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[SOURCE: https://en.wikipedia.org/wiki/Mubi_(streaming_service)] | [TOKENS: 1900] |
Contents Mubi (streaming service) Mubi (/ˈmuːbi/; styled MUBI; known as The Auteurs until 2010) is a British streaming platform, production company and film distributor. Mubi produces and theatrically distributes films by emerging and established filmmakers, which are exclusively available on its platform. The catalogue consists of world cinema films, such as arthouse, documentary and independent films. Additionally, it publishes Notebook, a film criticism and news publication, and provides weekly cinema tickets to selected new-release films through Mubi Go. Mubi's streaming platform is available in over 190 countries through its website, or using Android TV, Chromecast, Roku devices, Apple Vision Pro, PlayStation consoles, Amazon Fire TV, Apple TV, LG or Samsung Smart TVs, or mobile devices including iPhone, iPad and Android. History The Auteurs was founded in 2007 by Turkish entrepreneur Efe Çakarel. The next year, in 2008, the American home-video distribution company Criterion Collection partnered with The Auteurs to begin a video-on-demand service. In 2010, The Auteurs changed its name to "Mubi" or "MUBI", a two-syllable word with no specific meaning that rhymes with "movie", its creators stating that they wanted "a name all audiences can say and spell, without the burden of exclusionary meaning." In January 2022, Mubi announced the acquisition of arthouse cinema production and sales company The Match Factory. Prior to the 79th Venice International Film Festival world premiere, Mubi entered the TV industry by acquiring The Kingdom Exodus miniseries and bringing out the first two seasons of the original series in director's cuts. In 2023, the company announced Mubi Fest, its annual film festival, to be held in Chile, Colombia, Argentina, Mexico and Brazil. The event was expanded to cities in Europe, the United States and Canada a year later. In February 2024, Mubi acquired a majority stake in Benelux distributor Cinéart. On September 20, 2024, Mubi released The Substance in theaters worldwide and received critical and commercial success, grossed $77 million as their highest grossing film ever, which received a Cannes Film Festival Award for Best Screenplay, Golden Globe Award for Best Actress in a Motion Picture – Musical or Comedy out of 5 nominations at 82nd Golden Globe Awards, 5 Academy Award nominations for Best Picture, Best Director, Best Original Screenplay, Best Actress, and Best Makeup and Hairstyling at the 97th Academy Awards, 5 nominations at the 78th British Academy Film Awards. In February 2025, The New York Times published a major profile piece on Mubi and Efe Çakarel, positioning Mubi as "a real Hollywood player" following the success of The Substance. At the Cannes Film Festival in May 2025, Mubi made their largest acquisition to date, as well as the largest deal closed at the festival that year, by paying $24m for distribution rights across multiple territories to Lynne Ramsay's film Die My Love, starring Jennifer Lawrence and Robert Pattinson. Mubi set a 31 October 2025 date for the company's debut as a direct distributor in the Spanish market with the release of The Mastermind. The company had previously relied on third parties such as Elastica Films, Avalon, A Contracorriente Films, or Filmin for the distribution of its portfolio in Spain. Publication Mubi's International film publication named Notebook, is composed of daily online publications freely accessible via the website (same as streaming), which has been an essential part of the website's relevance as a curated cinema streaming service. The online publication includes a wide variety of coverage of cinema from interviews, features, columns, news, as well as coverage of selected major film festival such as Cannes, Berlinale, Toronto, Sundance and Rotterdam. Since 2009, the publication has featured an ongoing column named "Movie Poster of the Week" by writer Adrian Curry, which curates and discusses mostly contemporary movie posters. The column's focus allows space to discuss and highlight many territory-specific posters of well-known films around the globe. The publication is also known for its focus on a wider range of world cinema and highlight of independent, artist-driven, and experimental cinema. Since its beginning in 2009 its contributors have often published writings on sections from major film festivals that are often ignored by other publications such as Toronto International Film Festival's Wavelengths, the Berlinale Forum Expanded, and the New York Film Festival sections Views from the Avant-Garde (until 2013), Projections (2014–2018), and more Currents (2019–). Throughout the years, the most consistent coverages of these sections in MUBI Notebook has been made by writers Michael Sicinski and David Hudson. In the same form as other online publications of cinema and art at large, MUBI Notebook, is open to the public for pitching and it states its pitching guidelines very clearly on its website. In 2021 Mubi launched the Notebook Magazine (ISSN 2769-7681), an editorially independent semiannual print magazine with limited sale. The magazines are sold globally via both a subscription service (purchased separately from the streaming service) and in selected bookstores around the world. The magazine is only available in English language and has no digital archive or version available. Since issue 4, Mubi states that "Each issue will come with an exclusive surprise, just for subscribers." The magazine has published editions with articles, interviews, and often with special materials written by filmmakers themselves. The magazine's focus is based on themes and has highlighted the work of filmmakers, artists, writers and industry professionals with thematic resonance to the edition's focus. Some of the highlighted professionals include Yasujirō Ozu, Apichatpong Weerasethakul, Emma Seligman, Mike Leigh, Ryusuke Hamaguchi, Park Chan-wook, Jean-Luc Godard, Tsai Ming-liang, Pedro Costa, Alejandro Jodorowsky, Tacita Dean and Sergei Loznitsa, among many others. In issue 3, Mubi began a muti-issue series named "Things a Filmmaker Should Know" inaugurated by Tsai Ming-liang. Which since has been followed by contributions from Pedro Costa (issue 4), Tacita Dean (issue 5), Sergei Loznitsa (issue 5), Amalia Ulman (issue 6), Payal Kapadia (issue 6) and Kevin Jerome Everson (issue 7). Subscriber surprise included a seven-inch record featuring a song by filmmaker Gus Van Sant and a field recording by sound designer Leslie Shatz. Subscriber surprise included a make-your-own papercraft model by artist Ellie Sampson. (based on never-before-seen drawings by Max Douy from Alejandro Jodorowsky's legendary but ill-fated adaptation of Dune.) In a bound insert, author Mark Leyner shares a novelistic treatment for a film that was never made, 8W, a singular and wildly funny prose fantasia. Podcasts In 2021, Mubi launched two original podcasts. An English language podcast called Mubi Podcast produced and hosted by Rico Gagliano, and a Spanish language podcast titled Mubi Podcast: Encuentros, produced in collaboration with La Corriente del Golfo, the production house founded by Gael García Bernal and Diego Luna. In 2023, Mubi launched an Italian-language podcast, Mubi Podcast: Voci Italiane Contemporanee, in collaboration with Chora Media, hosted by critic Gianmaria Tammaro. Mubi productions Mubi productions and co-productions include: Mubi releases Mubi is also a film distributor. In addition to releasing films on the platform, it started distributing theatrically in the United States and United Kingdom in 2016, in Latin America and Germany in 2021, and in Italy and Spain in 2025. Controversy In May 2025, the venture capital firm Sequoia Capital invested $100 million in Mubi, valuing the company at $1 billion. However, the investment has sparked significant backlash due to Sequoia's ties to Kela, an Israeli defence-tech startup founded by former intelligence officers during the Gaza invasion. Critics, including Film Workers for Palestine and supporters of the BDS movement, have condemned Mubi's decision, calling for boycotts and demanding the company return the funds. Mubi has responded by distancing itself from the views of its investors, stating that the partnership aimed to support its global mission in independent cinema. In an open letter written for the press on August 14, 2025, Efe Çakarel addressed the issue by stating that Mubi is not directly tied with the firm while condemning the humanitarian crisis in Gaza and reaffirmed support for peace, dignity, and freedom for all people. To avoid confusion and anger, Mubi launched an Ethical Funding and Investment Policy along with the Artists Advisory Council; while expanding their Artists At Risk Fund "to support filmmakers under conflict, displacement, or censorship through commissions, residencies, and restoration projects". See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Computer#cite_note-111] | [TOKENS: 10628] |
Contents Computer A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations (computation). Modern digital electronic computers can perform generic sets of operations known as programs, which enable computers to perform a wide range of tasks. The term computer system may refer to a nominally complete computer that includes the hardware, operating system, software, and peripheral equipment needed and used for full operation, or to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of industrial and consumer products use computers as control systems, including simple special-purpose devices like microwave ovens and remote controls, and factory devices like industrial robots. Computers are at the core of general-purpose devices such as personal computers and mobile devices such as smartphones. Computers power the Internet, which links billions of computers and users. Early computers were meant to be used only for calculations. Simple manual instruments like the abacus have aided people in doing calculations since ancient times. Early in the Industrial Revolution, some mechanical devices were built to automate long, tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century. The first digital electronic calculating machines were developed during World War II, both electromechanical and using thermionic valves. The first semiconductor transistors in the late 1940s were followed by the silicon-based MOSFET (MOS transistor) and monolithic integrated circuit chip technologies in the late 1950s, leading to the microprocessor and the microcomputer revolution in the 1970s. The speed, power, and versatility of computers have been increasing dramatically ever since then, with transistor counts increasing at a rapid pace (Moore's law noted that counts doubled every two years), leading to the Digital Revolution during the late 20th and early 21st centuries. Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU) in the form of a microprocessor, together with some type of computer memory, typically semiconductor memory chips. The processing element carries out arithmetic and logical operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices (keyboards, mice, joysticks, etc.), output devices (monitors, printers, etc.), and input/output devices that perform both functions (e.g. touchscreens). Peripheral devices allow information to be retrieved from an external source, and they enable the results of operations to be saved and retrieved. Etymology It was not until the mid-20th century that the word acquired its modern definition; according to the Oxford English Dictionary, the first known use of the word computer was in a different sense, in a 1613 book called The Yong Mans Gleanings by the English writer Richard Brathwait: "I haue [sic] read the truest computer of Times, and the best Arithmetician that euer [sic] breathed, and he reduceth thy dayes into a short number." This usage of the term referred to a human computer, a person who carried out calculations or computations. The word continued to have the same meaning until the middle of the 20th century. During the latter part of this period, women were often hired as computers because they could be paid less than their male counterparts. By 1943, most human computers were women. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, meaning 'one who calculates'; this is an "agent noun from compute (v.)". The Online Etymology Dictionary states that the use of the term to mean "'calculating machine' (of any type) is from 1897." The Online Etymology Dictionary indicates that the "modern use" of the term, to mean 'programmable digital electronic computer' dates from "1945 under this name; [in a] theoretical [sense] from 1937, as Turing machine". The name has remained, although modern computers are capable of many higher-level functions. History Devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was most likely a form of tally stick. Later record keeping aids throughout the Fertile Crescent included calculi (clay spheres, cones, etc.) which represented counts of items, likely livestock or grains, sealed in hollow unbaked clay containers.[a] The use of counting rods is one example. The abacus was initially used for arithmetic tasks. The Roman abacus was developed from devices used in Babylonia as early as 2400 BCE. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money. The Antikythera mechanism is believed to be the earliest known mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to approximately c. 100 BCE. Devices of comparable complexity to the Antikythera mechanism would not reappear until the fourteenth century. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use. The planisphere was a star chart invented by Abū Rayhān al-Bīrūnī in the early 11th century. The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BCE and is often attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was effectively an analog computer capable of working out several different kinds of problems in spherical astronomy. An astrolabe incorporating a mechanical calendar computer and gear-wheels was invented by Abi Bakr of Isfahan, Persia in 1235. Abū Rayhān al-Bīrūnī invented the first mechanical geared lunisolar calendar astrolabe, an early fixed-wired knowledge processing machine with a gear train and gear-wheels, c. 1000 AD. The sector, a calculating instrument used for solving problems in proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery, surveying and navigation. The planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage. The slide rule was invented around 1620–1630, by the English clergyman William Oughtred, shortly after the publication of the concept of the logarithm. It is a hand-operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cube roots, as well as transcendental functions such as logarithms and exponentials, circular and hyperbolic trigonometry and other functions. Slide rules with special scales are still used for quick performance of routine calculations, such as the E6B circular slide rule used for time and distance calculations on light aircraft. In the 1770s, Pierre Jaquet-Droz, a Swiss watchmaker, built a mechanical doll (automaton) that could write holding a quill pen. By switching the number and order of its internal wheels different letters, and hence different messages, could be produced. In effect, it could be mechanically "programmed" to read instructions. Along with two other complex machines, the doll is at the Musée d'Art et d'Histoire of Neuchâtel, Switzerland, and still operates. In 1831–1835, mathematician and engineer Giovanni Plana devised a Perpetual Calendar machine, which through a system of pulleys and cylinders could predict the perpetual calendar for every year from 0 CE (that is, 1 BCE) to 4000 CE, keeping track of leap years and varying day length. The tide-predicting machine invented by the Scottish scientist Sir William Thomson in 1872 was of great utility to navigation in shallow waters. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location. The differential analyser, a mechanical analog computer designed to solve differential equations by integration, used wheel-and-disc mechanisms to perform the integration. In 1876, Sir William Thomson had already discussed the possible construction of such calculators, but he had been stymied by the limited output torque of the ball-and-disk integrators. In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output. The torque amplifier was the advance that allowed these machines to work. Starting in the 1920s, Vannevar Bush and others developed mechanical differential analyzers. In the 1890s, the Spanish engineer Leonardo Torres Quevedo began to develop a series of advanced analog machines that could solve real and complex roots of polynomials, which were published in 1901 by the Paris Academy of Sciences. Charles Babbage, an English mechanical engineer and polymath, originated the concept of a programmable computer. Considered the "father of the computer", he conceptualized and invented the first mechanical computer in the early 19th century. After working on his difference engine he announced his invention in 1822, in a paper to the Royal Astronomical Society, titled "Note on the application of machinery to the computation of astronomical and mathematical tables". He also designed to aid in navigational calculations, in 1833 he realized that a much more general design, an analytical engine, was possible. The input of programs and data was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. The engine would incorporate an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete. The machine was about a century ahead of its time. All the parts for his machine had to be made by hand – this was a major problem for a device with thousands of parts. Eventually, the project was dissolved with the decision of the British Government to cease funding. Babbage's failure to complete the analytical engine can be chiefly attributed to political and financial difficulties as well as his desire to develop an increasingly sophisticated computer and to move ahead faster than anyone else could follow. Nevertheless, his son, Henry Babbage, completed a simplified version of the analytical engine's computing unit (the mill) in 1888. He gave a successful demonstration of its use in computing tables in 1906. In his work Essays on Automatics published in 1914, Leonardo Torres Quevedo wrote a brief history of Babbage's efforts at constructing a mechanical Difference Engine and Analytical Engine. The paper contains a design of a machine capable to calculate formulas like a x ( y − z ) 2 {\displaystyle a^{x}(y-z)^{2}} , for a sequence of sets of values. The whole machine was to be controlled by a read-only program, which was complete with provisions for conditional branching. He also introduced the idea of floating-point arithmetic. In 1920, to celebrate the 100th anniversary of the invention of the arithmometer, Torres presented in Paris the Electromechanical Arithmometer, which allowed a user to input arithmetic problems through a keyboard, and computed and printed the results, demonstrating the feasibility of an electromechanical analytical engine. During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers. The first modern analog computer was a tide-predicting machine, invented by Sir William Thomson (later to become Lord Kelvin) in 1872. The differential analyser, a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by James Thomson, the elder brother of the more famous Sir William Thomson. The art of mechanical analog computing reached its zenith with the differential analyzer, completed in 1931 by Vannevar Bush at MIT. By the 1950s, the success of digital electronic computers had spelled the end for most analog computing machines, but analog computers remained in use during the 1950s in some specialized applications such as education (slide rule) and aircraft (control systems).[citation needed] Claude Shannon's 1937 master's thesis laid the foundations of digital computing, with his insight of applying Boolean algebra to the analysis and synthesis of switching circuits being the basic concept which underlies all electronic digital computers. By 1938, the United States Navy had developed the Torpedo Data Computer, an electromechanical analog computer for submarines that used trigonometry to solve the problem of firing a torpedo at a moving target. During World War II, similar devices were developed in other countries. Early digital computers were electromechanical; electric switches drove mechanical relays to perform the calculation. These devices had a low operating speed and were eventually superseded by much faster all-electric computers, originally using vacuum tubes. The Z2, created by German engineer Konrad Zuse in 1939 in Berlin, was one of the earliest examples of an electromechanical relay computer. In 1941, Zuse followed his earlier machine up with the Z3, the world's first working electromechanical programmable, fully automatic digital computer. The Z3 was built with 2000 relays, implementing a 22-bit word length that operated at a clock frequency of about 5–10 Hz. Program code was supplied on punched film while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advances such as floating-point numbers. Rather than the harder-to-implement decimal system (used in Charles Babbage's earlier design), using a binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time. The Z3 was not itself a universal computer but could be extended to be Turing complete. Zuse's next computer, the Z4, became the world's first commercial computer; after initial delay due to the Second World War, it was completed in 1950 and delivered to the ETH Zurich. The computer was manufactured by Zuse's own company, Zuse KG, which was founded in 1941 as the first company with the sole purpose of developing computers in Berlin. The Z4 served as the inspiration for the construction of the ERMETH, the first Swiss computer and one of the first in Europe. Purely electronic circuit elements soon replaced their mechanical and electromechanical equivalents, at the same time that digital calculation replaced analog. The engineer Tommy Flowers, working at the Post Office Research Station in London in the 1930s, began to explore the possible use of electronics for the telephone exchange. Experimental equipment that he built in 1934 went into operation five years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes. In the US, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed and tested the Atanasoff–Berry Computer (ABC) in 1942, the first "automatic electronic digital computer". This design was also all-electronic and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory. During World War II, the British code-breakers at Bletchley Park achieved a number of successes at breaking encrypted German military communications. The German encryption machine, Enigma, was first attacked with the help of the electro-mechanical bombes which were often run by women. To crack the more sophisticated German Lorenz SZ 40/42 machine, used for high-level Army communications, Max Newman and his colleagues commissioned Flowers to build the Colossus. He spent eleven months from early February 1943 designing and building the first Colossus. After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944 and attacked its first message on 5 February. Colossus was the world's first electronic digital programmable computer. It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of boolean logical operations on its data, but it was not Turing-complete. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total). Colossus Mark I contained 1,500 thermionic valves (tubes), but Mark II with 2,400 valves, was both five times faster and simpler to operate than Mark I, greatly speeding the decoding process. The ENIAC (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in the U.S. Although the ENIAC was similar to the Colossus, it was much faster, more flexible, and it was Turing-complete. Like the Colossus, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the stored program electronic machines that came later. Once a program was written, it had to be mechanically set into the machine with manual resetting of plugs and switches. The programmers of the ENIAC were six women, often known collectively as the "ENIAC girls". It combined the high speed of electronics with the ability to be programmed for many complex problems. It could add or subtract 5000 times a second, a thousand times faster than any other machine. It also had modules to multiply, divide, and square root. High speed memory was limited to 20 words (about 80 bytes). Built under the direction of John Mauchly and J. Presper Eckert at the University of Pennsylvania, ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. The machine was huge, weighing 30 tons, using 200 kilowatts of electric power and contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors. The principle of the modern computer was proposed by Alan Turing in his seminal 1936 paper, On Computable Numbers. Turing proposed a simple device that he called "Universal Computing machine" and that is now known as a universal Turing machine. He proved that such a machine is capable of computing anything that is computable by executing instructions (program) stored on tape, allowing the machine to be programmable. The fundamental concept of Turing's design is the stored program, where all the instructions for computing are stored in memory. Von Neumann acknowledged that the central concept of the modern computer was due to this paper. Turing machines are to this day a central object of study in theory of computation. Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete, which is to say, they have algorithm execution capability equivalent to a universal Turing machine. Early computing machines had fixed programs. Changing its function required the re-wiring and re-structuring of the machine. With the proposal of the stored-program computer this changed. A stored-program computer includes by design an instruction set and can store in memory a set of instructions (a program) that details the computation. The theoretical basis for the stored-program computer was laid out by Alan Turing in his 1936 paper. In 1945, Turing joined the National Physical Laboratory and began work on developing an electronic stored-program digital computer. His 1945 report "Proposed Electronic Calculator" was the first specification for such a device. John von Neumann at the University of Pennsylvania also circulated his First Draft of a Report on the EDVAC in 1945. The Manchester Baby was the world's first stored-program computer. It was built at the University of Manchester in England by Frederic C. Williams, Tom Kilburn and Geoff Tootill, and ran its first program on 21 June 1948. It was designed as a testbed for the Williams tube, the first random-access digital storage device. Although the computer was described as "small and primitive" by a 1998 retrospective, it was the first working machine to contain all of the elements essential to a modern electronic computer. As soon as the Baby had demonstrated the feasibility of its design, a project began at the university to develop it into a practically useful computer, the Manchester Mark 1. The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer. Built by Ferranti, it was delivered to the University of Manchester in February 1951. At least seven of these later machines were delivered between 1953 and 1957, one of them to Shell labs in Amsterdam. In October 1947 the directors of British catering company J. Lyons & Company decided to take an active role in promoting the commercial development of computers. Lyons's LEO I computer, modelled closely on the Cambridge EDSAC of 1949, became operational in April 1951 and ran the world's first routine office computer job. The concept of a field-effect transistor was proposed by Julius Edgar Lilienfeld in 1925. John Bardeen and Walter Brattain, while working under William Shockley at Bell Labs, built the first working transistor, the point-contact transistor, in 1947, which was followed by Shockley's bipolar junction transistor in 1948. From 1955 onwards, transistors replaced vacuum tubes in computer designs, giving rise to the "second generation" of computers. Compared to vacuum tubes, transistors have many advantages: they are smaller, and require less power than vacuum tubes, so give off less heat. Junction transistors were much more reliable than vacuum tubes and had longer, indefinite, service life. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space. However, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis, which limited them to a number of specialized applications. At the University of Manchester, a team under the leadership of Tom Kilburn designed and built a machine using the newly developed transistors instead of valves. Their first transistorized computer and the first in the world, was operational by 1953, and a second version was completed there in April 1955. However, the machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory, so it was not the first completely transistorized computer. That distinction goes to the Harwell CADET of 1955, built by the electronics division of the Atomic Energy Research Establishment at Harwell. The metal–oxide–silicon field-effect transistor (MOSFET), also known as the MOS transistor, was invented at Bell Labs between 1955 and 1960 and was the first truly compact transistor that could be miniaturized and mass-produced for a wide range of uses. With its high scalability, and much lower power consumption and higher density than bipolar junction transistors, the MOSFET made it possible to build high-density integrated circuits. In addition to data processing, it also enabled the practical use of MOS transistors as memory cell storage elements, leading to the development of MOS semiconductor memory, which replaced earlier magnetic-core memory in computers. The MOSFET led to the microcomputer revolution, and became the driving force behind the computer revolution. The MOSFET is the most widely used transistor in computers, and is the fundamental building block of digital electronics. The next great advance in computing power came with the advent of the integrated circuit (IC). The idea of the integrated circuit was first conceived by a radar scientist working for the Royal Radar Establishment of the Ministry of Defence, Geoffrey W.A. Dummer. Dummer presented the first public description of an integrated circuit at the Symposium on Progress in Quality Electronic Components in Washington, D.C., on 7 May 1952. The first working ICs were invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor. Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958. In his patent application of 6 February 1959, Kilby described his new device as "a body of semiconductor material ... wherein all the components of the electronic circuit are completely integrated". However, Kilby's invention was a hybrid integrated circuit (hybrid IC), rather than a monolithic integrated circuit (IC) chip. Kilby's IC had external wire connections, which made it difficult to mass-produce. Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. Noyce's invention was the first true monolithic IC chip. His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon, whereas Kilby's chip was made of germanium. Noyce's monolithic IC was fabricated using the planar process, developed by his colleague Jean Hoerni in early 1959. In turn, the planar process was based on Carl Frosch and Lincoln Derick work on semiconductor surface passivation by silicon dioxide. Modern monolithic ICs are predominantly MOS (metal–oxide–semiconductor) integrated circuits, built from MOSFETs (MOS transistors). The earliest experimental MOS IC to be fabricated was a 16-transistor chip built by Fred Heiman and Steven Hofstein at RCA in 1962. General Microelectronics later introduced the first commercial MOS IC in 1964, developed by Robert Norman. Following the development of the self-aligned gate (silicon-gate) MOS transistor by Robert Kerwin, Donald Klein and John Sarace at Bell Labs in 1967, the first silicon-gate MOS IC with self-aligned gates was developed by Federico Faggin at Fairchild Semiconductor in 1968. The MOSFET has since become the most critical device component in modern ICs. The development of the MOS integrated circuit led to the invention of the microprocessor, and heralded an explosion in the commercial and personal use of computers. While the subject of exactly which device was the first microprocessor is contentious, partly due to lack of agreement on the exact definition of the term "microprocessor", it is largely undisputed that the first single-chip microprocessor was the Intel 4004, designed and realized by Federico Faggin with his silicon-gate MOS IC technology, along with Ted Hoff, Masatoshi Shima and Stanley Mazor at Intel.