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[SOURCE: https://en.wikipedia.org/wiki/Animal#cite_note-Kapli_2020-114] | [TOKENS: 6011] |
Contents Animal Animals are multicellular, eukaryotic organisms belonging to the biological kingdom Animalia (/ˌænɪˈmeɪliə/). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million living animal species have been described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complex ecologies and interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology, and the study of animal behaviour is known as ethology. The animal kingdom is divided into five major clades, namely Porifera, Ctenophora, Placozoa, Cnidaria and Bilateria. Most living animal species belong to the clade Bilateria, a highly proliferative clade whose members have a bilaterally symmetric and significantly cephalised body plan, and the vast majority of bilaterians belong to two large clades: the protostomes, which includes organisms such as arthropods, molluscs, flatworms, annelids and nematodes; and the deuterostomes, which include echinoderms, hemichordates and chordates, the latter of which contains the vertebrates. The much smaller basal phylum Xenacoelomorpha have an uncertain position within Bilateria. Animals first appeared in the fossil record in the late Cryogenian period and diversified in the subsequent Ediacaran period in what is known as the Avalon explosion. Nearly all modern animal phyla first appeared in the fossil record as marine species during the Cambrian explosion, which began around 539 million years ago (Mya), and most classes during the Ordovician radiation 485.4 Mya. Common to all living animals, 6,331 groups of genes have been identified that may have arisen from a single common ancestor that lived about 650 Mya during the Cryogenian period. Historically, Aristotle divided animals into those with blood and those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between taxa. Humans make use of many other animal species for food (including meat, eggs, and dairy products), for materials (such as leather, fur, and wool), as pets and as working animals for transportation, and services. Dogs, the first domesticated animal, have been used in hunting, in security and in warfare, as have horses, pigeons and birds of prey; while other terrestrial and aquatic animals are hunted for sports, trophies or profits. Non-human animals are also an important cultural element of human evolution, having appeared in cave arts and totems since the earliest times, and are frequently featured in mythology, religion, arts, literature, heraldry, politics, and sports. Etymology The word animal comes from the Latin noun animal of the same meaning, which is itself derived from Latin animalis 'having breath or soul'. The biological definition includes all members of the kingdom Animalia. In colloquial usage, the term animal is often used to refer only to nonhuman animals. The term metazoa is derived from Ancient Greek μετα meta 'after' (in biology, the prefix meta- stands for 'later') and ζῷᾰ zōia 'animals', plural of ζῷον zōion 'animal'. A metazoan is any member of the group Metazoa. Characteristics Animals have several characteristics that they share with other living things. Animals are eukaryotic, multicellular, and aerobic, as are plants and fungi. Unlike plants and algae, which produce their own food, animals cannot produce their own food, a feature they share with fungi. Animals ingest organic material and digest it internally. Animals have structural characteristics that set them apart from all other living things: Typically, there is an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians). Animal development is controlled by Hox genes, which signal the times and places to develop structures such as body segments and limbs. During development, the animal extracellular matrix forms a relatively flexible framework upon which cells can move about and be reorganised into specialised tissues and organs, making the formation of complex structures possible, and allowing cells to be differentiated. The extracellular matrix may be calcified, forming structures such as shells, bones, and spicules. In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi) are held in place by cell walls, and so develop by progressive growth. Nearly all animals make use of some form of sexual reproduction. They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm, also develops between them. These germ layers then differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction generally leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. This may take place through fragmentation; budding, such as in Hydra and other cnidarians; or parthenogenesis, where fertile eggs are produced without mating, such as in aphids. Ecology Animals are categorised into ecological groups depending on their trophic levels and how they consume organic material. Such groupings include carnivores (further divided into subcategories such as piscivores, insectivores, ovivores, etc.), herbivores (subcategorised into folivores, graminivores, frugivores, granivores, nectarivores, algivores, etc.), omnivores, fungivores, scavengers/detritivores, and parasites. Interactions between animals of each biome form complex food webs within that ecosystem. In carnivorous or omnivorous species, predation is a consumer–resource interaction where the predator feeds on another organism, its prey, who often evolves anti-predator adaptations to avoid being fed upon. Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various antagonistic/competitive coevolutions. Almost all multicellular predators are animals. Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Other animals may have very specific feeding behaviours, such as hawksbill sea turtles which mainly eat sponges. Most animals rely on biomass and bioenergy produced by plants and phytoplanktons (collectively called producers) through photosynthesis. Herbivores, as primary consumers, eat the plant material directly to digest and absorb the nutrients, while carnivores and other animals on higher trophic levels indirectly acquire the nutrients by eating the herbivores or other animals that have eaten the herbivores. Animals oxidise carbohydrates, lipids, proteins and other biomolecules in cellular respiration, which allows the animal to grow and to sustain basal metabolism and fuel other biological processes such as locomotion. Some benthic animals living close to hydrothermal vents and cold seeps on the dark sea floor consume organic matter produced through chemosynthesis (via oxidising inorganic compounds such as hydrogen sulfide) by archaea and bacteria. Animals originated in the ocean; all extant animal phyla, except for Micrognathozoa and Onychophora, feature at least some marine species. However, several lineages of arthropods begun to colonise land around the same time as land plants, probably between 510 and 471 million years ago, during the Late Cambrian or Early Ordovician. Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Other notable animal groups that colonized land environments are Mollusca, Platyhelmintha, Annelida, Tardigrada, Onychophora, Rotifera, Nematoda. Animals occupy virtually all of earth's habitats and microhabitats, with faunas adapted to salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of other organisms. Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F) or in the most extreme cold deserts of continental Antarctica. The collective global geomorphic influence of animals on the processes shaping the Earth's surface remains largely understudied, with most studies limited to individual species and well-known exemplars. Diversity The blue whale (Balaenoptera musculus) is the largest animal that has ever lived, weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long. The largest extant terrestrial animal is the African bush elephant (Loxodonta africana), weighing up to 12.25 tonnes and measuring up to 10.67 metres (35.0 ft) long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as Argentinosaurus, which may have weighed as much as 73 tonnes, and Supersaurus which may have reached 39 metres. Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 μm, and one of the smallest species (Myxobolus shekel) is no more than 8.5 μm when fully grown. The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[a] 3,000–6,500 4,000–25,000 Evolutionary origin Evidence of animals is found as long ago as the Cryogenian period. 24-Isopropylcholestane (24-ipc) has been found in rocks from roughly 650 million years ago; it is only produced by sponges and pelagophyte algae. Its likely origin is from sponges based on molecular clock estimates for the origin of 24-ipc production in both groups. Analyses of pelagophyte algae consistently recover a Phanerozoic origin, while analyses of sponges recover a Neoproterozoic origin, consistent with the appearance of 24-ipc in the fossil record. The first body fossils of animals appear in the Ediacaran, represented by forms such as Charnia and Spriggina. It had long been doubted whether these fossils truly represented animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes their nature. Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration, but as they became specialised for aerobic metabolism they became fully dependent on oxygen in their environments. Many animal phyla first appear in the fossil record during the Cambrian explosion, starting about 539 million years ago, in beds such as the Burgess Shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as the predatory Anomalocaris. The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that all these animals appeared simultaneously. That view is supported by the discovery of Auroralumina attenboroughii, the earliest known Ediacaran crown-group cnidarian (557–562 mya, some 20 million years before the Cambrian explosion) from Charnwood Forest, England. It is thought to be one of the earliest predators, catching small prey with its nematocysts as modern cnidarians do. Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Early fossils that might represent animals appear for example in the 665-million-year-old rocks of the Trezona Formation of South Australia. These fossils are interpreted as most probably being early sponges. Trace fossils such as tracks and burrows found in the Tonian period (from 1 gya) may indicate the presence of triploblastic worm-like animals, roughly as large (about 5 mm wide) and complex as earthworms. However, similar tracks are produced by the giant single-celled protist Gromia sphaerica, so the Tonian trace fossils may not indicate early animal evolution. Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals. Objects such as sediment-filled tubes that resemble trace fossils of the burrows of wormlike animals have been found in 1.2 gya rocks in North America, in 1.5 gya rocks in Australia and North America, and in 1.7 gya rocks in Australia. Their interpretation as having an animal origin is disputed, as they might be water-escape or other structures. Phylogeny Animals are monophyletic, meaning they are derived from a common ancestor. Animals are the sister group to the choanoflagellates, with which they form the Choanozoa. Ros-Rocher and colleagues (2021) trace the origins of animals to unicellular ancestors, providing the external phylogeny shown in the cladogram. Uncertainty of relationships is indicated with dashed lines. The animal clade had certainly originated by 650 mya, and may have come into being as much as 800 mya, based on molecular clock evidence for different phyla. Holomycota (inc. fungi) Ichthyosporea Pluriformea Filasterea The relationships at the base of the animal tree have been debated. Other than Ctenophora, the Bilateria and Cnidaria are the only groups with symmetry, and other evidence shows they are closely related. In addition to sponges, Placozoa has no symmetry and was often considered a "missing link" between protists and multicellular animals. The presence of hox genes in Placozoa shows that they were once more complex. The Porifera (sponges) have long been assumed to be sister to the rest of the animals, but there is evidence that the Ctenophora may be in that position. Molecular phylogenetics has supported both the sponge-sister and ctenophore-sister hypotheses. In 2017, Roberto Feuda and colleagues, using amino acid differences, presented both, with the following cladogram for the sponge-sister view that they supported (their ctenophore-sister tree simply interchanging the places of ctenophores and sponges): Porifera Ctenophora Placozoa Cnidaria Bilateria Conversely, a 2023 study by Darrin Schultz and colleagues uses ancient gene linkages to construct the following ctenophore-sister phylogeny: Ctenophora Porifera Placozoa Cnidaria Bilateria Sponges are physically very distinct from other animals, and were long thought to have diverged first, representing the oldest animal phylum and forming a sister clade to all other animals. Despite their morphological dissimilarity with all other animals, genetic evidence suggests sponges may be more closely related to other animals than the comb jellies are. Sponges lack the complex organisation found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues, unlike all other animals. They typically feed by drawing in water through pores, filtering out small particles of food. The Ctenophora and Cnidaria are radially symmetric and have digestive chambers with a single opening, which serves as both mouth and anus. Animals in both phyla have distinct tissues, but these are not organised into discrete organs. They are diploblastic, having only two main germ layers, ectoderm and endoderm. The tiny placozoans have no permanent digestive chamber and no symmetry; they superficially resemble amoebae. Their phylogeny is poorly defined, and under active research. The remaining animals, the great majority—comprising some 29 phyla and over a million species—form the Bilateria clade, which have a bilaterally symmetric body plan. The Bilateria are triploblastic, with three well-developed germ layers, and their tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and in the Nephrozoa there is an internal body cavity, a coelom or pseudocoelom. These animals have a head end (anterior) and a tail end (posterior), a back (dorsal) surface and a belly (ventral) surface, and a left and a right side. A modern consensus phylogenetic tree for the Bilateria is shown below. Xenacoelomorpha Ambulacraria Chordata Ecdysozoa Spiralia Having a front end means that this part of the body encounters stimuli, such as food, favouring cephalisation, the development of a head with sense organs and a mouth. Many bilaterians have a combination of circular muscles that constrict the body, making it longer, and an opposing set of longitudinal muscles, that shorten the body; these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis. They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, over evolutionary time, descendant spaces have evolved which have lost one or more of each of these characteristics. For example, adult echinoderms are radially symmetric (unlike their larvae), while some parasitic worms have extremely simplified body structures. Genetic studies have considerably changed zoologists' understanding of the relationships within the Bilateria. Most appear to belong to two major lineages, the protostomes and the deuterostomes. It is often suggested that the basalmost bilaterians are the Xenacoelomorpha, with all other bilaterians belonging to the subclade Nephrozoa. However, this suggestion has been contested, with other studies finding that xenacoelomorphs are more closely related to Ambulacraria than to other bilaterians. Protostomes and deuterostomes differ in several ways. Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes (the Spiralia) undergo spiral cleavage. Animals from both groups possess a complete digestive tract, but in protostomes the first opening of the embryonic gut develops into the mouth, and the anus forms secondarily. In deuterostomes, the anus forms first while the mouth develops secondarily. Most protostomes have schizocoelous development, where cells simply fill in the interior of the gastrula to form the mesoderm. In deuterostomes, the mesoderm forms by enterocoelic pouching, through invagination of the endoderm. The main deuterostome taxa are the Ambulacraria and the Chordata. Ambulacraria are exclusively marine and include acorn worms, starfish, sea urchins, and sea cucumbers. The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. The protostomes include the Ecdysozoa, named after their shared trait of ecdysis, growth by moulting, Among the largest ecdysozoan phyla are the arthropods and the nematodes. The rest of the protostomes are in the Spiralia, named for their pattern of developing by spiral cleavage in the early embryo. Major spiralian phyla include the annelids and molluscs. History of classification In the classical era, Aristotle divided animals,[d] based on his own observations, into those with blood (roughly, the vertebrates) and those without. The animals were then arranged on a scale from man (with blood, two legs, rational soul) down through the live-bearing tetrapods (with blood, four legs, sensitive soul) and other groups such as crustaceans (no blood, many legs, sensitive soul) down to spontaneously generating creatures like sponges (no blood, no legs, vegetable soul). Aristotle was uncertain whether sponges were animals, which in his system ought to have sensation, appetite, and locomotion, or plants, which did not: he knew that sponges could sense touch and would contract if about to be pulled off their rocks, but that they were rooted like plants and never moved about. In 1758, Carl Linnaeus created the first hierarchical classification in his Systema Naturae. In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then, the last four have all been subsumed into a single phylum, the Chordata, while his Insecta (which included the crustaceans and arachnids) and Vermes have been renamed or broken up. The process was begun in 1793 by Jean-Baptiste de Lamarck, who called the Vermes une espèce de chaos ('a chaotic mess')[e] and split the group into three new phyla: worms, echinoderms, and polyps (which contained corals and jellyfish). By 1809, in his Philosophie Zoologique, Lamarck had created nine phyla apart from vertebrates (where he still had four phyla: mammals, birds, reptiles, and fish) and molluscs, namely cirripedes, annelids, crustaceans, arachnids, insects, worms, radiates, polyps, and infusorians. In his 1817 Le Règne Animal, Georges Cuvier used comparative anatomy to group the animals into four embranchements ('branches' with different body plans, roughly corresponding to phyla), namely vertebrates, molluscs, articulated animals (arthropods and annelids), and zoophytes (radiata) (echinoderms, cnidaria and other forms). This division into four was followed by the embryologist Karl Ernst von Baer in 1828, the zoologist Louis Agassiz in 1857, and the comparative anatomist Richard Owen in 1860. In 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms: Metazoa (multicellular animals, with five phyla: coelenterates, echinoderms, articulates, molluscs, and vertebrates) and Protozoa (single-celled animals), including a sixth animal phylum, sponges. The protozoa were later moved to the former kingdom Protista, leaving only the Metazoa as a synonym of Animalia. In human culture The human population exploits a large number of other animal species for food, both of domesticated livestock species in animal husbandry and, mainly at sea, by hunting wild species. Marine fish of many species are caught commercially for food. A smaller number of species are farmed commercially. Humans and their livestock make up more than 90% of the biomass of all terrestrial vertebrates, and almost as much as all insects combined. Invertebrates including cephalopods, crustaceans, insects—principally bees and silkworms—and bivalve or gastropod molluscs are hunted or farmed for food, fibres. Chickens, cattle, sheep, pigs, and other animals are raised as livestock for meat across the world. Animal fibres such as wool and silk are used to make textiles, while animal sinews have been used as lashings and bindings, and leather is widely used to make shoes and other items. Animals have been hunted and farmed for their fur to make items such as coats and hats. Dyestuffs including carmine (cochineal), shellac, and kermes have been made from the bodies of insects. Working animals including cattle and horses have been used for work and transport from the first days of agriculture. Animals such as the fruit fly Drosophila melanogaster serve a major role in science as experimental models. Animals have been used to create vaccines since their discovery in the 18th century. Some medicines such as the cancer drug trabectedin are based on toxins or other molecules of animal origin. People have used hunting dogs to help chase down and retrieve animals, and birds of prey to catch birds and mammals, while tethered cormorants have been used to catch fish. Poison dart frogs have been used to poison the tips of blowpipe darts. A wide variety of animals are kept as pets, from invertebrates such as tarantulas, octopuses, and praying mantises, reptiles such as snakes and chameleons, and birds including canaries, parakeets, and parrots all finding a place. However, the most kept pet species are mammals, namely dogs, cats, and rabbits. There is a tension between the role of animals as companions to humans, and their existence as individuals with rights of their own. A wide variety of terrestrial and aquatic animals are hunted for sport. The signs of the Western and Chinese zodiacs are based on animals. In China and Japan, the butterfly has been seen as the personification of a person's soul, and in classical representation the butterfly is also the symbol of the soul. Animals have been the subjects of art from the earliest times, both historical, as in ancient Egypt, and prehistoric, as in the cave paintings at Lascaux. Major animal paintings include Albrecht Dürer's 1515 The Rhinoceros, and George Stubbs's c. 1762 horse portrait Whistlejacket. Insects, birds and mammals play roles in literature and film, such as in giant bug movies. Animals including insects and mammals feature in mythology and religion. The scarab beetle was sacred in ancient Egypt, and the cow is sacred in Hinduism. Among other mammals, deer, horses, lions, bats, bears, and wolves are the subjects of myths and worship. See also Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mars#cite_note-124] | [TOKENS: 11899] |
Contents Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance. Mars is a desert-like rocky planet with a tenuous atmosphere that is primarily carbon dioxide (CO2). At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from −153 to 20 °C (−243 to 68 °F), and cosmic radiation is high. Mars retains some water, in the ground as well as thinly in the atmosphere, forming cirrus clouds, fog, frost, larger polar regions of permafrost and ice caps (with seasonal CO2 snow), but no bodies of liquid surface water. Its surface gravity is roughly a third of Earth's or double that of the Moon. Its diameter, 6,779 km (4,212 mi), is about half the Earth's, or twice the Moon's, and its surface area is the size of all the dry land of Earth. Fine dust is prevalent across the surface and the atmosphere, being picked up and spread at the low Martian gravity even by the weak wind of the tenuous atmosphere. The terrain of Mars roughly follows a north-south divide, the Martian dichotomy, with the northern hemisphere mainly consisting of relatively flat, low lying plains, and the southern hemisphere of cratered highlands. Geologically, the planet is fairly active with marsquakes trembling underneath the ground, but also hosts many enormous volcanoes that are extinct (the tallest is Olympus Mons, 21.9 km or 13.6 mi tall), as well as one of the largest canyons in the Solar System (Valles Marineris, 4,000 km or 2,500 mi long). Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos. With a significant axial tilt of 25 degrees, Mars experiences seasons, like Earth (which has an axial tilt of 23.5 degrees). A Martian solar year is equal to 1.88 Earth years (687 Earth days), a Martian solar day (sol) is equal to 24.6 hours. Mars formed along with the other planets approximately 4.5 billion years ago. During the martian Noachian period (4.5 to 3.5 billion years ago), its surface was marked by meteor impacts, valley formation, erosion, the possible presence of water oceans and the loss of its magnetosphere. The Hesperian period (beginning 3.5 billion years ago and ending 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels. The Amazonian period, which continues to the present, is the currently dominating and remaining influence on geological processes. Because of Mars's geological history, the possibility of past or present life on Mars remains an area of active scientific investigation, with some possible traces needing further examination. Being visible with the naked eye in Earth's sky as a red wandering star, Mars has been observed throughout history, acquiring diverse associations in different cultures. In 1963 the first flight to Mars took place with Mars 1, but communication was lost en route. The first successful flyby exploration of Mars was conducted in 1965 with Mariner 4. In 1971 Mariner 9 entered orbit around Mars, being the first spacecraft to orbit any body other than the Moon, Sun or Earth; following in the same year were the first uncontrolled impact (Mars 2) and first successful landing (Mars 3) on Mars. Probes have been active on Mars continuously since 1997. At times, more than ten probes have simultaneously operated in orbit or on the surface, more than at any other planet beyond Earth. Mars is an often proposed target for future crewed exploration missions, though no such mission is currently planned. Natural history Scientists have theorized that during the Solar System's formation, Mars was created as the result of a random process of run-away accretion of material from the protoplanetary disk that orbited the Sun. Mars has many distinctive chemical features caused by its position in the Solar System. Elements with comparatively low boiling points, such as chlorine, phosphorus, and sulfur, are much more common on Mars than on Earth; these elements were probably pushed outward by the young Sun's energetic solar wind. After the formation of the planets, the inner Solar System may have been subjected to the so-called Late Heavy Bombardment. About 60% of the surface of Mars shows a record of impacts from that era, whereas much of the remaining surface is probably underlain by immense impact basins caused by those events. However, more recent modeling has disputed the existence of the Late Heavy Bombardment. There is evidence of an enormous impact basin in the Northern Hemisphere of Mars, spanning 10,600 by 8,500 kilometres (6,600 by 5,300 mi), or roughly four times the size of the Moon's South Pole–Aitken basin, which would be the largest impact basin yet discovered if confirmed. It has been hypothesized that the basin was formed when Mars was struck by a Pluto-sized body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet. A 2023 study shows evidence, based on the orbital inclination of Deimos (a small moon of Mars), that Mars may once have had a ring system 3.5 billion years to 4 billion years ago. This ring system may have been formed from a moon, 20 times more massive than Phobos, orbiting Mars billions of years ago; and Phobos would be a remnant of that ring. Epochs: The geological history of Mars can be split into many periods, but the following are the three primary periods: Geological activity is still taking place on Mars. The Athabasca Valles is home to sheet-like lava flows created about 200 million years ago. Water flows in the grabens called the Cerberus Fossae occurred less than 20 million years ago, indicating equally recent volcanic intrusions. The Mars Reconnaissance Orbiter has captured images of avalanches. Physical characteristics Mars is approximately half the diameter of Earth or twice that of the Moon, with a surface area only slightly less than the total area of Earth's dry land. Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass, resulting in about 38% of Earth's surface gravity. Mars is the only presently known example of a desert planet, a rocky planet with a surface akin to that of Earth's deserts. The red-orange appearance of the Martian surface is caused by iron(III) oxide (nanophase Fe2O3) and the iron(III) oxide-hydroxide mineral goethite. It can look like butterscotch; other common surface colors include golden, brown, tan, and greenish, depending on the minerals present. Like Earth, Mars is differentiated into a dense metallic core overlaid by less dense rocky layers. The outermost layer is the crust, which is on average about 42–56 kilometres (26–35 mi) thick, with a minimum thickness of 6 kilometres (3.7 mi) in Isidis Planitia, and a maximum thickness of 117 kilometres (73 mi) in the southern Tharsis plateau. For comparison, Earth's crust averages 27.3 ± 4.8 km in thickness. The most abundant elements in the Martian crust are silicon, oxygen, iron, magnesium, aluminum, calcium, and potassium. Mars is confirmed to be seismically active; in 2019, it was reported that InSight had detected and recorded over 450 marsquakes and related events. Beneath the crust is a silicate mantle responsible for many of the tectonic and volcanic features on the planet's surface. The upper Martian mantle is a low-velocity zone, where the velocity of seismic waves is lower than surrounding depth intervals. The mantle appears to be rigid down to the depth of about 250 km, giving Mars a very thick lithosphere compared to Earth. Below this the mantle gradually becomes more ductile, and the seismic wave velocity starts to grow again. The Martian mantle does not appear to have a thermally insulating layer analogous to Earth's lower mantle; instead, below 1050 km in depth, it becomes mineralogically similar to Earth's transition zone. At the bottom of the mantle lies a basal liquid silicate layer approximately 150–180 km thick. The Martian mantle appears to be highly heterogenous, with dense fragments up to 4 km across, likely injected deep into the planet by colossal impacts ~4.5 billion years ago; high-frequency waves from eight marsquakes slowed as they passed these localized regions, and modeling indicates the heterogeneities are compositionally distinct debris preserved because Mars lacks plate tectonics and has a sluggishly convecting interior that prevents complete homogenization. Mars's iron and nickel core is at least partially molten, and may have a solid inner core. It is around half of Mars's radius, approximately 1650–1675 km, and is enriched in light elements such as sulfur, oxygen, carbon, and hydrogen. The temperature of the core is estimated to be 2000–2400 K, compared to 5400–6230 K for Earth's solid inner core. In 2025, based on data from the InSight lander, a group of researchers reported the detection of a solid inner core 613 kilometres (381 mi) ± 67 kilometres (42 mi) in radius. Mars is a terrestrial planet with a surface that consists of minerals containing silicon and oxygen, metals, and other elements that typically make up rock. The Martian surface is primarily composed of tholeiitic basalt, although parts are more silica-rich than typical basalt and may be similar to andesitic rocks on Earth, or silica glass. Regions of low albedo suggest concentrations of plagioclase feldspar, with northern low albedo regions displaying higher than normal concentrations of sheet silicates and high-silicon glass. Parts of the southern highlands include detectable amounts of high-calcium pyroxenes. Localized concentrations of hematite and olivine have been found. Much of the surface is deeply covered by finely grained iron(III) oxide dust. The Phoenix lander returned data showing Martian soil to be slightly alkaline and containing elements such as magnesium, sodium, potassium and chlorine. These nutrients are found in soils on Earth, and are necessary for plant growth. Experiments performed by the lander showed that the Martian soil has a basic pH of 7.7, and contains 0.6% perchlorate by weight, concentrations that are toxic to humans. Streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. The streaks can start in a tiny area, then spread out for hundreds of metres. They have been seen to follow the edges of boulders and other obstacles in their path. The commonly accepted hypotheses include that they are dark underlying layers of soil revealed after avalanches of bright dust or dust devils. Several other explanations have been put forward, including those that involve water or even the growth of organisms. Environmental radiation levels on the surface are on average 0.64 millisieverts of radiation per day, and significantly less than the radiation of 1.84 millisieverts per day or 22 millirads per day during the flight to and from Mars. For comparison the radiation levels in low Earth orbit, where Earth's space stations orbit, are around 0.5 millisieverts of radiation per day. Hellas Planitia has the lowest surface radiation at about 0.342 millisieverts per day, featuring lava tubes southwest of Hadriacus Mons with potentially levels as low as 0.064 millisieverts per day, comparable to radiation levels during flights on Earth. Although Mars has no evidence of a structured global magnetic field, observations show that parts of the planet's crust have been magnetized, suggesting that alternating polarity reversals of its dipole field have occurred in the past. This paleomagnetism of magnetically susceptible minerals is similar to the alternating bands found on Earth's ocean floors. One hypothesis, published in 1999 and re-examined in October 2005 (with the help of the Mars Global Surveyor), is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded. Geography and features Although better remembered for mapping the Moon, Johann Heinrich von Mädler and Wilhelm Beer were the first areographers. They began by establishing that most of Mars's surface features were permanent and by more precisely determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. Features on Mars are named from a variety of sources. Albedo features are named for classical mythology. Craters larger than roughly 50 km are named for deceased scientists and writers and others who have contributed to the study of Mars. Smaller craters are named for towns and villages of the world with populations of less than 100,000. Large valleys are named for the word "Mars" or "star" in various languages; smaller valleys are named for rivers. Large albedo features retain many of the older names but are often updated to reflect new knowledge of the nature of the features. For example, Nix Olympica (the snows of Olympus) has become Olympus Mons (Mount Olympus). The surface of Mars as seen from Earth is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian "continents" and given names like Arabia Terra (land of Arabia) or Amazonis Planitia (Amazonian plain). The dark features were thought to be seas, hence their names Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major Planum. The permanent northern polar ice cap is named Planum Boreum. The southern cap is called Planum Australe. Mars's equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's (at Greenwich), by choice of an arbitrary point; Mädler and Beer selected a line for their first maps of Mars in 1830. After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called Airy-0), located in the Sinus Meridiani ("Middle Bay" or "Meridian Bay"), was chosen by Merton E. Davies, Harold Masursky, and Gérard de Vaucouleurs for the definition of 0.0° longitude to coincide with the original selection. Because Mars has no oceans, and hence no "sea level", a zero-elevation surface had to be selected as a reference level; this is called the areoid of Mars, analogous to the terrestrial geoid. Zero altitude was defined by the height at which there is 610.5 Pa (6.105 mbar) of atmospheric pressure. This pressure corresponds to the triple point of water, and it is about 0.6% of the sea level surface pressure on Earth (0.006 atm). For mapping purposes, the United States Geological Survey divides the surface of Mars into thirty cartographic quadrangles, each named for a classical albedo feature it contains. In April 2023, The New York Times reported an updated global map of Mars based on images from the Hope spacecraft. A related, but much more detailed, global Mars map was released by NASA on 16 April 2023. The vast upland region Tharsis contains several massive volcanoes, which include the shield volcano Olympus Mons. The edifice is over 600 km (370 mi) wide. Because the mountain is so large, with complex structure at its edges, giving a definite height to it is difficult. Its local relief, from the foot of the cliffs which form its northwest margin to its peak, is over 21 km (13 mi), a little over twice the height of Mauna Kea as measured from its base on the ocean floor. The total elevation change from the plains of Amazonis Planitia, over 1,000 km (620 mi) to the northwest, to the summit approaches 26 km (16 mi), roughly three times the height of Mount Everest, which in comparison stands at just over 8.8 kilometres (5.5 mi). Consequently, Olympus Mons is either the tallest or second-tallest mountain in the Solar System; the only known mountain which might be taller is the Rheasilvia peak on the asteroid Vesta, at 20–25 km (12–16 mi). The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. It is possible that, four billion years ago, the Northern Hemisphere of Mars was struck by an object one-tenth to two-thirds the size of Earth's Moon. If this is the case, the Northern Hemisphere of Mars would be the site of an impact crater 10,600 by 8,500 kilometres (6,600 by 5,300 mi) in size, or roughly the area of Europe, Asia, and Australia combined, surpassing Utopia Planitia and the Moon's South Pole–Aitken basin as the largest impact crater in the Solar System. Mars is scarred by 43,000 impact craters with a diameter of 5 kilometres (3.1 mi) or greater. The largest exposed crater is Hellas, which is 2,300 kilometres (1,400 mi) wide and 7,000 metres (23,000 ft) deep, and is a light albedo feature clearly visible from Earth. There are other notable impact features, such as Argyre, which is around 1,800 kilometres (1,100 mi) in diameter, and Isidis, which is around 1,500 kilometres (930 mi) in diameter. Due to the smaller mass and size of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets, i.e., those that lie within the orbit of Jupiter. Martian craters can[discuss] have a morphology that suggests the ground became wet after the meteor impact. The large canyon, Valles Marineris (Latin for 'Mariner Valleys, also known as Agathodaemon in the old canal maps), has a length of 4,000 kilometres (2,500 mi) and a depth of up to 7 kilometres (4.3 mi). The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth is only 446 kilometres (277 mi) long and nearly 2 kilometres (1.2 mi) deep. Valles Marineris was formed due to the swelling of the Tharsis area, which caused the crust in the area of Valles Marineris to collapse. In 2012, it was proposed that Valles Marineris is not just a graben, but a plate boundary where 150 kilometres (93 mi) of transverse motion has occurred, making Mars a planet with possibly a two-tectonic plate arrangement. Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on the flanks of the volcano Arsia Mons. The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters". Cave entrances measure from 100 to 252 metres (328 to 827 ft) wide and they are estimated to be at least 73 to 96 metres (240 to 315 ft) deep. Because light does not reach the floor of most of the caves, they may extend much deeper than these lower estimates and widen below the surface. "Dena" is the only exception; its floor is visible and was measured to be 130 metres (430 ft) deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface. Martian geysers (or CO2 jets) are putative sites of small gas and dust eruptions that occur in the south polar region of Mars during the spring thaw. "Dark dune spots" and "spiders" – or araneiforms – are the two most visible types of features ascribed to these eruptions. Similarly sized dust will settle from the thinner Martian atmosphere sooner than it would on Earth. For example, the dust suspended by the 2001 global dust storms on Mars only remained in the Martian atmosphere for 0.6 years, while the dust from Mount Pinatubo took about two years to settle. However, under current Martian conditions, the mass movements involved are generally much smaller than on Earth. Even the 2001 global dust storms on Mars moved only the equivalent of a very thin dust layer – about 3 μm thick if deposited with uniform thickness between 58° north and south of the equator. Dust deposition at the two rover sites has proceeded at a rate of about the thickness of a grain every 100 sols. Atmosphere Mars lost its magnetosphere 4 billion years ago, possibly because of numerous asteroid strikes, so the solar wind interacts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected ionized atmospheric particles trailing off into space behind Mars, and this atmospheric loss is being studied by the MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from a low of 30 Pa (0.0044 psi) on Olympus Mons to over 1,155 Pa (0.1675 psi) in Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.087 psi). The highest atmospheric density on Mars is equal to that found 35 kilometres (22 mi) above Earth's surface. The resulting mean surface pressure is only 0.6% of Earth's 101.3 kPa (14.69 psi). The scale height of the atmosphere is about 10.8 kilometres (6.7 mi), which is higher than Earth's 6 kilometres (3.7 mi), because the surface gravity of Mars is only about 38% of Earth's. The atmosphere of Mars consists of about 96% carbon dioxide, 1.93% argon and 1.89% nitrogen along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates about 1.5 μm in diameter which give the Martian sky a tawny color when seen from the surface. It may take on a pink hue due to iron oxide particles suspended in it. Despite repeated detections of methane on Mars, there is no scientific consensus as to its origin. One suggestion is that methane exists on Mars and that its concentration fluctuates seasonally. The existence of methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars, or by Martian life. Compared to Earth, its higher concentration of atmospheric CO2 and lower surface pressure may be why sound is attenuated more on Mars, where natural sources are rare apart from the wind. Using acoustic recordings collected by the Perseverance rover, researchers concluded that the speed of sound there is approximately 240 m/s for frequencies below 240 Hz, and 250 m/s for those above. Auroras have been detected on Mars. Because Mars lacks a global magnetic field, the types and distribution of auroras there differ from those on Earth; rather than being mostly restricted to polar regions as is the case on Earth, a Martian aurora can encompass the planet. In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled, and were associated with an aurora 25 times brighter than any observed earlier, due to a massive, and unexpected, solar storm in the middle of the month. Mars has seasons, alternating between its northern and southern hemispheres, similar to on Earth. Additionally the orbit of Mars has, compared to Earth's, a large eccentricity and approaches perihelion when it is summer in its southern hemisphere and winter in its northern, and aphelion when it is winter in its southern hemisphere and summer in its northern. As a result, the seasons in its southern hemisphere are more extreme and the seasons in its northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to 30 °C (54 °F). Martian surface temperatures vary from lows of about −110 °C (−166 °F) to highs of up to 35 °C (95 °F) in equatorial summer. The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure (about 1% that of the atmosphere of Earth), and the low thermal inertia of Martian soil. The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. Mars has the largest dust storms in the Solar System, reaching speeds of over 160 km/h (100 mph). These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase global temperature. Seasons also produce dry ice covering polar ice caps. Hydrology While Mars contains water in larger amounts, most of it is dust covered water ice at the Martian polar ice caps. The volume of water ice in the south polar ice cap, if melted, would be enough to cover most of the surface of the planet with a depth of 11 metres (36 ft). Water in its liquid form cannot persist on the surface due to Mars's low atmospheric pressure, which is less than 1% that of Earth. Only at the lowest of elevations are the pressure and temperature high enough for liquid water to exist for short periods. Although little water is present in the atmosphere, there is enough to produce clouds of water ice and different cases of snow and frost, often mixed with snow of carbon dioxide dry ice. Landforms visible on Mars strongly suggest that liquid water has existed on the planet's surface. Huge linear swathes of scoured ground, known as outflow channels, cut across the surface in about 25 places. These are thought to be a record of erosion caused by the catastrophic release of water from subsurface aquifers, though some of these structures have been hypothesized to result from the action of glaciers or lava. One of the larger examples, Ma'adim Vallis, is 700 kilometres (430 mi) long, much greater than the Grand Canyon, with a width of 20 kilometres (12 mi) and a depth of 2 kilometres (1.2 mi) in places. It is thought to have been carved by flowing water early in Mars's history. The youngest of these channels is thought to have formed only a few million years ago. Elsewhere, particularly on the oldest areas of the Martian surface, finer-scale, dendritic networks of valleys are spread across significant proportions of the landscape. Features of these valleys and their distribution strongly imply that they were carved by runoff resulting from precipitation in early Mars history. Subsurface water flow and groundwater sapping may play important subsidiary roles in some networks, but precipitation was probably the root cause of the incision in almost all cases. Along craters and canyon walls, there are thousands of features that appear similar to terrestrial gullies. The gullies tend to be in the highlands of the Southern Hemisphere and face the Equator; all are poleward of 30° latitude. A number of authors have suggested that their formation process involves liquid water, probably from melting ice, although others have argued for formation mechanisms involving carbon dioxide frost or the movement of dry dust. No partially degraded gullies have formed by weathering and no superimposed impact craters have been observed, indicating that these are young features, possibly still active. Other geological features, such as deltas and alluvial fans preserved in craters, are further evidence for warmer, wetter conditions at an interval or intervals in earlier Mars history. Such conditions necessarily require the widespread presence of crater lakes across a large proportion of the surface, for which there is independent mineralogical, sedimentological and geomorphological evidence. Further evidence that liquid water once existed on the surface of Mars comes from the detection of specific minerals such as hematite and goethite, both of which sometimes form in the presence of water. The chemical signature of water vapor on Mars was first unequivocally demonstrated in 1963 by spectroscopy using an Earth-based telescope. In 2004, Opportunity detected the mineral jarosite. This forms only in the presence of acidic water, showing that water once existed on Mars. The Spirit rover found concentrated deposits of silica in 2007 that indicated wet conditions in the past, and in December 2011, the mineral gypsum, which also forms in the presence of water, was found on the surface by NASA's Mars rover Opportunity. It is estimated that the amount of water in the upper mantle of Mars, represented by hydroxyl ions contained within Martian minerals, is equal to or greater than that of Earth at 50–300 parts per million of water, which is enough to cover the entire planet to a depth of 200–1,000 metres (660–3,280 ft). On 18 March 2013, NASA reported evidence from instruments on the Curiosity rover of mineral hydration, likely hydrated calcium sulfate, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock as well as in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock. Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 60 centimetres (24 in), during the rover's traverse from the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain. In September 2015, NASA announced that they had found strong evidence of hydrated brine flows in recurring slope lineae, based on spectrometer readings of the darkened areas of slopes. These streaks flow downhill in Martian summer, when the temperature is above −23 °C, and freeze at lower temperatures. These observations supported earlier hypotheses, based on timing of formation and their rate of growth, that these dark streaks resulted from water flowing just below the surface. However, later work suggested that the lineae may be dry, granular flows instead, with at most a limited role for water in initiating the process. A definitive conclusion about the presence, extent, and role of liquid water on the Martian surface remains elusive. Researchers suspect much of the low northern plains of the planet were covered with an ocean hundreds of meters deep, though this theory remains controversial. In March 2015, scientists stated that such an ocean might have been the size of Earth's Arctic Ocean. This finding was derived from the ratio of protium to deuterium in the modern Martian atmosphere compared to that ratio on Earth. The amount of Martian deuterium (D/H = 9.3 ± 1.7 10−4) is five to seven times the amount on Earth (D/H = 1.56 10−4), suggesting that ancient Mars had significantly higher levels of water. Results from the Curiosity rover had previously found a high ratio of deuterium in Gale Crater, though not significantly high enough to suggest the former presence of an ocean. Other scientists caution that these results have not been confirmed, and point out that Martian climate models have not yet shown that the planet was warm enough in the past to support bodies of liquid water. Near the northern polar cap is the 81.4 kilometres (50.6 mi) wide Korolev Crater, which the Mars Express orbiter found to be filled with approximately 2,200 cubic kilometres (530 cu mi) of water ice. In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior (which is 12,100 cubic kilometers). During observations from 2018 through 2021, the ExoMars Trace Gas Orbiter spotted indications of water, probably subsurface ice, in the Valles Marineris canyon system. Orbital motion Mars's average distance from the Sun is roughly 230 million km (143 million mi), and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. The gravitational potential difference and thus the delta-v needed to transfer between Mars and Earth is the second lowest for Earth. The axial tilt of Mars is 25.19° relative to its orbital plane, which is similar to the axial tilt of Earth. As a result, Mars has seasons like Earth, though on Mars they are nearly twice as long because its orbital period is that much longer. In the present day, the orientation of the north pole of Mars is close to the star Deneb. Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury has a larger orbital eccentricity. It is known that in the past, Mars has had a much more circular orbit. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years. Mars has its closest approach to Earth (opposition) in a synodic period of 779.94 days. It should not be confused with Mars conjunction, where the Earth and Mars are at opposite sides of the Solar System and form a straight line crossing the Sun. The average time between the successive oppositions of Mars, its synodic period, is 780 days; but the number of days between successive oppositions can range from 764 to 812. The distance at close approach varies between about 54 and 103 million km (34 and 64 million mi) due to the planets' elliptical orbits, which causes comparable variation in angular size. At their furthest Mars and Earth can be as far as 401 million km (249 million mi) apart. Mars comes into opposition from Earth every 2.1 years. The planets come into opposition near Mars's perihelion in 2003, 2018 and 2035, with the 2020 and 2033 events being particularly close to perihelic opposition. The mean apparent magnitude of Mars is +0.71 with a standard deviation of 1.05. Because the orbit of Mars is eccentric, the magnitude at opposition from the Sun can range from about −3.0 to −1.4. The minimum brightness is magnitude +1.86 when the planet is near aphelion and in conjunction with the Sun. At its brightest, Mars (along with Jupiter) is second only to Venus in apparent brightness. Mars usually appears distinctly yellow, orange, or red. When farthest away from Earth, it is more than seven times farther away than when it is closest. Mars is usually close enough for particularly good viewing once or twice at 15-year or 17-year intervals. Optical ground-based telescopes are typically limited to resolving features about 300 kilometres (190 mi) across when Earth and Mars are closest because of Earth's atmosphere. As Mars approaches opposition, it begins a period of retrograde motion, which means it will appear to move backwards in a looping curve with respect to the background stars. This retrograde motion lasts for about 72 days, and Mars reaches its peak apparent brightness in the middle of this interval. Moons Mars has two relatively small (compared to Earth's) natural moons, Phobos (about 22 km (14 mi) in diameter) and Deimos (about 12 km (7.5 mi) in diameter), which orbit at 9,376 km (5,826 mi) and 23,460 km (14,580 mi) around the planet. The origin of both moons is unclear, although a popular theory states that they were asteroids captured into Martian orbit. Both satellites were discovered in 1877 by Asaph Hall and were named after the characters Phobos (the deity of panic and fear) and Deimos (the deity of terror and dread), twins from Greek mythology who accompanied their father Ares, god of war, into battle. Mars was the Roman equivalent to Ares. In modern Greek, the planet retains its ancient name Ares (Aris: Άρης). From the surface of Mars, the motions of Phobos and Deimos appear different from that of the Earth's satellite, the Moon. Phobos rises in the west, sets in the east, and rises again in just 11 hours. Deimos, being only just outside synchronous orbit – where the orbital period would match the planet's period of rotation – rises as expected in the east, but slowly. Because the orbit of Phobos is below a synchronous altitude, tidal forces from Mars are gradually lowering its orbit. In about 50 million years, it could either crash into Mars's surface or break up into a ring structure around the planet. The origin of the two satellites is not well understood. Their low albedo and carbonaceous chondrite composition have been regarded as similar to asteroids, supporting a capture theory. The unstable orbit of Phobos would seem to point toward a relatively recent capture. But both have circular orbits near the equator, which is unusual for captured objects, and the required capture dynamics are complex. Accretion early in the history of Mars is plausible, but would not account for a composition resembling asteroids rather than Mars itself, if that is confirmed. Mars may have yet-undiscovered moons, smaller than 50 to 100 metres (160 to 330 ft) in diameter, and a dust ring is predicted to exist between Phobos and Deimos. A third possibility for their origin as satellites of Mars is the involvement of a third body or a type of impact disruption. More-recent lines of evidence for Phobos having a highly porous interior, and suggesting a composition containing mainly phyllosilicates and other minerals known from Mars, point toward an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's satellite. Although the visible and near-infrared (VNIR) spectra of the moons of Mars resemble those of outer-belt asteroids, the thermal infrared spectra of Phobos are reported to be inconsistent with chondrites of any class. It is also possible that Phobos and Deimos were fragments of an older moon, formed by debris from a large impact on Mars, and then destroyed by a more recent impact upon the satellite. More recently, a study conducted by a team of researchers from multiple countries suggests that a lost moon, at least fifteen times the size of Phobos, may have existed in the past. By analyzing rocks which point to tidal processes on the planet, it is possible that these tides may have been regulated by a past moon. Human observations and exploration The history of observations of Mars is marked by oppositions of Mars when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the perihelic oppositions of Mars, which are distinguished because Mars is close to perihelion, making it even closer to Earth. The ancient Sumerians named Mars Nergal, the god of war and plague. During Sumerian times, Nergal was a minor deity of little significance, but, during later times, his main cult center was the city of Nineveh. In Mesopotamian texts, Mars is referred to as the "star of judgement of the fate of the dead". The existence of Mars as a wandering object in the night sky was also recorded by the ancient Egyptian astronomers and, by 1534 BCE, they were familiar with the retrograde motion of the planet. By the period of the Neo-Babylonian Empire, the Babylonian astronomers were making regular records of the positions of the planets and systematic observations of their behavior. For Mars, they knew that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years. They invented arithmetic methods for making minor corrections to the predicted positions of the planets. In Ancient Greece, the planet was known as Πυρόεις. Commonly, the Greek name for the planet now referred to as Mars, was Ares. It was the Romans who named the planet Mars, for their god of war, often represented by the sword and shield of the planet's namesake. In the fourth century BCE, Aristotle noted that Mars disappeared behind the Moon during an occultation, indicating that the planet was farther away. Ptolemy, a Greek living in Alexandria, attempted to address the problem of the orbital motion of Mars. Ptolemy's model and his collective work on astronomy was presented in the multi-volume collection later called the Almagest (from the Arabic for "greatest"), which became the authoritative treatise on Western astronomy for the next fourteen centuries. Literature from ancient China confirms that Mars was known by Chinese astronomers by no later than the fourth century BCE. In the East Asian cultures, Mars is traditionally referred to as the "fire star" (火星) based on the Wuxing system. In 1609 Johannes Kepler published a 10 year study of Martian orbit, using the diurnal parallax of Mars, measured by Tycho Brahe, to make a preliminary calculation of the relative distance to the planet. From Brahe's observations of Mars, Kepler deduced that the planet orbited the Sun not in a circle, but in an ellipse. Moreover, Kepler showed that Mars sped up as it approached the Sun and slowed down as it moved farther away, in a manner that later physicists would explain as a consequence of the conservation of angular momentum.: 433–437 In 1610 the first use of a telescope for astronomical observation, including Mars, was performed by Italian astronomer Galileo Galilei. With the telescope the diurnal parallax of Mars was again measured in an effort to determine the Sun-Earth distance. This was first performed by Giovanni Domenico Cassini in 1672. The early parallax measurements were hampered by the quality of the instruments. The only occultation of Mars by Venus observed was that of 13 October 1590, seen by Michael Maestlin at Heidelberg. By the 19th century, the resolution of telescopes reached a level sufficient for surface features to be identified. On 5 September 1877, a perihelic opposition to Mars occurred. The Italian astronomer Giovanni Schiaparelli used a 22-centimetre (8.7 in) telescope in Milan to help produce the first detailed map of Mars. These maps notably contained features he called canali, which, with the possible exception of the natural canyon Valles Marineris, were later shown to be an optical illusion. These canali were supposedly long, straight lines on the surface of Mars, to which he gave names of famous rivers on Earth. His term, which means "channels" or "grooves", was popularly mistranslated in English as "canals". Influenced by the observations, the orientalist Percival Lowell founded an observatory which had 30- and 45-centimetre (12- and 18-in) telescopes. The observatory was used for the exploration of Mars during the last good opportunity in 1894, and the following less favorable oppositions. He published several books on Mars and life on the planet, which had a great influence on the public. The canali were independently observed by other astronomers, like Henri Joseph Perrotin and Louis Thollon in Nice, using one of the largest telescopes of that time. The seasonal changes (consisting of the diminishing of the polar caps and the dark areas formed during Martian summers) in combination with the canals led to speculation about life on Mars, and it was a long-held belief that Mars contained vast seas and vegetation. As bigger telescopes were used, fewer long, straight canali were observed. During observations in 1909 by Antoniadi with an 84-centimetre (33 in) telescope, irregular patterns were observed, but no canali were seen. The first spacecraft from Earth to visit Mars was Mars 1 of the Soviet Union, which flew by in 1963, but contact was lost en route. NASA's Mariner 4 followed and became the first spacecraft to successfully transmit from Mars; launched on 28 November 1964, it made its closest approach to the planet on 15 July 1965. Mariner 4 detected the weak Martian radiation belt, measured at about 0.1% that of Earth, and captured the first images of another planet from deep space. Once spacecraft visited the planet during the 1960s and 1970s, many previous concepts of Mars were radically broken. After the results of the Viking life-detection experiments, the hypothesis of a dead planet was generally accepted. The data from Mariner 9 and Viking allowed better maps of Mars to be made. Until 1997 and after Viking 1 shut down in 1982, Mars was only visited by three unsuccessful probes, two flying past without contact (Phobos 1, 1988; Mars Observer, 1993), and one (Phobos 2 1989) malfunctioning in orbit before reaching its destination Phobos. In 1997 Mars Pathfinder became the first successful rover mission beyond the Moon and started together with Mars Global Surveyor (operated until late 2006) an uninterrupted active robotic presence at Mars that has lasted until today. It produced complete, extremely detailed maps of the Martian topography, magnetic field and surface minerals. Starting with these missions a range of new improved crewless spacecraft, including orbiters, landers, and rovers, have been sent to Mars, with successful missions by the NASA (United States), Jaxa (Japan), ESA, United Kingdom, ISRO (India), Roscosmos (Russia), the United Arab Emirates, and CNSA (China) to study the planet's surface, climate, and geology, uncovering the different elements of the history and dynamic of the hydrosphere of Mars and possible traces of ancient life. As of 2023[update], Mars is host to ten functioning spacecraft. Eight are in orbit: 2001 Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, MAVEN, ExoMars Trace Gas Orbiter, the Hope orbiter, and the Tianwen-1 orbiter. Another two are on the surface: the Mars Science Laboratory Curiosity rover and the Perseverance rover. Collected maps are available online at websites including Google Mars. NASA provides two online tools: Mars Trek, which provides visualizations of the planet using data from 50 years of exploration, and Experience Curiosity, which simulates traveling on Mars in 3-D with Curiosity. Planned missions to Mars include: As of February 2024[update], debris from these types of missions has reached over seven tons. Most of it consists of crashed and inactive spacecraft as well as discarded components. In April 2024, NASA selected several companies to begin studies on providing commercial services to further enable robotic science on Mars. Key areas include establishing telecommunications, payload delivery and surface imaging. Habitability and habitation During the late 19th century, it was widely accepted in the astronomical community that Mars had life-supporting qualities, including the presence of oxygen and water. However, in 1894 W. W. Campbell at Lick Observatory observed the planet and found that "if water vapor or oxygen occur in the atmosphere of Mars it is in quantities too small to be detected by spectroscopes then available". That observation contradicted many of the measurements of the time and was not widely accepted. Campbell and V. M. Slipher repeated the study in 1909 using better instruments, but with the same results. It was not until the findings were confirmed by W. S. Adams in 1925 that the myth of the Earth-like habitability of Mars was finally broken. However, even in the 1960s, articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars. The current understanding of planetary habitability – the ability of a world to develop environmental conditions favorable to the emergence of life – favors planets that have liquid water on their surface. Most often this requires the orbit of a planet to lie within the habitable zone, which for the Sun is estimated to extend from within the orbit of Earth to about that of Mars. During perihelion, Mars dips inside this region, but Mars's thin (low-pressure) atmosphere prevents liquid water from existing over large regions for extended periods. The past flow of liquid water demonstrates the planet's potential for habitability. Recent evidence has suggested that any water on the Martian surface may have been too salty and acidic to support regular terrestrial life. The environmental conditions on Mars are a challenge to sustaining organic life: the planet has little heat transfer across its surface, it has poor insulation against bombardment by the solar wind due to the absence of a magnetosphere and has insufficient atmospheric pressure to retain water in a liquid form (water instead sublimes to a gaseous state). Mars is nearly, or perhaps totally, geologically dead; the end of volcanic activity has apparently stopped the recycling of chemicals and minerals between the surface and interior of the planet. Evidence suggests that the planet was once significantly more habitable than it is today, but whether living organisms ever existed there remains unknown. The Viking probes of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites and had positive results, including a temporary increase in CO2 production on exposure to water and nutrients. This sign of life was later disputed by scientists, resulting in a continuing debate, with NASA scientist Gilbert Levin asserting that Viking may have found life. A 2014 analysis of Martian meteorite EETA79001 found chlorate, perchlorate, and nitrate ions in sufficiently high concentrations to suggest that they are widespread on Mars. UV and X-ray radiation would turn chlorate and perchlorate ions into other, highly reactive oxychlorines, indicating that any organic molecules would have to be buried under the surface to survive. Small quantities of methane and formaldehyde detected by Mars orbiters are both claimed to be possible evidence for life, as these chemical compounds would quickly break down in the Martian atmosphere. Alternatively, these compounds may instead be replenished by volcanic or other geological means, such as serpentinite. Impact glass, formed by the impact of meteors, which on Earth can preserve signs of life, has also been found on the surface of the impact craters on Mars. Likewise, the glass in impact craters on Mars could have preserved signs of life, if life existed at the site. The Cheyava Falls rock discovered on Mars in June 2024 has been designated by NASA as a "potential biosignature" and was core sampled by the Perseverance rover for possible return to Earth and further examination. Although highly intriguing, no definitive final determination on a biological or abiotic origin of this rock can be made with the data currently available. Several plans for a human mission to Mars have been proposed, but none have come to fruition. The NASA Authorization Act of 2017 directed NASA to study the feasibility of a crewed Mars mission in the early 2030s; the resulting report concluded that this would be unfeasible. In addition, in 2021, China was planning to send a crewed Mars mission in 2033. Privately held companies such as SpaceX have also proposed plans to send humans to Mars, with the eventual goal to settle on the planet. As of 2024, SpaceX has proceeded with the development of the Starship launch vehicle with the goal of Mars colonization. In plans shared with the company in April 2024, Elon Musk envisions the beginning of a Mars colony within the next twenty years. This would be enabled by the planned mass manufacturing of Starship and initially sustained by resupply from Earth, and in situ resource utilization on Mars, until the Mars colony reaches full self sustainability. Any future human mission to Mars will likely take place within the optimal Mars launch window, which occurs every 26 months. The moon Phobos has been proposed as an anchor point for a space elevator. Besides national space agencies and space companies, groups such as the Mars Society and The Planetary Society advocate for human missions to Mars. In culture Mars is named after the Roman god of war (Greek Ares), but was also associated with the demi-god Heracles (Roman Hercules) by ancient Greek astronomers, as detailed by Aristotle. This association between Mars and war dates back at least to Babylonian astronomy, in which the planet was named for the god Nergal, deity of war and destruction. It persisted into modern times, as exemplified by Gustav Holst's orchestral suite The Planets, whose famous first movement labels Mars "The Bringer of War". The planet's symbol, a circle with a spear pointing out to the upper right, is also used as a symbol for the male gender. The symbol dates from at least the 11th century, though a possible predecessor has been found in the Greek Oxyrhynchus Papyri. The idea that Mars was populated by intelligent Martians became widespread in the late 19th century. Schiaparelli's "canali" observations combined with Percival Lowell's books on the subject put forward the standard notion of a planet that was a drying, cooling, dying world with ancient civilizations constructing irrigation works. Many other observations and proclamations by notable personalities added to what has been termed "Mars Fever". In the present day, high-resolution mapping of the surface of Mars has revealed no artifacts of habitation, but pseudoscientific speculation about intelligent life on Mars still continues. Reminiscent of the canali observations, these speculations are based on small scale features perceived in the spacecraft images, such as "pyramids" and the "Face on Mars". In his book Cosmos, planetary astronomer Carl Sagan wrote: "Mars has become a kind of mythic arena onto which we have projected our Earthly hopes and fears." The depiction of Mars in fiction has been stimulated by its dramatic red color and by nineteenth-century scientific speculations that its surface conditions might support not just life but intelligent life. This gave way to many science fiction stories involving these concepts, such as H. G. Wells's The War of the Worlds, in which Martians seek to escape their dying planet by invading Earth; Ray Bradbury's The Martian Chronicles, in which human explorers accidentally destroy a Martian civilization; as well as Edgar Rice Burroughs's series Barsoom, C. S. Lewis's novel Out of the Silent Planet (1938), and a number of Robert A. Heinlein stories before the mid-sixties. Since then, depictions of Martians have also extended to animation. A comic figure of an intelligent Martian, Marvin the Martian, appeared in Haredevil Hare (1948) as a character in the Looney Tunes animated cartoons of Warner Brothers, and has continued as part of popular culture to the present. After the Mariner and Viking spacecraft had returned pictures of Mars as a lifeless and canal-less world, these ideas about Mars were abandoned; for many science-fiction authors, the new discoveries initially seemed like a constraint, but eventually the post-Viking knowledge of Mars became itself a source of inspiration for works like Kim Stanley Robinson's Mars trilogy. See also Notes References Further reading External links Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Local Volume → Virgo Supercluster → Laniakea Supercluster → Pisces–Cetus Supercluster Complex → Local Hole → Observable universe → UniverseEach arrow (→) may be read as "within" or "part of". |
