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

An undergraduate student handles chemicals

Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.

The earliest written records of identifiable predecessors to modern science come from Ancient Egypt and Mesopotamia from around 3000 to 1200 BCE. Their contributions to mathematics, astronomy, and medicine entered and shaped the 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 and later by the efforts of Byzantine Greek scholars who brought Greek manuscripts from the dying Byzantine Empire to Western Europe in the Renaissance.

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: natural sciences (e.g., biology, chemistry, and physics), which study the physical world; 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 study formal systems, governed by axioms and rules. There is disagreement whether the formal sciences are science disciplines, because they do not rely on empirical evidence. Applied sciences are disciplines that use scientific knowledge for practical purposes, such as in engineering and medicine.

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 ethical and moral development of commercial products, armaments, health care, public infrastructure, and environmental protection. (Full article...)

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  Featured articles are displayed here, which represent some of the best content on English Wikipedia.
  • Getting It: The Psychology of est, a non-fiction book by American clinical psychologist Sheridan Fenwick first published in 1976, analyzes Werner Erhard's Erhard Seminars Training or est. Fenwick based the book on her own experience of attending a four-day session of the est training, an intensive 60-hour personal-development course in the self-help genre. Large groups of up to 250 people took the est training at one time.

    In the first section of Fenwick's book, she recounts the est training process and the methods used during the course. Fenwick details the rules or "agreements" laid out by the trainers to the attendees, which include not talking to others or leaving the session to go to the bathroom unless during an announced break period. The second section is analytic: Fenwick analyzes the methods used by the est trainers, evaluates the course's potential effects, and discusses Erhard's background. Fenwick concludes that the program's long-term effects are unknown, the est training may not be appropriate for certain groups of people, and that a large proportion of participants report perceived positive effects. (Full article...)
  • Marbled newt

    Triturus is a genus of newts comprising the crested and the marbled newts, which are found from Great Britain through most of continental Europe to westernmost Siberia, Anatolia, and the Caspian Sea region. Their English names refer to their appearance: marbled newts have a green–black colour pattern, while the males of crested newts, which are dark brown with a yellow or orange underside, develop a conspicuous jagged seam on their back and tail during their breeding phase.

    Crested and marbled newts live and breed in vegetation-rich ponds or similar aquatic habitats for two to six months and usually spend the rest of the year in shady, protection-rich land habitats close to their breeding sites. Males court females with a ritualised display, ending in the deposition of a spermatophore that is picked up by the female. After fertilisation, a female lays 200–400 eggs, folding them individually into leaves of water plants. Larvae develop over two to four months before metamorphosing into land-dwelling juveniles. (Full article...)
  • Florence Nagle (26 October 1894 – 30 October 1988) was a British trainer and breeder of racehorses, a breeder of pedigree dogs, and an active feminist. Nagle purchased her first Irish Wolfhound in 1913, and went on to own or breed twenty-one United Kingdom Champions. Best in Show at Crufts in 1960 was awarded to Sulhamstead Merman, who was bred, owned and exhibited by Nagle. She also competed successfully in field trials with Irish Setters, from the 1920s until the mid-1960s resulting in eighteen Field Trial Champions. The male dog who was a linchpin in the 1970s revival of the Irish Red and White Setter breed was descended from one of Nagle's Irish Setters.

    Described as "the Mrs. Pankhurst of British horse racing", Nagle trained her first racehorse in 1920, the Irish-bred colt Fernley. At that time women were forced to employ men to hold a Jockey Club trainers licence on their behalf, or to have licences in their husbands' names. Nagle worked peacefully to redress such injustices to her sex. She successfully challenged the well-established leading gentlemen's clubs of the racing and canine worlds over their gender inequality, and in 1966 became one of the first two women in the United Kingdom licensed to train racehorses. The first racehorse officially trained in Nagle's name was Mahwa, registered as being owned by her friend Miss Newton Deakin, with whom she jointly owned some of her dogs. (Full article...)

  • Rigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive component – and the eponym – of a star system of at least four stars that appear as a single blue-white point of light to the naked eye. This system is located at a distance of approximately 860 light-years (260 pc) from the Sun.

