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Science (from the Latin word scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3500 to 3000 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 study abstract concepts. 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.
Science is based on research, which is commonly conducted in academic and research institutions as well as in government agencies and companies. The practical impact of scientific research 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, and environmental protection.
Selected article
Pallas's leaf warbler or Pallas's warbler (Phylloscopus proregulus) is a bird that breeds in mountain forests from southern Siberia east to northern Mongolia and northeast China. It is named for German zoologist Peter Simon Pallas, who first formally described it. This leaf warbler is strongly migratory, wintering mainly in south China and adjacent areas of southeast Asia, although in recent decades increasing numbers have been found in Europe in autumn.
Pallas's leaf warbler is one of the smallest Palearctic warblers, with a relatively large head and short tail. It has greenish upperparts and white underparts, a lemon-yellow rump, and yellow double wingbars, supercilia and central crown stripe. It is similar in appearance to several other Asian warblers, including some that were formerly considered to be its subspecies, although its distinctive vocalisations aid identification.
Callisto's anti-Jovian hemisphere imaged in 2001 by NASA's Galileo spacecraft. It shows a heavily cratered terrain. The large impact structure Asgard is on the limb at upper right. The prominent rayed crater below and just right of center is Bran.
Callisto /kəˈlɪstoʊ/, or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System that may not be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000 km. It is not in an orbital resonance like the three other Galilean satellites—Io, Europa, and Ganymede—and is thus not appreciably tidally heated. Callisto's rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward. Because of this, there is a sub-Jovian point on Callisto's surface, from which Jupiter would appear to hang directly overhead. It is less affected by Jupiter's magnetosphere than the other inner satellites because of its more remote orbit, located just outside Jupiter's main radiation belt.
Callisto is composed of approximately equal amounts of rock and ices, with a density of about 1.83 g/cm3, the lowest density and surface gravity of Jupiter's major moons. Compounds detected spectroscopically on the surface include water ice, carbon dioxide, silicates, and organic compounds. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate core and possibly a subsurface ocean of liquid water at depths greater than 100 km.
Photographed as a featureless disc by Voyager 2 in 1986
Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus, who, according to Greek mythology, was the grandfather of Zeus (Jupiter) and father of Cronus (Saturn). It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the other gas giants. Uranus's atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons. It has the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C; −371 °F), and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.
Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit. Its north and south poles, therefore, lie where most other planets have their equators. In 1986, images from Voyager 2 showed Uranus as an almost featureless planet in visible light, without the cloud bands or storms associated with the other giant planets. Voyager 2 remains the only spacecraft to visit the planet. Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second (900 km/h; 560 mph).
A breeding male of the subspecies ammodendri in southeastern Kazakhstan
The saxaul sparrow (Passer ammodendri) is a passerine bird of the sparrow family Passeridae, found in parts of Central Asia. At 14–16 centimetres (5.5–6.3 in) and 25–32 grams (0.88–1.13 oz), it is among the larger sparrows. Both sexes have plumage ranging from dull grey to sandy brown, and pale brown legs. Females have less boldly coloured plumage and bills, lacking the pattern of black stripes on the male's head. The head markings of both sexes make the saxaul sparrow distinctive, and unlikely to be confused with any other bird. Vocalisations include a comparatively soft and musical chirping call, a song, and a flight call.
Three subspecies are recognised, differing in the overall tone of their plumage and in the head striping of the female. The subspecies ammodendri occurs in the west of the saxaul sparrow's range, while stoliczkae and nigricans occur in the east. This distribution falls into six probably disjunct areas across Central Asia, from central Turkmenistan to northern Gansu in China. A bird of deserts, the saxaul sparrow favours areas with shrubs such as the saxaul, near rivers and oases. Though it has lost parts of its range to habitat destruction caused by agriculture, it is not seriously threatened by human activities.- Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.
All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208Pb. On Earth, thorium, bismuth, and uranium are the only three radioactive elements that still occur naturally in large quantities as primordial elements. It is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals.