[b] In the early 1970s, MOS IC technology enabled the integration of more than 10,000 transistors on a single chip. System on a Chip (SoCs) are complete computers on a microchip (or chip) the size of a coin. They may or may not have integrated RAM and flash memory. If not integrated, the RAM is usually placed directly above (known as Package on package) or below (on the opposite side of the circuit board) the SoC, and the flash memory is usually placed right next to the SoC. This is done to improve data transfer speeds, as the data signals do not have to travel long distances. Since ENIAC in 1945, computers have advanced enormously, with modern SoCs (such as the Snapdragon 865) being the size of a coin while also being hundreds of thousands of times more powerful than ENIAC, integrating billions of transistors, and consuming only a few watts of power. The first mobile computers were heavy and ran from mains power. The 50 lb (23 kg) IBM 5100 was an early example. Later portables such as the Osborne 1 and Compaq Portable were considerably lighter but still needed to be plugged in. The first laptops, such as the Grid Compass, removed this requirement by incorporating batteries – and with the continued miniaturization of computing resources and advancements in portable battery life, portable computers grew in popularity in the 2000s. The same developments allowed manufacturers to integrate computing resources into cellular mobile phones by the early 2000s. These smartphones and tablets run on a variety of operating systems and recently became the dominant computing device on the market. These are powered by System on a Chip (SoCs), which are complete computers on a microchip the size of a coin. Types Computers can be classified in a number of different ways, including: A computer does not need to be electronic, nor even have a processor, nor RAM, nor even a hard disk. While popular usage of the word "computer" is synonymous with a personal electronic computer,[c] a typical modern definition of a computer is: "A device that computes, especially a programmable [usually] electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information." According to this definition, any device that processes information qualifies as a computer. Hardware The term hardware covers all of those parts of a computer that are tangible physical objects. Circuits, computer chips, graphic cards, sound cards, memory (RAM), motherboard, displays, power supplies, cables, keyboards, printers and "mice" input devices are all hardware. A general-purpose computer has four main components: the arithmetic logic unit (ALU), the control unit, the memory, and the input and output devices (collectively termed I/O). These parts are interconnected by buses, often made of groups of wires. Inside each of these parts are thousands to trillions of small electrical circuits which can be turned off or on by means of an electronic switch. Each circuit represents a bit (binary digit) of information so that when the circuit is on it represents a "1", and when off it represents a "0" (in positive logic representation). The circuits are arranged in logic gates so that one or more of the circuits may control the state of one or more of the other circuits. Input devices are the means by which the operations of a computer are controlled and it is provided with data. Examples include: Output devices are the means by which a computer provides the results of its calculations in a human-accessible form. Examples include: The control unit (often called a control system or central controller) manages the computer's various components; it reads and interprets (decodes) the program instructions, transforming them into control signals that activate other parts of the computer.[e] Control systems in advanced computers may change the order of execution of some instructions to improve performance. A key component common to all CPUs is the program counter, a special memory cell (a register) that keeps track of which location in memory the next instruction is to be read from.[f] The control system's function is as follows— this is a simplified description, and some of these steps may be performed concurrently or in a different order depending on the type of CPU: Since the program counter is (conceptually) just another set of memory cells, it can be changed by calculations done in the ALU. Adding 100 to the program counter would cause the next instruction to be read from a place 100 locations further down the program. Instructions that modify the program counter are often known as "jumps" and allow for loops (instructions that are repeated by the computer) and often conditional instruction execution (both examples of control flow). The sequence of operations that the control unit goes through to process an instruction is in itself like a short computer program, and indeed, in some more complex CPU designs, there is another yet smaller computer called a microsequencer, which runs a microcode program that causes all of these events to happen. The control unit, ALU, and registers are collectively known as a central processing unit (CPU). Early CPUs were composed of many separate components. Since the 1970s, CPUs have typically been constructed on a single MOS integrated circuit chip called a microprocessor. The ALU is capable of performing two classes of operations: arithmetic and logic. The set of arithmetic operations that a particular ALU supports may be limited to addition and subtraction, or might include multiplication, division, trigonometry functions such as sine, cosine, etc., and square roots. Some can operate only on whole numbers (integers) while others use floating point to represent real numbers, albeit with limited precision. However, any computer that is capable of performing just the simplest operations can be programmed to break down the more complex operations into simple steps that it can perform. Therefore, any computer can be programmed to perform any arithmetic operation—although it will take more time to do so if its ALU does not directly support the operation. An ALU may also compare numbers and return Boolean truth values (true or false) depending on whether one is equal to, greater than or less than the other ("is 64 greater than 65?"). Logic operations involve Boolean logic: AND, OR, XOR, and NOT. These can be useful for creating complicated conditional statements and processing Boolean logic. Superscalar computers may contain multiple ALUs, allowing them to process several instructions simultaneously. Graphics processors and computers with SIMD and MIMD features often contain ALUs that can perform arithmetic on vectors and matrices. A computer's memory can be viewed as a list of cells into which numbers can be placed or read. Each cell has a numbered "address" and can store a single number. The computer can be instructed to "put the number 123 into the cell numbered 1357" or to "add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595." The information stored in memory may represent practically anything. Letters, numbers, even computer instructions can be placed into memory with equal ease. Since the CPU does not differentiate between different types of information, it is the software's responsibility to give significance to what the memory sees as nothing but a series of numbers. In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte). Each byte is able to represent 256 different numbers (28 = 256); either from 0 to 255 or −128 to +127. To store larger numbers, several consecutive bytes may be used (typically, two, four or eight). When negative numbers are required, they are usually stored in two's complement notation. Other arrangements are possible, but are usually not seen outside of specialized applications or historical contexts. A computer can store any kind of information in memory if it can be represented numerically. Modern computers have billions or even trillions of bytes of memory. The CPU contains a special set of memory cells called registers that can be read and written to much more rapidly than the main memory area. There are typically between two and one hundred registers depending on the type of CPU. Registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed. As data is constantly being worked on, reducing the need to access main memory (which is often slow compared to the ALU and control units) greatly increases the computer's speed. Computer main memory comes in two principal varieties: RAM can be read and written to anytime the CPU commands it, but ROM is preloaded with data and software that never changes, therefore the CPU can only read from it. ROM is typically used to store the computer's initial start-up instructions. In general, the contents of RAM are erased when the power to the computer is turned off, but ROM retains its data indefinitely. In a PC, the ROM contains a specialized program called the BIOS that orchestrates loading the computer's operating system from the hard disk drive into RAM whenever the computer is turned on or reset. In embedded computers, which frequently do not have disk drives, all of the required software may be stored in ROM. Software stored in ROM is often called firmware, because it is notionally more like hardware than software. Flash memory blurs the distinction between ROM and RAM, as it retains its data when turned off but is also rewritable. It is typically much slower than conventional ROM and RAM however, so its use is restricted to applications where high speed is unnecessary.[g] In more sophisticated computers there may be one or more RAM cache memories, which are slower than registers but faster than main memory. Generally computers with this sort of cache are designed to move frequently needed data into the cache automatically, often without the need for any intervention on the programmer's part. I/O is the means by which a computer exchanges information with the outside world. Devices that provide input or output to the computer are called peripherals. On a typical personal computer, peripherals include input devices like the keyboard and mouse, and output devices such as the display and printer. Hard disk drives, floppy disk drives and optical disc drives serve as both input and output devices. Computer networking is another form of I/O. I/O devices are often complex computers in their own right, with their own CPU and memory. A graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3D graphics.[citation needed] Modern desktop computers contain many smaller computers that assist the main CPU in performing I/O. A 2016-era flat screen display contains its own computer circuitry. While a computer may be viewed as running one gigantic program stored in its main memory, in some systems it is necessary to give the appearance of running several programs simultaneously. This is achieved by multitasking, i.e. having the computer switch rapidly between running each program in turn. One means by which this is done is with a special signal called an interrupt, which can periodically cause the computer to stop executing instructions where it was and do something else instead. By remembering where it was executing prior to the interrupt, the computer can return to that task later. If several programs are running "at the same time". Then the interrupt generator might be causing several hundred interrupts per second, causing a program switch each time. Since modern computers typically execute instructions several orders of magnitude faster than human perception, it may appear that many programs are running at the same time, even though only one is ever executing in any given instant. This method of multitasking is sometimes termed "time-sharing" since each program is allocated a "slice" of time in turn. Before the era of inexpensive computers, the principal use for multitasking was to allow many people to share the same computer. Seemingly, multitasking would cause a computer that is switching between several programs to run more slowly, in direct proportion to the number of programs it is running, but most programs spend much of their time waiting for slow input/output devices to complete their tasks. If a program is waiting for the user to click on the mouse or press a key on the keyboard, then it will not take a "time slice" until the event it is waiting for has occurred. This frees up time for other programs to execute so that many programs may be run simultaneously without unacceptable speed loss. Some computers are designed to distribute their work across several CPUs in a multiprocessing configuration, a technique once employed in only large and powerful machines such as supercomputers, mainframe computers and servers. Multiprocessor and multi-core (multiple CPUs on a single integrated circuit) personal and laptop computers are now widely available, and are being increasingly used in lower-end markets as a result. Supercomputers in particular often have highly unique architectures that differ significantly from the basic stored-program architecture and from general-purpose computers.