Portal:Science
Portal:Science
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Science portal
Science is a rigorous, systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the world. Modern science is typically divided into three major branches: the natural sciences (e.g., physics, chemistry, and biology), 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, as they do not rely on empirical evidence. Applied sciences are disciplines that use scientific knowledge for practical purposes, such as in engineering and medicine. (Full article...)
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Ficus rubiginosa, the rusty fig or Port Jackson fig (damun in the Dharug language), is a species of flowering plant native to eastern Australia in the genus Ficus. Beginning as a seedling that grows on other plants (hemiepiphyte) or rocks (lithophyte), F. rubiginosa matures into a tree 30 m (100 ft) high and nearly as wide with a yellow-brown buttressed trunk. The leaves are oval and glossy green and measure from 4 to 19.3 cm (1+1⁄2–7+1⁄2 in) long and 1.25 to 13.2 cm (1⁄2–5+1⁄4 in) wide.
The fruits are small, round, and yellow, and can ripen and turn red at any time of year, peaking in spring and summer. Like all figs, the fruit is in the form of a syconium, an inverted inflorescence with the flowers lining an internal cavity. F. rubiginosa is exclusively pollinated by the fig wasp species Pleistodontes imperialis, which may comprise four cryptospecies. The syconia are also home to another fourteen species of wasp, some of which induce galls while others parasitise the pollinator wasps and at least two species of nematode. Many species of bird, including pigeons, parrots, and various passerines, eat the fruit. Ranging along the Australian east coast from Queensland to Bega in southern New South Wales (including the Port Jackson area, leading to its alternative name), F. rubiginosa grows in rainforest margins and rocky outcrops. It is used as a shade tree in parks and public spaces, and when potted is well-suited for use as an indoor plant or in bonsai. (Full article...) - Image 2
The Mono–Inyo Craters are a volcanic chain of craters, domes and lava flows in Mono County, Eastern California. The chain stretches 25 miles (40 km) from the northwest shore of Mono Lake to the south of Mammoth Mountain. The Mono Lake Volcanic Field forms the northernmost part of the chain and consists of two volcanic islands in the lake and one cinder cone volcano on its northwest shore. Most of the Mono Craters, which make up the bulk of the northern part of the Mono–Inyo chain, are phreatic (steam explosion) volcanoes that have since been either plugged or over-topped by rhyolite domes and lava flows. The Inyo volcanic chain form much of the southern part of the chain and consist of phreatic explosion pits, and rhyolitic lava flows and domes. The southernmost part of the chain consists of fumaroles and explosion pits on Mammoth Mountain and a set of cinder cones south of the mountain; the latter are called the Red Cones.
Eruptions along the narrow fissure system under the chain began in the west moat of Long Valley Caldera 400,000 to 60,000 years ago. Mammoth Mountain was formed during this period. Multiple eruptions from 40,000 to 600 years ago created the Mono Craters and eruptions 5,000 to 500 years ago formed the Inyo volcanic chain. Lava flows 5,000 years ago built the Red Cones, and explosion pits on Mammoth Mountain were excavated in the last 1,000 years. Uplift of Paoha Island in Mono Lake about 250 years ago is the most recent activity. These eruptions most likely originated from small magma bodies rather than from a single, large magma chamber like the one that produced the massive Long Valley Caldera eruption 760,000 years ago. During the past 3,000 years, eruptions have occurred every 250 to 700 years. In 1980, a series of earthquakes and uplift within and south of Long Valley Caldera indicated renewed activity in the area. (Full article...) - Image 3
A cockatoo is any of the 21 species of parrots belonging to the family Cacatuidae, the only family in the superfamily Cacatuoidea. Along with the Psittacoidea (true parrots) and the Strigopoidea (large New Zealand parrots), they make up the order Psittaciformes. The family has a mainly Australasian distribution, ranging from the Philippines and the eastern Indonesian islands of Wallacea to New Guinea, the Solomon Islands and Australia.