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Contents Minecraft Minecraft is a sandbox game developed and published by Mojang Studios. Following its initial public alpha release in 2009, it was formally released in 2011 for personal computers. The game has since been ported to numerous platforms, including mobile devices and various video game consoles. In Minecraft, players explore a procedurally generated world with virtually infinite terrain made up of voxels (cubes). They can discover and extract raw materials, craft tools and items, build structures, fight hostile mobs, and cooperate with or compete against other players in multiplayer. The game's large community offers a wide variety of user-generated content, such as modifications, servers, player skins, texture packs, and custom maps, which add new game mechanics and possibilities. Originally created by Markus "Notch" Persson using the Java programming language, Jens "Jeb" Bergensten was handed control over the game's development following its full release. In 2014, Mojang and the Minecraft intellectual property were purchased by Microsoft for US$2.5 billion; Xbox Game Studios hold the publishing rights for the Bedrock Edition, the unified cross-platform version which evolved from the Pocket Edition codebase[i] and replaced the legacy console versions. Bedrock is updated concurrently with Mojang's original Java Edition, although with numerous, generally small, differences. Minecraft is the best-selling video game in history with over 350 million copies sold. It has received critical acclaim, winning several awards and being cited as one of the greatest video games of all time. Social media, parodies, adaptations, merchandise, and the annual Minecon conventions have played prominent roles in popularizing it. The wider Minecraft franchise includes several spin-off games, such as Minecraft: Story Mode, Minecraft Dungeons, and Minecraft Legends. A film adaptation, titled A Minecraft Movie, was released in 2025 and became the second highest-grossing video game film of all time. Gameplay Minecraft is a 3D sandbox video game that has no required goals to accomplish, giving players a large amount of freedom in choosing how to play the game. The game features an optional achievement system. Gameplay is in the first-person perspective by default, but players have the option of third-person perspectives. The game world is composed of rough 3D objects—mainly cubes, referred to as blocks—representing various materials, such as dirt, stone, ores, tree trunks, water, and lava. The core gameplay revolves around picking up and placing these objects. These blocks are arranged in a voxel grid, while players can move freely around the world. Players can break, or mine, blocks and then place them elsewhere, enabling them to build things. Very few blocks are affected by gravity, instead maintaining their voxel position in the air. Players can also craft a wide variety of items, such as armor, which mitigates damage from attacks; weapons (such as swords or bows and arrows), which allow monsters and animals to be killed more easily; and tools (such as pickaxes or shovels), which break certain types of blocks more quickly. Some items have multiple tiers depending on the material used to craft them, with higher-tier items being more effective and durable. They may also freely craft helpful blocks—such as furnaces which can cook food and smelt ores, and torches that produce light—or exchange items with villagers (NPC) through trading emeralds for different goods and vice versa. The game has an inventory system, allowing players to carry a limited number of items. The in-game time system follows a day and night cycle, with one full cycle lasting for 20 real-time minutes. The game also contains a material called redstone, which can be used to make primitive mechanical devices, electrical circuits, and logic gates, allowing for the construction of many complex systems. New players are given a randomly selected default character skin out of nine possibilities, including Steve or Alex, but are able to create and upload their own skins. Players encounter various mobs (short for mobile entities) including animals, villagers, and hostile creatures. Passive mobs, such as cows, pigs, and chickens, spawn during the daytime and can be hunted for food and crafting materials, while hostile mobs—including large spiders, witches, skeletons, and zombies—spawn during nighttime or in dark places such as caves. Some hostile mobs, such as zombies and skeletons, burn under the sun if they have no headgear and are not standing in water. Other creatures unique to Minecraft include the creeper (an exploding creature that sneaks up on the player) and the enderman (a creature with the ability to teleport as well as pick up and place blocks). There are also variants of mobs that spawn in different conditions; for example, zombies have husk and drowned variants that spawn in deserts and oceans, respectively. The Minecraft environment is procedurally generated as players explore it using a map seed that is randomly chosen at the time of world creation (or manually specified by the player). Divided into biomes representing different environments with unique resources and structures, worlds are designed to be effectively infinite in traditional gameplay, though technical limits on the player have existed throughout development, both intentionally and not. Implementation of horizontally infinite generation initially resulted in a glitch termed the "Far Lands" at over 12 million blocks away from the world center, where terrain generated as wall-like, fissured patterns. The Far Lands and associated glitches were considered the effective edge of the world until they were resolved, with the current horizontal limit instead being a special impassable barrier called the world border, located 30 million blocks away. Vertical space is comparatively limited, with an unbreakable bedrock layer at the bottom and a building limit several hundred blocks into the sky. Minecraft features three independent dimensions accessible through portals and providing alternate game environments. The Overworld is the starting dimension and represents the real world, with a terrestrial surface setting including plains, mountains, forests, oceans, caves, and small sources of lava. The Nether is a hell-like underworld dimension accessed via an obsidian portal and composed mainly of lava. Mobs that populate the Nether include shrieking, fireball-shooting ghasts, alongside anthropomorphic pigs called piglins and their zombified counterparts. Piglins in particular have a bartering system, where players can give them gold ingots and receive items in return. Structures known as Nether Fortresses generate in the Nether, containing mobs such as wither skeletons and blazes, which can drop blaze rods needed to access the End dimension. The player can also choose to build an optional boss mob known as the Wither, using skulls obtained from wither skeletons and soul sand. The End can be reached through an end portal, consisting of twelve end portal frames. End portals are found in underground structures in the Overworld known as strongholds. To find strongholds, players must craft eyes of ender using an ender pearl and blaze powder. Eyes of ender can then be thrown, traveling in the direction of the stronghold. Once the player reaches the stronghold, they can place eyes of ender into each portal frame to activate the end portal. The dimension consists of islands floating in a dark, bottomless void. A boss enemy called the Ender Dragon guards the largest, central island. Killing the dragon opens access to an exit portal, which, when entered, cues the game's ending credits and the End Poem, a roughly 1,500-word work written by Irish novelist Julian Gough, which takes about nine minutes to scroll past, is the game's only narrative text, and the only text of significant length directed at the player.: 10–12 At the conclusion of the credits, the player is teleported back to their respawn point and may continue the game indefinitely. In Survival mode, players have to gather natural resources such as wood and stone found in the environment in order to craft certain blocks and items. Depending on the difficulty, monsters spawn in darker areas outside a certain radius of the character, requiring players to build a shelter in order to survive at night. The mode also has a health bar which is depleted by attacks from mobs, falls, drowning, falling into lava, suffocation, starvation, and other events. Players also have a hunger bar, which must be periodically refilled by eating food in-game unless the player is playing on peaceful difficulty. If the hunger bar is empty, the player starves. Health replenishes when players have a full hunger bar or continuously on peaceful. Upon losing all health, players die. The items in the players' inventories are dropped unless the game is reconfigured not to do so. Players then re-spawn at their spawn point, which by default is where players first spawn in the game and can be changed by sleeping in a bed or using a respawn anchor. Dropped items can be recovered if players can reach them before they despawn after 5 minutes. Players may acquire experience points (commonly referred to as "xp" or "exp") by killing mobs and other players, mining, smelting ores, animal breeding, and cooking food. Experience can then be spent on enchanting tools, armor and weapons. Enchanted items are generally more powerful, last longer, or have other special effects. The game features two more game modes based on Survival, known as Hardcore mode and Adventure mode. Hardcore mode plays identically to Survival mode, but with the game's difficulty setting locked to "Hard" and with permadeath, forcing them to delete the world or explore it as a spectator after dying. Adventure mode was added to the game in a post-launch update, and prevents the player from directly modifying the game's world. It was designed primarily for use in custom maps, allowing map designers to let players experience it as intended. In Creative mode, players have access to an infinite number of all resources and items in the game through the inventory menu and can place or mine them instantly. Players can toggle the ability to fly freely around the game world at will, and their characters usually do not take any damage nor are affected by hunger. The game mode helps players focus on building and creating projects of any size without disturbance. Multiplayer in Minecraft enables multiple players to interact and communicate with each other on a single world. It is available through direct game-to-game multiplayer, local area network (LAN) play, local split screen (console-only), and servers (player-hosted and business-hosted). Players can run their own server by making a realm, using a host provider, hosting one themselves or connect directly to another player's game via Xbox Live, PlayStation Network or Nintendo Switch Online. Single-player worlds have LAN support, allowing players to join a world on locally interconnected computers without a server setup. Minecraft multiplayer servers are guided by server operators, who have access to server commands such as setting the time of day and teleporting players. Operators can also set up restrictions concerning which usernames or IP addresses are allowed or disallowed to enter the server. Multiplayer servers have a wide range of activities, with some servers having their own unique rules and customs. The largest and most popular server is Hypixel, which has been visited by over 14 million unique players. Player versus player combat (PvP) can be enabled to allow fighting between players. In 2013, Mojang announced Minecraft Realms, a server hosting service intended to enable players to run server multiplayer games easily and safely without having to set up their own. Unlike a standard server, only invited players can join Realms servers, and these servers do not use server addresses. Minecraft: Java Edition Realms server owners can invite up to twenty people to play on their server, with up to ten players online at a time. Minecraft Realms server owners can invite up to 3,000 people to play on their server, with up to ten players online at one time. The Minecraft: Java Edition Realms servers do not support user-made plugins, but players can play custom Minecraft maps. Minecraft Bedrock Realms servers support user-made add-ons, resource packs, behavior packs, and custom Minecraft maps. At Electronic Entertainment Expo 2016, support for cross-platform play between Windows 10, iOS, and Android platforms was added through Realms starting in June 2016, with Xbox One and Nintendo Switch support to come later in 2017, and support for virtual reality devices. On 31 July 2017, Mojang released the beta version of the update allowing cross-platform play. Nintendo Switch support for Realms was released in July 2018. The modding community consists of fans, users and third-party programmers. Using a variety of application program interfaces that have arisen over time, they have produced a wide variety of downloadable content for Minecraft, such as modifications, texture packs and custom maps. Modifications of the Minecraft code, called mods, add a variety of gameplay changes, ranging from new blocks, items, and mobs to entire arrays of mechanisms. The modding community is responsible for a substantial supply of mods from ones that enhance gameplay, such as mini-maps, waypoints, and durability counters, to ones that add to the game elements from other video games and media. While a variety of mod frameworks were independently developed by reverse engineering the code, Mojang has also enhanced vanilla Minecraft with official frameworks for modification, allowing the production of community-created resource packs, which alter certain game elements including textures and sounds. Players can also create their own "maps" (custom world save files) that often contain specific rules, challenges, puzzles and quests, and share them for others to play. Mojang added an adventure mode in August 2012 and "command blocks" in October 2012, which were created specially for custom maps in Java Edition. Data packs, introduced in version 1.13 of the Java Edition, allow further customization, including the ability to add new achievements, dimensions, functions, loot tables, predicates, recipes, structures, tags, and world generation. The Xbox 360 Edition supported downloadable content, which was available to purchase via the Xbox Games Store; these content packs usually contained additional character skins. It later received support for texture packs in its twelfth title update while introducing "mash-up packs", which combined texture packs with skin packs and changes to the game's sounds, music and user interface. The first mash-up pack (and by extension, the first texture pack) for the Xbox 360 Edition was released on 4 September 2013, and was themed after the Mass Effect franchise. Unlike Java Edition, however, the Xbox 360 Edition did not support player-made mods or custom maps. A cross-promotional resource pack based on the Super Mario franchise by Nintendo was released exclusively for the Wii U Edition worldwide on 17 May 2016, and later bundled free with the Nintendo Switch Edition at launch. Another based on Fallout was released on consoles that December, and for Windows and Mobile in April 2017. In April 2018, malware was discovered in several downloadable user-made Minecraft skins for use with the Java Edition of the game. Avast stated that nearly 50,000 accounts were infected, and when activated, the malware would attempt to reformat the user's hard drive. Mojang promptly patched the issue, and released a statement stating that "the code would not be run or read by the game itself", and would run only when the image containing the skin itself was opened. In June 2017, Mojang released the "1.1 Discovery Update" to the Pocket Edition of the game, which later became the Bedrock Edition. The update introduced the "Marketplace", a catalogue of purchasable user-generated content intended to give Minecraft creators "another way to make a living from the game". Various skins, maps, texture packs and add-ons from different creators can be bought with "Minecoins", a digital currency that is purchased with real money. Additionally, users can access specific content with a subscription service titled "Marketplace Pass". Alongside content from independent creators, the Marketplace also houses items published by Mojang and Microsoft themselves, as well as official collaborations between Minecraft and other intellectual properties. By 2022, the Marketplace had over 1.7 billion content downloads, generating over $500 million in revenue. Development Before creating Minecraft, Markus "Notch" Persson was a game developer at King, where he worked until March 2009. At King, he primarily developed browser games and learned several programming languages. During his free time, he prototyped his own games, often drawing inspiration from other titles, and was an active participant on the TIGSource forums for independent developers. One such project was "RubyDung", a base-building game inspired by Dwarf Fortress, but with an isometric, three-dimensional perspective similar to RollerCoaster Tycoon. Among the features in RubyDung that he explored was a first-person view similar to Dungeon Keeper, though he ultimately discarded this idea, feeling the graphics were too pixelated at the time. Around March 2009, Persson left King and joined jAlbum, while continuing to work on his prototypes. Infiniminer, a block-based open-ended mining game first released in April 2009, inspired Persson's vision for RubyDung's future direction. Infiniminer heavily influenced the visual style of gameplay, including bringing back the first-person mode, the "blocky" visual style and the block-building fundamentals. However, unlike Infiniminer, Persson wanted Minecraft to have RPG elements. The first public alpha build of Minecraft was released on 17 May 2009 on TIGSource. Over the years, Persson regularly released test builds that added new features, including tools, mobs, and entire new dimensions. In 2011, partly due to the game's rising popularity, Persson decided to release a full 1.0 version—a second part of the "Adventure Update"—on 18 November 2011. Shortly after, Persson stepped down from development, handing the project's lead to Jens "Jeb" Bergensten. On 15 September 2014, Microsoft, the developer behind the Microsoft Windows operating system and Xbox video game console, announced a $2.5 billion acquisition of Mojang, which included the Minecraft intellectual property. Persson had suggested the deal on Twitter, asking a corporation to buy his stake in the game after receiving criticism for enforcing terms in the game's end-user license agreement (EULA), which had been in place for the past three years. According to Persson, Mojang CEO Carl Manneh received a call from a Microsoft executive shortly after the tweet, asking if Persson was serious about a deal. Mojang was also approached by other companies including Activision Blizzard and Electronic Arts. The deal with Microsoft was arbitrated on 6 November 2014 and led to Persson becoming one of Forbes' "World's Billionaires". After 2014, Minecraft's primary versions received usually annual major updates—free to players who have purchased the game— each primarily centered around a specific theme. For instance, version 1.13, the Update Aquatic, focused on ocean-related features, while version 1.16, the Nether Update, introduced significant changes to the Nether dimension. However, in late 2024, Mojang announced a shift in their update strategy; rather than releasing large updates annually, they opted for a more frequent release schedule with smaller, incremental updates, stating, "We know that you want new Minecraft content more often." The Bedrock Edition has also received regular updates, now matching the themes of the Java Edition updates. Other versions of the game, such as various console editions and the Pocket Edition, were either merged into Bedrock or discontinued and have not received further updates. On 7 May 2019, coinciding with Minecraft's 10th anniversary, a JavaScript recreation of an old 2009 Java Edition build named Minecraft Classic was made available to play online for free. On 16 April 2020, a Bedrock Edition-exclusive beta version of Minecraft, called Minecraft RTX, was released by Nvidia. It introduced physically-based rendering, real-time path tracing, and DLSS for RTX-enabled GPUs. The public release was made available on 8 December 2020. Path tracing can only be enabled in supported worlds, which can be downloaded for free via the in-game Minecraft Marketplace, with a texture pack from Nvidia's website, or with compatible third-party texture packs. It cannot be enabled by default with any texture pack on any world. Initially, Minecraft RTX was affected by many bugs, display errors, and instability issues. On 22 March 2025, a new visual mode called Vibrant Visuals, an optional graphical overhaul similar to Minecraft RTX, was announced. It promises modern rendering features—such as dynamic shadows, screen space reflections, volumetric fog, and bloom—without the need of RTX-capable hardware. Vibrant Visuals was released as a part of the Chase the Skies update on 17 June 2025 for Bedrock Edition and is planned to release on Java Edition at a later date. Development began for the original edition of Minecraft—then known as Cave Game, and now known as the Java Edition—in May 2009,[k] and ended on 13 May, when Persson released a test video on YouTube of an early version of the game, dubbed the "Cave game tech test" or the "Cave game tech demo". The game was named Minecraft: Order of the Stone the next day, after a suggestion made by a player. "Order of the Stone" came from the webcomic The Order of the Stick, and "Minecraft" was chosen "because it's a good name". The title was later shortened to just Minecraft, omitting the subtitle. Persson completed the game's base programming over a weekend in May 2009, and private testing began on TigIRC on 16 May. The first public release followed on 17 May 2009 as a developmental version shared on the TIGSource forums. Based on feedback from forum users, Persson continued updating the game. This initial public build later became known as Classic. Further developmental phases—dubbed Survival Test, Indev, and Infdev—were released throughout 2009 and 2010. The first major update, known as Alpha, was released on 30 June 2010. At the time, Persson was still working a day job at jAlbum but later resigned to focus on Minecraft full-time as sales of the alpha version surged. Updates were distributed automatically, introducing new blocks, items, mobs, and changes to game mechanics such as water flow. With revenue generated from the game, Persson founded Mojang, a video game studio, alongside former colleagues Jakob Porser and Carl Manneh. On 11 December 2010, Persson announced that Minecraft would enter its beta phase on 20 December. He assured players that bug fixes and all pre-release updates would remain free. As development progressed, Mojang expanded, hiring additional employees to work on the project. The game officially exited beta and launched in full on 18 November 2011. On 1 December 2011, Jens "Jeb" Bergensten took full creative control over Minecraft, replacing Persson as lead designer. On 28 February 2012, Mojang announced the hiring of the developers behind Bukkit, a popular developer API for Minecraft servers, to improve Minecraft's support of server modifications. This move included Mojang taking apparent ownership of the CraftBukkit server mod, though this apparent acquisition later became controversial, and its legitimacy was questioned due to CraftBukkit's open-source nature and licensing under the GNU General Public License and Lesser General Public License. In August 2011, Minecraft: Pocket Edition was released as an early alpha for the Xperia Play via the Android Market, later expanding to other Android devices on 8 October 2011. The iOS version followed on 17 November 2011. A port was made available for Windows Phones shortly after Microsoft acquired Mojang. Unlike Java Edition, Pocket Edition initially focused on Minecraft's creative building and basic survival elements but lacked many features of the PC version. Bergensten confirmed on Twitter that the Pocket Edition was written in C++ rather than Java, as iOS does not support Java. On 10 December 2014, a port of Pocket Edition was released for Windows Phone 8.1. In July 2015, a port of the Pocket Edition to Windows 10 was released as the Windows 10 Edition, with full crossplay to other Pocket versions. In January 2017, Microsoft announced that it would no longer maintain the Windows Phone versions of Pocket Edition. On 20 September 2017, with the "Better Together Update", the Pocket Edition was ported to the Xbox One, and was renamed to the Bedrock Edition. The console versions of Minecraft debuted with the Xbox 360 edition, developed by 4J Studios and released on 9 May 2012. Announced as part of the Xbox Live Arcade NEXT promotion, this version introduced a redesigned crafting system, a new control interface, in-game tutorials, split-screen multiplayer, and online play via Xbox Live. Unlike the PC version, its worlds were finite, bordered by invisible walls. Initially, the Xbox 360 version resembled outdated PC versions but received updates to bring it closer to Java Edition before eventually being discontinued. The Xbox One version launched on 5 September 2014, featuring larger worlds and support for more players. Minecraft expanded to PlayStation platforms with PlayStation 3 and PlayStation 4 editions released on 17 December 2013 and 4 September 2014, respectively. Originally planned as a PS4 launch title, it was delayed before its eventual release. A PlayStation Vita version followed in October 2014. Like the Xbox versions, the PlayStation editions were developed by 4J Studios. Nintendo platforms received Minecraft: Wii U Edition on 17 December 2015, with a physical release in North America on 17 June 2016 and in Europe on 30 June. The Nintendo Switch version launched via the eShop on 11 May 2017. During a Nintendo Direct presentation on 13 September 2017, Nintendo announced that Minecraft: New Nintendo 3DS Edition, based on the Pocket Edition, would be available for download immediately after the livestream, and a physical copy available on a later date. The game is compatible only with the New Nintendo 3DS or New Nintendo 2DS XL systems and does not work with the original 3DS or 2DS systems. On 20 September 2017, the Better Together Update introduced Bedrock Edition across Xbox One, Windows 10, VR, and mobile platforms, enabling cross-play between these versions. Bedrock Edition later expanded to Nintendo Switch and PlayStation 4, with the latter receiving the update in December 2019, allowing cross-platform play for users with a free Xbox Live account. The Bedrock Edition released a native version for PlayStation 5 on 22 October 2024, while the Xbox Series X/S version launched on 17 June 2025. On 18 December 2018, the PlayStation 3, PlayStation Vita, Xbox 360, and Wii U versions of Minecraft received their final update and would later become known as "Legacy Console Editions". On 15 January 2019, the New Nintendo 3DS version of Minecraft received its final update, effectively becoming discontinued as well. An educational version of Minecraft, designed for use in schools, launched on 1 November 2016. It is available on Android, ChromeOS, iPadOS, iOS, MacOS, and Windows. On 20 August 2018, Mojang announced that it would bring Education Edition to iPadOS in Autumn 2018. It was released to the App Store on 6 September 2018. On 27 March 2019, it was announced that it would be operated by JD.com in China. On 26 June 2020, a public beta for the Education Edition was made available to Google Play Store compatible Chromebooks. The full game was released to the Google Play Store for Chromebooks on 7 August 2020. On 20 May 2016, China Edition (also known as My World) was announced as a localized edition for China, where it was released under a licensing agreement between NetEase and Mojang. The PC edition was released for public testing on 8 August 2017. The iOS version was released on 15 September 2017, and the Android version was released on 12 October 2017. The PC edition is based on the original Java Edition, while the iOS and Android mobile versions are based on the Bedrock Edition. The edition is free-to-play and had over 700 million registered accounts by September 2023. This version of Bedrock Edition is exclusive to Microsoft's Windows 10 and Windows 11 operating systems. The beta release for Windows 10 launched on the Windows Store on 29 July 2015. After nearly a year and a half in beta, Microsoft fully released the version on 19 December 2016. Called the "Ender Update", this release implemented new features to this version of Minecraft like world templates and add-on packs. On 7 June 2022, the Java and Bedrock Editions of Minecraft were merged into a single bundle for purchase on Windows; those who owned one version would automatically gain access to the other version. Both game versions would otherwise remain separate. Around 2011, prior to Minecraft's full release, Mojang collaborated with The Lego Group to create a Lego brick-based Minecraft game called Brickcraft. This would have modified the base Minecraft game to use Lego bricks, which meant adapting the basic 1×1 block to account for larger pieces typically used in Lego sets. Persson worked on an early version called "Project Rex Kwon Do", named after the character of the same name from the film Napoleon Dynamite. Although Lego approved the project and Mojang assigned two developers for six months, it was canceled due to the Lego Group's demands, according to Mojang's Daniel Kaplan. Lego considered buying Mojang to complete the game, but when Microsoft offered over $2 billion for the company, Lego stepped back, unsure of Minecraft's potential. On 26 June 2025, a build of Brickcraft dated 28 June 2012 was published on a community archive website Omniarchive. Initially, Markus Persson planned to support the Oculus Rift with a Minecraft port. However, after Facebook acquired Oculus in 2013, he abruptly canceled the plans, stating, "Facebook creeps me out." In 2016, a community-made mod, Minecraft VR, added VR support for Java Edition, followed by Vivecraft for HTC Vive. Later that year, Microsoft introduced official Oculus Rift support for Windows 10 Edition, leading to the discontinuation of the Minecraft VR mod due to trademark complaints. Vivecraft was endorsed by Minecraft VR contributors for its Rift support. Also available is a Gear VR version, titled Minecraft: Gear VR Edition. Windows Mixed Reality support was added in 2017. On 7 September 2020, Mojang Studios announced that the PlayStation 4 Bedrock version would receive PlayStation VR support later that month. In September 2024, the Minecraft team announced they would no longer support PlayStation VR, which received its final update in March 2025. Music and sound design Minecraft's music and sound effects were produced by German musician Daniel Rosenfeld, better known as C418. To create the sound effects for the game, Rosenfeld made extensive use of Foley techniques. On learning the processes for the game, he remarked, "Foley's an interesting thing, and I had to learn its subtleties. Early on, I wasn't that knowledgeable about it. It's a whole trial-and-error process. You just make a sound and eventually you go, 'Oh my God, that's it! Get the microphone!' There's no set way of doing anything at all." He reminisced on creating the in-game sound for grass blocks, stating "It turns out that to make grass sounds you don't actually walk on grass and record it, because grass sounds like nothing. What you want to do is get a VHS, break it apart, and just lightly touch the tape." According to Rosenfeld, his favorite sound to design for the game was the hisses of spiders. He elaborates, "I like the spiders. Recording that was a whole day of me researching what a spider sounds like. Turns out, there are spiders that make little screeching sounds, so I think I got this recording of a fire hose, put it in a sampler, and just pitched it around until it sounded like a weird spider was talking to you." Many of the sound design decisions by Rosenfeld were done accidentally or spontaneously. The creeper notably lacks any specific noises apart from a loud fuse-like sound when about to explode; Rosenfeld later recalled "That was just a complete accident by Markus and me [sic]. We just put in a placeholder sound of burning a matchstick. It seemed to work hilariously well, so we kept it." On other sounds, such as those of the zombie, Rosenfeld remarked, "I actually never wanted the zombies so scary. I intentionally made them sound comical. It's nice to hear that they work so well [...]." Rosenfeld remarked that the sound engine was "terrible" to work with, remembering "If you had two song files at once, it [the game engine] would actually crash. There were so many more weird glitches like that the guys never really fixed because they were too busy with the actual game and not the sound engine." The background music in Minecraft consists of instrumental ambient music. To compose the music of Minecraft, Rosenfeld used the package from Ableton Live, along with several additional plug-ins. Speaking on them, Rosenfeld said "They can be pretty much everything from an effect to an entire orchestra. Additionally, I've got some synthesizers that are attached to the computer. Like a Moog Voyager, Dave Smith Prophet 08 and a Virus TI." On 4 March 2011, Rosenfeld released a soundtrack titled Minecraft – Volume Alpha; it includes most of the tracks featured in Minecraft, as well as other music not featured in the game. Kirk Hamilton of Kotaku chose the music in Minecraft as one of the best video game soundtracks of 2011. On 9 November 2013, Rosenfeld released the second official soundtrack, titled Minecraft – Volume Beta, which included the music that was added in a 2013 "Music Update" for the game. A physical release of Volume Alpha, consisting of CDs, black vinyl, and limited-edition transparent green vinyl LPs, was issued by indie electronic label Ghostly International on 21 August 2015. On 14 August 2020, Ghostly released Volume Beta on CD and vinyl, with alternate color LPs and lenticular cover pressings released in limited quantities. The final update Rosenfeld worked on was 2018's 1.13 Update Aquatic. His music remained the only music in the game until 2020's "Nether Update", introducing pieces from Lena Raine. Since then, other composers have made contributions, including Kumi Tanioka, Samuel Åberg, Aaron Cherof, and Amos Roddy, with Raine remaining as the new primary composer. Ownership of all music besides Rosenfeld's independently released albums has been retained by Microsoft, with their label publishing all of the other artists' releases. Gareth Coker also composed some of the music for the game's mini games from the Legacy Console editions. Rosenfeld had stated his intent to create a third album of music for the game in a 2015 interview with Fact, and confirmed its existence in a 2017 tweet, stating that his work on the record as of then had tallied up to be longer than the previous two albums combined, which in total clocks in at over 3 hours and 18 minutes. However, due to licensing issues with Microsoft, the third volume has since not seen release. On 8 January 2021, Rosenfeld was asked in an interview with Anthony Fantano whether or not there was still a third volume of his music intended for release. Rosenfeld responded, saying, "I have something—I consider it finished—but things have become complicated, especially as Minecraft is now a big property, so I don't know." Reception Minecraft has received critical acclaim, with praise for the creative freedom it grants players in-game, as well as the ease of enabling emergent gameplay. Critics have expressed enjoyment in Minecraft's complex crafting system, commenting that it is an important aspect of the game's open-ended gameplay. Most publications were impressed by the game's "blocky" graphics, with IGN describing them as "instantly memorable". Reviewers also liked the game's adventure elements, noting that the game creates a good balance between exploring and building. The game's multiplayer feature has been generally received favorably, with IGN commenting that "adventuring is always better with friends". Jaz McDougall of PC Gamer said Minecraft is "intuitively interesting and contagiously fun, with an unparalleled scope for creativity and memorable experiences". It has been regarded as having introduced millions of children to the digital world, insofar as its basic game mechanics are logically analogous to computer commands. IGN was disappointed about the troublesome steps needed to set up multiplayer servers, calling it a "hassle". Critics also said that visual glitches occur periodically. Despite its release out of beta in 2011, GameSpot said the game had an "unfinished feel", adding that some game elements seem "incomplete or thrown together in haste". A review of the alpha version, by Scott Munro of the Daily Record, called it "already something special" and urged readers to buy it. Jim Rossignol of Rock Paper Shotgun also recommended the alpha of the game, calling it "a kind of generative 8-bit Lego Stalker". On 17 September 2010, gaming webcomic Penny Arcade began a series of comics and news posts about the addictiveness of the game. The Xbox 360 version was generally received positively by critics, but did not receive as much praise as the PC version. Although reviewers were disappointed by the lack of features such as mod support and content from the PC version, they acclaimed the port's addition of a tutorial and in-game tips and crafting recipes, saying that they make the game more user-friendly. The Xbox One Edition was one of the best received ports, being praised for its relatively large worlds. The PlayStation 3 Edition also received generally favorable reviews, being compared to the Xbox 360 Edition and praised for its well-adapted controls. The PlayStation 4 edition was the best received port to date, being praised for having 36 times larger worlds than the PlayStation 3 edition and described as nearly identical to the Xbox One edition. The PlayStation Vita Edition received generally positive reviews from critics but was noted for its technical limitations. The Wii U version received generally positive reviews from critics but was noted for a lack of GamePad integration. The 3DS version received mixed reviews, being criticized for its high price, technical issues, and lack of cross-platform play. The Nintendo Switch Edition received fairly positive reviews from critics, being praised, like other modern ports, for its relatively larger worlds. Minecraft: Pocket Edition initially received mixed reviews from critics. Although reviewers appreciated the game's intuitive controls, they were disappointed by the lack of content. The inability to collect resources and craft items, as well as the limited types of blocks and lack of hostile mobs, were especially criticized. After updates added more content, Pocket Edition started receiving more positive reviews. Reviewers complimented the controls and the graphics, but still noted a lack of content. Minecraft surpassed over a million purchases less than a month after entering its beta phase in early 2011. At the same time, the game had no publisher backing and has never been commercially advertised except through word of mouth, and various unpaid references in popular media such as the Penny Arcade webcomic. By April 2011, Persson estimated that Minecraft had made €23 million (US$33 million) in revenue, with 800,000 sales of the alpha version of the game, and over 1 million sales of the beta version. In November 2011, prior to the game's full release, Minecraft beta surpassed 16 million registered users and 4 million purchases. By March 2012, Minecraft had become the 6th best-selling PC game of all time. As of 10 October 2014[update], the game had sold 17 million copies on PC, becoming the best-selling PC game of all time. On 25 February 2014, the game reached 100 million registered users. By May 2019, 180 million copies had been sold across all platforms, making it the single best-selling video game of all time. The free-to-play Minecraft China version had over 700 million registered accounts by September 2023. By 2023, the game had sold over 300 million copies. As of April 2025, Minecraft has sold over 350 million copies. The Xbox 360 version of Minecraft became profitable within the first day of the game's release in 2012, when the game broke the Xbox Live sales records with 400,000 players online. Within a week of being on the Xbox Live Marketplace, Minecraft sold a million copies. GameSpot announced in December 2012 that Minecraft sold over 4.48 million copies since the game debuted on Xbox Live Arcade in May 2012. In 2012, Minecraft was the most purchased title on Xbox Live Arcade; it was also the fourth most played title on Xbox Live based on average unique users per day. As of 4 April 2014[update], the Xbox 360 version has sold 12 million copies. In addition, Minecraft: Pocket Edition has reached a figure of 21 million in sales. The PlayStation 3 Edition sold one million copies in five weeks. The release of the game's PlayStation Vita version boosted Minecraft sales by 79%, outselling both PS3 and PS4 debut releases and becoming the largest Minecraft launch on a PlayStation console. The PS Vita version sold 100,000 digital copies in Japan within the first two months of release, according to an announcement by SCE Japan Asia. By January 2015, 500,000 digital copies of Minecraft were sold in Japan across all PlayStation platforms, with a surge in primary school children purchasing the PS Vita version. As of 2022, the Vita version has sold over 1.65 million physical copies in Japan, making it the best-selling Vita game in the country. Minecraft helped improve Microsoft's total first-party revenue by $63 million for the 2015 second quarter. The game, including all of its versions, had over 112 million monthly active players by September 2019. On its 11th anniversary in May 2020, the company announced that Minecraft had reached over 200 million copies sold across platforms with over 126 million monthly active players. By April 2021, the number of active monthly users had climbed to 140 million. In July 2010, PC Gamer listed Minecraft as the fourth-best game to play at work. In December of that year, Good Game selected Minecraft as their choice for Best Downloadable Game of 2010, Gamasutra named it the eighth best game of the year as well as the eighth best indie game of the year, and Rock, Paper, Shotgun named it the "game of the year". Indie DB awarded the game the 2010 Indie of the Year award as chosen by voters, in addition to two out of five Editor's Choice awards for Most Innovative and Best Singleplayer Indie. It was also awarded Game of the Year by PC Gamer UK. The game was nominated for the Seumas McNally Grand Prize, Technical Excellence, and Excellence in Design awards at the March 2011 Independent Games Festival and won the Grand Prize and the community-voted Audience Award. At Game Developers Choice Awards 2011, Minecraft won awards in the categories for Best Debut Game, Best Downloadable Game and Innovation Award, winning every award for which it was nominated. It also won GameCity's video game arts award. On 5 May 2011, Minecraft was selected as one of the 80 games that would be displayed at the Smithsonian American Art Museum as part of The Art of Video Games exhibit that opened on 16 March 2012. At the 2011 Spike Video Game Awards, Minecraft won the award for Best Independent Game and was nominated in the Best PC Game category. In 2012, at the British Academy Video Games Awards, Minecraft was nominated in the GAME Award of 2011 category and Persson received The Special Award. In 2012, Minecraft XBLA was awarded a Golden Joystick Award in the Best Downloadable Game category, and a TIGA Games Industry Award in the Best Arcade Game category. In 2013, it was nominated as the family game of the year at the British Academy Video Games Awards. During the 16th Annual D.I.C.E. Awards, the Academy of Interactive Arts & Sciences nominated the Xbox 360 version of Minecraft for "Strategy/Simulation Game of the Year". Minecraft Console Edition won the award for TIGA Game Of The Year in 2014. In 2015, the game placed 6th on USgamer's The 15 Best Games Since 2000 list. In 2016, Minecraft placed 6th on Time's The 50 Best Video Games of All Time list. Minecraft was nominated for the 2013 Kids' Choice Awards for Favorite App, but lost to Temple Run. It was nominated for the 2014 Kids' Choice Awards for Favorite Video Game, but lost to Just Dance 2014. The game later won the award for the Most Addicting Game at the 2015 Kids' Choice Awards. In addition, the Java Edition was nominated for "Favorite Video Game" at the 2018 Kids' Choice Awards, while the game itself won the "Still Playing" award at the 2019 Golden Joystick Awards, as well as the "Favorite Video Game" award at the 2020 Kids' Choice Awards. Minecraft also won "Stream Game of the Year" at inaugural Streamer Awards in 2021. The game later garnered a Nickelodeon Kids' Choice Award nomination for Favorite Video Game in 2021, and won the same category in 2022 and 2023. At the Golden Joystick Awards 2025, it won the Still Playing Award - PC and Console. Minecraft has been subject to several notable controversies. In June 2014, Mojang announced that it would begin enforcing the portion of Minecraft's end-user license agreement (EULA) which prohibits servers from giving in-game advantages to players in exchange for donations or payments. Spokesperson Owen Hill stated that servers could still require players to pay a fee to access the server and could sell in-game cosmetic items. The change was supported by Persson, citing emails he received from parents of children who had spent hundreds of dollars on servers. The Minecraft community and server owners protested, arguing that the EULA's terms were more broad than Mojang was claiming, that the crackdown would force smaller servers to shut down for financial reasons, and that Mojang was suppressing competition for its own Minecraft Realms subscription service. The controversy contributed to Notch's decision to sell Mojang. In 2020, Mojang announced an eventual change to the Java Edition to require a login from a Microsoft account rather than a Mojang account, the latter of which would be sunsetted. This also required Java Edition players to create Xbox network Gamertags. Mojang defended the move to Microsoft accounts by saying that improved security could be offered, including two-factor authentication, blocking cyberbullies in chat, and improved parental controls. The community responded with intense backlash, citing various technical difficulties encountered in the process and how account migration would be mandatory, even for those who do not play on servers. As of 10 March 2022, Microsoft required that all players migrate in order to maintain access the Java Edition of Minecraft. Mojang announced a deadline of 19 September 2023 for account migration, after which all legacy Mojang accounts became inaccessible and unable to be migrated. In June 2022, Mojang added a player-reporting feature in Java Edition. Players could report other players on multiplayer servers for sending messages prohibited by the Xbox Live Code of Conduct; report categories included profane language,[l] substance abuse, hate speech, threats of violence, and nudity. If a player was found to be in violation of Xbox Community Standards, they would be banned from all servers for a specific period of time or permanently. The update containing the report feature (1.19.1) was released on 27 July 2022. Mojang received substantial backlash and protest from community members, one of the most common complaints being that banned players would be forbidden from joining any server, even private ones. Others took issue to what they saw as Microsoft increasing control over its player base and exercising censorship, leading some to start a hashtag #saveminecraft and dub the version "1.19.84", a reference to the dystopian novel Nineteen Eighty-Four. The "Mob Vote" was an online event organized by Mojang in which the Minecraft community voted between three original mob concepts; initially, the winning mob was to be implemented in a future update, while the losing mobs were scrapped, though after the first mob vote this was changed, and losing mobs would now have a chance to come to the game in the future. The first Mob Vote was held during Minecon Earth 2017 and became an annual event starting with Minecraft Live 2020. The Mob Vote was often criticized for forcing players to choose one mob instead of implementing all three, causing divisions and flaming within the community, and potentially allowing internet bots and Minecraft content creators with large fanbases to conduct vote brigading. The Mob Vote was also blamed for a perceived lack of new content added to Minecraft since Microsoft's acquisition of Mojang in 2014. The 2023 Mob Vote featured three passive mobs—the crab, the penguin, and the armadillo—with voting scheduled to start on 13 October. In response, a Change.org petition was created on 6 October, demanding that Mojang eliminate the Mob Vote and instead implement all three mobs going forward. The petition received approximately 445,000 signatures by 13 October and was joined by calls to boycott the Mob Vote, as well as a partially tongue-in-cheek "revolutionary" propaganda campaign in which sympathizers created anti-Mojang and pro-boycott posters in the vein of real 20th century propaganda posters. Mojang did not release an official response to the boycott, and the Mob Vote otherwise proceeded normally, with the armadillo winning the vote. In September 2024, as part of a blog post detailing their future plans for Minecraft's development, Mojang announced the Mob Vote would be retired. Cultural impact In September 2019, The Guardian classified Minecraft as the best video game of the 21st century to date, and in November 2019, Polygon called it the "most important game of the decade" in its 2010s "decade in review". In June 2020, Minecraft was inducted into the World Video Game Hall of Fame. Minecraft is recognized as one of the first successful games to use an early access model to draw in sales prior to its full release version to help fund development. As Minecraft helped to bolster indie game development in the early 2010s, it also helped to popularize the use of the early access model in indie game development. Social media sites such as YouTube, Facebook, and Reddit have played a significant role in popularizing Minecraft. Research conducted by the Annenberg School for Communication at the University of Pennsylvania showed that one-third of Minecraft players learned about the game via Internet videos. In 2010, Minecraft-related videos began to gain influence on YouTube, often made by commentators. The videos usually contain screen-capture footage of the game and voice-overs. Common coverage in the videos includes creations made by players, walkthroughs of various tasks, and parodies of works in popular culture. By May 2012, over four million Minecraft-related YouTube videos had been uploaded. The game would go on to be a prominent fixture within YouTube's gaming scene during the entire 2010s; in 2014, it was the second-most searched term on the entire platform. By 2018, it was still YouTube's biggest game globally. Some popular commentators have received employment at Machinima, a now-defunct gaming video company that owned a highly watched entertainment channel on YouTube. The Yogscast is a British company that regularly produces Minecraft videos; their YouTube channel has attained billions of views, and their panel at Minecon 2011 had the highest attendance. Another well-known YouTube personality is Jordan Maron, known online as CaptainSparklez, who has also created many Minecraft music parodies, including "Revenge", a parody of Usher's "DJ Got Us Fallin' in Love". Minecraft's popularity on YouTube was described by Polygon as quietly dominant, although in 2019, thanks in part to PewDiePie's playthroughs of the game, Minecraft experienced a visible uptick in popularity on the platform. Longer-running series include Far Lands or Bust, dedicated to reaching the obsolete "Far Lands" glitch by foot on an older version of the game. YouTube announced that on 14 December 2021 that the total amount of Minecraft-related views on the website had exceeded one trillion. Minecraft has been referenced by other video games, such as Torchlight II, Team Fortress 2, Borderlands 2, Choplifter HD, Super Meat Boy, The Elder Scrolls V: Skyrim, The Binding of Isaac, The Stanley Parable, and FTL: Faster Than Light. Minecraft is officially represented in downloadable content for the crossover fighter Super Smash Bros. Ultimate, with Steve as a playable character with a moveset including references to building, crafting, and redstone, alongside an Overworld-themed stage. It was also referenced by electronic music artist Deadmau5 in his performances. The game is also referenced heavily in "Informative Murder Porn", the second episode of the seventeenth season of the animated television series South Park. In 2025, A Minecraft Movie was released. It made $313 million in the box office in the first week, a record-breaking opening for a video game adaptation. Minecraft has been noted as a cultural touchstone for Generation Z, as many of the generation's members played the game at a young age. The possible applications of Minecraft have been discussed extensively, especially in the fields of computer-aided design (CAD) and education. In a panel at Minecon 2011, a Swedish developer discussed the possibility of using the game to redesign public buildings and parks, stating that rendering using Minecraft was much more user-friendly for the community, making it easier to envision the functionality of new buildings and parks. In 2012, a member of the Human Dynamics group at the MIT Media Lab, Cody Sumter, said: "Notch hasn't just built a game. He's tricked 40 million people into learning to use a CAD program." Various software has been developed to allow virtual designs to be printed using professional 3D printers or personal printers such as MakerBot and RepRap. In September 2012, Mojang began the Block by Block project in cooperation with UN Habitat to create real-world environments in Minecraft. The project allows young people who live in those environments to participate in designing the changes they would like to see. Using Minecraft, the community has helped reconstruct the areas of concern, and citizens are invited to enter the Minecraft servers and modify their own neighborhood. Carl Manneh, Mojang's managing director, called the game "the perfect tool to facilitate this process", adding "The three-year partnership will support UN-Habitat's Sustainable Urban Development Network to upgrade 300 public spaces by 2016." Mojang signed Minecraft building community, FyreUK, to help render the environments into Minecraft. The first pilot project began in Kibera, one of Nairobi's informal settlements and is in the planning phase. The Block by Block project is based on an earlier initiative started in October 2011, Mina Kvarter (My Block), which gave young people in Swedish communities a tool to visualize how they wanted to change their part of town. According to Manneh, the project was a helpful way to visualize urban planning ideas without necessarily having a training in architecture. The ideas presented by the citizens were a template for political decisions. In April 2014, the Danish Geodata Agency generated all of Denmark in fullscale in Minecraft based on their own geodata. This is possible because Denmark is one of the flattest countries with the highest point at 171 meters (ranking as the country with the 30th smallest elevation span), where the limit in default Minecraft was around 192 meters above in-game sea level when the project was completed. Taking advantage of the game's accessibility where other websites are censored, the non-governmental organization Reporters Without Borders has used an open Minecraft server to create the Uncensored Library, a repository within the game of journalism by authors from countries (including Egypt, Mexico, Russia, Saudi Arabia and Vietnam) who have been censored and arrested, such as Jamal Khashoggi. The neoclassical virtual building was created over about 250 hours by an international team of 24 people. Despite its unpredictable nature, Minecraft speedrunning, where players time themselves from spawning into a new world to reaching The End and defeating the Ender Dragon boss, is popular. Some speedrunners use a combination of mods, external programs, and debug menus, while other runners play the game in a more vanilla or more consistency-oriented way. Minecraft has been used in educational settings through initiatives such as MinecraftEdu, founded in 2011 to make the game affordable and accessible for schools in collaboration with Mojang. MinecraftEdu provided features allowing teachers to monitor student progress, including screenshot submissions as evidence of lesson completion, and by 2012 reported that approximately 250,000 students worldwide had access to the platform. Mojang also developed Minecraft: Education Edition with pre-built lesson plans for up to 30 students in a closed environment. Educators have used Minecraft to teach subjects such as history, language arts, and science through custom-built environments, including reconstructions of historical landmarks and large-scale models of biological structures such as animal cells. The introduction of redstone blocks enabled the construction of functional virtual machines such as a hard drive and an 8-bit computer. Mods have been created to use these mechanics for teaching programming. In 2014, the British Museum announced a project to reproduce its building and exhibits in Minecraft in collaboration with the public. Microsoft and Code.org have offered Minecraft-based tutorials and activities designed to teach programming, reporting by 2018 that more than 85 million children had used their resources. In 2025, the Musée de Minéralogie in Paris held a temporary exhibition titled "Minerals in Minecraft." Following the initial surge in popularity of Minecraft in 2010, other video games were criticised for having various similarities to Minecraft, and some were described as being "clones", often due to a direct inspiration from Minecraft, or a superficial similarity. Examples include Ace of Spades, CastleMiner, CraftWorld, FortressCraft, Terraria, BlockWorld 3D, Total Miner, and Luanti (formerly Minetest). David Frampton, designer of The Blockheads, reported that one failure of his 2D game was the "low resolution pixel art" that too closely resembled the art in Minecraft, which resulted in "some resistance" from fans. A homebrew adaptation of the alpha version of Minecraft for the Nintendo DS, titled DScraft, has been released; it has been noted for its similarity to the original game considering the technical limitations of the system. In response to Microsoft's acquisition of Mojang and their Minecraft IP, various developers announced further clone titles developed specifically for Nintendo's consoles, as they were the only major platforms not to officially receive Minecraft at the time. These clone titles include UCraft (Nexis Games), Cube Life: Island Survival (Cypronia), Discovery (Noowanda), Battleminer (Wobbly Tooth Games), Cube Creator 3D (Big John Games), and Stone Shire (Finger Gun Games). Despite this, the fears of fans were unfounded, with official Minecraft releases on Nintendo consoles eventually resuming. Markus Persson made another similar game, Minicraft, for a Ludum Dare competition in 2011. In 2025, Persson announced through a poll on his X account that he was considering developing a spiritual successor to Minecraft. He later clarified that he was "100% serious", and that he had "basically announced Minecraft 2". Within days, however, Persson cancelled the plans after speaking to his team. In November 2024, artificial intelligence companies Decart and Etched released Oasis, an artificially generated version of Minecraft, as a proof of concept. Every in-game element is completely AI-generated in real time and the model does not store world data, leading to "hallucinations" such as items and blocks appearing that were not there before. In January 2026, indie game developer Unomelon announced that their voxel sandbox game Allumeria would be playable in Steam Next Fest that year. On 10 February, Mojang issued a DMCA takedown of Allumeria on Steam through Valve, alleging the game was infringing on Minecraft's copyright. Some reports suggested that the takedown may have used an automatic AI copyright claiming service. The DMCA was later withdrawn. Minecon was an annual official fan convention dedicated to Minecraft. The first full Minecon was held in November 2011 at the Mandalay Bay Hotel and Casino in Las Vegas. The event included the official launch of Minecraft; keynote speeches, including one by Persson; building and costume contests; Minecraft-themed breakout classes; exhibits by leading gaming and Minecraft-related companies; commemorative merchandise; and autograph and picture times with Mojang employees and well-known contributors from the Minecraft community. In 2016, Minecon was held in-person for the last time, with the following years featuring annual "Minecon Earth" livestreams on minecraft.net and YouTube instead. These livestreams, later rebranded to "Minecraft Live", included the mob/biome votes, and announcements of new game updates. In 2025, "Minecraft Live" became a biannual event as part of Minecraft's changing update schedule.[citation needed] Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Child_grooming] | [TOKENS: 1959] |
Contents Sexual grooming Sexual grooming is the action or behavior used to establish an emotional connection with a vulnerable person under the age of consent – and sometimes the victim's family, to lower their inhibitions with the objective of sexual abuse. It can occur in various settings, including online, in person, and through other means of communication. Children who are groomed may experience mental health issues, including "anxiety, depression, post-traumatic stress, and suicidal thoughts". History and recognition Before the term "grooming" was associated with grooming a child for sexual abuse, it had come to have a meaning of mentorship, coaching, or preparing someone for leadership. From 1975 to 1985, law enforcement in the United States became increasingly aware of child sexual abuse that happened to children from outside their family, committed by those who were not strangers. Previously, the focus of law enforcement had been on "stranger danger" and those who used threats of violence to ensure compliance from their victims. In these newly recognized sexual abuse cases, children were manipulated with a "combination of attention, affection, kindness, gifts, alcohol, drugs, money, and privileges". While there are examples before this time where the pattern was recognized, it was during this decade that the FBI became aware of the pattern and criminal investigations were first taken seriously in the United States. There was also growing awareness that offenders joined youth-serving organizations to gain access to potential victims. As an example, a 1977 study used the terminology "pressured sexual contacts" and "forced sex contacts" to distinguish two types of offenders. Sex-pressure offenses had a lack of physical force and behavior that was counter-aggressive, using "persuasion of reward, attention, affection, money, gifts, or entrapment". "Sex-force offenses" used the threat of harm or physical force, such as "intimidation, verbal threat, restraint, manipulation, and physical strength". Ken Lanning is credited with being one of the first professionals to use the term "grooming". He recalls it being used in conversations between law enforcement professionals, and pinpoints the first known written description of the process of child grooming to a 1979 book written by Nicholas Groth, and the first printed use of the word grooming to a 1984 article by Jon Conte. At the beginning of its use, both grooming and seduction were being used to describe this type of non-violent offender, and Lanning recalls using both terms interchangeably. A January 1984 FBI Law Enforcement Bulletin used "seduction" and being "seduced" to describe the activity of non-violent offenders. By 1985, the Chicago Tribune had used the term, reporting "These 'friendly molesters' become acquainted with their targeted victim, gaining their trust while secretly grooming the child as a sexual partner." In the 1980s, the public in the United States became increasingly aware of child sexual abuse through the nursery school cases and abuse in religious settings. During the 1990s, the term grooming was increasingly used to replace "seduction" as the most commonly used term. However, there was not "one official, legal, mental health, or even lay definition" of grooming. Growing awareness of chat rooms being used by pedophiles to target victims came to public notice, and the use of "grooming" to mean "to win the confidence of (a victim) in order to commit sexual assault on him or her" became mainstream. In academia, the description of grooming strategies in online cases became distinct from the descriptions of pre-Internet grooming strategies. In 2008, a BBC report stated that "grooming" had taken on a pejorative meaning; no longer associated with animal care or mentoring, it had become associated with pedophiles and pedophilia. This caused outrage when the term "groomed" was used to describe the behavior of someone who had obtained leaked documents from a civil servant. The news report mentioned other uses of the term "groom" that also had negative connotation, such as "groomed for terrorism" or "groomed to become suicide bombers". A 2022 report by the Christian Monitor, reported that the word "grooming" was now seen as "sinister". Instead of meaning "to prepare as a political candidate ... to prepare or coach for a career", the term had shifted in public discourse to mean "to befriend or influence (a child), now esp. via the internet, in preparation for future sexual abuse". Grooming is also increasingly used in political commentary to mean “indoctrination” or “brainwashing". Patterns To establish a good relationship with a child and the child's family, child groomers might do several things: they might try to gain the child's or parents' trust by befriending them, with the goal of easy access to the child. A trusting relationship with the family means the child's parents are less likely to believe potential accusations. Child groomers might look for opportunities to have time alone with the child, which can be done by offering to babysit; the groomers may also invite the child for sleepovers, for opportunistic bed sharing. They might give gifts or money to the child in exchange for sexual contact, or simply because they like or love them. Commonly, they show pornography to the child, or talk about sexual topics with the child, hoping to make it easy for the child to accept such acts, thus normalizing the behavior. They may also engage in hugging, kissing, or other physical contact, even when the child does not want it. When grooming techniques are successful, the resulting compliance of the child can be mis-interpreted as consent; and the child treated as if they were not a victim of crime. When the behavior is considered criminal, it can still be perceived as a lesser offense. Some offenders prefer sexual gratification from less obvious types of behaviors, and grooming behaviors in and of themselves are the goal as they provide a chance to engage in a paraphilia. Signs that characterize child groomers include: a person who tries to communicate with a child online or in person in secret, outside the knowledge of the child's parents or guardians; a person who attempts to isolate a child from their friends or family, or who discourages the child from spending time with others; or a person who asks a child to keep secrets or who makes the child feel like they are special or important in a way that is inappropriate. Impact on victims Grooming has devastating impacts on victims, damaging their sense of self, eroding their ability to trust others, and severely impacting mental health. Children who are groomed may feel they are to blame for their abuse, and have difficulty placing blame on the perpetrator. Survivors may perceive aspects of human connection as threat cues, and thus may find it difficult to fully engage mentally with simple positive interactions, such as affirmation or compliments.[citation needed] Many grooming tactics involve isolating a victim through fostering distrust or otherwise sabotaging other close relationships. This directly weakens the potential support network to process traumatic experiences, increasing the risk of long-term psychological ramifications. Victims can be left having been both isolated from existing social connections, and finding it difficult to form new ones.[citation needed] Criminal offences Because sexual grooming is a non-violent and non-threatening form of child sexual abuse, it includes behaviors that do not appear inappropriate on the surface, as the behavior is designed to control and conceal a sexual relationship with the victim. The behavior becomes a criminal act in the United States when one tries to "persuade, induce, entice, or coerce" a minor to engage in sexual activity. As awareness of nonviolent offenders has grown, States like Illinois have passed legislation that bans enticement similar to the federal law. Other example child sexual abuse offenses include "Solicitation of a Minor," and "Indecent Liberties with a Child". In Kansas, "Aggravated Indecent Liberties with a Child" is used when an abuser has sex with the child. In Arkansas, the statute is "Sexual indecency with a child". Related topics In some contexts, such as the UK grooming gangs scandal, the behavior of Loverboy or Romeo Pimps has been described as 'grooming' by the media. Loverboy is a method used to lure young people into sexual exploitation and prostitution, where the target is initially approached romantically by the exploiter. The goal is to exploit the target, usually in the sex industry. Unlike non-violent offenders, once ensnared, victims face blackmail and violence to maintain their compliance. Grooming is also used to describe befriending a child on the Internet, in preparation for future sexual abuse. Sexual predation of children on the Internet mostly consists of adults using the Internet to meet and seduce underage adolescents into sexual encounters. Some abusers (sometimes posing as children themselves) chat with children online and make arrangements to meet with them in person. Internet initiated sex crimes against people under the age of consent are most commonly commited against the 13–17 age group (99% of cases), and particularly 13–14 (48%). The majority of targeted children are girls, and most victimization occurs with mobile-phone support. Children and teenagers who are highly curious and high-sensation-seeking are at higher risk than others. Pedophiles and predators use online grooming to carry out cybersex trafficking crimes. After the pedophile gains the trust from a local cybersex trafficker, often a parent or neighbor of the victim, the online sexual exploitation will take place. References Further reading See also External links |
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[SOURCE: https://en.wikipedia.org/wiki/Lattice_graph] | [TOKENS: 641] |
Contents Lattice graph In graph theory, a lattice graph, mesh graph, or grid graph is a graph whose drawing, embedded in some Euclidean space R n {\displaystyle \mathbb {R} ^{n}} , forms a regular tiling. This implies that the group of bijective transformations that send the graph to itself is a lattice in the group-theoretical sense. Typically, no clear distinction is made between such a graph in the more abstract sense of graph theory, and its drawing in space (often the plane or 3D space). This type of graph may more shortly be called just a lattice, mesh, or grid. Moreover, these terms are also commonly used for a finite section of the infinite graph, as in "an 8 × 8 square grid". The term lattice graph has also been given in the literature to various other kinds of graphs with some regular structure, such as the Cartesian product of a number of complete graphs. Square grid graph A common type of lattice graph (known under different names, such as grid graph or square grid graph) is the graph whose vertices correspond to the points in the plane with integer coordinates, x-coordinates being in the range 1, ..., n, y-coordinates being in the range 1, ..., m, and two vertices being connected by an edge whenever the corresponding points are at distance one. In other words, it is the unit distance graph for the integer points in a rectangle with sides parallel to the axes. A square grid graph is a Cartesian product of graphs, namely, of two path graphs with n − 1 and m − 1 edges. Since a path graph is a median graph, the latter fact implies that the square grid graph is also a median graph. All square grid graphs are bipartite, which is easily verified by the fact that one can color the vertices in a checkerboard fashion. A path graph is a grid graph on the 1 × n {\displaystyle 1\times n} grid. A 2 × 2 {\displaystyle 2\times 2} grid graph is a 4-cycle. Every planar graph H is a minor of the h × h grid, where h = 2 | V ( H ) | + 4 | E ( H ) | {\displaystyle h=2|V(H)|+4|E(H)|} . Grid graphs are fundamental objects in the theory of graph minors because of the grid exclusion theorem. They play a major role in bidimensionality theory. Other kinds A triangular grid graph is a graph that corresponds to a triangular grid. A Hanan grid graph for a finite set of points in the plane is produced by the grid obtained by intersections of all vertical and horizontal lines through each point of the set. The rook's graph (the graph that represents all legal moves of the rook chess piece on a chessboard) is also sometimes called the lattice graph, although this graph is different from the lattice graph described here because all points in one row or column are adjacent. The valid moves of the fairy chess piece the wazir form a square lattice graph. See also References |
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[SOURCE: https://en.wikipedia.org/wiki/Chaos_Theory] | [TOKENS: 8588] |
Contents Chaos theory Chaos theory is an interdisciplinary area of scientific study and branch of mathematics. It focuses on underlying patterns and deterministic laws of dynamical systems that are highly sensitive to initial conditions. These were once thought to have completely random states of disorder and irregularities. Chaos theory states that within the apparent randomness of chaotic complex systems, there are underlying patterns, interconnection, constant feedback loops, repetition, self-similarity, fractals and self-organization. The butterfly effect, an underlying principle of chaos, describes how a small change in one state of a deterministic nonlinear system can result in large differences in a later state (meaning there is sensitive dependence on initial conditions). A metaphor for this behavior is that a butterfly flapping its wings in Brazil can cause or prevent a tornado in Texas.: 181–184 Small differences in initial conditions, such as those due to errors in measurements or due to rounding errors in numerical computation, can yield widely diverging outcomes for such dynamic systems, rendering long-term prediction of their behavior impossible in general. This can happen even though these systems are deterministic, meaning that their future behavior follows a unique evolution and is fully determined by their initial conditions, with no random elements involved. In other words, despite the deterministic nature of these systems, this does not make them predictable. This behavior is known as deterministic chaos, or simply chaos. The theory was summarized by Edward Lorenz as: Chaos: When the present determines the future but the approximate present does not approximately determine the future. Chaotic behavior exists in many natural systems, including fluid flow, heartbeat irregularities, weather and climate. It also occurs spontaneously in some systems with artificial components, such as road traffic. This behavior can be studied through the analysis of a chaotic mathematical model or through analytical techniques such as recurrence plots and Poincaré maps. Chaos theory has applications in a variety of disciplines, including meteorology, anthropology, sociology, environmental science, computer science, engineering, economics, ecology, and pandemic crisis management. The theory formed the basis for such fields of study as complex dynamical systems, edge of chaos theory and self-assembly processes. Introduction Chaos theory concerns deterministic systems which are predictable for some amount of time and then appear to become random. The amount of time for which the behavior of a chaotic system can be effectively predicted depends on three things: How much uncertainty can be tolerated in the forecast, how accurately its current state can be measured, and a time scale depending on the dynamics of the system, called the Lyapunov time. Some examples of Lyapunov times are: Chaotic electrical circuits, about 1 millisecond; weather systems, a few days (unproven); the inner solar system, 4 to 5 million years. In chaotic systems, the uncertainty in a forecast increases exponentially with elapsed time. Hence, mathematically, doubling the forecast time more than squares the proportional uncertainty in the forecast. This means, in practice, a meaningful prediction cannot be made over an interval of more than two or three times the Lyapunov time. When meaningful predictions cannot be made, the system appears random. Chaotic dynamics In common usage, "chaos" means "a state of disorder". However, in chaos theory, the term is defined more precisely. Although no universally accepted mathematical definition of chaos exists, a commonly used definition, originally formulated by Robert L. Devaney, says that to classify a dynamical system as chaotic, it must have these properties: In some cases, the last two properties above have been shown to actually imply sensitivity to initial conditions. In the discrete-time case, this is true for all continuous maps on metric spaces. In these cases, while it is often the most practically significant property, "sensitivity to initial conditions" need not be stated in the definition. If attention is restricted to intervals, the second property implies the other two. An alternative and a generally weaker definition of chaos uses only the first two properties in the above list. Sensitivity to initial conditions means that each point in a chaotic system is arbitrarily closely approximated by other points that have significantly different future paths or trajectories. Thus, an arbitrarily small change or perturbation of the current trajectory may lead to significantly different future behavior. Sensitivity to initial conditions is popularly known as the "butterfly effect", so-called because of the title of a paper given by Edward Lorenz in 1972 to the American Association for the Advancement of Science in Washington, D.C., entitled Predictability: Does the Flap of a Butterfly's Wings in Brazil set off a Tornado in Texas?. The flapping wing represents a small change in the initial condition of the system, which causes a chain of events that prevents the predictability of large-scale phenomena. Had the butterfly not flapped its wings, the trajectory of the overall system could have been vastly different. As suggested in Lorenz's book entitled The Essence of Chaos, published in 1993,: 8 "sensitive dependence can serve as an acceptable definition of chaos". In the same book, Lorenz defined the butterfly effect as: "The phenomenon that a small alteration in the state of a dynamical system will cause subsequent states to differ greatly from the states that would have followed without the alteration.": 23 The above definition is consistent with the sensitive dependence of solutions on initial conditions (SDIC). An idealized skiing model was developed to illustrate the sensitivity of time-varying paths to initial positions.: 189–204 A predictability horizon can be determined before the onset of SDIC (i.e., prior to significant separations of initial nearby trajectories). A consequence of sensitivity to initial conditions is that if we start with a limited amount of information about the system (as is usually the case in practice), then beyond a certain time, the system would no longer be predictable. This is most prevalent in the case of weather, which is generally predictable only about a week ahead. This does not mean that one cannot assert anything about events far in the future - only that some restrictions on the system are present. For example, we know that the temperature of the surface of the earth will not naturally reach 100 °C (212 °F) or fall below −130 °C (−202 °F) on earth (during the current geologic era), but we cannot predict exactly which day will have the hottest temperature of the year. In more mathematical terms, the Lyapunov exponent measures the sensitivity to initial conditions, in the form of rate of exponential divergence from the perturbed initial conditions. More specifically, given two starting trajectories in the phase space that are infinitesimally close, with initial separation δ Z 0 {\displaystyle \delta \mathbf {Z} _{0}} , the two trajectories end up diverging at a rate given by where t {\displaystyle t} is the time and λ {\displaystyle \lambda } is the Lyapunov exponent. The rate of separation depends on the orientation of the initial separation vector, so a whole spectrum of Lyapunov exponents can exist. The number of Lyapunov exponents is equal to the number of dimensions of the phase space, though it is common to just refer to the largest one. For example, the maximal Lyapunov exponent (MLE) is most often used, because it determines the overall predictability of the system. A positive MLE, coupled with the solution's boundedness, is usually taken as an indication that the system is chaotic. In addition to the above property, other properties related to sensitivity of initial conditions also exist. These include, for example, measure-theoretical mixing (as discussed in ergodic theory) and properties of a K-system. A chaotic system may have sequences of values for the evolving variable that exactly repeat themselves, giving periodic behavior starting from any point in that sequence. However, such periodic sequences are repelling rather than attracting, meaning that if the evolving variable is outside the sequence, however close, it will not enter the sequence and in fact, will diverge from it. Thus for almost all initial conditions, the variable evolves chaotically with non-periodic behavior. Topological mixing (or the weaker condition of topological transitivity) means that the system evolves over time so that any given region or open set of its phase space eventually overlaps with any other given region. This mathematical concept of "mixing" corresponds to the standard intuition, and the mixing of colored dyes or fluids is an example of a chaotic system. Topological mixing is often omitted from popular accounts of chaos, which equate chaos with only sensitivity to initial conditions. However, sensitive dependence on initial conditions alone does not give chaos. For example, consider the simple dynamical system produced by repeatedly doubling an initial value. This system has sensitive dependence on initial conditions everywhere, since any pair of nearby points eventually becomes widely separated. However, this example has no topological mixing, and therefore has no chaos. Indeed, it has extremely simple behavior: all points except 0 tend to positive or negative infinity. A map f : X → X {\displaystyle f:X\to X} is said to be topologically transitive if for any pair of non-empty open sets U , V ⊂ X {\displaystyle U,V\subset X} , there exists k > 0 {\displaystyle k>0} such that f k ( U ) ∩ V ≠ ∅ {\displaystyle f^{k}(U)\cap V\neq \emptyset } . Topological transitivity is a weaker version of topological mixing. Intuitively, if a map is topologically transitive then given a point x and a region V, there exists a point y near x whose orbit passes through V. This implies that it is impossible to decompose the system into two open sets. An important related theorem is the Birkhoff Transitivity Theorem. It is easy to see that the existence of a dense orbit implies topological transitivity. The Birkhoff Transitivity Theorem states that if X is a second countable, complete metric space, then topological transitivity implies the existence of a dense set of points in X that have dense orbits. For a chaotic system to have dense periodic orbits means that every point in the space is approached arbitrarily closely by periodic orbits. The one-dimensional logistic map defined by x → 4 x (1 – x) is one of the simplest systems with density of periodic orbits. For example, 5 − 5 8 {\displaystyle {\tfrac {5-{\sqrt {5}}}{8}}} → 5 + 5 8 {\displaystyle {\tfrac {5+{\sqrt {5}}}{8}}} → 5 − 5 8 {\displaystyle {\tfrac {5-{\sqrt {5}}}{8}}} (or approximately 0.3454915 → 0.9045085 → 0.3454915) is an (unstable) orbit of period 2, and similar orbits exist for periods 4, 8, 16, etc. (indeed, for all the periods specified by Sharkovskii's theorem). Sharkovskii's theorem is the basis of the Li and Yorke (1975) proof that any continuous one-dimensional system that exhibits a regular cycle of period three will also display regular cycles of every other length, as well as completely chaotic orbits. Some dynamical systems, like the one-dimensional logistic map defined by x → 4 x (1 – x), are chaotic everywhere, but in many cases chaotic behavior is found only in a subset of phase space. The cases of most interest arise when the chaotic behavior takes place on an attractor, since then a large set of initial conditions leads to orbits that converge to this chaotic region. An easy way to visualize a chaotic attractor is to start with a point in the basin of attraction of the attractor, and then simply plot its subsequent orbit. Because of the topological transitivity condition, this is likely to produce a picture of the entire final attractor, and indeed both orbits shown in the figure on the right give a picture of the general shape of the Lorenz attractor. This attractor results from a simple three-dimensional model of the Lorenz weather system. The Lorenz attractor is perhaps one of the best-known chaotic system diagrams, probably because it is not only one of the first, but it is also one of the most complex, and as such gives rise to a very interesting pattern that, with a little imagination, looks like the wings of a butterfly. Unlike fixed-point attractors and limit cycles, the attractors that arise from chaotic systems, known as strange attractors, have great detail and complexity. Strange attractors occur in both continuous dynamical systems (such as the Lorenz system) and in some discrete systems (such as the Hénon map). Other discrete dynamical systems have a repelling structure called a Julia set, which forms at the boundary between basins of attraction of fixed points. Julia sets can be thought of as strange repellers. Both strange attractors and Julia sets typically have a fractal structure, and the