The secretarybird or secretary bird (Sagittarius serpentarius) is a large, mostly terrestrial bird of prey. Endemic to Africa, it is usually found in the open grasslands and savanna of the sub-Saharan region. John Frederick Miller described the species in 1779. Although a member of the order Accipitriformes, which also includes many other diurnal birds of prey such as kites, hawks, vultures, and harriers, it is placed in its own family, Sagittariidae. The secretarybird is instantly recognisable as a very large bird with an eagle-like body on crane-like legs that give the bird a height of as much as 1.3 m (4 ft 3 in). The sexes are similar in appearance. Adults have a featherless red-orange face and predominantly grey plumage, with a flattened dark crest and black flight feathers and thighs.
Breeding can take place at any time of year, but tends to be late in the dry season. The nest is built at the top of a thorny tree, and a clutch of one to three eggs is laid. In years with plentiful food all three young can survive to fledging. The secretarybird hunts and catches prey on the ground, often stomping on victims to kill them. Insects and small vertebrates make up its diet.
The white-eyed river martin (Pseudochelidon sirintarae) is a passerine bird, one of only two members of the river martin subfamily of the swallows. Since it has significant differences from its closest relative, the African river martin, it is sometimes placed in its own genus, Eurochelidon. First found in 1968, it is known only from a single wintering site in Thailand, and may be extinct, since it has not been seen since 1980 despite targeted surveys in Thailand and neighbouring Cambodia. It may possibly still breed in China or Southeast Asia, but a Chinese painting initially thought to depict this species was later reassessed as showing pratincoles.
The adult white-eyed river martin is a medium-sized swallow, with mainly glossy greenish-black plumage, a white rump, and a tail which has two elongated slender central tail feathers, each widening to a racket-shape at the tip. It has a white eye ring and a broad, bright greenish-yellow bill. The sexes are similar in appearance, but the juvenile lacks the tail ornaments and is generally browner than the adult. Little is known of the behaviour or breeding habitat of this martin, although like other swallows it feeds on insects caught in flight, and its wide bill suggests that it may take relatively large species. It roosts in reed beds in winter, and may nest in river sandbanks, probably in April or May before the summer rains. It may have been overlooked prior to its discovery because it tended to feed at dawn or dusk rather than during the day.
Mounted V. mongoliensis cast at Dinosaur Journey Museum
Velociraptor (/vɪˈlɒsɪræptər/; meaning "swift seizer" in Latin) is a genus of dromaeosaurid theropod dinosaur that lived approximately 75 to 71 million years ago during the latter part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils of this species have been discovered in Mongolia. A second species, V. osmolskae, was named in 2008 for skull material from Inner Mongolia, China.
Smaller than other dromaeosaurids like Deinonychus and Achillobator, Velociraptor nevertheless shared many of the same anatomical features. It was a bipedal, feathered carnivore with a long tail and an enlarged sickle-shaped claw on each hindfoot, which is thought to have been used to tackle and disembowel prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.
The European storm petrel, British storm petrel, or just storm petrel (Hydrobates pelagicus) is a seabird in the northern storm petrel family, Hydrobatidae. It is the only member of the genus Hydrobates. The small, square-tailed bird is entirely black except for a broad, white rump and a white band on the under wings, and it has a fluttering, bat-like flight. The large majority of the population breeds on islands off the coasts of Europe, with the greatest numbers in the Faroe Islands, United Kingdom, Ireland, and Iceland. The Mediterranean population is a separate subspecies, but is inseparable at sea from its Atlantic relatives; its strongholds are Filfla Island (Malta), Sicily, and the Balearic Islands.