Cockatoos are recognisable by the prominent crests and curved bills. Their plumage is generally less colourful than that of other parrots, being mainly white, grey or black and often with coloured features in the crest, cheeks or tail. On average they are larger than other parrots; however, the cockatiel, the smallest cockatoo species, is a small bird. The phylogenetic position of the cockatiel remains unresolved, except that it is one of the earliest offshoots of the cockatoo lineage. The remaining species are in two main clades. The five large black-coloured cockatoos of the genus Calyptorhynchus form one branch. The second and larger branch is formed by the genus Cacatua, comprising 11 species of white-plumaged cockatoos and four monotypic genera that branched off earlier; namely the pink and white pink cockatoo, the pink and grey galah, the mainly grey gang-gang cockatoo and the large black-plumaged palm cockatoo. (Full article...) - Image 4
The Beulé Gate (French pronunciation: [bœ'le]) is a fortified gate, constructed in the Roman period, leading to the Propylaia of the Acropolis of Athens. It was constructed almost entirely from repurposed materials (spolia) taken from the Choragic Monument of Nikias, a monument built in the fourth century BCE and demolished between the second and fourth centuries CE. The dedicatory inscription from Nikias's monument is still visible in the entablature of the Beulé Gate.
The gate was integrated into the Post-Herulian Wall, a late Roman fortification built around the Acropolis in the years following the city's sack by the Germanic Heruli people in 267 or early 268 CE. Its construction marked the beginning of a new phase in the Acropolis's use, in which it came to be seen more as a potential defensive position than in the religious terms that had marked its use in the classical period. During the medieval period, the gate was further fortified and closed off, before being built over with a bastion in Ottoman times. (Full article...) - Image 5Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest element and, at standard conditions, is a gas of diatomic molecules with the formula H2, sometimes called dihydrogen, but more commonly called hydrogen gas, molecular hydrogen or simply hydrogen. It is colorless, odorless, tasteless, non-toxic, and highly combustible. Constituting approximately 75% of all normal matter, hydrogen is the most abundant chemical substance in the universe. Stars, including the Sun, primarily consist of hydrogen in a plasma state, while on Earth, hydrogen is found in water, organic compounds, and other molecular forms. The most common isotope of hydrogen (symbol 1H) consists of one proton, one electron, and no neutrons.
In the early universe, the formation of hydrogen's protons occurred during the first second following the Big Bang, with neutral hydrogen atoms only forming approximately 370,000 years later during the recombination epoch as the universe cooled and plasma had cooled enough for electrons to remain bound to protons. Hydrogen, typically nonmetallic except under extreme pressures, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid-base reactions, which predominantly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively charged anion, where it is known as hydride, or as a positively charged cation denoted by the symbol H+. The cation, simply a proton (symbol p), exhibits specific behavior in aqueous solutions and in ionic compounds involves screening of its electric charge by surrounding polar molecules or anions. Hydrogen's unique position as the only neutral atom for which the Schrödinger equation can be directly solved has significantly contributed to the foundational principles of quantum mechanics through the exploration of its energetics and chemical bonding. (Full article...) - Image 6
Smilodon is a genus of felids belonging to the extinct subfamily Machairodontinae. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch (2.5 mya – 10,000 years ago). The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of specimens obtained from the La Brea Tar Pits in Los Angeles constitute the largest collection of Smilodon fossils.
Overall, Smilodon was more robustly built than any extant cat, with particularly well-developed forelimbs and exceptionally long upper canine teeth. Its jaw had a bigger gape than that of modern cats, and its upper canines were slender and fragile, being adapted for precision killing. S. gracilis was the smallest species at 55 to 100 kg (120 to 220 lb) in weight. S. fatalis had a weight of 160 to 280 kg (350 to 620 lb) and height of 100 cm (39 in). Both of these species are mainly known from North America, but remains from South America have also been attributed to them. S. populator from South America was the largest species, at 220 to 436 kg (485 to 961 lb) in weight and 120 cm (47 in) in height, and was among the largest known felids. The coat pattern of Smilodon is unknown, but it has been artistically restored with plain or spotted patterns. (Full article...) - Image 7(mostly astrological) (Full article...)
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Caloboletus calopus, commonly known as the bitter bolete, bitter beech bolete or scarlet-stemmed bolete, is a fungus of the bolete family, found in Asia, Northern Europe and North America. Appearing in coniferous and deciduous woodland in summer and autumn, the stout fruit bodies are attractively coloured, with a beige to olive cap up to 15 cm (6 in) across, yellow pores, and a reddish stipe up to 15 cm (6 in) long and 5 cm (2 in) wide. The pale yellow flesh stains blue when broken or bruised.