fractal dimension can be calculated for them. In contrast to single type chaotic solutions, studies using Lorenz models have emphasized the importance of considering various types of solutions. For example, coexisting chaotic and non-chaotic may appear within the same model (e.g., the double pendulum system) using the same modeling configurations but different initial conditions. The findings of attractor coexistence, obtained from classical and generalized Lorenz models, suggested a revised view that "the entirety of weather possesses a dual nature of chaos and order with distinct predictability", in contrast to the conventional view of "weather is chaotic". Discrete chaotic systems, such as the logistic map, can exhibit strange attractors whatever their dimensionality. In contrast, for continuous dynamical systems, the Poincaré–Bendixson theorem shows that a strange attractor can only arise in three or more dimensions. Finite-dimensional linear systems are never chaotic; for a dynamical system to display chaotic behavior, it must be either nonlinear or infinite-dimensional. The Poincaré–Bendixson theorem states that a two-dimensional differential equation has very regular behavior. The Lorenz attractor discussed below is generated by a system of three differential equations such as: where x {\displaystyle x} , y {\displaystyle y} , and z {\displaystyle z} make up the system state, t {\displaystyle t} is time, and σ {\displaystyle \sigma } , ρ {\displaystyle \rho } , β {\displaystyle \beta } are the system parameters. Five of the terms on the right hand side are linear, while two are quadratic; a total of seven terms. Another well-known chaotic attractor is generated by the Rössler equations, which have only one nonlinear term out of seven. Sprott found a three-dimensional system with just five terms, that had only one nonlinear term, which exhibits chaos for certain parameter values. Zhang and Heidel showed that, at least for dissipative and conservative quadratic systems, three-dimensional quadratic systems with only three or four terms on the right-hand side cannot exhibit chaotic behavior. The reason is, simply put, that solutions to such systems are asymptotic to a two-dimensional surface and therefore solutions are well behaved. While the Poincaré–Bendixson theorem shows that a continuous dynamical system on the Euclidean plane cannot be chaotic, two-dimensional continuous systems with non-Euclidean geometry can still exhibit some chaotic properties. The above set of three ordinary differential equations has been referred to as the three-dimensional Lorenz model. Since 1963, higher-dimensional Lorenz models have been developed in numerous studies for examining the impact of an increased degree of nonlinearity, as well as its collective effect with heating and dissipations, on solution stability. Perhaps surprisingly, chaos may occur also in linear systems, provided they are infinite dimensional. A theory of linear chaos is being developed in functional analysis. Quantum mechanics is also often considered as a prime example of linear non chaotic theory, that dampens out chaotic behaviour in the same manner that viscosity dampens out turbulence, this is actually not the case for quantum mechanical systems with infinite degrees of freedom, such as strongly correlated systems that do exhibit forms of nano scale turbulence. Other characteristics of Chaos The straightforward generalization of coupled discrete maps is based upon convolution integral which mediates interaction between spatially distributed maps: ψ n + 1 ( r → , t ) = ∫ K ( r → − r → , , t ) f [ ψ n ( r → , , t ) ] d r → , {\displaystyle \psi _{n+1}({\vec {r}},t)=\int K({\vec {r}}-{\vec {r}}^{,},t)f[\psi _{n}({\vec {r}}^{,},t)]d{\vec {r}}^{,}} , where kernel K ( r → − r → , , t ) {\displaystyle K({\vec {r}}-{\vec {r}}^{,},t)} is propagator derived as Green function of a relevant physical system, f [ ψ n ( r → , t ) ] {\displaystyle f[\psi _{n}({\vec {r}},t)]} might be logistic map alike ψ → G ψ [ 1 − tanh ( ψ ) ] {\displaystyle \psi \rightarrow G\psi [1-\tanh(\psi )]} or complex map. For examples of complex maps the Julia set f [ ψ ] = ψ 2 {\displaystyle f[\psi ]=\psi ^{2}} or Ikeda map ψ n + 1 = A + B ψ n e i ( | ψ n | 2 + C ) {\displaystyle \psi _{n+1}=A+B\psi _{n}e^{i(|\psi _{n}|^{2}+C)}} may serve. When wave propagation problems at distance L = c t {\displaystyle L=ct} with wavelength λ = 2 π / k {\displaystyle \lambda =2\pi /k} are considered the kernel K {\displaystyle K} may have a form of Green function for Schrödinger equation:. K ( r → − r → , , L ) = i k exp [ i k L ] 2 π L exp [ i k | r → − r → , | 2 2 L ] {\displaystyle K({\vec {r}}-{\vec {r}}^{,},L)={\frac {ik\exp[ikL]}{2\pi L}}\exp[{\frac {ik|{\vec {r}}-{\vec {r}}^{,}|^{2}}{2L}}]} . Under the right conditions, chaos spontaneously evolves into a lockstep pattern. In the Kuramoto model, four conditions suffice to produce synchronization in a chaotic system. Examples include the coupled oscillation of Christiaan Huygens' pendulums, fireflies, neurons, the London Millennium Bridge resonance, and large arrays of Josephson junctions. Moreover, from the theoretical physics standpoint, dynamical chaos itself, in its most general manifestation, is a spontaneous order. The essence here is that most orders in nature arise from the spontaneous breakdown of various symmetries. This large family of phenomena includes elasticity, superconductivity, ferromagnetism, and many others. According to the supersymmetric theory of stochastic dynamics, chaos, or more precisely, its stochastic generalization, is also part of this family. The corresponding symmetry being broken is the topological supersymmetry which is hidden in all stochastic (partial) differential equations, and the corresponding order parameter is a field-theoretic embodiment of the butterfly effect. There are also definitions of chaos that don't require the sensitivity on initial conditions property, such as combinatorial chaos (I.e. applying recursively a discrete combinatorial action). This is also comparable and similar to chaos generated by cellular automata. This is important because this type of chaos it's also equivalent to a turing machine, you can execute computation with such dynamical systems, and as such the halting problem is not decidable, therefore some computational algorithms may never end. This is ultimately a very different way for a system to be unpredictable. History James Clerk Maxwell was the first scientist to emphasize the importance of initial conditions, and he is seen as being one of the earliest to discuss chaos theory, with work in the 1860s and 1870s. In the 1880s, while studying the three-body problem, Henri Poincaré found that there can be orbits that are nonperiodic, and yet not forever increasing nor approaching a fixed point. In 1898, Jacques Hadamard published an influential study of the motion of a free particle gliding frictionlessly on a surface of constant negative curvature, called "Hadamard's billiards". Hadamard was able to show that all trajectories are unstable, in that all particle trajectories diverge exponentially from one another, with a positive Lyapunov exponent. Later studies, also on the topic of nonlinear differential equations, were carried out by George David Birkhoff, Andrey Nikolaevich Kolmogorov, Mary Lucy Cartwright and John Edensor Littlewood, and Stephen Smale. Experimentalists and mathematicians had encountered turbulence in fluid motion, chaotic behaviour in society and economy, nonperiodic oscillation in radio circuits and fractal patterns in nature without the benefit of a theory to explain what they were seeing. Despite initial insights in the first half of the twentieth century, chaos theory became formalized as such only after mid-century, when it first became evident to some scientists that linear theory which is smooth and continuous, and which was the prevailing system theory at that time, simply could not explain the observed behavior of certain experiments like that of the logistic map which has jump and erratic behaviours. Both of these observations underline the connection of chaos to either stochastic or non-linear dynamical systems, but definitely non-differentiable and non-continuous time evolution. What had been attributed to measure imprecision and simple "noise" was considered by chaos theorists as a full component of the studied systems. In 1959 Boris Valerianovich Chirikov proposed a criterion for the emergence of classical chaos in Hamiltonian systems (Chirikov criterion). He applied this criterion to explain some experimental results on plasma confinement in open mirror traps. This is regarded as the very first physical theory of chaos, which succeeded in explaining a concrete experiment. And Boris Chirikov himself is considered as a pioneer in classical and quantum chaos. The main catalyst for the development of chaos theory was the electronic computer. Much of the mathematics of chaos theory involves the repeated iteration of simple mathematical formulas, which would be impractical to do by hand. Electronic computers made these repeated calculations practical, while figures and images made it possible to visualize these systems. As a graduate student in Chihiro Hayashi's laboratory at Kyoto University, Yoshisuke Ueda was experimenting with analog computers and noticed, on November 27, 1961, what he called "randomly transitional phenomena". Yet his advisor did not agree with his conclusions at the time, and did not allow him to report his findings until 1970. Edward Lorenz was an early pioneer of the theory. His interest in chaos came about accidentally through his work on weather prediction in 1961. Lorenz and his collaborator Ellen Fetter and Margaret Hamilton were using a simple digital computer, a Royal McBee LGP-30, to run weather simulations. They wanted to see a sequence of data again, and to save time they started the simulation in the middle of its course. They did this by entering a printout of the data that corresponded to conditions in the middle of the original simulation. To their surprise, the weather the machine began to predict was completely different from the previous calculation. They tracked this down to the computer printout. The computer worked with 6-digit precision, but the printout rounded variables off to a 3-digit number, so a value like 0.506127 printed as 0.506. This difference is tiny, and the consensus at the time would have been that it should have no practical effect. However, Lorenz discovered that small changes in initial conditions produced large changes in long-term outcome. Lorenz's discovery, which gave its name to Lorenz attractors, showed that even detailed atmospheric modeling cannot, in general, make precise long-term weather predictions. In 1963, Benoit Mandelbrot, studying information theory, discovered that noise in many phenomena (including stock prices and telephone circuits) was patterned like a Cantor set, a set of points with infinite roughness and detail. Mandelbrot described both the "Noah effect" (in which sudden discontinuous changes can occur) and the "Joseph effect" (in which persistence of a value can occur for a while, yet suddenly change afterwards). In 1967, he published "How long is the coast of Britain? Statistical self-similarity and fractional dimension", showing that a coastline's length varies with the scale of the measuring instrument, resembles itself at all scales, and is infinite in length for an infinitesimally small measuring device. Arguing that a ball of twine appears as a point when viewed from far away (0-dimensional), a ball when viewed from fairly near (3-dimensional), or a curved strand (1-dimensional), he argued that the dimensions of an object are relative to the observer and may be fractional. An object whose irregularity is constant over different scales ("self-similarity") is a fractal (examples include the Menger sponge, the Sierpiński gasket, and the Koch curve or snowflake, which is infinitely long yet encloses a finite space and has a fractal dimension of circa 1.2619). In 1982, Mandelbrot published The Fractal Geometry of Nature, which became a classic of chaos theory. In December 1977, the New York Academy of Sciences organized the first symposium on chaos, attended by David Ruelle, Robert May, James A. Yorke (coiner of the term "chaos" as used in mathematics), Robert Shaw, and the meteorologist Edward Lorenz. The following year Pierre Coullet and Charles Tresser published "Itérations d'endomorphismes et groupe de renormalisation", and Mitchell Feigenbaum's article "Quantitative Universality for a Class of Nonlinear Transformations" finally appeared in a journal, after 3 years of referee rejections. Thus Feigenbaum (1975) and Coullet & Tresser (1978) discovered the universality in chaos, permitting the application of chaos theory to many different phenomena. In 1979, Albert J. Libchaber, during a symposium organized in Aspen by Pierre Hohenberg, presented his experimental observation of the bifurcation cascade that leads to chaos and turbulence in Rayleigh–Bénard convection systems. He was awarded the Wolf Prize in Physics in 1986 along with Mitchell J. Feigenbaum for their inspiring achievements. In 1986, the New York Academy of Sciences co-organized with the National Institute of Mental Health and the Office of Naval Research the first important conference on chaos in biology and medicine. There, Bernardo Huberman presented a mathematical model of the eye tracking dysfunction among people with schizophrenia. This led to a renewal of physiology in the 1980s through the application of chaos theory, for example, in the study of pathological cardiac cycles. In 1987, Per Bak, Chao Tang and Kurt Wiesenfeld published a paper in Physical Review Letters describing for the first time self-organized criticality (SOC), considered one of the mechanisms by which complexity arises in nature. Alongside largely lab-based approaches such as the Bak–Tang–Wiesenfeld sandpile, many other investigations have focused on large-scale natural or social systems that are known (or suspected) to display scale-invariant behavior. Although these approaches were not always welcomed (at least initially) by specialists in the subjects examined, SOC has nevertheless become established as a strong candidate for explaining a number of natural phenomena, including earthquakes, (which, long before SOC was discovered, were known as a source of scale-invariant behavior such as the Gutenberg–Richter law describing the statistical distribution of earthquake sizes, and the Omori law describing the frequency of aftershocks), solar flares, fluctuations in economic systems such as financial markets (references to SOC are common in econophysics), landscape formation, forest fires, landslides, epidemics, and biological evolution (where SOC has been invoked, for example, as the dynamical mechanism behind the theory of "punctuated equilibria" put forward by Niles Eldredge and Stephen Jay Gould). Given the implications of a scale-free distribution of event sizes, some researchers have suggested that another phenomenon that should be considered an example of SOC is the occurrence of wars. These investigations of SOC have included both attempts at modelling (either developing new models or adapting existing ones to the specifics of a given natural system), and extensive data analysis to determine the existence and/or characteristics of natural scaling laws. Also in 1987 James Gleick published Chaos: Making a New Science, which became a best-seller and introduced the general principles of chaos theory as well as its history to the broad public. Initially the domain of a few, isolated individuals, chaos theory progressively emerged as a transdisciplinary and institutional discipline, mainly under the name of nonlinear systems analysis. Alluding to Thomas Kuhn's concept of a paradigm shift exposed in The Structure of Scientific Revolutions (1962), many "chaologists" (as some described themselves) claimed that this new theory was an example of such a shift, a thesis upheld by Gleick. The availability of cheaper, more powerful computers broadens the applicability of chaos theory. Currently, chaos theory remains an active area of research, involving many different disciplines such as mathematics, topology, physics, social systems, population modeling, biology, meteorology, astrophysics, information theory, computational neuroscience, pandemic crisis management, etc. A popular but inaccurate analogy for chaos The sensitive dependence on initial conditions (i.e., butterfly effect) has been illustrated using the following folklore: For want of a nail, the shoe was lost. For want of a shoe, the horse was lost. For want of a horse, the rider was lost. For want of a rider, the battle was lost. For want of a battle, the kingdom was lost. And all for the want of a horseshoe nail. Based on the above, many people mistakenly believe that the impact of a tiny initial perturbation monotonically increases with time and that any tiny perturbation can eventually produce a large impact on numerical integrations. However, in 2008, Lorenz stated that he did not feel that this verse described true chaos but that it better illustrated the simpler phenomenon of instability and that the verse implicitly suggests that subsequent small events will not reverse the outcome. Based on the analysis, the verse only indicates divergence, not boundedness. Boundedness is important for the finite size of a butterfly pattern. The characteristic of the aforementioned verse was described as "finite-time sensitive dependence". Applications Although chaos theory was born from observing weather patterns, it has become applicable to a variety of other situations. Some areas benefiting from chaos theory today are geology, mathematics, biology, computer science, economics, engineering, finance, meteorology, philosophy, anthropology, physics, politics, population dynamics, and robotics. A few categories are listed below with examples, but this is by no means a comprehensive list as new applications are appearing. Chaos theory has been used for many years in cryptography. In the past few decades, chaos and nonlinear dynamics have been used in the design of hundreds of cryptographic primitives. These algorithms include image encryption algorithms, hash functions, secure pseudo-random number generators, stream ciphers, watermarking, and steganography. The majority of these algorithms are based on uni-modal chaotic maps and a big portion of these algorithms use the control parameters and the initial condition of the chaotic maps as their keys. From a wider perspective, without loss of generality, the similarities between the chaotic maps and the cryptographic systems is the main motivation for the design of chaos based cryptographic algorithms. One type of encryption, secret key or symmetric key, relies on diffusion and confusion, which is modeled well by chaos theory. Another type of computing, DNA computing, when paired with chaos theory, offers a way to encrypt images and other information. Many of the DNA-Chaos cryptographic algorithms are proven to be either not secure, or the technique applied is suggested to be not efficient. Robotics is another area that has recently benefited from chaos theory. Instead of robots acting in a trial-and-error type of refinement to interact with their environment, chaos theory has been used to build a predictive model. Chaotic dynamics have been exhibited by passive walking biped robots. For over a hundred years, biologists have been keeping track of populations of different species with population models. Most models are continuous, but recently scientists have been able to implement chaotic models in certain populations. For example, a study on models of Canadian lynx showed there was chaotic behavior in the population growth. Chaos can also be found in ecological systems, such as hydrology. While a chaotic model for hydrology has its shortcomings, there is still much to learn from looking at the data through the lens of chaos theory. Another biological application is found in cardiotocography. Fetal surveillance is a delicate balance of obtaining accurate information while being as noninvasive as possible. Better models of warning signs of fetal hypoxia can be obtained through chaotic modeling. As Perry points out, modeling of chaotic time series in ecology is helped by constraint.: 176, 177 There is always potential difficulty in distinguishing real chaos from chaos that is only in the model.: 176, 177 Hence both constraint in the model and or duplicate time series data for comparison will be helpful in constraining the model to something close to the reality, for example Perry & Wall 1984.: 176, 177 Gene-for-gene co-evolution sometimes shows chaotic dynamics in allele frequencies. Adding variables exaggerates this: Chaos is more common in models incorporating additional variables to reflect additional facets of real populations. Robert M. May himself did some of these foundational crop co-evolution studies, and this in turn helped shape the entire field. Even for a steady environment, merely combining one crop and one pathogen may result in quasi-periodic- or chaotic- oscillations in pathogen population.: 169 It is possible that economic models can also be improved through an application of chaos theory, but predicting the health of an economic system and what factors influence it most is an extremely complex task. Economic and financial systems are fundamentally different from those in the classical natural sciences since the former are inherently stochastic in nature, as they result from the interactions of people, and thus pure deterministic models are unlikely to provide accurate representations of the data. The empirical literature that tests for chaos in economics and finance presents very mixed results, in part due to confusion between specific tests for chaos and more general tests for non-linear relationships. Chaos could be found in economics by the means of recurrence quantification analysis. In fact, Orlando et al. by the means of the so-called recurrence quantification correlation index were able to detect hidden changes in time series. Then, the same technique was employed to detect transitions from laminar (regular) to turbulent (chaotic) phases as well as differences between macroeconomic variables and highlight hidden features of economic dynamics. Finally, chaos theory could help in modeling how an economy operates as well as in embedding shocks due to external events such as COVID-19. Due to the sensitive dependence of solutions on initial conditions (SDIC), also known as the butterfly effect, chaotic systems like the Lorenz 1963 model imply a finite predictability horizon. This means that while accurate predictions are possible over a finite time period, they are not feasible over an infinite time span. Considering the nature of Lorenz's chaotic solutions, the committee led by Charney et al. in 1966 extrapolated a doubling time of five days from a general circulation model, suggesting a predictability limit of two weeks. This connection between the five-day doubling time and the two-week predictability limit was also recorded in a 1969 report by the Global Atmospheric Research Program (GARP). To acknowledge the combined direct and indirect influences from the Mintz and Arakawa model and Lorenz's models, as well as the leadership of Charney et al., Shen et al. refer to the two-week predictability limit as the "Predictability Limit Hypothesis," drawing an analogy to Moore's Law. In AI-driven large language models, responses can exhibit sensitivities to factors like alterations in formatting and variations in prompts. These sensitivities are akin to butterfly effects. Although classifying AI-powered large language models as classical deterministic chaotic systems poses challenges, chaos-inspired approaches and techniques (such as ensemble modeling) may be employed to extract reliable information from these expansive language models (see also "Butterfly Effect in Popular Culture"). In chemistry, predicting gas solubility is essential to manufacturing polymers, but models using particle swarm optimization (PSO) tend to converge to the wrong points. An improved version of PSO has been created by introducing chaos, which keeps the simulations from getting stuck. In celestial mechanics, especially when observing asteroids, applying chaos theory leads to better predictions about when these objects will approach Earth and other planets. Four of the five moons of Pluto rotate chaotically. In quantum physics and electrical engineering, the study of large arrays of Josephson junctions benefitted greatly from chaos theory. Closer to home, coal mines have always been dangerous places where frequent natural gas leaks cause many deaths. Until recently, there was no reliable way to predict when they would occur. But these gas leaks have chaotic tendencies that, when properly modeled, can be predicted fairly accurately. Chaos theory can be applied outside of the natural sciences, but historically nearly all such studies have suffered from lack of reproducibility; poor external validity; and/or inattention to cross-validation, resulting in poor predictive accuracy (if out-of-sample prediction has even been attempted). Glass and Mandell and Selz have found that no EEG study has as yet indicated the presence of strange attractors or other signs of chaotic behavior. Redington and Reidbord (1992) attempted to demonstrate that the human heart could display chaotic traits. They monitored the changes in between-heartbeat intervals for a single psychotherapy patient as she moved through periods of varying emotional intensity during a therapy session. Results were admittedly inconclusive. Not only were there ambiguities in the various plots the authors produced to purportedly show evidence of chaotic dynamics (spectral analysis, phase trajectory, and autocorrelation plots), but also when they attempted to compute a Lyapunov exponent as more definitive confirmation of chaotic behavior, the authors found they could not reliably do so. In their 1995 paper, Metcalf and Allen maintained that they uncovered in animal behavior a pattern of period doubling leading to chaos. The authors examined a well-known response called schedule-induced polydipsia, by which an animal deprived of food for certain lengths of time will drink unusual amounts of water when the food is at last presented. The control parameter (r) operating here was the length of the interval between feedings, once resumed. The authors were careful to test a large number of animals and to include many replications, and they designed their experiment so as to rule out the likelihood that changes in response patterns were caused by different starting places for r. Time series and first delay plots provide the best support for the claims made, showing a fairly clear march from periodicity to irregularity as the feeding times were increased. The various phase trajectory plots and spectral analyses, on the other hand, do not match up well enough with the other graphs or with the overall theory to lead inexorably to a chaotic diagnosis. For example, the phase trajectories do not show a definite progression towards greater and greater complexity (and away from periodicity); the process seems quite muddied. Also, where Metcalf and Allen saw periods of two and six in their spectral plots, there is room for alternative interpretations. All of this ambiguity necessitate some serpentine, post-hoc explanation to show that results fit a chaotic model. By adapting a model of career counseling to include a chaotic interpretation of the relationship between employees and the job market, Amundson and Bright found that better suggestions can be made to people struggling with career decisions. Modern organizations are increasingly seen as open complex adaptive systems with fundamental natural nonlinear structures, subject to internal and external forces that may contribute chaos. For instance, team building and group development is increasingly being researched as an inherently unpredictable system, as the uncertainty of different individuals meeting for the first time makes the trajectory of the team unknowable. Traffic forecasting may benefit from applications of chaos theory. Better predictions of when a congestion will occur would allow measures to be taken to disperse it before it would have occurred. Combining chaos theory principles with a few other methods has led to a more accurate short-term prediction model (see the plot of the BML traffic model at right). Chaos theory has been applied to environmental water cycle data (also hydrological data), such as rainfall and streamflow. These studies have yielded controversial results, because the methods for detecting a chaotic signature are often relatively subjective. Early studies tended to "succeed" in finding chaos, whereas subsequent studies and meta-analyses called those studies into question and provided explanations for why these datasets are not likely to have low-dimension chaotic dynamics. See also Examples of chaotic systems Other related topics People References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Glaistig] | [TOKENS: 828] |
Contents Glaistig The glaistig /ˈɡlæʃtɪɡ/ is a ghost from Scottish mythology, a type of fuath. It is also known as maighdean uaine — the Green Maiden — and may appear as a woman of beauty or monstrous mien, as a half-woman and half-goat similar to a faun or satyr, or in the shape of a goat. The lower goat half of her hybrid form is usually disguised by a long, flowing green robe or dress, and the woman often appears grey with long yellow hair. This appearance may have been influenced by, or influenced, the closely related Norse folklore of "hidden-folk", Old Norse: hulder or huldra, across Scandinavia — along with the Faeroe Isles and Icelandic: Huldufólk — being beautiful women usually hiding legs and tail of an animal like a fox or a goat beneath clothing or long hair, with her named Skogsrå or Skogsfrun, the "Mistress of the Forest" in Swedish folklore. Variants The glaistig is an ambivalent ghost that appears in legend as both a malicious and benign creature. Some stories have her luring men to her lair via either song or dance, where she would then drink their blood. Other tales have her casting stones in the path of travellers or throwing them off course. In some benign incarnations, the glaistig is a type of tutelary spirit and protector of cattle and herders. One of the legends in Scotland, in the town of Ach-na-Creige, there was such a spirit protecting the cattle herds. The townsfolk, in gratitude, poured milk from the cows into a hollowed-out stone for her to drink. According to the same legend, her protection was revoked after one local youth poured boiling milk into the stone, burning her. She has also been described in some folklore as watching over children while their mothers milked the cows and fathers watched over the herds. In some Scottish tales, the cows are replaced with deer, of which the glaistig is fiercely protective. Also known as the Scottish goddess of the hunt, the glaistig was both help and hindrance to hunters, going so far as to hide her herds if the hunters made the mistake of killing a doe instead of a stag. Occasionally, hunters would be granted permission to shoot if they provided an offering, such as the hind of the deer to the herder. Another name of this instance is the Maiden of Callart. In the neighbouring Manx folklore, there is the similarly named shape-shifting Glashtyn, a water spirit.[citation needed] Another rendition of the glaistig legend is that she was once a mortal noblewoman, to whom a "fairy" nature had been given or who was cursed with the goat's legs and immortality, and since has been known as "The Green Lady". She might either be benign, watching over houses and looking after the weak mind, or appear as a vengeful ghost. In some tales she was murdered in a green dress, and then stuffed unceremoniously up the chimney by a servant. It is said that her footsteps can still be heard as she walks the castle in sadness. In most tales, she would continue to look after the house, upholding household duties, such as washing dishes and sweeping the floor. She might be heard moving around furniture at night. If she becomes offended by the servants or the tenants she is known to play pranks on them. Such Green Lady myths have been associated with a number of locations in Scotland, including Ardnacallich, Dunollie Castle, Loch Fyne, Muchalls Castle, Tulloch Castle, and in Wales at Caerphilly. A similar tale ("Ocean Born Mary") has been told in Henniker, New Hampshire. In literature References This article incorporates text from Dwelly's [Scottish] Gaelic Dictionary (1911). |
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[SOURCE: https://en.wikipedia.org/wiki/Multimedia_computer] | [TOKENS: 669] |
Contents Multimedia computer A multimedia computer is a computer that is optimized for multimedia performance. Early home computers lacked the power and storage necessary for true multimedia. The games for these systems, along with the demo scene, were able to achieve high sophistication and technical polish using only simple, blocky graphics and digitally generated sound. The Amiga 1000 from Commodore International has been called the first multimedia computer. Its groundbreaking animation, graphics and sound technologies enabled multimedia content to flourish. Famous demos such as the Boing Ball and Juggler showed off the Amiga's abilities. Later the Atari ST series and Apple Macintosh II extended the concept; the Atari integrated a MIDI port and was the first computer under US$1000 to have 1 megabyte of RAM, which is a realistic minimum for multimedia content, and the Macintosh was the first computer able to display true photorealistic graphics as well as integrating a CD-ROM drive, whose high capacity was essential for delivering multimedia content in the pre-Internet era. While the Commodore machines had the hardware to present multimedia of the kinds listed above, they lacked a way to create it easily. One of the earliest authoring systems on the market for creating and deploying multimedia content can be found in the archives of the Smithsonian Institution and is called VirtualVideo. It consisted of a standard PC with an added digital imaging board, an added digital audio capture board (that was sold as a phone answering device), and the DOS authoring software, VirtualVideo Producer. The system stored content on a local hard drive, but could use networked computer storage as well. The name for the software was used because at the time, the mid-1980s, the term multimedia was used to describe slide shows with sound. This software was later sold as Tempra, and in 1993 was included with Tay Vaugh's first edition of Multimedia: Making It Work. Multimedia capabilities were not common on IBM PC compatibles until the advent of Windows 3.0 and the MPC standards in the early 1990s. The original PCs were devised as "serious" business machines and colorful graphics and powerful sound abilities weren't a priority. The few games available suffered from slow video hardware, PC speaker sound and limited color palette when compared to its contemporaries. But as PCs penetrated the home market in the late 1980s, a thriving industry arose to equip PCs to take advantage of the latest sound, graphics and animation technologies. Creative's SoundBlaster series of sound cards, as well as video cards from ATI, Nvidia and Matrox, soon became standard equipment for most PCs sold. As of 2021[update], most PCs have good multimedia features. They have dual or more core CPUs clocked at 2.0 GHz or faster, at least 4 GB of RAM and an integrated graphics processing unit. Popular graphics cards include Nvidia GeForce or AMD Radeon. The Intel Core and AMD Ryzen platforms, and Microsoft Windows 10 and Windows 11 are some of today's products that excel at multimedia computing. More recently, high-performance devices have become more compact, and multimedia computer capabilities are found in mobile devices such as the Apple iPhone and many Android phones, featuring DVD-like video quality, multi-megapixel cameras, music and video players, and internet call (VoIP) functionality. References |
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[SOURCE: https://en.wikipedia.org/wiki/Elon_Musk#cite_note-NYT_AI-212] | [TOKENS: 10515] |
Contents Elon Musk Elon Reeve Musk (/ˈiːlɒn/ EE-lon; born June 28, 1971) is a businessman and entrepreneur known for his leadership of Tesla, SpaceX, Twitter, and xAI. Musk has been the wealthiest person in the world since 2025; as of February 2026,[update] Forbes estimates his net worth to be around US$852 billion. Born into a wealthy family in Pretoria, South Africa, Musk emigrated in 1989 to Canada; he has Canadian citizenship since his mother was born there. He received bachelor's degrees in 1997 from the University of Pennsylvania before moving to California to pursue business ventures. In 1995, Musk co-founded the software company Zip2. Following its sale in 1999, he co-founded X.com, an online payment company that later merged to form PayPal, which was acquired by eBay in 2002. Musk also became an American citizen in 2002. In 2002, Musk founded the space technology company SpaceX, becoming its CEO and chief engineer; the company has since led innovations in reusable rockets and commercial spaceflight. Musk joined the automaker Tesla as an early investor in 2004 and became its CEO and product architect in 2008; it has since become a leader in electric vehicles. In 2015, he co-founded OpenAI to advance artificial intelligence (AI) research, but later left; growing discontent with the organization's direction and their leadership in the AI boom in the 2020s led him to establish xAI, which became a subsidiary of SpaceX in 2026. In 2022, he acquired the social network Twitter, implementing significant changes, and rebranding it as X in 2023. His other businesses include the neurotechnology company Neuralink, which he co-founded in 2016, and the tunneling company the Boring Company, which he founded in 2017. In November 2025, a Tesla pay package worth $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Musk was the largest donor in the 2024 U.S. presidential election, where he supported Donald Trump. After Trump was inaugurated as president in early 2025, Musk served as Senior Advisor to the President and as the de facto head of the Department of Government Efficiency (DOGE). After a public feud with Trump, Musk left the Trump administration and returned to managing his companies. Musk is a supporter of global far-right figures, causes, and political parties. His political activities, views, and statements have made him a polarizing figure. Musk has been criticized for COVID-19 misinformation, promoting conspiracy theories, and affirming antisemitic, racist, and transphobic comments. His acquisition of Twitter was controversial due to a subsequent increase in hate speech and the spread of misinformation on the service, following his pledge to decrease censorship. His role in the second Trump administration attracted public backlash, particularly in response to DOGE. The emails he sent to Jeffrey Epstein are included in the Epstein files, which were published between 2025–26 and became a topic of worldwide debate. Early life Elon Reeve Musk was born on June 28, 1971, in Pretoria, South Africa's administrative capital. He is of British and Pennsylvania Dutch ancestry. His mother, Maye (née Haldeman), is a model and dietitian born in Saskatchewan, Canada, and raised in South Africa. Musk therefore holds both South African and Canadian citizenship from birth. His father, Errol Musk, is a South African electromechanical engineer, pilot, sailor, consultant, emerald dealer, and property developer, who partly owned a rental lodge at Timbavati Private Nature Reserve. His maternal grandfather, Joshua N. Haldeman, who died in a plane crash when Elon was a toddler, was an American-born Canadian chiropractor, aviator and political activist in the technocracy movement who moved to South Africa in 1950. Elon has a younger brother, Kimbal, a younger sister, Tosca, and four paternal half-siblings. Musk was baptized as a child in the Anglican Church of Southern Africa. Despite both Elon and Errol previously stating that Errol was a part owner of a Zambian emerald mine, in 2023, Errol recounted that the deal he made was to receive "a portion of the emeralds produced at three small mines". Errol was elected to the Pretoria City Council as a representative of the anti-apartheid Progressive Party and has said that his children shared their father's dislike of apartheid. After his parents divorced in 1979, Elon, aged around 9, chose to live with his father because Errol Musk had an Encyclopædia Britannica and a computer. Elon later regretted his decision and became estranged from his father. Elon has recounted trips to a wilderness school that he described as a "paramilitary Lord of the Flies" where "bullying was a virtue" and children were encouraged to fight over rations. In one incident, after an altercation with a fellow pupil, Elon was thrown down concrete steps and beaten severely, leading to him being hospitalized for his injuries. Elon described his father berating him after he was discharged from the hospital. Errol denied berating Elon and claimed, "The [other] boy had just lost his father to suicide, and Elon had called him stupid. Elon had a tendency to call people stupid. How could I possibly blame that child?" Elon was an enthusiastic reader of books, and had attributed his success in part to having read The Lord of the Rings, the Foundation series, and The Hitchhiker's Guide to the Galaxy. At age ten, he developed an interest in computing and video games, teaching himself how to program from the VIC-20 user manual. At age twelve, Elon sold his BASIC-based game Blastar to PC and Office Technology magazine for approximately $500 (equivalent to $1,600 in 2025). Musk attended Waterkloof House Preparatory School, Bryanston High School, and then Pretoria Boys High School, where he graduated. Musk was a decent but unexceptional student, earning a 61/100 in Afrikaans and a B on his senior math certification. Musk applied for a Canadian passport through his Canadian-born mother to avoid South Africa's mandatory military service, which would have forced him to participate in the apartheid regime, as well as to ease his path to immigration to the United States. While waiting for his application to be processed, he attended the University of Pretoria for five months. Musk arrived in Canada in June 1989, connected with a second cousin in Saskatchewan, and worked odd jobs, including at a farm and a lumber mill. In 1990, he entered Queen's University in Kingston, Ontario. Two years later, he transferred to the University of Pennsylvania, where he studied until 1995. Although Musk has said that he earned his degrees in 1995, the University of Pennsylvania did not award them until 1997 – a Bachelor of Arts in physics and a Bachelor of Science in economics from the university's Wharton School. He reportedly hosted large, ticketed house parties to help pay for tuition, and wrote a business plan for an electronic book-scanning service similar to Google Books. In 1994, Musk held two internships in Silicon Valley: one at energy storage startup Pinnacle Research Institute, which investigated electrolytic supercapacitors for energy storage, and another at Palo Alto–based startup Rocket Science Games. In 1995, he was accepted to a graduate program in materials science at Stanford University, but did not enroll. Musk decided to join the Internet boom of the 1990s, applying for a job at Netscape, to which he reportedly never received a response. The Washington Post reported that Musk lacked legal authorization to remain and work in the United States after failing to enroll at Stanford. In response, Musk said he was allowed to work at that time and that his student visa transitioned to an H1-B. According to numerous former business associates and shareholders, Musk said he was on a student visa at the time. Business career In 1995, Musk, his brother Kimbal, and Greg Kouri founded the web software company Zip2 with funding from a group of angel investors. They housed the venture at a small rented office in Palo Alto. Replying to Rolling Stone, Musk denounced the notion that they started their company with funds borrowed from Errol Musk, but in a tweet, he recognized that his father contributed 10% of a later funding round. The company developed and marketed an Internet city guide for the newspaper publishing industry, with maps, directions, and yellow pages. According to Musk, "The website was up during the day and I was coding it at night, seven days a week, all the time." To impress investors, Musk built a large plastic structure around a standard computer to create the impression that Zip2 was powered by a small supercomputer. The Musk brothers obtained contracts with The New York Times and the Chicago Tribune, and persuaded the board of directors to abandon plans for a merger with CitySearch. Musk's attempts to become CEO were thwarted by the board. Compaq acquired Zip2 for $307 million in cash in February 1999 (equivalent to $590,000,000 in 2025), and Musk received $22 million (equivalent to $43,000,000 in 2025) for his 7-percent share. In 1999, Musk co-founded X.com, an online financial services and e-mail payment company. The startup was one of the first federally insured online banks, and, in its initial months of operation, over 200,000 customers joined the service. The company's investors regarded Musk as inexperienced and replaced him with Intuit CEO Bill Harris by the end of the year. The following year, X.com merged with online bank Confinity to avoid competition. Founded by Max Levchin and Peter Thiel, Confinity had its own money-transfer service, PayPal, which was more popular than X.com's service. Within the merged company, Musk returned as CEO. Musk's preference for Microsoft software over Unix created a rift in the company and caused Thiel to resign. Due to resulting technological issues and lack of a cohesive business model, the board ousted Musk and replaced him with Thiel in 2000.[b] Under Thiel, the company focused on the PayPal service and was renamed PayPal in 2001. In 2002, PayPal was acquired by eBay for $1.5 billion (equivalent to $2,700,000,000 in 2025) in stock, of which Musk—the largest shareholder with 11.72% of shares—received $175.8 million (equivalent to $320,000,000 in 2025). In 2017, Musk purchased the domain X.com from PayPal for an undisclosed amount, stating that it had sentimental value. In 2001, Musk became involved with the nonprofit Mars Society and discussed funding plans to place a growth-chamber for plants on Mars. Seeking a way to launch the greenhouse payloads into space, Musk made two unsuccessful trips to Moscow to purchase intercontinental ballistic missiles (ICBMs) from Russian companies NPO Lavochkin and Kosmotras. Musk instead decided to start a company to build affordable rockets. With $100 million of his early fortune, (equivalent to $180,000,000 in 2025) Musk founded SpaceX in May 2002 and became the company's CEO and Chief Engineer. SpaceX attempted its first launch of the Falcon 1 rocket in 2006. Although the rocket failed to reach Earth orbit, it was awarded a Commercial Orbital Transportation Services program contract from NASA, then led by Mike Griffin. After two more failed attempts that nearly caused Musk to go bankrupt, SpaceX succeeded in launching the Falcon 1 into orbit in 2008. Later that year, SpaceX received a $1.6 billion NASA contract (equivalent to $2,400,000,000 in 2025) for Falcon 9-launched Dragon spacecraft flights to the International Space Station (ISS), replacing the Space Shuttle after its 2011 retirement. In 2012, the Dragon vehicle docked with the ISS, a first for a commercial spacecraft. Working towards its goal of reusable rockets, in 2015 SpaceX successfully landed the first stage of a Falcon 9 on a land platform. Later landings were achieved on autonomous spaceport drone ships, an ocean-based recovery platform. In 2018, SpaceX launched the Falcon Heavy; the inaugural mission carried Musk's personal Tesla Roadster as a dummy payload. Since 2019, SpaceX has been developing Starship, a reusable, super heavy-lift launch vehicle intended to replace the Falcon 9 and Falcon Heavy. In 2020, SpaceX launched its first crewed flight, the Demo-2, becoming the first private company to place astronauts into orbit and dock a crewed spacecraft with the ISS. In 2024, NASA awarded SpaceX an $843 million (equivalent to $865,000,000 in 2025) contract to build a spacecraft that NASA will use to deorbit the ISS at the end of its lifespan. In 2015, SpaceX began development of the Starlink constellation of low Earth orbit satellites to provide satellite Internet access. After the launch of prototype satellites in 2018, the first large constellation was deployed in May 2019. As of May 2025[update], over 7,600 Starlink satellites are operational, comprising 65% of all operational Earth satellites. The total cost of the decade-long project to design, build, and deploy the constellation was estimated by SpaceX in 2020 to be $10 billion (equivalent to $12,000,000,000 in 2025).[c] During the Russian invasion of Ukraine, Musk provided free Starlink service to Ukraine, permitting Internet access and communication at a yearly cost to SpaceX of $400 million (equivalent to $440,000,000 in 2025). However, Musk refused to block Russian state media on Starlink. In 2023, Musk denied Ukraine's request to activate Starlink over Crimea to aid an attack against the Russian navy, citing fears of a nuclear response. Tesla, Inc., originally Tesla Motors, was incorporated in July 2003 by Martin Eberhard and Marc Tarpenning. Both men played active roles in the company's early development prior to Musk's involvement. Musk led the Series A round of investment in February 2004; he invested $6.35 million (equivalent to $11,000,000 in 2025), became the majority shareholder, and joined Tesla's board of directors as chairman. Musk took an active role within the company and oversaw Roadster product design, but was not deeply involved in day-to-day business operations. Following a series of escalating conflicts in 2007 and the 2008 financial crisis, Eberhard was ousted from the firm.[page needed] Musk assumed leadership of the company as CEO and product architect in 2008. A 2009 lawsuit settlement with Eberhard designated Musk as a Tesla co-founder, along with Tarpenning and two others. Tesla began delivery of the Roadster, an electric sports car, in 2008. With sales of about 2,500 vehicles, it was the first mass production all-electric car to use lithium-ion battery cells. Under Musk, Tesla has since launched several well-selling electric vehicles, including the four-door sedan Model S (2012), the crossover Model X (2015), the mass-market sedan Model 3 (2017), the crossover Model Y (2020), and the pickup truck Cybertruck (2023). In May 2020, Musk resigned as chairman of the board as part of the settlement of a lawsuit from the SEC over him tweeting that funding had been "secured" for potentially taking Tesla private. The company has also constructed multiple lithium-ion battery and electric vehicle factories, called Gigafactories. Since its initial public offering in 2010, Tesla stock has risen significantly; it became the most valuable carmaker in summer 2020, and it entered the S&P 500 later that year. In October 2021, it reached a market capitalization of $1 trillion (equivalent to $1,200,000,000,000 in 2025), the sixth company in U.S. history to do so. Musk provided the initial concept and financial capital for SolarCity, which his cousins Lyndon and Peter Rive founded in 2006. By 2013, SolarCity was the second largest provider of solar power systems in the United States. In 2014, Musk promoted the idea of SolarCity building an advanced production facility in Buffalo, New York, triple the size of the largest solar plant in the United States. Construction of the factory started in 2014 and was completed in 2017. It operated as a joint venture with Panasonic until early 2020. Tesla acquired SolarCity for $2 billion in 2016 (equivalent to $2,700,000,000 in 2025) and merged it with its battery unit to create Tesla Energy. The deal's announcement resulted in a more than 10% drop in Tesla's stock price; at the time, SolarCity was facing liquidity issues. Multiple shareholder groups filed a lawsuit against Musk and Tesla's directors, stating that the purchase of SolarCity was done solely to benefit Musk and came at the expense of Tesla and its shareholders. Tesla directors settled the lawsuit in January 2020, leaving Musk the sole remaining defendant. Two years later, the court ruled in Musk's favor. In 2016, Musk co-founded Neuralink, a neurotechnology startup, with an investment of $100 million. Neuralink aims to integrate the human brain with artificial intelligence (AI) by creating devices that are embedded in the brain. Such technology could enhance memory or allow the devices to communicate with software. The company also hopes to develop devices to treat neurological conditions like spinal cord injuries. In 2022, Neuralink announced that clinical trials would begin by the end of the year. In September 2023, the Food and Drug Administration approved Neuralink to initiate six-year human trials. Neuralink has conducted animal testing on macaques at the University of California, Davis. In 2021, the company released a video in which a macaque played the video game Pong via a Neuralink implant. The company's animal trials—which have caused the deaths of some monkeys—have led to claims of animal cruelty. The Physicians Committee for Responsible Medicine has alleged that Neuralink violated the Animal Welfare Act. Employees have complained that pressure from Musk to accelerate development has led to botched experiments and unnecessary animal deaths. In 2022, a federal probe was launched into possible animal welfare violations by Neuralink.[needs update] In 2017, Musk founded the Boring Company to construct tunnels; he also revealed plans for specialized, underground, high-occupancy vehicles that could travel up to 150 miles per hour (240 km/h) and thus circumvent above-ground traffic in major cities. Early in 2017, the company began discussions with regulatory bodies and initiated construction of a 30-foot (9.1 m) wide, 50-foot (15 m) long, and 15-foot (4.6 m) deep "test trench" on the premises of SpaceX's offices, as that required no permits. The Los Angeles tunnel, less than two miles (3.2 km) in length, debuted to journalists in 2018. It used Tesla Model Xs and was reported to be a rough ride while traveling at suboptimal speeds. Two tunnel projects announced in 2018, in Chicago and West Los Angeles, have been canceled. A tunnel beneath the Las Vegas Convention Center was completed in early 2021. Local officials have approved further expansions of the tunnel system. April 14, 2022 In early 2017, Musk expressed interest in buying Twitter and had questioned the platform's commitment to freedom of speech. By 2022, Musk had reached 9.2% stake in the company, making him the largest shareholder.[d] Musk later agreed to a deal that would appoint him to Twitter's board of directors and prohibit him from acquiring more than 14.9% of the company. Days later, Musk made a $43 billion offer to buy Twitter. By the end of April Musk had successfully concluded his bid for approximately $44 billion. This included approximately $12.5 billion in loans and $21 billion in equity financing. Having backtracked on his initial decision, Musk bought the company on October 27, 2022. Immediately after the acquisition, Musk fired several top Twitter executives including CEO Parag Agrawal; Musk became the CEO instead. Under Elon Musk, Twitter instituted monthly subscriptions for a "blue check", and laid off a significant portion of the company's staff. Musk lessened content moderation and hate speech also increased on the platform after his takeover. In late 2022, Musk released internal documents relating to Twitter's moderation of Hunter Biden's laptop controversy in the lead-up to the 2020 presidential election. Musk also promised to step down as CEO after a Twitter poll, and five months later, Musk stepped down as CEO and transitioned his role to executive chairman and chief technology officer (CTO). Despite Musk stepping down as CEO, X continues to struggle with challenges such as viral misinformation, hate speech, and antisemitism controversies. Musk has been accused of trying to silence some of his critics such as Twitch streamer Asmongold, who criticized him during one of his streams. Musk has been accused of removing their accounts' blue checkmarks, which hinders visibility and is considered a form of shadow banning, or suspending their accounts without justification. Other activities In August 2013, Musk announced plans for a version of a vactrain, and assigned engineers from SpaceX and Tesla to design a transport system between Greater Los Angeles and the San Francisco Bay Area, at an estimated cost of $6 billion. Later that year, Musk unveiled the concept, dubbed the Hyperloop, intended to make travel cheaper than any other mode of transport for such long distances. In December 2015, Musk co-founded OpenAI, a not-for-profit artificial intelligence (AI) research company aiming to develop artificial general intelligence, intended to be safe and beneficial to humanity. Musk pledged $1 billion of funding to the company, and initially gave $50 million. In 2018, Musk left the OpenAI board. Since 2018, OpenAI has made significant advances in machine learning. In July 2023, Musk launched the artificial intelligence company xAI, which aims to develop a generative AI program that competes with existing offerings like OpenAI's ChatGPT. Musk obtained funding from investors in SpaceX and Tesla, and xAI hired engineers from Google and OpenAI. December 16, 2022 Musk uses a private jet owned by Falcon Landing LLC, a SpaceX-linked company, and acquired a second jet in August 2020. His heavy use of the jets and the consequent fossil fuel usage have received criticism. Musk's flight usage is tracked on social media through ElonJet. In December 2022, Musk banned the ElonJet account on Twitter, and made temporary bans on the accounts of journalists that posted stories regarding the incident, including Donie O'Sullivan, Keith Olbermann, and journalists from The New York Times, The Washington Post, CNN, and The Intercept. In October 2025, Musk's company xAI launched Grokipedia, an AI-generated online encyclopedia that he promoted as an alternative to Wikipedia. Articles on Grokipedia are generated and reviewed by xAI's Grok chatbot. Media coverage and academic analysis described Grokipedia as frequently reusing Wikipedia content but framing contested political and social topics in line with Musk's own views and right-wing narratives. A study by Cornell University researchers and NBC News stated that Grokipedia cites sources that are blacklisted or considered "generally unreliable" on Wikipedia, for example, the conspiracy site Infowars and the neo-Nazi forum Stormfront. Wired, The Guardian and Time criticized Grokipedia for factual errors and for presenting Musk himself in unusually positive terms while downplaying controversies. Politics Musk is an outlier among business leaders who typically avoid partisan political advocacy. Musk was a registered independent voter when he lived in California. Historically, he has donated to both Democrats and Republicans, many of whom serve in states in which he has a vested interest. Since 2022, his political contributions have mostly supported Republicans, with his first vote for a Republican going to Mayra Flores in the 2022 Texas's 34th congressional district special election. In 2024, he started supporting international far-right political parties, activists, and causes, and has shared misinformation and numerous conspiracy theories. Since 2024, his views have been generally described as right-wing. Musk supported Barack Obama in 2008 and 2012, Hillary Clinton in 2016, Joe Biden in 2020, and Donald Trump in 2024. In the 2020 Democratic Party presidential primaries, Musk endorsed candidate Andrew Yang and expressed support for Yang's proposed universal basic income, and endorsed Kanye West's 2020 presidential campaign. In 2021, Musk publicly expressed opposition to the Build Back Better Act, a $3.5 trillion legislative package endorsed by Joe Biden that ultimately failed to pass due to unanimous opposition from congressional Republicans and several Democrats. In 2022, gave over $50 million to Citizens for Sanity, a conservative political action committee. In 2023, he supported Republican Ron DeSantis for the 2024 U.S. presidential election, giving $10 million to his campaign, and hosted DeSantis's campaign announcement on a Twitter Spaces event. From June 2023 to January 2024, Musk hosted a bipartisan set of X Spaces with Republican and Democratic candidates, including Robert F. Kennedy Jr., Vivek Ramaswamy, and Dean Phillips. In October 2025, former vice-president Kamala Harris commented that it was a mistake from the Democratic side to not invite Musk to a White House electric vehicle event organized in August 2021 and featuring executives from General Motors, Ford and Stellantis, despite Tesla being "the major American manufacturer of extraordinary innovation in this space." Fortune remarked that this was a nod to United Auto Workers and organized labor. Harris said presidents should put aside political loyalties when it came to recognizing innovation, and guessed that the non-invitation impacted Musk's perspective. Fortune noted that, at the time, Musk said, "Yeah, seems odd that Tesla wasn't invited." A month later, he criticized Biden as "not the friendliest administration." Jacob Silverman, author of the book Gilded Rage: Elon Musk and the Radicalization of Silicon Valley, said that the tech industry represented by Musk, Thiel, Andreessen and other capitalists, actually flourished under Biden, but the tech leaders chose Trump for their common ground on cultural issues. By early 2024, Musk had become a vocal and financial supporter of Donald Trump. In July 2024, minutes after the attempted assassination of Donald Trump, Musk endorsed him for president saying; "I fully endorse President Trump and hope for his rapid recovery." During the presidential campaign, Musk joined Trump on stage at a campaign rally, and during the campaign promoted conspiracy theories and falsehoods about Democrats, election fraud and immigration, in support of Trump. Musk was the largest individual donor of the 2024 election. In 2025, Musk contributed $19 million to the Wisconsin Supreme Court race, hoping to influence the state's future redistricting efforts and its regulations governing car manufacturers and dealers. In 2023, Musk said he shunned the World Economic Forum because it was boring. The organization commented that they had not invited him since 2015. He has participated in Dialog, dubbed "Tech Bilderberg" and organized by Peter Thiel and Auren Hoffman, though. Musk's international political actions and comments have come under increasing scrutiny and criticism, especially from the governments and leaders of France, Germany, Norway, Spain and the United Kingdom, particularly due to his position in the U.S. government as well as ownership of X. An NBC News analysis found he had boosted far-right political movements to cut immigration and curtail regulation of business in at least 18 countries on six continents since 2023. During his speech after the second inauguration of Donald Trump, Musk twice made a gesture interpreted by many as a Nazi or a fascist Roman salute.[e] He thumped his right hand over his heart, fingers spread wide, and then extended his right arm out, emphatically, at an upward angle, palm down and fingers together. He then repeated the gesture to the crowd behind him. As he finished the gestures, he said to the crowd, "My heart goes out to you. It is thanks to you that the future of civilization is assured." It was widely condemned as an intentional Nazi salute in Germany, where making such gestures is illegal. The Anti-Defamation League said it was not a Nazi salute, but other Jewish organizations disagreed and condemned the salute. American public opinion was divided on partisan lines as to whether it was a fascist salute. Musk dismissed the accusations of Nazi sympathies, deriding them as "dirty tricks" and a "tired" attack. Neo-Nazi and white supremacist groups celebrated it as a Nazi salute. Multiple European political parties demanded that Musk be banned from entering their countries. The concept of DOGE emerged in a discussion between Musk and Donald Trump, and in August 2024, Trump committed to giving Musk an advisory role, with Musk accepting the offer. In November and December 2024, Musk suggested that the organization could help to cut the U.S. federal budget, consolidate the number of federal agencies, and eliminate the Consumer Financial Protection Bureau, and that its final stage would be "deleting itself". In January 2025, the organization was created by executive order, and Musk was designated a "special government employee". Musk led the organization and was a senior advisor to the president, although his official role is not clear. In sworn statement during a lawsuit, the director of the White House Office of Administration stated that Musk "is not an employee of the U.S. DOGE Service or U.S. DOGE Service Temporary Organization", "is not the U.S. DOGE Service administrator", and has "no actual or formal authority to make government decisions himself". Trump said two days later that he had put Musk in charge of DOGE. A federal judge has ruled that Musk acted as the de facto leader of DOGE. Musk's role in the second Trump administration, particularly in response to DOGE, has attracted public backlash. He was criticized for his treatment of federal government employees, including his influence over the mass layoffs of the federal workforce. He has prioritized secrecy within the organization and has accused others of violating privacy laws. A Senate report alleged that Musk could avoid up to $2 billion in legal liability as a result of DOGE's actions. In May 2025, Bill Gates accused Musk of "killing the world's poorest children" through his cuts to USAID, which modeling by Boston University estimated had resulted in 300,000 deaths by this time, most of them of children. By November 2025, the estimated death toll had increased to 400,000 children and 200,000 adults. Musk announced on May 28, 2025, that he would depart from the Trump administration as planned when the special government employee's 130 day deadline expired, with a White House official confirming that Musk's offboarding from the Trump administration was already underway. His departure was officially confirmed during a joint Oval Office press conference with Trump on May 30, 2025. @realDonaldTrump is in the Epstein files. That is the real reason they have not been made public. June 5, 2025 After leaving office, Musk criticized the Trump administration's Big Beautiful Bill, calling it a "disgusting abomination" due to its provisions increasing the deficit. A feud began between Musk and Trump, with its most notable event being Musk alleging Trump had ties to sex offender Jeffrey Epstein on X (formerly Twitter) on June 5, 2025. Trump responded on Truth Social stating that Musk went "CRAZY" after the "EV Mandate" was purportedly taken away and threatened to cut Musk's government contracts. Musk then called for a third Trump impeachment. The next day, Trump stated that he did not wish to reconcile with Musk, and added that Musk would face "very serious consequences" if he funds Democratic candidates. On June 11, Musk publicly apologized for the tweets against Trump, saying they "went too far". Views November 6, 2022 Rejecting the conservative label, Musk has described himself as a political moderate, even as his views have become more right-wing over time. His views have been characterized as libertarian and far-right, and after his involvement in European politics, they have received criticism from world leaders such as Emmanuel Macron and Olaf Scholz. Within the context of American politics, Musk supported Democratic candidates up until 2022, at which point he voted for a Republican for the first time. He has stated support for universal basic income, gun rights, freedom of speech, a tax on carbon emissions, and H-1B visas. Musk has expressed concern about issues such as artificial intelligence (AI) and climate change, and has been a critic of wealth tax, short-selling, and government subsidies. An immigrant himself, Musk has been accused of being anti-immigration, and regularly blames immigration policies for illegal immigration. He is also a pronatalist who believes population decline is the biggest threat to civilization, and identifies as a cultural Christian. Musk has long been an advocate for space colonization, especially the colonization of Mars. He has repeatedly pushed for humanity colonizing Mars, in order to become an interplanetary species and lower the risks of human extinction. Musk has promoted conspiracy theories and made controversial statements that have led to accusations of racism, sexism, antisemitism, transphobia, disseminating disinformation, and support of white pride. While describing himself as a "pro-Semite", his comments regarding George Soros and Jewish communities have been condemned by the Anti-Defamation League and the Biden White House. Musk was criticized during the COVID-19 pandemic for making unfounded epidemiological claims, defying COVID-19 lockdowns restrictions, and supporting the Canada convoy protest against vaccine mandates. He has amplified false claims of white genocide in South Africa. Musk has been critical of Israel's actions in the Gaza Strip during the Gaza war, praised China's economic and climate goals, suggested that Taiwan and China should resolve cross-strait relations, and was described as having a close relationship with the Chinese government. In Europe, Musk expressed support for Ukraine in 2022 during the Russian invasion, recommended referendums and peace deals on the annexed Russia-occupied territories, and supported the far-right Alternative for Germany political party in 2024. Regarding British politics, Musk blamed the 2024 UK riots on mass migration and open borders, criticized Prime Minister Keir Starmer for what he described as a "two-tier" policing system, and was subsequently attacked as being responsible for spreading misinformation and amplifying the far-right. He has also voiced his support for far-right activist Tommy Robinson and pledged electoral support for Reform UK. In February 2026, Musk described Spanish Prime Minister Pedro Sánchez as a "tyrant" following Sánchez's proposal to prohibit minors under the age of 16 from accessing social media platforms. Legal affairs In 2018, Musk was sued by the U.S. Securities and Exchange Commission (SEC) for a tweet stating that funding had been secured for potentially taking Tesla private.[f] The securities fraud lawsuit characterized the tweet as false, misleading, and damaging to investors, and sought to bar Musk from serving as CEO of publicly traded companies. Two days later, Musk settled with the SEC, without admitting or denying the SEC's allegations. As a result, Musk and Tesla were fined $20 million each, and Musk was forced to step down for three years as Tesla chairman but was able to remain as CEO. Shareholders filed a lawsuit over the tweet, and in February 2023, a jury found Musk and Tesla not liable. Musk has stated in interviews that he does not regret posting the tweet that triggered the SEC investigation. In 2019, Musk stated in a tweet that Tesla would build half a million cars that year. The SEC reacted by asking a court to hold him in contempt for violating the terms of the 2018 settlement agreement. A joint agreement between Musk and the SEC eventually clarified the previous agreement details, including a list of topics about which Musk needed preclearance. In 2020, a judge blocked a lawsuit that claimed a tweet by Musk regarding Tesla stock price ("too high imo") violated the agreement. Freedom of Information Act (FOIA)-released records showed that the SEC concluded Musk had subsequently violated the agreement twice by tweeting regarding "Tesla's solar roof production volumes and its stock price". In October 2023, the SEC sued Musk over his refusal to testify a third time in an investigation into whether he violated federal law by purchasing Twitter stock in 2022. In February 2024, Judge Laurel Beeler ruled that Musk must testify again. In January 2025, the SEC filed a lawsuit against Musk for securities violations related to his purchase of Twitter. In January 2024, Delaware judge Kathaleen McCormick ruled in a 2018 lawsuit that Musk's $55 billion pay package from Tesla be rescinded. McCormick called the compensation granted by the company's board "an unfathomable sum" that was unfair to shareholders. The Delaware Supreme Court overturned McCormick's decision in December 2025, restoring Musk's compensation package and awarding $1 in nominal damages. Personal life Musk became a U.S. citizen in 2002. From the early 2000s until late 2020, Musk resided in California, where both Tesla and SpaceX were founded. He then relocated to Cameron County, Texas, saying that California had become "complacent" about its economic success. While hosting Saturday Night Live in 2021, Musk stated that he has Asperger syndrome (an outdated term for autism spectrum disorder). When asked about his experience growing up with Asperger's syndrome in a TED2022 conference in Vancouver, Musk stated that "the social cues were not intuitive ... I would just tend to take things very literally ... but then that turned out to be wrong — [people were not] simply saying exactly what they mean, there's all sorts of other things that are meant, and [it] took me a while to figure that out." Musk suffers from back pain and has undergone several spine-related surgeries, including a disc replacement. In 2000, he contracted a severe case of malaria while on vacation in South Africa. Musk has stated he uses doctor-prescribed ketamine for occasional depression and that he doses "a small amount once every other week or something like that"; since January 2024, some media outlets have reported that he takes ketamine, marijuana, LSD, ecstasy, mushrooms, cocaine and other drugs. Musk at first refused to comment on his alleged drug use, before responding that he had not tested positive for drugs, and that if drugs somehow improved his productivity, "I would definitely take them!". The New York Times' investigations revealed Musk's overuse of ketamine and numerous other drugs, as well as strained family relationships and concerns from close associates who have become troubled by his public behavior as he became more involved in political activities and government work. According to The Washington Post, President Trump described Musk as "a big-time drug addict". Through his own label Emo G Records, Musk released a rap track, "RIP Harambe", on SoundCloud in March 2019. The following year, he released an EDM track, "Don't Doubt Ur Vibe", featuring his own lyrics and vocals. Musk plays video games, which he stated has a "'restoring effect' that helps his 'mental calibration'". Some games he plays include Quake, Diablo IV, Elden Ring, and Polytopia. Musk once claimed to be one of the world's top video game players but has since admitted to "account boosting", or cheating by hiring outside services to achieve top player rankings. Musk has justified the boosting by claiming that all top accounts do it so he has to as well to remain competitive. In 2024 and 2025, Musk criticized the video game Assassin's Creed Shadows and its creator Ubisoft for "woke" content. Musk posted to X that "DEI kills art" and specified the inclusion of the historical figure Yasuke in the Assassin's Creed game as offensive; he also called the game "terrible". Ubisoft responded by saying that Musk's comments were "just feeding hatred" and that they were focused on producing a game not pushing politics. Musk has fathered at least 14 children, one of whom died as an infant. The Wall Street Journal reported in 2025 that sources close to Musk suggest that the "true number of Musk's children is much higher than publicly known". He had six children with his first wife, Canadian author Justine Wilson, whom he met while attending Queen's University in Ontario, Canada; they married in 2000. In 2002, their first child Nevada Musk died of sudden infant death syndrome at the age of 10 weeks. After his death, the couple used in vitro fertilization (IVF) to continue their family; they had twins in 2004, followed by triplets in 2006. The couple divorced in 2008 and have shared custody of their children. The elder twin he had with Wilson came out as a trans woman and, in 2022, officially changed her name to Vivian Jenna Wilson, adopting her mother's surname because she no longer wished to be associated with Musk. Musk began dating English actress Talulah Riley in 2008. They married two years later at Dornoch Cathedral in Scotland. In 2012, the couple divorced, then remarried the following year. After briefly filing for divorce in 2014, Musk finalized a second divorce from Riley in 2016. Musk then dated the American actress Amber Heard for several months in 2017; he had reportedly been "pursuing" her since 2012. In 2018, Musk and Canadian musician Grimes confirmed they were dating. Grimes and Musk have three children, born in 2020, 2021, and 2022.[g] Musk and Grimes originally gave their eldest child the name "X Æ A-12", which would have violated California regulations as it contained characters that are not in the modern English alphabet; the names registered on the birth certificate are "X" as a first name, "Æ A-Xii" as a middle name, and "Musk" as a last name. They received criticism for choosing a name perceived to be impractical and difficult to pronounce; Musk has said the intended pronunciation is "X Ash A Twelve". Their second child was born via surrogacy. Despite the pregnancy, Musk confirmed reports that the couple were "semi-separated" in September 2021; in an interview with Time in December 2021, he said he was single. In October 2023, Grimes sued Musk over parental rights and custody of X Æ A-Xii. Elon Musk has taken X Æ A-Xii to multiple official events in Washington, D.C. during Trump's second term in office. Also in July 2022, The Wall Street Journal reported that Musk allegedly had an affair with Nicole Shanahan, the wife of Google co-founder Sergey Brin, in 2021, leading to their divorce the following year. Musk denied the report. Musk also had a relationship with Australian actress Natasha Bassett, who has been described as "an occasional girlfriend". In October 2024, The New York Times reported Musk bought a Texas compound for his children and their mothers, though Musk denied having done so. Musk also has four children with Shivon Zilis, director of operations and special projects at Neuralink: twins born via IVF in 2021, a child born in 2024 via surrogacy and a child born in 2025.[h] On February 14, 2025, Ashley St. Clair, an influencer and author, posted on X claiming to have given birth to Musk's son Romulus five months earlier, which media outlets reported as Musk's supposed thirteenth child.[i] On February 22, 2025, it was reported that St Clair had filed for sole custody of her five-month-old son and for Musk to be recognised as the child's father. On March 31, 2025, Musk wrote that, while he was unsure if he was the father of St. Clair's child, he had paid St. Clair $2.5 million and would continue paying her $500,000 per year.[j] Later reporting from the Wall Street Journal indicated that $1 million of these payments to St. Clair were structured as a loan. In 2014, Musk and Ghislaine Maxwell appeared together in a photograph taken at an Academy Awards after-party, which Musk later described as a "photobomb". The January 2026 Epstein files contain emails between Musk and Epstein from 2012 to 2013, after Epstein's first conviction. Emails released on January 30, 2026, indicated that Epstein invited Musk to visit his private island on multiple occasions. The correspondence showed that while Epstein repeatedly encouraged Musk to attend, Musk did not visit the island. In one instance, Musk discussed the possibility of attending a party with his then-wife Talulah Riley and asked which day would be the "wildest party"; according to the emails, the visit did not take place after Epstein later cancelled the plans.[k] On Christmas day in 2012, Musk emailed Epstein asking "Do you have any parties planned? I’ve been working to the edge of sanity this year and so, once my kids head home after Christmas, I really want to hit the party scene in St Barts or elsewhere and let loose. The invitation is much appreciated, but a peaceful island experience is the opposite of what I’m looking for". Epstein replied that the "ratio on my island" might make Musk's wife uncomfortable to which Musk responded, "Ratio is not a problem for Talulah". On September 11, 2013, Epstein sent an email asking Musk if he had any plans for coming to New York for the opening of the United Nations General Assembly where many "interesting people" would be coming to his house to which Musk responded that "Flying to NY to see UN diplomats do nothing would be an unwise use of time". Epstein responded by stating "Do you think i am retarded. Just kidding, there is no one over 25 and all very cute." Musk has denied any close relationship with Epstein and described him as a "creep" who attempted to ingratiate himself with influential people. When Musk was asked in 2019 if he introduced Epstein to Mark Zuckerberg, Musk responded: "I don’t recall introducing Epstein to anyone, as I don’t know the guy well enough to do so." The released emails nonetheless showed cordial exchanges on a range of topics, including Musk's inquiry about parties on the island. The correspondence also indicated that Musk suggested hosting Epstein at SpaceX, while Epstein separately discussed plans to tour SpaceX and bring "the girls", though there is no evidence that such a visit occurred. Musk has described the release of the files a "distraction", later accusing the second Trump administration of suppressing them to protect powerful individuals, including Trump himself.[l] Wealth Elon Musk is the wealthiest person in the world, with an estimated net worth of US$690 billion as of January 2026, according to the Bloomberg Billionaires Index, and $852 billion according to Forbes, primarily from his ownership stakes in SpaceX and Tesla. Having been first listed on the Forbes Billionaires List in 2012, around 75% of Musk's wealth was derived from Tesla stock in November 2020, although he describes himself as "cash poor". According to Forbes, he became the first person in the world to achieve a net worth of $300 billion in 2021; $400 billion in December 2024; $500 billion in October 2025; $600 billion in mid-December 2025; $700 billion later that month; and $800 billion in February 2026. In November 2025, a Tesla pay package worth potentially $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Public image Although his ventures have been highly influential within their separate industries starting in the 2000s, Musk only became a public figure in the early 2010s. He has been described as an eccentric who makes spontaneous and impactful decisions, while also often making controversial statements, contrary to other billionaires who prefer reclusiveness to protect their businesses. Musk's actions and his expressed views have made him a polarizing figure. Biographer Ashlee Vance described people's opinions of Musk as polarized due to his "part philosopher, part troll" persona on Twitter. He has drawn denouncement for using his platform to mock the self-selection of personal pronouns, while also receiving praise for bringing international attention to matters like British survivors of grooming gangs. Musk has been described as an American oligarch due to his extensive influence over public discourse, social media, industry, politics, and government policy. After Trump's re-election, Musk's influence and actions during the transition period and the second presidency of Donald Trump led some to call him "President Musk", the "actual president-elect", "shadow president" or "co-president". Awards for his contributions to the development of the Falcon rockets include the American Institute of Aeronautics and Astronautics George Low Transportation Award in 2008, the Fédération Aéronautique Internationale Gold Space Medal in 2010, and the Royal Aeronautical Society Gold Medal in 2012. In 2015, he received an honorary doctorate in engineering and technology from Yale University and an Institute of Electrical and Electronics Engineers Honorary Membership. Musk was elected a Fellow of the Royal Society (FRS) in 2018.[m] In 2022, Musk was elected to the National Academy of Engineering. Time has listed Musk as one of the most influential people in the world in 2010, 2013, 2018, and 2021. Musk was selected as Time's "Person of the Year" for 2021. Then Time editor-in-chief Edward Felsenthal wrote that, "Person of the Year is a marker of influence, and few individuals have had more influence than Musk on life on Earth, and potentially life off Earth too." Notes References Works cited Further reading External links |