[h] They often feature thousands of CPUs, customized high-speed interconnects, and specialized computing hardware. Such designs tend to be useful for only specialized tasks due to the large scale of program organization required to use most of the available resources at once. Supercomputers usually see usage in large-scale simulation, graphics rendering, and cryptography applications, as well as with other so-called "embarrassingly parallel" tasks. Software Software is the part of a computer system that consists of the encoded information that determines the computer's operation, such as data or instructions on how to process the data. In contrast to the physical hardware from which the system is built, software is immaterial. Software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. It is often divided into system software and application software. Computer hardware and software require each other and neither is useful on its own. When software is stored in hardware that cannot easily be modified, such as with BIOS ROM in an IBM PC compatible computer, it is sometimes called "firmware". The defining feature of modern computers which distinguishes them from all other machines is that they can be programmed. That is to say that some type of instructions (the program) can be given to the computer, and it will process them. Modern computers based on the von Neumann architecture often have machine code in the form of an imperative programming language. In practical terms, a computer program may be just a few instructions or extend to many millions of instructions, as do the programs for word processors and web browsers for example. A typical modern computer can execute billions of instructions per second (gigaflops) and rarely makes a mistake over many years of operation. Large computer programs consisting of several million instructions may take teams of programmers years to write, and due to the complexity of the task almost certainly contain errors. This section applies to most common RAM machine–based computers. In most cases, computer instructions are simple: add one number to another, move some data from one location to another, send a message to some external device, etc. These instructions are read from the computer's memory and are generally carried out (executed) in the order they were given. However, there are usually specialized instructions to tell the computer to jump ahead or backwards to some other place in the program and to carry on executing from there. These are called "jump" instructions (or branches). Furthermore, jump instructions may be made to happen conditionally so that different sequences of instructions may be used depending on the result of some previous calculation or some external event. Many computers directly support subroutines by providing a type of jump that "remembers" the location it jumped from and another instruction to return to the instruction following that jump instruction. Program execution might be likened to reading a book. While a person will normally read each word and line in sequence, they may at times jump back to an earlier place in the text or skip sections that are not of interest. Similarly, a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met. This is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention. Comparatively, a person using a pocket calculator can perform a basic arithmetic operation such as adding two numbers with just a few button presses. But to add together all of the numbers from 1 to 1,000 would take thousands of button presses and a lot of time, with a near certainty of making a mistake. On the other hand, a computer may be programmed to do this with just a few simple instructions. The following example is written in the MIPS assembly language: Once told to run this program, the computer will perform the repetitive addition task without further human intervention. It will almost never make a mistake and a modern PC can complete the task in a fraction of a second. In most computers, individual instructions are stored as machine code with each instruction being given a unique number (its operation code or opcode for short). The command to add two numbers together would have one opcode; the command to multiply them would have a different opcode, and so on. The simplest computers are able to perform any of a handful of different instructions; the more complex computers have several hundred to choose from, each with a unique numerical code. Since the computer's memory is able to store numbers, it can also store the instruction codes. This leads to the important fact that entire programs (which are just lists of these instructions) can be represented as lists of numbers and can themselves be manipulated inside the computer in the same way as numeric data. The fundamental concept of storing programs in the computer's memory alongside the data they operate on is the crux of the von Neumann, or stored program, architecture. In some cases, a computer might store some or all of its program in memory that is kept separate from the data it operates on. This is called the Harvard architecture after the Harvard Mark I computer. Modern von Neumann computers display some traits of the Harvard architecture in their designs, such as in CPU caches. While it is possible to write computer programs as long lists of numbers (machine language) and while this technique was used with many early computers,[i] it is extremely tedious and potentially error-prone to do so in practice, especially for complicated programs. Instead, each basic instruction can be given a short name that is indicative of its function and easy to remember – a mnemonic such as ADD, SUB, MULT or JUMP. These mnemonics are collectively known as a computer's assembly language. Converting programs written in assembly language into something the computer can actually understand (machine language) is usually done by a computer program called an assembler. A programming language is a notation system for writing the source code from which a computer program is produced. Programming languages provide various ways of specifying programs for computers to run. Unlike natural languages, programming languages are designed to permit no ambiguity and to be concise. They are purely written languages and are often difficult to read aloud. They are generally either translated into machine code by a compiler or an assembler before being run, or translated directly at run time by an interpreter. Sometimes programs are executed by a hybrid method of the two techniques. There are thousands of programming languages—some intended for general purpose programming, others useful for only highly specialized applications. Machine languages and the assembly languages that represent them (collectively termed low-level programming languages) are generally unique to the particular architecture of a computer's central processing unit (CPU). For instance, an ARM architecture CPU (such as may be found in a smartphone or a hand-held videogame) cannot understand the machine language of an x86 CPU that might be in a PC.[j] Historically a significant number of other CPU architectures were created and saw extensive use, notably including the MOS Technology 6502 and 6510 in addition to the Zilog Z80. Although considerably easier than in machine language, writing long programs in assembly language is often difficult and is also error prone. Therefore, most practical programs are written in more abstract high-level programming languages that are able to express the needs of the programmer more conveniently (and thereby help reduce programmer error). High level languages are usually "compiled" into machine language (or sometimes into assembly language and then into machine language) using another computer program called a compiler.[k] High level languages are less related to the workings of the target computer than assembly language, and more related to the language and structure of the problem(s) to be solved by the final program. It is therefore often possible to use different compilers to translate the same high level language program into the machine language of many different types of computer. This is part of the means by which software like video games may be made available for different computer architectures such as personal computers and various video game consoles. Program design of small programs is relatively simple and involves the analysis of the problem, collection of inputs, using the programming constructs within languages, devising or using established procedures and algorithms, providing data for output devices and solutions to the problem as applicable. As problems become larger and more complex, features such as subprograms, modules, formal documentation, and new paradigms such as object-oriented programming are encountered. Large programs involving thousands of line of code and more require formal software methodologies. The task of developing large software systems presents a significant intellectual challenge. Producing software with an acceptably high reliability within a predictable schedule and budget has historically been difficult; the academic and professional discipline of software engineering concentrates specifically on this challenge. Errors in computer programs are called "bugs". They may be benign and not affect the usefulness of the program, or have only subtle effects. However, in some cases they may cause the program or the entire system to "hang", becoming unresponsive to input such as mouse clicks or keystrokes, to completely fail, or to crash. Otherwise benign bugs may sometimes be harnessed for malicious intent by an unscrupulous user writing an exploit, code designed to take advantage of a bug and disrupt a computer's proper execution. Bugs are usually not the fault of the computer. Since computers merely execute the instructions they are given, bugs are nearly always the result of programmer error or an oversight made in the program's design.