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For a topic outline of science, see Outline of science.

French Academy of Sciences

Members of the Academy in 1667 with Louis XIV

Science (from Latin scientia 'knowledge') is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the world.

The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3000 to 1200 BCE. Their contributions to mathematics, astronomy, and medicine entered and shaped Greek natural philosophy of classical antiquity, whereby formal attempts were made to provide explanations of events in the physical world based on natural causes. After the fall of the Western Roman Empire, knowledge of Greek conceptions of the world deteriorated in Western Europe during the early centuries (400 to 1000 CE) of the Middle Ages, but was preserved in the Muslim world during the Islamic Golden Age. The recovery and assimilation of Greek works and Islamic inquiries into Western Europe from the 10th to 13th century revived "natural philosophy", which was later transformed by the Scientific Revolution that began in the 16th century as new ideas and discoveries departed from previous Greek conceptions and traditions. The scientific method soon played a greater role in knowledge creation and it was not until the 19th century that many of the institutional and professional features of science began to take shape; along with the changing of "natural philosophy" to "natural science."

Modern science is typically divided into three major branches that consist of the natural sciences (e.g., biology, chemistry, and physics), which study nature in the broadest sense; the social sciences (e.g., economics, psychology, and sociology), which study individuals and societies; and the formal sciences (e.g., logic, mathematics, and theoretical computer science), which deal with symbols governed by rules. There is disagreement, however, on whether the formal sciences actually constitute a science as they do not rely on empirical evidence. Disciplines that use existing scientific knowledge for practical purposes, such as engineering and medicine, are described as applied sciences.

New knowledge in science is advanced by research from scientists who are motivated by curiosity about the world and a desire to solve problems. Contemporary scientific research is highly collaborative and is usually done by teams in academic and research institutions, government agencies, and companies. The practical impact of their work has led to the emergence of science policies that seek to influence the scientific enterprise by prioritizing the development of commercial products, armaments, health care, public infrastructure, and environmental protection. (Full article...)

Featured article

  Featured articles are displayed here, which represent some of the best content on English Wikipedia.

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  The Kreutz sungrazers (/ˈkrɔɪts/ (listen) KROYTS) are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. They are believed to be fragments of one large comet that broke up several centuries ago and are named for German astronomer Heinrich Kreutz, who first demonstrated that they were related. A Kreutz sungrazers's aphelion is about 170 AU from the Sun; these sungrazers make their way from the distant outer Solar System from a patch in the sky in Canis Major, to the inner Solar System, to their perihelion point near the Sun, and then leave the inner Solar System in their return trip to their aphelion.
  
  Several members of the Kreutz family have become great comets, occasionally visible near the Sun in the daytime sky. The most recent of these was Comet Ikeya–Seki in 1965, which may have been one of the brightest comets in the last millennium. It has been suggested that another cluster of bright Kreutz system comets may begin to arrive in the inner Solar System in the next few years to decades. (Full article...)
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  A man with a smaller right leg due to poliomyelitis

  
  Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. In about 0.5 percent of cases, it moves from the gut to affect the central nervous system, and there is muscle weakness resulting in a flaccid paralysis. This can occur over a few hours to a few days. The weakness most often involves the legs, but may less commonly involve the muscles of the head, neck, and diaphragm. Many people fully recover. In those with muscle weakness, about 2 to 5 percent of children and 15 to 30 percent of adults die. Up to 70 percent of those infected have no symptoms. Another 25 percent of people have minor symptoms such as fever and a sore throat, and up to 5 percent have headache, neck stiffness, and pains in the arms and legs. These people are usually back to normal within one or two weeks. Years after recovery, post-polio syndrome may occur, with a slow development of muscle weakness similar to that which the person had during the initial infection.
  