    A star of spectral type B8Ia, Rigel is calculated to be anywhere from 61,500 to 363,000 times as luminous as the Sun, and 18 to 24 times as massive, depending on the method and assumptions used. Its radius is more than seventy times that of the Sun, and its surface temperature is 12,100 K. Due to its stellar wind, Rigel's mass-loss is estimated to be ten million times that of the Sun. With an estimated age of seven to nine million years, Rigel has exhausted its core hydrogen fuel, expanded, and cooled to become a supergiant. It is expected to end its life as a type II supernova, leaving a neutron star or a black hole as a final remnant, depending on the initial mass of the star. (Full article...)
  • Sir Robert Eric Mortimer Wheeler CH CIE MC TD FRS FBA FSA (10 September 1890 – 22 July 1976) was a British archaeologist and officer in the British Army. Over the course of his career, he served as Director of both the National Museum of Wales and London Museum, Director-General of the Archaeological Survey of India, and the founder and Honorary Director of the Institute of Archaeology in London, in addition to writing twenty-four books on archaeological subjects.

    Born in Glasgow to a middle-class family, Wheeler was raised largely in Yorkshire before moving to London in his teenage years. After studying classics at University College London (UCL), he began working professionally in archaeology, specialising in the Romano-British period. During World War I he volunteered for service in the Royal Artillery, being stationed on the Western Front, where he rose to the rank of major and was awarded the Military Cross. Returning to Britain, he obtained his doctorate from UCL before taking on a position at the National Museum of Wales, first as Keeper of Archaeology and then as Director, during which time he oversaw excavation at the Roman forts of Segontium, Y Gaer, and Isca Augusta with the aid of his first wife, Tessa Wheeler. Influenced by the archaeologist Augustus Pitt Rivers, Wheeler argued that excavation and the recording of stratigraphic context required an increasingly scientific and methodical approach, developing the "Wheeler method". In 1926, he was appointed Keeper of the London Museum; there, he oversaw a reorganisation of the collection, successfully lobbied for increased funding, and began lecturing at UCL. (Full article...)

  • The short-beaked echidna (Tachyglossus aculeatus), also called the short-nosed echidna, is one of four living species of echidna and the only member of the genus Tachyglossus. It is covered in fur and spines and has a distinctive snout and a specialized tongue, which it uses to catch its insect prey at a great speed. Like the other extant monotremes, the short-beaked echidna lays eggs; the monotremes are the only living group of mammals to do so.

    The short-beaked echidna has extremely strong front limbs and claws, which allow it to burrow quickly with great power. As it needs to be able to survive underground, it has a significant tolerance to high levels of carbon dioxide and low levels of oxygen. It has no weapons or fighting ability but repels predators by curling into a ball and deterring them with its spines. It lacks the ability to sweat and cannot deal with heat well, so it tends to avoid daytime activity in hot weather. It can swim if needed. The snout has mechanoreceptors and electroreceptors that help the echidna to detect its surroundings. (Full article...)
  • Aerial view in 2009: "The most famous twentieth century garden in England"

    Sissinghurst Castle Garden, at Sissinghurst in the Weald of Kent in England, was created by Vita Sackville-West, poet and writer, and her husband Harold Nicolson, author and diplomat. It is among the most famous gardens in England and is designated Grade I on Historic England's register of historic parks and gardens. It was bought by Sackville-West in 1930, and over the next thirty years, working with, and later succeeded by, a series of notable head gardeners, she and Nicolson transformed a farmstead of "squalor and slovenly disorder" into one of the world's most influential gardens. Following Sackville-West's death in 1962, the estate was donated to the National Trust. It is one of the Trust's most popular properties, with nearly 200,000 visitors in 2017.

    The gardens contain an internationally respected plant collection, particularly the assemblage of old garden roses. The writer Anne Scott-James considered the roses at Sissinghurst to be "one of the finest collections in the world". A number of plants propagated in the gardens bear names related to people connected with Sissinghurst or the name of the garden itself. The garden design is based on axial walks that open onto enclosed gardens, termed "garden rooms", one of the earliest examples of this gardening style. Among the individual "garden rooms", the White Garden has been particularly influential, with the horticulturalist Tony Lord describing it as "the most ambitious ... of its time, the most entrancing of its type." (Full article...)
  • Reconstructed skeleton, Museo Municipal Carmen Funes, Plaza Huincul, Argentina. The original vertebrae are seen on the lower left

    Argentinosaurus is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, Argentinosaurus is one of the largest known land animals of all time, perhaps the largest, reaching 30–35 metres (98–115 ft) in length and 60–75 tonnes (66–83 short tons) in body mass. It was a member of Titanosauria, the dominant group of sauropods during the Cretaceous. It is widely regarded by many paleontologists as the biggest dinosaur ever, and perhaps lengthwise the longest animal ever, though both claims have no concrete evidence yet.