Christiaan Persoon first described Boletus calopus in 1801. Modern molecular phylogenetics showed that it was only distantly related to the type species of Boletus and required placement in a new genus; Caloboletus was erected in 2014, with C. calopus designated as the type species. Although Caloboletus calopus is not typically considered edible due to an intensely bitter taste that does not disappear with cooking, there are reports of it being consumed in eastern Europe. Its red stipe distinguishes it from edible species, such as Boletus edulis. (Full article...) - Image 9
Suillus bovinus, also known as the Jersey cow mushroom or bovine bolete, is a pored mushroom of the genus Suillus in the family Suillaceae. A common fungus native to Europe and Asia, it has been introduced to North America and Australia. It was initially described as Boletus bovinus by Carl Linnaeus in 1753, and given its current binomial name by Henri François Anne de Roussel in 1806. It is an edible mushroom, though not highly regarded.
The fungus grows in coniferous forests in its native range, and pine plantations in countries where it has become naturalised. It forms symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue, and is sometimes parasitised by the related mushroom Gomphidius roseus. Suillus bovinus produces spore-bearing fruit bodies, often in large numbers, above ground. The mushroom has a convex grey-yellow or ochre cap reaching up to 10 cm (4 in) in diameter, which flattens with age. Like other boletes, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores. The pore surface is yellow. The stipe, more slender than those of other Suillus boletes, lacks a ring. (Full article...) - Image 10Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. Ursa Minor was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the north pole star.
Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging in apparent magnitude from 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. Kochab and 3rd-magnitude Gamma Ursae Minoris have been called the "guardians of the pole star" or "Guardians of The Pole". Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star—Calvera—and H1504+65, the hottest white dwarf yet discovered, with a surface temperature of 200,000 K. (Full article...) - Image 11
The rufous-crowned sparrow (Aimophila ruficeps) is a small American sparrow. This passerine is primarily found across the Southwestern United States and much of the interior of Mexico, south to the transverse mountain range, and to the Pacific coast to the southwest of the transverse range. Its distribution is patchy, with populations often being isolated from each other. Twelve subspecies are generally recognized, though up to eighteen have been suggested. This bird has a brown back with darker streaks and gray underparts. The crown is rufous, and the face and supercilium are gray with a brown or rufous streak extending from each eye and a thick black malar streak.
These sparrows feed primarily on seeds in the winter and insects in the spring and summer. The birds are often territorial, with males guarding their territory through song and displays. Flight is awkward for this species, which prefers to hop along the ground for locomotion. They are monogamous and breed during spring. Two to five eggs are laid in the bird's nest, which is cup-shaped and well hidden. Adult sparrows are preyed upon by house cats and small raptors, while young may be taken by a range of mammals and reptiles. They have been known to live for up to three years, two months. Although the species has been classified as least concern, or unthreatened with extinction, some subspecies are threatened by habitat destruction and one may be extinct. (Full article...) - Image 12
The American goldfinch (Spinus tristis) is a small North American bird in the finch family. It is migratory, ranging from mid-Alberta to North Carolina during the breeding season, and from just south of the Canada–United States border to Mexico during the winter.
The only finch in its subfamily to undergo a complete molt, the American goldfinch displays sexual dichromatism: the male is a vibrant yellow in the summer and an olive color during the winter, while the female is a dull yellow-brown shade which brightens only slightly during the summer. The male displays brightly colored plumage during the breeding season to attract a mate. (Full article...) - Image 13
Miniopterus aelleni is a bat in the genus Miniopterus that occurs on Anjouan in the Comoros and in northern and western Madagascar.
It is a small brown bat; its forearm length is 35 to 41 mm (1.4 to 1.6 in). The long tragus (a projection in the outer ear) has a broad base and a blunt or rounded tip. The uropatagium (tail membrane) is sparsely haired. The palate is flat, and there are distinct diastemata (gaps) between the upper canines and premolars. (Full article...) - Image 14
The raccoon (/rəˈkuːn/ or US: /ræˈkuːn/ ⓘ, Procyon lotor), also spelled racoon and sometimes called the common raccoon to distinguish it from the other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of 40 to 70 cm (16 to 28 in), and a body weight of 5 to 26 kg (11 to 57 lb). Its grayish coat mostly consists of dense underfur, which insulates it against cold weather. The animal's most distinctive features include its extremely dexterous front paws, its facial mask, and its ringed tail, which are common themes in the mythologies of the Indigenous peoples of the Americas surrounding the species. The raccoon is noted for its intelligence, as studies show that it is able to remember the solution to tasks for at least three years. It is usually nocturnal and omnivorous, eating about 40% invertebrates, 33% plants, and 27% vertebrates.
