receives a reward that depends on the measurement result. The agent uses decision theory to evaluate the price they would pay to take part in such a gamble, and concludes that the price is given by the utility of the rewards weighted according to the Born rule. Some reviews have been positive, although these arguments remain highly controversial; some theoretical physicists have taken them as supporting the case for parallel universes. For example, a "New Scientist" story on a 2007 conference about Everettian interpretations quoted physicist Andy Albrecht as saying, "This work will go down as one of the most important developments in the history of science." In contrast, the philosopher Huw Price, also attending the conference, found the Deutsch–Wallace–Saunders approach fundamentally flawed.


title: Many-worlds interpretation

text: Zurek (2005) has produced a derivation of the Born rule based on the symmetries of entangled states; Schlosshauer and Fine argue that Zurek's derivation is not rigorous, as it does not define what probability is and has several unstated assumptions about how it should behave.


title: Many-worlds interpretation

text: Charles Sebens and Sean M. Carroll, building on work by Lev Vaidman, proposed a similar approach based on self-locating uncertainty. In this approach, decoherence creates multiple identical copies of observers, who can assign credences to being on different branches using the Born rule. The Sebens–Carroll approach has been criticized by Adrian Kent, and Vaidman himself does not find it satisfactory.


title: Many-worlds interpretation

text: As originally formulated by Everett and DeWitt, the many-worlds interpretation had a privileged role for measurements: they determined which basis of a quantum system would give rise to the eponymous worlds. Without this the theory was ambiguous, as a quantum state can equally well be described (e.g.) as having a well-defined position or as being a superposition of two delocalised states. The assumption is that the preferred basis to use is the one which assigns a unique measurement outcome to each world. This special role for measurements is problematic for the theory, as it contradicts Everett and DeWitt's goal of having a reductionist theory and undermines their criticism of the ill-defined measurement postulate of the Copenhagen interpretation. This is known today as the "preferred basis problem".


title: Many-worlds interpretation

text: The preferred basis problem has been solved, according to Saunders and Wallace, among others, by incorporating decoherence into the many-worlds theory. In this approach, the preferred basis does not have to be postulated, but rather is identified as the basis stable under environmental decoherence. In this way measurements no longer play a special role; rather, any interaction that causes decoherence causes the world to split. Since decoherence is never complete, there will always remain some infinitesimal overlap between two worlds, making it arbitrary whether a pair of worlds has split or not. Wallace argues that this is not problematic: it only shows that worlds are not a part of the fundamental ontology, but rather of the "emergent" ontology, where these approximate, effective descriptions are routine in the physical sciences. Since in this approach the worlds are derived, it follows that they must be present in any other interpretation of quantum mechanics that does not have a collapse mechanism, such as Bohmian mechanics.


title: Many-worlds interpretation

text: This approach to deriving the preferred basis has been criticized as creating a circularity with derivations of probability in the many-worlds interpretation, as decoherence theory depends on probability, and probability depends on the ontology derived from decoherence. Wallace contends that decoherence theory depends not on probability but only on the notion that one is allowed to do approximations in physics.


title: Many-worlds interpretation

text: MWI originated in Everett's Princeton PhD thesis "The Theory of the Universal Wavefunction", developed under his thesis advisor John Archibald Wheeler, a shorter summary of which was published in 1957 under the title "Relative State Formulation of Quantum Mechanics" (Wheeler contributed the title "relative state"; Everett originally called his approach the "Correlation Interpretation", where "correlation" refers to quantum entanglement). The phrase "many-worlds" is due to Bryce DeWitt, who was responsible for the wider popularisation of Everett's theory, which had been largely ignored for a decade after publication in 1957.


title: Many-worlds interpretation

text: Everett's proposal was not without precedent. In 1952, Erwin Schrödinger gave a lecture in Dublin in which at one point he jocularly warned his audience that what he was about to say might "seem lunatic". He went on to assert that while the Schrödinger equation seemed to be describing several different histories, they were "not alternatives but all really happen simultaneously". According to David Deutsch, this is the earliest known reference to many-worlds; Jeffrey A. Barrett describes it as indicating the similarity of "general views" between Everett and Schrödinger. Schrödinger's writings from the period also contain elements resembling the modal interpretation originated by Bas van Fraassen. Because Schrödinger subscribed to a kind of post-Machian neutral monism, in which "matter" and "mind" are only different aspects or arrangements of the same common elements, treating the wavefunction as physical and treating it as information became interchangeable.