    The first Argentinosaurus bone was discovered in 1987 by a farmer on his farm near the city of Plaza Huincul. A scientific excavation of the site led by the Argentine palaeontologist José Bonaparte was conducted in 1989, yielding several back vertebrae and parts of a sacrum—fused vertebrae between the back and tail vertebrae. Additional specimens include a complete femur (thigh bone) and the shaft of another. Argentinosaurus was named by Bonaparte and the Argentine palaeontologist Rodolfo Coria in 1993; the genus contains a single species, A. huinculensis. The generic name Argentinosaurus means "Argentine lizard", and the specific name huinculensis refers to its place of discovery, Plaza Huincul. (Full article...)
  • A pair (male on left and female on right)

    The red-tailed black cockatoo (Calyptorhynchus banksii) also known as Banksian- or Banks' black cockatoo, is a large black cockatoo native to Australia. Adult males have a characteristic pair of bright red panels on the tail that gives the species its name. It is more common in the drier parts of the continent. Five subspecies are recognised, differing chiefly in beak size. Although the more northerly subspecies are widespread, the two southern subspecies, the forest red-tailed black cockatoo and the south-eastern red-tailed black cockatoo are under threat.

    The species is usually found in eucalyptus woodlands, or along water courses. In the more northerly parts of the country, these cockatoos are commonly seen in large flocks. They are seed eaters and cavity nesters, and as such depend on trees with fairly large diameters, generally Eucalyptus. Populations in southeastern Australia are threatened by deforestation and other habitat alterations. Of the black cockatoos, the red-tailed is the most adaptable to aviculture, although black cockatoos are much rarer and much more expensive in aviculture outside Australia. (Full article...)
  • Map showing nuclear test sites in Australia

    Between 1956 and 1963, the United Kingdom conducted seven nuclear tests at the Maralinga site in South Australia, part of the Woomera Prohibited Area about 800 kilometres (500 mi) north west of Adelaide. Two major test series were conducted: Operation Buffalo in 1956 and Operation Antler the following year. Approximate weapon yields ranged from 1 to 27 kilotons of TNT (4 to 100 TJ). The Maralinga site was also used for minor trials, tests of nuclear weapons components not involving nuclear explosions. Kittens were trials of neutron initiators; Rats and Tims measured how the fissile core of a nuclear weapon was compressed by the high explosive shock wave; and Vixens investigated the effects of fire or non-nuclear explosions on atomic weapons. The minor trials, numbering around 550, ultimately generated far more contamination than the major tests.

    Operation Buffalo consisted of four tests; One Tree (12.9 kilotons of TNT (54 TJ)) and Breakaway (10.8 kilotons of TNT (45 TJ)) were detonated on towers, Marcoo (1.4 kilotons of TNT (5.9 TJ)) at ground level, and the Kite (2.9 kilotons of TNT (12 TJ)) was released by a Royal Air Force (RAF) Vickers Valiant bomber from a height of 11,000 metres (35,000 ft). This was the first drop of a British nuclear weapon from an aircraft. Operation Antler in 1957 tested new, light-weight nuclear weapons. Three tests were conducted in this series: Tadje (0.93 kilotons of TNT (3.9 TJ)), Biak (5.67 kilotons of TNT (23.7 TJ)) and Taranak (26.6 kilotons of TNT (111 TJ)). The first two were conducted from towers, while the last was suspended from balloons. Tadje used cobalt pellets as a tracer for determining yield, resulting in rumours that Britain was developing a cobalt bomb. (Full article...)
  • Tutupaca viewed from a southern direction.

    Tutupaca is a volcano in the region of Tacna in Peru. It is part of the Peruvian segment of the Central Volcanic Zone, one of several volcanic belts in the Andes. Tutupaca consists of three overlapping volcanoes formed by lava flows and lava domes made out of andesite and dacite, which grew on top of older volcanic rocks. The highest of these is usually reported to be 5,815 metres (19,078 ft) tall and was glaciated in the past.

    Several volcanoes in Peru have been active in recent times, including Tutupaca. Their volcanism is caused by the subduction of the Nazca Plate beneath the South America Plate. One of these volcanoes collapsed in historical time, probably in 1802, generating a large debris avalanche with a volume likely exceeding 0.6–0.8 cubic kilometres (0.14–0.19 cu mi) and a pyroclastic flow. The associated eruption was among the largest in Peru for which there are historical records. The volcano became active about 700,000 years ago, and activity continued into the Holocene, but whether there were historical eruptions was initially unclear; some eruptions were instead attributed to the less eroded Yucamane volcano. The Peruvian government plans to monitor the volcano for future activity. Tutupaca features geothermal manifestations with fumaroles and hot springs. (Full article...)

  • Richard Phillips Feynman (/ˈfaɪnmən/; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfluidity of supercooled liquid helium, as well as his work in particle physics for which he proposed the parton model. For his contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin'ichirō Tomonaga.