  Poliovirus is usually spread from person to person through infected fecal matter entering the mouth. It may also be spread by food or water containing human feces and less commonly from infected saliva. Those who are infected may spread the disease for up to six weeks even if no symptoms are present. The disease may be diagnosed by finding the virus in the feces or detecting antibodies against it in the blood. The disease occurs naturally only in humans. (Full article...)
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  Sir James Chadwick, CH, FRS (20 October 1891 – 24 July 1974) was a British physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932. In 1941, he wrote the final draft of the MAUD Report, which inspired the U.S. government to begin serious atomic bomb research efforts. He was the head of the British team that worked on the Manhattan Project during World War II. He was knighted in Britain in 1945 for his achievements in physics.
  
  Chadwick graduated from the Victoria University of Manchester in 1911, where he studied under Ernest Rutherford (known as the "father of nuclear physics"). At Manchester, he continued to study under Rutherford until he was awarded his MSc in 1913. The same year, Chadwick was awarded an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851. He elected to study beta radiation under Hans Geiger in Berlin. Using Geiger's recently developed Geiger counter, Chadwick was able to demonstrate that beta radiation produced a continuous spectrum, and not discrete lines as had been thought. Still in Germany when World War I broke out in Europe, he spent the next four years in the Ruhleben internment camp. (Full article...)
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  Aleeta curvicosta (commonly known as the floury baker or floury miller, known until 2003 as Abricta curvicosta) is a species of cicada, one of Australia's most familiar insects. Native to the continent's eastern coastline, it was described in 1834 by Ernst Friedrich Germar. The floury baker is the only described species in the genus Aleeta.
  
  The floury baker's distinctive appearance and loud call make it popular with children. Both the common and genus name are derived from the white, flour-like filaments covering the adult body. Its body and eyes are generally brown with pale patterns including a light-coloured line along the midline of the pronotum. Its forewings have distinctive dark brown patches at the base of two of their apical cells. The female is larger than the male, although species size overall varies geographically, with larger animals associated with regions of higher rainfall. The male has distinctive genitalia and a loud and complex call generated by the frequent buckling of ribbed tymbals and amplified by abdominal air sacs. (Full article...)
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  Distribution of Transandinomys bolivaris in southern Central and northwestern South America

  
  Transandinomys bolivaris, also known as the long-whiskered rice rat, is a rodent in the family Cricetidae. It is found in humid forest from northeastern Honduras to western Ecuador, up to 1,800 m (5,900 ft) above sea level. Since it was first described in 1901 from Ecuador, six scientific names have been introduced for it, but their common identity was not documented until 1998 and the species has long been known under the name Oryzomys bombycinus, described from Panama in 1912. The name Oryzomys bolivaris was used before it was moved to the new genus Transandinomys with Transandinomys talamancae (formerly Oryzomys talamancae) in 2006.
  
  It is a medium-sized rice rat distinguished by its very long vibrissae (whiskers)—those above the eyes are up to 50 mm (2 in) long. The fur, which is soft and dense, is usually dark brown above and light gray below; it is darker in juveniles. The feet are long and the tail is about as long as the head and body. The skull is narrow and has a broad interorbital region (between the eyes). The species generally lives on the ground. Although it is rare, its conservation status is thought to be secure. (Full article...)
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  Reconstructed skeleton, Burpee Museum of Natural History

  
  Thescelosaurus (/ˌθɛsɪləˈsɔːrəs/ THESS-il-ə-SOR-əs; ancient Greek θέσκελος- (theskelos-) meaning "godlike", "marvellous", or "wondrous" and σαυρος (sauros) "lizard") was a genus of small neornithischian dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous–Paleogene extinction event around 66 million years ago. The preservation and completeness of many of its specimens indicate that it may have preferred to live near streams.
  