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Contents Social network 1800s: Martineau · Tocqueville · Marx · Spencer · Le Bon · Ward · Pareto · Tönnies · Veblen · Simmel · Durkheim · Addams · Mead · Weber · Du Bois · Mannheim · Elias A social network is a social structure consisting of a set of social actors (such as individuals or organizations), networks of dyadic ties, and other social interactions between actors. The social network perspective provides a set of methods for analyzing the structure of whole social entities along with a variety of theories explaining the patterns observed in these structures. The study of these structures uses social network analysis to identify local and global patterns, locate influential entities, and examine dynamics of networks. For instance, social network analysis has been used in studying the spread of misinformation on social media platforms or analyzing the influence of key figures in social networks. Social networks and the analysis of them is an inherently interdisciplinary academic field which emerged from social psychology, sociology, statistics, and graph theory. Georg Simmel authored early structural theories in sociology emphasizing the dynamics of triads and "web of group affiliations". Jacob Moreno is credited with developing the first sociograms in the 1930s to study interpersonal relationships. These approaches were mathematically formalized in the 1950s and theories and methods of social networks became pervasive in the social and behavioral sciences by the 1980s. Social network analysis is now one of the major paradigms in contemporary sociology, and is also employed in a number of other social and formal sciences. Together with other complex networks, it forms part of the nascent field of network science. Overview The social network is a theoretical construct useful in the social sciences to study relationships between individuals, groups, organizations, or even entire societies (social units, see differentiation). The term is used to describe a social structure determined by such interactions. The ties through which any given social unit connects represent the convergence of the various social contacts of that unit. This theoretical approach is, necessarily, relational. An axiom of the social network approach to understanding social interaction is that social phenomena should be primarily conceived and investigated through the properties of relations between and within units, instead of the properties of these units themselves. Thus, one common criticism of social network theory is that individual agency is often ignored although this may not be the case in practice (see agent-based modeling). Precisely because many different types of relations, singular or in combination, form these network configurations, network analytics are useful to a broad range of research enterprises. In social science, these fields of study include, but are not limited to anthropology, biology, communication studies, economics, geography, information science, organizational studies, social psychology, sociology, and sociolinguistics. History In the late 1890s, both Émile Durkheim and Ferdinand Tönnies foreshadowed the idea of social networks in their theories and research of social groups. Tönnies argued that social groups can exist as personal and direct social ties that either link individuals who share values and belief (Gemeinschaft, German, commonly translated as "community") or impersonal, formal, and instrumental social links (Gesellschaft, German, commonly translated as "society"). Durkheim gave a non-individualistic explanation of social facts, arguing that social phenomena arise when interacting individuals constitute a reality that can no longer be accounted for in terms of the properties of individual actors. Georg Simmel, writing at the turn of the twentieth century, pointed to the nature of networks and the effect of network size on interaction and examined the likelihood of interaction in loosely knit networks rather than groups. Major developments in the field can be seen in the 1930s by several groups in psychology, anthropology, and mathematics working independently. In psychology, in the 1930s, Jacob L. Moreno began systematic recording and analysis of social interaction in small groups, especially classrooms and work groups (see sociometry). In anthropology, the foundation for social network theory is the theoretical and ethnographic work of Bronislaw Malinowski, Alfred Radcliffe-Brown, and Claude Lévi-Strauss. A group of social anthropologists associated with Max Gluckman and the Manchester School, including John A. Barnes, J. Clyde Mitchell and Elizabeth Bott Spillius, often are credited with performing some of the first fieldwork from which network analyses were performed, investigating community networks in southern Africa, India and the United Kingdom. Concomitantly, British anthropologist S. F. Nadel codified a theory of social structure that was influential in later network analysis. In sociology, the early (1930s) work of Talcott Parsons set the stage for taking a relational approach to understanding social structure. Later, drawing upon Parsons' theory, the work of sociologist Peter Blau provides a strong impetus for analyzing the relational ties of social units with his work on social exchange theory. By the 1970s, a growing number of scholars worked to combine the different tracks and traditions. One group consisted of sociologist Harrison White and his students at the Harvard University Department of Social Relations. Also independently active in the Harvard Social Relations department at the time were Charles Tilly, who focused on networks in political and community sociology and social movements, and Stanley Milgram, who developed the "six degrees of separation" thesis. Mark Granovetter and Barry Wellman are among the former students of White who elaborated and championed the analysis of social networks. Beginning in the late 1990s, social network analysis experienced work by sociologists, political scientists, and physicists such as Duncan J. Watts, Albert-László Barabási, Peter Bearman, Nicholas A. Christakis, James H. Fowler, and others, developing and applying new models and methods to emerging data available about online social networks, as well as "digital traces" regarding face-to-face networks. Levels of analysis In general, social networks are self-organizing, emergent, and complex, such that a globally coherent pattern appears from the local interaction of the elements that make up the system. These patterns become more apparent as network size increases. However, a global network analysis of, for example, all interpersonal relationships in the world is not feasible and is likely to contain so much information as to be uninformative. Practical limitations of computing power, ethics and participant recruitment and payment also limit the scope of a social network analysis. The nuances of a local system may be lost in a large network analysis, hence the quality of information may be more important than its scale for understanding network properties. Thus, social networks are analyzed at the scale relevant to the researcher's theoretical question. Although levels of analysis are not necessarily mutually exclusive, there are three general levels into which networks may fall: micro-level, meso-level, and macro-level. At the micro-level, social network research typically begins with an individual, snowballing as social relationships are traced, or may begin with a small group of individuals in a particular social context. Dyadic level: A dyad is a social relationship between two individuals. Network research on dyads may concentrate on structure of the relationship (e.g. multiplexity, strength), social equality, and tendencies toward reciprocity/mutuality. Triadic level: Add one individual to a dyad, and you have a triad. Research at this level may concentrate on factors such as balance and transitivity, as well as social equality and tendencies toward reciprocity/mutuality. In the balance theory of Fritz Heider the triad is the key to social dynamics. The discord in a rivalrous love triangle is an example of an unbalanced triad, likely to change to a balanced triad by a change in one of the relations. The dynamics of social friendships in society has been modeled by balancing triads. The study is carried forward with the theory of signed graphs. Actor level: The smallest unit of analysis in a social network is an individual in their social setting, i.e., an "actor" or "ego." Egonetwork analysis focuses on network characteristics, such as size, relationship strength, density, centrality, prestige and roles such as isolates, liaisons, and bridges. Such analyses, are most commonly used in the fields of psychology or social psychology, ethnographic kinship analysis or other genealogical studies of relationships between individuals. Subset level: Subset levels of network research problems begin at the micro-level, but may cross over into the meso-level of analysis. Subset level research may focus on distance and reachability, cliques, cohesive subgroups, or other group actions or behavior. In general, meso-level theories begin with a population size that falls between the micro- and macro-levels. However, meso-level may also refer to analyses that are specifically designed to reveal connections between micro- and macro-levels. Meso-level networks are low density and may exhibit causal processes distinct from interpersonal micro-level networks. Organizations: Formal organizations are social groups that distribute tasks for a collective goal. Network research on organizations may focus on either intra-organizational or inter-organizational ties in terms of formal or informal relationships. Intra-organizational networks themselves often contain multiple levels of analysis, especially in larger organizations with multiple branches, franchises or semi-autonomous departments. In these cases, research is often conducted at a work group level and organization level, focusing on the interplay between the two structures. Experiments with networked groups online have documented ways to optimize group-level coordination through diverse interventions, including the addition of autonomous agents to the groups. Randomly distributed networks: Exponential random graph models of social networks became state-of-the-art methods of social network analysis in the 1980s. This framework has the capacity to represent social-structural effects commonly observed in many human social networks, including general degree-based structural effects commonly observed in many human social networks as well as reciprocity and transitivity, and at the node-level, homophily and attribute-based activity and popularity effects, as derived from explicit hypotheses about dependencies among network ties. Parameters are given in terms of the prevalence of small subgraph configurations in the network and can be interpreted as describing the combinations of local social processes from which a given network emerges. These probability models for networks on a given set of actors allow generalization beyond the restrictive dyadic independence assumption of micro-networks, allowing models to be built from theoretical structural foundations of social behavior. Scale-free networks: A scale-free network is a network whose degree distribution follows a power law, at least asymptotically. In network theory a scale-free ideal network is a random network with a degree distribution that unravels the size distribution of social groups. Specific characteristics of scale-free networks vary with the theories and analytical tools used to create them, however, in general, scale-free networks have some common characteristics. One notable characteristic in a scale-free network is the relative commonness of vertices with a degree that greatly exceeds the average. The highest-degree nodes are often called "hubs", and may serve specific purposes in their networks, although this depends greatly on the social context. Another general characteristic of scale-free networks is the clustering coefficient distribution, which decreases as the node degree increases. This distribution also follows a power law. The Barabási model of network evolution shown above is an example of a scale-free network. Rather than tracing interpersonal interactions, macro-level analyses generally trace the outcomes of interactions, such as economic or other resource transfer interactions over a large population. Large-scale networks: Large-scale network is a term somewhat synonymous with "macro-level." It is primarily used in social and behavioral sciences, and in economics. Originally, the term was used extensively in the computer sciences (see large-scale network mapping). Complex networks: Most larger social networks display features of social complexity, which involves substantial non-trivial features of network topology, with patterns of complex connections between elements that are neither purely regular nor purely random (see, complexity science, dynamical system and chaos theory), as do biological, and technological networks. Such complex network features include a heavy tail in the degree distribution, a high clustering coefficient, assortativity or disassortativity among vertices, community structure (see stochastic block model), and hierarchical structure. In the case of agency-directed networks these features also include reciprocity, triad significance profile (TSP, see network motif), and other features. In contrast, many of the mathematical models of networks that have been studied in the past, such as lattices and random graphs, do not show these features. Theoretical links Various theoretical frameworks have been imported for the use of social network analysis. The most prominent of these are Graph theory, Balance theory, Social comparison theory, and more recently, the Social identity approach. Few complete theories have been produced from social network analysis. Two that have are structural role theory and heterophily theory. The basis of Heterophily Theory was the finding in one study that more numerous weak ties can be important in seeking information and innovation, as cliques have a tendency to have more homogeneous opinions as well as share many common traits. This homophilic tendency was the reason for the members of the cliques to be attracted together in the first place. However, being similar, each member of the clique would also know more or less what the other members knew. To find new information or insights, members of the clique will have to look beyond the clique to its other friends and acquaintances. This is what Granovetter called "the strength of weak ties". Structural holes In the context of networks, social capital exists where people have an advantage because of their location in a network. Contacts in a network provide information, opportunities and perspectives that can be beneficial to the central player in the network. Most social structures tend to be characterized by dense clusters of strong connections. Information within these clusters tends to be rather homogeneous and redundant. Non-redundant information is most often obtained through contacts in different clusters. When two separate clusters possess non-redundant information, there is said to be a structural hole between them. Thus, a network that bridges structural holes will provide network benefits that are in some degree additive, rather than overlapping. An ideal network structure has a vine and cluster structure, providing access to many different clusters and structural holes. Networks rich in structural holes are a form of social capital in that they offer information benefits. The main player in a network that bridges structural holes is able to access information from diverse sources and clusters. For example, in business networks, this is beneficial to an individual's career because he is more likely to hear of job openings and opportunities if his network spans a wide range of contacts in different industries/sectors. This concept is similar to Mark Granovetter's theory of weak ties, which rests on the basis that having a broad range of contacts is most effective for job attainment. Structural holes have been widely applied in social network analysis, resulting in applications in a wide range of practical scenarios as well as machine learning-based social prediction. Research clusters Research has used network analysis to examine networks created when artists are exhibited together in museum exhibition. Such networks have been shown to affect an artist's recognition in history and historical narratives, even when controlling for individual accomplishments of the artist. Other work examines how network grouping of artists can affect an individual artist's auction performance. An artist's status has been shown to increase when associated with higher status networks, though this association has diminishing returns over an artist's career. In J.A. Barnes' day, a "community" referred to a specific geographic location and studies of community ties had to do with who talked, associated, traded, and attended church with whom. Today, however, there are extended "online" communities developed through telecommunications devices and social network services. Such devices and services require extensive and ongoing maintenance and analysis, often using network science methods. Community development studies, today, also make extensive use of such methods. Complex networks require methods specific to modelling and interpreting social complexity and complex adaptive systems, including techniques of dynamic network analysis. Mechanisms such as Dual-phase evolution explain how temporal changes in connectivity contribute to the formation of structure in social networks. The study of social networks is being used to examine the nature of interdependencies between actors and the ways in which these are related to outcomes of conflict and cooperation. Areas of study include cooperative behavior among participants in collective actions such as protests; promotion of peaceful behavior, social norms, and public goods within communities through networks of informal governance; the role of social networks in both intrastate conflict and interstate conflict; and social networking among politicians, constituents, and bureaucrats. In criminology and urban sociology, much attention has been paid to the social networks among criminal actors. For example, murders can be seen as a series of exchanges between gangs. Murders can be seen to diffuse outwards from a single source, because weaker gangs cannot afford to kill members of stronger gangs in retaliation, but must commit other violent acts to maintain their reputation for strength. Diffusion of ideas and innovations studies focus on the spread and use of ideas from one actor to another or one culture and another. This line of research seeks to explain why some become "early adopters" of ideas and innovations, and links social network structure with facilitating or impeding the spread of an innovation. A case in point is the social diffusion of linguistic innovation such as neologisms. Experiments and large-scale field trials (e.g., by Nicholas Christakis and collaborators) have shown that cascades of desirable behaviors can be induced in social groups, in settings as diverse as Honduras villages, Indian slums, or in the lab. Still other experiments have documented the experimental induction of social contagion of voting behavior, emotions, risk perception, and commercial products. In demography, the study of social networks has led to new sampling methods for estimating and reaching populations that are hard to enumerate (for example, homeless people or intravenous drug users.) For example, respondent driven sampling is a network-based sampling technique that relies on respondents to a survey recommending further respondents. The field of sociology focuses almost entirely on networks of outcomes of social interactions. More narrowly, economic sociology considers behavioral interactions of individuals and groups through social capital and social "markets". Sociologists, such as Mark Granovetter, have developed core principles about the interactions of social structure, information, ability to punish or reward, and trust that frequently recur in their analyses of political, economic and other institutions. Granovetter examines how social structures and social networks can affect economic outcomes like hiring, price, productivity and innovation and describes sociologists' contributions to analyzing the impact of social structure and networks on the economy. Analysis of social networks is increasingly incorporated into health care analytics, not only in epidemiological studies but also in models of patient communication and education, disease prevention, mental health diagnosis and treatment, and in the study of health care organizations and systems. Human ecology is an interdisciplinary and transdisciplinary study of the relationship between humans and their natural, social, and built environments. The scientific philosophy of human ecology has a diffuse history with connections to geography, sociology, psychology, anthropology, zoology, and natural ecology. In the study of literary systems, network analysis has been applied by Anheier, Gerhards and Romo, De Nooy, Senekal, and Lotker, to study various aspects of how literature functions. The basic premise is that polysystem theory, which has been around since the writings of Even-Zohar, can be integrated with network theory and the relationships between different actors in the literary network, e.g. writers, critics, publishers, literary histories, etc., can be mapped using visualization from SNA. Research studies of formal or informal organization relationships, organizational communication, economics, economic sociology, and other resource transfers. Social networks have also been used to examine how organizations interact with each other, characterizing the many informal connections that link executives together, as well as associations and connections between individual employees at different organizations. Many organizational social network studies focus on teams. Within team network studies, research assesses, for example, the predictors and outcomes of centrality and power, density and centralization of team instrumental and expressive ties, and the role of between-team networks. Intra-organizational networks have been found to affect organizational commitment, organizational identification, interpersonal citizenship behaviour. Social capital is a form of economic and cultural capital in which social networks are central, transactions are marked by reciprocity, trust, and cooperation, and market agents produce goods and services not mainly for themselves, but for a common good. Social capital is split into three dimensions: the structural, the relational and the cognitive dimension. The structural dimension describes how partners interact with each other and which specific partners meet in a social network. Also, the structural dimension of social capital indicates the level of ties among organizations. This dimension is highly connected to the relational dimension which refers to trustworthiness, norms, expectations and identifications of the bonds between partners. The relational dimension explains the nature of these ties which is mainly illustrated by the level of trust accorded to the network of organizations. The cognitive dimension analyses the extent to which organizations share common goals and objectives as a result of their ties and interactions. Social capital is a sociological concept about the value of social relations and the role of cooperation and confidence to achieve positive outcomes. The term refers to the value one can get from their social ties. For example, newly arrived immigrants can make use of their social ties to established migrants to acquire jobs they may otherwise have trouble getting (e.g., because of unfamiliarity with the local language). A positive relationship exists between social capital and the intensity of social network use. In a dynamic framework, higher activity in a network feeds into higher social capital which itself encourages more activity. This particular cluster focuses on brand-image and promotional strategy effectiveness, taking into account the impact of customer participation on sales and brand-image. This is gauged through techniques such as sentiment analysis which rely on mathematical areas of study such as data mining and analytics. This area of research produces vast numbers of commercial applications as the main goal of any study is to understand consumer behaviour and drive sales. In many organizations, members tend to focus their activities inside their own groups, which stifles creativity and restricts opportunities. A player whose network bridges structural holes has an advantage in detecting and developing rewarding opportunities. Such a player can mobilize social capital by acting as a "broker" of information between two clusters that otherwise would not have been in contact, thus providing access to new ideas, opinions and opportunities. British philosopher and political economist John Stuart Mill, writes, "it is hardly possible to overrate the value of placing human beings in contact with persons dissimilar to themselves.... Such communication [is] one of the primary sources of progress." Thus, a player with a network rich in structural holes can add value to an organization through new ideas and opportunities. This in turn, helps an individual's career development and advancement. A social capital broker also reaps control benefits of being the facilitator of information flow between contacts. Full communication with exploratory mindsets and information exchange generated by dynamically alternating positions in a social network promotes creative and deep thinking. In the case of consulting firm Eden McCallum, the founders were able to advance their careers by bridging their connections with former big three consulting firm consultants and mid-size industry firms. By bridging structural holes and mobilizing social capital, players can advance their careers by executing new opportunities between contacts. There has been research that both substantiates and refutes the benefits of information brokerage. A study of high tech Chinese firms by Zhixing Xiao found that the control benefits of structural holes are "dissonant to the dominant firm-wide spirit of cooperation and the information benefits cannot materialize due to the communal sharing values" of such organizations. However, this study only analyzed Chinese firms, which tend to have strong communal sharing values. Information and control benefits of structural holes are still valuable in firms that are not quite as inclusive and cooperative on the firm-wide level. In 2004, Ronald Burt studied 673 managers who ran the supply chain for one of America's largest electronics companies. He found that managers who often discussed issues with other groups were better paid, received more positive job evaluations and were more likely to be promoted. Thus, bridging structural holes can be beneficial to an organization, and in turn, to an individual's career. Computer networks combined with social networking software produce a new medium for social interaction. A relationship over a computerized social networking service can be characterized by context, direction, and strength. The content of a relation refers to the resource that is exchanged. In a computer-mediated communication context, social pairs exchange different kinds of information, including sending a data file or a computer program as well as providing emotional support or arranging a meeting. With the rise of electronic commerce, information exchanged may also correspond to exchanges of money, goods or services in the "real" world. Social network analysis methods have become essential to examining these types of computer mediated communication. In addition, the sheer size and the volatile nature of social media has given rise to new network metrics. A key concern with networks extracted from social media is the lack of robustness of network metrics given missing data. Based on the pattern of homophily, ties between people are most likely to occur between nodes that are most similar to each other, or within neighbourhood segregation, individuals are most likely to inhabit the same regional areas as other individuals who are like them. Therefore, social networks can be used as a tool to measure the degree of segregation or homophily within a social network. Social Networks can both be used to simulate the process of homophily but it can also serve as a measure of level of exposure of different groups to each other within a current social network of individuals in a certain area. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/REXX] | [TOKENS: 3214] |
Contents Rexx Rexx (restructured extended executor) is a high-level programming language developed at IBM by Mike Cowlishaw. Both proprietary and open source Rexx interpreters exist for a wide range of computing platforms, and compilers exist for IBM mainframe computers. Rexx is used for scripting, application macros and application development. As a general purpose scripting language, Rexx is considered a precursor to Tcl and Python. Rexx is supported in a variety of environments. It is the primary scripting language in some operating systems including OS/2, MVS, VM, AmigaOS and is used for macros in some software including SPF/PC, KEDIT, THE and ZOC. With an engine installed, Rexx can be used for scripting and macros in programs that use a Windows Scripting Host ActiveX scripting engine (such as VBScript or JScript). Rexx is supplied with VM/SP Release 3 on up, TSO/E Version 2 on up, OS/2 (1.3 and later, where it is officially named Procedures Language/2), AmigaOS Version 2 on up, PC DOS (7.0 or 2000), ArcaOS, and Windows NT 4.0 (Resource Kit: Regina). In the late 1980s, Rexx became the common scripting language for IBM Systems Application Architecture, where it was renamed "SAA Procedure Language REXX". A script is associated with a Rexx interpreter at runtime in various ways based on context. In mainframe computing, a Rexx script or command is sometimes referred to as an EXEC since that is the name of the file type used for similar CMS EXEC, and EXEC 2 scripts and for Rexx scripts on VM/SP R3 through z/VM. The first line of a script specifies the use of a Rexx interpreter in a comment either by identifying the code as Rexx language or by file path via EXTPROC. On MVS, Rexx scripts may[a] be recognized by the low level qualifier "EXEC" or if the first line fetched from SYSPROC is a comment containing "REXX" then it is treated as Rexx (rather than CLIST), and a script fetched from SYSEXEC must be Rexx. On OS/2, Rexx scripts share the filename extension ".cmd" with other scripting languages, and the first line of the script specifies the interpreter to use. On Linux, Rexx scripts generally begin with a shebang. Rexx macros for Rexx-aware applications use extensions determined by the application. Name Originally, the language was called REX, short for Reformed Executor, but an extra "X" was added to avoid confusion with other products. The name was originally all uppercase because that was the only way to represent it in mainframe code at the time. Both editions of Mike Cowlishaw's first book on the language use all-caps, REXX, although the cover graphic uses mixed case. His book on NetRexx uses mixed case but all caps in the cover graphic with large and small caps, NETREXX. An expansion that matches the abbreviation, REstructured eXtended eXecutor, was used for the system product in 1984. The name Rexx (mixed case) is used in this article, and is commonly used elsewhere. Attributes Objective and subjective attributes of Rexx include: Some claim that Rexx is a relatively simple language. With only 23 instructions (such as call, parse, and select), it has a relatively small instruction set. Rexx has limited punctuation and formatting requirements. Rexx has only one data type, the character string. Some claim that such simplicities make Rexx relatively easy to debug. Some claim that Rexx code looks similar to PL/I code, but has fewer notations. With fewer notations, it tends to be is harder to parse via a translator, but is easier to write. Simplifying coding was intentional as noted by the Rexx design goal of the principle of least astonishment. History On his own time, Mike Cowlishaw developed the language and an interpreter for it in assembly language between 20 March 1979 and mid-1982 with the intent to replace the languages EXEC and EXEC 2. Mike also intended Rexx to be a simplified and easier to learn version of PL/I, but some claim that Rexx has problematic differences from PL/I. Rexx was first described in public at the SHARE 56 conference in Houston, Texas, in 1981, where customer reaction, championed by Ted Johnston of SLAC, led to it being shipped as an IBM product in 1982. Over the years IBM included Rexx in almost all of its operating systems (VM/CMS, MVS TSO/E, IBM OS/400, VSE/ESA, MUSIC/SP, AIX, PC DOS, and OS/2), and has made versions available for Novell NetWare, Windows, Java, and Linux. The first non-IBM version was written for PC DOS by Charles Daney in 1984/5 and marketed by the Mansfield Software Group (founded by Kevin J. Kearney in 1986). The first Rexx compiler appeared in 1987, written for CMS by Lundin and Woodruff. Other versions have also been developed for Atari, AmigaOS, Unix (many variants), Solaris, DEC, Windows, Windows CE, Pocket PC, DOS, Palm OS, QNX, OS/2, Linux, BeOS, EPOC32/Symbian, AtheOS, OpenVMS,: 309 Apple Macintosh, and Mac OS X. ARexx, a Rexx interpreter for Amiga, was included with AmigaOS 2 onwards and was popular for scripting and application control. Many Amiga applications have an "ARexx port" which allows control of the application via a Rexx script. Notably, a Rexx script can switch between Rexx ports to control multiple applications. In 1990, Cathie Dager of SLAC organized the first independent Rexx symposium, which led to the forming of the Rexx Language Association. Symposia are held annually. In 1992, the two most widely used open-source ports appeared: Ian Collier's REXX/imc for Unix and Anders Christensen's Regina (later adopted by Mark Hessling) for Windows and Unix. BRexx was developed by Vasilis N Vlachoudis, a nuclear scientist at CERN. It runs on a range of operating systems, including Unix, Linux, BSD, macOS and Windows. Its small size means it can run on an Android mobile phone. BRexx/370 is a version that runs on IBM mainframes.: 359–383 OS/2 has a visual development system from Watcom VX-REXX. Another dialect was VisPro REXX from Hockware. Portable Rexx by Kilowatt and Personal Rexx by Quercus are two Rexx interpreters designed for DOS and can be run under Windows as well using a command prompt. Since the mid-1990s, two newer variants of Rexx have appeared: In 1996 the American National Standards Institute (ANSI) published a standard for Rexx: ANSI X3.274–1996 "Information Technology – Programming Language REXX".[c] More than two dozen books on Rexx have been published since 1985. Rexx marked its 25th anniversary on 20 March 2004, which was celebrated at the Rexx Language Association's 15th International REXX Symposium in Böblingen, Germany, in May 2004. On October 12, 2004, IBM announced their plan to release their Object REXX implementation's sources under the Common Public License. Recent releases of Object REXX contain an ActiveX Windows Scripting Host (WSH) scripting engine implementing this version of the Rexx language. On February 22, 2005, the first public release of Open Object Rexx (ooRexx) was announced. This product contains a WSH scripting engine which allows for programming of the Windows operating system and applications with Rexx in the same fashion in which Visual Basic and JScript are implemented by the default WSH installation and Perl, Tcl, Python third-party scripting engines. In January 2018 the TIOBE index listed Rexx at position 30. Since 2018 it has been either outside the top 50, or, more frequently, outside the top 100. In 2019, the 30th Rexx Language Association Symposium marked the 40th anniversary of Rexx. The symposium was held in Hursley, England, where Rexx was first designed and implemented. Toolkits Host environment A Rexx host environment is a named interface for sending commands to an, e.g., application, operating system, subsystem. The Rexx interpreter initially has a list of known environments; the first in the list is known as the default environment. A Rexx script use the ADDRESS statement to change the default environment and may also use it to send a single command to a specific environment without changing the default environment. Syntax Rexx has three instruction types: 31 The address instruction has three roles: The ANSI standard added options for redirecting the input and output of commands. The language provides do groups for two purposes: A do group begins with do and ends with end. A single group may serve both purposes. In the related ooRexx and NetRexx, there is both a do and a loop keyword, with almost identical semantics; they differ in that a simple do is equivalent to do 1 while a simple loop is equivalent to loop forever. An iteration of a do group may be terminated with an iterate statement and the entire group may be terminated with a leave statement. Although it is valid anywhere, a simple do is specifically useful inside conditional statements: The language supports testing a condition either before (do while) or after (do until) executing a group of code via syntax: The language permits counted loops, where an expression is computed at the start of the loop and the instructions within the loop are executed that many times: A loop can increment a variable and stop when a limit is reached. The increment value is 1 if the by clause is omitted. The loop continues forever if the limit to clause is omitted, unless terminated earlier by another clause or by a leave statement. The language supports an unconditional loop via forever that continues until the loop is terminated or the program is terminated. Repetitive elements and conditional phrases can be combined in the same loop;: 50 e.g.: The language provides for conditional execution via if, then and else for a group delimited by do and end. For a single instruction, do and end can be omitted. The language provides multiple condition branching via select which derives from the SELECT; form of the PL/I SELECT statement .[d] Like similar constructs in other dynamic languages, Rexx's when clauses specify full conditions – not equality tests of a single value for the statement as some languages do. In that, they are more like cascading if-then-else code than like the C or Java switch statement. The nop instruction is required if no action is associated with a when condition. The otherwise clause is optional. If omitted and no when conditions are met, then the syntax condition is raised. Variables are typeless and initially are evaluated as their names in upper case. Thus a variable's type can vary with its use in the program: If no novalue condition handler is configured, then an undefined variable evaluates to its name, in upper case. The built-in function SYMBOL returns "VAR" for a defined variable and does not trigger novalue even if not defined. The VALUE function gets the value of a variable without triggering a novalue condition, but its main purpose is to read and set environment variables, similar to POSIX getenv and putenv. The language provides the compound variable construct which supports adding fields (called tails) to a variable (called a stem in this context) to support data structures such as lists, arrays, n-dimensional arrays, sparse or dense arrays, balanced or unbalanced trees and records. The language does not provide special support for numeric array indexing like many other languages do. Instead, a compound variable with numeric tails produce a similar effect. The following code defines variables stem.1 = 9, stem.2 = 8, stem.3 = 7... Unlike a typical array, a tail (index) need not identify (be named) an integer value. For example, the following code is valid: A default value can be assigned to a stem via . but no tail. In this case stem.3, for example, evaluates to the default value, 'Unknown'. The whole stem (including any default value) can be erased with the drop statement. By convention (not part of the language) the compound stem.0 is often used to keep track of how many items are in a stem, for example a procedure to add a word to a list might be coded like this: A stem can have multiple tails. For example: Multiple numerical tail elements can be used to provide the effect of a multi-dimensional array. Features similar to the compound variable are found in other languages including associative arrays in AWK, hashes in Perl and hash tables in Java, dynamic objects in JavaScript. Most of these languages provide a mechanism to iterate over the keys (tails) of such a construct, but this is lacking in classic Rexx. Instead, it is necessary to store additional information. For example, the following procedure might be used to count each occurrence of a word. and then later: More recent Rexx variants, including Object REXX and ooRexx, provide a construct to iterate over the tails of a stem. The parse instruction provides string-handling via syntax: parse [upper] origin [template] If upper is included then the input is converted to upper case before parsing. origin describes the input as one of the following: template can be a combination of variables, literal delimiters, and column number delimiters. Using a list of variables as template: displays: Using column number delimiters: displays: The interpret instruction evaluates its argument as a Rexx statement allowing for evaluation of code formatted at runtime. Uses include passing a function as a parameter, arbitrary precision arithmetic, use of the parse statement with programmatic templates, stemmed arrays, and sparse arrays.[how?] The following example displays 16 and exits. The Valour software package relied upon Rexx's interpretive ability to implement an OOP environment.[citation needed] Another use was found in an unreleased Westinghouse product called Time Machine that was able to fully recover following an otherwise fatal error.[citation needed] Calculation of the value √2: Output: SqRt 2 = 1.414213562373095048801688724209698078569671875377 Calculation of the value e: Output: e = 2.7182818284590452353602874713526624977572470936998 The signal instruction configures the runtime to run custom code to handle a system condition if triggered. Conditions include: The following fragment prints a message when the user terminates (halts) it: Since Rexx version 4, a handler can be named. In the following example, the handler ChangeCodePage.Trap is configured to handle a syntax condition. When a condition is handled (as configured via signal on), the condition can be analyzed via RC which indicates the last error code and SIGL which indicates the line number of the code that triggered the condition. See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/w/index.php?title=Social_network&action=edit§ion=7] | [TOKENS: 1430] |
Editing Social network (section) Copy and paste: – — ° ′ ″ ≈ ≠ ≤ ≥ ± − × ÷ ← → · § Cite your sources: <ref></ref> {{}} {{{}}} | [] [[]] [[Category:]] #REDIRECT [[]] <s></s> <sup></sup> <sub></sub> <code></code> <pre></pre> <blockquote></blockquote> <ref></ref> <ref name="" /> {{Reflist}} <references /> <includeonly></includeonly> <noinclude></noinclude> {{DEFAULTSORT:}} <nowiki></nowiki> <!-- --> <span class="plainlinks"></span> Symbols: ~ | ¡ ¿ † ‡ ↔ ↑ ↓ • ¶ # ∞ ‹› «» ¤ ₳ ฿ ₵ ¢ ₡ ₢ $ ₫ ₯ € ₠ ₣ ƒ ₴ ₭ ₤ ℳ ₥ ₦ ₧ ₰ £ ៛ ₨ ₪ ৳ ₮ ₩ ¥ ♠ ♣ ♥ ♦ 𝄫 ♭ ♮ ♯ 𝄪 © ¼ ½ ¾ Latin: A a Á á À à  â Ä ä Ǎ ǎ Ă ă Ā ā à ã Å å Ą ą Æ æ Ǣ ǣ B b C c Ć ć Ċ ċ Ĉ ĉ Č č Ç ç D d Ď ď Đ đ Ḍ ḍ Ð ð E e É é È è Ė ė Ê ê Ë ë Ě ě Ĕ ĕ Ē ē Ẽ ẽ Ę ę Ẹ ẹ Ɛ ɛ Ǝ ǝ Ə ə F f G g Ġ ġ Ĝ ĝ Ğ ğ Ģ ģ H h Ĥ ĥ Ħ ħ Ḥ ḥ I i İ ı Í í Ì ì Î î Ï ï Ǐ ǐ Ĭ ĭ Ī ī Ĩ ĩ Į į Ị ị J j Ĵ ĵ K k Ķ ķ L l Ĺ ĺ Ŀ ŀ Ľ ľ Ļ ļ Ł ł Ḷ ḷ Ḹ ḹ M m Ṃ ṃ N n Ń ń Ň ň Ñ ñ Ņ ņ Ṇ ṇ Ŋ ŋ O o Ó ó Ò ò Ô ô Ö ö Ǒ ǒ Ŏ ŏ Ō ō Õ õ Ǫ ǫ Ọ ọ Ő ő Ø ø Œ œ Ɔ ɔ P p Q q R r Ŕ ŕ Ř ř Ŗ ŗ Ṛ ṛ Ṝ ṝ S s Ś ś Ŝ ŝ Š š Ş ş Ș ș Ṣ ṣ ß T t Ť ť Ţ ţ Ț ț Ṭ ṭ Þ þ U u Ú ú Ù ù Û û Ü ü Ǔ ǔ Ŭ ŭ Ū ū Ũ ũ Ů ů Ų ų Ụ ụ Ű ű Ǘ ǘ Ǜ ǜ Ǚ ǚ Ǖ ǖ V v W w Ŵ ŵ X x Y y Ý ý Ŷ ŷ Ÿ ÿ Ỹ ỹ Ȳ ȳ Z z Ź ź Ż ż Ž ž ß Ð ð Þ þ Ŋ ŋ Ə ə Greek: Ά ά Έ έ Ή ή Ί ί Ό ό Ύ ύ Ώ ώ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω {{Polytonic|}} Cyrillic: А а Б б В в Г г Ґ ґ Ѓ ѓ Д д Ђ ђ Е е Ё ё Є є Ж ж З з Ѕ ѕ И и І і Ї ї Й й Ј ј К к Ќ ќ Л л Љ љ М м Н н Њ њ О о П п Р р С с Т т Ћ ћ У у Ў ў Ф ф Х х Ц ц Ч ч Џ џ Ш ш Щ щ Ъ ъ Ы ы Ь ь Э э Ю ю Я я ́ IPA: t̪ d̪ ʈ ɖ ɟ ɡ ɢ ʡ ʔ ɸ β θ ð ʃ ʒ ɕ ʑ ʂ ʐ ç ʝ ɣ χ ʁ ħ ʕ ʜ ʢ ɦ ɱ ɳ ɲ ŋ ɴ ʋ ɹ ɻ ɰ ʙ ⱱ ʀ ɾ ɽ ɫ ɬ ɮ ɺ ɭ ʎ ʟ ɥ ʍ ɧ ʼ ɓ ɗ ʄ ɠ ʛ ʘ ǀ ǃ ǂ ǁ ɨ ʉ ɯ ɪ ʏ ʊ ø ɘ ɵ ɤ ə ɚ ɛ œ ɜ ɝ ɞ ʌ ɔ æ ɐ ɶ ɑ ɒ ʰ ʱ ʷ ʲ ˠ ˤ ⁿ ˡ ˈ ˌ ː ˑ ̪ {{IPA|}} This page is a member of 6 hidden categories (help): |
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[SOURCE: https://en.wikipedia.org/wiki/PlayStation_(console)#cite_note-SCEE_2000—Key_Facts_and_Figures-169] | [TOKENS: 10728] |
Contents PlayStation (console) The PlayStation[a] (codenamed PSX, abbreviated as PS, and retroactively PS1 or PS one) is a home video game console developed and marketed by Sony Computer Entertainment. It was released in Japan on 3 December 1994, followed by North America on 9 September 1995, Europe on 29 September 1995, and other regions following thereafter. As a fifth-generation console, the PlayStation primarily competed with the Nintendo 64 and the Sega Saturn. Sony began developing the PlayStation after a failed venture with Nintendo to create a CD-ROM peripheral for the Super Nintendo Entertainment System in the early 1990s. The console was primarily designed by Ken Kutaragi and Sony Computer Entertainment in Japan, while additional development was outsourced in the United Kingdom. An emphasis on 3D polygon graphics was placed at the forefront of the console's design. PlayStation game production was designed to be streamlined and inclusive, enticing the support of many third party developers. The console proved popular for its extensive game library, popular franchises, low retail price, and aggressive youth marketing which advertised it as the preferable console for adolescents and adults. Critically acclaimed games that defined the console include Gran Turismo, Crash Bandicoot, Spyro the Dragon, Tomb Raider, Resident Evil, Metal Gear Solid, Tekken 3, and Final Fantasy VII. Sony ceased production of the PlayStation on 23 March 2006—over eleven years after it had been released, and in the same year the PlayStation 3 debuted. More than 4,000 PlayStation games were released, with cumulative sales of 962 million units. The PlayStation signaled Sony's rise to power in the video game industry. It received acclaim and sold strongly; in less than a decade, it became the first computer entertainment platform to ship over 100 million units. Its use of compact discs heralded the game industry's transition from cartridges. The PlayStation's success led to a line of successors, beginning with the PlayStation 2 in 2000. In the same year, Sony released a smaller and cheaper model, the PS one. History The PlayStation was conceived by Ken Kutaragi, a Sony executive who managed a hardware engineering division and was later dubbed "the Father of the PlayStation". Kutaragi's interest in working with video games stemmed from seeing his daughter play games on Nintendo's Famicom. Kutaragi convinced Nintendo to use his SPC-700 sound processor in the Super Nintendo Entertainment System (SNES) through a demonstration of the processor's capabilities. His willingness to work with Nintendo was derived from both his admiration of the Famicom and conviction in video game consoles becoming the main home-use entertainment systems. Although Kutaragi was nearly fired because he worked with Nintendo without Sony's knowledge, president Norio Ohga recognised the potential in Kutaragi's chip and decided to keep him as a protégé. The inception of the PlayStation dates back to a 1988 joint venture between Nintendo and Sony. Nintendo had produced floppy disk technology to complement cartridges in the form of the Family Computer Disk System, and wanted to continue this complementary storage strategy for the SNES. Since Sony was already contracted to produce the SPC-700 sound processor for the SNES, Nintendo contracted Sony to develop a CD-ROM add-on, tentatively titled the "Play Station" or "SNES-CD". The PlayStation name had already been trademarked by Yamaha, but Nobuyuki Idei liked it so much that he agreed to acquire it for an undisclosed sum rather than search for an alternative. Sony was keen to obtain a foothold in the rapidly expanding video game market. Having been the primary manufacturer of the MSX home computer format, Sony had wanted to use their experience in consumer electronics to produce their own video game hardware. Although the initial agreement between Nintendo and Sony was about producing a CD-ROM drive add-on, Sony had also planned to develop a SNES-compatible Sony-branded console. This iteration was intended to be more of a home entertainment system, playing both SNES cartridges and a new CD format named the "Super Disc", which Sony would design. Under the agreement, Sony would retain sole international rights to every Super Disc game, giving them a large degree of control despite Nintendo's leading position in the video game market. Furthermore, Sony would also be the sole benefactor of licensing related to music and film software that it had been aggressively pursuing as a secondary application. The Play Station was to be announced at the 1991 Consumer Electronics Show (CES) in Las Vegas. However, Nintendo president Hiroshi Yamauchi was wary of Sony's increasing leverage at this point and deemed the original 1988 contract unacceptable upon realising it essentially handed Sony control over all games written on the SNES CD-ROM format. Although Nintendo was dominant in the video game market, Sony possessed a superior research and development department. Wanting to protect Nintendo's existing licensing structure, Yamauchi cancelled all plans for the joint Nintendo–Sony SNES CD attachment without telling Sony. He sent Nintendo of America president Minoru Arakawa (his son-in-law) and chairman Howard Lincoln to Amsterdam to form a more favourable contract with Dutch conglomerate Philips, Sony's rival. This contract would give Nintendo total control over their licences on all Philips-produced machines. Kutaragi and Nobuyuki Idei, Sony's director of public relations at the time, learned of Nintendo's actions two days before the CES was due to begin. Kutaragi telephoned numerous contacts, including Philips, to no avail. On the first day of the CES, Sony announced their partnership with Nintendo and their new console, the Play Station. At 9 am on the next day, in what has been called "the greatest ever betrayal" in the industry, Howard Lincoln stepped onto the stage and revealed that Nintendo was now allied with Philips and would abandon their work with Sony. Incensed by Nintendo's renouncement, Ohga and Kutaragi decided that Sony would develop their own console. Nintendo's contract-breaking was met with consternation in the Japanese business community, as they had broken an "unwritten law" of native companies not turning against each other in favour of foreign ones. Sony's American branch considered allying with Sega to produce a CD-ROM-based machine called the Sega Multimedia Entertainment System, but the Sega board of directors in Tokyo vetoed the idea when Sega of America CEO Tom Kalinske presented them the proposal. Kalinske recalled them saying: "That's a stupid idea, Sony doesn't know how to make hardware. They don't know how to make software either. Why would we want to do this?" Sony halted their research, but decided to develop what it had developed with Nintendo and Sega into a console based on the SNES. Despite the tumultuous events at the 1991 CES, negotiations between Nintendo and Sony were still ongoing. A deal was proposed: the Play Station would still have a port for SNES games, on the condition that it would still use Kutaragi's audio chip and that Nintendo would own the rights and receive the bulk of the profits. Roughly two hundred prototype machines were created, and some software entered development. Many within Sony were still opposed to their involvement in the video game industry, with some resenting Kutaragi for jeopardising the company. Kutaragi remained adamant that Sony not retreat from the growing industry and that a deal with Nintendo would never work. Knowing that they had to take decisive action, Sony severed all ties with Nintendo on 4 May 1992. To determine the fate of the PlayStation project, Ohga chaired a meeting in June 1992, consisting of Kutaragi and several senior Sony board members. Kutaragi unveiled a proprietary CD-ROM-based system he had been secretly working on which played games with immersive 3D graphics. Kutaragi was confident that his LSI chip could accommodate one million logic gates, which exceeded the capabilities of Sony's semiconductor division at the time. Despite gaining Ohga's enthusiasm, there remained opposition from a majority present at the meeting. Older Sony executives also opposed it, who saw Nintendo and Sega as "toy" manufacturers. The opposers felt the game industry was too culturally offbeat and asserted that Sony should remain a central player in the audiovisual industry, where companies were familiar with one another and could conduct "civili[s]ed" business negotiations. After Kutaragi reminded him of the humiliation he suffered from Nintendo, Ohga retained the project and became one of Kutaragi's most staunch supporters. Ohga shifted Kutaragi and nine of his team from Sony's main headquarters to Sony Music Entertainment Japan (SMEJ), a subsidiary of the main Sony group, so as to retain the project and maintain relationships with Philips for the MMCD development project. The involvement of SMEJ proved crucial to the PlayStation's early development as the process of manufacturing games on CD-ROM format was similar to that used for audio CDs, with which Sony's music division had considerable experience. While at SMEJ, Kutaragi worked with Epic/Sony Records founder Shigeo Maruyama and Akira Sato; both later became vice-presidents of the division that ran the PlayStation business. Sony Computer Entertainment (SCE) was jointly established by Sony and SMEJ to handle the company's ventures into the video game industry. On 27 October 1993, Sony publicly announced that it was entering the game console market with the PlayStation. According to Maruyama, there was uncertainty over whether the console should primarily focus on 2D, sprite-based graphics or 3D polygon graphics. After Sony witnessed the success of Sega's Virtua Fighter (1993) in Japanese arcades, the direction of the PlayStation became "instantly clear" and 3D polygon graphics became the console's primary focus. SCE president Teruhisa Tokunaka expressed gratitude for Sega's timely release of Virtua Fighter as it proved "just at the right time" that making games with 3D imagery was possible. Maruyama claimed that Sony further wanted to emphasise the new console's ability to utilise redbook audio from the CD-ROM format in its games alongside high quality visuals and gameplay. Wishing to distance the project from the failed enterprise with Nintendo, Sony initially branded the PlayStation the "PlayStation X" (PSX). Sony formed their European division and North American division, known as Sony Computer Entertainment Europe (SCEE) and Sony Computer Entertainment America (SCEA), in January and May 1995. The divisions planned to market the new console under the alternative branding "PSX" following the negative feedback regarding "PlayStation" in focus group studies. Early advertising prior to the console's launch in North America referenced PSX, but the term was scrapped before launch. The console was not marketed with Sony's name in contrast to Nintendo's consoles. According to Phil Harrison, much of Sony's upper management feared that the Sony brand would be tarnished if associated with the console, which they considered a "toy". Since Sony had no experience in game development, it had to rely on the support of third-party game developers. This was in contrast to Sega and Nintendo, which had versatile and well-equipped in-house software divisions for their arcade games and could easily port successful games to their home consoles. Recent consoles like the Atari Jaguar and 3DO suffered low sales due to a lack of developer support, prompting Sony to redouble their efforts in gaining the endorsement of arcade-savvy developers. A team from Epic Sony visited more than a hundred companies throughout Japan in May 1993 in hopes of attracting game creators with the PlayStation's technological appeal. Sony found that many disliked Nintendo's practices, such as favouring their own games over others. Through a series of negotiations, Sony acquired initial support from Namco, Konami, and Williams Entertainment, as well as 250 other development teams in Japan alone. Namco in particular was interested in developing for PlayStation since Namco rivalled Sega in the arcade market. Attaining these companies secured influential games such as Ridge Racer (1993) and Mortal Kombat 3 (1995), Ridge Racer being one of the most popular arcade games at the time, and it was already confirmed behind closed doors that it would be the PlayStation's first game by December 1993, despite Namco being a longstanding Nintendo developer. Namco's research managing director Shegeichi Nakamura met with Kutaragi in 1993 to discuss the preliminary PlayStation specifications, with Namco subsequently basing the Namco System 11 arcade board on PlayStation hardware and developing Tekken to compete with Virtua Fighter. The System 11 launched in arcades several months before the PlayStation's release, with the arcade release of Tekken in September 1994. Despite securing the support of various Japanese studios, Sony had no developers of their own by the time the PlayStation was in development. This changed in 1993 when Sony acquired the Liverpudlian company Psygnosis (later renamed SCE Liverpool) for US$48 million, securing their first in-house development team. The acquisition meant that Sony could have more launch games ready for the PlayStation's release in Europe and North America. Ian Hetherington, Psygnosis' co-founder, was disappointed after receiving early builds of the PlayStation and recalled that the console "was not fit for purpose" until his team got involved with it. Hetherington frequently clashed with Sony executives over broader ideas; at one point it was suggested that a television with a built-in PlayStation be produced. In the months leading up to the PlayStation's launch, Psygnosis had around 500 full-time staff working on games and assisting with software development. The purchase of Psygnosis marked another turning point for the PlayStation as it played a vital role in creating the console's development kits. While Sony had provided MIPS R4000-based Sony NEWS workstations for PlayStation development, Psygnosis employees disliked the thought of developing on these expensive workstations and asked Bristol-based SN Systems to create an alternative PC-based development system. Andy Beveridge and Martin Day, owners of SN Systems, had previously supplied development hardware for other consoles such as the Mega Drive, Atari ST, and the SNES. When Psygnosis arranged an audience for SN Systems with Sony's Japanese executives at the January 1994 CES in Las Vegas, Beveridge and Day presented their prototype of the condensed development kit, which could run on an ordinary personal computer with two extension boards. Impressed, Sony decided to abandon their plans for a workstation-based development system in favour of SN Systems's, thus securing a cheaper and more efficient method for designing software. An order of over 600 systems followed, and SN Systems supplied Sony with additional software such as an assembler, linker, and a debugger. SN Systems produced development kits for future PlayStation systems, including the PlayStation 2 and was bought out by Sony in 2005. Sony strived to make game production as streamlined and inclusive as possible, in contrast to the relatively isolated approach of Sega and Nintendo. Phil Harrison, representative director of SCEE, believed that Sony's emphasis on developer assistance reduced most time-consuming aspects of development. As well as providing programming libraries, SCE headquarters in London, California, and Tokyo housed technical support teams that could work closely with third-party developers if needed. Sony did not favour their own over non-Sony products, unlike Nintendo; Peter Molyneux of Bullfrog Productions admired Sony's open-handed approach to software developers and lauded their decision to use PCs as a development platform, remarking that "[it was] like being released from jail in terms of the freedom you have". Another strategy that helped attract software developers was the PlayStation's use of the CD-ROM format instead of traditional cartridges. Nintendo cartridges were expensive to manufacture, and the company controlled all production, prioritising their own games, while inexpensive compact disc manufacturing occurred at dozens of locations around the world. The PlayStation's architecture and interconnectability with PCs was beneficial to many software developers. The use of the programming language C proved useful, as it safeguarded future compatibility of the machine should developers decide to make further hardware revisions. Despite the inherent flexibility, some developers found themselves restricted due to the console's lack of RAM. While working on beta builds of the PlayStation, Molyneux observed that its MIPS processor was not "quite as bullish" compared to that of a fast PC and said that it took his team two weeks to port their PC code to the PlayStation development kits and another fortnight to achieve a four-fold speed increase. An engineer from Ocean Software, one of Europe's largest game developers at the time, thought that allocating RAM was a challenging aspect given the 3.5 megabyte restriction. Kutaragi said that while it would have been easy to double the amount of RAM for the PlayStation, the development team refrained from doing so to keep the retail cost down. Kutaragi saw the biggest challenge in developing the system to be balancing the conflicting goals of high performance, low cost, and being easy to program for, and felt he and his team were successful in this regard. Its technical specifications were finalised in 1993 and its design during 1994. The PlayStation name and its final design were confirmed during a press conference on May 10, 1994, although the price and release dates had not been disclosed yet. Sony released the PlayStation in Japan on 3 December 1994, a week after the release of the Sega Saturn, at a price of ¥39,800. Sales in Japan began with a "stunning" success with long queues in shops. Ohga later recalled that he realised how important PlayStation had become for Sony when friends and relatives begged for consoles for their children. PlayStation sold 100,000 units on the first day and two million units within six months, although the Saturn outsold the PlayStation in the first few weeks due to the success of Virtua Fighter. By the end of 1994, 300,000 PlayStation units were sold in Japan compared to 500,000 Saturn units. A grey market emerged for PlayStations shipped from Japan to North America and Europe, with buyers of such consoles paying up to £700. "When September 1995 arrived and Sony's Playstation roared out of the gate, things immediately felt different than [sic] they did with the Saturn launch earlier that year. Sega dropped the Saturn $100 to match the Playstation's $299 debut price, but sales weren't even close—Playstations flew out the door as fast as we could get them in stock. Before the release in North America, Sega and Sony presented their consoles at the first Electronic Entertainment Expo (E3) in Los Angeles on 11 May 1995. At their keynote presentation, Sega of America CEO Tom Kalinske revealed that their Saturn console would be released immediately to select retailers at a price of $399. Next came Sony's turn: Olaf Olafsson, the head of SCEA, summoned Steve Race, the head of development, to the conference stage, who said "$299" and left the audience with a round of applause. The attention to the Sony conference was further bolstered by the surprise appearance of Michael Jackson and the showcase of highly anticipated games, including Wipeout (1995), Ridge Racer and Tekken (1994). In addition, Sony announced that no games would be bundled with the console. Although the Saturn had released early in the United States to gain an advantage over the PlayStation, the surprise launch upset many retailers who were not informed in time, harming sales. Some retailers such as KB Toys responded by dropping the Saturn entirely. The PlayStation went on sale in North America on 9 September 1995. It sold more units within two days than the Saturn had in five months, with almost all of the initial shipment of 100,000 units sold in advance and shops across the country running out of consoles and accessories. The well-received Ridge Racer contributed to the PlayStation's early success, — with some critics considering it superior to Sega's arcade counterpart Daytona USA (1994) — as did Battle Arena Toshinden (1995). There were over 100,000 pre-orders placed and 17 games available on the market by the time of the PlayStation's American launch, in comparison to the Saturn's six launch games. The PlayStation released in Europe on 29 September 1995 and in Australia on 15 November 1995. By November it had already outsold the Saturn by three to one in the United Kingdom, where Sony had allocated a £20 million marketing budget during the Christmas season compared to Sega's £4 million. Sony found early success in the United Kingdom by securing listings with independent shop owners as well as prominent High Street chains such as Comet and Argos. Within its first year, the PlayStation secured over 20% of the entire American video game market. From September to the end of 1995, sales in the United States amounted to 800,000 units, giving the PlayStation a commanding lead over the other fifth-generation consoles,[b] though the SNES and Mega Drive from the fourth generation still outsold it. Sony reported that the attach rate of sold games and consoles was four to one. To meet increasing demand, Sony chartered jumbo jets and ramped up production in Europe and North America. By early 1996, the PlayStation had grossed $2 billion (equivalent to $4.106 billion 2025) from worldwide hardware and software sales. By late 1996, sales in Europe totalled 2.2 million units, including 700,000 in the UK. Approximately 400 PlayStation games were in development, compared to around 200 games being developed for the Saturn and 60 for the Nintendo 64. In India, the PlayStation was launched in test market during 1999–2000 across Sony showrooms, selling 100 units. Sony finally launched the console (PS One model) countrywide on 24 January 2002 with the price of Rs 7,990 and 26 games available from start. PlayStation was also doing well in markets where it was never officially released. For example, in Brazil, due to the registration of the trademark by a third company, the console could not be released, which was why the market was taken over by the officially distributed Sega Saturn during the first period, but as the Sega console withdraws, PlayStation imports and large piracy increased. In another market, China, the most popular 32-bit console was Sega Saturn, but after leaving the market, PlayStation grown with a base of 300,000 users until January 2000, although Sony China did not have plans to release it. The PlayStation was backed by a successful marketing campaign, allowing Sony to gain an early foothold in Europe and North America. Initially, PlayStation demographics were skewed towards adults, but the audience broadened after the first price drop. While the Saturn was positioned towards 18- to 34-year-olds, the PlayStation was initially marketed exclusively towards teenagers. Executives from both Sony and Sega reasoned that because younger players typically looked up to older, more experienced players, advertising targeted at teens and adults would draw them in too. Additionally, Sony found that adults reacted best to advertising aimed at teenagers; Lee Clow surmised that people who started to grow into adulthood regressed and became "17 again" when they played video games. The console was marketed with advertising slogans stylised as "LIVE IN YUR WRLD. PLY IN URS" (Live in Your World. Play in Ours.) and "U R NOT E" (red E). The four geometric shapes were derived from the symbols for the four buttons on the controller. Clow thought that by invoking such provocative statements, gamers would respond to the contrary and say "'Bullshit. Let me show you how ready I am.'" As the console's appeal enlarged, Sony's marketing efforts broadened from their earlier focus on mature players to specifically target younger children as well. Shortly after the PlayStation's release in Europe, Sony tasked marketing manager Geoff Glendenning with assessing the desires of a new target audience. Sceptical over Nintendo and Sega's reliance on television campaigns, Glendenning theorised that young adults transitioning from fourth-generation consoles would feel neglected by marketing directed at children and teenagers. Recognising the influence early 1990s underground clubbing and rave culture had on young people, especially in the United Kingdom, Glendenning felt that the culture had become mainstream enough to help cultivate PlayStation's emerging identity. Sony partnered with prominent nightclub owners such as Ministry of Sound and festival promoters to organise dedicated PlayStation areas where demonstrations of select games could be tested. Sheffield-based graphic design studio The Designers Republic was contracted by Sony to produce promotional materials aimed at a fashionable, club-going audience. Psygnosis' Wipeout in particular became associated with nightclub culture as it was widely featured in venues. By 1997, there were 52 nightclubs in the United Kingdom with dedicated PlayStation rooms. Glendenning recalled that he had discreetly used at least £100,000 a year in slush fund money to invest in impromptu marketing. In 1996, Sony expanded their CD production facilities in the United States due to the high demand for PlayStation games, increasing their monthly output from 4 million discs to 6.5 million discs. This was necessary because PlayStation sales were running at twice the rate of Saturn sales, and its lead dramatically increased when both consoles dropped in price to $199 that year. The PlayStation also outsold the Saturn at a similar ratio in Europe during 1996, with 2.2 million consoles sold in the region by the end of the year. Sales figures for PlayStation hardware and software only increased following the launch of the Nintendo 64. Tokunaka speculated that the Nintendo 64 launch had actually helped PlayStation sales by raising public awareness of the gaming market through Nintendo's added marketing efforts. Despite this, the PlayStation took longer to achieve dominance in Japan. Tokunaka said that, even after the PlayStation and Saturn had been on the market for nearly two years, the competition between them was still "very close", and neither console had led in sales for any meaningful length of time. By 1998, Sega, encouraged by their declining market share and significant financial losses, launched the Dreamcast as a last-ditch attempt to stay in the industry. Although its launch was successful, the technically superior 128-bit console was unable to subdue Sony's dominance in the industry. Sony still held 60% of the overall video game market share in North America at the end of 1999. Sega's initial confidence in their new console was undermined when Japanese sales were lower than expected, with disgruntled Japanese consumers reportedly returning their Dreamcasts in exchange for PlayStation software. On 2 March 1999, Sony officially revealed details of the PlayStation 2, which Kutaragi announced would feature a graphics processor designed to push more raw polygons than any console in history, effectively rivalling most supercomputers. The PlayStation continued to sell strongly at the turn of the new millennium: in June 2000, Sony released the PSOne, a smaller, redesigned variant which went on to outsell all other consoles in that year, including the PlayStation 2. In 2005, PlayStation became the first console to ship 100 million units with the PlayStation 2 later achieving this faster than its predecessor. The combined successes of both PlayStation consoles led to Sega retiring the Dreamcast in 2001, and abandoning the console business entirely. The PlayStation was eventually discontinued on 23 March 2006—over eleven years after its release, and less than a year before the debut of the PlayStation 3. Hardware The main microprocessor is a R3000 CPU made by LSI Logic operating at a clock rate of 33.8688 MHz and 30 MIPS. This 32-bit CPU relies heavily on the "cop2" 3D and matrix math coprocessor on the same die to provide the necessary speed to render complex 3D graphics. The role of the separate GPU chip is to draw 2D polygons and apply shading and textures to them: the rasterisation stage of the graphics pipeline. Sony's custom 16-bit sound chip supports ADPCM sources with up to 24 sound channels and offers a sampling rate of up to 44.1 kHz and music sequencing. It features 2 MB of main RAM, with an additional 1 MB of video RAM. The PlayStation has a maximum colour depth of 16.7 million true colours with 32 levels of transparency and unlimited colour look-up tables. The PlayStation can output composite, S-Video or RGB video signals through its AV Multi connector (with older models also having RCA connectors for composite), displaying resolutions from 256×224 to 640×480 pixels. Different games can use different resolutions. Earlier models also had proprietary parallel and serial ports that could be used to connect accessories or multiple consoles together; these were later removed due to a lack of usage. The PlayStation uses a proprietary video compression unit, MDEC, which is integrated into the CPU and allows for the presentation of full motion video at a higher quality than other consoles of its generation. Unusual for the time, the PlayStation lacks a dedicated 2D graphics processor; 2D elements are instead calculated as polygons by the Geometry Transfer Engine (GTE) so that they can be processed and displayed on screen by the GPU. While running, the GPU can also generate a total of 4,000 sprites and 180,000 polygons per second, in addition to 360,000 per second flat-shaded. The PlayStation went through a number of variants during its production run. Externally, the most notable change was the gradual reduction in the number of external connectors from the rear of the unit. This started with the original Japanese launch units; the SCPH-1000, released on 3 December 1994, was the only model that had an S-Video port, as it was removed from the next model. Subsequent models saw a reduction in number of parallel ports, with the final version only retaining one serial port. Sony marketed a development kit for amateur developers known as the Net Yaroze (meaning "Let's do it together" in Japanese). It was launched in June 1996 in Japan, and following public interest, was released the next year