The original habitats of the raccoon are deciduous and mixed forests, but due to their adaptability, they have extended their range to mountainous areas, coastal marshes, and urban areas, where some homeowners consider them to be pests. As a result of escapes and deliberate introductions in the mid-20th century, raccoons are now also distributed across central Europe, the Caucasus, and Japan. (Full article...) - Image 15
The thylacine (/ˈθaɪləsiːn/; binomial name Thylacinus cynocephalus), also commonly known as the Tasmanian tiger or Tasmanian wolf, is an extinct carnivorous marsupial that was native to the Australian mainland and the islands of Tasmania and New Guinea. The thylacine died out in New Guinea and mainland Australia around 3,600–3,200 years ago, prior to the arrival of Europeans, possibly because of the introduction of the dingo, whose earliest record dates to around the same time, but which never reached Tasmania. Prior to European settlement, around 5,000 remained in the wild on Tasmania. Beginning in the nineteenth century, they were perceived as a threat to the livestock of farmers and bounty hunting was introduced. The last known of its species died in 1936 at Hobart Zoo in Tasmania. The thylacine is widespread in popular culture and is a cultural icon in Australia.
The thylacine was known as the Tasmanian tiger because of the dark transverse stripes that radiated from the top of its back, and it was called the Tasmanian wolf because it resembled a medium- to large-sized canid. The name thylacine is derived from thýlakos meaning "pouch" and ine meaning "pertaining to", and refers to the marsupial pouch. Both sexes had a pouch. The females used theirs for rearing young, and the males used theirs as a protective sheath, covering the external reproductive organs. The animal had a stiff tail and could open its jaws to an unusual extent. Recent studies and anecdotal evidence on its predatory behaviour suggest that the thylacine was a solitary ambush predator specialised in hunting small to medium-sized prey. Accounts suggest that in the wild, it fed on small birds and mammals. It was the only member of the genus Thylacinus and family Thylacinidae to have survived until modern times. Its closest living relatives are the other members of Dasyuromorphia including the Tasmanian devil, from which it is estimated to have split 42–36 million years ago. (Full article...)
Featured pictures
- Image 1Archaeological excavation at Atapuerca Mountains, by Mario modesto (from Wikipedia:Featured pictures/Sciences/Others)
- Image 2Global oceanic and terrestrial photoautotroph abundance at Primary production, by SeaWiFS Project (from Wikipedia:Featured pictures/Sciences/Others)
- Image 3Drop impact on a liquid surface, by José Manuel Suárez (from Wikipedia:Featured pictures/Sciences/Others)
- Image 5Toroid magnets of the ATLAS detector, by Maximilien Brice, CERN (edited by Bammesk) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 7Oblique shock, by NASA/United States Air Force (from Wikipedia:Featured pictures/Sciences/Others)
- Image 8Section of the Large Hadron Collider, by Maximilien Brice (from Wikipedia:Featured pictures/Sciences/Others)
- Image 9NASA study on wingtip vortices at Wake turbulence, by Langley Research Center (edited by Fir0002) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 11Archaeologists prospecting Santa Ana Cave at Excavation (archaeology), by Mario modesto (from Wikipedia:Featured pictures/Sciences/Others)
- Image 14Color cathodoluminescence of a diamond, by Pavel.Somov (from Wikipedia:Featured pictures/Sciences/Others)
- Image 15Nobel Prize in Physics diploma, by Sofia Gisberg (restored by Jebulon) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 16Simulation of liquids with different viscosities, by Synapticrelay (from Wikipedia:Featured pictures/Sciences/Others)
- Image 17Hypervelocity impact demonstration, by NASA (from Wikipedia:Featured pictures/Sciences/Others)
- Image 18Total internal reflection, by Jean-Marc Kuffer (from Wikipedia:Featured pictures/Sciences/Others)
- Image 19Peruvian Andes at United States Exploring Expedition, by Alfred Thomas Agate (edited by Durova) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 20Parallax, by Mila Zinkova (edited by Richard Bartz) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 21Mechanical advantage device, by Prolineserver (edited by Tomia, Ss181292 and Atropos235) (from Wikipedia:Featured pictures/Sciences/Others)
- Image 22Diet Coke and Mentos eruption, by Mikemurphy (from Wikipedia:Featured pictures/Sciences/Others)
- Image 24Ice core, by the Greenland Ice Sheet Project (from Wikipedia:Featured pictures/Sciences/Others)
- Image 25Translational motion at Thermodynamic temperature, by Greg L (from Wikipedia:Featured pictures/Sciences/Others)
- Image 26Vibrating glass beam at Euler–Bernoulli beam theory, by Ben pcc (from Wikipedia:Featured pictures/Sciences/Others)
- Image 27Projectile motion of a bouncing ball at Inelastic collision, by MichaelMaggs (from Wikipedia:Featured pictures/Sciences/Others)
- Image 28Lorentz transformation of world line, by Cyp (from Wikipedia:Featured pictures/Sciences/Others)
- Image 35Animation of a water drop, by Chris 73 and Gmaxwell (from Wikipedia:Featured pictures/Sciences/Others)
Vital articles
Did you know...