  This bipedal neornithischian is known from several partial skeletons and skulls that indicate it grew to between 2.5 and 4.0 meters (8.2 to 13.1 ft) in length on average. It had sturdy hind limbs, small wide hands, and a head with an elongate pointed snout. The form of the teeth and jaws suggest a primarily herbivorous animal. This genus of dinosaur is regarded as a specialized neornithischian, traditionally described as a hypsilophodont, but more recently recognized as distinct from Hypsilophodon. Several species have been suggested for this genus. Three currently are recognized as valid: the type species T. neglectus, T. garbanii and T. assiniboiensis. (Full article...)
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  The Benty Grange helmet, on a modern transparent support

  
  The Benty Grange helmet is a boar-crested Anglo-Saxon helmet from the 7th century AD. It was excavated by Thomas Bateman in 1848 from a tumulus at the Benty Grange farm in Monyash in western Derbyshire. The grave had probably been looted by the time of Bateman's excavation, but still contained other high-status objects suggestive of a richly furnished burial, such as the fragmentary remains of a hanging bowl. The helmet is displayed at Sheffield's Weston Park Museum, which purchased it from Bateman's estate in 1893.
  
  The helmet was constructed by covering the outside of an iron framework with plates of horn and the inside with cloth or leather; the organic material has since decayed. It would have provided some protection against weapons, but was also ornate and may have been intended for ceremonial use. It was the first Anglo-Saxon helmet to be discovered; five others, from Sutton Hoo, York, Wollaston, Shorwell, and Staffordshire, have been found since. The helmet features a unique combination of structural and technical attributes, but contemporaneous parallels exist for its individual characteristics. It is classified as one of the "crested helmets" used in Northern Europe from the 6th to 11th centuries AD. (Full article...)
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  Banksia dentata, commonly known as the tropical banksia, is a species of tree in the genus Banksia. It occurs across northern Australia, southern New Guinea and the Aru Islands. Growing as a gnarled tree to 7 m (23 ft) high, it has large green leaves up to 22 cm (8.7 in) long with dentate (toothed) margins. The cylindrical yellow inflorescences (flower spikes), up to 13 cm (5.1 in) high, appear over the cooler months, attracting various species of honeyeaters, sunbirds, the sugar glider and a variety of insects. Flowers fall off the ageing spikes, which swell and develop follicles containing up to two viable seeds each.
  
  Banksia dentata is one of four Banksia species collected by Sir Joseph Banks in 1770, and one of the four species published in 1782 as part of Carolus Linnaeus the Younger's original description of Banksia. Within the genus, it is classified in the series Salicinae, a group of species from Australia's eastern states. Genetic studies show it is a basal member (early offshoot) within the group. Banksia dentata is found in tropical grassland known as savanna, associated with Pandanus and Melaleuca. It regenerates from bushfire by regrowing from its woody base, known as a lignotuber. (Full article...)
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  A territorial impala ram in northern Botswana

  
  The impala (/ɪmˈpɑːlə, -ˈpælə/, Aepyceros melampus) is a medium-sized antelope found in eastern and southern Africa. The sole member of the genus Aepyceros, it was first described to European audiences by German zoologist Hinrich Lichtenstein in 1812. Two subspecies are recognised—the common impala, and the larger and darker black-faced impala. The impala reaches 70–92 cm (28–36 in) at the shoulder and weighs 40–76 kg (88–168 lb). It features a glossy, reddish brown coat. The male's slender, lyre-shaped horns are 45–92 cm (18–36 in) long.
  
  Active mainly during the day, the impala may be gregarious or territorial depending upon the climate and geography. Three distinct social groups can be observed: the territorial males, bachelor herds and female herds. The impala is known for two characteristic leaps that constitute an anti-predator strategy. Browsers as well as grazers, impala feed on monocots, dicots, forbs, fruits and acacia pods (whenever available). An annual, three-week-long rut takes place toward the end of the wet season, typically in May. Rutting males fight over dominance, and the victorious male courts female in oestrus. Gestation lasts six to seven months, following which a single calf is born and immediately concealed in cover. Calves are suckled for four to six months; young males—forced out of the all-female groups—join bachelor herds, while females may stay back. (Full article...)
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  Pale fork-marked lemur (P. pallescens)

  
  Fork-marked lemurs or fork-crowned lemurs are strepsirrhine primates; the four species comprise the genus Phaner. Like all lemurs, they are native to Madagascar, where they are found only in the west, north, and east sides of the island. They are named for the two black stripes which run up from the eyes, converge on the top of the head, and run down the back as a single black stripe. They were originally placed in the genus Lemur in 1839, later moved between the genera Cheirogaleus and Microcebus, and given their own genus in 1870 by John Edward Gray. Only one species (Phaner furcifer) was recognized, until three subspecies described in 1991 were promoted to species status in 2001. New species may yet be identified, particularly in northeast Madagascar.
  