The storm petrel nests in crevices and burrows, sometimes shared with other seabirds or rabbits, and lays a single white egg, usually on bare soil. The adults share the lengthy incubation and both feed the chick, which is not normally brooded after the first week. This bird is strongly migratory, spending the Northern Hemisphere winter mainly off the coasts of South Africa and Namibia, with some birds stopping in the seas adjoining West Africa, and a few remaining near their Mediterranean breeding islands. This petrel is strictly oceanic outside the breeding season. It feeds on small fish, squid, and zooplankton, while pattering on the sea's surface, and can find oily edible items by smell. The food is converted in the bird's stomach to an oily orange liquid, which is regurgitated when the chick is fed. Although usually silent at sea, the storm petrel has a chattering call given by both members of a pair in their courtship flight, and the male has a purring song given from the breeding chamber.
Tropical Storm Keith was the eleventh Atlantic tropical cyclone of the 1988 Atlantic hurricane season. It struck the Continental United States later in the calendar year than any since the 1925 Atlantic hurricane season. Keith developed out of a tropical wave in the Caribbean Sea on November 17. It tracked northwestward, and under generally favorable conditions, it reached a peak intensity of 70 mph (110 km/h) shortly before striking the northeastern tip of the Yucatán Peninsula. It turned northeastward in the Gulf of Mexico, and made landfall near Sarasota, Florida, on November 23. Keith accelerated its forward motion under the influence of a cold front, and became extratropical near Bermuda on November 24. The extratropical remnant persisted for two more days.
Early in its duration, Keith produced moderate to heavy rainfall in Honduras, Jamaica, and Cuba. Minimal damage was reported in Mexico, which was still recovering from the effects of Hurricane Gilbert two months prior. Keith, the last of four named tropical cyclones to hit the United States during the season, produced moderate rainfall, rough storm surge, and gusty winds across central Florida. Overall damage was fairly minor but widespread, totaling $7.3 million (1988 USD; $15.8 million 2020 USD). Near the coast of Florida, damage occurred mainly from storm surge and beach erosion. Further inland there were floods, downed trees and power lines. No fatalities were reported.
The oceanic whitetip shark (Carcharhinus longimanus), also known as Brown Milbert's sand bar shark, brown shark, lesser white shark, nigano shark, oceanic white-tipped whaler, and silvertip shark, is a large pelagic requiem shark inhabiting tropical and warm temperate seas. Its stocky body is most notable for its long, white-tipped, rounded fins.
Though slow-moving, they are opportunistic and aggressive, and are reputed to be dangerous to shipwreck survivors. Recent studies show steeply declining populations because its large fins are highly valued as the chief ingredient of shark fin soup, and as with other shark species, the whitetip faces mounting fishing pressure throughout its range.
The use of horses in World War I marked a transitional period in the evolution of armed conflict. Cavalry units were initially considered essential offensive elements of a military force, but over the course of the war, the vulnerability of horses to modern weapons such as machine gun, mortar, and artillery fire greatly reduced their utility on the battlefield. This paralleled with the development of tanks, would ultimately replace cavalry in shock tactics role. While the perceived value of the horse in war changed dramatically, horses still played a significant role throughout the war.
All of the major combatants in World War I (1914–1918) began the conflict with cavalry forces. Germany stopped using them on the Western Front soon after the war began, but continued with limited use on the Eastern Front, well into the war. The Ottoman Empire used cavalry extensively during the war. On the Allied side, the United Kingdom used mounted infantry and cavalry charges throughout the war, but the United States used cavalry only briefly. Although not particularly successful on the Western Front, Allied cavalry had some success in the Middle Eastern theatre against a weaker and less technologically-advanced enemy. Russia used cavalry forces on the Eastern Front but with limited success.
Lundomys molitor, also known as Lund's amphibious rat or the greater marsh rat, is a semiaquatic rat species from southeastern South America.
Its distribution is now restricted to Uruguay and nearby Rio Grande do Sul, Brazil, but it previously ranged northward into Minas Gerais, Brazil, and southward into eastern Argentina. The Argentine form may have been distinct from the living form from Brazil and Uruguay. L. molitor is a large rodent, with the head and body length averaging 193 mm (7.6 in), characterized by a long tail, large hindfeet, and long and dense fur. It builds nests above the water, supported by reeds, and it is not currently threatened.