    Feynman developed a widely used pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World, he was ranked the seventh-greatest physicist of all time. (Full article...)
  • Image of Sirius A and Sirius B taken by the Hubble Space Telescope. Sirius B, which is a white dwarf, can be seen as a faint point of light to the lower left of the much brighter Sirius A.


    A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name white dwarf was coined by Willem Luyten in 1922.

    White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen-fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant during which it fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon (around 1 billion K), an inert mass of carbon and oxygen will build up at its center. After such a star sheds its outer layers and forms a planetary nebula, it will leave behind a core, which is the remnant white dwarf. Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf). If the mass of the progenitor is between 8 and 10.5 solar masses (M☉), the core temperature will be sufficient to fuse carbon but not neon, in which case an oxygen–neon–magnesium (ONeMg or ONe) white dwarf may form. Stars of very low mass will be unable to fuse helium; hence, a helium white dwarf may form by mass loss in binary systems. (Full article...)
  • Life drawing by Paul Jossigny, 1770s

    Newton's parakeet (Psittacula exsul), also known as the Rodrigues parakeet or Rodrigues ring-necked parakeet, is an extinct species of parrot that was endemic to the Mascarene island of Rodrigues in the western Indian Ocean. Several of its features diverged from related species, indicating long-term isolation on Rodrigues and subsequent adaptation. The rose-ringed parakeet of the same genus is a close relative and probable ancestor. Newton's parakeet may itself have been ancestral to the endemic parakeets of nearby Mauritius and Réunion.

    Around 40 centimetres (16 in) long, Newton's parakeet was roughly the size of a rose-ringed parakeet. Its plumage was mostly greyish or slate blue in colour, which is unusual in Psittacula, a genus containing mostly green species. The male had stronger colours than the female and possessed a reddish instead of black beak, but details of a mature male's appearance are uncertain; only one male specimen is known, and it is believed to be immature. Mature males might have possessed red patches on the wing like the related Alexandrine parakeet. Both sexes had a black collar running from the chin to the nape, but this was clearer in the male. The legs were grey and the iris yellow. Some 17th-century accounts indicate that some members of the species were green, which would suggest that both blue and green colour morphs occurred, but no definitive explanation exists for these reports. Little is known about its behaviour in life, but it may have fed on the nuts of the bois d'olive tree, along with leaves. It was very tame and was able to mimic speech. (Full article...)
  • Absorption lines in the visible spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the visible spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases).

    In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum.

    In astronomy and cosmology, the three main causes of electromagnetic redshift are (Full article...)

Selected image

DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus.
Credit: Polyparadigm
Direct current-generated plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. Plasma-enhanced chemical vapor deposition processes utilize plasma to enhance chemical reaction rates. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The red color in the picture is black-body radiation.

Selected biography

William Sanford Nye (born November 27, 1955) is an American mechanical engineer, science communicator, and television presenter. He is best known as the host of the science education television show Bill Nye the Science Guy (1993–1999) and as a science educator in pop culture.

Born in Washington, D.C., Nye began his career as a mechanical engineer for Boeing in Seattle, where he invented a hydraulic resonance suppressor tube used on 747 airplanes. In 1986, he left Boeing to pursue comedy—writing and performing for the local sketch television show Almost Live!, where he regularly conducted wacky scientific experiments.

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Science News

Further information: 2023 in science
12 February 2023 – Asteroid impact prediction
Researchers at the Konkoly Observatory in Hungary discover 2023 CX1, a 1-metre (3.3-foot) asteroid predicted to fall harmlessly as a fireball over the English Channel at 03:00 UTC, making it the seventh asteroid to be discovered before impacting Earth. (JPL Center for NEO Studies)
27 January 2023 – Rewilding
Cheetah reintroduction in India
South Africa agrees to send twelve cheetahs to India each year for the next eight to ten years to help secure a viable wild population. The Asiatic cheetah went extinct in India in the 1940s due to overhunting and habitat destruction. (BBC News)
24 January 2023 – Doomsday Clock
The Bulletin of the Atomic Scientists announces that the Doomsday Clock has been moved up to 90 seconds before midnight, largely due to the 2022 Russian invasion of Ukraine. (NPR) (CNN)
16 December 2022 –
The AquaDom aquarium in Berlin, Germany, home to 1,500 tropical fish of more than 100 different species, bursts, flooding local streets. The majority of the fish die during the incident, and two people are injured. (BBC News)
25 November 2022 –
At the 19th CITES Conference of the Parties in Panama City, member states adopt stricter measures on the trade of 54 requiem and hammerhead shark species. (AFP via Voice of America)

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