title: Many-worlds interpretation

text: MWI's initial reception was overwhelmingly negative, in the sense that it was ignored, with the notable exception of DeWitt. Wheeler made considerable efforts to formulate the theory in a way that would be palatable to Bohr, visited Copenhagen in 1956 to discuss it with him, and convinced Everett to visit as well, which happened in 1959. Nevertheless, Bohr and his collaborators completely rejected the theory. Everett had already left academia in 1956, never to return, and after his death, Wheeler disavowed the theory.


title: Many-worlds interpretation

text: One of MWI's strongest longtime advocates is David Deutsch. According to Deutsch, the single photon interference pattern observed in the double slit experiment can be explained by interference of photons in multiple universes. Viewed this way, the single photon interference experiment is indistinguishable from the multiple photon interference experiment. In a more practical vein, in one of the earliest papers on quantum computing, he suggested that parallelism that results from MWI could lead to ""a method by which certain probabilistic tasks can be performed faster by a universal quantum computer than by any classical restriction of it"". Deutsch has also proposed that MWI will be testable (at least against "naive" Copenhagenism) when reversible computers become conscious via the reversible observation of spin.


title: Many-worlds interpretation

text: Philosophers of science James Ladyman and Don Ross say that the MWI could be true, but that they do not embrace it. They note that no quantum theory is yet empirically adequate for describing all of reality, given its lack of unification with general relativity, and so they do not see a reason to regard any interpretation of quantum mechanics as the final word in metaphysics. They also suggest that the multiple branches may be an artifact of incomplete descriptions and of using quantum mechanics to represent the states of macroscopic objects. They argue that macroscopic objects are significantly different from microscopic objects in not being isolated from the environment, and that using quantum formalism to describe them lacks explanatory and descriptive power and accuracy.


title: Many-worlds interpretation

text: Victor J. Stenger remarked that Murray Gell-Mann's published work explicitly rejects the existence of simultaneous parallel universes. Collaborating with James Hartle, Gell-Mann worked toward the development a more "palatable" "post-Everett quantum mechanics". Stenger thought it fair to say that most physicists find the MWI too extreme, while noting it "has merit in finding a place for the observer inside the system being analyzed and doing away with the troublesome notion of wave function collapse".


title: Many-worlds interpretation

text: Richard Feynman, described as an Everettian in some sources, said of the MWI in 1982, "It's possible, but I'm not very happy with it."


title: Many-worlds interpretation

text: Some scientists consider MWI unfalsifiable and hence unscientific because the multiple parallel universes are non-communicating, in the sense that no information can be passed between them. Others claim MWI is directly testable.


title: Many-worlds interpretation

text: Roger Penrose argues that the idea is flawed because it is based on an oversimple version of quantum mechanics that does not account for gravity. In his view, applying conventional quantum mechanics to the universe implies the MWI, but the lack of a successful theory of quantum gravity negates the claimed universality of conventional quantum mechanics. According to Penrose, "the rules must change when gravity is involved". He further asserts that gravity helps anchor reality and "blurry" events have only one allowable outcome: "electrons, atoms, molecules, etc., are so minute that they require almost no amount of energy to maintain their gravity, and therefore their overlapping states. They can stay in that state forever, as described in standard quantum theory". On the other hand, "in the case of large objects, the duplicate states disappear in an instant due to the fact that these objects create a large gravitational field".


title: Many-worlds interpretation

text: Philosopher of science Robert P. Crease says that the MWI is "one of the most implausible and unrealistic ideas in the history of science" because it means that everything conceivable happens. Science writer Philip Ball describes the MWI's implications as fantasies, since "beneath their apparel of scientific equations or symbolic logic, they are acts of imagination, of 'just supposing'".


title: Many-worlds interpretation

text: Theoretical physicist Gerard 't Hooft also dismisses the idea: "I do not believe that we have to live with the many-worlds interpretation. Indeed, it would be a stupendous number of parallel worlds, which are only there because physicists couldn't decide which of them is real."


title: Many-worlds interpretation

text: Asher Peres was an outspoken critic of MWI. A section of his 1993 textbook had the title "Everett's interpretation and other bizarre theories". Peres argued that the various many-worlds interpretations merely shift the arbitrariness or vagueness of the collapse postulate to the question of when "worlds" can be regarded as separate, and that no objective criterion for that separation can actually be formulated.


title: Many-worlds interpretation

text: A poll of 72 "leading quantum cosmologists and other quantum field theorists" conducted before 1991 by L. David Raub showed 58% agreement with "Yes, I think MWI is true".