  Fork-marked lemurs are among the least studied of all lemurs and are some of the largest members of the family Cheirogaleidae, weighing around 350 grams (12 oz) or more. They are the most phylogenetically distinct of the cheirogaleids, and considered a sister group to the rest of the family. Aside from their dorsal forked stripe, they have dark rings around their eyes, and large membranous ears. Males have a scent gland on their throat, but only use it during social grooming, not for marking territory. Instead, they are very vocal, making repeated calls at the beginning and end of the night. Like the other members of their family, they are nocturnal, and sleep in tree holes and nests during the day. Monogamous pairing is typical for fork-marked lemurs, and females are dominant. Females are thought to have only one offspring every two years or more. (Full article...)
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  A metalloid is a type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specificity, the term remains in use in the literature of chemistry.
  
  The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Five elements are less frequently so classified: carbon, aluminium, selenium, polonium, and astatine. On a standard periodic table, all eleven elements are in a diagonal region of the p-block extending from boron at the upper left to astatine at lower right. Some periodic tables include a dividing line between metals and nonmetals, and the metalloids may be found close to this line. (Full article...)
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  Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus. It is one of the 48 ancient constellations listed by the 2nd-century astronomer Ptolemy, and among the 88 modern constellations defined by the International Astronomical Union (IAU). It is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west. Some star atlases during the early 19th century also depicted Perseus holding the disembodied head of Medusa, whose asterism was named together as Perseus et Caput Medusae; however, this never came into popular usage.
  
  The galactic plane of the Milky Way passes through Perseus, whose brightest star is the yellow-white supergiant Alpha Persei (also called Mirfak), which shines at magnitude 1.79. It and many of the surrounding stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol (Beta Persei), linked with ominous legends because of its variability, which is noticeable to the naked eye. Rather than being an intrinsically variable star, it is an eclipsing binary. Other notable star systems in Perseus include X Persei, a binary system containing a neutron star, and GK Persei, a nova that peaked at magnitude 0.2 in 1901. The Double Cluster, comprising two open clusters quite near each other in the sky, was known to the ancient Chinese. The constellation gives its name to the Perseus cluster (Abell 426), a massive galaxy cluster located 250 million light-years from Earth. It hosts the radiant of the annual Perseids meteor shower—one of the most prominent meteor showers in the sky. (Full article...)
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  Suillus pungens, commonly known as the pungent slippery jack or the pungent suillus, is a species of fungus in the genus Suillus. The fruit bodies of the fungus have slimy convex caps up to14 cm (5.5 in) wide. The mushroom is characterized by the very distinct color changes that occur in the cap throughout development. Typically, the young cap is whitish, later becoming grayish-olive to reddish-brown or a mottled combination of these colors. The mushroom has a dotted stem (stipe) up to 7 cm (2.8 in) long, and 2 cm (0.8 in) thick. On the underside on the cap is the spore-bearing tissue consisting of minute vertically arranged tubes that appear as a surface of angular, yellowish pores. The presence of milky droplets on the pore surface of young individuals, especially in humid environments, is a characteristic feature of this species. S. pungens can usually be distinguished from other similar Suillus species by differences in distribution, odor and taste. The mushroom is considered edible, but not highly regarded.
  