[l] Admiral Grace Hopper, an American computer scientist and developer of the first compiler, is credited for having first used the term "bugs" in computing after a dead moth was found shorting a relay in the Harvard Mark II computer in September 1947. Networking and the Internet Computers have been used to coordinate information between multiple physical locations since the 1950s. The U.S. military's SAGE system was the first large-scale example of such a system, which led to a number of special-purpose commercial systems such as Sabre. In the 1970s, computer engineers at research institutions throughout the United States began to link their computers together using telecommunications technology. The effort was funded by ARPA (now DARPA), and the computer network that resulted was called the ARPANET. Logic gates are a common abstraction which can apply to most of the above digital or analog paradigms. The ability to store and execute lists of instructions called programs makes computers extremely versatile, distinguishing them from calculators. The Church–Turing thesis is a mathematical statement of this versatility: any computer with a minimum capability (being Turing-complete) is, in principle, capable of performing the same tasks that any other computer can perform. Therefore, any type of computer (netbook, supercomputer, cellular automaton, etc.) is able to perform the same computational tasks, given enough time and storage capacity. In the 20th century, artificial intelligence systems were predominantly symbolic: they executed code that was explicitly programmed by software developers. Machine learning models, however, have a set parameters that are adjusted throughout training, so that the model learns to accomplish a task based on the provided data. The efficiency of machine learning (and in particular of neural networks) has rapidly improved with progress in hardware for parallel computing, mainly graphics processing units (GPUs). Some large language models are able to control computers or robots. AI progress may lead to the creation of artificial general intelligence (AGI), a type of AI that could accomplish virtually any intellectual task at least as well as humans. Professions and organizations As the use of computers has spread throughout society, there are an increasing number of careers involving computers. The need for computers to work well together and to be able to exchange information has spawned the need for many standards organizations, clubs and societies of both a formal and informal nature. See also Notes References Sources External links |
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Contents Cursor (code editor) Cursor is an AI-assisted integrated development environment for Windows, macOS, and Linux. It is a fork of Visual Studio Code with additional AI features. Cursor is proprietary software and developed by Anysphere, a San Francisco-based startup company founded in 2022. Service Cursor uses large language models to manipulate text with autocomplete and chat query function. It is a fork of Visual Studio Code. Several media outlets have described Cursor as a vibe coding app. Cursor allows developers to produce code from natural language instructions. Users can generate or update parts of their code by providing prompts. It can also index the codebase, which can be queried in natural language. The editor offers "smart rewrite" capabilities, allowing users to change multiple lines of code simultaneously. In April 2025, Cursor experienced a bug preventing the use of the software on multiple devices at once. A Cursor customer support email using AI-generated responses falsely cited a policy prohibiting a single subscription license from being used on multiple devices for security reasons, and falsely stated that a separate subscription had to be purchased for each device. Amid criticism of the new "policy" on Reddit, an Anysphere spokesperson issued a retraction clarifying that no such policy existed, and that it was an erroneous response from a "front-line AI support bot". Cursor's service model is great for "vibe coding" and has the ability to leverage large language models (LLMs) for developers to build complex software systems. Cursor's features enable multi-line code manipulation and deep codebase analysis in order to build these systems. However, newer warnings from Cursor's CEO indicate that vibe coding can lead to unstable codebase foundations and should be carefully watched for technical debt. See also References External links |
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Contents John Michell John Michell (/ˈmɪtʃəl/; 25 December 1724 – 21 April 1793) was an English natural philosopher and clergyman who provided pioneering insights into a wide range of scientific fields including astronomy, geology, optics, and gravitation. He was the first to have proposed the existence of stellar bodies comparable to black holes, and was the first to apply statistics to astronomy, providing the earliest evidence for the physical nature of double stars and star clusters. He was first to have suggested that earthquakes travelled in (seismic) waves and the first to have measured the velocity of an earthquake, that being the 1755 Lisbon earthquake. Michell further invented an apparatus to measure the mass of the Earth that was later used by Henry Cavendish to measure the gravitational constant. He also explained how to manufacture an artificial magnet and provided the first accurate and comprehensive statement of the law of magnetic force. As a result, he has been called the father of both seismology and of magnetometry. Michell served as the Woodwardian Professor of Geology at the University of Cambridge starting in 1762. He was elected a Fellow of the Royal Society in 1760. Early life, education and professional positions John Michell was born in 1724 in Eakring, in Nottinghamshire, the son of Gilbert Michell, a priest, and Obedience Gerrard. Gilbert was the son of William Michell and Mary Taylor of Kenwyn, Cornwall; Obedience was the daughter of Ralph and Hannah Gerrard of London. He was educated at Queens' College, Cambridge, and later became a Fellow of Queens'. The family was of Cornish origins. He obtained his M.A. degree in 1752, and his B.D. degree in 1761. He was Tutor of the college from 1751 to 1763; Praelector in Arithmetic in 1751; Censor in Theology in 1752; Praelector in Geometry in 1753; Praelector in Greek in 1755 and 1759; Senior Bursar in 1756; Praelector in Hebrew in 1759 and 1762; Censor in Philosophy and Examiner in 1760. "He was nominated Rector of St Botolph's, Cambridge, on 28 March 1760, and held this living until June 1763." From 1762 to 1764, he held the Woodwardian Chair of Geology until he was obliged to relinquish it on his marriage. There is no surviving portrait of Michell; he is said to have been "a little short Man, of a black Complexion, and fat but having no Acquaintance with him, can say little of him. I think he had the care of St. Botolph's Church Cambridge, while he continued Fellow of Queens’ College, where he was esteemed a very ingenious Man, and an excellent Philosopher. He has published some things in that way, on the Magnet and Electricity." In 1910, Sir Edmund Whittaker observed that during the century after Isaac Newton's death, "the only natural philosopher of distinction who lived and taught at Cambridge was Michell", although his "researches seem to have attracted little or no attention among his collegiate contemporaries and successors, who silently acquiesced when his discoveries were attributed to others, and allowed his name to perish entirely from Cambridge tradition". Michell proceeded to take up clerical positions in Compton and then Havant, both in Hampshire. During this period he unsuccessfully sought positions at Cambridge, and as Astronomer Royal. In 1767, he was appointed rector of St. Michael's Church of Thornhill, near Leeds, Yorkshire, England, a post he held for the rest of his life. He did most of his important scientific work in Thornhill, where he died on 21 April 1793, aged 68. He is buried there. After local pressure, a blue plaque went up on the church wall to commemorate him. Scientific work In 1750, Michell published at Cambridge a work of some eighty pages entitled "A Treatise of Artificial Magnets", in which he presented an easy and expeditious method of producing magnets that are superior to the best natural magnets. Besides the description of the method of magnetization which still bears his name, this work contains a variety of accurate observations about magnetism, and features a lucid exposition of the nature of magnetic induction. At one point, Michell attempted to measure the radiation pressure of light by focusing sunlight onto one side of a compass needle. The experiment was not a success: the needle melted. Until the late 20th century Michell was considered important primarily because of his work on geology. His most important geological essay, written after the 1755 Lisbon earthquake, was entitled "Conjectures concerning the Cause and Observations upon the Phaenomena of Earthquakes" (Philosophical Transactions, li. 1760). In this paper he introduced the idea that earthquakes spread out as waves through the Earth, and that they involve the offsets in geological strata now known as faults. He was able to estimate both the epicentre and the focus of the Lisbon earthquake, and may also have been the first to suggest that a tsunami is caused by a submarine earthquake. He was the first to calculate the velocity of an earthquake. Michell's essay not only provided insights on earthquakes but also, more broadly, represented an advance in the understanding of the geology of the Earth's crust. He recognized that the Earth is composed "of regular and uniform strata", some of which have been interrupted by upheavals. "The most important part of Michell's Earthquake paper", in the view of one commentator, "is the account which it contains of what is now known as 'the crust of the Earth.'" Exhibiting a remarkable knowledge of the geological strata in various parts of England and abroad, he drew on his own observations to advance the understanding of sedimentary stratigraphy and was the first to define the Mesozoic stratigraphy in the U.K. In 1760, as a result of this work, he was elected a member of the Royal Society. A 1788 letter to Henry Cavendish indicated that Michell continued to be interested in geology several decades after his paper on earthquakes. Michell studied magnetism and discovered that the magnetic force exerted by each pole of a magnet decreases according to an inverse-square law, i.e. in proportion to the square of the distance between them. His 1750 paper Treatise of Artificial Magnets, which was written for seamen and instrument makers and intended as a practical manual on how to make magnets, included a list of the "Properties of Magnetical Bodies" that represented a major contribution to the understanding of magnetism. His paper provided the first accurate and comprehensive statement of the law of magnetic force. Michell devised a torsion balance for measuring the mass of the Earth, but died before he could use it. His instrument passed into the hands of his lifelong friend Henry Cavendish, who first performed in 1798 the experiment now known as the Cavendish Experiment. Placing two 1-kg lead balls at the ends of a six-foot rod, he suspended the rod horizontally by a fibre attached to its centre. Then he placed a massive lead ball beside each of the small ones, causing a gravitational attraction that led the rod to turn clockwise. By measuring the rod's movement, Cavendish was able to calculate the force exerted by each of the large balls on the 1-kg balls. From these calculations, he was able to provide an accurate estimate of the gravitational constant and of the mass and average density of the Earth. Cavendish gave Michell full credit for his accomplishment. In 1987, gravity researcher A. H. Cook