title: Many-worlds interpretation

text: Max Tegmark reports the result of a "highly unscientific" poll taken at a 1997 quantum mechanics workshop. According to Tegmark, "The many worlds interpretation (MWI) scored second, comfortably ahead of the consistent histories and Bohm interpretations."


title: Many-worlds interpretation

text: In response to Sean M. Carroll's statement "As crazy as it sounds, most working physicists buy into the many-worlds theory", Michael Nielsen counters: "at a quantum computing conference at Cambridge in 1998, a many-worlder surveyed the audience of approximately 200 people... Many-worlds did just fine, garnering support on a level comparable to, but somewhat below, Copenhagen and decoherence." But Nielsen notes that it seemed most attendees found it to be a waste of time: Peres "got a huge and sustained round of applause…when he got up at the end of the polling and asked 'And who here believes the laws of physics are decided by a democratic vote?'"


title: Many-worlds interpretation

text: A 2005 poll of fewer than 40 students and researchers taken after a course on the Interpretation of Quantum Mechanics at the Institute for Quantum Computing University of Waterloo found "Many Worlds (and decoherence)" to be the least favored.


title: Many-worlds interpretation

text: A 2011 poll of 33 participants at an Austrian conference found 6 endorsed MWI, 8 "Information-based/information-theoretical", and 14 Copenhagen; the authors remark that MWI received a similar percentage of votes as in Tegmark's 1997 poll.


title: Many-worlds interpretation

text: Everett believed in the literal reality of the other quantum worlds. His son reported that he "never wavered in his belief over his many-worlds theory".


title: Many-worlds interpretation

text: According to Martin Gardner, the "other" worlds of MWI have two different interpretations: real or unreal; he claimed that Stephen Hawking and Steven Weinberg both favour the unreal interpretation. Gardner also claimed that most physicists favour the unreal interpretation, whereas the "realist" view is supported only by MWI experts such as Deutsch and DeWitt. Gardner reports Hawking saying that MWI is "trivially true". In a 1983 interview, Hawking also said he regarded MWI as "self-evidently correct" but was dismissive of questions about the interpretation of quantum mechanics, saying, "When I hear of Schrödinger's cat, I reach for my gun." In the same interview, he also said, "But, look: All that one does, really, is to calculate conditional probabilities—in other words, the probability of A happening, given B. I think that that's all the many-worlds interpretation is. Some people overlay it with a lot of mysticism about the wave function splitting into different parts. But all that you're calculating is conditional probabilities." Elsewhere Hawking contrasted his attitude towards the "reality" of physical theories with that of his colleague Roger Penrose, saying, "He's a Platonist and I'm a positivist. He's worried that Schrödinger's cat is in a quantum state, where it is half alive and half dead. He feels that can't correspond to reality. But that doesn't bother me. I don't demand that a theory correspond to reality because I don't know what it is. Reality is not a quality you can test with litmus paper. All I'm concerned with is that the theory should predict the results of measurements. Quantum theory does this very successfully."


title: Many-worlds interpretation

text: Gell-Mann described himself as a "post-Everett investigator" and wrote, "it is not necessary to become queasy trying to conceive of many 'parallel universes,' all equally real". Instead, he advocated the language of "many histories, all treated alike by the theory except for their different probabilities."


title: Many-worlds interpretation

text: "Quantum suicide" is a thought experiment in quantum mechanics and the philosophy of physics. Purportedly, it can distinguish between the Copenhagen interpretation of quantum mechanics and the many-worlds interpretation by means of a variation of the Schrödinger's cat thought experiment, from the cat's point of view. "Quantum immortality" refers to the subjective experience of surviving quantum suicide.


title: Many-worlds interpretation

text: Most experts believe that the experiment would not work in the real world, because the world with the surviving experimenter has a lower "measure" than the world before the experiment, making it less likely that the experimenter will experience their survival.


title: Many-worlds interpretation

text: DeWitt has stated that "[Everett, Wheeler and Graham] do not in the end exclude any element of the superposition. All the worlds are there, even those in which everything goes wrong and all the statistical laws break down."


title: Many-worlds interpretation

text: Max Tegmark has affirmed that absurd or highly unlikely events are inevitable but rare under MWI. To quote Tegmark, "Things inconsistent with the laws of physics will never happen—everything else will... it's important to keep track of the statistics, since even if everything conceivable happens somewhere, really freak events happen only exponentially rarely."


title: Many-worlds interpretation

text: Ladyman and Ross state that, in general, many of the unrealized possibilities that are discussed in other scientific fields will not have counterparts in other branches, because they are in fact incompatible with the universal wavefunction.