  An ectomycorrhizal species, S. pungens forms an intimate mutualistic relationship between its underground mycelium and the young roots of the associated host tree. The fungus—limited in distribution to California—fruits almost exclusively with Monterey and bishop pine, two trees with small and scattered natural ranges concentrated in the West Coast of the United States. Several studies have investigated the role of S. pungens in the coastal Californian forest ecosystem it occupies. Although the species produces more fruit bodies than other competing ectomycorrhizal fungi in the same location, it is not a dominant root colonizer, and occupies only a small percentage of ectomycorrhizal root tips. The fungus's propensity to fruit prolifically despite minimal root colonization is a result of its ability to efficiently transfer nutrients from its host for its own use. (Full article...)
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  The Siberian accentor (Prunella montanella) is a small passerine bird that breeds in northern Russia from the Ural Mountains eastwards across Siberia. It is migratory, wintering in Korea and eastern China, with rare occurrences in western Europe and northwestern North America. Its typical breeding habitat is subarctic deciduous forests and open coniferous woodland, often close to water, although it also occurs in mountains and spruce taiga. It inhabits bushes and shrubs in winter, frequently near streams, but may also be found in dry grassland and woods.
  
  The Siberian accentor has brown upperparts and wings, with bright chestnut streaking on its back and a greyish-brown rump and tail. The head has a dark brown crown and a long, wide pale yellow supercilium ("eyebrow"). All plumages are quite similar. The nest is an open cup in dense shrub or a tree into which the female lays four to six glossy deep blue-green eggs that hatch in about ten days. Adults and chicks feed mainly on insects, typically picked off the ground, but sometimes taken from vegetation. In winter, the accentors may also consume seeds or feed near human habitation. (Full article...)
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  Two sheep on the shoreline of North Ronaldsay

  
  The North Ronaldsay or Orkney is a breed of sheep from North Ronaldsay, the northernmost island of Orkney, off the north coast of Scotland. It belongs to the Northern European short-tailed sheep group of breeds, and has evolved without much cross-breeding with modern breeds. It is a smaller sheep than most, with the rams (males) horned and ewes (females) mostly hornless. It was formerly kept primarily for wool, but now the two largest flocks are feral, one on North Ronaldsay and another on the Orkney island of Auskerry. The Rare Breeds Survival Trust lists the breed as a priority on its 2021–2022 watchlist, and they are in danger of extinction, with fewer than 600 registered breeding females in the United Kingdom.
  
  The semi-feral flock on North Ronaldsay is the original flock that evolved to subsist almost entirely on seaweed – they are one of few mammals to do this. They are confined to the foreshore by a 1.8 m (6 ft) drystane dyke, which completely encircles the island, forcing the sheep to evolve this unusual characteristic. The wall was built as kelping (the production of soda ash from seaweed) on the shore became uneconomical. Sheep were confined to the shore to protect the fields and crofts inside, and afterwards subsisted largely on seaweed. (Full article...)

Selected image

Paramecium

Credit: Josh Grosse

Paramecium aurelia, the best known of all ciliates. The bubbles throughout the cell are vacuoles. The entire surface is covered in cilia, which are blurred by their rapid movement. Cilia are short, hair-like projections that help with locomotion.

Selected biography

Galileo Galilei (February 15, 1564 – January 8, 1642) was an Italian physicist, astronomer, and philosopher who is closely associated with the scientific revolution. His achievements include improvements to the telescope, a variety of astronomical observations, the first and second laws of motion, and effective support for Copernicanism. According to Stephen Hawking, Galileo has contributed more to the creation of the modern natural sciences than anybody else. He is the "father of modern astronomy," the "father of modern physics," and the "father of science." The work of Galilei is considered to be a significant break from that of Aristotle.

Did you know...

• ...that the endangered golden lion tamarin (pictured) has a long, but not prehensile, tail?
• ...that the Witch's hat is the common name of a colourful orange-red toadstool?
• ...that Grandi's series 1 − 1 + 1 − 1 + • • • is divergent and appears to equal 0, yet in some sense "sums" to ¹⁄₂ — a paradox once linked to the creation ex nihilo of the universe?
• ...that Derek Freeman was an anthropologist whose refutation of Margaret Mead's work "ignited controversy of a scale, visibility, and ferocity never before seen in anthropology"?
• ...that the New Year's Eve snowstorm of 1963/1964 dropped over 17 inches of snow at Huntsville, Alabama, simultaneously setting new snowfall records for any day, week, or month in their history?

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