wrote: The most important advance in experiments on gravitation and other delicate measurements was the introduction of the torsion balance by Michell and its use by Cavendish. It has been the basis of all the most significant experiments on gravitation ever since. Michell was the first person to apply the new mathematics of statistics to the study of the stars, and demonstrated in a 1767 paper that many more stars occur in pairs or groups than a perfectly random distribution could account for. He focused his investigation on the Pleiades cluster, and calculated that the likelihood of finding such a close grouping of stars was about one in half a million. He concluded that the stars in these double or multiple star systems might be drawn to one another by gravitational pull, thus providing the first evidence for the existence of binary stars and star clusters. His work on double stars may have influenced his friend William Herschel's research on the same topic. Another consequence of Michell's statistical work was the realization that fixed luminosity for stars was a poor approximation. Hershel had developed a model of the Milky Way using this approximation and a large number of star directions. While the shape was correct, various appendages to the model were not. The variable luminosity meant the evidence for the edge of the galaxy was suspect and Hershel lost faith in his model.: 6 In a paper for the Philosophical Transactions of the Royal Society of London, read on 27 November 1783, Michell was the first to propose the existence of celestial bodies similar to black holes. Having accepted Newton's corpuscular theory of light, which posited that light consists of minuscule particles, he reasoned that such particles, when emanated by a star, would be slowed down by its gravitational pull, and that it might therefore be possible to determine the star's mass based on the reduction in speed. This insight led in turn to the recognition that a star's gravitational pull might be so strong that the escape velocity would exceed the speed of light. Michell calculated that this would be the case with a star more than 500 times the size of the Sun. Since light would not be able to escape such a star, it would be invisible. In his own words: If there should really exist in nature any bodies, whose density is not less than that of the sun, and whose diameters are more than 500 times the diameter of the sun, since their light could not arrive at us; or if there should exist any other bodies of a somewhat smaller size, which are not naturally luminous; of the existence of bodies under either of these circumstances, we could have no information from sight; yet, if any other luminous bodies should happen to revolve about them we might still perhaps from the motions of these revolving bodies infer the existence of the central ones with some degree of probability, as this might afford a clue to some of the apparent irregularities of the revolving bodies, which would not be easily explicable on any other hypothesis; but as the consequences of such a supposition are very obvious, and the consideration of them somewhat beside my present purpose, I shall not prosecute them any further. — John Michell, 1784 Michell suggested that there might be many such objects in the universe, and today astronomers believe that black holes do indeed exist at the centers of most galaxies. Similarly, Michell proposed that astronomers could detect them by looking for star systems which behaved gravitationally like two stars, but where only one star could be seen. Michell argued that this would show the presence of a star from which light was not escaping. It was an extraordinarily accurate prediction. All of the dozen candidate stellar black holes in our galaxy (the Milky Way) are in X-ray compact binary systems. Michell's ideas about gravity and light interested William Herschel, who tried to test them with his powerful telescopes. A few years after Michell came up with the concept of invisible, light-trapping stars, the French mathematician Pierre-Simon Laplace suggested essentially the same idea in his 1796 book, Exposition du Système du Monde. It has been written that Michell was so far ahead of his time in regard to black holes that the idea "made little impression" on his contemporaries. "He died in quiet obscurity", states the American Physical Society, "and his notion of a 'dark star' was forgotten until his writings re-surfaced in the 1970s." Michell constructed telescopes for his own use. One of them, a reflecting telescope with a 10-foot focal length and a 30-inch aperture, was bought by the distinguished astronomer William Herschel after Michell's death. The two men had many interests in common, and exchanged letters at least twice, but only one record suggests that they ever met. Herschel recorded having visited and seen Michell's telescope while in the area in 1792; Michell was already frail, and his telescope was in disrepair. Herschel bought the telescope the following year, for £30. Other professional activities Michell also wrote a paper on surveying that his biographer has described as "elegant" in theory. Michell was elected a member of the Royal Society. He was first invited to meetings of the Royal Society in 1751 as a guest of Sir George Savile, who would become his patron. He later attended meetings "one to four times a year", while at Cambridge. His paper on the cause of earthquakes was read before the Society beginning on 28 February 1760, leading to a recommendation by Savile and another member that Michell be invited to join the Society. He was elected a member on 12 June 1760. Michell followed his work in seismology with work in astronomy, and after publishing his findings in 1767 he served on an astronomical committee of the Royal Society. More recently, Michell has become known for his letter to Cavendish, published in 1784, on the effect of gravity on light. This paper was rediscovered in the 1970s and is now recognised as anticipating several astronomical ideas that had been considered to be 20th century innovations. Michell is now credited with being the first to study the case of a heavenly object massive enough to prevent light from escaping (the concept of escape velocity was well known at the time). Such an object, often referred to as a dark star, would not be directly visible, but could be identified by the motions of a companion star if it was part of a binary system. The classical minimum radius for escape assuming light behaved like particles of matter is numerically equal to the Schwarzschild radius in general relativity. Michell also suggested using a prism to measure what is now known as gravitational redshift, the gravitational weakening of starlight due to the surface gravity of the source. Michell acknowledged that some of these ideas were not technically practical at the time, but wrote that he hoped they would be useful to future generations. By the time that Michell's paper was rediscovered nearly two centuries later, these ideas had been reinvented by others. Personal life Michell was a man of "wide latitude in religious belief". He was described by a contemporary as "a little short man, of black complexion, and fat", and was "esteemed a very ingenious Man, and an excellent Philosopher." During his years at Thornhill, he welcomed visitors including Benjamin Franklin, Joseph Priestley, Jan Ingenhousz, and Henry Cavendish (the discoverer of hydrogen). Michell wrote to Franklin in 1767 describing his first visit to Thornhill, "the place I told you I was going to remove to". Priestley lived in nearby Birstall for a time. It was at Michell's rectory opposite the church that Priestley and Ingenhousz met for the first time. At the same meeting John Smeaton was introduced to Benjamin Franklin and together they viewed the canal that Smeaton had just finished constructing nearby. Michell also helped Smeaton revise his book on the Eddystone Lighthouse. Michell's first wife was Sarah Williamson (1727–1765), daughter of Luke Williamson and Sutton Holmes, "a young lady of considerable fortune", whom he married in 1764 and who unfortunately died only a year later, in 1765. On 13 February 1773, in Newark, Nottinghamshire, he married Ann Brecknock (1736-1805), daughter of Matthew and Ann Brecknock of Nottinghamshire. They had one child, Mary, who married Sir Thomas Turton of Leeds, son of William Turton Esq. of Kingston Lisle, Berkshire, and Jane Clarke of Hertford, Hertfordshire. Michell's younger brother Gilbert was a merchant in London who later lived with Michell in Thornhill, where the two brothers were active in local real estate, purchasing many properties in the West Riding of Yorkshire. Legacy Michell has been called one of the "greatest unsung scientists of all time". The American Physical Society (APS) described him as being "so far ahead of his scientific contemporaries that his ideas languished in obscurity, until they were re-invented more than a century later". The Society stated that while "he was one of the most brilliant and original scientists of his time, Michell remains virtually unknown today, in part because he did little to develop and promote his own path-breaking ideas". According to another science journalist, "a few specifics of Michell's work really do sound like they are ripped from the pages of a twentieth century astronomy textbook." Michell has been described as arguably having "the broadest competence of any British natural philosopher of the eighteenth century: equally skilled in experiment and observation, mathematical theory, and instruments, his field of inquiry was the universe." Biographies Michell is the subject of the book Weighing the World: The Reverend John Michell of Thornhill (2012) by Russell McCormmach. Selected publications References Sources External links |
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[SOURCE: https://en.wikipedia.org/wiki/PHP] | [TOKENS: 8020] |