title: Catherine Bach

text: Catherine Bach (born Catherine Bachman; March 1, 1954) is an American actress. She is known for playing Daisy Duke in the television series "The Dukes of Hazzard" and Margo Dutton in "African Skies". In 2012, she joined the cast of the CBS soap opera "The Young and the Restless" as Anita Lawson.


title: Catherine Bach

text: Bach was born in Cleveland, Ohio, the daughter of Norma Jean Kucera (née Verdugo), an acupuncturist, and Bernard P. Bachman, a rancher. Her mother was a daughter of Antonio L. Verdugo, of Bisbee, Arizona, a baker born in Mexico, while her father was of German ancestry. She was raised in Warren, Ohio. Her mother, born into the Verdugo family, claimed to be descended from one of California's earliest landed families.


title: Catherine Bach

text: She spent some of her childhood on a ranch in South Dakota, and she visited her grandparents in Faith, South Dakota. In 1970, Bach graduated from


title: Catherine Bach

text: Stevens High School in Rapid City, South Dakota. She briefly majored in drama at UCLA, where she supplemented her income by making clothes for friends and theater groups.


title: Catherine Bach

text: Bach's professional debut was as one of the children in a production of "The Sound of Music". Bach's first screen appearance was in the Burt Lancaster murder mystery, "The Midnight Man", shot in upstate South Carolina in 1973, in which she played the murdered coed, Natalie Claiburn. Her next role was Melody in the 1974 film "Thunderbolt and Lightfoot".


title: Catherine Bach

text: Bach heard about the audition for "The Dukes of Hazzard" through her husband. When she arrived there, she found the producers were looking for a Dolly Parton-lookalike; despite not looking like what they were searching for, she was hired on the spot. One of the earliest costume ideas from the producers was that she wear a tight white turtleneck, go-go boots and a poodle skirt, but Bach asked if she could bring her own outfit, which was a homemade T-shirt, a pair of cut-off denim shorts and high heels. Bach had concerns about the appropriateness of the cut-off shorts at first, saying she could not wear them in a restaurant scene. When prompted by the producers to visit a restaurant across the street, Bach found the waitresses were wearing "little miniskirts that matched the tablecloths!". She starred on that show, opposite Tom Wopat, John Schneider and James Best.


title: Catherine Bach

text: At the suggestion of the show's producers, Bach posed as Daisy Duke for a poster, which sold 5 million copies. The poster once caused a stir when Nancy Reagan took a liking to it after Bach visited the White House with one as a gift for one of her former schoolteachers then working there.


title: Catherine Bach

text: While she was starring on "The Dukes of Hazzard", her legs were insured for $1,000,000. In 1985, she served as the model for the figurehead for the schooner "Californian".


title: Catherine Bach

text: After the series ended, Bach had roles in a number of low-profile films. From 1992 to 1994, she starred in the Canadian family drama series, "African Skies". In 2006, she guest-starred on "Monk", and in 2010 had a small cameo in the comedy film "You Again". In 2012, Bach joined the cast of CBS daytime soap opera, "The Young and the Restless" in the recurring role of Anita Lawson.


title: Catherine Bach

text: Bach married David Shaw (stepson of Angela Lansbury) in 1976; the couple divorced in 1981. Bach married entertainment lawyer Peter Lopez in August 1990. They had two daughters. On April 30, 2010, 60-year-old Lopez was found shot dead in an apparent suicide.


title: Sphere

text: A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space. That given point is the centre of the sphere, and is the sphere's radius. The earliest known mentions of spheres appear in the work of the ancient Greek mathematicians.


title: Sphere

text: The sphere is a fundamental object in many fields of mathematics. Spheres and nearly-spherical shapes also appear in nature and industry. Bubbles such as soap bubbles take a spherical shape in equilibrium. The Earth is often approximated as a sphere in geography, and the celestial sphere is an important concept in astronomy. Manufactured items including pressure vessels and most curved mirrors and lenses are based on spheres. Spheres roll smoothly in any direction, so most balls used in sports and toys are spherical, as are ball bearings.


title: Sphere

text: As mentioned earlier is the sphere's radius; any line from the center to a point on the sphere is also called a radius.


title: Sphere

text: If a radius is extended through the center to the opposite side of the sphere, it creates a diameter. Like the radius, the length of a diameter is also called the diameter, and denoted . Diameters are the longest line segments that can be drawn between two points on the sphere: their length is twice the radius, =. Two points on the sphere connected by a diameter are antipodal points of each other.