- ... that the first Black woman to receive tenure in Kent State University's College of Arts & Sciences, Angela Neal-Barnett, emphasizes social support between Black women as "an indigenous form of healing"?
- ... that according to science fiction essayist Jacques Van Herp, the novella The End of Illa caused the temporary decline of French science fiction?
- ... that Cowbridge Girls School, built in 1896, was unusual for its time in providing a science laboratory for the students?
- ... that Brian Stableford blamed the cancellation of the follow-up to his 2006 book Science Fact and Science Fiction: An Encyclopedia on the availability of information online?
- ... that the Royal Albert Hall has called the 1891 Vril-Ya Bazaar and Fete the world's first science fiction convention?
- ... that Godwin Obasi has been described as "Africa's gift to the world of climate science"?
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Science News
- 12 March 2024 –
- A scientific expedition to the Bounty Trough off the coast of New Zealand reports the discovery of more than one hundred new species. (The New York Times)
- 28 February 2024 –
- The Canadian government releases its report into the high-profile firings of two scientists from the National Microbiology Laboratory in Winnipeg, Manitoba, in 2021, stating that the pair worked closely and covertly with the Chinese government. (National Post)
- 20 February 2024 –
- Astronomers identify the most luminous object ever observed, QSO J0529-4351, a quasar that accretes around one solar mass per day. (The Guardian) (Nature.com)
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Top 10 WikiProject Science Popular articles of the month - load new batch
- Image 1Artificial intelligence (AI), in its broadest sense, is intelligence exhibited by machines, particularly computer systems, as opposed to the natural intelligence of living beings. It is a field of research in computer science that develops and studies methods and software which enable machines to perceive their environment and uses learning and intelligence to take actions that maximize their chances of achieving defined goals. Such machines may be called AIs. (Full article...)
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Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being a water world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation. (Full article...) - Image 3
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other scholarly literature, including court opinions and patents. (Full article...) - Image 4Sci-Hub is a shadow library website that provides free access to millions of research papers, regardless of copyright, by bypassing publishers' paywalls in various ways. Unlike Library Genesis, it does not provide access to books. Sci-Hub was founded in Kazakhstan by Alexandra Elbakyan in 2011, in response to the high cost of research papers behind paywalls (see Serials crisis). The site is extensively used worldwide. In September 2019, the site's operator(s) said that it served approximately 400,000 requests per day.
In addition to its intensive use, Sci-Hub stands out among other shadow libraries because of its easy use/reliability and because of the enormous size of its collection: a 2018 study estimated that Sci-Hub provided access to 95% of all scholarly publications with issued DOI numbers, and on 15 July 2022 Sci-Hub reported that its collection comprises 88,343,822 files. (Full article...) - Image 5
In statistics, the standard deviation is a measure of the amount of variation of a random variable expected about its mean. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range. The standard deviation is commonly used in the determination of what constitutes an outlier and what does not. (Full article...) - Image 6Science is a rigorous, systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the world. Modern science is typically divided into three major branches: the natural sciences (e.g., physics, chemistry, and biology), 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, as they do not rely on empirical evidence. Applied sciences are disciplines that use scientific knowledge for practical purposes, such as in engineering and medicine. (Full article...)
- Image 7Ejaculation is the discharge of semen (the ejaculate; normally containing sperm) from the male reproductive tract. It is normally linked with orgasm, which involves involuntary contractions of the pelvic floor. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. Ejaculation can occur spontaneously during sleep, and is a normal part of human sexual development (a nocturnal emission or "wet dream"). In rare cases, ejaculation occurs because of prostatic disease. Anejaculation is the condition of being unable to ejaculate. Ejaculation is normally intensely pleasurable for men; dysejaculation is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the condition where semen travels backwards into the bladder rather than out of the urethra. (Full article...)
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The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and science. (Full article...) - Image 9
In physics, gravity (from Latin gravitas 'weight') is a fundamental interaction which causes mutual attraction between all things that have mass. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a result, it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light. (Full article...) - Image 10
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. (Full article...)