in other countries. The Net Yaroze allowed hobbyists to create their own games and upload them via an online forum run by Sony. The console was only available to buy through an ordering service and with the necessary documentation and software to program PlayStation games and applications through C programming compilers. On 7 July 2000, Sony released the PS One (stylised as "PS one" or "PSone"), a smaller, redesigned version of the original PlayStation. It was the highest-selling console through the end of the year, outselling all other consoles—including the PlayStation 2. In 2002, Sony released a 5-inch (130 mm) LCD screen add-on for the PS One, referred to as the "Combo pack". It also included a car cigarette lighter adaptor adding an extra layer of portability. Production of the LCD "Combo Pack" ceased in 2004, when the popularity of the PlayStation began to wane in markets outside Japan. A total of 28.15 million PS One units had been sold by the time it was discontinued in March 2006. Three iterations of the PlayStation's controller were released over the console's lifespan. The first controller, the PlayStation controller, was released alongside the PlayStation in December 1994. It features four individual directional buttons (as opposed to a conventional D-pad), a pair of shoulder buttons on both sides, Start and Select buttons in the centre, and four face buttons consisting of simple geometric shapes: a green triangle, red circle, blue cross, and a pink square (, , , ). Rather than depicting traditionally used letters or numbers onto its buttons, the PlayStation controller established a trademark which would be incorporated heavily into the PlayStation brand. Teiyu Goto, the designer of the original PlayStation controller, said that the circle and cross represent "yes" and "no", respectively (though this layout is reversed in Western versions); the triangle symbolises a point of view and the square is equated to a sheet of paper to be used to access menus. The European and North American models of the original PlayStation controllers are roughly 10% larger than its Japanese variant, to account for the fact the average person in those regions has larger hands than the average Japanese person. Sony's first analogue gamepad, the PlayStation Analog Joystick (often erroneously referred to as the "Sony Flightstick"), was first released in Japan in April 1996. Featuring two parallel joysticks, it uses potentiometer technology previously used on consoles such as the Vectrex; instead of relying on binary eight-way switches, the controller detects minute angular changes through the entire range of motion. The stick also features a thumb-operated digital hat switch on the right joystick, corresponding to the traditional D-pad, and used for instances when simple digital movements were necessary. The Analog Joystick sold poorly in Japan due to its high cost and cumbersome size. The increasing popularity of 3D games prompted Sony to add analogue sticks to its controller design to give users more freedom over their movements in virtual 3D environments. The first official analogue controller, the Dual Analog Controller, was revealed to the public in a small glass booth at the 1996 PlayStation Expo in Japan, and released in April 1997 to coincide with the Japanese releases of analogue-capable games Tobal 2 and Bushido Blade. In addition to the two analogue sticks (which also introduced two new buttons mapped to clicking in the analogue sticks), the Dual Analog controller features an "Analog" button and LED beneath the "Start" and "Select" buttons which toggles analogue functionality on or off. The controller also features rumble support, though Sony decided that haptic feedback would be removed from all overseas iterations before the United States release. A Sony spokesman stated that the feature was removed for "manufacturing reasons", although rumours circulated that Nintendo had attempted to legally block the release of the controller outside Japan due to similarities with the Nintendo 64 controller's Rumble Pak. However, a Nintendo spokesman denied that Nintendo took legal action. Next Generation's Chris Charla theorised that Sony dropped vibration feedback to keep the price of the controller down. In November 1997, Sony introduced the DualShock controller. Its name derives from its use of two (dual) vibration motors (shock). Unlike its predecessor, its analogue sticks feature textured rubber grips, longer handles, slightly different shoulder buttons and has rumble feedback included as standard on all versions. The DualShock later replaced its predecessors as the default controller. Sony released a series of peripherals to add extra layers of functionality to the PlayStation. Such peripherals include memory cards, the PlayStation Mouse, the PlayStation Link Cable, the Multiplayer Adapter (a four-player multitap), the Memory Drive (a disk drive for 3.5-inch floppy disks), the GunCon (a light gun), and the Glasstron (a monoscopic head-mounted display). Released exclusively in Japan, the PocketStation is a memory card peripheral which acts as a miniature personal digital assistant. The device features a monochrome liquid crystal display (LCD), infrared communication capability, a real-time clock, built-in flash memory, and sound capability. Sharing similarities with the Dreamcast's VMU peripheral, the PocketStation was typically distributed with certain PlayStation games, enhancing them with added features. The PocketStation proved popular in Japan, selling over five million units. Sony planned to release the peripheral outside Japan but the release was cancelled, despite receiving promotion in Europe and North America. In addition to playing games, most PlayStation models are equipped to play CD-Audio. The Asian model SCPH-5903 can also play Video CDs. Like most CD players, the PlayStation can play songs in a programmed order, shuffle the playback order of the disc and repeat one song or the entire disc. Later PlayStation models use a music visualisation function called SoundScope. This function, as well as a memory card manager, is accessed by starting the console without either inserting a game or closing the CD tray, thereby accessing a graphical user interface (GUI) for the PlayStation BIOS. The GUI for the PS One and PlayStation differ depending on the firmware version: the original PlayStation GUI had a dark blue background with rainbow graffiti used as buttons, while the early PAL PlayStation and PS One GUI had a grey blocked background with two icons in the middle. PlayStation emulation is versatile and can be run on numerous modern devices. Bleem! was a commercial emulator which was released for IBM-compatible PCs and the Dreamcast in 1999. It was notable for being aggressively marketed during the PlayStation's lifetime, and was the centre of multiple controversial lawsuits filed by Sony. Bleem! was programmed in assembly language, which allowed it to emulate PlayStation games with improved visual fidelity, enhanced resolutions, and filtered textures that was not possible on original hardware. Sony sued Bleem! two days after its release, citing copyright infringement and accusing the company of engaging in unfair competition and patent infringement by allowing use of PlayStation BIOSs on a Sega console. Bleem! were subsequently forced to shut down in November 2001. Sony was aware that using CDs for game distribution could have left games vulnerable to piracy, due to the growing popularity of CD-R and optical disc drives with burning capability. To preclude illegal copying, a proprietary process for PlayStation disc manufacturing was developed that, in conjunction with an augmented optical drive in Tiger H/E assembly, prevented burned copies of games from booting on an unmodified console. Specifically, all genuine PlayStation discs were printed with a small section of deliberate irregular data, which the PlayStation's optical pick-up was capable of detecting and decoding. Consoles would not boot game discs without a specific wobble frequency contained in the data of the disc pregap sector (the same system was also used to encode discs' regional lockouts). This signal was within Red Book CD tolerances, so PlayStation discs' actual content could still be read by a conventional disc drive; however, the disc drive could not detect the wobble frequency (therefore duplicating the discs omitting it), since the laser pick-up system of any optical disc drive would interpret this wobble as an oscillation of the disc surface and compensate for it in the reading process. Early PlayStations, particularly early 1000 models, experience skipping full-motion video or physical "ticking" noises from the unit. The problems stem from poorly placed vents leading to overheating in some environments, causing the plastic mouldings inside the console to warp slightly and create knock-on effects with the laser assembly. The solution is to sit the console on a surface which dissipates heat efficiently in a well vented area or raise the unit up slightly from its resting surface. Sony representatives also recommended unplugging the PlayStation when it is not in use, as the system draws in a small amount of power (and therefore heat) even when turned off. The first batch of PlayStations use a KSM-440AAM laser unit, whose case and movable parts are all built out of plastic. Over time, the plastic lens sled rail wears out—usually unevenly—due to friction. The placement of the laser unit close to the power supply accelerates wear, due to the additional heat, which makes the plastic more vulnerable to friction. Eventually, one side of the lens sled will become so worn that the laser can tilt, no longer pointing directly at the CD; after this, games will no longer load due to data read errors. Sony fixed the problem by making the sled out of die-cast metal and placing the laser unit further away from the power supply on later PlayStation models. Due to an engineering oversight, the PlayStation does not produce a proper signal on several older models of televisions, causing the display to flicker or bounce around the screen. Sony decided not to change the console design, since only a small percentage of PlayStation owners used such televisions, and instead gave consumers the option of sending their PlayStation unit to a Sony service centre to have an official modchip installed, allowing play on older televisions. Game library The PlayStation featured a diverse game library which grew to appeal to all types of players. Critically acclaimed PlayStation games included Final Fantasy VII (1997), Crash Bandicoot (1996), Spyro the Dragon (1998), Metal Gear Solid (1998), all of which became established franchises. Final Fantasy VII is credited with allowing role-playing games to gain mass-market appeal outside Japan, and is considered one of the most influential and greatest video games ever made. The PlayStation's bestselling game is Gran Turismo (1997), which sold 10.85 million units. After the PlayStation's discontinuation in 2006, the cumulative software shipment was 962 million units. Following its 1994 launch in Japan, early games included Ridge Racer, Crime Crackers, King's Field, Motor Toon Grand Prix, Toh Shin Den (i.e. Battle Arena Toshinden), and Kileak: The Blood. The first two games available at its later North American launch were Jumping Flash! (1995) and Ridge Racer, with Jumping Flash! heralded as an ancestor for 3D graphics in console gaming. Wipeout, Air Combat, Twisted Metal, Warhawk and Destruction Derby were among the popular first-year games, and the first to be reissued as part of Sony's Greatest Hits or Platinum range. At the time of the PlayStation's first Christmas season, Psygnosis had produced around 70% of its launch catalogue; their breakthrough racing game Wipeout was acclaimed for its techno soundtrack and helped raise awareness of Britain's underground music community. Eidos Interactive's action-adventure game Tomb Raider contributed substantially to the success of the console in 1996, with its main protagonist Lara Croft becoming an early gaming icon and garnering unprecedented media promotion. Licensed tie-in video games of popular films were also prevalent; Argonaut Games' 2001 adaptation of Harry Potter and the Philosopher's Stone went on to sell over eight million copies late in the console's lifespan. Third-party developers committed largely to the console's wide-ranging game catalogue even after the launch of the PlayStation 2; some of the notable exclusives in this era include Harry Potter and the Philosopher's Stone, Fear Effect 2: Retro Helix, Syphon Filter 3, C-12: Final Resistance, Dance Dance Revolution Konamix and Digimon World 3.[c] Sony assisted with game reprints as late as 2008 with Metal Gear Solid: The Essential Collection, this being the last PlayStation game officially released and licensed by Sony. Initially, in the United States, PlayStation games were packaged in long cardboard boxes, similar to non-Japanese 3DO and Saturn games. Sony later switched to the jewel case format typically used for audio CDs and Japanese video games, as this format took up less retailer shelf space (which was at a premium due to the large number of PlayStation games being released), and focus testing showed that most consumers preferred this format. Reception The PlayStation was mostly well received upon release. Critics in the west generally welcomed the new console; the staff of Next Generation reviewed the PlayStation a few weeks after its North American launch, where they commented that, while the CPU is "fairly average", the supplementary custom hardware, such as the GPU and sound processor, is stunningly powerful. They praised the PlayStation's focus on 3D, and complemented the comfort of its controller and the convenience of its memory cards. Giving the system 41⁄2 out of 5 stars, they concluded, "To succeed in this extremely cut-throat market, you need a combination of great hardware, great games, and great marketing. Whether by skill, luck, or just deep pockets, Sony has scored three out of three in the first salvo of this war." Albert Kim from Entertainment Weekly praised the PlayStation as a technological marvel, rivalling that of Sega and Nintendo. Famicom Tsūshin scored the console a 19 out of 40, lower than the Saturn's 24 out of 40, in May 1995. In a 1997 year-end review, a team of five Electronic Gaming Monthly editors gave the PlayStation scores of 9.5, 8.5, 9.0, 9.0, and 9.5—for all five editors, the highest score they gave to any of the five consoles reviewed in the issue. They lauded the breadth and quality of the games library, saying it had vastly improved over previous years due to developers mastering the system's capabilities in addition to Sony revising their stance on 2D and role playing games. They also complimented the low price point of the games compared to the Nintendo 64's, and noted that it was the only console on the market that could be relied upon to deliver a solid stream of games for the coming year, primarily due to third party developers almost unanimously favouring it over its competitors. Legacy SCE was an upstart in the video game industry in late 1994, as the video game market in the early 1990s was dominated by Nintendo and Sega. Nintendo had been the clear leader in the industry since the introduction of the Nintendo Entertainment System in 1985 and the Nintendo 64 was initially expected to maintain this position. The PlayStation's target audience included the generation which was the first to grow up with mainstream video games, along with 18- to 29-year-olds who were not the primary focus of Nintendo. By the late 1990s, Sony became a highly regarded console brand due to the PlayStation, with a significant lead over second-place Nintendo, while Sega was relegated to a distant third. The PlayStation became the first "computer entertainment platform" to ship over 100 million units worldwide, with many critics attributing the console's success to third-party developers. It remains the sixth best-selling console of all time as of 2025[update], with a total of 102.49 million units sold. Around 7,900 individual games were published for the console during its 11-year life span, the second-most games ever produced for a console. Its success resulted in a significant financial boon for Sony as profits from their video game division contributed to 23%. Sony's next-generation PlayStation 2, which is backward compatible with the PlayStation's DualShock controller and games, was announced in 1999 and launched in 2000. The PlayStation's lead in installed base and developer support paved the way for the success of its successor, which overcame the earlier launch of the Sega's Dreamcast and then fended off competition from Microsoft's newcomer Xbox and Nintendo's GameCube. The PlayStation 2's immense success and failure of the Dreamcast were among the main factors which led to Sega abandoning the console market. To date, five PlayStation home consoles have been released, which have continued the same numbering scheme, as well as two portable systems. The PlayStation 3 also maintained backward compatibility with original PlayStation discs. Hundreds of PlayStation games have been digitally re-released on the PlayStation Portable, PlayStation 3, PlayStation Vita, PlayStation 4, and PlayStation 5. The PlayStation has often ranked among the best video game consoles. In 2018, Retro Gamer named it the third best console, crediting its sophisticated 3D capabilities as one of its key factors in gaining mass success, and lauding it as a "game-changer in every sense possible". In 2009, IGN ranked the PlayStation the seventh best console in their list, noting its appeal towards older audiences to be a crucial factor in propelling the video game industry, as well as its assistance in transitioning game industry to use the CD-ROM format. Keith Stuart from The Guardian likewise named it as the seventh best console in 2020, declaring that its success was so profound it "ruled the 1990s". In January 2025, Lorentio Brodesco announced the nsOne project, attempting to reverse engineer PlayStation's motherboard. Brodesco stated that "detailed documentation on the original motherboard was either incomplete or entirely unavailable". The project was successfully crowdfunded via Kickstarter. In June, Brodesco manufactured the first working motherboard, promising to bring a fully rooted version with multilayer routing as well as documentation and design files in the near future. The success of the PlayStation contributed to the demise of cartridge-based home consoles. While not the first system to use an optical disc format, it was the first highly successful one, and ended up going head-to-head with the proprietary cartridge-relying Nintendo 64,[d] which the industry had expected to use CDs like PlayStation. After the demise of the Sega Saturn, Nintendo was left as Sony's main competitor in Western markets. Nintendo chose not to use CDs for the Nintendo 64; they were likely concerned with the proprietary cartridge format's ability to help enforce copy protection, given their substantial reliance on licensing and exclusive games for their revenue. Besides their larger capacity, CD-ROMs could be produced in bulk quantities at a much faster rate than ROM cartridges, a week compared to two to three months. Further, the cost of production per unit was far cheaper, allowing Sony to offer games about 40% lower cost to the user compared to ROM cartridges while still making the same amount of net revenue. In Japan, Sony published fewer copies of a wide variety of games for the PlayStation as a risk-limiting step, a model that had been used by Sony Music for CD audio discs. The production flexibility of CD-ROMs meant that Sony could produce larger volumes of popular games to get onto the market quickly, something that could not be done with cartridges due to their manufacturing lead time. The lower production costs of CD-ROMs also allowed publishers an additional source of profit: budget-priced reissues of games which had already recouped their development costs. Tokunaka remarked in 1996: Choosing CD-ROM is one of the most important decisions that we made. As I'm sure you understand, PlayStation could just as easily have worked with masked ROM [cartridges]. The 3D engine and everything—the whole PlayStation format—is independent of the media. But for various reasons (including the economies for the consumer, the ease of the manufacturing, inventory control for the trade, and also the software publishers) we deduced that CD-ROM would be the best media for PlayStation. The increasing complexity of developing games pushed cartridges to their storage limits and gradually discouraged some third-party developers. Part of the CD format's appeal to publishers was that they could be produced at a significantly lower cost and offered more production flexibility to meet demand. As a result, some third-party developers switched to the PlayStation, including Square and Enix, whose Final Fantasy VII and Dragon Quest VII respectively had been planned for the Nintendo 64 (both companies later merged to form Square Enix). Other developers released fewer games for the Nintendo 64 (Konami, releasing only thirteen N64 games but over fifty on the PlayStation). Nintendo 64 game releases were less frequent than the PlayStation's, with many being developed by either Nintendo themselves or second-parties such as Rare. The PlayStation Classic is a dedicated video game console made by Sony Interactive Entertainment that emulates PlayStation games. It was announced in September 2018 at the Tokyo Game Show, and released on 3 December 2018, the 24th anniversary of the release of the original console. As a dedicated console, the PlayStation Classic features 20 pre-installed games; the games run off the open source emulator PCSX. The console is bundled with two replica wired PlayStation controllers (those without analogue sticks), an HDMI cable, and a USB-Type A cable. Internally, the console uses a MediaTek MT8167a Quad A35 system on a chip with four central processing cores clocked at @ 1.5 GHz and a Power VR GE8300 graphics processing unit. It includes 16 GB of eMMC flash storage and 1 Gigabyte of DDR3 SDRAM. The PlayStation Classic is 45% smaller than the original console. The PlayStation Classic received negative reviews from critics and was compared unfavorably to Nintendo's rival Nintendo Entertainment System Classic Edition and Super Nintendo Entertainment System Classic Edition. Criticism was directed at its meagre game library, user interface, emulation quality, use of PAL versions for certain games, use of the original controller, and high retail price, though the console's design received praise. The console sold poorly. See also Notes References |
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Contents Lod Lod (Hebrew: לוד, fully vocalized: לֹד), also known as Lydda (Ancient Greek: Λύδδα) and Lidd (Arabic: اللِّدّ, romanized: al-Lidd, or اللُّدّ, al-Ludd), is a city 15 km (9+1⁄2 mi) southeast of Tel Aviv and 40 km (25 mi) northwest of Jerusalem in the Central District of Israel. It is situated between the lower Shephelah on the east and the coastal plain on the west. The city had a population of 90,814 in 2023. Lod has been inhabited since at least the Neolithic period. It is mentioned a few times in the Hebrew Bible and in the New Testament. Between the 5th century BCE and up until the late Roman period, it was a prominent center for Jewish scholarship and trade. Around 200 CE, the city became a Roman colony and was renamed Diospolis (Ancient Greek: Διόσπολις, lit. 'city of Zeus'). Tradition identifies Lod as the 4th century martyrdom site of Saint George; the Church of Saint George and Mosque of Al-Khadr located in the city is believed to have housed his remains. Following the Arab conquest of the Levant, Lod served as the capital of Jund Filastin; however, a few decades later, the seat of power was transferred to Ramla, and Lod slipped in importance. Under Crusader rule, the city was a Catholic diocese of the Latin Church and it remains a titular see to this day.[citation needed] Lod underwent a major change in its population in the mid-20th century. Exclusively Palestinian Arab in 1947, Lod was part of the area designated for an Arab state in the United Nations Partition Plan for Palestine; however, in July 1948, the city was occupied by the Israel Defense Forces, and most of its Arab inhabitants were expelled in the Palestinian expulsion from Lydda and Ramle. The city was largely resettled by Jewish immigrants, most of them expelled from Arab countries. Today, Lod is one of Israel's mixed cities, with an Arab population of 30%. Lod is one of Israel's major transportation hubs. The main international airport, Ben Gurion Airport, is located 8 km (5 miles) north of the city. The city is also a major railway and road junction. Religious references The Hebrew name Lod appears in the Hebrew Bible as a town of Benjamin, founded along with Ono by Shamed or Shamer (1 Chronicles 8:12; Ezra 2:33; Nehemiah 7:37; 11:35). In Ezra 2:33, it is mentioned as one of the cities whose inhabitants returned after the Babylonian captivity. Lod is not mentioned among the towns allocated to the tribe of Benjamin in Joshua 18:11–28. The name Lod derives from a tri-consonantal root not extant in Northwest Semitic, but only in Arabic (“to quarrel; withhold, hinder”). An Arabic etymology of such an ancient name is unlikely (the earliest attestation is from the Achaemenid period). In the New Testament, the town appears in its Greek form, Lydda, as the site of Peter's healing of Aeneas in Acts 9:32–38. The city is also mentioned in an Islamic hadith as the location of the battlefield where the false messiah (al-Masih ad-Dajjal) will be slain before the Day of Judgment. History The first occupation dates to the Neolithic in the Near East and is associated with the Lodian culture. Occupation continued in the Levant Chalcolithic. Pottery finds have dated the initial settlement in the area now occupied by the town to 5600–5250 BCE. In the Early Bronze, it was an important settlement in the central coastal plain between the Judean Shephelah and the Mediterranean coast, along Nahal Ayalon. Other important nearby sites were Tel Dalit, Tel Bareqet, Khirbat Abu Hamid (Shoham North), Tel Afeq, Azor and Jaffa. Two architectural phases belong to the late EB I in Area B. The first phase had a mudbrick wall, while the late phase included a circulat stone structure. Later excavations have produced an occupation later, Stratum IV. It consists of two phases, Stratum IVb with mudbrick wall on stone foundations and rounded exterior corners. In Stratum IVa there was a mudbrick wall with no stone foundations, with imported Egyptian potter and local pottery imitations. Another excavations revealed nine occupation strata. Strata VI-III belonged to Early Bronze IB. The material culture showed Egyptian imports in strata V and IV. Occupation continued into Early Bronze II with four strata (V-II). There was continuity in the material culture and indications of centralized urban planning. North to the tell were scattered MB II burials. The earliest written record is in a list of Canaanite towns drawn up by the Egyptian pharaoh Thutmose III at Karnak in 1465 BCE. From the fifth century BCE until the Roman period, the city was a centre of Jewish scholarship and commerce. According to British historian Martin Gilbert, during the Hasmonean period, Jonathan Maccabee and his brother, Simon Maccabaeus, enlarged the area under Jewish control, which included conquering the city. The Jewish community in Lod during the Mishnah and Talmud era is described in a significant number of sources, including information on its institutions, demographics, and way of life. The city reached its height as a Jewish center between the First Jewish-Roman War and the Bar Kokhba revolt, and again in the days of Judah ha-Nasi and the start of the Amoraim period. The city was then the site of numerous public institutions, including schools, study houses, and synagogues. In 43 BC, Cassius, the Roman governor of Syria, sold the inhabitants of Lod into slavery, but they were set free two years later by Mark Antony. During the First Jewish–Roman War, the Roman proconsul of Syria, Cestius Gallus, razed the town on his way to Jerusalem in Tishrei 66 CE. According to Josephus, "[he] found the city deserted, for the entire population had gone up to Jerusalem for the Feast of Tabernacles. He killed fifty people whom he found, burned the town and marched on". Lydda was occupied by Emperor Vespasian in 68 CE. In the period following the destruction of Jerusalem in 70 CE, Rabbi Tarfon, who appears in many Tannaitic and Jewish legal discussions, served as a rabbinic authority in Lod. During the Kitos War, 115–117 CE, the Roman army laid siege to Lod, where the rebel Jews had gathered under the leadership of Julian and Pappos. Torah study was outlawed by the Romans and pursued mostly in the underground. The distress became so great, the patriarch Rabban Gamaliel II, who was shut up there and died soon afterwards, permitted fasting on Ḥanukkah. Other rabbis disagreed with this ruling. Lydda was next taken and many of the Jews were executed; the "slain of Lydda" are often mentioned in words of reverential praise in the Talmud. In 200 CE, emperor Septimius Severus elevated the town to the status of a city, calling it Colonia Lucia Septimia Severa Diospolis. The name Diospolis ("City of Zeus") may have been bestowed earlier, possibly by Hadrian. At that point, most of its inhabitants were Christian. The earliest known bishop is Aëtius, a friend of Arius. During the following century (200-300CE), it's said that Joshua ben Levi founded a yeshiva in Lod. In December 415, the Council of Diospolis was held here to try Pelagius; he was acquitted. In the sixth century, the city was renamed Georgiopolis after St. George, a soldier in the guard of the emperor Diocletian, who was born there between 256 and 285 CE. The Church of Saint George and Mosque of Al-Khadr is named for him. The 6th-century Madaba map shows Lydda as an unwalled city with a cluster of buildings under a black inscription reading "Lod, also Lydea, also Diospolis". An isolated large building with a semicircular colonnaded plaza in front of it might represent the St George shrine. After the Muslim conquest of Palestine by Amr ibn al-'As in 636 CE, Lod which was referred to as "al-Ludd" in Arabic served as the capital of Jund Filastin ("Military District of Palaestina") before the seat of power was moved to nearby Ramla during the reign of the Umayyad Caliph Suleiman ibn Abd al-Malik in 715–716. The population of al-Ludd was relocated to Ramla, as well. With the relocation of its inhabitants and the construction of the White Mosque in Ramla, al-Ludd lost its importance and fell into decay. The city was visited by the local Arab geographer al-Muqaddasi in 985, when it was under the Fatimid Caliphate, and was noted for its Great Mosque which served the residents of al-Ludd, Ramla, and the nearby villages. He also wrote of the city's "wonderful church (of St. George) at the gate of which Christ will slay the Antichrist." The Crusaders occupied the city in 1099 and named it St Jorge de Lidde. It was briefly conquered by Saladin, but retaken by the Crusaders in 1191. For the English Crusaders, it was a place of great significance as the birthplace of Saint George. The Crusaders made it the seat of a Latin Church diocese, and it remains a titular see. It owed the service of 10 knights and 20 sergeants, and it had its own burgess court during this era. In 1226, Ayyubid Syrian geographer Yaqut al-Hamawi visited al-Ludd and stated it was part of the Jerusalem District during Ayyubid rule. Sultan Baybars brought Lydda again under Muslim control by 1267–8. According to Qalqashandi, Lydda was an administrative centre of a wilaya during the fourteenth and fifteenth century in the Mamluk empire. Mujir al-Din described it as a pleasant village with an active Friday mosque. During this time, Lydda was a station on the postal route between Cairo and Damascus. In 1517, Lydda was incorporated into the Ottoman Empire as part of the Damascus Eyalet, and in the 1550s, the revenues of Lydda were designated for the new waqf of Hasseki Sultan Imaret in Jerusalem, established by Hasseki Hurrem Sultan (Roxelana), the wife of Suleiman the Magnificent. By 1596 Lydda was a part of the nahiya ("subdistrict") of Ramla, which was under the administration of the liwa ("district") of Gaza. It had a population of 241 households and 14 bachelors who were all Muslims, and 233 households who were Christians. They paid a fixed tax-rate of 33,3 % on agricultural products, including wheat, barley, summer crops, vineyards, fruit trees, sesame, special product ("dawalib" =spinning wheels), goats and beehives, in addition to occasional revenues and market toll, a total of 45,000 Akçe. All of the revenue went to the Waqf. In 1051 AH/1641/2, the Bedouin tribe of al-Sawālima from around Jaffa attacked the villages of Subṭāra, Bayt Dajan, al-Sāfiriya, Jindās, Lydda and Yāzūr belonging to Waqf Haseki Sultan. The village appeared as Lydda, though misplaced, on the map of Pierre Jacotin compiled in 1799. Missionary William M. Thomson visited Lydda in the mid-19th century, describing it as a "flourishing village of some 2,000 inhabitants, imbosomed in noble orchards of olive, fig, pomegranate, mulberry, sycamore, and other trees, surrounded every way by a very fertile neighbourhood. The inhabitants are evidently industrious and thriving, and the whole country between this and Ramleh is fast being filled up with their flourishing orchards. Rarely have I beheld a rural scene more delightful than this presented in early harvest ... It must be seen, heard, and enjoyed to be appreciated." In 1869, the population of Ludd was given as: 55 Catholics, 1,940 "Greeks", 5 Protestants and 4,850 Muslims. In 1870, the Church of Saint George was rebuilt. In 1892, the first railway station in the entire region was established in the city. In the second half of the 19th century, Jewish merchants migrated to the city, but left after the 1921 Jaffa riots. In 1882, the Palestine Exploration Fund's Survey of Western Palestine described Lod as "A small town, standing among enclosure of prickly pear, and having fine olive groves around it, especially to the south. The minaret of the mosque is a very conspicuous object over the whole of the plain. The inhabitants are principally Moslim, though the place is the seat of a Greek bishop resident of Jerusalem. The Crusading church has lately been restored, and is used by the Greeks. Wells are found in the gardens...." From 1918, Lydda was under the administration of the British Mandate in Palestine, as per a League of Nations decree that followed the Great War. During the Second World War, the British set up supply posts in and around Lydda and its railway station, also building an airport that was renamed Ben Gurion Airport after the death of Israel's first prime minister in 1973. At the time of the 1922 census of Palestine, Lydda had a population of 8,103 inhabitants (7,166 Muslims, 926 Christians, and 11 Jews), the Christians were 921 Orthodox, 4 Roman Catholics and 1 Melkite. This had increased by the 1931 census to 11,250 (10,002 Muslims, 1,210 Christians, 28 Jews, and 10 Bahai), in a total of 2475 residential houses. In 1938, Lydda had a population of 12,750. In 1945, Lydda had a population of 16,780 (14,910 Muslims, 1,840 Christians, 20 Jews and 10 "other"). Until 1948, Lydda was an Arab town with a population of around 20,000—18,500 Muslims and 1,500 Christians. In 1947, the United Nations proposed dividing Mandatory Palestine into two states, one Jewish state and one Arab; Lydda was to form part of the proposed Arab state. In the ensuing war, Israel captured Arab towns outside the area the UN had allotted it, including Lydda. In December 1947, thirteen Jewish passengers in a seven-car convoy to Ben Shemen Youth Village were ambushed and murdered.In a separate incident, three Jewish youths, two men and a woman were captured, then raped and murdered in a neighbouring village. Their bodies were paraded in Lydda’s principal street. The Israel Defense Forces entered Lydda on 11 July 1948. The following day, under the impression that it was under attack, the 3rd Battalion was ordered to shoot anyone "seen on the streets". According to Israel, 250 Arabs were killed. Other estimates are higher: Arab historian Aref al Aref estimated 400, and Nimr al Khatib 1,700. In 1948, the population rose to 50,000 during the Nakba, as Arab refugees fleeing other areas made their way there. A key event was the Palestinian expulsion from Lydda and Ramle, with the expulsion of 50,000-70,000 Palestinians from Lydda and Ramle by the Israel Defense Forces. All but 700 to 1,056 were expelled by order of the Israeli high command, and forced to walk 17 km (10+1⁄2 mi) to the Jordanian Arab Legion lines. Estimates of those who died from exhaustion and dehydration vary from a handful to 355. The town was subsequently sacked by the Israeli army. Some scholars, including Ilan Pappé, characterize this as ethnic cleansing. The few hundred Arabs who remained in the city were soon outnumbered by the influx of Jews who immigrated to Lod from August 1948 onward, most of them from Arab countries. As a result, Lod became a predominantly Jewish town. After the establishment of the state, the biblical name Lod was readopted. The Jewish immigrants who settled Lod came in waves, first from Morocco and Tunisia, later from Ethiopia, and then from the former Soviet Union. Since 2008, many urban development projects have been undertaken to improve the image of the city. Upscale neighbourhoods have been built, among them Ganei Ya'ar and Ahisemah, expanding the city to the east. According to a 2010 report in the Economist, a three-meter-high wall was built between Jewish and Arab neighbourhoods and construction in Jewish areas was given priority over construction in Arab neighborhoods. The newspaper says that violent crime in the Arab sector revolves mainly around family feuds over turf and honour crimes. In 2010, the Lod Community Foundation organised an event for representatives of bicultural youth movements, volunteer aid organisations, educational start-ups, businessmen, sports organizations, and conservationists working on programmes to better the city. In the 2021 Israel–Palestine crisis, a state of emergency was declared in Lod after Arab rioting led to the death of an Israeli Jew. The Mayor of Lod, Yair Revivio, urged Prime Minister of Israel Benjamin Netanyahu to deploy Israel Border Police to restore order in the city. This was the first time since 1966 that Israel had declared this kind of emergency lockdown. International media noted that both Jewish and Palestinian mobs were active in Lod, but the "crackdown came for one side" only. Demographics In the 19th century and until the Lydda Death March, Lod was an exclusively Muslim-Christian town, with an estimated 6,850 inhabitants, of whom approximately 2,000 (29%) were Christian. According to the Israel Central Bureau of Statistics (CBS), the population of Lod in 2010 was 69,500 people. According to the 2019 census, the population of Lod was 77,223, of which 53,581 people, comprising 69.4% of the city's population, were classified as "Jews and Others", and 23,642 people, comprising 30.6% as "Arab". Education According to CBS, 38 schools and 13,188 pupils are in the city. They are spread out as 26 elementary schools and 8,325 elementary school pupils, and 13 high schools and 4,863 high school pupils. About 52.5% of 12th-grade pupils were entitled to a matriculation certificate in 2001.[citation needed] Economy The airport and related industries are a major source of employment for the residents of Lod. Other important factories in the city are the communication equipment company "Talard", "Cafe-Co" - a subsidiary of the Strauss Group and "Kashev" - the computer center of Bank Leumi. A Jewish Agency Absorption Centre is also located in Lod. According to CBS figures for 2000, 23,032 people were salaried workers and 1,405 were self-employed. The mean monthly wage for a salaried worker was NIS 4,754, a real change of 2.9% over the course of 2000. Salaried men had a mean monthly wage of NIS 5,821 (a real change of 1.4%) versus NIS 3,547 for women (a real change of 4.6%). The mean income for the self-employed was NIS 4,991. About 1,275 people were receiving unemployment benefits and 7,145 were receiving an income supplement. Art and culture In 2009-2010, Dor Guez held an exhibit, Georgeopolis, at the Petach Tikva art museum that focuses on Lod. Archaeology A well-preserved mosaic floor dating to the Roman period was excavated in 1996 as part of a salvage dig conducted on behalf of the Israel Antiquities Authority and the Municipality of Lod, prior to widening HeHalutz Street. According to Jacob Fisch, executive director of the Friends of the Israel Antiquities Authority, a worker at the construction site noticed the tail of a tiger and halted work. The mosaic was initially covered over with soil at the conclusion of the excavation for lack of funds to conserve and develop the site. The mosaic is now part of the Lod Mosaic Archaeological Center. The floor, with its colorful display of birds, fish, exotic animals and merchant ships, is believed to have been commissioned by a wealthy resident of the city for his private home. The Lod Community Archaeology Program, which operates in ten Lod schools, five Jewish and five Israeli Arab, combines archaeological studies with participation in digs in Lod. Sports The city's major football club, Hapoel Bnei Lod, plays in Liga Leumit (the second division). Its home is at the Lod Municipal Stadium. The club was formed by a merger of Bnei Lod and Rakevet Lod in the 1980s. Two other clubs in the city play in the regional leagues: Hapoel MS Ortodoxim Lod in Liga Bet and Maccabi Lod in Liga Gimel. Hapoel Lod played in the top division during the 1960s and 1980s, and won the State Cup in 1984. The club folded in 2002. A new club, Hapoel Maxim Lod (named after former mayor Maxim Levy) was established soon after, but folded in 2007. Notable people Twin towns-sister cities Lod is twinned with: See also References Bibliography External links |
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Contents Lod Lod (Hebrew: לוד, fully vocalized: לֹד), also known as Lydda (Ancient Greek: Λύδδα) and Lidd (Arabic: اللِّدّ, romanized: al-Lidd, or اللُّدّ, al-Ludd), is a city 15 km (9+1⁄2 mi) southeast of Tel Aviv and 40 km (25 mi) northwest of Jerusalem in the Central District of Israel. It is situated between the lower Shephelah on the east and the coastal plain on the west. The city had a population of 90,814 in 2023. Lod has been inhabited since at least the Neolithic period. It is mentioned a few times in the Hebrew Bible and in the New Testament. Between the 5th century BCE and up until the late Roman period, it was a prominent center for Jewish scholarship and trade. Around 200 CE, the city became a Roman colony and was renamed Diospolis (Ancient Greek: Διόσπολις, lit. 'city of Zeus'). Tradition identifies Lod as the 4th century martyrdom site of Saint George; the Church of Saint George and Mosque of Al-Khadr located in the city is believed to have housed his remains. Following the Arab conquest of the Levant, Lod served as the capital of Jund Filastin; however, a few decades later, the seat of power was transferred to Ramla, and Lod slipped in importance. Under Crusader rule, the city was a Catholic diocese of the Latin Church and it remains a titular see to this day.[citation needed] Lod underwent a major change in its population in the mid-20th century. Exclusively Palestinian Arab in 1947, Lod was part of the area designated for an Arab state in the United Nations Partition Plan for Palestine; however, in July 1948, the city was occupied by the Israel Defense Forces, and most of its Arab inhabitants were expelled in the Palestinian expulsion from Lydda and Ramle. The city was largely resettled by Jewish immigrants, most of them expelled from Arab countries. Today, Lod is one of Israel's mixed cities, with an Arab population of 30%. Lod is one of Israel's major transportation hubs. The main international airport, Ben Gurion Airport, is located 8 km (5 miles) north of the city. The city is also a major railway and road junction. Religious references The Hebrew name Lod appears in the Hebrew Bible as a town of Benjamin, founded along with Ono by Shamed or Shamer (1 Chronicles 8:12; Ezra 2:33; Nehemiah 7:37; 11:35). In Ezra 2:33, it is mentioned as one of the cities whose inhabitants returned after the Babylonian captivity. Lod is not mentioned among the towns allocated to the tribe of Benjamin in Joshua 18:11–28. The name Lod derives from a tri-consonantal root not extant in Northwest Semitic, but only in Arabic (“to quarrel; withhold, hinder”). An Arabic etymology of such an ancient name is unlikely (the earliest attestation is from the Achaemenid period). In the New Testament, the town appears in its Greek form, Lydda, as the site of Peter's healing of Aeneas in Acts 9:32–38. The city is also mentioned in an Islamic hadith as the location of the battlefield where the false messiah (al-Masih ad-Dajjal) will be slain before the Day of Judgment. History The first occupation dates to the Neolithic in the Near East and is associated with the Lodian culture. Occupation continued in the Levant Chalcolithic. Pottery finds have dated the initial settlement in the area now occupied by the town to 5600–5250 BCE. In the Early Bronze, it was an important settlement in the central coastal plain between the Judean Shephelah and the Mediterranean coast, along Nahal Ayalon. Other important nearby sites were Tel Dalit, Tel Bareqet, Khirbat Abu Hamid (Shoham North), Tel Afeq, Azor and Jaffa. Two architectural phases belong to the late EB I in Area B. The first phase had a mudbrick wall, while the late phase included a circulat stone structure. Later excavations have produced an occupation later, Stratum IV. It consists of two phases, Stratum IVb with mudbrick wall on stone foundations and rounded exterior corners. In Stratum IVa there was a mudbrick wall with no stone foundations, with imported Egyptian potter and local pottery imitations. Another excavations revealed nine occupation strata. Strata VI-III belonged to Early Bronze IB. The material culture showed Egyptian imports in strata V and IV. Occupation continued into Early Bronze II with four strata (V-II). There was continuity in the material culture and indications of centralized urban planning. North to the tell were scattered MB II burials. The earliest written record is in a list of Canaanite towns drawn up by the Egyptian pharaoh Thutmose III at Karnak in 1465 BCE. From the fifth century BCE until the Roman period, the city was a centre of Jewish scholarship and commerce. According to British historian Martin Gilbert, during the Hasmonean period, Jonathan Maccabee and his brother, Simon Maccabaeus, enlarged the area under Jewish control, which included conquering the city. The Jewish community in Lod during the Mishnah and Talmud era is described in a significant number of sources, including information on its institutions, demographics, and way of life. The city reached its height as a Jewish center between the First Jewish-Roman War and the Bar Kokhba revolt, and again in the days of Judah ha-Nasi and the start of the Amoraim period. The city was then the site of numerous public institutions, including schools, study houses, and synagogues. In 43 BC, Cassius, the Roman governor of Syria, sold the inhabitants of Lod into slavery, but they were set free two years later by Mark Antony. During the First Jewish–Roman War, the Roman proconsul of Syria, Cestius Gallus, razed the town on his way to Jerusalem in Tishrei 66 CE. According to Josephus, "[he] found the city deserted, for the entire population had gone up to Jerusalem for the Feast of Tabernacles. He killed fifty people whom he found, burned the town and marched on". Lydda was occupied by Emperor Vespasian in 68 CE. In the period following the destruction of Jerusalem in 70 CE, Rabbi Tarfon, who appears in many Tannaitic and Jewish legal discussions, served as a rabbinic authority in Lod. During the Kitos War, 115–117 CE, the Roman army laid siege to Lod, where the rebel Jews had gathered under the leadership of Julian and Pappos. Torah study was outlawed by the Romans and pursued mostly in the underground. The distress became so great, the patriarch Rabban Gamaliel II, who was shut up there and died soon afterwards, permitted fasting on Ḥanukkah. Other rabbis disagreed with this ruling. Lydda was next taken and many of the Jews were executed; the "slain of Lydda" are often mentioned in words of reverential praise in the Talmud. In 200 CE, emperor Septimius Severus elevated the town to the status of a city, calling it Colonia Lucia Septimia Severa Diospolis. The name Diospolis ("City of Zeus") may have been bestowed earlier, possibly by Hadrian. At that point, most of its inhabitants were Christian. The earliest known bishop is Aëtius, a friend of Arius. During the following century (200-300CE), it's said that Joshua ben Levi founded a yeshiva in Lod. In December 415, the Council of Diospolis was held here to try Pelagius; he was acquitted. In the sixth century, the city was renamed Georgiopolis after St. George, a soldier in the guard of the emperor Diocletian, who was born there between 256 and 285 CE. The Church of Saint George and Mosque of Al-Khadr is named for him. The 6th-century Madaba map shows Lydda as an unwalled city with a cluster of buildings under a black inscription reading "Lod, also Lydea, also Diospolis". An isolated large building with a semicircular colonnaded plaza in front of it might represent the St George shrine. After the Muslim conquest of Palestine by Amr ibn al-'As in 636 CE, Lod which was referred to as "al-Ludd" in Arabic served as the capital of Jund Filastin ("Military District of Palaestina") before the seat of power was moved to nearby Ramla during the reign of the Umayyad Caliph Suleiman ibn Abd al-Malik in 715–716. The population of al-Ludd was relocated to Ramla, as well. With the relocation of its inhabitants and the construction of the White Mosque in Ramla, al-Ludd lost its importance and fell into decay. The city was visited by the local Arab geographer al-Muqaddasi in 985, when it was under the Fatimid Caliphate, and was noted for its Great Mosque which served the residents of al-Ludd, Ramla, and the nearby villages. He also wrote of the city's "wonderful church (of St. George) at the gate of which Christ will slay the Antichrist." The Crusaders occupied the city in 1099 and named it St Jorge de Lidde. It was briefly conquered by Saladin, but retaken by the Crusaders in 1191. For the English Crusaders, it was a place of great significance as the birthplace of Saint George. The Crusaders made it the seat of a Latin Church diocese, and it remains a titular see. It owed the service of 10 knights and 20 sergeants, and it had its own burgess court during this era. In 1226, Ayyubid Syrian geographer Yaqut al-Hamawi visited al-Ludd and stated it was part of the Jerusalem District during Ayyubid rule. Sultan Baybars brought Lydda again under Muslim control by 1267–8. According to Qalqashandi, Lydda was an administrative centre of a wilaya during the fourteenth and fifteenth century in the Mamluk empire. Mujir al-Din described it as a pleasant village with an active Friday mosque. During this time, Lydda was a station on the postal route between Cairo and Damascus. In 1517, Lydda was incorporated into the Ottoman Empire as part of the Damascus Eyalet, and in the 1550s, the revenues of Lydda were designated for the new waqf of Hasseki Sultan Imaret in Jerusalem, established by Hasseki Hurrem Sultan (Roxelana), the wife of Suleiman the Magnificent. By 1596 Lydda was a part of the nahiya ("subdistrict") of Ramla, which was under the administration of the liwa ("district") of Gaza. It had a population of 241 households and 14 bachelors who were all Muslims, and 233 households who were Christians. They paid a fixed tax-rate of 33,3 % on agricultural products, including wheat, barley, summer crops, vineyards, fruit trees, sesame, special product ("dawalib" =spinning wheels), goats and beehives, in addition to occasional revenues and market toll, a total of 45,000 Akçe. All of the revenue went to the Waqf. In 1051 AH/1641/2, the Bedouin tribe of al-Sawālima from around Jaffa attacked the villages of Subṭāra, Bayt Dajan, al-Sāfiriya, Jindās, Lydda and Yāzūr belonging to Waqf Haseki Sultan. The village appeared as Lydda, though misplaced, on the map of Pierre Jacotin compiled in 1799. Missionary William M. Thomson visited Lydda in the mid-19th century, describing it as a "flourishing village of some 2,000 inhabitants, imbosomed in noble orchards of olive, fig, pomegranate, mulberry, sycamore, and other trees, surrounded every way by a very fertile neighbourhood. The inhabitants are evidently industrious and thriving, and the whole country between this and Ramleh is fast being filled up with their flourishing orchards. Rarely have I beheld a rural scene more delightful than this presented in early harvest ... It must be seen, heard, and enjoyed to be appreciated." In 1869, the population of Ludd was given as: 55 Catholics, 1,940 "Greeks", 5 Protestants and 4,850 Muslims. In 1870, the Church of Saint George was rebuilt. In 1892, the first railway station in the entire region was established in the city. In the second half of the 19th century, Jewish merchants migrated to the city, but left after the 1921 Jaffa riots. In 1882, the Palestine Exploration Fund's Survey of Western Palestine described Lod as "A small town, standing among enclosure of prickly pear, and having fine olive groves around it, especially to the south. The minaret of the mosque is a very conspicuous object over the whole of the plain. The inhabitants are principally Moslim, though the place is the seat of a Greek bishop resident of Jerusalem. The Crusading church has lately been restored, and is used by the Greeks. Wells are found in the gardens...." From 1918, Lydda was under the administration of the British Mandate in Palestine, as per a League of Nations decree that followed the Great War. During the Second World War, the British set up supply posts in and around Lydda and its railway station, also building an airport that was renamed Ben Gurion Airport after the death of Israel's first prime minister in 1973. At the time of the 1922 census of Palestine, Lydda had a population of 8,103 inhabitants (7,166 Muslims, 926 Christians, and 11 Jews), the Christians were 921 Orthodox, 4 Roman Catholics and 1 Melkite. This had increased by the 1931 census to 11,250 (10,002 Muslims, 1,210 Christians, 28 Jews, and 10 Bahai), in a total of 2475 residential houses. In 1938, Lydda had a population of 12,750. In 1945, Lydda had a population of 16,780 (14,910 Muslims, 1,840 Christians, 20 Jews and 10 "other"). Until 1948, Lydda was an Arab town with a population of around 20,000—18,500 Muslims and 1,500 Christians. In 1947, the United Nations proposed dividing Mandatory Palestine into two states, one Jewish state and one Arab; Lydda was to form part of the proposed Arab state. In the ensuing war, Israel captured Arab towns outside the area the UN had allotted it, including Lydda. In December 1947, thirteen Jewish passengers in a seven-car convoy to Ben Shemen Youth Village were ambushed and murdered.In a separate incident, three Jewish youths, two men and a woman were captured, then raped and murdered in a neighbouring village. Their bodies were paraded in Lydda’s principal street. The Israel Defense Forces entered Lydda on 11 July 1948. The following day, under the impression that it was under attack, the 3rd Battalion was ordered to shoot anyone "seen on the streets". According to Israel, 250 Arabs were killed. Other estimates are higher: Arab historian Aref al Aref estimated 400, and Nimr al Khatib 1,700. In 1948, the population rose to 50,000 during the Nakba, as Arab refugees fleeing other areas made their way there. A key event was the Palestinian expulsion from Lydda and Ramle, with the expulsion of 50,000-70,000 Palestinians from Lydda and Ramle by the Israel Defense Forces. All but 700 to 1,056 were expelled by order of the Israeli high command, and forced to walk 17 km (10+1⁄2 mi) to the Jordanian Arab Legion lines. Estimates of those who died from exhaustion and dehydration vary from a handful to 355. The town was subsequently sacked by the Israeli army. Some scholars, including Ilan Pappé, characterize this as ethnic cleansing. The few hundred Arabs who remained in the city were soon outnumbered by the influx of Jews who immigrated to Lod from August 1948 onward, most of them from Arab countries. As a result, Lod became a predominantly Jewish town. After the establishment of the state, the biblical name Lod was readopted. The Jewish immigrants who settled Lod came in waves, first from Morocco and Tunisia, later from Ethiopia, and then from the former Soviet Union. Since 2008, many urban development projects have been undertaken to improve the image of the city. Upscale neighbourhoods have been built, among them Ganei Ya'ar and Ahisemah, expanding the city to the east. According to a 2010 report in the Economist, a three-meter-high wall was built between Jewish and Arab neighbourhoods and construction in Jewish areas was given priority over construction in Arab neighborhoods. The newspaper says that violent crime in the Arab sector revolves mainly around family feuds over turf and honour crimes. In 2010, the Lod Community Foundation organised an event for representatives of bicultural youth movements, volunteer aid organisations, educational start-ups, businessmen, sports organizations, and conservationists working on programmes to better the city. In the 2021 Israel–Palestine crisis, a state of emergency was declared in Lod after Arab rioting led to the death of an Israeli Jew. The Mayor of Lod, Yair Revivio, urged Prime Minister of Israel Benjamin Netanyahu to deploy Israel Border Police to restore order in the city. This was the first time since 1966 that Israel had declared this kind of emergency lockdown. International media noted that both Jewish and Palestinian mobs were active in Lod, but the "crackdown came for one side" only. Demographics In the 19th century and until the Lydda Death March, Lod was an exclusively Muslim-Christian town, with an estimated 6,850 inhabitants, of whom approximately 2,000 (29%) were Christian. According to the Israel Central Bureau of Statistics (CBS), the population of Lod in 2010 was 69,500 people. According to the 2019 census, the population of Lod was 77,223, of which 53,581 people, comprising 69.4% of the city's population, were classified as "Jews and Others", and 23,642 people, comprising 30.6% as "Arab". Education According to CBS, 38 schools and 13,188 pupils are in the city. They are spread out as 26 elementary schools and 8,325 elementary school pupils, and 13 high schools and 4,863 high school pupils. About 52.5% of 12th-grade pupils were entitled to a matriculation certificate in 2001.[citation needed] Economy The airport and related industries are a major source of employment for the residents of Lod. Other important factories in the city are the communication equipment company "Talard", "Cafe-Co" - a subsidiary of the Strauss Group and "Kashev" - the computer center of Bank Leumi. A Jewish Agency Absorption Centre is also located in Lod. According to CBS figures for 2000, 23,032 people were salaried workers and 1,405 were self-employed. The mean monthly wage for a salaried worker was NIS 4,754, a real change of 2.9% over the course of 2000. Salaried men had a mean monthly wage of NIS 5,821 (a real change of 1.4%) versus NIS 3,547 for women (a real change of 4.6%). The mean income for the self-employed was NIS 4,991. About 1,275 people were receiving unemployment benefits and 7,145 were receiving an income supplement. Art and culture In 2009-2010, Dor Guez held an exhibit, Georgeopolis, at the Petach Tikva art museum that focuses on Lod. Archaeology A well-preserved mosaic floor dating to the Roman period was excavated in 1996 as part of a salvage dig conducted on behalf of the Israel Antiquities Authority and the Municipality of Lod, prior to widening HeHalutz Street. According to Jacob Fisch, executive director of the Friends of the Israel Antiquities Authority, a worker at the construction site noticed the tail of a tiger and halted work. The mosaic was initially covered over with soil at the conclusion of the excavation for lack of funds to conserve and develop the site. The mosaic is now part of the Lod Mosaic Archaeological Center. The floor, with its colorful display of birds, fish, exotic animals and merchant ships, is believed to have been commissioned by a wealthy resident of the city for his private home. The Lod Community Archaeology Program, which operates in ten Lod schools, five Jewish and five Israeli Arab, combines archaeological studies with participation in digs in Lod. Sports The city's major football club, Hapoel Bnei Lod, plays in Liga Leumit (the second division). Its home is at the Lod Municipal Stadium. The club was formed by a merger of Bnei Lod and Rakevet Lod in the 1980s. Two other clubs in the city play in the regional leagues: Hapoel MS Ortodoxim Lod in Liga Bet and Maccabi Lod in Liga Gimel. Hapoel Lod played in the top division during the 1960s and 1980s, and won the State Cup in 1984. The club folded in 2002. A new club, Hapoel Maxim Lod (named after former mayor Maxim Levy) was established soon after, but folded in 2007. Notable people Twin towns-sister cities Lod is twinned with: See also References Bibliography External links |
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[SOURCE: https://en.wikipedia.org/wiki/Ionosphere] | [TOKENS: 6001] |
Contents Ionosphere The ionosphere (/aɪˈɒnəˌsfɪər/) is the ionized part of the upper atmosphere of Earth, from about 48 km (30 mi) to 965 km (600 mi) above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. Travel through this layer also impacts GPS signals, resulting in effects such as deflection in their path and delay in the arrival of the signal. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a 152.4 m (500 ft) kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall, used a spark-gap transmitter to produce a signal with a frequency of approximately 500 kHz and a power of 100 times more than any radio signal previously produced. The message received was three dits, the Morse code for the letter S. To reach Newfoundland the signal would have to bounce off the ionosphere twice. Dr. Jack Belrose has contested this, however, based on theoretical and experimental work. However, Marconi did achieve transatlantic wireless communications in Glace Bay, Nova Scotia, one year later. In 1902, Oliver Heaviside proposed the existence of the Kennelly–Heaviside layer of the ionosphere which bears his name. Heaviside's proposal included means by which radio signals are transmitted around the Earth's curvature. Also in 1902, Arthur Edwin Kennelly discovered some of the ionosphere's radio-electrical properties. In 1912, the U.S. Congress imposed the Radio Act of 1912 on amateur radio operators, limiting their operations to frequencies above 1.5 MHz (wavelength 200 meters or smaller). The government thought those frequencies were useless. This led to the discovery of HF radio propagation via the ionosphere in 1923. In 1925, observations during a solar eclipse in New York by Dr. Alfred N. Goldsmith and his team demonstrated the influence of sunlight on radio wave propagation, revealing that short waves became weak or inaudible while long waves steadied during the eclipse, thus contributing to the understanding of the ionosphere's role in radio transmission. In 1926, Scottish physicist Robert Watson-Watt introduced the term ionosphere in a letter published only in 1969 in Nature: We have in quite recent years seen the universal adoption of the term 'stratosphere'..and..the companion term 'troposphere'... The term 'ionosphere', for the region in which the main characteristic is large scale ionisation with considerable mean free paths, appears appropriate as an addition to this series. In the early 1930s, test transmissions of Radio Luxembourg inadvertently provided evidence of the first radio modification of the ionosphere; HAARP ran a series of experiments in 2017 using the eponymous Luxembourg Effect. Edward V. Appleton was awarded a Nobel Prize in 1947 for his confirmation in 1927 of the existence of the ionosphere. Lloyd Berkner first measured the height and density of the ionosphere. This permitted the first complete theory of short-wave radio propagation. Maurice V. Wilkes and J. A. Ratcliffe researched the topic of radio propagation of very long radio waves in the ionosphere. Vitaly Ginzburg has developed a theory of electromagnetic wave propagation in plasmas such as the ionosphere. In 1962, the Canadian satellite Alouette 1 was launched to study the ionosphere. Following its success were Alouette 2 in 1965 and the two ISIS satellites in 1969 and 1971, further AEROS-A and -B in 1972 and 1975, all for measuring the ionosphere. On July 26, 1963, the first operational geosynchronous satellite Syncom 2 was launched. On board radio beacons on this satellite (and its successors) enabled – for the first time – the measurement of total electron content (TEC) variation along a radio beam from geostationary orbit to an earth receiver. (The rotation of the plane of polarization directly measures TEC along the path.) Australian geophysicist Elizabeth Essex-Cohen from 1969 onwards was using this technique to monitor the atmosphere above Australia and Antarctica. Geophysics The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about 50 km (30 mi) to more than 1,000 km (600 mi). It exists primarily due to ultraviolet radiation from the Sun. The lowest part of the Earth's atmosphere, the troposphere, extends from the surface to about 10 km (6 mi). Above that is the stratosphere, followed by the mesosphere. In the stratosphere incoming solar radiation creates the ozone layer. At heights of above 80 km (50 mi), in the thermosphere, the atmosphere is so thin that free electrons can exist for short periods of time before they are captured by a nearby positive ion. The number of these free electrons is sufficient to affect radio propagation. This portion of the atmosphere is partially ionized and contains a plasma which is referred to as the ionosphere. Ultraviolet (UV), X-ray and shorter wavelengths of solar radiation are ionizing, since photons at these frequencies contain sufficient energy to dislodge an electron from a neutral gas atom or molecule upon absorption. In this process the light electron obtains a high velocity so that the temperature of the created electronic gas is much higher (of the order of thousand K) than the one of ions and neutrals. The reverse process to ionization is recombination, in which a free electron is "captured" by a positive ion. Recombination occurs spontaneously, and causes the emission of a photon carrying away the energy produced upon recombination. As gas density increases at lower altitudes, the recombination process prevails, since the gas molecules and ions are closer together. The balance between these two processes determines the quantity of ionization present. Ionization depends primarily on the Sun and its Extreme Ultraviolet (EUV) and X-ray irradiance which varies strongly with solar activity. The more magnetically active the Sun is, the more sunspot active regions there are on the Sun at any one time. Sunspot active regions are the source of increased coronal heating and accompanying increases in EUV and X-ray irradiance, particularly during episodic magnetic eruptions that include solar flares that increase ionization on the sunlit side of the Earth and solar energetic particle events that can increase ionization in the polar regions. Thus the degree of ionization in the ionosphere follows both a diurnal (time of day) cycle and the 11-year solar cycle. There is also a seasonal dependence in ionization degree since the local winter hemisphere is tipped away from the Sun, thus there is less received solar radiation. Radiation received also varies with geographical location (polar, auroral zones, mid-latitudes, and equatorial regions). There are also mechanisms that disturb the ionosphere and decrease the ionization. Sydney Chapman proposed that the region below the ionosphere be called neutrosphere (the neutral atmosphere). Layers of ionization At night the F layer is the only layer of significant ionization present, while the ionization in the E and D layers is extremely low. During the day, the D and E layers become much more heavily ionized, as does the F layer, which develops an additional, weaker region of ionization known as the F1 layer. The F2 layer persists by day and night and is the main region responsible for the refraction and reflection of radio waves. The D layer is the innermost layer, 48 to 90 km (30 to 56 mi) above the surface of the Earth. Ionization here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121.6 nanometre (nm) ionizing nitric oxide (NO). In addition, solar flares can generate hard X-rays (wavelength < 1 nm) that ionize N2 and O2. Recombination rates are high in the D layer, so there are many more neutral air molecules than ions. Medium frequency (MF) and lower high frequency (HF) radio waves are significantly attenuated within the D layer, as the passing radio waves cause electrons to move, which then collide with the neutral molecules, giving up their energy. Lower frequencies experience greater absorption because they move the electrons farther, leading to greater chance of collisions. This is the main reason for absorption of HF radio waves, particularly at 10 MHz and below, with progressively less absorption at higher frequencies. This effect peaks around noon and is reduced at night due to a decrease in the D layer's thickness; only a small part remains due to cosmic rays. A common example of the D layer in action is the disappearance of distant AM broadcast band stations in the daytime. During solar proton events, ionization can reach unusually high levels in the D-region over high and polar latitudes. Such very rare events are known as Polar Cap Absorption (PCA) events, because the increased ionization significantly enhances the absorption of radio signals passing through the region. In fact, absorption levels can increase by many tens of dB during intense events, which is enough to absorb most (if not all) transpolar HF radio signal transmissions. Such events typically last less than 24 to 48 hours. The E layer is the middle layer, 90 to 150 km (56 to 93 mi) above the surface of the Earth. Ionization is due to soft X-ray (1–10 nm) and far ultraviolet (UV) solar radiation ionization of molecular oxygen (O2). Normally, at oblique incidence, this layer can only reflect radio waves having frequencies lower than about 10 MHz and may contribute a bit to absorption on frequencies above. However, during intense sporadic E events, the Es layer can reflect frequencies up to 50 MHz and higher. The vertical structure of the E layer is primarily determined by the competing effects of ionization and recombination. At night the E layer weakens because the primary source of ionization is no longer present. After sunset an increase in the height of the E layer maximum increases the range to which radio waves can travel by reflection from the layer. This region is also known as the Kennelly–Heaviside layer or simply the Heaviside layer. Its existence was predicted in 1902 independently and almost simultaneously by the American electrical engineer Arthur Edwin Kennelly (1861–1939) and the British physicist Oliver Heaviside (1850–1925). In 1924 its existence was detected by Edward V. Appleton and Miles Barnett. The Es layer (sporadic E-layer) is characterized by small, thin clouds of intense ionization, which can support reflection of radio waves, frequently up to 50 MHz and rarely up to 450 MHz. Sporadic-E events may last for just a few minutes to many hours. Sporadic E propagation makes VHF-operating by radio amateurs very exciting when long-distance propagation paths that are generally unreachable "open up" to two-way communication. There are multiple causes of sporadic-E that are still being pursued by researchers. This propagation occurs every day during June and July in northern hemisphere mid-latitudes when high signal levels are often reached. The skip distances are generally around 1,640 km (1,020 mi). Distances for one hop propagation can be anywhere from 900 to 2,500 km (560 to 1,550 mi). Multi-hop propagation over 3,500 km (2,200 mi) is also common, sometimes to distances of 15,000 km (9,300 mi) or more. The F layer or region, also known as the Appleton–Barnett layer, extends from about 150 km (93 mi) to more than 500 km (310 mi) above the surface of Earth. It is the layer with the highest electron density, which implies signals penetrating this layer will escape into space. Electron production is dominated by extreme ultraviolet (UV, 10–100 nm) radiation ionizing atomic oxygen. The F layer consists of one layer (F2) at night, but during the day, a secondary peak (labelled F1) often forms in the electron density profile. Because the F2 layer remains by day and night, it is responsible for most skywave propagation of radio waves and long distance high frequency (HF, or shortwave) radio communications. Above the F layer, the number of oxygen ions decreases and lighter ions such as hydrogen and helium become dominant. This region above the F layer peak and below the plasmasphere is called the topside ionosphere. From 1972 to 1975 NASA launched the AEROS and AEROS B satellites to study the F region. Ionospheric model An ionospheric model is a mathematical description of the ionosphere as a function of location, altitude, day of year, phase of the sunspot cycle and geomagnetic activity. Geophysically, the state of the ionospheric plasma may be described by four parameters: electron density, electron and ion temperature and, since several species of ions are present, ionic composition. Radio propagation depends uniquely on electron density. Models are usually expressed as computer programs. The model may be based on basic physics of the interactions of the ions and electrons with the neutral atmosphere and sunlight, or it may be a statistical description based on a large number of observations or a combination of physics and observations. One of the most widely used models is the International Reference Ionosphere (IRI), which is based on data and specifies the four parameters just mentioned. The IRI is an international project sponsored by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI). The major data sources are the worldwide network of ionosondes, the powerful incoherent scatter radars (Jicamarca, Arecibo, Millstone Hill, Malvern, St Santin), the ISIS and Alouette topside sounders, and in situ instruments on several satellites and rockets. IRI is updated yearly. IRI is more accurate in describing the variation of the electron density from bottom of the ionosphere to the altitude of maximum density than in describing the total electron content (TEC). Since 1999 this model is "International Standard" for the terrestrial ionosphere (standard TS16457). Persistent anomalies to the idealized model Ionograms allow deducing, via computation, the true shape of the different layers. Nonhomogeneous structure of the electron/ion-plasma produces rough echo traces, seen predominantly at night and at higher latitudes, and during disturbed conditions. At mid-latitudes, the F2 layer daytime ion production is higher in the summer, as expected, since the Sun shines more directly on the Earth. However, there are seasonal changes in the molecular-to-atomic ratio of the neutral atmosphere that cause the summer ion loss rate to be even higher. The result is that the increase in the summertime loss overwhelms the increase in summertime production, and total F2 ionization is actually lower in the local summer months. This effect is known as the winter anomaly. The anomaly is always present in the northern hemisphere, but is usually absent in the southern hemisphere during periods of low solar activity. Within approximately ± 20 degrees of the magnetic equator, is the equatorial anomaly. It is the occurrence of a trough in the ionization in the F2 layer at the equator and crests at about 17 degrees in magnetic latitude. The Earth's magnetic field lines are horizontal at the magnetic equator. Solar heating and tidal oscillations in the lower ionosphere move plasma up and across the magnetic field lines. This sets up a sheet of electric current in the E region which, with the horizontal magnetic field, forces ionization up into the F layer, concentrating at ± 20 degrees from the magnetic equator. This phenomenon is known as the equatorial fountain. The worldwide solar-driven wind results in the so-called Sq (solar quiet) current system in the E region of the Earth's ionosphere (ionospheric dynamo region) (100–130 km (60–80 mi) altitude).[citation needed] Resulting from this current is an electrostatic field directed west–east (dawn–dusk) in the equatorial day side of the ionosphere. At the magnetic dip equator, where the geomagnetic field is horizontal, this electric field results in an enhanced eastward current flow within ± 3 degrees of the magnetic equator, known as the equatorial electrojet. Ephemeral ionospheric perturbations When the Sun is active, strong solar flares can occur that hit the sunlit side of Earth with hard X-rays. The X-rays penetrate to the D-region, releasing electrons that rapidly increase absorption, causing a high frequency (3–30 MHz) radio blackout that can persist for many hours after strong flares. During this time very low frequency (3–30 kHz) signals will be reflected by the D layer instead of the E layer, where the increased atmospheric density will usually increase the absorption of the wave and thus dampen it. As soon as the X-rays end, the sudden ionospheric disturbance (SID) or radio black-out steadily declines as the electrons in the D-region recombine rapidly and propagation gradually returns to pre-flare conditions over minutes to hours depending on the solar flare strength and frequency. Associated with solar flares is a release of high-energy protons. These particles can hit the Earth within 15 minutes to 2 hours of the solar flare. The protons spiral around and down the magnetic field lines of the Earth and penetrate into the atmosphere near the magnetic poles increasing the ionization of the D and E layers. PCA's typically last anywhere from about an hour to several days, with an average of around 24 to 36 hours. Coronal mass ejections can also release energetic protons that enhance D-region absorption in the polar regions. Geomagnetic storms and ionospheric storms are temporary and intense disturbances of the Earth's magnetosphere and ionosphere. During a geomagnetic storm the F₂ layer will become unstable, fragment, and may even disappear completely. In the Northern and Southern polar regions of the Earth aurorae will be observable in the night sky. Lightning can cause ionospheric perturbations in the D-region in one of two ways. The first is through VLF (very low frequency) radio waves launched into the magnetosphere. These so-called "whistler" mode waves can interact with radiation belt particles and cause them to precipitate onto the ionosphere, adding ionization to the D-region. These disturbances are called "lightning-induced electron precipitation" (LEP) events. Additional ionization can also occur from direct heating/ionization as a result of huge motions of charge in lightning strikes. These events are called early/fast. In 1925, C. T. R. Wilson proposed a mechanism by which electrical discharge from lightning storms could propagate upwards from clouds to the ionosphere. Around the same time, Robert Watson-Watt, working at the Radio Research Station in Slough, UK, suggested that the ionospheric sporadic E layer (Es) appeared to be enhanced as a result of lightning but that more work was needed. In 2005, C. Davis and C. Johnson, working at the Rutherford Appleton Laboratory in Oxfordshire, UK, demonstrated that the Es layer was indeed enhanced as a result of lightning activity. Their subsequent research has focused on the mechanism by which this process can occur. Applications Due to the ability of ionized atmospheric gases to refract high frequency (HF, or shortwave) radio waves, the ionosphere can reflect radio waves directed into the sky back toward the Earth. Radio waves directed at an angle into the sky can return to Earth beyond the horizon. This technique, called "skip" or "skywave" propagation, has been used since the 1920s to communicate at international or intercontinental distances. The returning radio waves can reflect off the Earth's surface into the sky again, allowing greater ranges to be achieved with multiple hops. This communication method is variable and unreliable, with reception over a given path depending on time of day or night, the seasons, weather, and the 11-year sunspot cycle. During the first half of the 20th century it was widely used for transoceanic telephone and telegraph service, and business and diplomatic communication. Due to its relative unreliability, shortwave radio communication has been mostly abandoned by the telecommunications industry, though it remains important for high-latitude communication where the availability of satellite-based radio communication may be insufficient. Shortwave broadcasting is useful in crossing international boundaries and covering large areas at low cost. Automated services still use shortwave radio frequencies, as do radio amateur hobbyists for private recreational contacts and to assist with emergency communications during natural disasters. Armed forces use shortwave so as to be independent of vulnerable infrastructure, including satellites, and the low latency of shortwave communications make it attractive to stock traders, where milliseconds count. When a radio wave reaches the ionosphere, the electric field in the wave forces the electrons in the ionosphere into oscillation at the same frequency as the radio wave. Some of the radio-frequency energy is given up to this resonant oscillation. The oscillating electrons will then either be lost to recombination or will re-radiate the original wave energy. Total refraction can occur when the collision frequency of the ionosphere is less than the radio frequency, and if the electron density in the ionosphere is great enough. A qualitative understanding of how an electromagnetic wave propagates through the ionosphere can be obtained by recalling geometric optics. Since the ionosphere is a plasma, it can be shown that the refractive index is less than unity. Hence, the electromagnetic "ray" is bent away from the normal rather than toward the normal as would be indicated when the refractive index is greater than unity. It can also be shown that the refractive index of a plasma, and hence the ionosphere, is frequency-dependent, see Dispersion (optics). The critical frequency is the limiting frequency at or below which a radio wave is reflected by an ionospheric layer at vertical incidence. If the transmitted frequency is higher than the plasma frequency of the ionosphere, then the electrons cannot respond fast enough, and they are not able to re-radiate the signal. It is calculated as shown below: where N = electron density per m3 and fcritical is in Hz. The Maximum Usable Frequency (MUF) is defined as the upper frequency limit that can be used for transmission between two points at a specified time. where α {\displaystyle \alpha } = angle of arrival, the angle of the wave relative to the horizon, and sin is the sine function. The cutoff frequency is the frequency below which a radio wave fails to penetrate a layer of the ionosphere at the incidence angle required for transmission between two specified points by refraction from the layer. There are a number of models used to understand the effects of the ionosphere on global navigation satellite systems. The Klobuchar model is currently used to compensate for ionospheric effects in GPS. This model was developed at the US Air Force Geophysical Research Laboratory circa 1974 by John (Jack) Klobuchar. The Galileo navigation system uses the NeQuick model. GALILEO broadcasts 3 coefficients to compute the effective ionization level, which is then used by the NeQuick model to compute a range delay along the line-of-sight. The open system electrodynamic tether, which uses the ionosphere, is being researched. The space tether uses plasma contactors and the ionosphere as parts of a circuit to extract energy from the Earth's magnetic field by electromagnetic induction. Measurements Scientists explore the structure of the ionosphere by a wide variety of methods. They include: A variety of experiments, such as HAARP (High Frequency Active Auroral Research Program), involve high power radio transmitters to modify the properties of the ionosphere. These investigations focus on studying the properties and behavior of ionospheric plasma, with particular emphasis on being able to understand and use it to enhance communications and surveillance systems for both civilian and military purposes. HAARP was started in 1993 as a proposed twenty-year experiment, and is currently active near Gakona, Alaska. The SuperDARN radar project researches the high- and mid-latitudes using coherent backscatter of radio waves in the 8 to 20 MHz range. Coherent backscatter is similar to Bragg scattering in crystals and involves the constructive interference of scattering from ionospheric density irregularities. The project involves more than 11 countries and multiple radars in both hemispheres. Scientists are also examining the ionosphere by the changes to radio waves, from satellites and stars, passing through it. The Arecibo Telescope located in Puerto Rico, was originally intended to study Earth's ionosphere. Ionograms show the virtual heights and critical frequencies of the ionospheric layers and which are measured by an ionosonde. An ionosonde sweeps a range of frequencies, usually from 0.1 to 30 MHz, transmitting at vertical incidence to the ionosphere. As the frequency increases, each wave is refracted less by the ionization in the layer, and so each penetrates further before it is reflected. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency just exceeds the peak plasma, or critical, frequency of the layer. Tracings of the reflected high frequency radio pulses are known as ionograms. Reduction rules are given in: "URSI Handbook of Ionogram Interpretation and Reduction", edited by William Roy Piggott and Karl Rawer, Elsevier Amsterdam, 1961 (translations into Chinese, French, Japanese and Russian are available). Incoherent scatter radars operate above the critical frequencies. Therefore, the technique allows probing the ionosphere, unlike ionosondes, also above the electron density peaks. The thermal fluctuations of the electron density scattering the transmitted signals lack coherence, which gave the technique its name. Their power spectrum contains information not only on the density, but also on the ion and electron temperatures, ion masses and drift velocities. Incoherent scatter radars can also measure neutral atmosphere movements, such as atmospheric tides, after making assumptions about ion-neutral collision frequency across the ionospheric dynamo region. Radio occultation is a remote sensing technique where a GNSS signal tangentially scrapes the Earth, passing through the atmosphere, and is received by a Low Earth Orbit (LEO) satellite. As the signal passes through the atmosphere, it is refracted, curved and delayed. An LEO satellite samples the total electron content and bending angle of many such signal paths as it watches the GNSS satellite rise or set behind the Earth. Using an Inverse Abel's transform, a radial profile of refractivity at that tangent point on earth can be reconstructed. Major GNSS radio occultation missions include the GRACE, CHAMP, and COSMIC. Indices of the ionosphere In empirical models of the ionosphere such as Nequick, the following indices are used as indirect indicators of the state of the ionosphere. F10.7 and R12 are two indices commonly used in ionospheric modelling. Both are valuable for their long historical records covering multiple solar cycles. F10.7 is a measurement of the intensity of solar radio emissions at a frequency of 2800 MHz made using a ground radio telescope. R12 is a 12 months average of daily sunspot numbers. The two indices have been shown to be correlated with each other. However, both indices are only indirect indicators of solar ultraviolet and X-ray emissions, which are primarily responsible for causing ionization in the Earth's upper atmosphere. We now have data from the GOES spacecraft that measures the background X-ray flux from the Sun, a parameter more closely related to the ionization levels in the ionosphere. Ionospheres of other planets and natural satellites Objects in the Solar System that have appreciable atmospheres (i.e., all of the major planets and many of the larger natural satellites) generally produce ionospheres. Planets known to have ionospheres include Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. The atmosphere of Titan includes an ionosphere that ranges from about 880 to 1,300 km (550 to 810 mi) in altitude and contains carbon compounds. Ionospheres have also been observed at Io, Europa, Ganymede, Triton, and Pluto. See also Notes References External links |