title: Sphere

text: A unit sphere is a sphere with unit radius (=1). For convenience, spheres are often taken to have their center at the origin of the coordinate system, and spheres in this article have their center at the origin unless a center is mentioned.


title: Sphere

text: A "great circle" on the sphere has the same center and radius as the sphere, and divides it into two equal "hemispheres".


title: Sphere

text: Although the Earth is not perfectly spherical, terms borrowed from geography are convenient to apply to the sphere.


title: Sphere

text: If a particular point on a sphere is (arbitrarily) designated as its "north pole", its antipodal point is called the "south pole". The great circle equidistant to each is then the "equator". Great circles through the poles are called lines of longitude or meridians. A line connecting the two poles may be called the axis of rotation. Small circles on the sphere that are parallel to the equator are lines of latitude. In geometry unrelated to astronomical bodies, geocentric terminology should be used only for illustration and "noted" as such, unless there is no chance of misunderstanding.


title: Sphere

text: Mathematicians consider a sphere to be a two-dimensional closed surface embedded in three-dimensional Euclidean space. They draw a distinction a "sphere" and a "ball", which is a three-dimensional manifold with boundary that includes the volume contained by the sphere. An "open ball" excludes the sphere itself, while a "closed ball" includes the sphere: a closed ball is the union of the open ball and the sphere, and a sphere is the boundary of a (closed or open) ball. The distinction between "ball" and "sphere" has not always been maintained and especially older mathematical references talk about a sphere as a solid. The distinction between "circle" and "disk" in the plane is similar.


title: Sphere

text: Since it can be expressed as a quadratic polynomial, a sphere is a quadric surface, a type of algebraic surface.


title: Sphere

text: has no real points as solutions if formula_4 and is called the equation of an imaginary sphere. If formula_5, the only solution of formula_6 is the point formula_7 and the equation is said to be the equation of a point sphere. Finally, in the case formula_8, formula_6 is an equation of a sphere whose center is formula_10 and whose radius is formula_11.


title: Sphere

text: If in the above equation is zero then is the equation of a plane. Thus, a plane may be thought of as a sphere of infinite radius whose center is a point at infinity.


title: Sphere

text: A parametric equation for the sphere with radius formula_12 and center formula_13 can be parameterized using trigonometric functions.


title: Sphere

text: The symbols used here are the same as those used in spherical coordinates. is constant, while varies from 0 to and formula_15 varies from 0 to 2.


title: Sphere

text: In three dimensions, the volume inside a sphere (that is, the volume of a ball, but classically referred to as the volume of a sphere) is


title: Sphere

text: where is the radius and is the diameter of the sphere. Archimedes first derived this formula by showing that the volume inside a sphere is twice the volume between the sphere and the circumscribed cylinder of that sphere (having the height and diameter equal to the diameter of the sphere). This may be proved by inscribing a cone upside down into semi-sphere, noting that the area of a cross section of the cone plus the area of a cross section of the sphere is the same as the area of the cross section of the circumscribing cylinder, and applying Cavalieri's principle. This formula can also be derived using integral calculus, i.e. disk integration to sum the volumes of an infinite number of circular disks of infinitesimally small thickness stacked side by side and centered along the -axis from to , assuming the sphere of radius is centered at the origin.


title: Sphere

text: At any given , the incremental volume () equals the product of the cross-sectional area of the disk at and its thickness ():


title: Sphere

text: At any given , a right-angled triangle connects , and to the origin; hence, applying the Pythagorean theorem yields:


title: Sphere

text: For most practical purposes, the volume inside a sphere inscribed in a cube can be approximated as 52.4% of the volume of the cube, since , where is the diameter of the sphere and also the length of a side of the cube and  ≈ 0.5236. For example, a sphere with diameter 1m has 52.4% the volume of a cube with edge length 1m, or about 0.524 m.


title: Sphere

text: Archimedes first derived this formula from the fact that the projection to the lateral surface of a circumscribed cylinder is area-preserving. Another approach to obtaining the formula comes from the fact that it equals the derivative of the formula for the volume with respect to because the total volume inside a sphere of radius can be thought of as the summation of the surface area of an infinite number of spherical shells of infinitesimal thickness concentrically stacked inside one another from radius 0 to radius . At infinitesimal thickness the discrepancy between the inner and outer surface area of any given shell is infinitesimal, and the elemental volume at radius is simply the product of the surface area at radius and the infinitesimal thickness.