Telopea speciosissima flowerhead with florets opening from the edges towards the centre, Blue Mountains, Australia
Telopea speciosissima, commonly known as the New South Wales waratah or simply waratah, is a large shrub in the plant family Proteaceae. It is endemic to New South Wales in Australia and is the floral emblem of that state. No subspecies are recognised, but the closely related Telopea aspera was only recently classified as a separate species.
T. speciosissima is a shrub to 3 or 4 m (9.8 or 13.1 ft) high and 2 m (6.6 ft) wide, with dark green leaves. Its several stems arise from a pronounced woody base known as a lignotuber. The species is well renowned for its striking large red springtime inflorescences (flowerheads), each including hundreds of individual flowers. These are visited by the eastern pygmy possum (Cercartetus nanus), birds such as honeyeaters (Meliphagidae), and various insects.
Roald Amundsen, Helmer Hanssen, Sverre Hassel and Oscar Wisting (l–r) at "Polheim", the tent erected at the South Pole on 16 December 1911. The top flag is the Flag of Norway; the bottom is marked "Fram". Photograph by Olav Bjaaland.
The first expedition to reach the geographic South Pole was led by the Norwegian explorer Roald Amundsen. He and four others arrived at the pole on 14 December 1911, five weeks ahead of a British party led by Robert Falcon Scott as part of the Terra Nova Expedition. Amundsen and his team returned safely to their base, and later heard that Scott and his four companions had died on their return journey.
Amundsen's initial plans had focused on the Arctic and the conquest of the North Pole by means of an extended drift in an icebound ship. He obtained the use of Fridtjof Nansen's polar exploration ship Fram, and undertook extensive fundraising. Preparations for this expedition were disrupted when, in 1909, the rival American explorers Frederick Cook and Robert E. Peary each claimed to have reached the North Pole. Amundsen then changed his plan and began to prepare for a conquest of the South Pole; uncertain of the extent to which the public and his backers would support him, he kept this revised objective secret. When he set out in June 1910, he led even his crew to believe they were embarking on an Arctic drift, and revealed their true Antarctic destination only when Fram was leaving their last port of call, Madeira.
Selected image
The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble for his discovery of galaxies outside the Milky Way and his creation of Hubble's law, which calculates the rate at which the universe is expanding. Its position outside the Earth's atmosphere allows it to take sharp optical images of very faint objects, and since its launch in 1990, it has become one of the most important instruments in the history of astronomy. It has been responsible for many ground-breaking observations and has helped astronomers achieve a better understanding of many fundamental problems in astrophysics. Hubble's Ultra-Deep Field is the deepest (most sensitive) astronomical optical image ever taken.
Selected biography
Rosalind Elsie Franklin (25 July 1920 - 16 April 1958) was an English chemist and X-ray crystallographer who made critical contributions to the understanding of the fine molecular structures of DNA, RNA, viruses, coal, and graphite. Franklin is best known for her contribution to the discovery of the structure of DNA in 1953, while working at King's College London under the direction of physicist John Randall. By the time the 1962 Nobel Prize for Physiology and Medicine was awarded to Crick, Watson, and her colleague Wilkins, she had been dead for 4 years. She subsequently became an icon in feminist literature.
Did you know...
- ...that in recent years Mediterranean alcoholic beverages (pictured) have been subject of intense scientific study?
- ...that the supermassive black hole at the center of the quasar OJ287 has been measured as weighing 18 billion times the mass of the Sun, six times heavier than the previous record holder?
- ...that the origins of Castle Lake (pictured) in California date to the Pleistocene Era (more than 10,000 years ago) when a glacier carved a basin in the location of the current lake?
- ...that 2002's Hurricane Elida was the first hurricane to be observed by the MERIS sensor aboard the ESA's satellite Envisat?
- ...that for a pure wave motion in fluid dynamics, the Stokes drift velocity is the average velocity when following a specific fluid parcel as it travels with the fluid flow?
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