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Contents Glashtyn Glashtyn (Manx English: glashtin, glashtan [ˈɡlaʃθən] or glashan; Manx: glashtin or glashtyn [ˈɡlaʃtʲənʲ]) is a legendary creature from Manx folklore. The glashtin is said to be a goblin that appears out of its aquatic habitat, to come in contact with the island folk; others claim it takes the shape of a colt, or equate it to the water horse known locally as cabbyl-ushtey. Yet another source claims the glashtin was a water-bull (tarroo-ushtey in Manx), half-bovine and half-equine. Some tales or lore recount that it has pursued after women, ending in the stock motif of escape by cutting loose the skirt-hem, although in one modern version her escape is achieved by a rooster's crowing; in that tale the glashtin pretends to be a handsome man but is betrayed by his horse-ears. Lexicography The word glashtin is thought to derive from Celtic glais (Old Irish: glais, glaise, glas), meaning "stream", or sometimes even the sea. "Glashtin" is the orthography in the Manx language according to Cregeen's dictionary (1835), and this is the spelling adhered to by Joseph Train, A. W. Moore and various other 19th century authorities of Manx folklore. However the spelling "Glashtyn" is used as heading in John Kelly's Fockleyr dictionary of 1866. Manx Gaelic glashtin, glashtyn is pronounced /ɡlaʃtʲənʲ/ according to a recent paper on the language.[a] In the Manx English dialect, "Glashan, glashtan, glashtin" as 'hairy goblin' is the primary (and most detailed) entry given in Moore's posthumous dictionary (1924), completed in collaboration with Morrison and Goodwin. Glashtan, glashtin ([glaʃən]) and glashan ([glaʃþən]) are the phonology given in Moore's dictionary.[b][c] The form "glashan" is found in folklore examples collect on a southerly island (Calf of Man) by J. F. Campbell.[d] Definitions The Celtic Manx term glashtin is a masculine noun denoting "a goblin, a sprite" according to Cregeen's dictionary, while Moore's Manx English dictionary gives "hairy goblin", which can also be applied figuratively to a "big, hulking boy". Kelly adds that the goblin emerges out of water. But according to Manx writer Joseph Train, "the glashtin is a water-horse that formerly, like the §taroo-ushtey, left his native element to associate with land animals of the same class". This dual picture prompted A. W. Moore to comment that the glashan or glashtin is sometimes ascribed a hairy goblin's attributes, like the fenodyree's, and sometimes horse-like attributes, like the cabbyl-ushtey's. Welsh scholar Rhys also concurred, saying that his "informants" were at odds, some of them regarding the "glastyn" as the Manx version of the brownie, while others were adamant it was "a sort of grey colt, frequenting the banks of lakes at night".[e] The two conflicting accounts above can be reconciled by regarding the Manx glashtin as a shape-shifter. Recent literature embracing this notion claims that the equine glashtin assumes human form at times, but betrays his identity when he fails to conceal his ears, which are pointed like a horse's. One modern fairy tale relates how a fisherman's daughter living in Scarlett outwitted the foreign-tongued "dark and handsome" stranger whom she recognized as glashtin by his horse's ears. She knew she was in peril because according to lore, the glashtin had the ill habit of transforming into a "water-horse" and dragging women to sea. Reversed hooves Although the glashtin may assume a normal horse's guise, it had hooves which "were back to front", writes Wiltshire native folklore author Ralph Whitlock, writing in 1979. The reversed hooves has been ascribed to the Shetlandic njogel by James A. Teit back in 1918. Folklore attestations An early commentary on the glashtin occurs in Joseph Train's History (1845).[f] According to Train, the glashtin is a sort of a water-horse, while at the same time, the fairy fiddler Hom Mooar was a glashtin as well, thus providing a dichotomous picture of the legendary creature. In one passage, Train claims the glashtin to be a water-horse, and that this sea-glashtin would at one time emerge from his marine habitat, mingling with the local land-roving ponies, and cross breed to produce foal. Train drew similarity to the Manx water-bull (see taroo ushtey below) which also shared the trait of mingling with land livestock. In fact the water-bull attempts to mate with domesticated cows as well, only unsuccessfully, according to George Waldron (1731).[g][h] The glashtin, it was said, ceased to appear after the islanders started cross-breeding their native horses with breeds from the outside. German mythographer Karl Blind noted that Manx glashtin or elashtan "attacks lonely women" as is the case with the Shetlandic nuggle and the Scottish kelpie. The creature was known to have great curiosity for women and pester them in rather picaresque manner, and would grab hold and tear off pieces of women's attire. One anecdote concerns a glashan who caught a girl by getting a tight grip-hold of her dress. But while he slept, she cut away the dress and escaped, making him cast away the cloth, uttering something in Manx unintelligible to Campbell. Charles Roeder records a similar tale of a woman who loosened her apron-string to rid herself of the glashtin clung on her apron, and he spoke these words: 'Rumbyl, rumbyl, cha vel ayms agh yn sampyl' (The edge or skirt of the garment, I have but the sample).[i] Sophia Morrison gives another version with this tale motif, entitled "The Buggane of the Glen Meay Waterfall". In the aforementioned modern fairy tale, on a stormy night in Scarlett, the girl Kirree Quayle gave refuge to a dark, handsome stranger, but afterwards recognized him be a glashtin, deducing from his horse ears. She feared for herself knowing the creature was reputed to shape-shift into a water-horse and drag women to sea. As her fisherman father was late, she wished for dawn's break which would banish any non-mortals. She resisted his temptation of a strand of pearls dangled before her, and when grabbed she let out a scream, causing the red cockerel to crow, prematurely announcing the break of dawn, scaring the glashtin away. Train also alleged that the renowned Hom Mooar (which signifies "Big Tom", a name of a fairy fiddler), was a glashtin. He goes on to supply as an example a tale taken from Waldron, describing a man was lured by invisible musicians to a strange banquet, and obtained the silver cup that came to be used for the "consecrated Wine in Kirk-Merlugh (Malew Church), even though Waldron never refers to the enchanted musicians as glashtin or "Big Tom". Manx lore concerning a helpful glashan was collected by Scottish folklorist J. F. Campbell, from a woman living on the Calf of Man in the southern part of the Isle of Man. The story-telling woman described a creature or being which assisted her as farmhand, performing the tasks of rounding up sheep from the fold, or threshing stalks of corn left unbundled.[j] Similar or conflated mythical creatures tarroo-ushtey (Manx pronunciation: [ˌtaru ˈuʃtʲə], Manx English pronunciation:[ˈtaru ˈùʃtþə], Mx. for "water bull") The 18th century Manx local historian George Waldron records the superstition about the Water-Bull, an "amphibious creature" with every semblance of a natural bull, but a cow mating with it calves only a misshapen "lump of flesh and skin without bones" and often dies giving birth. Waldron also wrote that a neighbor detected a stray bull in his herd and, suspecting it to be a Water-Bull, rounded up a group of men with pitchforks to give it chase. The beast, however, dived into a river and eluded them, bobbing its head up in mockery. It was Train who later supplied the equivalent name in the Manx language, and made similarity comparisons to the glashtin. John Nelson (1840-1910), a Manx informant well-versed in local Gaelic lore, argued that the water-bull was "supposed to be a goblin half cow and half horse" and so it and the glashtin were one and the same. cabbyl-ushtey[k] (Manx pronunciation: [ˈkaːvəl ˈuʃtʲə], [ˈkabəlˈuʃtʲə], Manx English pronunciation:[ˈkāvəl ˈùʃtþə], Mx. for "water horse") Manx folklorist and historian Arthur William Moore was unable to avoid the dichotomy regarding the glashtin. In one instance, Moore represents the glashtin as "a hairy goblin or sprite", but also says glashtin was another name for a water-horse or the cabbyl-ushtey.[l] Moore says there was a sighting of the horse in 1859 at Ballure Glen, and after being spotted people from nearby Ramsey flocked to see, but no one caught sight of it. The glen beneath the Glen Meay Waterfall (near Peel; see Morrison's tale above) was haunted by the ghost of a man who unwittingly rode on the horseback of the glashtin or cabbyl-ushtey, and was drowned at sea.[m] One tale recounts how a cabbyl-ushtey emerged from the Awin Dhoo (Black River) and devoured a farmer's cow, then later it took his teenaged daughter. Nevertheless, recent literature makes the cabbyl-ushtey as being more benign than the Scottish Gaelic each-uisge. See also Explanatory notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/C11_(C_standard_revision)] | [TOKENS: 476] |
Contents C11 (C standard revision) C11 (previously C1X, formally ISO/IEC 9899:2011) is a past standard for the C programming language. It replaced C99 (standard ISO/IEC 9899:1999) and was superseded by C17 (standard ISO/IEC 9899:2018). C11 mainly standardizes features already supported by common contemporary compilers, and includes a detailed memory model to better support multiple threads of execution. Due to delayed availability of conforming C99 implementations, C11 makes certain features optional, to make it easier to comply with the core language standard. The final draft, N1570, was published in April 2011. The new standard passed its final draft review on October 10, 2011 and was officially ratified by ISO and published as ISO/IEC 9899:2011 on December 8, 2011, with no comments requiring resolution by participating national bodies. A standard macro __STDC_VERSION__ is defined with value 201112L to indicate that C11 support is available. Changes from C99 The standard includes several changes to the C99 language and library specifications, such as Optional features The new revision allows implementations to not support certain parts of the standard — including some that had been mandatory to support in the 1999 revision. Programs can use predefined macros to determine whether an implementation supports a certain feature or not. Compiler support Some features of C11 are supported by the GCC starting with version 4.6, Clang starting with version 3.1, IBM XL C starting with version 12.1, and Microsoft Visual C++ starting with VS 2019 (16.8) in September 2020. Criticism The optional bounds-checking interfaces (Annex K) remain controversial and have not been widely implemented, and their deprecation or removal from the next standard revision has been proposed. Even Microsoft, a main proponent of this interface, does not conform to the definition. In addition, Annex K does not include the more useful TR24731-2 (dynamic allocation functions), such as vasprintf and open_memstream. The few open-source implementations include Open Watcom C/C++'s "Safer C" library and safeclib. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Revisionist_Maximalism] | [TOKENS: 1687] |
Contents Revisionist Maximalism Revisionist Maximalism was a short-lived right-wing militant political ideology and Jewish militant ideology which was part of the Brit HaBirionim faction of the Zionist Revisionist Movement (ZRM) created by Abba Ahimeir. History The ideology and political faction of Revisionist Maximalism was officially created in 1930 by Abba Ahimeir, a Jewish historian, journalist, and politician. Abba Ahimier was born in Russia in 1897 and migrated to Palestine at the age of fifteen. After the end of World War I, Ahimier entered the University of Kiev in the Russian Empire, then traveled to Liege and Vienna to complete his academic studies. He then returned to Palestine and became close in contact with other socialist circles, and organizations. In 1928 Ahimier joined Ze'ev Jabotinsky's Revisionist movement and became one of the movement's important activists. He called for the Zionist Revisionist Movement (ZRM) to adopt the principles of totalitarianism to create a "pure nationalism" amongst Jews. Ahimeir was originally a member of the Jewish Labour Movement who supported the October Revolution in Russia in 1917, and called for Jews to have their "own 1917" and spoke of the need for an October Revolution in Zionism. However Ahimeir grew disillusioned with Russian Bolshevism which he began to see as a Russian nationalist movement rather than a movement to promote international class struggle. Having become disillusioned with communism, Ahimeir grew nationalistic after the Arab-Jewish violence occurred in the British Mandate of Palestine from 1928 to 1929. Revisionist Maximalism rejects communism, humanism, internationalism, liberalism, pacifism and socialism; condemned liberal Zionists for only working for middle-class Jews rather than the Jewish nation as a whole. After the rise of anti-Jewish violence in the British Mandate of Palestine one year prior, support for the Brit HaBirionim faction of the ZRM soared, Brit HaBirionim quickly became the largest faction within the ZRM in 1930. In 1931 Jabotinsky, and members of the Revisionist movement launched an attack on the 17th Zionist Congress, in order to force Chaim Weizmann to resign as president of the World Zionist Organization. Jabotinsky along with the other Revisionist Zionists, wanted to obtain all of Eretz Yisrael, (Land of Israel) and establish a Jewish state, and did not settle for a two state solution in Palestine. Soon, Abba Ahimier, the poet Uri Zvi Greenberg, and Wolfgang von Weisl, the chairman of their Palestine central committee, became the ideological leaders of the Revisionists, after Jabotinsky was banned from returning to Palestine by the British authorities, due to his political activities. During the 1930s, Abba Ahimier Joshua Yevin, and Uri Zvi Grunberg began to establish their own newspaper, Hazit HaAm, and would publish the idea of "Jewish Labor" and emphasized that Jews should be self-reliant and economically independent. In December 1932 Ahimier, along with Weisl, Gruenberg, and his supporters organized a strike-breaking "union" at the Froumine Biscuit Factory in Jerusalem by providing scabs. Then on February 27, 1933, the Maximalist tried to break a building strike in Petah Tikva, where dozens of strikers were arrested for battling the scabs. In 1930, Brit HaBirionim under Ahimeir's leadership publicly declared their desire to form a fascist state at the conference of the ZRM, saying: It is not the masses whom we need ... but the minorities ... We want to educate people for the 'Great Day of God' (war or world revolution), so that they will be ready to follow the leader blindly into the greatest danger ... Not a party but an Orden, a group of private [people], devoting themselves and sacrificing themselves for the great goal. They are united in all, but their private lives and their livelihood are the matter of the Orden. Iron discipline; cult of the leader (on the model of the fascists); dictatorship. Abba Achimeir, 1930 Ahimeir claimed that the Jewish people would outlast Arab rule in the region of Palestine, saying: We fought the Egyptian Pharaoh, the Roman emperors, the Spanish Inquisition, the Russian tsars. They 'defeated' us. But where are they today? Can we not cope with a few despicable muftis or sheiks? ... For us, the forefathers, the prophets, the zealots were not mythological concepts... Abba Achimeir, 1930. Revisionist Maximalism and the Brit HaBirionim movement were fierce opponents of pacifism, while promoting militarism and demonstrated in 1932 against Norman Bentwich's inaugural lecture on peace to which Ahimeir saying that "It is not a cathedral to international peace in the name of Bentwich that we need, but a military academy in the name of Ze'ev Jabotinsky" and said "we can defend the honour of Israel ... not by filling our bellies with lectures on peace ... but rather by learning the doctrine of Jabotinsky". Brit HaBirionim demonstrators outside handed out leaflets declaring that peace studies were "the work of Satan" and were "an anti-Zionist measure, a stab in the back of Zionism.". Ahimeir believed that his ideology would constitute a "neo-Revisionism" within the Zionist movement that he criticized, and advocated it at a meeting of the Hatzohar movement in Vienna in 1932, saying: Zionism is imbued with the ghetto and pronouncements. The path to Jewish sovereignty has to cross a bridge of steel, not a bridge of paper. ... I bring to you a new form of social organization, one that is free of principles and parties ... I bring you Neo-Revisionism. In 1932, Brit HaBirionim pressed the ZRM to adopt their policies which were titled the "Ten Commandments of Maximalism", which were made under "In the spirit of Complete Fascism", according to Stein Uglevik. Moderate ZRM members refused to accept this and moderate ZRM member Yaacov Kahan pressured Brit HaBirionim to accept the democratic nature of the ZRM and not push for the party to adopt fascist dictatorial policies. Ideology The Revisionist Maximalist borrowed principles from totalitarianism, fascism and inspiration from Józef Piłsudski's Poland and Benito Mussolini's Italy. Revisionist Maximalists strongly supported the Italian fascist regime of Benito Mussolini and wanted the creation of a Jewish state based on fascist principles. The Revisionist Maximalists became the largest faction in the ZRM in 1930 but collapsed in support in 1933 after Ahimeir's support for the assassination of Haim Arlosoroff. The Maximalist goal was to "extract Revisionism from its liberal entrapment", as they wanted Jabotinsky's status to be elevated to a dictator, and desired to force integrate the population of Palestine into Hebrew society. The Maximalists believed that authoritarianism and national solidarity was necessary to have the public collaborate with the government, and to create total unity in Palestine. The label of "fascist" has nevertheless to be regarded with reserves because in that period as later it was used often abusively in the disputes between opposed political non-fascist factions, as in the 1930s even the Social Democrat parties were accused by Stalin and the communists of being "fascists" or "social-fascists". In the same way in Palestine Revisionist Zionists themselves were often qualified in the 1930s as "fascists" by the Labor Zionist leaders and the Revisionists attacked the social democratic dominated General Confederation of Labor (Histadrut) and Ben Gurion by use of terms like "Red Swastika" and comparisons with fascism and Hitler. See also References |
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[SOURCE: https://en.wikipedia.org/w/index.php?title=Social_network&action=edit§ion=8] | [TOKENS: 1430] |
Editing Social network (section) Copy and paste: – — ° ′ ″ ≈ ≠ ≤ ≥ ± − × ÷ ← → · § Cite your sources: <ref></ref> {{}} {{{}}} | [] [[]] [[Category:]] #REDIRECT [[]] <s></s> <sup></sup> <sub></sub> <code></code> <pre></pre> <blockquote></blockquote> <ref></ref> <ref name="" /> {{Reflist}} <references /> <includeonly></includeonly> <noinclude></noinclude> {{DEFAULTSORT:}} <nowiki></nowiki> <!-- --> <span class="plainlinks"></span> Symbols: ~ | ¡ ¿ † ‡ ↔ ↑ ↓ • ¶ # ∞ ‹› «» ¤ ₳ ฿ ₵ ¢ ₡ ₢ $ ₫ ₯ € ₠ ₣ ƒ ₴ ₭ ₤ ℳ ₥ ₦ ₧ ₰ £ ៛ ₨ ₪ ৳ ₮ ₩ ¥ ♠ ♣ ♥ ♦ 𝄫 ♭ ♮ ♯ 𝄪 © ¼ ½ ¾ Latin: A a Á á À à  â Ä ä Ǎ ǎ Ă ă Ā ā à ã Å å Ą ą Æ æ Ǣ ǣ B b C c Ć ć Ċ ċ Ĉ ĉ Č č Ç ç D d Ď ď Đ đ Ḍ ḍ Ð ð E e É é È è Ė ė Ê ê Ë ë Ě ě Ĕ ĕ Ē ē Ẽ ẽ Ę ę Ẹ ẹ Ɛ ɛ Ǝ ǝ Ə ə F f G g Ġ ġ Ĝ ĝ Ğ ğ Ģ ģ H h Ĥ ĥ Ħ ħ Ḥ ḥ I i İ ı Í í Ì ì Î î Ï ï Ǐ ǐ Ĭ ĭ Ī ī Ĩ ĩ Į į Ị ị J j Ĵ ĵ K k Ķ ķ L l Ĺ ĺ Ŀ ŀ Ľ ľ Ļ ļ Ł ł Ḷ ḷ Ḹ ḹ M m Ṃ ṃ N n Ń ń Ň ň Ñ ñ Ņ ņ Ṇ ṇ Ŋ ŋ O o Ó ó Ò ò Ô ô Ö ö Ǒ ǒ Ŏ ŏ Ō ō Õ õ Ǫ ǫ Ọ ọ Ő ő Ø ø Œ œ Ɔ ɔ P p Q q R r Ŕ ŕ Ř ř Ŗ ŗ Ṛ ṛ Ṝ ṝ S s Ś ś Ŝ ŝ Š š Ş ş Ș ș Ṣ ṣ ß T t Ť ť Ţ ţ Ț ț Ṭ ṭ Þ þ U u Ú ú Ù ù Û û Ü ü Ǔ ǔ Ŭ ŭ Ū ū Ũ ũ Ů ů Ų ų Ụ ụ Ű ű Ǘ ǘ Ǜ ǜ Ǚ ǚ Ǖ ǖ V v W w Ŵ ŵ X x Y y Ý ý Ŷ ŷ Ÿ ÿ Ỹ ỹ Ȳ ȳ Z z Ź ź Ż ż Ž ž ß Ð ð Þ þ Ŋ ŋ Ə ə Greek: Ά ά Έ έ Ή ή Ί ί Ό ό Ύ ύ Ώ ώ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω {{Polytonic|}} Cyrillic: А а Б б В в Г г Ґ ґ Ѓ ѓ Д д Ђ ђ Е е Ё ё Є є Ж ж З з Ѕ ѕ И и І і Ї ї Й й Ј ј К к Ќ ќ Л л Љ љ М м Н н Њ њ О о П п Р р С с Т т Ћ ћ У у Ў ў Ф ф Х х Ц ц Ч ч Џ џ Ш ш Щ щ Ъ ъ Ы ы Ь ь Э э Ю ю Я я ́ IPA: t̪ d̪ ʈ ɖ ɟ ɡ ɢ ʡ ʔ ɸ β θ ð ʃ ʒ ɕ ʑ ʂ ʐ ç ʝ ɣ χ ʁ ħ ʕ ʜ ʢ ɦ ɱ ɳ ɲ ŋ ɴ ʋ ɹ ɻ ɰ ʙ ⱱ ʀ ɾ ɽ ɫ ɬ ɮ ɺ ɭ ʎ ʟ ɥ ʍ ɧ ʼ ɓ ɗ ʄ ɠ ʛ ʘ ǀ ǃ ǂ ǁ ɨ ʉ ɯ ɪ ʏ ʊ ø ɘ ɵ ɤ ə ɚ ɛ œ ɜ ɝ ɞ ʌ ɔ æ ɐ ɶ ɑ ɒ ʰ ʱ ʷ ʲ ˠ ˤ ⁿ ˡ ˈ ˌ ː ˑ ̪ {{IPA|}} This page is a member of 6 hidden categories (help): |
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[SOURCE: https://en.wikipedia.org/wiki/Sony_Corporation] | [TOKENS: 11890] |
Contents Sony Sony Group Corporation[b], commonly referred to as Sony[c], is a Japanese multinational conglomerate headquartered at Sony City in Minato, Tokyo, Japan. The Sony Group encompasses various businesses, including electronics (Sony Corporation), imaging and sensing (Sony Semiconductor Solutions), film (Sony Pictures Entertainment), music (Sony Music Group and Sony Music Entertainment Japan), video games (Sony Interactive Entertainment), and others. Sony was founded in 1946 as initially Tokyo Tsushin Kogyo K.K.[d] by Masaru Ibuka and Akio Morita. In 1958, the company adopted the name Sony Corporation.[e] Initially an electronics firm, it gained early recognition for products such as the TR-55 transistor radio and the CV-2000 home video tape recorder, contributing significantly to Japan's post-war economic recovery. After Ibuka's retirement in the 1970s, Morita served as chairman until 1994, overseeing Sony's rise as a global brand recognized for innovation in consumer electronics. Landmark products included the Trinitron color television, the Walkman portable audio player, and the co-development of the compact disc. Expanding beyond electronics, Sony acquired Columbia Records in 1988 and Columbia Pictures in 1989, while also entering the home video game console market with the launch of the PlayStation in 1994. In Japan, the company further diversified by establishing a financial services division, that would be turned into a separate company in September 2025, with the group maintaining 20% of the shares. In 2021, the company was renamed Sony Group Corporation as it transitioned into a holding company structure, with its electronics business continuing under the name Sony Corporation. As of 2020[update], Sony holds a 55% share of the global image sensor market, making it the largest image sensor manufacturer, the second largest camera manufacturer, a semiconductor sales leader, and the world's third-largest television manufacturer by sales. Although Sony is not part of a traditional keiretsu, it has historical ties to the Sumitomo Mitsui Financial Group, dating back to the 1950s when it relied exclusively on Mitsui Bank for financing. Sony is publicly traded on the Tokyo Stock Exchange (a component of the Nikkei 225 and TOPIX Core30 indices) and also maintains American depositary receipts on the New York Stock Exchange, where it has been listed since 1961. As of 2021, it ranked 88th on the Fortune Global 500 and 57th on the 2023 Forbes Global 2000 list. History Sony began in the wake of World War II. In 1946, Masaru Ibuka started an electronics shop in Shirokiya, a department store building in the Nihonbashi area of Tokyo. The company started with a capital of ¥190,000 and a total of eight employees. On 7 May 1946, Ibuka was joined by Akio Morita to establish a company called Tokyo Tsushin Kogyo (東京通信工業, Tōkyō Tsūshin Kōgyō; Tokyo Telecommunications Engineering Corporation). The company built Japan's first tape recorder, called the Type-G. In 1958, the company changed its name to "Sony". Tokyo Tsushin Kogyo founders Morita and Ibuka realized that to achieve success and grow, their business had to expand to the global market, which required labeling their products with a short and easy brand name. While looking for a romanized name, they at first strongly considered using their initials, TTK. The primary reason they did not is that the railway company Tokyo Kyuko was known as TTK. The company occasionally used the syllabic acronym "Totsuko" in Japan, but during his visit to the United States, Morita discovered that Americans had trouble pronouncing that name. Another early name that was tried out for a while was "Tokyo Teletech" until Akio Morita discovered that there was an American company already using Teletech as a brand name. The name "Sony" was chosen for the brand as a mix of two words: one was the Latin word "sonus", which is the root of sonic and sound, and the other was "sonny", a common slang term used in 1950s America to call a young boy. In 1950s Japan, "sonny boys" was a loan word in Japanese, which connoted smart and presentable young men, which Akio Morita and Masaru Ibuka considered themselves to be. The first Sony-branded product, the TR-55 transistor radio, appeared in 1955, but the company name did not change to Sony until January 1958. At the time of the change, it was extremely unusual for a Japanese company to use Roman letters to spell its name instead of writing it in kanji. The move was not without opposition: TTK's principal bank at the time, Mitsui, had strong feelings about the name. They pushed for a name such as Sony Electronic Industries, or Sony Teletech. Akio Morita was firm, however, as he did not want the company name tied to any particular industry. Eventually, both Ibuka and Mitsui Bank's chairman gave their approval. According to Schiffer, Sony's TR-63 radio "cracked open the U.S. market and launched the new industry of consumer microelectronics." By the mid-1950s, American teens had begun buying portable transistor radios in huge numbers, helping to propel the fledgling industry from an estimated 100,000 units in 1955 to 5 million units by the end of 1968. Sony co-founder Akio Morita founded Sony Corporation of America in 1960. In the process, he was struck by the mobility of employees between American companies, which was unheard of in Japan at that time. When he returned to Japan, he encouraged experienced, middle-aged employees of other companies to reevaluate their careers and consider joining Sony. The company filled many positions in this manner, and inspired other Japanese companies to do the same. Moreover, Sony played a major role in the development of Japan as a powerful exporter during the 1960s, 1970s and 1980s, supplying the U.S. Military with bomb parts used in the Vietnam War. It also helped to significantly improve American perceptions of "made in Japan" products. Known for its production quality, Sony was able to charge above-market prices for its consumer electronics and resisted lowering prices. In 1971, Masaru Ibuka handed the position of president over to his co-founder Akio Morita. Sony began a life insurance company in 1979, one of its many peripheral businesses. Amid a global recession in the early 1980s, electronics sales dropped and the company was forced to cut prices. Sony's profits fell sharply. "It's over for Sony", one analyst concluded. "The company's best days are behind it." Around that time, Norio Ohga took up the role of president. He encouraged the development of the compact disc (CD) in the 1970s and 1980s, and of the PlayStation in the early 1990s. Ohga went on to purchase CBS Records in 1988 and Columbia Pictures in 1989, greatly expanding Sony's media presence. Ohga would succeed Morita as chief executive officer in 1989.[citation needed] Under the vision of co-founder Akio Morita and his successors, the company had aggressively expanded into new businesses. Part of its motivation for doing so was the pursuit of "convergence", linking film, music and digital electronics via the Internet. This expansion proved unrewarding and unprofitable, threatening Sony's ability to charge a premium on its products as well as its brand name. In 2005, Howard Stringer replaced Nobuyuki Idei as chief executive officer, marking the first time that a foreigner had run a major Japanese electronics firm. Stringer helped to reinvigorate the company's struggling media businesses, encouraging blockbusters such as Spider-Man while cutting 9,000 jobs. He hoped to sell off peripheral business and focus the company again on electronics. Furthermore, he aimed to increase cooperation between business units, which he described as "silos" operating in isolation from one another. In a bid to provide a unified brand for its global operations, Sony introduced a slogan known as "make.believe" in 2009.[citation needed] Despite some successes, the company faced continued struggles in the mid- to late-2000s. In 2012, Kazuo Hirai was promoted to president and CEO, replacing Stringer. Shortly thereafter, Hirai outlined his company-wide initiative, named "One Sony" to revive Sony from years of financial losses and bureaucratic management structure, which proved difficult for former CEO Stringer to accomplish, partly due to differences in business culture and native languages between Stringer and some of Sony's Japanese divisions and subsidiaries. Hirai outlined three major areas of focus for Sony's electronics business, which include imaging technology, gaming and mobile technology, as well as a focus on reducing the major losses from the television business. In February 2014, Sony announced the sale of its Vaio PC division to a new corporation owned by investment fund Japan Industrial Partners and spinning its TV division into its own corporation as to make it more nimble to turn the unit around from past losses totaling $7.8 billion over a decade. Later that month, they announced that they would be closing 20 stores. In April, the company announced that they would be selling 9.5 million shares in Square Enix (roughly 8.2 percent of the game company's total shares) in a deal worth approximately $48 million. In May 2014 the company announced it was forming two joint ventures with Shanghai Oriental Pearl Group to manufacture and market Sony's PlayStation game consoles and associated software in China. In 2015, Sony purchased Toshiba's image sensor business. It was reported in December 2016 by multiple news outlets that Sony was considering restructuring its U.S. operations by merging its TV & film business, Sony Pictures Entertainment, with its gaming business, Sony Interactive Entertainment. According to the reports, such a restructuring would have placed Sony Pictures under Sony Interactive's CEO, Andrew House, though House would not have taken over day-to-day operations of the film studio. According to one report, Sony was set to make a final decision on the possibility of the merger of the TV, film, & gaming businesses by the end of its fiscal year in March of the following year (2017). In 2017, Sony sold its lithium-ion battery business to Murata Manufacturing. In 2019, Sony merged its mobile, TV and camera businesses. On 1 April 2020, Sony Electronics Corporation was established as an intermediate holding company to own and oversee its electronics and IT solutions businesses. On 19 May 2020, the company announced that it would change its name to Sony Group Corporation as of 1 April 2021. Subsequently, Sony Electronics Corporation would be renamed to Sony Corporation. On the same day the company announced that it would turn Sony Financial Holdings (currently Sony Financial Group), of which Sony already owns 65.06% of shares, to a wholly owned subsidiary through a takeover bid. On 1 April 2021, Sony Corporation was renamed Sony Group Corporation. On the same day, Sony Mobile Communications Inc. absorbed Sony Electronics Corporation, Sony Imaging Products & Solutions Inc., and Sony Home Entertainment & Sound Products Inc. and changed its trade name to Sony Corporation. Formats and technologies Sony has historically been notable for creating its own in-house standards for new recording and storage technologies, instead of adopting those of other manufacturers and standards bodies, while its success in the early years owes to a smooth capitalization on the Digital Compact Cassette standard introduced by Philips, with which Sony went on to enjoy a decades-long technological relationship in various areas. Sony (either alone or with partners) has introduced several of the most popular recording formats, including the 3.5-inch floppy disk, compact disc and Blu-ray disc. Sony introduced U-matic, the world's first videocassette format, in 1971, but the standard was unpopular for domestic use due to the high price. The company subsequently launched the Betamax format in 1975. Sony was involved in the videotape format war of the early 1980s, when they were marketing the Betamax system for video cassette recorders against the VHS format developed by JVC. In the end, VHS gained critical mass in the marketbase and became the worldwide standard for consumer VCRs. Betamax is, for all practical purposes, an obsolete format. Sony's professional-oriented component video format called Betacam, which was derived from Betamax, was used until 2016 when Sony announced it was stopping production of all remaining 1/2-inch video tape recorders and players, including the Digital Betacam format. In 1985, Sony launched their Handycam products and the Video8 format. Video8 and the follow-on hi-band Hi8 format became popular in the consumer camcorder market. In 1987 Sony launched the 4 mm DAT or Digital Audio Tape as a new digital audio tape standard. Sony held a patent for its proprietary Trinitron until 1996. Sony introduced the Triluminos Display, the company's proprietary color reproduction enhancing technology, in 2004, featured in the world's first LED-backlit LCD televisions. It was widely used in other Sony's products as well, including computer monitors, laptops, and smartphones. In 2013, Sony released a new line of televisions with an improved version of the technology, which incorporated quantum dots in the backlight system. It was the first commercial use of quantum dots. In 2012, the company revealed a prototype of an ultrafine RGB LED display, which it calls the Crystal LED Display. Sony used the Compact Cassette format in many of its tape recorders and players, including the Walkman, the world's first portable music player. Sony introduced the MiniDisc format in 1992 as an alternative to Philips DCC or Digital Compact Cassette and as a successor to the Compact Cassette. Since the introduction of MiniDisc, Sony has attempted to promote its own audio compression technologies under the ATRAC brand, against the more widely used MP3. Until late 2004, Sony's Network Walkman line of digital portable music players did not support the MP3 standard natively. In 2004, Sony built upon the MiniDisc format by releasing Hi-MD. Hi-MD allows the playback and recording of audio on newly introduced 1 GB Hi-MD discs in addition to playback and recording on regular MiniDiscs. In addition to saving audio on the discs, Hi-MD allows the storage of computer files such as documents, videos and photos. In 1993, Sony challenged the industry standard Dolby Digital 5.1 surround sound format with a newer and more advanced proprietary motion picture digital audio format called SDDS (Sony Dynamic Digital Sound). This format employed eight channels (7.1) of audio opposed to just six used in Dolby Digital 5.1 at the time. Ultimately, SDDS has been vastly overshadowed by the preferred DTS (Digital Theatre System) and Dolby Digital standards in the motion picture industry. SDDS was solely developed for use in the theatre circuit; Sony never intended to develop a home theatre version of SDDS. Sony and Philips jointly developed the Sony-Philips digital interface format (S/PDIF) and the high-fidelity audio system SACD. The latter became entrenched in a format war with DVD-Audio. Still, neither gained a major foothold with the general public. CDs had been preferred by consumers because of the ubiquitous presence of CD drives in consumer devices until the early 2000s when the iPod and streaming services became available. In 2015, Sony introduced LDAC, a proprietary audio coding technology which allows streaming high-resolution audio over Bluetooth connections at up to 990 kbit/s at 32 bit/96 kHz. Sony also contributed it as part of the Android Open Source Project starting from Android 8.0 "Oreo", enabling every OEM to integrate this standard into their own Android devices freely. However the decoder library is proprietary, so receiving devices require licenses. On 17 September 2019, the Japan Audio Society (JAS) certified LDAC with their Hi-Res Audio Wireless certification. Currently the only codecs with the Hi-Res Audio Wireless certification are LDAC and LHDC, another competing standard. Sony demonstrated an optical digital audio disc in 1977 and soon joined hands with Philips, another major contender for the storage technology, to establish a worldwide standard. In 1983, the two companies jointly announced the Compact Disc (CD). In 1984, Sony launched the Discman series, an expansion of the Walkman brand to portable CD players. Sony began to improve performance and capacity of the novel format. It launched write-once optical discs (WO) and magneto-optical discs which were around 125MB size for the specific use of archival data storage, in 1986 and 1988 respectively. In the early 1990s, two high-density optical storage standards were being developed: one was the MultiMedia Compact Disc (MMCD), backed by Philips and Sony, and the other was the Super Density Disc (SD), supported by Toshiba and many others. Philips and Sony abandoned their MMCD format and agreed upon Toshiba's SD format with only one modification. The unified disc format was called DVD and was introduced in 1997. Sony was one of the leading developers of the Blu-ray optical disc format, the newest standard for disc-based content delivery. The first Blu-ray players became commercially available in 2006. The format emerged as the standard for HD media over the competing format, Toshiba's HD DVD, after a two-year-long high-definition optical disc format war. Sony's laser communication devices for small satellites rely on the technologies developed for the company's optical disc products. In 1983, Sony introduced 90 mm micro diskettes, better known as 3.5-inch (89 mm) floppy disks, which it had developed at a time when there were 4" floppy disks, and many variations from different companies, to replace the then on-going 5.25" floppy disks. Sony had great success and the format became dominant. 3.5" floppy disks gradually became obsolete as they were replaced by current media formats. Sony held more than a 70 percent share of the market when it decided to pull the plug on the format in 2010. Sony still develops magnetic tape storage technologies along with IBM, and are one of only two manufacturers of Linear Tape-Open (LTO) cartridges. In 1998, Sony launched the Memory Stick format, the flash memory cards for use in Sony lines of digital cameras and portable music players. It has seen little support outside of Sony's own products, with Secure Digital cards (SD) commanding considerably greater popularity. Sony has made updates to the Memory Stick format with Memory Stick Duo and Memory Stick Micro. The company has also released USB flash drive products, branded under the Micro Vault line. Sony introduced FeliCa, a contactless IC card technology primarily used in contactless payment, as a result of the company's joint development and commercialization of Near-Field Communication (NFC) with Philips. The standard is largely offered in two forms, either chips embedded in smartphones or plastic cards with chips embedded in them. Sony plans to implement this technology in train systems across Asia. In 2019, Sony launched the ELTRES, the company's proprietary low-power wide-area wireless communication (LPWAN) standard. Until 1991, Sony had little direct involvement with the video game industry. The company supplied components for other consoles, such as the sound chip for the Super Famicom from Nintendo, and operated a video game studio, Sony Imagesoft. As part of a joint project between Nintendo and Sony that began as early as 1988, the two companies worked to create a CD-ROM version of the Super Famicom, though Nintendo denied the existence of the Sony deal as late as March 1991. At the Consumer Electronics Show in June 1991, Sony revealed a Super Famicom with a built-in CD-ROM drive, named the "Play Station" (also known as SNES-CD). However, a day after the announcement at CES, Nintendo announced that it would be breaking its partnership with Sony, opting to go with Philips instead but using the same technology. The deal was broken by Nintendo after they were unable to come to an agreement on how revenue would be split between the two companies. The breaking of the partnership infuriated Sony President Norio Ohga, who responded by appointing Kutaragi with the responsibility of developing the PlayStation project to rival Nintendo. At that time, negotiations were still on-going between Nintendo and Sony, with Nintendo offering Sony a "non-gaming role" regarding their new partnership with Philips. This proposal was swiftly rejected by Kutaragi who was facing increasing criticism over his work with regard to entering the video game industry from within Sony. Negotiations officially ended in May 1992 and in order to decide the fate of the PlayStation project, a meeting was held in June 1992, consisting of Sony President Ohga, PlayStation Head Kutaragi and several senior members of Sony's board. At the meeting, Kutaragi unveiled a proprietary CD-ROM-based system he had been working on which involved playing video games with 3D graphics to the board. Eventually, Sony President Ohga decided to retain the project after being reminded by Kutaragi of the humiliation he suffered from Nintendo. Nevertheless, due to strong opposition from a majority present at the meeting as well as widespread internal opposition to the project by the older generation of Sony executives, Kutaragi and his team had to be shifted from Sony's headquarters to Sony Music, a completely separate financial entity owned by Sony, so as to retain the project and maintain relationships with Philips for the MMCD development project (which helped lead to the creation of the DVD) In 2021, the WIPO's annual review of the World Intellectual Property Indicators report ranked Sony's as ninth in the world for the number of patent applications published under the PCT System. 1,793 patent applications were published by Sony during 2020. This position is up from their previous ranking as 13th in 2019 with 1,566 applications. Business units Sony offers a wide variety of product lines in many areas. At its peak, it was dubbed as a "corporate octopus", for its sprawling ventures from private insurance to chemicals to cosmetics to home shopping to a Tokyo-based French food joint, in addition its core businesses such as electronics and entertainment. Even after it has unwound many business units including Sony Chemicals and Vaio PC, Sony still runs diverse businesses. As of 2020, Sony is organized into the following business segments: Game & Network Services (G&NS), Music, Pictures, Electronics Products & Solutions (EP&S), Imaging & Sensing Solutions (I&SS), Financial Services, and Others. Usually, each business segment has a handful of corresponding intermediate holding companies under which all the related businesses are folded into, such as Columbia Records being part of Sony Music Group, a subsidiary and, at the same time, a holding company for Sony's music businesses, along with SMEJ. Sony Corporation (Sony Electronics Corporation until 1 April 2021) is the electronics business unit of the Sony Group. It primarily conducts research and development (R&D), planning, designing, manufacturing and marketing for electronics products. Sony Global Manufacturing & Operations Corporation (SGMO) is a wholly owned subsidiary of Sony Corporation and responsible for managing manufacturing operations both in Japan and overseas, through its own factories as well as third party contract manufacturers. In 1979, Sony released the world's first portable music player, the Walkman, bundled with the MDL-3L2 headphones. This line fostered a fundamental change in music listening habits by allowing people to carry music with them and listen to music through lightweight headphones. Originally used to refer to portable audio cassette players, the Walkman brand has been widely adopted by the company to encompass its portable digital audio and video players as well as a line of former Sony Ericsson mobile phones. In the case of optical disc players, the Discman brand was used until the late 1990s. In 2025, a model TPS-L2 cassette Walkman from 1979 was included in Pirouette: Turning Points in Design, an exhibition at the Museum of Modern Art featuring "widely recognized design icons [...] highlighting pivotal moments in design history." In 1999 Sony's first portable digital audio players were introduced; one was a player using Memory Stick flash storage created by the Walkman division, and the other was a smaller pen-sized player with embedded flash storage created by the Vaio division; both accompanied with Sony's OpenMG copyright protection technology and PC software for music transfer. Sony continue to develop Walkman digital audio players, although it was unable to capture the large share and influence in the digital world as it did in the cassette era. Sony is a major audio products manufacturer and one of the active noise control technology leaders. Sony's high-end microphones and headphones for professional use are produced at Sony/Taiyo Corporation, a designated special subsidiary at which 67% of employees have a disability, in Ōita Prefecture, Japan. Sony partnered with Chery to provide OEM car audio for vehicles such as the Tiggo 8 and Tiggo 9, Ford to provide OEM audio for their vehicles such as the F-150, Fiesta, Focus, Mondeo and Taurus, Jaecoo with the Jaecoo 7, Omoda with their Omoda 5 and Omoda 9, Toyota with their Avensis and the Celica, Volkswagen with their Golf, Passat and also the Polo. A specialist Sony Xplod audio system was fitted to the Ford GTX1 supercar. Sony currently produces aftermarket car audio with their Mobile ES series. Sony produced the TV8-301, the world's first all-transistor television, in 1959. In 1968, the company introduced the Trinitron brand name for its lines of aperture grille cathode-ray tube televisions and afterwards computer monitors. Sony stopped production of Trinitron for most markets, but continued producing sets for markets such as Pakistan, Bangladesh and China. Sony discontinued its series of Trinitron computer monitors in 2005. The company discontinued the last Trinitron-based television set in the U.S. in early 2007. The end of Trinitron marked the end of Sony's analog television sets and monitors. Sony used the LCD WEGA name for its LCD TVs until summer 2005. The company then introduced the BRAVIA name. BRAVIA is an in-house brand owned by Sony which produces high-definition LCD televisions, projection TVs and front projectors, home cinemas and the BRAVIA home theatre range. All Sony high-definition flat-panel LCD televisions in North America have carried the logo for BRAVIA since 2005. In 2006, Sony lost its decades-long No.1 market share in the global television market. In November 2007, the Sony XEL-1, the first OLED television, was released and manufactured for two years. Later in 2013, Sony demonstrated the first 4K OLED television. As of 2012, Sony was the third-largest maker of televisions in the world and the business unit had been unprofitable for eight consecutive years. From 2011, Sony started restructuring of its loss-making television business, mainly by downsizing business units and outsourcing the manufacturing of display panels to the companies like Sharp Corporation, LG Display, and Samsung Electronics. In December 2011, Sony agreed to sell all stake in an LCD joint venture with Samsung Electronics (S-LCD) for about $940 million. On 28 March 2012, Sony and Sharp announced that they have agreed to further amend the joint venture agreement originally executed by the parties in July 2009, as amended in April 2011, for the establishment and operation of Sharp Display Products Corporation ("SDP"), a joint venture to produce and sell large-sized LCD panels and modules. The agreement was eventually terminated as Sony parted ways. Sony's small-sized LCD business subsidiary and medium-to-large-sized OLED display business unit were spun off and became part of Japan Display and JOLED, respectively. In 2017, Sony launched OLED televisions under the BRAVIA brand. Also, Sony has sold a range of tapes, discs, recorders and players for videocassette, DVD, and Blu-ray formats for decades. Sony offers a wide range of digital cameras. Its point-and-shoot models are branded Cyber-shot, while DSLRs and mirrorless models are branded Alpha, though Sony no longer makes DSLRs. It also produces action cameras and camcorders, with the company's cinema-grade products being sold under the CineAlta name. Sony demonstrated a prototype of the Sony Mavica in 1981 and released it for the consumer market in 1988. The first Cyber-shot was introduced in 1996. Sony's market share of the digital camera market fell from a high of 20% to 9% by 2005. Sony entered the market for digital single-lens reflex cameras in 2006 when it acquired the camera business of Konica Minolta. Sony rebranded the company's line of cameras as its Alpha line. Sony is the world's third largest manufacturer of the cameras, behind Canon and Nikon respectively. In 2010, Sony introduced their first mirrorless interchangeable-lens cameras, which were the NEX-3 and the NEX-5. They also started a new lens mount system, which was the E-mount. There were quite a few NEX models out there, when Sony decided to melt the NEX series into the Alpha series. The first Alpha MILC was the α3000, which was introduced in August 2013. It was followed by the Full-Frame α7 and α7R in October, then the successors of the NEX-5, the NEX-6 and NEX-7, the α5000 and the α6000 in 2014. The α6000 became the most popular MILC ever and Sony became the largest MILC manufacturer. Sony produced computers (SMC-777 [jp] personal computer, MSX home computers and NEWS workstations) during the 1980s. The company withdrew from the computer business around 1990. Sony entered again into the global computer market under the new VAIO brand, began in 1996. Short for "Video Audio Integrated Operation", the line was the first computer brand to highlight visual-audio features. Sony faced considerable controversy when some of its laptop batteries exploded and caught fire in 2006, resulting in the largest computer-related recall to that point in history. In a bid to join the tablet computer market, the company launched its Sony Tablet line of Android tablets in 2011. Since 2012, Sony's Android products have been marketed under the Xperia brand used for its smartphones. On 4 February 2014, Sony announced that it would sell its VAIO PC business due to poor sales and Japanese company Japan Industrial Partners (JIP) will purchase the VAIO brand, with the deal finalized by the end of March 2014. As of 2018, Sony maintained a 5% stake in the new, independent company. In the 1990s, Sony was contracted to manufacture laptop computers for Apple and Dell. The Raspberry Pi Foundation delegates the manufacture of its single-board computers to Sony. Most Raspberry Pi computers are made at Sony UK Technology Centre in Pencoed, Wales, UK. Sony has targeted medical, healthcare and biotechnology business as a growth sector in the future. The company acquired iCyt Mission Technology, Inc. (renamed Sony Biotechnology Inc. in 2012), a manufacturer of flow cytometers, in 2010 and Micronics, Inc., a developer of microfluidics-based diagnostic tools, in 2011. In 2012, Sony announced that it would acquire all shares of So-net Entertainment Corporation, the largest shareholder of M3, Inc., an operator of portal sites (m3.com, MR-kun, MDLinx and MEDI:GATE) for healthcare professionals. On 28 September 2012, Olympus and Sony announced that the two companies will establish a joint venture to develop new surgical endoscopes with 4K resolution (or higher) and 3D capability. Sony Olympus Medical Solutions Inc. (Sony 51%, Olympus 49%) was established on 16 April 2013. On 28 February 2014, Sony, M3 and Illumina established a joint venture called P5, Inc. to provide a genome analysis service for research institutions and enterprises in Japan. In 2000, Sony was a marginal player in the mobile phone market with a share of less than 1 percent. In 2001, Sony entered into a joint venture with Swedish telecommunications company Ericsson, forming Sony Ericsson Mobile Communications. Initial sales were rocky, and the company posted losses in 2001 and 2002. However, Sony Ericsson reached a profit in 2003. The company distinguished itself with multimedia-capable mobile phones, which included features such as cameras. These were unusual at the time. Despite their innovations, Sony Ericsson faced intense competition from Apple's iPhone, which was released in 2007. From 2008 to 2010, amid a global recession, Sony Ericsson slashed its workforce by several thousand. In 2009, Sony Ericsson was the fourth-largest mobile phone manufacturer in the world (after Nokia, Samsung and LG). By 2010, its market share had fallen to sixth place. Sony acquired Ericsson's share of the venture in 2012 for over US$1 billion. Sony Mobile focuses exclusively on the smartphone market under the Xperia brand. In 2013, Sony contributed to around two percent of the mobile phone market with 37 million mobile phones sold. Sony Mobile's sales reached a peak in 2014 with 40 million handsets, the volume has since decreased. Sony shipped 13.5 million phones in 2017, 6.5 million in 2018, and 2.9 million handsets in FY 2020. Since the late 1990s, Sony has released numerous consumer robots, including dog-shaped robots called AIBO, a music playing robot called Rolly, and a humanoid robot called QRIO. Despite being a pioneer in the field, Sony had ceased robotics-related operations for 10 years due to financial difficulties, until it decided to revive them in 2016. In 2015, Sony partnered with an autonomous driving startup ZMP INC. to establish an aerial surveillance and reconnaissance drone manufacturer named Aerosense. At the CES 2021, Sony unveiled a drone with the brand Airpeak, the smallest of its kind that can incorporate a Sony Alpha camera according to the company, entering the drone business on its own for the first time. In 2019, as part of the London Design Festival, Sony Design showcased Affinity in Autonomy, a conceptual environmental art installation in the Prince Consort Gallery of the Victoria and Albert Museum that represented the company's vision of the future of AI and Robotics. Sony traces its roots in the semiconductor business back to 1954, when it became the first Japanese company to commercialize the transistor, invented and licensed by Bell Labs, whilst some of the biggest and well-established names in Japan at the time like Toshiba and Mitsubishi Electric initially stuck with vacuum tubes they had been thriving on; despite being an expert on the vacuum tube himself, Ibuka saw potential of the novel technology and had Morita negotiate the terms for licensing, making Sony into one of the earliest and the youngest licensees of the transistor, together with Texas Instruments. In 1957, Sony employee Leo Esaki and his colleagues invented a tunnel diode (usually referred to as Esaki diode) by which they discovered the quantum tunneling effect in solids, for which Esaki received the Nobel prize in Physics in 1973. Sony has commanded a dominant share in the charge-coupled device market. As of 2020, Sony is the world's largest manufacturer of CMOS image sensors as its chips are widely used in digital cameras, tablet computers, smartphones, drones and more recently, self-driving systems in automobiles. As of 2020, the company, through its chip business arm Sony Semiconductor Solutions, designs, manufactures, and sells a wide range of semiconductors and electronic components, including image sensors (HAD CCD, Exmor), image processors (BIONZ), laser diodes, system LSIs, mixed-signal LSIs, emerging memory storage, emerging displays (microLED, microOLED, and holographic display), multi-functional microcomputer (SPRESENSE), etc. In 2020, Sony has launched the first intelligent vision sensors with AI edge computing capabilies. Sony Interactive Entertainment (formerly Sony Computer Entertainment) is most notable for producing PlayStation consoles. The line grew out of a failed partnership with Nintendo. Originally, Nintendo requested Sony to develop an add-on for its Super Nintendo Entertainment System that would play CD-ROMs. In 1991 Sony announced the add-on, as well as a dedicated console known as the "Play Station". However, a disagreement over software licensing for the console caused the partnership to fall through. Sony then continued the project independently. Launched in 1994, the first PlayStation gained 61% of global console sales and broke Nintendo's long-standing lead in the market. Sony followed up with the PlayStation 2 in 2000, which was even more successful. The console has become the most successful of all time, selling over 150 million units as of 2011[update]. Sony released the PlayStation 3, a high-definition console, in 2006. It was the first console to use the Blu-ray format, and was considerably more expensive than the competitors Xbox 360 and Wii due to the Cell processor. Early on, poor sales performance resulted in significant losses for the company, pushing it to sell the console at a loss. The PlayStation 3 sold generally more poorly than its competitors in the early years of its release but managed to overtake the Xbox 360 in global sales later on. It later introduced the PlayStation Move, an accessory that allows players to control video games using motion gestures. Sony extended the brand to the portable games market in 2004 with the PlayStation Portable (PSP). The console has sold reasonably, but has taken a second place to a rival handheld, the Nintendo DS. Sony developed the Universal Media Disc (UMD) optical disc medium for use on the PlayStation Portable. Early on, the format was used for movies, but it has since lost major studio support. Sony released a disc-less version of its PlayStation Portable, the PSP Go, in 2009. The company went on to release its second portable video game system, PlayStation Vita, in 2011 and 2012. Sony launched its fourth console, the PlayStation 4, on 15 November 2013, which as of 31 December 2017 has sold 73.6 million units globally. On 18 March 2014, at GDC, president of SCE Worldwide Studios Shuhei Yoshida announced their new virtual reality technology dubbed Project Morpheus, and later named PlayStation VR, for PlayStation 4. The headset brought VR gaming and non-gaming software to the company's console. According to a report released by Houston-based patent consulting firm LexInnova in May 2015, Sony is leading the virtual reality patent race. According to the firm's analysis of nearly 12,000 patents or patent applications, Sony has 366 virtual reality patents or patent applications. PlayStation VR was released worldwide on 13 October 2016. On 31 March 2019, the successor to the PlayStation 4 was announced and on 12 November 2020, the PlayStation 5 was released in North America, Australia, New Zealand, Japan, South Korea, and Singapore. The console was launched in Indonesia on 22 January 2021. Upon completion of the fiscal quarter, Sony sold 4.5 million PlayStation 5 consoles, keeping pace with the best-selling console of all time, the PlayStation 2. Sony Entertainment has two divisions: Sony Pictures Entertainment, Sony Music Group (Sony Music Entertainment, Sony Music Publishing). Sony USA previously owned and operated Sony Trans Com: a technology business that provided in-flight entertainment programming as well as video and audio playback equipment for the airline industry. Sony had purchased the business from Sundstrand Corp. in 1989 and subsequently sold it to Rockwell Collins in 2000. In 2012, Sony rolled most of its consumer content services (including video, music and gaming) into the Sony Entertainment Network, the predecessor of PlayStation Network. Sony Pictures Entertainment Inc. (SPE) is the television and film production/distribution unit of Sony. With 12.5% box office market share in 2011, the company was ranked third among movie studios. Its group sales in 2010 were US$7.2 billion. The company has produced many notable movie franchises, including Spider-Man, The Karate Kid and Men in Black. It has also produced the popular television game shows Jeopardy! and Wheel of Fortune. Sony entered the television and film production market when it acquired Columbia Pictures Entertainment in 1989 for $3.4 billion. Columbia lives on in the Sony Pictures Motion Picture Group, a division of SPE which in turn owns Columbia Pictures and TriStar Pictures among other film production and distribution companies such as Screen Gems, Sony Pictures Classics, Sony Pictures Home Entertainment. SPE's television division is known as Sony Pictures Television. For the first several years of its existence, Sony Pictures Entertainment performed poorly, leading many to suspect the company would sell off the division. In 2006, Sony started using ARccOS Protection on some of their film DVDs, but later issued a recall. In late 2014, Sony Pictures became the target of a hack attack from a clandestine group called Guardians of Peace, weeks before releasing the anti-North Korean comedy film The Interview. In February 2024, Sony entered into an agreement with Disney under which Sony Pictures Home Entertainment Corporation of Japan will handle the release of Disney products on DVD and Blu-ray on a licensing model, as well as production on physical media. Sony will market, sell and distribute new Disney releases and catalog films on DVD, Blu-ray and 4K Ultra DVD through Canadian and American retailers and distributors. Sony Music Entertainment (also known as SME or Sony Music) is the largest global recorded music company of the "big three" record companies and is controlled by Sony Corporation of America, the United States subsidiary of Sony. In one of its largest-ever acquisitions, Sony purchased CBS Record Group in 1988 for US$2 billion. In the process, Sony partnered and gained the rights to the ATV catalogue of Michael Jackson, considered by the Guinness Book of World Records to be the most successful entertainer of all time. The acquisition of CBS Records provided the foundation for the formation of Sony Music Entertainment, which Sony established in 1991. In 1968, Sony and CBS Records had formed a 50:50 joint-venture CBS/Sony Records, later renamed CBS/Sony Group, in Japan. When CBS Records was acquired, a 50% stake in CBS/Sony Group owned by CBS was also transferred to Sony. In March 1988, four wholly owned subsidiaries were folded into CBS/Sony Group and the company was renamed as Sony Music Entertainment Japan (SMEJ). It operates independently of Sony Music as it is directly owned by Japanese Sony. In 2004, Sony entered into a joint venture with Bertelsmann AG, merging Sony Music Entertainment with Bertelsmann Music Group to create Sony BMG. In 2005, Sony BMG faced a copy protection scandal, because its music CDs had installed malware on users' computers that was posing a security risk to affected customers. In 2007, the company acquired Famous Music for US$370 million, gaining the rights to the catalogues of Eminem and Akon, among others. Sony bought out Bertelsmann's share in Sony BMG and formed a new Sony Music Entertainment in 2008. Since then, the company has undergone management changes. Sony purchased digital music recognition company Gracenote for US$260 million in 2008. Tribune Media Company acquired Gracenote from Sony in 2014 for $170 million. Besides its record label, Sony operates other music businesses. In 1995, Sony merged its publisher with Michael Jackson's ATV Music Publishing, forming Sony/ATV Music Publishing. At the time, the publishing company was the second largest of its kind in the world. The company owns the publishing rights to over 4 million compositions, including The Beatles' Lennon–McCartney catalogue, Bob Dylan, Eminem, Lady Gaga, Sam Smith, Ed Sheeran, and Taylor Swift. In 2012, Sony/ATV acquired a majority stake in EMI Music Publishing, becoming the world's largest music publishing company. In 2018, Sony bought the rest of the shares in the publisher, making it a wholly owned subsidiary. Since 2016, Sony owns all of Sony/ATV. Sony's entering into the Japanese animation, or anime, business happened in 1995 when its Sony Music Entertainment Japan (SMEJ) division established Aniplex as its subsidiary managing creative productions, which founded A-1 Pictures, the first anime studio of Sony, ten years later. Since then, through group-wide and international ventures, Sony has solidified its position in the industry, elevating the business to what is called the "fourth pillar of its entertainment portfolio" according to The Nikkei. The anime business operations of Sony are scattered around the group, mainly in its Pictures and Music units, as follows: SMEJ's notable related businesses include Aniplex and its subsidiaries CloverWorks and A-1 Pictures; Aniplex and U.S.-headquartered Sony Pictures co-own U.S.-based anime distribution company Crunchyroll, which since 2022, has become the successor company to Funimation, which it acquired in 2017 and included subsidiaries such as Wakanim (absorbing into Crunchyroll itself) and Madman Anime (to be rebranded as Crunchyroll Pty. Ltd.) In December 2020, Funimation announced that it would buy AT&T's animation business Crunchyroll for $1.175 billion, which would help the company to compete more globally with entertainment giants such as Netflix. This acquisition was completed in August 2021. Sony Financial Group is a holding company for Sony's financial services business which includes Sony Life (in Japan and the Philippines), Sony Assurance, Sony Bank, etc. The unit proved to be the most profitable of Sony's businesses in FY 2005, earning $1.7 billion in profit. Sony Financial's low fees have aided the unit's popularity while threatening Sony's premium brand name. A company behind the commercialization of lithium-ion battery, Sony had been exploring the possibility to manufacture the batteries for electric vehicles. In 2014, Sony participated within NRG Energy eVgo Ready for Electric Vehicle (REV) program, for EV charging parking lots. However, the company then decided to sell its lithium-ion battery business to Murata Manufacturing in 2016. In 2015, Sony invested $842,000 in ZMP INC., drawing speculations that it is contemplating developing self-driving cars. In January 2020, Sony unveiled a concept electric car at the Consumer Electronics Show, named Vision-S, designed in collaboration with components manufacturer Magna International. At the occasion, Sony also stated its goal of developing technology for the automotive sector, especially concerning autonomous driving, sensors, and in-car entertainment. In 2022, Sony Group and Honda launched a joint venture for their electric vehicle partnership, Sony Honda Mobility (SHM), which would deliver its first electric vehicles by 2026 and sell them online, starting in the United States and Japan. The joint venture announced their new "Afeela" brand and its first prototype model at the CES 2023. Corporate information Sony is a kabushiki kaisha (joint stock company) listed on the Tokyo Stock Exchange in Japan with American depositary receipts listed on New York Stock Exchange. As of 31 March 2023[update], the largest shareholders of Sony are as follows: The key trends for Sony are (as of the financial year ending March 31): As of January 2024, Sony, one of the largest Japanese companies by market capitalization and operating profit, was valued at over $112 billion. At the same period, it was also recognized as the most cash-rich Japanese company, with its net cash reserves of ¥1.8 trillion. The company was immensely profitable throughout the 1990s and early 2000s in part because of the success of its new PlayStation line. The company encountered financial difficulty in the mid- to late-2000s due to several factors: the Great Recession, increased competition for PlayStation, and the 2011 Tōhoku earthquake and tsunami. The company faced three consecutive years of losses leading up to 2011. While noting the negative effects of intervening circumstances such as natural disasters and fluctuating currency exchange rates, the Financial Times criticized the company for its "lack of resilience" and "inability to gauge the economy," voicing skepticism about Sony's revitalization efforts, given a lack of tangible results. In September 2000 Sony had a market capitalization of $100 billion; but by December 2011 it had plunged to $18 billion, reflecting falling prospects for Sony but also reflecting grossly inflated share prices of the 'dot-com bubble' years. Net worth, as measured by stockholder equity, has steadily grown from $17.9 billion in March 2002 to $35.6 billion through December 2011. Earnings yield (inverse of the price to earnings ratio) has never been more than 5% and usually much less; thus Sony has always traded in over-priced ranges with the exception of the 2009 market bottom. On 9 December 2008, Sony announced that it would be cutting 8,000 jobs, dropping 8,000 contractors and reducing its global manufacturing sites by 10% to save $1.1 billion per year. In April 2012, Sony announced that it would reduce its workforce by 10,000 (6% of its employee base) as part of CEO Kaz Hirai's effort to get the company back into the black. This came after a loss of 520 billion yen (roughly US$6.36 billion) for fiscal 2012, the worst since the company was founded. Accumulation loss for the past four years was 919.32 billion-yen. Sony planned to increase its marketing expenses by 30% in 2012. 1,000 of the jobs cut came from the company's mobile phone unit's workforce, 700 jobs being cut in the 2012–2013 fiscal year and the remaining 300 in the following fiscal year. Sony had revenues of ¥6.493 trillion in 2012 and maintained large reserves of cash, with ¥895 billion on hand as of 2012. In May 2012, Sony's market capitalization was valued at about $15 billion. In January 2013, Sony announced it was selling its US headquarters building for $1.1 billion to a consortium led by real estate developer The Chetrit Group. On 28 January 2014, Moody's Investors Services dropped Sony's credit rating to Ba1—"judged to have speculative elements and a significant credit risk"—saying that the company's "profitability is likely to remain weak and volatile." On 6 February 2014, Sony announced it would trim as many as 5,000 jobs as it attempts to sell its PC business and focus on mobile and tablets. In 2014, Sony South Africa closed its TV, Hi-Fi and camera divisions with the purpose of reconsidering its local distribution model and, in 2017, it returned facilitated by Premium Brand Distributors (Pty) Ltd. In November 2018, Sony posted its earning report for the second quarter showing it has lost about US$480 million in the mobile phone division, prompting another round of downsizing in the unit, including the closure of a manufacturing plant and halving of its workforce. In November 2025, Israeli business media outlets, including Globes, reported that the Japanese company Sony plans to cease its telecommunications chip development activities in Israel. Criticism & controversies Over the years, Sony has faced a number of allegations and criticism pertaining to their corporate behavior, often leading to legal proceedings and customer dissatisfaction. In August 2000, then Sony Pictures Entertainment U.S. senior vice president Steve Heckler was quoted saying "The industry will take whatever steps it needs to protect itself and protect its revenue streams ...". Sony then worked on a DRM system that works like a rootkit in order to enforce its copyright claims upon users of music CDs. With respect to Sony's gaming consoles, subsequent updates are released to the said consoles, many of which strip the user of some of the originally advertised features in order to save the company some licensing fees or protect itself from the modding community. On April 1, 2010, Sony released a patch for the PS3 that would remove OtherOS from being installed onto the system after hackers were looking for ways to exploit OtherOS in order to run homebrew software. Then on January 12, 2011, Sony filled lawsuits against geohot and fail0verflow for their efforts on exploiting the PS3. In December 2023, Sony announced that it will remove the Discovery app and its content, even if previously paid for, from its gaming consoles. In November 2025, a collaborative decision was made by Sony Semiconductor Israel and the headquarters of Sony Corporation in Japan, stating that Sony Israel will detach from Sony Corporation and will recommence its operations as an independent entity under its original name, Altair Semiconductor. In December 2025, Texas Attorney General Ken Paxton filed a lawsuit against Sony and four other smart TV manufacturers, alleging that the companies were illegally "spying on Texans by secretly recording what consumers watch in their own homes" using automated content recognition (ACR) technology. In November 2011, Sony was ranked ninth (jointly with Panasonic) in Greenpeace's Guide to Greener Electronics. This chart grades major electronics companies on their environmental work. The company scored 3.6/10, incurring a penalty point for comments it has made in opposition to energy efficiency standards in California. It also risks a further penalty point in future editions for being a member of trade associations that have commented against energy efficiency standards. Together with Philips, Sony receives the highest score for energy policy advocacy after calling on the EU to adopt an unconditional 30% reduction target for greenhouse gas emissions by 2020. Meanwhile, it receives full marks for the efficiency of its products. In June 2007, Sony ranked 14th on the Greenpeace guide. Sony fell from its earlier 11th-place ranking due to Greenpeace's claims that Sony had double standards in their waste policies. As of May 2018[update] Greenpeace's 2017 Guide to Greener Electronics rated Sony approximately in the middle among electronics manufacturers with a grade of D+. Since 1976, Sony has had an Environmental Conference. Sony's policies address their effects on global warming, the environment, and resources. They are taking steps to reduce the amount of greenhouse gases that they put out as well as regulating the products they get from their suppliers in a process that they call "green procurement". Sony has said that they have signed on to have about 75 percent of their Sony Building running on geothermal power. The "Sony Take Back Recycling Program" allow consumers to recycle the electronics products that they buy from Sony by taking them to eCycle (Recycling) drop-off points around the U.S. The company has also developed a biobattery that runs on sugars and carbohydrates that works similarly to the way living creatures work. This is the most powerful small biobattery to date. In 2000, Sony faced criticism for a document entitled "NGO Strategy" that was leaked to the press. The document involved the company's surveillance of environmental activists in an attempt to plan how to counter their movements. It specifically mentioned environmental groups that were trying to pass laws that held electronics-producing companies responsible for the cleanup of the toxic chemicals contained in their merchandise. In 2007 an investigation launched in 2002 by the European Commission culminated in Sony, Fuji and Maxell receiving a total of 110 million US dollar fine for fixing professional videotape prices between 1999 and 2002 through regular meetings and other illegal contracts; at the time the three corporations shared a combined 85% control of the market. Sony's part of the fine was raised by a third for trying to obstruct the investigation by refusing to answer inquiries made by the EU officials and shredding of evidence during the multiple law-enforcement raids. During the year 2001 prior to the investigation Sony sold professional videotapes for a total of €115 million inside the EU. See also Notes References Further reading External links |
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Contents Extraterrestrial life Extraterrestrial life, or alien life (colloquially aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically or conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more, or far less, advanced than humans. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology. Speculation about inhabited worlds beyond Earth dates back to antiquity. Early Christian writers, including Augustine, discussed ideas from thinkers like Democritus and Epicurus about countless worlds in the vast universe. Pre-modern writers typically assumed extraterrestrial "worlds" were inhabited by living beings. William Vorilong, in the 15th century, acknowledged the possibility Jesus could have visited extraterrestrial worlds to redeem their inhabitants.: 26 In 1440, Nicholas of Cusa suggested Earth is a "brilliant star"; he theorized that all celestial bodies, even the Sun, could host life. Descartes wrote that there were no means to prove the stars were not inhabited by "intelligent creatures", but their existence was a matter of speculation.: 67 In comparison to the life-abundant Earth, the vast majority of intrasolar and extrasolar planets and moons have harsh surface conditions and disparate atmospheric chemistry, or lack an atmosphere. However, there are many extreme and chemically harsh ecosystems on Earth that do support forms of life and are often hypothesized to be the origin of life on Earth. Examples include life surrounding hydrothermal vents, acidic hot springs, and volcanic lakes, as well as halophiles and the deep biosphere. Since the mid-20th century, researchers have searched for extraterrestrial life and intelligence. Solar system studies focus on Venus, Mars, Europa, and Titan, while exoplanet discoveries now total 6,022 confirmed planets in 4,490 systems as of October 2025. Depending on the category of search, methods range from analysis of telescope and specimen data to radios used to detect and transmit interstellar communication. Interstellar travel remains largely hypothetical, with only the Voyager 1 and Voyager 2 probes confirmed to have entered the interstellar medium. The concept of extraterrestrial life, especially intelligent life, has greatly influenced culture and fiction. A key debate centers on contacting extraterrestrial intelligence: some advocate active attempts, while others warn it could be risky, given human history of exploiting other societies. Context Initially, after the Big Bang, the universe was too hot to allow life. It is estimated that the temperature of the universe was around 10 billion Kelvin at the one-second mark. Roughly 15 million years later, it cooled to temperate levels, though the elements of organic life were yet nonexistent. The only freely available elements at that point were hydrogen and helium. Carbon and oxygen (and later, water) would not appear until 50 million years later, created through stellar fusion. At that point, the difficulty for life to appear was not the temperature, but the scarcity of free heavy elements. Planetary systems emerged, and the first organic compounds may have formed in the protoplanetary disk of dust grains that would eventually create rocky planets like Earth. Although Earth was in a molten state after its birth and may have burned any organics that fell on it, it would have been more receptive once it cooled down. Once the right conditions on Earth were met, life started by a chemical process known as abiogenesis. Alternatively, life may have formed less frequently, then spread—by meteoroids, for example—between habitable planets in a process called panspermia. During most of its stellar evolution, stars combine hydrogen nuclei to make helium nuclei by stellar fusion, and the comparatively lighter weight of helium allows the star to release the extra energy. The process continues until the star uses all of its available fuel, with the speed of consumption being related to the size of the star. During its last stages, stars start combining helium nuclei to form carbon nuclei. The larger stars can further combine carbon nuclei to create oxygen and silicon, oxygen into neon and sulfur, and so on until iron. Ultimately, the star blows much of its content back into the stellar medium, where it would join clouds that would eventually become new generations of stars and planets. Many of those materials are the raw components of life on Earth. As this process takes place in all the universe, said materials are ubiquitous in the cosmos and not a rarity from the Solar System. Earth is a planet in the Solar System, a planetary system formed by a star at the center, the Sun, and the objects that orbit it: other planets, moons, asteroids, and comets. The sun is part of the Milky Way, a galaxy. The Milky Way is part of the Local Group, a galaxy group that is in turn part of the Laniakea Supercluster. The universe is composed of all similar structures in existence. The immense distances between celestial objects are a difficulty for studying extraterrestrial life. So far, humans have only set foot on the Moon and sent robotic probes to other planets and moons in the Solar System. Although probes can withstand conditions that may be lethal to humans, the distances cause time delays: the New Horizons took nine years after launch to reach Pluto. No probe has ever reached extrasolar planetary systems. The Voyager 2 left the Solar System at a speed of 50,000 kilometers per hour; if it headed towards the Alpha Centauri system, the closest one to Earth at 4.4 light years, it would reach it in 100,000 years. Under current technology, such systems can only be studied by telescopes, which have limitations. It is estimated that dark matter has a larger amount of combined matter than stars and gas clouds, but as it plays no role in the stellar evolution of stars and planets, it is usually not taken into account by astrobiology. There is an area around a star, the circumstellar habitable zone or "Goldilocks zone", wherein water may be at the right temperature to exist in liquid form at a planetary surface. This area is neither too close to the star, where water would become steam, nor too far away, where water would be frozen as ice. However, although useful as an approximation, planetary habitability is complex and defined by several factors. Being in the habitable zone is not enough for a planet to be habitable, not even to actually have such liquid water. Venus is located in the solar system's habitable zone, but does not have liquid water because of the conditions of its atmosphere. Jovian planets or gas giants are not considered habitable even if they orbit close enough to their stars as hot Jupiters, due to crushing atmospheric pressures. The actual distances for the habitable zones vary according to the type of star, and even the solar activity of each specific star influences the local habitability. The type of star also defines the time the habitable zone will exist, as its presence and limits will change along with the star's stellar evolution. The Big Bang occurred 13.8 billion years ago, the Solar System was formed 4.6 billion years ago, and the first hominids appeared 6 million years ago. Life on other planets may have started, evolved, given birth to extraterrestrial intelligences, and perhaps even faced a planetary extinction event millions or billions of years ago. When considered from a cosmic perspective, the brief times of existence of Earth's species may suggest that extraterrestrial life may be equally fleeting under such a scale. During a period of about 7 million years, from about 10 to 17 million years after the Big Bang, the background temperature was between 373 and 273 K (100 and 0 °C; 212 and 32 °F), allowing the possibility of liquid water if any planets existed. Avi Loeb (2014) speculated that primitive life might in principle have appeared during this window, which he called "the Habitable Epoch of the Early Universe". Life on Earth is quite ubiquitous across the planet and has adapted over time to almost all the available environments in it, extremophiles and the deep biosphere thrive at even the most hostile ones. As a result, it is inferred that life in other celestial bodies may be equally adaptive. However, the origin of life is unrelated to its ease of adaptation and may have stricter requirements. A celestial body may not have any life on it, even if it were habitable. Likelihood of existence Life in the cosmos beyond Earth has been observed. The hypothesis of ubiquitous extraterrestrial life relies on three main ideas. The first one, the size of the universe, allows for plenty of planets to have a similar habitability to Earth, and the age of the universe gives enough time for a long process analog to the history of Earth to happen there. The second is that the substances that make life, such as carbon and water, are ubiquitous in the universe. The third is that the physical laws are universal, which means that the forces that would facilitate or prevent the existence of life would be the same ones as on Earth. According to this argument, made by scientists such as Carl Sagan and Stephen Hawking, it would be improbable for life not to exist somewhere else other than Earth. This argument is embodied in the Copernican principle, which states that Earth does not occupy a unique position in the Universe, and the mediocrity principle, which states that there is nothing special about life on Earth. Other authors consider instead that life in the cosmos, or at least multicellular life, may actually be rare. The Rare Earth hypothesis maintains that life on Earth is possible because of a series of factors that range from the location in the galaxy and the configuration of the Solar System to local characteristics of the planet, and that it is unlikely that another planet simultaneously meets all such requirements. The proponents of this hypothesis consider that very little evidence suggests the existence of extraterrestrial life and that, at this point, it is just a desired result and not a reasonable scientific explanation for any gathered data. In 1961, astronomer and astrophysicist Frank Drake devised the Drake equation as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence (SETI). The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The Drake equation is:: xix where: and Drake's proposed estimates are as follows, but numbers on the right side of the equation are agreed as speculative and open to substitution: 10,000 = 5 ⋅ 0.5 ⋅ 2 ⋅ 1 ⋅ 0.2 ⋅ 1 ⋅ 10,000 {\displaystyle 10{,}000=5\cdot 0.5\cdot 2\cdot 1\cdot 0.2\cdot 1\cdot 10{,}000} [better source needed] The Drake equation has proved controversial since, although it is written as a math equation, none of its values were known at the time. Although some values may eventually be measured, others are based on social sciences and are not knowable by their very nature. This does not allow one to make noteworthy conclusions from the equation. Based on observations from the Hubble Space Telescope, there are nearly 2 trillion galaxies in the observable universe. It is estimated that at least ten percent of all Sun-like stars have a system of planets. In other words, there are 6.25×1018 stars with planets orbiting them in the observable universe. Even if it is assumed that only one out of a billion of these stars has planets supporting life, there would be some 6.25 billion life-supporting planetary systems in the observable universe. A 2013 study based on results from the Kepler spacecraft estimated that the Milky Way contains at least as many planets as it does stars, resulting in 100–400 billion exoplanets. The Nebular hypothesis that explains the formation of the Solar System and other planetary systems would suggest that those can have several configurations, and not all of them may have rocky planets within the habitable zone. The apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilisations and the lack of evidence for such civilisations is known as the Fermi paradox. Dennis W. Sciama claimed that life's existence in the universe depends on various fundamental constants. Zhi-Wei Wang and Samuel L. Braunstein suggest that a random universe capable of supporting life is likely to be just barely able to do so, giving a potential explanation to the Fermi paradox. Biochemical basis If extraterrestrial life exists, it could range from simple microorganisms and multicellular organisms similar to animals or plants, to complex alien intelligences akin to humans. When scientists talk about extraterrestrial life, they consider all those types. Although it is possible that extraterrestrial life may have other configurations, scientists use the hierarchy of lifeforms from Earth for simplicity, as it is the only one known to exist. The first basic requirement for life is an environment with non-equilibrium thermodynamics, which means that the thermodynamic equilibrium must be broken by a source of energy. The traditional sources of energy in the cosmos are the stars, such as for life on Earth, which depends on the energy of the sun. However, there are other alternative energy sources, such as volcanoes, plate tectonics, and hydrothermal vents. There are ecosystems on Earth in deep areas of the ocean that do not receive sunlight, and take energy from black smokers instead. Magnetic fields and radioactivity have also been proposed as sources of energy, although they would be less efficient ones. Life on Earth requires water in a liquid state as a solvent in which biochemical reactions take place. It is highly unlikely that an abiogenesis process can start within a gaseous or solid medium: the atom speeds, either too fast or too slow, make it difficult for specific ones to meet and start chemical reactions. A liquid medium also allows the transport of nutrients and substances required for metabolism. Sufficient quantities of carbon and other elements, along with water, might enable the formation of living organisms on terrestrial planets with a chemical make-up and temperature range similar to that of Earth. Life based on ammonia rather than water has been suggested as an alternative, though this solvent appears less suitable than water. It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbon, such as methane, ethane or propane. Another unknown aspect of potential extraterrestrial life would be the chemical elements that would compose it. Life on Earth is largely composed of carbon, but there could be other hypothetical types of biochemistry. A replacement for carbon would need to be able to create complex molecules, store information required for evolution, and be freely available in the medium. To create DNA, RNA, or a close analog, such an element should be able to bind its atoms with many others, creating complex and stable molecules. It should be able to create at least three covalent bonds: two for making long strings and at least a third to add new links and allow for diverse information. Only nine elements meet this requirement: boron, nitrogen, phosphorus, arsenic, antimony (three bonds), carbon, silicon, germanium and tin (four bonds). As for abundance, carbon, nitrogen, and silicon are the most abundant ones in the universe, far more than the others. On Earth's crust the most abundant of those elements is silicon, in the Hydrosphere it is carbon and in the atmosphere, it is carbon and nitrogen. Silicon, however, has disadvantages over carbon. The molecules formed with silicon atoms are less stable, and more vulnerable to acids, oxygen, and light. An ecosystem of silicon-based lifeforms would require very low temperatures, high atmospheric pressure, an atmosphere devoid of oxygen, and a solvent other than water. The low temperatures required would add an extra problem, the difficulty to kickstart a process of abiogenesis to create life in the first place. Norman Horowitz, head of the Jet Propulsion Laboratory bioscience section for the Mariner and Viking missions from 1965 to 1976 considered that the great versatility of the carbon atom makes it the element most likely to provide solutions, even exotic solutions, to the problems of survival of life on other planets. However, he also considered that the conditions found on Mars were incompatible with carbon based life. Even if extraterrestrial life is based on carbon and uses water as a solvent, like Earth life, it may still have a radically different biochemistry. Life is generally considered to be a product of natural selection. It has been proposed that to undergo natural selection a living entity must have the capacity to replicate itself, the capacity to avoid damage/decay, and the capacity to acquire and process resources in support of the first two capacities. Life on Earth may have started with an RNA world and later evolved to its current form, where some of the RNA tasks were transferred to DNA and proteins. Extraterrestrial life may still be stuck using RNA, or evolve into other configurations. It is unclear if our biochemistry is the most efficient one that could be generated, or which elements would follow a similar pattern. However, it is likely that, even if cells had a different composition to those from Earth, they would still have a cell membrane. Life on Earth jumped from prokaryotes to eukaryotes and from unicellular organisms to multicellular organisms through evolution. So far no alternative process to achieve such a result has been conceived, even if hypothetical. Evolution requires life to be divided into individual organisms, and no alternative organisation has been satisfactorily proposed either. At the basic level, membranes define the limit of a cell, between it and its environment, while remaining partially open to exchange energy and resources with it. The evolution from simple cells to eukaryotes, and from them to multicellular lifeforms, is not guaranteed. The Cambrian explosion took place thousands of millions of years after the origin of life, and its causes are not fully known yet. On the other hand, the jump to multicellularity took place several times, which suggests that it could be a case of convergent evolution, and so likely to take place on other planets as well. Palaeontologist Simon Conway Morris considers that convergent evolution would lead to kingdoms similar to our plants and animals, and that many features are likely to develop in alien animals as well, such as bilateral symmetry, limbs, digestive systems and heads with sensory organs. Scientists from the University of Oxford analysed it from the perspective of evolutionary theory and wrote in a study in the International Journal of Astrobiology that aliens may be similar to humans. The planetary context would also have an influence: a planet with higher gravity would have smaller animals, and other types of stars can lead to non-green photosynthesizers. The amount of energy available would also affect biodiversity, as an ecosystem sustained by black smokers or hydrothermal vents would have less energy available than those sustained by a star's light and heat, and so its lifeforms would not grow beyond a certain complexity. There is also research in assessing the capacity of life for developing intelligence. It has been suggested that this capacity arises with the number of potential niches a planet contains, and that the complexity of life itself is reflected in the information density of planetary environments, which in turn can be computed from its niches. It is common knowledge that the conditions on other planets in the solar system, in addition to the many galaxies outside of the Milky Way galaxy, are very harsh and seem to be too extreme to harbor any life. The environmental conditions on these planets can have intense UV radiation paired with extreme temperatures, lack of water, and much more that can lead to conditions that don't seem to favor the creation or maintenance of extraterrestrial life. However, there has been much historical evidence that some of the earliest and most basic forms of life on Earth originated in some extreme environments that seem unlikely to have harbored life at least at one point in Earth's history. Fossil evidence as well as many historical theories backed up by years of research and studies have marked environments like hydrothermal vents or acidic hot springs as some of the first places that life could have originated on Earth. These environments can be considered extreme when compared to the typical ecosystems that the majority of life on Earth now inhabit, as hydrothermal vents are scorching hot due to the magma escaping from the Earth's mantle and meeting the much colder oceanic water. Even in today's world, there can be a diverse population of bacteria found inhabiting the area surrounding these hydrothermal vents which can suggest that some form of life can be supported even in the harshest of environments like the other planets in the solar system. The aspects of these harsh environments that make them ideal for the origin of life on Earth, as well as the possibility of creation of life on other planets, is the chemical reactions forming spontaneously. For example, the hydrothermal vents found on the ocean floor are known to support many chemosynthetic processes which allow organisms to utilize energy through reduced chemical compounds that fix carbon. In return, these reactions will allow for organisms to live in relatively low oxygenated environments while maintaining enough energy to support themselves. The early Earth environment was reducing and therefore, these carbon fixing compounds were necessary for the survival and possible origin of life on Earth. With the little amount of information that scientists have found regarding the atmosphere on other planets in the Milky Way galaxy and beyond, the atmospheres are most likely reducing or with very low oxygen levels, especially when compared with Earth's atmosphere. If there were the necessary elements and ions on these planets, the same carbon fixing, reduced chemical compounds occurring around hydrothermal vents could also occur on these planets' surfaces and possibly result in the origin of extraterrestrial life. Planetary habitability in the Solar System The Solar System has a wide variety of planets, dwarf planets, and moons, and each one is studied for its potential to host life. Each one has its own specific conditions that may benefit or harm life. So far, the only lifeforms found are those from Earth. No extraterrestrial intelligence other than humans exists or has ever existed within the Solar System. Astrobiologist Mary Voytek points out that it would be unlikely to find large ecosystems, as they would have already been detected by now. The inner Solar System is likely devoid of life. However, Venus is still of interest to astrobiologists, as it is a terrestrial planet that was likely similar to Earth in its early stages and developed in a different way. There is a greenhouse effect, the surface is the hottest in the Solar System, sulfuric acid clouds, all surface liquid water is lost, and it has a thick carbon-dioxide atmosphere with huge pressure. Comparing both helps to understand the precise differences that lead to beneficial or harmful conditions for life. And despite the conditions against life on Venus, there are suspicions that microbial life-forms may still survive in high-altitude clouds. Mars is a cold and almost airless desert, inhospitable to life. However, recent studies revealed that water on Mars used to be quite abundant, forming rivers, lakes, and perhaps even oceans. Mars may have been habitable back then, and life on Mars may have been possible. But when the planetary core ceased to generate a magnetic field, solar winds removed the atmosphere and the planet became vulnerable to solar radiation. Ancient life-forms may still have left fossilised remains, and microbes may still survive deep underground. As mentioned, the gas giants and ice giants are unlikely to contain life. The most distant solar system bodies, found in the Kuiper Belt and outwards, are locked in permanent deep-freeze, but cannot be ruled out completely. Although the giant planets themselves are highly unlikely to have life, there is much hope to find it on moons orbiting these planets. Europa, from the Jovian system, has a subsurface ocean below a thick layer of ice. Ganymede and Callisto also have subsurface oceans, but life is less likely in them because water is sandwiched between layers of solid ice. Europa would have contact between the ocean and the rocky surface, which helps the chemical reactions. It may be difficult to dig so deep in order to study those oceans, though. Enceladus, a tiny moon of Saturn with another subsurface ocean, may not need to be dug, as it releases water to space in eruption columns. The space probe Cassini flew inside one of these, but could not make a full study because NASA did not expect this phenomenon and did not equip the probe to study ocean water. Still, Cassini detected complex organic molecules, salts, evidence of hydrothermal activity, hydrogen, and methane. Titan is the only celestial body in the Solar System besides Earth that has liquid bodies on the surface. It has rivers, lakes, and rain of hydrocarbons, methane, and ethane, and even a cycle similar to Earth's water cycle. This special context encourages speculations about lifeforms with different biochemistry, but the cold temperatures would make such chemistry take place at a very slow pace. Water is rock-solid on the surface, but Titan does have a subsurface water ocean like several other moons. However, it is of such a great depth that it would be very difficult to access it for study. Scientific search The science that searches and studies life in the universe, both on Earth and elsewhere, is called astrobiology. With the study of Earth's life, the only known form of life, astrobiology seeks to study how life starts and evolves and the requirements for its continuous existence. This helps to determine what to look for when searching for life in other celestial bodies. This is a complex area of study, and uses the combined perspectives of several scientific disciplines, such as astronomy, biology, chemistry, geology, oceanography, and atmospheric sciences. The scientific search for extraterrestrial life is being carried out both directly and indirectly. As of September 2017[update], 3,667 exoplanets in 2,747 systems have been identified, and other planets and moons in the Solar System hold the potential for hosting primitive life such as microorganisms. As of 8 February 2021, an updated status of studies considering the possible detection of lifeforms on Venus (via phosphine) and Mars (via methane) was reported. Scientists search for biosignatures within the Solar System by studying planetary surfaces and examining meteorites. Some claim to have identified evidence that microbial life has existed on Mars. In 1996, a controversial report stated that structures resembling nanobacteria were discovered in a meteorite, ALH84001, formed of rock ejected from Mars. Although all the unusual properties of the meteorite were eventually explained as the result of inorganic processes, the controversy over its discovery laid the groundwork for the development of astrobiology. An experiment on the two Viking Mars landers reported gas emissions from heated Martian soil samples that some scientists argue are consistent with the presence of living microorganisms. Lack of corroborating evidence from other experiments on the same samples suggests that a non-biological reaction is a more likely hypothesis. In February 2005 NASA scientists reported they may have found some evidence of extraterrestrial life on Mars. The two scientists, Carol Stoker and Larry Lemke of NASA's Ames Research Center, based their claim on methane signatures found in Mars's atmosphere resembling the methane production of some forms of primitive life on Earth, as well as on their own study of primitive life near the Rio Tinto river in Spain. NASA officials soon distanced NASA from the scientists' claims, and Stoker herself backed off from her initial assertions. In November 2011, NASA launched the Mars Science Laboratory that landed the Curiosity rover on Mars. It is designed to assess the past and present habitability on Mars using a variety of scientific instruments. The rover landed on Mars at Gale Crater in August 2012. A group of scientists at Cornell University started a catalog of microorganisms, with the way each one reacts to sunlight. The goal is to help with the search for similar organisms in exoplanets, as the starlight reflected by planets rich in such organisms would have a specific spectrum, unlike that of starlight reflected from lifeless planets. If Earth was studied from afar with this system, it would reveal a shade of green, as a result of the abundance of plants with photosynthesis. In August 2011, NASA studied meteorites found on Antarctica, finding adenine, guanine, hypoxanthine, and xanthine. Adenine and guanine are components of DNA, and the others are used in other biological processes. The studies ruled out pollution of the meteorites on Earth, as those components would not be freely available the way they were found in the samples. This discovery suggests that several organic molecules that serve as building blocks of life may be generated within asteroids and comets. In October 2011, scientists reported that cosmic dust contains complex organic compounds ("amorphous organic solids with a mixed aromatic-aliphatic structure") that could be created naturally, and rapidly, by stars. It is still unclear if those compounds played a role in the creation of life on Earth, but Sun Kwok, of the University of Hong Kong, thinks so. "If this is the case, life on Earth may have had an easier time getting started as these organics can serve as basic ingredients for life." In August 2012, and in a world first, astronomers at Copenhagen University reported the detection of a specific sugar molecule, glycolaldehyde, in a distant star system. The molecule was found around the protostellar binary IRAS 16293-2422, which is located 400 light years from Earth. Glycolaldehyde is needed to form ribonucleic acid, or RNA, which is similar in function to DNA. This finding suggests that complex organic molecules may form in stellar systems prior to the formation of planets, eventually arriving on young planets early in their formation. In December 2023, astronomers reported the first time discovery, in the plumes of Enceladus, moon of the planet Saturn, of hydrogen cyanide, a possible chemical essential for life as we know it, as well as other organic molecules, some of which are yet to be better identified and understood. According to the researchers, "these [newly discovered] compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life." Although most searches are focused on the biology of extraterrestrial life, an extraterrestrial intelligence capable enough to develop a civilization may be detectable by other means as well. Technology may generate technosignatures, effects on the native planet that may not be caused by natural causes. There are three main types of techno-signatures considered: interstellar communications, effects on the atmosphere, and planetary-sized structures such as Dyson spheres. Organizations such as the SETI Institute search the cosmos for potential forms of communication. They started with radio waves, and now search for laser pulses as well. The challenge for this search is that there are natural sources of such signals as well, such as gamma-ray bursts and supernovae, and the difference between a natural signal and an artificial one would be in its specific patterns. Astronomers intend to use artificial intelligence for this, as it can manage large amounts of data and is devoid of biases and preconceptions. Besides, even if there is an advanced extraterrestrial civilization, there is no guarantee that it is transmitting radio communications in the direction of Earth. The length of time required for a signal to travel across space means that a potential answer may arrive decades or centuries after the initial message. The atmosphere of Earth is rich in nitrogen dioxide as a result of air pollution, which can be detectable. The natural abundance of carbon, which is also relatively reactive, makes it likely to be a basic component of the development of a potential extraterrestrial technological civilization, as it is on Earth. Fossil fuels may likely be generated and used on such worlds as well. The abundance of chlorofluorocarbons in the atmosphere can also be a clear technosignature, considering their role in ozone depletion. Light pollution may be another technosignature, as multiple lights on the night side of a rocky planet can be a sign of advanced technological development. However, modern telescopes are not strong enough to study exoplanets with the required level of detail to perceive it. The Kardashev scale proposes that a civilization may eventually start consuming energy directly from its local star. This would require giant structures built next to it, called Dyson spheres. Those speculative structures would cause an excess infrared radiation, that telescopes may notice. The infrared radiation is typical of young stars, surrounded by dusty protoplanetary disks that will eventually form planets. An older star such as the Sun would have no natural reason to have excess infrared radiation. The presence of heavy elements in a star's light-spectrum is another potential biosignature; such elements would (in theory) be found if the star were being used as an incinerator/repository for nuclear waste products. Some astronomers search for extrasolar planets that may be conducive to life, narrowing the search to terrestrial planets within the habitable zones of their stars. Since 1992, over four thousand exoplanets have been discovered (6,128 planets in 4,584 planetary systems including 1,017 multiple planetary systems as of 30 October 2025). The extrasolar planets so far discovered range in size from that of terrestrial planets similar to Earth's size to that of gas giants larger than Jupiter. The number of observed exoplanets is expected to increase greatly in the coming years.[better source needed] The Kepler space telescope has also detected a few thousand candidate planets, of which about 11% may be false positives. There is at least one planet on average per star. About 1 in 5 Sun-like stars[a] have an "Earth-sized"[b] planet in the habitable zone,[c] with the nearest expected to be within 12 light-years distance from Earth. Assuming 200 billion stars in the Milky Way,[d] that would be 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if red dwarfs are included. The rogue planets in the Milky Way possibly number in the trillions. The nearest known exoplanet is Proxima Centauri b, located 4.2 light-years (1.3 pc) from Earth in the southern constellation of Centaurus. As of March 2014[update], the least massive exoplanet known is PSR B1257+12 A, which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is DENIS-P J082303.1−491201 b, about 29 times the mass of Jupiter, although according to most definitions of a planet, it is too massive to be a planet and may be a brown dwarf instead. Almost all of the planets detected so far are within the Milky Way, but there have also been a few possible detections of extragalactic planets. The study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life. One sign that a planet probably already contains life is the presence of an atmosphere with significant amounts of oxygen, since that gas is highly reactive and generally would not last long without constant replenishment. This replenishment occurs on Earth through photosynthetic organisms. One way to analyse the atmosphere of an exoplanet is through spectrography when it transits its star, though this might only be feasible with dim stars like white dwarfs. History and cultural impact The modern concept of extraterrestrial life is based on assumptions that were not commonplace during the early days of astronomy. The first explanations for the celestial objects seen in the night sky were based on mythology. Scholars from Ancient Greece were the first to consider that the universe is inherently understandable and rejected explanations based on supernatural incomprehensible forces, such as the myth of the Sun being pulled across the sky in the chariot of Apollo. They had not developed the scientific method yet and based their ideas on pure thought and speculation, but they developed precursor ideas to it, such as that explanations had to be discarded if they contradict observable facts. The discussions of those Greek scholars established many of the pillars that would eventually lead to the idea of extraterrestrial life, such as Earth being round and not flat. The cosmos was first structured in a geocentric model that considered that the sun and all other celestial bodies revolve around Earth. However, they did not consider them as worlds. In Greek understanding, the world was composed by both Earth and the celestial objects with noticeable movements. Anaximander thought that the cosmos was made from apeiron, a substance that created the world, and that the world would eventually return to the cosmos. Eventually two groups emerged, the atomists that thought that matter at both Earth and the cosmos was equally made of small atoms of the classical elements (earth, water, fire and air), and the Aristotelians who thought that those elements were exclusive of Earth and that the cosmos was made of a fifth one, the aether. Atomist Epicurus thought that the processes that created the world, its animals and plants should have created other worlds elsewhere, along with their own animals and plants. Aristotle thought instead that all the earth element naturally fell towards the center of the universe, and that would make it impossible for other planets to exist elsewhere. Under that reasoning, Earth was not only in the center, it was also the only planet in the universe. Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the philosophical belief in numerous "worlds" in addition to Earth, which might harbor extraterrestrial life. The earliest recorded assertion of extraterrestrial human life is found in ancient scriptures of Jainism. There are multiple "worlds" mentioned in Jain scriptures that support human life. These include, among others, Bharat Kshetra, Mahavideh Kshetra, Airavat Kshetra, and Hari kshetra. Medieval Muslim writers like Fakhr al-Din al-Razi and Muhammad al-Baqir supported cosmic pluralism on the basis of the Qur'an. Chaucer's poem The House of Fame engaged in medieval thought experiments that postulated the plurality of worlds. However, those ideas about other worlds were different from the current knowledge about the structure of the universe, and did not postulate the existence of planetary systems other than the Solar System. When those authors talk about other worlds, they talk about places located at the center of their own systems, and with their own stellar vaults and cosmos surrounding them. The Greek ideas and the disputes between atomists and Aristotelians outlived the fall of the Greek empire. The Great Library of Alexandria compiled information about it, part of which was translated by Islamic scholars and thus survived the end of the Library. Baghdad combined the knowledge of the Greeks, the Indians, the Chinese and its own scholars, and the knowledge expanded through the Byzantine Empire. From there it eventually returned to Europe by the time of the Middle Ages. However, as the Greek atomist doctrine held that the world was created by random movements of atoms, with no need for a creator deity, it became associated with atheism, and the dispute intertwined with religious ones. Still, the Church did not react to those topics in a homogeneous way, and there were stricter and more permissive views within the church itself. The first known mention of the term 'panspermia' was in the writings of the 5th-century BC Greek philosopher Anaxagoras. He proposed the idea that life exists everywhere. By the time of the late Middle Ages there were many known inaccuracies in the geocentric model, but it was kept in use because naked eye observations provided limited data. Nicolaus Copernicus started the Copernican Revolution by proposing that the planets revolve around the sun rather than Earth. His proposal had little acceptance at first because, as he kept the assumption that orbits were perfect circles, his model led to as many inaccuracies as the geocentric one. Tycho Brahe improved the available data with naked-eye observatories, which worked with highly complex sextants and quadrants. Tycho could not make sense of his observations, but Johannes Kepler did: orbits were not perfect circles, but ellipses. This knowledge benefited the Copernican model, which worked now almost perfectly. The invention of the telescope a short time later, perfected by Galileo Galilei, clarified the final doubts, and the paradigm shift was completed. Under this new understanding, the notion of extraterrestrial life became feasible: if Earth is but just a planet orbiting around a star, there may be planets similar to Earth elsewhere. The astronomical study of distant bodies also proved that physical laws are the same elsewhere in the universe as on Earth, with nothing making the planet truly special. The new ideas were met with resistance from the Catholic church. Galileo was tried for the heliocentric model, which was considered heretical, and forced to recant it. The best-known early-modern proponent of ideas of extraterrestrial life was the Italian philosopher Giordano Bruno, who argued in the 16th century for an infinite universe in which every star is surrounded by its own planetary system. Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants". Bruno's belief in the plurality of worlds was one of the charges leveled against him by the Venetian Holy Inquisition, which tried and executed him. The heliocentric model was further strengthened by the postulation of the theory of gravity by Sir Isaac Newton. This theory provided the mathematics that explains the motions of all things in the universe, including planetary orbits. By this point, the geocentric model was definitely discarded. By this time, the use of the scientific method had become a standard, and new discoveries were expected to provide evidence and rigorous mathematical explanations. Science also took a deeper interest in the mechanics of natural phenomena, trying to explain not just the way nature works but also the reasons for working that way. There was very little actual discussion about extraterrestrial life before this point, as the Aristotelian ideas remained influential while geocentrism was still accepted. When it was finally proved wrong, it not only meant that Earth was not the center of the universe, but also that the lights seen in the sky were not just lights, but physical objects. The notion that life may exist in them as well soon became an ongoing topic of discussion, although one with no practical ways to investigate. The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel, the discoverer of Uranus, was one of many 18th–19th-century astronomers who believed that the Solar System is populated by alien life. Other scholars of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment, even the Sun and Moon were considered candidates for extraterrestrial inhabitants. Speculation about life on Mars increased in the late 19th century, following telescopic observation of apparent Martian canals – which soon, however, turned out to be optical illusions. Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilisation. Spectroscopic analysis of Mars's atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen was present in the Martian atmosphere. By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal hypothesis. As a consequence of the belief in the spontaneous generation there was little thought about the conditions of each celestial body: it was simply assumed that life would thrive anywhere. This theory was disproved by Louis Pasteur in the 19th century. Popular belief in thriving alien civilisations elsewhere in the solar system still remained strong until Mariner 4 and Mariner 9 provided close images of Mars, which debunked forever the idea of the existence of Martians and decreased the previous expectations of finding alien life in general. The end of the spontaneous generation belief forced investigation into the origin of life. Although abiogenesis is the more accepted theory, a number of authors reclaimed the term "panspermia" and proposed that life was brought to Earth from elsewhere. Some of those authors are Jöns Jacob Berzelius (1834), Kelvin (1871), Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903). The science fiction genre, although not so named during the time, developed during the late 19th century. The expansion of the genre of extraterrestrials in fiction influenced the popular perception over the real-life topic, making people eager to jump to conclusions about the discovery of aliens. Science marched at a slower pace, some discoveries fueled expectations and others dashed excessive hopes. For example, with the advent of telescopes, most structures seen on the Moon or Mars were immediately attributed to Selenites or Martians, and later ones (such as more powerful telescopes) revealed that all such discoveries were natural features. A famous case is the Cydonia region of Mars, first imaged by the Viking 1 orbiter. The low-resolution photos showed a rock formation that resembled a human face, but later spacecraft took photos in higher detail that showed that there was nothing special about the site. The search and study of extraterrestrial life became a science of its own, astrobiology. Also known as exobiology, this discipline is studied by the NASA, the ESA, the INAF, and others. Astrobiology studies life from Earth as well, but with a cosmic perspective. For example, abiogenesis is of interest to astrobiology, not because of the origin of life on Earth, but for the chances of a similar process taking place in other celestial bodies. Many aspects of life, from its definition to its chemistry, are analyzed as either likely to be similar in all forms of life across the cosmos or only native to Earth. Astrobiology, however, remains constrained by the current lack of extraterrestrial life-forms to study, as all life on Earth comes from the same ancestor, and it is hard to infer general characteristics from a group with a single example to analyse. The 20th century came with great technological advances, speculations about future hypothetical technologies, and an increased basic knowledge of science by the general population thanks to science divulgation through the mass media. The public interest in extraterrestrial life and the lack of discoveries by mainstream science led to the emergence of pseudosciences that provided affirmative, if questionable, answers to the existence of aliens. Ufology claims that many unidentified flying objects (UFOs) would be spaceships from alien species, and ancient astronauts hypothesis claim that aliens would have visited Earth in antiquity and prehistoric times but people would have failed to understand it by then. Most UFOs or UFO sightings can be readily explained as sightings of Earth-based aircraft (including top-secret aircraft), known astronomical objects or weather phenomenons, or as hoaxes. Looking beyond the pseudosciences, Lewis White Beck strove to elevate the level of public discourse on the topic of extraterrestrial life by tracing the evolution of philosophical thought over the centuries from ancient times into the modern era. His review of the contributions made by Lucretius, Plutarch, Aristotle, Copernicus, Immanuel Kant, John Wilkins, Charles Darwin and Karl Marx demonstrated that even in modern times, humanity could be profoundly influenced in its search for extraterrestrial life by subtle and comforting archetypal ideas which are largely derived from firmly held religious, philosophical and existential belief systems. On a positive note, however, Beck further argued that even if the search for extraterrestrial life proves to be unsuccessful, the endeavor itself could have beneficial consequences by assisting humanity in its attempt to actualize superior ways of living here on Earth. By the 21st century, it was accepted that multicellular life in the Solar System can only exist on Earth, but the interest in extraterrestrial life increased regardless. This is a result of the advances in several sciences. The knowledge of planetary habitability allows to consider on scientific terms the likelihood of finding life at each specific celestial body, as it is known which features are beneficial and harmful for life. Astronomy and telescopes also improved to the point exoplanets can be confirmed and even studied, increasing the number of search places. Life may still exist elsewhere in the Solar System in unicellular form, but the advances in spacecraft allow to send robots to study samples in situ, with tools of growing complexity and reliability. Although no extraterrestrial life has been found and life may still be just a rarity from Earth, there are scientific reasons to suspect that it can exist elsewhere, and technological advances that may detect it if it does. Many scientists are optimistic about the chances of finding alien life. In the words of SETI's Frank Drake, "All we know for sure is that the sky is not littered with powerful microwave transmitters". Drake noted that it is entirely possible that advanced technology results in communication being carried out in some way other than conventional radio transmission. At the same time, the data returned by space probes, and giant strides in detection methods, have allowed science to begin delineating habitability criteria on other worlds, and to confirm that at least other planets are plentiful, though aliens remain a question mark. The Wow! signal, detected in 1977 by a SETI project, remains a subject of speculative debate. On the other hand, other scientists are pessimistic. Jacques Monod wrote that "Man knows at last that he is alone in the indifferent immensity of the universe, whence which he has emerged by chance". In 2000, geologist and paleontologist Peter Ward and astrobiologist Donald Brownlee published a book entitled Rare Earth: Why Complex Life is Uncommon in the Universe.[better source needed] In it, they discussed the Rare Earth hypothesis, in which they claim that Earth-like life is rare in the universe, whereas microbial life is common. Ward and Brownlee are open to the idea of evolution on other planets that is not based on essential Earth-like characteristics such as DNA and carbon. As for the possible risks, theoretical physicist Stephen Hawking warned in 2010 that humans should not try to contact alien life forms. He warned that aliens might pillage Earth for resources. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans", he said. Jared Diamond had earlier expressed similar concerns. On 20 July 2015, Hawking and Russian billionaire Yuri Milner, along with the SETI Institute, announced a well-funded effort, called the Breakthrough Initiatives, to expand efforts to search for extraterrestrial life. The group contracted the services of the 100-meter Robert C. Byrd Green Bank Telescope in West Virginia in the United States and the 64-meter Parkes Telescope in New South Wales, Australia. On 13 February 2015, scientists (including Geoffrey Marcy, Seth Shostak, Frank Drake and David Brin) at a convention of the American Association for the Advancement of Science, discussed Active SETI and whether transmitting a message to possible intelligent extraterrestrials in the Cosmos was a good idea; one result was a statement, signed by many, that a "worldwide scientific, political and humanitarian discussion must occur before any message is sent". Government responses The 1967 Outer Space Treaty and the 1979 Moon Agreement define rules of planetary protection against potentially hazardous extraterrestrial life. COSPAR also provides guidelines for planetary protection. A committee of the United Nations Office for Outer Space Affairs had in 1977 discussed for a year strategies for interacting with extraterrestrial life or intelligence. The discussion ended without any conclusions. As of 2010, the UN lacks response mechanisms for the case of an extraterrestrial contact. One of the NASA divisions is the Office of Safety and Mission Assurance (OSMA), also known as the Planetary Protection Office. A part of its mission is to "rigorously preclude backward contamination of Earth by extraterrestrial life." In 2016, the Chinese Government released a white paper detailing its space program. According to the document, one of the research objectives of the program is the search for extraterrestrial life. It is also one of the objectives of the Chinese Five-hundred-meter Aperture Spherical Telescope (FAST) program. In 2020, Dmitry Rogozin, the head of the Russian space agency, said the search for extraterrestrial life is one of the main goals of deep space research. He also acknowledged the possibility of existence of primitive life on other planets of the Solar System. The French space agency has an office for the study of "non-identified aero spatial phenomena". The agency is maintaining a publicly accessible database of such phenomena, with over 1600 detailed entries. According to the head of the office, the vast majority of entries have a mundane explanation; but for 25% of entries, their extraterrestrial origin can neither be confirmed nor denied. In 2020, chairman of the Israel Space Agency Isaac Ben-Israel stated that the probability of detecting life in outer space is "quite large". But he disagrees with his former colleague Haim Eshed who stated that there are contacts between an advanced alien civilisation and some of Earth's governments. In fiction Although the idea of extraterrestrial peoples became feasible once astronomy developed enough to understand the nature of planets, they were not thought of as being any different from humans. Having no scientific explanation for the origin of mankind and its relation to other species, there was no reason to expect them to be any other way. This was changed by the 1859 book On the Origin of Species by Charles Darwin, which proposed the theory of evolution. Now with the notion that evolution on other planets may take other directions, science fiction authors created bizarre aliens, clearly distinct from humans. A usual way to do that was to add body features from other animals, such as insects or octopuses. Costuming and special effects feasibility alongside budget considerations forced films and TV series to tone down the fantasy, but these limitations lessened since the 1990s with the advent of computer-generated imagery (CGI), and later on as CGI became more effective and less expensive. Real-life events sometimes captivate people's imagination and this influences the works of fiction. For example, during the Barney and Betty Hill incident, the first recorded claim of an alien abduction, the couple reported that they were abducted and experimented on by aliens with oversized heads, big eyes, pale grey skin, and small noses, a description that eventually became the grey alien archetype once used in works of fiction. See also Notes References Further reading External links |
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Contents Non-linear editing Non-linear editing (NLE) is a form of offline editing for audio, video, and image editing. In offline editing, the original content is not modified in the course of editing. In non-linear editing, edits are specified and modified by specialized software. A pointer-based playlist, effectively an edit decision list (EDL), for video and audio, or a directed acyclic graph for still images, is used to keep track of edits. Each time the edited audio, video, or image is rendered, played back, or accessed, it is reconstructed from the original source and the specified editing steps. Although this process is more computationally intensive than directly modifying the original content, changing the edits themselves can be almost instantaneous, and it prevents further generation loss as the audio, video, or image is edited. A non-linear editing system is a video editing (NLVE) program or application, or an audio editing (NLAE) digital audio workstation (DAW) system. These perform non-destructive editing on source material. The name is in contrast to 20th-century methods of linear video editing and film editing. Basic techniques A non-linear editing approach may be used when all assets are available as files on video servers, or on local solid-state drives or hard disks, rather than recordings on reels or tapes. While linear editing is tied to the need to sequentially view film or hear tape, non-linear editing enables direct access to any video frame in a digital video clip, without having to play or scrub/shuttle through adjacent footage to reach it, as is necessary with video tape linear editing systems. When ingesting audio or video feeds, metadata is attached to the clip. That metadata can be attached automatically (timecode, localization, take number, name of the clip) or manually (players' names, characters, in sports). It is then possible to access any frame by entering directly the timecode or the descriptive metadata. An editor can, for example, at the end of the day in the Olympic Games, easily retrieve all the clips related to the players who received a gold medal. The non-linear editing method is similar in concept to the cut and paste techniques used in information technology (IT). However, with the use of non-linear editing systems, the destructive act of cutting of film negatives is eliminated. It can also be viewed as the audio/video equivalent of word processing, which is why it is called desktop video editing in the consumer space. Broadcast workflows and advantages In broadcasting applications, video and audio data are first captured to hard disk-based systems or other digital storage devices. The data are then imported into servers employing any necessary transcoding, digitizing or transfer. Once imported, the source material can be edited on a computer using any of a wide range of video editing software. The end product of the offline non-linear editing process is a frame-accurate edit decision list (EDL), which can be taken, together with the source tapes, to an online quality tape or film editing suite. The EDL is then read into an edit controller and used to create a replica of the offline edit by playing portions of the source tapes back at full quality and recording them to a master as per the exact edit points of the EDL. Editing software records the editor's decisions in an EDL that is exportable to other editing tools. Many generations and variations of the EDL can exist without storing many different copies of the final product, allowing for very flexible editing. It also makes it easy to change cuts and undo previous decisions simply by editing the EDL. Generation loss is also controlled, due to not having to repeatedly re-encode the data when different effects are applied. Generation loss can still occur in digital video or audio when using lossy video or audio compression algorithms, as these introduce artifacts into the source material with each encoding or re-encoding. Codecs such as Apple ProRes, Advanced Video Coding and MP3 are very widely used as they allow for dramatic reductions in file size while often being indistinguishable from the uncompressed or losslessly compressed original. Compared to the linear method of tape-to-tape editing, non-linear editing offers the flexibility of film editing, with random access and easy project organization. In non-linear editing, the original source files are not lost or modified during editing. This is one of the biggest advantages of non-linear editing compared to linear editing. With the EDLs, the editor can work on low-resolution copies of the video. This makes it possible to edit both standard-definition broadcast quality and high definition broadcast quality very quickly on desktop computers that may not have the power to process huge full-quality high-resolution data in real-time. The costs of editing systems have dropped such that non-linear editing tools are now within the reach of home users. Some editing software can now be accessed free as web applications; some, like Cinelerra (focused on the professional market) and Blender, can be downloaded as free software; and some, like Microsoft's Windows Movie Maker or Apple Inc.'s iMovie, come included with the appropriate operating system. Accessing the material The non-linear editing retrieves video media for editing. Because these media exist on the video server or other mass storage that stores the video feeds in a given codec, the editing system can use several methods to access the material: Editor brands The leading professional non-linear editing software for many years has been Avid Media Composer. This software is likely to be present in almost all post-production houses globally, and it is used for feature films, television programs, advertising and corporate editing. In 2011, reports indicated, "Avid is still the most-used NLE on prime-time TV productions, being employed on up to 90 percent of evening broadcast shows." Since then the rise in semi-professional and domestic users of editing software has seen a large rise in other titles becoming very popular in these areas. Other significant software used by many editors is Adobe Premiere Pro (part of Adobe Creative Cloud), Apple Final Cut Pro X, DaVinci Resolve and Lightworks. The take-up of these software titles is to an extent dictated by cost and subscription licence arrangements, as well as the rise in mobile apps and free software. As of January 2019[update], Davinci Resolve has risen in popularity within professional users and others alike - it had a user base of more than 2 million using the free version alone. This is a comparable user base to Apple's Final Cut Pro X, which also had 2 million users as of April 2017[update]. Some notable NLEs are: Home use Early consumer applications using a multimedia computer for non-linear editing of video may have a video capture card to capture analog video or a FireWire connection to capture digital video from a DV camera, with its video editing software. Various editing tasks could then be performed on the imported video before export to another medium, or MPEG encoded for transfer to a DVD. Modern web-based editing systems can take video directly from a camera phone over a mobile connection, and editing can take place through a web browser interface, so, strictly speaking, a computer for video editing does not require any installed hardware or software beyond a web browser and an Internet connection. Nowadays there is a huge amount of home editing which takes place both on desktop and tablets or smartphones. The social media revolution has brought about a significant change in access to powerful editing tools or apps, at everyone's disposal. History When videotapes were first developed in the 1950s, the only way to edit was to physically cut the tape with a razor blade and splice segments together. While the footage excised in this process was not technically destroyed, continuity was lost and the footage was generally discarded. In 1963, with the introduction of the Ampex Editec, videotape could be edited electronically with a process known as linear video editing by selectively copying the original footage to another tape called a master. The original recordings are not destroyed or altered in this process. However, since the final product is a copy of the original, there is a generation loss of quality. The first truly non-linear editor, the CMX 600, was introduced in 1971 by CMX Systems, a joint venture between CBS and Memorex. It recorded and played back black-and-white analog video recorded in "skip-field" mode on modified disk pack drives the size of washing machines that could store a half-hour worth of video & audio for editing. These disk packs were commonly used to store data digitally on mainframe computers of the time. The 600 had a console with two monitors built in. The right monitor, which played the preview video, was used by the editor to make cuts and edit decisions using a light pen. The editor selected from options superimposed as text over the preview video. The left monitor was used to display the edited video. A DEC PDP-11 computer served as a controller for the whole system. Because the video edited on the 600 was in low-resolution black and white, the 600 was suitable only for offline editing. Non-linear editing systems were built in the 1980s using computers coordinating multiple LaserDiscs or banks of VCRs. One example of these tape and disc-based systems was Lucasfilm's EditDroid, which used several LaserDiscs of the same raw footage to simulate random-access editing.[a] EditDroid was demonstrated at NAB in 1984. EditDroid was the first system to introduce modern concepts in non-linear editing such as timeline editing and clip bins. The LA-based post house Laser Edit[b] also had an in-house system using recordable random-access LaserDiscs. The most popular non-linear system in the 1980s was Ediflex, which used a bank of U-matic and VHS VCRs for offline editing. Ediflex was introduced in 1983 on the Universal series "Still the Beaver". By 1985 it was used on over 80% of filmed network programs and Cinedco was awarded the Technical Emmy for "Design and Implementation of Non-Linear Editing for Filmed Programs." In 1984, Montage Picture Processor was demonstrated at NAB. Montage used 17 identical copies of a set of film rushes on modified consumer Betamax VCRs. A custom circuit board was added to each deck that enabled frame-accurate switching and playback using vertical interval timecode. Intelligent positioning and sequencing of the source decks provided a simulation of random-access playback of a lengthy edited sequence without any re-recording. The theory was that with so many copies of the rushes, there could always be one machine cued up to replay the next shot in real time. Changing the EDL could be done easily, and the results seen immediately. The first feature edited on the Montage was Sidney Lumet's Power. Notably, Francis Coppola edited The Godfather Part III on the system, and Stanley Kubrick used it for Full Metal Jacket. It was used on several episodic TV shows (Knots Landing, for one) and on hundreds of commercials and music videos. The original Montage system won an Academy Award for Technical Achievement in 1988.[citation needed] Montage was reincarnated as Montage II in 1987, and Montage III appeared at NAB in 1991, using digital disk technology, which was considerably less cumbersome than the Betamax system. All of these original systems were slow, cumbersome, and had problems with the limited computer horsepower of the time, but the mid-to-late-1980s saw a trend towards non-linear editing, moving away from film editing on Moviolas and the linear videotape method using U-matic VCRs. Computer processing advanced sufficiently by the end of the 1980s to enable true digital imagery and has progressed today to provide this capability in personal desktop computers. An example of computing power progressing to make non-linear editing possible was demonstrated in the first all-digital non-linear editing system, the "Harry" effects compositing system manufactured by Quantel in 1985. Although it was more of a video effects system, it had some non-linear editing capabilities. Most importantly, it could record (and apply effects to) 80 seconds (due to hard disk space limitations) of broadcast-quality uncompressed digital video encoded in 8-bit CCIR 601 format on its built-in hard disk array. The term nonlinear editing was formalized in 1991 with the publication of Michael Rubin's Nonlinear: A Guide to Digital Film and Video Editing—which popularized this terminology over other terminology common at the time, including real-time editing, random-access or RA editing, virtual editing, electronic film editing, and so on.[citation needed] Non-linear editing with computers as it is known today was first introduced by Editing Machines Corp. in 1989 with the EMC2 editor, a PC-based non-linear off-line editing system that utilized magneto-optical disks for storage and playback of video, using half-screen-resolution video at 15 frames per second. A couple of weeks later that same year, Avid introduced the Avid/1, the first in the line of their Media Composer systems. It was based on the Apple Macintosh computer platform (Macintosh II systems were used) with special hardware and software developed and installed by Avid. The video quality of the Avid/1 (and later Media Composer systems from the late 1980s) was somewhat low (about VHS quality), due to the use of a very early version of a Motion JPEG (M-JPEG) codec. It was sufficient, however, to provide a versatile system for offline editing. Lost in Yonkers (1993) was the first film edited with Avid Media Composer, and the first long-form documentary so edited was the HBO program Earth and the American Dream, which won a National Primetime Emmy Award for Editing in 1993. The NewTek Video Toaster Flyer for the Amiga included non-linear editing capabilities in addition to processing live video signals. The Flyer used hard drives to store video clips and audio, and supported complex scripted playback. The Flyer provided simultaneous dual-channel playback, which let the Toaster's video switcher perform transitions and other effects on video clips without additional rendering. The Flyer portion of the Video Toaster/Flyer combination was a complete computer of its own, having its own microprocessor and embedded software. Its hardware included three embedded SCSI controllers. Two of these SCSI buses were used to store video data, and the third to store audio. The Flyer used a proprietary wavelet compression algorithm known as VTASC, which was well regarded at the time for offering better visual quality than comparable non-linear editing systems using motion JPEG. Until 1993, the Avid Media Composer was most often used for editing commercials or other small-content and high-value projects. This was primarily because the purchase cost of the system was very high, especially in comparison to the offline tape-based systems that were then in general use. Hard disk storage was also expensive enough to be a limiting factor on the quality of footage that most editors could work with or the amount of material that could be held digitized at any one time.[c] Up until 1992, the Apple Macintosh computers could access only 50 gigabytes of storage at once. This limitation was overcome by a digital video R&D team at the Disney Channel led by Rick Eye. By February 1993, this team had integrated a long-form system that let the Avid Media Composer running on the Apple Macintosh access over seven terabytes of digital video data. With instant access to the shot footage of an entire movie, long-form non-linear editing was now possible. The system made its debut at the NAB conference in 1993 in the booths of the three primary sub-system manufacturers, Avid, Silicon Graphics and Sony. Within a year, thousands of these systems had replaced 35mm film editing equipment in major motion picture studios and TV stations worldwide. Although M-JPEG became the standard codec for NLE during the early 1990s, it had drawbacks. Its high computational requirements ruled out software implementations imposing extra cost and complexity of hardware compression/playback cards. More importantly, the traditional tape workflow had involved editing from videotape, often in a rented facility. When the editor left the edit suite, they could securely take their tapes with them. But the M-JPEG data rate was too high for systems like Avid/1 on the Apple Macintosh and Lightworks on PC to store the video on removable storage. The content needed to be stored on fixed hard disks instead. The secure tape paradigm of keeping your content with you was not possible with these fixed disks. Editing machines were often rented from facilities houses on a per-hour basis, and some productions chose to delete their material after each edit session, and then ingest it again the next day to guarantee the security of their content.[citation needed] In addition, each NLE system had storage limited by its fixed disk capacity. These issues were addressed by a small UK company, Eidos Interactive. Eidos chose the new ARM-based computers from the UK and implemented an editing system, launched in Europe in 1990 at the International Broadcasting Convention. Because it implemented its own compression software designed specifically for non-linear editing, the Eidos system had no requirement for JPEG hardware and was cheap to produce. The software could decode multiple video and audio streams at once for real-time effects at no extra cost. But most significantly, for the first time, it supported unlimited cheap removable storage. The Eidos Edit 1, Edit 2, and later Optima systems let the editor use any Eidos system, rather than being tied down to a particular one, and still keep his data secure. The Optima software editing system was closely tied to Acorn hardware, such that when Acorn ceased development of a successor to its Risc PC and discontinued its traditional operations in the late 1990s, it presented difficulties that Eidos's founder, Stephen Streater, attempted to overcome through an ultimately unsuccessful bid for various Acorn hardware and software technologies. Due to a corporate decision to focus on the games industry, Eidos discontinued the Optima system, and Streater left the company in 1999. In the early 1990s, a small American company called Data Translation took what it knew about coding and decoding pictures for the US military and large corporate clients and spent $12 million developing a desktop editor based on its proprietary compression algorithms and off-the-shelf parts. Their aim was to democratize the desktop and take some of Avid's market. In August 1993, Media 100 entered the market, providing would-be editors with a low-cost, high-quality platform.[citation needed] Around the same period, other competitors provided non-linear systems that required special hardware—typically cards added to the computer system. Fast Video Machine was a PC-based system that first came out as an offline system, and later became more online editing capable. The Imix video cube was also a contender for media production companies. The Imix Video Cube had a control surface with faders to allow mixing and shuttle control. Data Translation's Media 100 came with three different JPEG codecs for different types of graphics and many resolutions. DOS-based D/Vision Pro was released by TouchVision Systems, Inc. in the mid-1990s and worked with the Action Media II board. These other companies caused tremendous downward market pressure on Avid. Avid was forced to continually offer lower-priced systems to compete with the Media 100 and other systems. Inspired by the success of Media 100, members of the Premiere development team left Adobe to start a project called "Keygrip" for Macromedia. Difficulty raising support and money for development led the team to take their non-linear editor to the NAB Show. After various companies made offers, Keygrip was purchased by Apple as Steve Jobs wanted a product to compete with Adobe Premiere in the desktop video market. At around the same time, Avid—now with Windows versions of its editing software—was considering abandoning the Macintosh platform. Apple released Final Cut Pro in 1999, and despite not being taken seriously at first by professionals, it has evolved into a serious competitor to entry-level Avid systems. Another leap came in the late 1990s with the launch of DV-based video formats for consumer and professional use. With DV came IEEE 1394 (FireWire/iLink), a simple and inexpensive way of getting video into and out of computers. Users no longer had to convert video from analog to digital—it was recorded as digital to start with—and FireWire offered a straightforward way to transfer video data without additional hardware. With this innovation, editing became a more realistic proposition for software running on standard computers. It enabled desktop editing, producing high-quality results at a fraction of the cost of earlier systems. In early 2000, the introduction of highly compressed HD formats such as HDV has continued this trend, making it possible to edit HD material on a standard computer running a software-only editing system. Avid is an industry standard used for major feature films, television programs, and commercials. Final Cut Pro received a Technology & Engineering Emmy Award in 2002. Since 2000, many personal computers include basic non-linear video editing software free of charge. This is the case of Apple iMovie for the Macintosh platform, various open-source programs like Kdenlive, Cinelerra-GG Infinity and PiTiVi for the Linux platform, and Windows Movie Maker for the Windows platform. This phenomenon has brought low-cost non-linear editing to consumers. The demands of video editing in terms of the volumes of data involved means the proximity of the stored footage being edited to the NLE system doing the editing is governed partly by the capacity of the data connection between the two. The increasing availability of broadband internet combined with the use of lower-resolution copies of original material provides an opportunity to not just review and edit material remotely but also open up access to far more people to the same content at the same time. In 2004 the first cloud-based video editor, known as Blackbird and based on technology invented by Stephen Streater, was demonstrated at IBC and recognized by the RTS the following year. Since that time a number of other cloud-based editors have become available including systems from Avid, WeVideo and Grabyo. Despite their reliance on a network connection, the need to ingest material before editing can take place, and the use of lower-resolution video proxies, their adoption has grown. Their popularity has been driven largely by efficiencies arising from opportunities for greater collaboration and the potential for cost savings derived from using a shared platform, hiring rather than buying infrastructure, and the use of conventional IT equipment over hardware specifically designed for video editing. As of 2014[update], 4K Video in NLE was fairly new, but it was being used in the creation of many movies throughout the world, due to the increased use of advanced 4K cameras such as the Red Camera. Examples of software for this task include Avid Media Composer, Apple's Final Cut Pro X, Sony Vegas, Adobe Premiere, DaVinci Resolve, Edius, and Cinelerra-GG Infinity for Linux. As of 2019[update] 8K video was relatively new. 8K video editing requires advanced hardware and software capable of handling the standard.[citation needed] For imaging software, early works such as HSC Software's Live Picture brought non-destructive editing to the professional market and current efforts such as GEGL provide an implementation being used in open-source image editing software. Quality An early concern with non-linear editing had been picture and sound quality available to editors. Storage limitations at the time required that all material undergo lossy compression techniques to reduce the amount of memory occupied. Improvements in compression techniques and disk storage capacity have mitigated these concerns, and the migration to high-definition video and audio has virtually removed this concern completely. Most professional NLEs are also able to edit uncompressed video with the appropriate hardware.[citation needed] See also Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Atmospheric_stripping] | [TOKENS: 6034] |
Contents Solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of particle species found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. There are also rarer traces of some other nuclei and isotopes such as phosphorus, titanium, chromium, and nickel's isotopes 58Ni, 60Ni, and 62Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface. At a distance of more than a few solar radii from the Sun, the solar wind reaches speeds of 250–750 km/s and is supersonic, meaning it moves faster than the speed of fast magnetosonic waves. The flow of the solar wind is no longer supersonic at the termination shock. Other related phenomena include the aurora (northern and southern lights), comet tails that always point away from the Sun, and geomagnetic storms that can change the direction of magnetic field lines. History The existence of particles flowing outward from the Sun to the Earth was first suggested by British astronomer Richard C. Carrington. In 1859, Carrington and Richard Hodgson independently made the first observations of what would later be called a solar flare. This is a sudden, localised increase in brightness on the solar disc, which is now known to often occur in conjunction with an episodic ejection of material and magnetic flux from the Sun's atmosphere, known as a coronal mass ejection. The following day, a powerful geomagnetic storm was observed, and Carrington suspected that there might be a connection; the geomagnetic storm is now attributed to the arrival of the coronal mass ejection in near-Earth space and its subsequent interaction with the Earth's magnetosphere. Irish academic George FitzGerald later suggested that matter was being regularly accelerated away from the Sun, reaching the Earth after several days. In 1910, British astrophysicist Arthur Eddington essentially suggested the existence of the solar wind, without naming it, in a footnote to an article on Comet Morehouse. Eddington's proposition was never fully embraced, even though he had also made a similar suggestion at a Royal Institution address the previous year, in which he had postulated that the ejected material consisted of electrons, whereas in his study of Comet Morehouse he had supposed them to be ions. The idea that the ejected material consisted of both ions and electrons was first suggested by Norwegian scientist Kristian Birkeland. His geomagnetic surveys showed that auroral activity was almost uninterrupted. As these displays and other geomagnetic activity were being produced by particles from the Sun, he concluded that the Earth was being continually bombarded by "rays of electric corpuscles emitted by the Sun". He proposed in 1916 that, "From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, but of both kinds"; in other words, the solar wind consists of both negative electrons and positive ions. Three years later, in 1919, British physicist Frederick Lindemann also suggested that the Sun ejects particles of both polarities: protons as well as electrons. Around the 1930s, scientists had concluded that the temperature of the solar corona must be a million degrees Celsius because of the way it extended into space (as seen during a total solar eclipse). Later spectroscopic work confirmed this extraordinary temperature to be the case. In the mid-1950s, British mathematician Sydney Chapman calculated the properties of a gas at such a temperature and determined that the corona being such a superb conductor of heat, it must extend way out into space, beyond the orbit of Earth. Also in the 1950s, German astronomer Ludwig Biermann became interested in the fact that the tail of a comet always points away from the Sun, regardless of the direction in which the comet is travelling. Biermann postulated that this happens because the Sun emits a steady stream of particles that pushes the comet's tail away. German astronomer Paul Ahnert is credited (by Wilfried Schröder) as being the first to relate solar wind to the direction of a comet's tail based on observations of the comet Whipple–Fedke (1942g). In 1956, Biermann came to the University of Chicago, where he discussed his results with the astrophysicist Eugene Parker. Parker also discussed the solar corona with mathematician Sydney Chapman, who mentioned that "the corona is so hot that it should extend clear to the orbit of the Earth". Parker then conjectured that "the corona and solar corpuscular radiation must be the same thing": Parker himself said that the math needed for the solar wind discovery was just "four lines of algebra". I called it the solar wind because I felt that solar corpuscular radiation gives the wrong idea. With that term, one thinks of individual particles being shot out, which was the original picture we had. But it really is an ordinary flow of gas. The math needed to discover the solar wind was, per Parker just "four lines of algebra". Parker proposed that although the Sun's corona is strongly attracted by solar gravity, it is such a good conductor of heat that it is still very hot at large distances from the Sun. As solar gravity weakens with increasing distance from the Sun, the hydrodynamic effect is identical to a de Laval nozzle, inciting a transition from subsonic to supersonic flow. When Parker wrote hydrodynamic equations for an isothermal, extended coronal atmosphere, the plasma flow velocity integrated to a closed form: [ v 2 v m 2 − ln ( v 2 v m 2 ) ] = 4 ln ( r a ) + ( v esc 2 v m 2 ) ( a r ) − 4 ln ( v esc 2 v m 2 ) − 3 + ln 256 {\displaystyle \left[{\frac {v^{2}}{v_{m}^{2}}}-\ln \left({\frac {v^{2}}{v_{m}^{2}}}\right)\right]=4\ln \left({\frac {r}{a}}\right)+\left({\frac {v_{\text{esc}}^{2}}{v_{m}^{2}}}\right)\left({\frac {a}{r}}\right)-4\ln \left({\frac {v_{\text{esc}}^{2}}{v_{m}^{2}}}\right)-3+\ln 256} One solution to this equation was immediately recognizable as a solar wind. Parker's theory of supersonic solar wind also predicted the shape of the solar magnetic field in the outer Solar System. Parker argued that a million-degree corona cannot remain static: pressure forces must drive a radially expanding flow that accelerates from subsonic near the Sun to supersonic beyond a critical point. He further noted that solar rotation winds outward-advected magnetic field lines into a spiral pattern in the ecliptic, now called the Parker spiral. His theoretical modeling was not immediately accepted by the astronomical community: when Parker submitted the results to The Astrophysical Journal in 1958, two reviewers recommended its rejection. One reviewer commented on the paper: "Well I would suggest that Parker go to the library and read up on the subject before he tries to write a paper about it, because this is utter nonsense." The editor of the journal and Parker's colleague at the University of Chicago, future Nobel prize-winner Subrahmanyan Chandrasekhar, finding no obvious errors in the paper, overruled the reviewers and published the paper, even though he disagreed with Parker's theory. A colleague at the University of Chicago, Joseph W. Chamberlain, who published a paper in 1960 showing that the plasma flow velocity equation also admitted a solution with an exponential decay in flow velocity away from the sun. Chamberlain's subsonic solution was called the "solar breeze", and Italian plasma physicist Marco Velli later showed that "the breeze solution is unstable" to low frequency perturbations. Parker's theoretical predictions were confirmed by satellite observations; it is called to be "a unique example in astrophysics, due to its immediate and brief confirmation by observations". In January 1959, the Soviet spacecraft Luna 1 first directly observed the solar wind and measured its strength, using hemispherical ion traps. The discovery, made by Konstantin Gringauz [ru], was verified by Luna 2, Luna 3, and the more distant measurements of Venera 1. Three years later, a similar measurement was performed by American geophysicist Marcia Neugebauer and collaborators using the Mariner 2 spacecraft. Mariner 2 data revealed two types of solar wind, a low- and a high-speed components. The first numerical simulation of the solar wind in the solar corona, including closed and open field lines, was performed by Pneuman and Kopp in 1971. The magnetohydrodynamics equations in steady state were solved iteratively starting with an initial dipolar configuration. In 1990, the Ulysses probe was launched to study the solar wind from high solar latitudes. All prior observations had been made at or near the Solar System's ecliptic plane. In the late 1990s, the Ultraviolet Coronal Spectrometer (UVCS) instrument on board the SOHO spacecraft observed the acceleration region of the fast solar wind emanating from the poles of the Sun and found that the wind accelerates much faster than can be accounted for by thermodynamic expansion alone. Parker's model predicted that the wind should make the transition to supersonic flow at an altitude of about four solar radii (approx. 3,000,000 km) from the photosphere (surface); but the transition (or "sonic point") now appears to be much lower, perhaps only one solar radius (approx. 700,000 km) above the photosphere, suggesting that some additional mechanism accelerates the solar wind away from the Sun. The acceleration of the fast wind is still not understood and cannot be fully explained by Parker's theory. However, the gravitational and electromagnetic explanation for this acceleration is detailed in an earlier paper by 1970 Nobel laureate in Physics, Hannes Alfvén. From May 10 to May 12, 1999, NASA's Advanced Composition Explorer (ACE) and WIND spacecraft observed a 98% decrease of solar wind density. This allowed energetic electrons from the Sun to flow to Earth in narrow beams known as "strahl", which caused a highly unusual "polar rain" event, in which a visible aurora appeared over the North Pole. In addition, Earth's magnetosphere increased to between 5 and 6 times its normal size. The STEREO mission was launched in 2006 to study coronal mass ejections and the solar corona, using stereoscopy from two widely separated imaging systems. Each STEREO spacecraft carried two heliospheric imagers: highly sensitive wide-field cameras capable of imaging the solar wind itself, via Thomson scattering of sunlight off of free electrons. Movies from STEREO revealed the solar wind near the ecliptic, as a large-scale turbulent flow. On December 13, 2010, Voyager 1 determined that the velocity of the solar wind, at its location 10.8 billion miles (17.4 billion kilometres) from Earth had slowed to zero. "We have gotten to the point where the wind from the Sun, which until now has always had an outward motion, is no longer moving outward; it is only moving sideways so that it can end up going down the tail of the heliosphere, which is a comet-shaped-like object", said Voyager project scientist Edward Stone. In 2018, NASA launched the Parker Solar Probe, named in honor of American astrophysicist Eugene Parker, on a mission to study the structure and dynamics of the solar corona, in an attempt to understand the mechanisms that cause particles to be heated and accelerated as solar wind. During its seven-year mission, the probe will make twenty-four orbits of the Sun, passing further into the corona with each orbit's perihelion, ultimately passing within 0.04 astronomical units of the Sun's surface. It is the first NASA spacecraft named for a living person, and Parker, at age 91, was on hand to observe the launch. Acceleration mechanism While early models of the solar wind relied primarily on thermal energy to accelerate the material, by the 1960s it was clear that thermal acceleration alone cannot account for the high speed of solar wind. An additional unknown acceleration mechanism is required and likely relates to magnetic fields in the solar atmosphere. The Sun's corona, or extended outer layer, is a region of plasma that is heated to over a megakelvin. As a result of thermal collisions, the particles within the inner corona have a range and distribution of speeds described by a Maxwellian distribution. The mean velocity of these particles is about 145 km/s, which is well below the solar escape velocity of 618 km/s. However, a few of the particles achieve energies sufficient to reach the terminal velocity of 400 km/s, which allows them to feed the solar wind. At the same temperature, electrons, due to their much smaller mass, reach escape velocity and build up an electric field that further accelerates ions away from the Sun. The total number of particles carried away from the Sun by the solar wind is about 1.3×1036 per second. Thus, the total mass loss each year is about (2–3)×10−14 solar masses, or about 1.3–1.9 million tonnes per second. This is equivalent to losing a mass equal to the Earth every 150 million years. However, since the Sun's formation, only about 0.01% of its initial mass has been lost through the solar wind. Other stars have much stronger stellar winds that result in significantly higher mass-loss rates. In March 2023 solar extreme ultraviolet observations have shown that small-scale magnetic reconnection could be a driver of the solar wind as a swarm of nanoflares in the form omnipresent jetting activity a.k.a. jetlets producing short-lived streams of hot plasma and Alfvén waves at the base of the solar corona. This activity could also be connected to the magnetic switchback phenomenon of the solar wind. Properties and structure The solar wind is observed to exist in two fundamental states, termed the slow solar wind and the fast solar wind, though their differences extend well beyond their speeds. In near-Earth space, the slow solar wind is observed to have a velocity of 300–500 km/s, a temperature of ~100 kilokelvin and a composition that is a close match to the corona. By contrast, the fast solar wind has a typical velocity of 750 km/s, a temperature of 800 kilokelvin[citation needed] and it nearly matches the composition of the Sun's photosphere. The slow solar wind is twice as dense and more variable in nature than the fast solar wind. The slow solar wind appears to originate from a region around the Sun's equatorial belt that is known as the "streamer belt", where coronal streamers are produced by magnetic flux open to the heliosphere draping over closed magnetic loops.[clarification needed] The exact coronal structures involved in slow solar wind formation and the method by which the material is released is still under debate. Observations of the Sun between 1996 and 2001 showed that emission of the slow solar wind occurred at latitudes up to 30–35° during the solar minimum (the period of lowest solar activity), then expanded toward the poles as the solar cycle approached maximum. At solar maximum, the poles were also emitting a slow solar wind. The fast solar wind originates from coronal holes, which are funnel-like regions of open field lines in the Sun's magnetic field. Such open lines are particularly prevalent around the Sun's magnetic poles. The plasma source is small magnetic fields created by convection cells in the solar atmosphere. These fields confine the plasma and transport it into the narrow necks of the coronal funnels, which are located only 20,000 km above the photosphere. The plasma is released into the funnel when these magnetic field lines reconnect. Near the Earth's orbit at 1 astronomical unit (AU) the plasma flows at speeds ranging from 250 to 750 km/s with a density ranging between 3 and 10 particles per cubic centimeter and temperature ranging from 104 to 106 kelvin. On average, the plasma density decreases with the square of the distance from the Sun,: Sect. 2.4 while the velocity decreases and flattens out at 1 AU.: Fig. 5 Voyager 1 and Voyager 2 reported plasma density n between 0.001 and 0.005 particles/cm3 at distances of 80 to 120 AU, increasing rapidly beyond 120 AU at heliopause to between 0.05 and 0.2 particles/cm3. At 1 AU, the wind exerts a pressure typically in the range of 1–6 nPa ((1–6)×10−9 N/m2), although it can readily vary outside that range. The ram pressure is a function of wind speed and density. The formula is where mp is the proton mass, pressure P is in Pa (pascals), n is the density in particles/cm3 and V is the speed in km/s of the solar wind. Both the fast and slow solar wind can be interrupted by large, fast-moving bursts of plasma called coronal mass ejections, or CMEs. CMEs are caused by a release of magnetic energy at the Sun. CMEs are often called "solar storms" or "space storms" in the popular media. They are sometimes, but not always, associated with solar flares, which are another manifestation of magnetic energy release at the Sun. CMEs cause shock waves in the thin plasma of the heliosphere, launching electromagnetic waves and accelerating particles (mostly protons and electrons) to form showers of ionizing radiation that precede the CME. When a CME impacts the Earth's magnetosphere, it temporarily deforms the Earth's magnetic field, changing the direction of compass needles and inducing large electrical ground currents in Earth itself; this is called a geomagnetic storm and it is a global phenomenon. CME impacts can induce magnetic reconnection in Earth's magnetotail (the midnight side of the magnetosphere); this launches protons and electrons downward toward Earth's atmosphere, where they form the aurora. CMEs are not the only cause of space weather. Different patches on the Sun are known to give rise to slightly different speeds and densities of wind depending on local conditions. In isolation, each of these different wind streams would form a spiral with a slightly different angle, with fast-moving streams moving out more directly and slow-moving streams wrapping more around the Sun. Fast-moving streams tend to overtake slower streams that originate westward of them on the Sun, forming turbulent co-rotating interaction regions that give rise to wave motions and accelerated particles, and that affect Earth's magnetosphere in the same way as, but more gently than, CMEs. CMEs have a complex internal structure, with a highly turbulent region of hot and compressed plasma (known as sheath) preceding an arrival of relatively cold and strongly magnetized plasma region (known as magnetic cloud or ejecta). Sheath and ejecta have very different impact on the Earth's magnetosphere and on various space weather phenomena, such as the behavior of Van Allen radiation belts. Magnetic switchbacks are sudden reversals in the magnetic field of the solar wind. They can also be described as traveling disturbances in the solar wind that caused the magnetic field to bend back on itself. They were first observed by the NASA–ESA mission Ulysses, the first spacecraft to fly over the Sun's poles. Parker Solar Probe observed first switchbacks in 2018. Solar System effects Over the Sun's lifetime, the interaction of its surface layers with the escaping solar wind has significantly decreased its surface rotation rate. The wind is considered responsible for comets' tails, along with the Sun's radiation. The solar wind contributes to fluctuations in celestial radio waves observed on the Earth, through an effect called interplanetary scintillation. Where the solar wind intersects with a planet that has a well-developed magnetic field (such as Earth, Jupiter or Saturn), the particles are deflected by the Lorentz force. This region, known as the magnetosphere, causes the particles to travel around the planet rather than bombarding the atmosphere or surface. The magnetosphere is roughly shaped like a hemisphere on the side facing the Sun, then is drawn out in a long wake on the opposite side. The boundary of this region is called the magnetopause, and some of the particles are able to penetrate the magnetosphere through this region by partial reconnection of the magnetic field lines. The solar wind is responsible for the overall shape of Earth's magnetosphere. Fluctuations in its speed, density, direction, and entrained magnetic field strongly affect Earth's local space environment. For example, the levels of ionizing radiation and radio interference can vary by factors of hundreds to thousands; and the shape and location of the magnetopause and bow shock wave upstream of it can change by several Earth radii, exposing geosynchronous satellites to the direct solar wind. These phenomena are collectively called space weather. From the European Space Agency's Cluster mission, a new study has taken place that proposes that it is easier for the solar wind to infiltrate the magnetosphere than previously believed. A group of scientists directly observed the existence of certain waves in the solar wind that were not expected. A recent study shows that these waves enable incoming charged particles of solar wind to breach the magnetopause. This suggests that the magnetic bubble forms more as a filter than a continuous barrier. This latest discovery occurred through the distinctive arrangement of the four identical Cluster spacecraft, which fly in a controlled configuration through near-Earth space. As they sweep from the magnetosphere into interplanetary space and back again, the fleet provides exceptional three-dimensional insights on the phenomena that connect the sun to Earth. The research characterised variances in formation of the interplanetary magnetic field (IMF) largely influenced by Kelvin–Helmholtz instability (which occur at the interface of two fluids) as a result of differences in thickness and numerous other characteristics of the boundary layer. Experts believe that this was the first occasion that the appearance of Kelvin–Helmholtz waves at the magnetopause had been displayed at high latitude downward orientation of the IMF. These waves are being seen in unforeseen places under solar wind conditions that were formerly believed to be undesired for their generation. These discoveries show how Earth's magnetosphere can be penetrated by solar particles under specific IMF circumstances. The findings are also relevant to studies of magnetospheric progressions around other planetary bodies. This study suggests that Kelvin–Helmholtz waves can be a somewhat common, and possibly constant, instrument for the entrance of solar wind into terrestrial magnetospheres under various IMF orientations. The solar wind affects other incoming cosmic rays interacting with planetary atmospheres. Moreover, planets with a weak or non-existent magnetosphere are subject to atmospheric stripping by the solar wind. Venus, the nearest and most similar planet to Earth, has 100 times denser atmosphere, with little or no geo-magnetic field. Space probes discovered a comet-like tail that extends to Earth's orbit. Earth itself is largely protected from the solar wind by its magnetic field, which deflects most of the charged particles; however, some of the charged particles are trapped in the Van Allen radiation belt. A smaller number of particles from the solar wind manage to travel, as though on an electromagnetic energy transmission line, to the Earth's upper atmosphere and ionosphere in the auroral zones. The only time the solar wind is observable on the Earth is when it is strong enough to produce phenomena such as the aurora and geomagnetic storms. Bright auroras strongly heat the ionosphere, causing its plasma to expand into the magnetosphere, increasing the size of the plasma geosphere and injecting atmospheric matter into the solar wind. Geomagnetic storms result when the pressure of plasmas contained inside the magnetosphere is sufficiently large to inflate and thereby distort the geomagnetic field. Although Mars is larger than Mercury and four times farther from the Sun, it is thought that the solar wind has stripped away up to a third of its original atmosphere, leaving a layer 1/100 as dense as the Earth's. It is believed the mechanism for this atmospheric stripping is gas caught in bubbles of the magnetic field, which are ripped off by the solar wind. In 2015 the NASA Mars Atmosphere and Volatile Evolution (MAVEN) mission measured the rate of atmospheric stripping caused by the magnetic field carried by the solar wind as it flows past Mars, which generates an electric field, much as a turbine on Earth can be used to generate electricity. This electric field accelerates electrically charged gas atoms, called ions, in Mars's upper atmosphere and shoots them into space. The MAVEN mission measured the rate of atmospheric stripping at about 100 grams (≈1/4 lb) per second. Mercury, the nearest planet to the Sun, bears the full brunt of the solar wind, and since its atmosphere is vestigial and transient, its surface is bathed in radiation. Mercury has an intrinsic magnetic field, so under normal solar wind conditions, the solar wind cannot penetrate its magnetosphere and particles only reach the surface in the cusp regions. During coronal mass ejections, however, the magnetopause may get pressed into the surface of the planet, and under these conditions, the solar wind may interact freely with the planetary surface. The Earth's Moon has no atmosphere or intrinsic magnetic field, and consequently its surface is bombarded with the full solar wind. The Project Apollo missions deployed passive aluminum collectors in an attempt to sample the solar wind, and lunar soil returned for study confirmed that the lunar regolith is enriched in atomic nuclei deposited from the solar wind. These elements may prove useful resources for future lunar expeditions. Limits The Alfvén surface is the boundary separating the corona from the solar wind defined as where the coronal plasma's Alfvén speed and the large-scale solar wind speed are equal. Researchers were unsure exactly where the Alfvén critical surface of the Sun lay. Based on remote images of the corona, estimates had put it somewhere between 10 and 20 solar radii from the surface of the Sun. On April 28, 2021, during its eighth flyby of the Sun, NASA's Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii that indicated that it penetrated the Alfvén surface. The solar wind "blows a bubble" in the interstellar medium (the rarefied hydrogen and helium gas that permeates the galaxy). The point where the solar wind's strength is no longer great enough to push back the interstellar medium is known as the heliopause and is often considered to be the outer border of the Solar System. The distance to the heliopause is not precisely known and probably depends on the current velocity of the solar wind and the local density of the interstellar medium, but it is far outside Pluto's orbit. Scientists hope to gain perspective on the heliopause from data acquired through the Interstellar Boundary Explorer (IBEX) mission, launched in October 2008. The heliopause is noted as one of the ways of defining the extent of the Solar System, along with the Kuiper Belt and the radius at which the Sun's gravitational influence is matched by other stars. The maximum extent of that influence has been estimated at between 50,000 astronomical units (7,500 billion kilometres; 0.79 light-years) and 2 light-years (130,000 au), compared to the heliopause (the outer boundary of the heliosphere), which has been detected at about 120 au (18,000 million km) by the Voyager 1 spacecraft. The Voyager 2 spacecraft crossed the termination shock more than five times between August 30 and December 10, 2007. Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5 billion km (90 au) distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the termination shock into the heliosheath and onward toward the interstellar medium. See also References Further reading External links |
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Contents Elon Musk Elon Reeve Musk (/ˈiːlɒn/ EE-lon; born June 28, 1971) is a businessman and entrepreneur known for his leadership of Tesla, SpaceX, Twitter, and xAI. Musk has been the wealthiest person in the world since 2025; as of February 2026,[update] Forbes estimates his net worth to be around US$852 billion. Born into a wealthy family in Pretoria, South Africa, Musk emigrated in 1989 to Canada; he has Canadian citizenship since his mother was born there. He received bachelor's degrees in 1997 from the University of Pennsylvania before moving to California to pursue business ventures. In 1995, Musk co-founded the software company Zip2. Following its sale in 1999, he co-founded X.com, an online payment company that later merged to form PayPal, which was acquired by eBay in 2002. Musk also became an American citizen in 2002. In 2002, Musk founded the space technology company SpaceX, becoming its CEO and chief engineer; the company has since led innovations in reusable rockets and commercial spaceflight. Musk joined the automaker Tesla as an early investor in 2004 and became its CEO and product architect in 2008; it has since become a leader in electric vehicles. In 2015, he co-founded OpenAI to advance artificial intelligence (AI) research, but later left; growing discontent with the organization's direction and their leadership in the AI boom in the 2020s led him to establish xAI, which became a subsidiary of SpaceX in 2026. In 2022, he acquired the social network Twitter, implementing significant changes, and rebranding it as X in 2023. His other businesses include the neurotechnology company Neuralink, which he co-founded in 2016, and the tunneling company the Boring Company, which he founded in 2017. In November 2025, a Tesla pay package worth $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Musk was the largest donor in the 2024 U.S. presidential election, where he supported Donald Trump. After Trump was inaugurated as president in early 2025, Musk served as Senior Advisor to the President and as the de facto head of the Department of Government Efficiency (DOGE). After a public feud with Trump, Musk left the Trump administration and returned to managing his companies. Musk is a supporter of global far-right figures, causes, and political parties. His political activities, views, and statements have made him a polarizing figure. Musk has been criticized for COVID-19 misinformation, promoting conspiracy theories, and affirming antisemitic, racist, and transphobic comments. His acquisition of Twitter was controversial due to a subsequent increase in hate speech and the spread of misinformation on the service, following his pledge to decrease censorship. His role in the second Trump administration attracted public backlash, particularly in response to DOGE. The emails he sent to Jeffrey Epstein are included in the Epstein files, which were published between 2025–26 and became a topic of worldwide debate. Early life Elon Reeve Musk was born on June 28, 1971, in Pretoria, South Africa's administrative capital. He is of British and Pennsylvania Dutch ancestry. His mother, Maye (née Haldeman), is a model and dietitian born in Saskatchewan, Canada, and raised in South Africa. Musk therefore holds both South African and Canadian citizenship from birth. His father, Errol Musk, is a South African electromechanical engineer, pilot, sailor, consultant, emerald dealer, and property developer, who partly owned a rental lodge at Timbavati Private Nature Reserve. His maternal grandfather, Joshua N. Haldeman, who died in a plane crash when Elon was a toddler, was an American-born Canadian chiropractor, aviator and political activist in the technocracy movement who moved to South Africa in 1950. Elon has a younger brother, Kimbal, a younger sister, Tosca, and four paternal half-siblings. Musk was baptized as a child in the Anglican Church of Southern Africa. Despite both Elon and Errol previously stating that Errol was a part owner of a Zambian emerald mine, in 2023, Errol recounted that the deal he made was to receive "a portion of the emeralds produced at three small mines". Errol was elected to the Pretoria City Council as a representative of the anti-apartheid Progressive Party and has said that his children shared their father's dislike of apartheid. After his parents divorced in 1979, Elon, aged around 9, chose to live with his father because Errol Musk had an Encyclopædia Britannica and a computer. Elon later regretted his decision and became estranged from his father. Elon has recounted trips to a wilderness school that he described as a "paramilitary Lord of the Flies" where "bullying was a virtue" and children were encouraged to fight over rations. In one incident, after an altercation with a fellow pupil, Elon was thrown down concrete steps and beaten severely, leading to him being hospitalized for his injuries. Elon described his father berating him after he was discharged from the hospital. Errol denied berating Elon and claimed, "The [other] boy had just lost his father to suicide, and Elon had called him stupid. Elon had a tendency to call people stupid. How could I possibly blame that child?" Elon was an enthusiastic reader of books, and had attributed his success in part to having read The Lord of the Rings, the Foundation series, and The Hitchhiker's Guide to the Galaxy. At age ten, he developed an interest in computing and video games, teaching himself how to program from the VIC-20 user manual. At age twelve, Elon sold his BASIC-based game Blastar to PC and Office Technology magazine for approximately $500 (equivalent to $1,600 in 2025). Musk attended Waterkloof House Preparatory School, Bryanston High School, and then Pretoria Boys High School, where he graduated. Musk was a decent but unexceptional student, earning a 61/100 in Afrikaans and a B on his senior math certification. Musk applied for a Canadian passport through his Canadian-born mother to avoid South Africa's mandatory military service, which would have forced him to participate in the apartheid regime, as well as to ease his path to immigration to the United States. While waiting for his application to be processed, he attended the University of Pretoria for five months. Musk arrived in Canada in June 1989, connected with a second cousin in Saskatchewan, and worked odd jobs, including at a farm and a lumber mill. In 1990, he entered Queen's University in Kingston, Ontario. Two years later, he transferred to the University of Pennsylvania, where he studied until 1995. Although Musk has said that he earned his degrees in 1995, the University of Pennsylvania did not award them until 1997 – a Bachelor of Arts in physics and a Bachelor of Science in economics from the university's Wharton School. He reportedly hosted large, ticketed house parties to help pay for tuition, and wrote a business plan for an electronic book-scanning service similar to Google Books. In 1994, Musk held two internships in Silicon Valley: one at energy storage startup Pinnacle Research Institute, which investigated electrolytic supercapacitors for energy storage, and another at Palo Alto–based startup Rocket Science Games. In 1995, he was accepted to a graduate program in materials science at Stanford University, but did not enroll. Musk decided to join the Internet boom of the 1990s, applying for a job at Netscape, to which he reportedly never received a response. The Washington Post reported that Musk lacked legal authorization to remain and work in the United States after failing to enroll at Stanford. In response, Musk said he was allowed to work at that time and that his student visa transitioned to an H1-B. According to numerous former business associates and shareholders, Musk said he was on a student visa at the time. Business career In 1995, Musk, his brother Kimbal, and Greg Kouri founded the web software company Zip2 with funding from a group of angel investors. They housed the venture at a small rented office in Palo Alto. Replying to Rolling Stone, Musk denounced the notion that they started their company with funds borrowed from Errol Musk, but in a tweet, he recognized that his father contributed 10% of a later funding round. The company developed and marketed an Internet city guide for the newspaper publishing industry, with maps, directions, and yellow pages. According to Musk, "The website was up during the day and I was coding it at night, seven days a week, all the time." To impress investors, Musk built a large plastic structure around a standard computer to create the impression that Zip2 was powered by a small supercomputer. The Musk brothers obtained contracts with The New York Times and the Chicago Tribune, and persuaded the board of directors to abandon plans for a merger with CitySearch. Musk's attempts to become CEO were thwarted by the board. Compaq acquired Zip2 for $307 million in cash in February 1999 (equivalent to $590,000,000 in 2025), and Musk received $22 million (equivalent to $43,000,000 in 2025) for his 7-percent share. In 1999, Musk co-founded X.com, an online financial services and e-mail payment company. The startup was one of the first federally insured online banks, and, in its initial months of operation, over 200,000 customers joined the service. The company's investors regarded Musk as inexperienced and replaced him with Intuit CEO Bill Harris by the end of the year. The following year, X.com merged with online bank Confinity to avoid competition. Founded by Max Levchin and Peter Thiel, Confinity had its own money-transfer service, PayPal, which was more popular than X.com's service. Within the merged company, Musk returned as CEO. Musk's preference for Microsoft software over Unix created a rift in the company and caused Thiel to resign. Due to resulting technological issues and lack of a cohesive business model, the board ousted Musk and replaced him with Thiel in 2000.[b] Under Thiel, the company focused on the PayPal service and was renamed PayPal in 2001. In 2002, PayPal was acquired by eBay for $1.5 billion (equivalent to $2,700,000,000 in 2025) in stock, of which Musk—the largest shareholder with 11.72% of shares—received $175.8 million (equivalent to $320,000,000 in 2025). In 2017, Musk purchased the domain X.com from PayPal for an undisclosed amount, stating that it had sentimental value. In 2001, Musk became involved with the nonprofit Mars Society and discussed funding plans to place a growth-chamber for plants on Mars. Seeking a way to launch the greenhouse payloads into space, Musk made two unsuccessful trips to Moscow to purchase intercontinental ballistic missiles (ICBMs) from Russian companies NPO Lavochkin and Kosmotras. Musk instead decided to start a company to build affordable rockets. With $100 million of his early fortune, (equivalent to $180,000,000 in 2025) Musk founded SpaceX in May 2002 and became the company's CEO and Chief Engineer. SpaceX attempted its first launch of the Falcon 1 rocket in 2006. Although the rocket failed to reach Earth orbit, it was awarded a Commercial Orbital Transportation Services program contract from NASA, then led by Mike Griffin. After two more failed attempts that nearly caused Musk to go bankrupt, SpaceX succeeded in launching the Falcon 1 into orbit in 2008. Later that year, SpaceX received a $1.6 billion NASA contract (equivalent to $2,400,000,000 in 2025) for Falcon 9-launched Dragon spacecraft flights to the International Space Station (ISS), replacing the Space Shuttle after its 2011 retirement. In 2012, the Dragon vehicle docked with the ISS, a first for a commercial spacecraft. Working towards its goal of reusable rockets, in 2015 SpaceX successfully landed the first stage of a Falcon 9 on a land platform. Later landings were achieved on autonomous spaceport drone ships, an ocean-based recovery platform. In 2018, SpaceX launched the Falcon Heavy; the inaugural mission carried Musk's personal Tesla Roadster as a dummy payload. Since 2019, SpaceX has been developing Starship, a reusable, super heavy-lift launch vehicle intended to replace the Falcon 9 and Falcon Heavy. In 2020, SpaceX launched its first crewed flight, the Demo-2, becoming the first private company to place astronauts into orbit and dock a crewed spacecraft with the ISS. In 2024, NASA awarded SpaceX an $843 million (equivalent to $865,000,000 in 2025) contract to build a spacecraft that NASA will use to deorbit the ISS at the end of its lifespan. In 2015, SpaceX began development of the Starlink constellation of low Earth orbit satellites to provide satellite Internet access. After the launch of prototype satellites in 2018, the first large constellation was deployed in May 2019. As of May 2025[update], over 7,600 Starlink satellites are operational, comprising 65% of all operational Earth satellites. The total cost of the decade-long project to design, build, and deploy the constellation was estimated by SpaceX in 2020 to be $10 billion (equivalent to $12,000,000,000 in 2025).[c] During the Russian invasion of Ukraine, Musk provided free Starlink service to Ukraine, permitting Internet access and communication at a yearly cost to SpaceX of $400 million (equivalent to $440,000,000 in 2025). However, Musk refused to block Russian state media on Starlink. In 2023, Musk denied Ukraine's request to activate Starlink over Crimea to aid an attack against the Russian navy, citing fears of a nuclear response. Tesla, Inc., originally Tesla Motors, was incorporated in July 2003 by Martin Eberhard and Marc Tarpenning. Both men played active roles in the company's early development prior to Musk's involvement. Musk led the Series A round of investment in February 2004; he invested $6.35 million (equivalent to $11,000,000 in 2025), became the majority shareholder, and joined Tesla's board of directors as chairman. Musk took an active role within the company and oversaw Roadster product design, but was not deeply involved in day-to-day business operations. Following a series of escalating conflicts in 2007 and the 2008 financial crisis, Eberhard was ousted from the firm.[page needed] Musk assumed leadership of the company as CEO and product architect in 2008. A 2009 lawsuit settlement with Eberhard designated Musk as a Tesla co-founder, along with Tarpenning and two others. Tesla began delivery of the Roadster, an electric sports car, in 2008. With sales of about 2,500 vehicles, it was the first mass production all-electric car to use lithium-ion battery cells. Under Musk, Tesla has since launched several well-selling electric vehicles, including the four-door sedan Model S (2012), the crossover Model X (2015), the mass-market sedan Model 3 (2017), the crossover Model Y (2020), and the pickup truck Cybertruck (2023). In May 2020, Musk resigned as chairman of the board as part of the settlement of a lawsuit from the SEC over him tweeting that funding had been "secured" for potentially taking Tesla private. The company has also constructed multiple lithium-ion battery and electric vehicle factories, called Gigafactories. Since its initial public offering in 2010, Tesla stock has risen significantly; it became the most valuable carmaker in summer 2020, and it entered the S&P 500 later that year. In October 2021, it reached a market capitalization of $1 trillion (equivalent to $1,200,000,000,000 in 2025), the sixth company in U.S. history to do so. Musk provided the initial concept and financial capital for SolarCity, which his cousins Lyndon and Peter Rive founded in 2006. By 2013, SolarCity was the second largest provider of solar power systems in the United States. In 2014, Musk promoted the idea of SolarCity building an advanced production facility in Buffalo, New York, triple the size of the largest solar plant in the United States. Construction of the factory started in 2014 and was completed in 2017. It operated as a joint venture with Panasonic until early 2020. Tesla acquired SolarCity for $2 billion in 2016 (equivalent to $2,700,000,000 in 2025) and merged it with its battery unit to create Tesla Energy. The deal's announcement resulted in a more than 10% drop in Tesla's stock price; at the time, SolarCity was facing liquidity issues. Multiple shareholder groups filed a lawsuit against Musk and Tesla's directors, stating that the purchase of SolarCity was done solely to benefit Musk and came at the expense of Tesla and its shareholders. Tesla directors settled the lawsuit in January 2020, leaving Musk the sole remaining defendant. Two years later, the court ruled in Musk's favor. In 2016, Musk co-founded Neuralink, a neurotechnology startup, with an investment of $100 million. Neuralink aims to integrate the human brain with artificial intelligence (AI) by creating devices that are embedded in the brain. Such technology could enhance memory or allow the devices to communicate with software. The company also hopes to develop devices to treat neurological conditions like spinal cord injuries. In 2022, Neuralink announced that clinical trials would begin by the end of the year. In September 2023, the Food and Drug Administration approved Neuralink to initiate six-year human trials. Neuralink has conducted animal testing on macaques at the University of California, Davis. In 2021, the company released a video in which a macaque played the video game Pong via a Neuralink implant. The company's animal trials—which have caused the deaths of some monkeys—have led to claims of animal cruelty. The Physicians Committee for Responsible Medicine has alleged that Neuralink violated the Animal Welfare Act. Employees have complained that pressure from Musk to accelerate development has led to botched experiments and unnecessary animal deaths. In 2022, a federal probe was launched into possible animal welfare violations by Neuralink.[needs update] In 2017, Musk founded the Boring Company to construct tunnels; he also revealed plans for specialized, underground, high-occupancy vehicles that could travel up to 150 miles per hour (240 km/h) and thus circumvent above-ground traffic in major cities. Early in 2017, the company began discussions with regulatory bodies and initiated construction of a 30-foot (9.1 m) wide, 50-foot (15 m) long, and 15-foot (4.6 m) deep "test trench" on the premises of SpaceX's offices, as that required no permits. The Los Angeles tunnel, less than two miles (3.2 km) in length, debuted to journalists in 2018. It used Tesla Model Xs and was reported to be a rough ride while traveling at suboptimal speeds. Two tunnel projects announced in 2018, in Chicago and West Los Angeles, have been canceled. A tunnel beneath the Las Vegas Convention Center was completed in early 2021. Local officials have approved further expansions of the tunnel system. April 14, 2022 In early 2017, Musk expressed interest in buying Twitter and had questioned the platform's commitment to freedom of speech. By 2022, Musk had reached 9.2% stake in the company, making him the largest shareholder.[d] Musk later agreed to a deal that would appoint him to Twitter's board of directors and prohibit him from acquiring more than 14.9% of the company. Days later, Musk made a $43 billion offer to buy Twitter. By the end of April Musk had successfully concluded his bid for approximately $44 billion. This included approximately $12.5 billion in loans and $21 billion in equity financing. Having backtracked on his initial decision, Musk bought the company on October 27, 2022. Immediately after the acquisition, Musk fired several top Twitter executives including CEO Parag Agrawal; Musk became the CEO instead. Under Elon Musk, Twitter instituted monthly subscriptions for a "blue check", and laid off a significant portion of the company's staff. Musk lessened content moderation and hate speech also increased on the platform after his takeover. In late 2022, Musk released internal documents relating to Twitter's moderation of Hunter Biden's laptop controversy in the lead-up to the 2020 presidential election. Musk also promised to step down as CEO after a Twitter poll, and five months later, Musk stepped down as CEO and transitioned his role to executive chairman and chief technology officer (CTO). Despite Musk stepping down as CEO, X continues to struggle with challenges such as viral misinformation, hate speech, and antisemitism controversies. Musk has been accused of trying to silence some of his critics such as Twitch streamer Asmongold, who criticized him during one of his streams. Musk has been accused of removing their accounts' blue checkmarks, which hinders visibility and is considered a form of shadow banning, or suspending their accounts without justification. Other activities In August 2013, Musk announced plans for a version of a vactrain, and assigned engineers from SpaceX and Tesla to design a transport system between Greater Los Angeles and the San Francisco Bay Area, at an estimated cost of $6 billion. Later that year, Musk unveiled the concept, dubbed the Hyperloop, intended to make travel cheaper than any other mode of transport for such long distances. In December 2015, Musk co-founded OpenAI, a not-for-profit artificial intelligence (AI) research company aiming to develop artificial general intelligence, intended to be safe and beneficial to humanity. Musk pledged $1 billion of funding to the company, and initially gave $50 million. In 2018, Musk left the OpenAI board. Since 2018, OpenAI has made significant advances in machine learning. In July 2023, Musk launched the artificial intelligence company xAI, which aims to develop a generative AI program that competes with existing offerings like OpenAI's ChatGPT. Musk obtained funding from investors in SpaceX and Tesla, and xAI hired engineers from Google and OpenAI. December 16, 2022 Musk uses a private jet owned by Falcon Landing LLC, a SpaceX-linked company, and acquired a second jet in August 2020. His heavy use of the jets and the consequent fossil fuel usage have received criticism. Musk's flight usage is tracked on social media through ElonJet. In December 2022, Musk banned the ElonJet account on Twitter, and made temporary bans on the accounts of journalists that posted stories regarding the incident, including Donie O'Sullivan, Keith Olbermann, and journalists from The New York Times, The Washington Post, CNN, and The Intercept. In October 2025, Musk's company xAI launched Grokipedia, an AI-generated online encyclopedia that he promoted as an alternative to Wikipedia. Articles on Grokipedia are generated and reviewed by xAI's Grok chatbot. Media coverage and academic analysis described Grokipedia as frequently reusing Wikipedia content but framing contested political and social topics in line with Musk's own views and right-wing narratives. A study by Cornell University researchers and NBC News stated that Grokipedia cites sources that are blacklisted or considered "generally unreliable" on Wikipedia, for example, the conspiracy site Infowars and the neo-Nazi forum Stormfront. Wired, The Guardian and Time criticized Grokipedia for factual errors and for presenting Musk himself in unusually positive terms while downplaying controversies. Politics Musk is an outlier among business leaders who typically avoid partisan political advocacy. Musk was a registered independent voter when he lived in California. Historically, he has donated to both Democrats and Republicans, many of whom serve in states in which he has a vested interest. Since 2022, his political contributions have mostly supported Republicans, with his first vote for a Republican going to Mayra Flores in the 2022 Texas's 34th congressional district special election. In 2024, he started supporting international far-right political parties, activists, and causes, and has shared misinformation and numerous conspiracy theories. Since 2024, his views have been generally described as right-wing. Musk supported Barack Obama in 2008 and 2012, Hillary Clinton in 2016, Joe Biden in 2020, and Donald Trump in 2024. In the 2020 Democratic Party presidential primaries, Musk endorsed candidate Andrew Yang and expressed support for Yang's proposed universal basic income, and endorsed Kanye West's 2020 presidential campaign. In 2021, Musk publicly expressed opposition to the Build Back Better Act, a $3.5 trillion legislative package endorsed by Joe Biden that ultimately failed to pass due to unanimous opposition from congressional Republicans and several Democrats. In 2022, gave over $50 million to Citizens for Sanity, a conservative political action committee. In 2023, he supported Republican Ron DeSantis for the 2024 U.S. presidential election, giving $10 million to his campaign, and hosted DeSantis's campaign announcement on a Twitter Spaces event. From June 2023 to January 2024, Musk hosted a bipartisan set of X Spaces with Republican and Democratic candidates, including Robert F. Kennedy Jr., Vivek Ramaswamy, and Dean Phillips. In October 2025, former vice-president Kamala Harris commented that it was a mistake from the Democratic side to not invite Musk to a White House electric vehicle event organized in August 2021 and featuring executives from General Motors, Ford and Stellantis, despite Tesla being "the major American manufacturer of extraordinary innovation in this space." Fortune remarked that this was a nod to United Auto Workers and organized labor. Harris said presidents should put aside political loyalties when it came to recognizing innovation, and guessed that the non-invitation impacted Musk's perspective. Fortune noted that, at the time, Musk said, "Yeah, seems odd that Tesla wasn't invited." A month later, he criticized Biden as "not the friendliest administration." Jacob Silverman, author of the book Gilded Rage: Elon Musk and the Radicalization of Silicon Valley, said that the tech industry represented by Musk, Thiel, Andreessen and other capitalists, actually flourished under Biden, but the tech leaders chose Trump for their common ground on cultural issues. By early 2024, Musk had become a vocal and financial supporter of Donald Trump. In July 2024, minutes after the attempted assassination of Donald Trump, Musk endorsed him for president saying; "I fully endorse President Trump and hope for his rapid recovery." During the presidential campaign, Musk joined Trump on stage at a campaign rally, and during the campaign promoted conspiracy theories and falsehoods about Democrats, election fraud and immigration, in support of Trump. Musk was the largest individual donor of the 2024 election. In 2025, Musk contributed $19 million to the Wisconsin Supreme Court race, hoping to influence the state's future redistricting efforts and its regulations governing car manufacturers and dealers. In 2023, Musk said he shunned the World Economic Forum because it was boring. The organization commented that they had not invited him since 2015. He has participated in Dialog, dubbed "Tech Bilderberg" and organized by Peter Thiel and Auren Hoffman, though. Musk's international political actions and comments have come under increasing scrutiny and criticism, especially from the governments and leaders of France, Germany, Norway, Spain and the United Kingdom, particularly due to his position in the U.S. government as well as ownership of X. An NBC News analysis found he had boosted far-right political movements to cut immigration and curtail regulation of business in at least 18 countries on six continents since 2023. During his speech after the second inauguration of Donald Trump, Musk twice made a gesture interpreted by many as a Nazi or a fascist Roman salute.[e] He thumped his right hand over his heart, fingers spread wide, and then extended his right arm out, emphatically, at an upward angle, palm down and fingers together. He then repeated the gesture to the crowd behind him. As he finished the gestures, he said to the crowd, "My heart goes out to you. It is thanks to you that the future of civilization is assured." It was widely condemned as an intentional Nazi salute in Germany, where making such gestures is illegal. The Anti-Defamation League said it was not a Nazi salute, but other Jewish organizations disagreed and condemned the salute. American public opinion was divided on partisan lines as to whether it was a fascist salute. Musk dismissed the accusations of Nazi sympathies, deriding them as "dirty tricks" and a "tired" attack. Neo-Nazi and white supremacist groups celebrated it as a Nazi salute. Multiple European political parties demanded that Musk be banned from entering their countries. The concept of DOGE emerged in a discussion between Musk and Donald Trump, and in August 2024, Trump committed to giving Musk an advisory role, with Musk accepting the offer. In November and December 2024, Musk suggested that the organization could help to cut the U.S. federal budget, consolidate the number of federal agencies, and eliminate the Consumer Financial Protection Bureau, and that its final stage would be "deleting itself". In January 2025, the organization was created by executive order, and Musk was designated a "special government employee". Musk led the organization and was a senior advisor to the president, although his official role is not clear. In sworn statement during a lawsuit, the director of the White House Office of Administration stated that Musk "is not an employee of the U.S. DOGE Service or U.S. DOGE Service Temporary Organization", "is not the U.S. DOGE Service administrator", and has "no actual or formal authority to make government decisions himself". Trump said two days later that he had put Musk in charge of DOGE. A federal judge has ruled that Musk acted as the de facto leader of DOGE. Musk's role in the second Trump administration, particularly in response to DOGE, has attracted public backlash. He was criticized for his treatment of federal government employees, including his influence over the mass layoffs of the federal workforce. He has prioritized secrecy within the organization and has accused others of violating privacy laws. A Senate report alleged that Musk could avoid up to $2 billion in legal liability as a result of DOGE's actions. In May 2025, Bill Gates accused Musk of "killing the world's poorest children" through his cuts to USAID, which modeling by Boston University estimated had resulted in 300,000 deaths by this time, most of them of children. By November 2025, the estimated death toll had increased to 400,000 children and 200,000 adults. Musk announced on May 28, 2025, that he would depart from the Trump administration as planned when the special government employee's 130 day deadline expired, with a White House official confirming that Musk's offboarding from the Trump administration was already underway. His departure was officially confirmed during a joint Oval Office press conference with Trump on May 30, 2025. @realDonaldTrump is in the Epstein files. That is the real reason they have not been made public. June 5, 2025 After leaving office, Musk criticized the Trump administration's Big Beautiful Bill, calling it a "disgusting abomination" due to its provisions increasing the deficit. A feud began between Musk and Trump, with its most notable event being Musk alleging Trump had ties to sex offender Jeffrey Epstein on X (formerly Twitter) on June 5, 2025. Trump responded on Truth Social stating that Musk went "CRAZY" after the "EV Mandate" was purportedly taken away and threatened to cut Musk's government contracts. Musk then called for a third Trump impeachment. The next day, Trump stated that he did not wish to reconcile with Musk, and added that Musk would face "very serious consequences" if he funds Democratic candidates. On June 11, Musk publicly apologized for the tweets against Trump, saying they "went too far". Views November 6, 2022 Rejecting the conservative label, Musk has described himself as a political moderate, even as his views have become more right-wing over time. His views have been characterized as libertarian and far-right, and after his involvement in European politics, they have received criticism from world leaders such as Emmanuel Macron and Olaf Scholz. Within the context of American politics, Musk supported Democratic candidates up until 2022, at which point he voted for a Republican for the first time. He has stated support for universal basic income, gun rights, freedom of speech, a tax on carbon emissions, and H-1B visas. Musk has expressed concern about issues such as artificial intelligence (AI) and climate change, and has been a critic of wealth tax, short-selling, and government subsidies. An immigrant himself, Musk has been accused of being anti-immigration, and regularly blames immigration policies for illegal immigration. He is also a pronatalist who believes population decline is the biggest threat to civilization, and identifies as a cultural Christian. Musk has long been an advocate for space colonization, especially the colonization of Mars. He has repeatedly pushed for humanity colonizing Mars, in order to become an interplanetary species and lower the risks of human extinction. Musk has promoted conspiracy theories and made controversial statements that have led to accusations of racism, sexism, antisemitism, transphobia, disseminating disinformation, and support of white pride. While describing himself as a "pro-Semite", his comments regarding George Soros and Jewish communities have been condemned by the Anti-Defamation League and the Biden White House. Musk was criticized during the COVID-19 pandemic for making unfounded epidemiological claims, defying COVID-19 lockdowns restrictions, and supporting the Canada convoy protest against vaccine mandates. He has amplified false claims of white genocide in South Africa. Musk has been critical of Israel's actions in the Gaza Strip during the Gaza war, praised China's economic and climate goals, suggested that Taiwan and China should resolve cross-strait relations, and was described as having a close relationship with the Chinese government. In Europe, Musk expressed support for Ukraine in 2022 during the Russian invasion, recommended referendums and peace deals on the annexed Russia-occupied territories, and supported the far-right Alternative for Germany political party in 2024. Regarding British politics, Musk blamed the 2024 UK riots on mass migration and open borders, criticized Prime Minister Keir Starmer for what he described as a "two-tier" policing system, and was subsequently attacked as being responsible for spreading misinformation and amplifying the far-right. He has also voiced his support for far-right activist Tommy Robinson and pledged electoral support for Reform UK. In February 2026, Musk described Spanish Prime Minister Pedro Sánchez as a "tyrant" following Sánchez's proposal to prohibit minors under the age of 16 from accessing social media platforms. Legal affairs In 2018, Musk was sued by the U.S. Securities and Exchange Commission (SEC) for a tweet stating that funding had been secured for potentially taking Tesla private.[f] The securities fraud lawsuit characterized the tweet as false, misleading, and damaging to investors, and sought to bar Musk from serving as CEO of publicly traded companies. Two days later, Musk settled with the SEC, without admitting or denying the SEC's allegations. As a result, Musk and Tesla were fined $20 million each, and Musk was forced to step down for three years as Tesla chairman but was able to remain as CEO. Shareholders filed a lawsuit over the tweet, and in February 2023, a jury found Musk and Tesla not liable. Musk has stated in interviews that he does not regret posting the tweet that triggered the SEC investigation. In 2019, Musk stated in a tweet that Tesla would build half a million cars that year. The SEC reacted by asking a court to hold him in contempt for violating the terms of the 2018 settlement agreement. A joint agreement between Musk and the SEC eventually clarified the previous agreement details, including a list of topics about which Musk needed preclearance. In 2020, a judge blocked a lawsuit that claimed a tweet by Musk regarding Tesla stock price ("too high imo") violated the agreement. Freedom of Information Act (FOIA)-released records showed that the SEC concluded Musk had subsequently violated the agreement twice by tweeting regarding "Tesla's solar roof production volumes and its stock price". In October 2023, the SEC sued Musk over his refusal to testify a third time in an investigation into whether he violated federal law by purchasing Twitter stock in 2022. In February 2024, Judge Laurel Beeler ruled that Musk must testify again. In January 2025, the SEC filed a lawsuit against Musk for securities violations related to his purchase of Twitter. In January 2024, Delaware judge Kathaleen McCormick ruled in a 2018 lawsuit that Musk's $55 billion pay package from Tesla be rescinded. McCormick called the compensation granted by the company's board "an unfathomable sum" that was unfair to shareholders. The Delaware Supreme Court overturned McCormick's decision in December 2025, restoring Musk's compensation package and awarding $1 in nominal damages. Personal life Musk became a U.S. citizen in 2002. From the early 2000s until late 2020, Musk resided in California, where both Tesla and SpaceX were founded. He then relocated to Cameron County, Texas, saying that California had become "complacent" about its economic success. While hosting Saturday Night Live in 2021, Musk stated that he has Asperger syndrome (an outdated term for autism spectrum disorder). When asked about his experience growing up with Asperger's syndrome in a TED2022 conference in Vancouver, Musk stated that "the social cues were not intuitive ... I would just tend to take things very literally ... but then that turned out to be wrong — [people were not] simply saying exactly what they mean, there's all sorts of other things that are meant, and [it] took me a while to figure that out." Musk suffers from back pain and has undergone several spine-related surgeries, including a disc replacement. In 2000, he contracted a severe case of malaria while on vacation in South Africa. Musk has stated he uses doctor-prescribed ketamine for occasional depression and that he doses "a small amount once every other week or something like that"; since January 2024, some media outlets have reported that he takes ketamine, marijuana, LSD, ecstasy, mushrooms, cocaine and other drugs. Musk at first refused to comment on his alleged drug use, before responding that he had not tested positive for drugs, and that if drugs somehow improved his productivity, "I would definitely take them!". The New York Times' investigations revealed Musk's overuse of ketamine and numerous other drugs, as well as strained family relationships and concerns from close associates who have become troubled by his public behavior as he became more involved in political activities and government work. According to The Washington Post, President Trump described Musk as "a big-time drug addict". Through his own label Emo G Records, Musk released a rap track, "RIP Harambe", on SoundCloud in March 2019. The following year, he released an EDM track, "Don't Doubt Ur Vibe", featuring his own lyrics and vocals. Musk plays video games, which he stated has a "'restoring effect' that helps his 'mental calibration'". Some games he plays include Quake, Diablo IV, Elden Ring, and Polytopia. Musk once claimed to be one of the world's top video game players but has since admitted to "account boosting", or cheating by hiring outside services to achieve top player rankings. Musk has justified the boosting by claiming that all top accounts do it so he has to as well to remain competitive. In 2024 and 2025, Musk criticized the video game Assassin's Creed Shadows and its creator Ubisoft for "woke" content. Musk posted to X that "DEI kills art" and specified the inclusion of the historical figure Yasuke in the Assassin's Creed game as offensive; he also called the game "terrible". Ubisoft responded by saying that Musk's comments were "just feeding hatred" and that they were focused on producing a game not pushing politics. Musk has fathered at least 14 children, one of whom died as an infant. The Wall Street Journal reported in 2025 that sources close to Musk suggest that the "true number of Musk's children is much higher than publicly known". He had six children with his first wife, Canadian author Justine Wilson, whom he met while attending Queen's University in Ontario, Canada; they married in 2000. In 2002, their first child Nevada Musk died of sudden infant death syndrome at the age of 10 weeks. After his death, the couple used in vitro fertilization (IVF) to continue their family; they had twins in 2004, followed by triplets in 2006. The couple divorced in 2008 and have shared custody of their children. The elder twin he had with Wilson came out as a trans woman and, in 2022, officially changed her name to Vivian Jenna Wilson, adopting her mother's surname because she no longer wished to be associated with Musk. Musk began dating English actress Talulah Riley in 2008. They married two years later at Dornoch Cathedral in Scotland. In 2012, the couple divorced, then remarried the following year. After briefly filing for divorce in 2014, Musk finalized a second divorce from Riley in 2016. Musk then dated the American actress Amber Heard for several months in 2017; he had reportedly been "pursuing" her since 2012. In 2018, Musk and Canadian musician Grimes confirmed they were dating. Grimes and Musk have three children, born in 2020, 2021, and 2022.[g] Musk and Grimes originally gave their eldest child the name "X Æ A-12", which would have violated California regulations as it contained characters that are not in the modern English alphabet; the names registered on the birth certificate are "X" as a first name, "Æ A-Xii" as a middle name, and "Musk" as a last name. They received criticism for choosing a name perceived to be impractical and difficult to pronounce; Musk has said the intended pronunciation is "X Ash A Twelve". Their second child was born via surrogacy. Despite the pregnancy, Musk confirmed reports that the couple were "semi-separated" in September 2021; in an interview with Time in December 2021, he said he was single. In October 2023, Grimes sued Musk over parental rights and custody of X Æ A-Xii. Elon Musk has taken X Æ A-Xii to multiple official events in Washington, D.C. during Trump's second term in office. Also in July 2022, The Wall Street Journal reported that Musk allegedly had an affair with Nicole Shanahan, the wife of Google co-founder Sergey Brin, in 2021, leading to their divorce the following year. Musk denied the report. Musk also had a relationship with Australian actress Natasha Bassett, who has been described as "an occasional girlfriend". In October 2024, The New York Times reported Musk bought a Texas compound for his children and their mothers, though Musk denied having done so. Musk also has four children with Shivon Zilis, director of operations and special projects at Neuralink: twins born via IVF in 2021, a child born in 2024 via surrogacy and a child born in 2025.[h] On February 14, 2025, Ashley St. Clair, an influencer and author, posted on X claiming to have given birth to Musk's son Romulus five months earlier, which media outlets reported as Musk's supposed thirteenth child.[i] On February 22, 2025, it was reported that St Clair had filed for sole custody of her five-month-old son and for Musk to be recognised as the child's father. On March 31, 2025, Musk wrote that, while he was unsure if he was the father of St. Clair's child, he had paid St. Clair $2.5 million and would continue paying her $500,000 per year.[j] Later reporting from the Wall Street Journal indicated that $1 million of these payments to St. Clair were structured as a loan. In 2014, Musk and Ghislaine Maxwell appeared together in a photograph taken at an Academy Awards after-party, which Musk later described as a "photobomb". The January 2026 Epstein files contain emails between Musk and Epstein from 2012 to 2013, after Epstein's first conviction. Emails released on January 30, 2026, indicated that Epstein invited Musk to visit his private island on multiple occasions. The correspondence showed that while Epstein repeatedly encouraged Musk to attend, Musk did not visit the island. In one instance, Musk discussed the possibility of attending a party with his then-wife Talulah Riley and asked which day would be the "wildest party"; according to the emails, the visit did not take place after Epstein later cancelled the plans.[k] On Christmas day in 2012, Musk emailed Epstein asking "Do you have any parties planned? I’ve been working to the edge of sanity this year and so, once my kids head home after Christmas, I really want to hit the party scene in St Barts or elsewhere and let loose. The invitation is much appreciated, but a peaceful island experience is the opposite of what I’m looking for". Epstein replied that the "ratio on my island" might make Musk's wife uncomfortable to which Musk responded, "Ratio is not a problem for Talulah". On September 11, 2013, Epstein sent an email asking Musk if he had any plans for coming to New York for the opening of the United Nations General Assembly where many "interesting people" would be coming to his house to which Musk responded that "Flying to NY to see UN diplomats do nothing would be an unwise use of time". Epstein responded by stating "Do you think i am retarded. Just kidding, there is no one over 25 and all very cute." Musk has denied any close relationship with Epstein and described him as a "creep" who attempted to ingratiate himself with influential people. When Musk was asked in 2019 if he introduced Epstein to Mark Zuckerberg, Musk responded: "I don’t recall introducing Epstein to anyone, as I don’t know the guy well enough to do so." The released emails nonetheless showed cordial exchanges on a range of topics, including Musk's inquiry about parties on the island. The correspondence also indicated that Musk suggested hosting Epstein at SpaceX, while Epstein separately discussed plans to tour SpaceX and bring "the girls", though there is no evidence that such a visit occurred. Musk has described the release of the files a "distraction", later accusing the second Trump administration of suppressing them to protect powerful individuals, including Trump himself.[l] Wealth Elon Musk is the wealthiest person in the world, with an estimated net worth of US$690 billion as of January 2026, according to the Bloomberg Billionaires Index, and $852 billion according to Forbes, primarily from his ownership stakes in SpaceX and Tesla. Having been first listed on the Forbes Billionaires List in 2012, around 75% of Musk's wealth was derived from Tesla stock in November 2020, although he describes himself as "cash poor". According to Forbes, he became the first person in the world to achieve a net worth of $300 billion in 2021; $400 billion in December 2024; $500 billion in October 2025; $600 billion in mid-December 2025; $700 billion later that month; and $800 billion in February 2026. In November 2025, a Tesla pay package worth potentially $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Public image Although his ventures have been highly influential within their separate industries starting in the 2000s, Musk only became a public figure in the early 2010s. He has been described as an eccentric who makes spontaneous and impactful decisions, while also often making controversial statements, contrary to other billionaires who prefer reclusiveness to protect their businesses. Musk's actions and his expressed views have made him a polarizing figure. Biographer Ashlee Vance described people's opinions of Musk as polarized due to his "part philosopher, part troll" persona on Twitter. He has drawn denouncement for using his platform to mock the self-selection of personal pronouns, while also receiving praise for bringing international attention to matters like British survivors of grooming gangs. Musk has been described as an American oligarch due to his extensive influence over public discourse, social media, industry, politics, and government policy. After Trump's re-election, Musk's influence and actions during the transition period and the second presidency of Donald Trump led some to call him "President Musk", the "actual president-elect", "shadow president" or "co-president". Awards for his contributions to the development of the Falcon rockets include the American Institute of Aeronautics and Astronautics George Low Transportation Award in 2008, the Fédération Aéronautique Internationale Gold Space Medal in 2010, and the Royal Aeronautical Society Gold Medal in 2012. In 2015, he received an honorary doctorate in engineering and technology from Yale University and an Institute of Electrical and Electronics Engineers Honorary Membership. Musk was elected a Fellow of the Royal Society (FRS) in 2018.[m] In 2022, Musk was elected to the National Academy of Engineering. Time has listed Musk as one of the most influential people in the world in 2010, 2013, 2018, and 2021. Musk was selected as Time's "Person of the Year" for 2021. Then Time editor-in-chief Edward Felsenthal wrote that, "Person of the Year is a marker of influence, and few individuals have had more influence than Musk on life on Earth, and potentially life off Earth too." Notes References Works cited Further reading External links |
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