Contents PHP PHP is a general-purpose scripting language geared towards web development. It was created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by the PHP Group. PHP was originally an abbreviation of Personal Home Page, but it now stands for the recursive backronym PHP: Hypertext Preprocessor. PHP code is usually processed on a web server by a PHP interpreter implemented as a module, a daemon or a Common Gateway Interface (CGI) executable. On a web server, the result of the interpreted and executed PHP code—which may be any type of data, such as generated HTML or binary image data—can form the whole or part of an HTTP response. Various web template systems, web content management systems, and web frameworks exist that can be employed to orchestrate or facilitate the generation of that response. Additionally, PHP can be used for programming tasks outside the web context, though non-web uses are rare. PHP code can also be directly executed from the command line. The standard PHP interpreter, powered by the Zend Engine, is free software released under the PHP License. PHP has been widely ported and can be deployed on most web servers on a variety of operating systems and platforms. History The PHP language at first evolved without a written formal specification or standard, with the original implementation acting as the de facto standard that other implementations aimed to follow. PHP development began in 1993 when Rasmus Lerdorf wrote several Common Gateway Interface (CGI) programs in C, which he used to maintain his personal homepage. He extended them to work with HTML forms and to communicate with databases, and called this implementation "Personal Home Page/Forms Interpreter" or PHP/FI. An example of the early PHP syntax: PHP/FI could be used to build simple, dynamic web applications. To accelerate bug reporting and improve the code, Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" on the Usenet discussion group comp.infosystems.www.authoring.cgi on 8 June 1995. This release included basic functionality such as Perl-like variables, form handling, and the ability to embed HTML. By this point, the syntax had changed to resemble that of Perl, but was simpler, more limited, and less consistent. Early PHP was never intended to be a new programming language; rather, it grew organically, with Lerdorf noting in retrospect: "I don't know how to stop it [...] there was never any intent to write a programming language [...] I have absolutely no idea how to write a programming language [...] I just kept adding the next logical step on the way." A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997. The fact that PHP was not originally designed, but instead was developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters. In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping", while in some very early versions of PHP the length of the function names was used internally as a hash function, so names were chosen to improve the distribution of hash values. Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive acronym PHP: Hypertext Preprocessor. Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend Engine in 1999. They also founded Zend Technologies in Ramat Gan, Israel. On 22 May 2000, PHP 4.0, powered by the Zend Engine 1.0, was released. By August 2008, this branch had reached version 4.4.9. PHP 4 is now no longer under development and nor are any security updates planned to be released. On 1 July 2004, PHP 5.0 was released, powered by the new Zend Engine 2.0. PHP 5.0 included significant changes to the language, most notably an overhauled approach to object-oriented programming, as well as iterators and exceptions. PHP 5.1 and PHP 5.2 were released the following years, adding smaller improvements and new features, such as the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases) In 2008, PHP 5.x became the only stable version under development. Many high-profile open-source projects ceased to support PHP 4 in new code from February 5, 2008, because of the GoPHP5 initiative, provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5. PHP's native string functions worked only on raw bytes, making use with multibyte character encodings difficult. In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the International Components for Unicode (ICU) library, and representing text strings as UTF-16 internally. Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development. However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project. As a result, a PHP 5.3 release was created in 2009, and in March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared to contain most remaining non-Unicode features from PHP 6. Initial hopes were that a new plan would be formed for Unicode integration, but by 2014 none had been adopted.[citation needed] Because it contained features originally intended to be part of 6.0, PHP 5.3 was a significant release, adding support for namespaces, closures, late static binding, and many fixes and improvements to standard functions. With the Unicode branch officially abandoned, a new release process was adopted in 2011, planning a yearly release cycle, and a clear distinction between "feature releases" (x.y.z to x.y+1.z) and "major releases" (x.y.z to x+1.0.0). Remaining features which had been planned for the 6.0 release were included in PHP 5.4, released in March 2012, such as trait support and a new "short array syntax". This was followed by more incremental changes in PHP 5.5 (June 2013) and 5.6 (August 2014). For PHP versions 5.3 and 5.4, the only available Microsoft Windows binary distributions were 32-bit IA-32 builds, requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit x86-64 builds available for Microsoft Windows. Official security support for PHP 5.6 ended on 31 December 2018. During 2014 and 2015, a new major PHP version was developed, PHP 7.0. The numbering of this version involved some debate among internal developers. While the PHP 6 Unicode experiments had never been released, several articles and book titles referenced the PHP 6 names, which might have caused confusion if a new release were to reuse the name. After a vote, the name PHP 7 was chosen. The foundation of PHP 7.0 was a PHP branch that was originally dubbed PHP next generation (phpng). It was written by Dmitry Stogov, Xinchen Hui and Nikita Popov, and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility. By 14 July 2014, WordPress-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng make it easier to improve performance in future versions, as more compact data structures and other changes are seen as better suited for a successful migration to a just-in-time (JIT) compiler. Because of the significant changes, the reworked Zend Engine was called Zend Engine 3, succeeding Zend Engine 2 used in PHP 5.x. PHP 7.0 also included changes which were not backwards compatible, as allowed for "major versions" under the versioning scheme agreed in 2011. Changes to the core language included a more consistent handling of variable dereferencing, a more predictable behavior of the foreach statement, and platform consistency of bitwise shifts and floating-point to integer conversion. Several unmaintained or deprecated server application programming interfaces (SAPIs) and extensions were removed from the PHP core, most notably the legacy mysql extension. Other legacy features were also removed, such as ASP-style delimiters <% and %> and <script language="php"> ... </script>. PHP 7.0 marked the beginning of an expansion in PHP's type system. In PHP 5.x, only function parameters could have type declarations, but this was extended to function return types in 7.0., and object properties in 7.4 The types expressible also expanded, with scalar types (integer, float, string, and boolean) in 7.0; iterable type, nullable types, and void return type. all in 7.1; and the object type in 7.2 Other changes in this period aimed to add expressiveness to the language, such as the ?? (null coalesce) and <=> "spaceship" three-way comparison operators in 7.0; new syntax for array derefencing and catching multiple exception types in PHP 7.1; more flexible Heredoc and Nowdoc syntax in 7.3; and the null-coalescing assignment operator in 7.4. PHP 8.0 was released on 26 November 2020, as a major version with breaking changes from previous versions. One of the most high-profile changes was the addition of a JIT compiler, which can provide substantial performance improvements for some use cases. Substantial improvements were expected more for mathematical-type operations than for common web-development use cases. Additionally, the performance advantage of the JIT compiler provides the potential to move some code from C to PHP. A significant addition to the language in 8.0 is attributes, which allow metadata to be added to program elements such as classes, methods, and parameters. Later versions added built-in attributes which change the behaviour of the language, such as the #[\SensitiveParameter] attribute in PHP 8.2, #[\Override] in PHP 8.3, #[\Deprecated] in PHP 8.4, and the #[\NoDiscard] and #[\DelayedTargetValidation] attributes in PHP 8.5. A significant extension to the language's type system is the addition of composite types: union types in PHP 8.0 (e.g. int|string meaning "either integer or string), intersection types in PHP 8.1 (e.g. Traversable&Countable meaning the value must implement both the Traversable and Countable interfaces), and disjunctive normal form (DNF) types in PHP 8.2 (unions of intersections, such as array|(Traversable&Countable)). Additional special type keywords have been added, such as mixed and static in PHP 8.0, never (a bottom type indicating that a function never returns) in PHP 8.1, and null, false, and true as stand-alone types in PHP 8.2. The addition of a rich type system is part of a general trend towards a stricter language, and PHP 8.0 included breaking changes to the handling of string to number comparisons, numeric strings, and incompatible method signatures. Later versions have introduced deprecation notices for behaviour which is planned as a breaking change in a future major version, such as passing null to non-nullable internal function parameters and referring to properties which have not been declared on the class. Beginning on 28 June 2011, the PHP Development Team implemented a timeline for the release of new versions of PHP. Under this system, at least one release should occur every month. Once per year, a minor release should occur which may include new features. Every minor release should at least be supported for two years with security and bug fixes, followed by at least one year of only security fixes, for a total of a three-year release process for every minor release. No new features, unless small and self-contained, are to be introduced into a minor release during the three-year release process. A 2024 RFC extended the length of the security fix only period to two years, fixed all end of life dates to 31 December, and removed the exception that allowed for "small and self-contained" features to be introduced in patch versions. W3Techs reports that as of November 2025[update] (about three years since PHP 7 was discontinued and 23 months after the PHP 8.3 release), unsupported versions such as PHP 7 are still used by well over half of PHP websites, which are outdated and known to be insecure. Those included the 9.7% of PHP websites using the even more outdated (discontinued for 7 years) and insecure PHP 5, released over two decades ago. Mascot The mascot of the PHP project is the elePHPant, a blue elephant with the PHP logo on its side, designed by Vincent Pontier in 1998. "The (PHP) letters were forming the shape of an elephant if viewed in a sideways angle." The elePHPant is sometimes differently coloured when in plush toy form. Many variations of this physical mascot have been made over the years. Only the elePHPants based on the original design by Vincent Pontier are considered official by the community. These are collectable and some of them are extremely rare. Syntax The following "Hello, World!" program is written in PHP code embedded in an HTML document: The PHP interpreter only executes PHP code within its delimiters. Anything outside of its delimiters is not processed by PHP, although the non-PHP text can still be subject to control structures described in PHP code. The most common delimiters are <?php to open and ?> to close PHP sections; the shortened form <? also exists. This short delimiter makes script files less portable since support can be disabled in the local PHP configuration and it is therefore discouraged. Conversely, there is no recommendation against the echo short tag <?=. Prior to PHP 5.4.0, this short syntax for echo only works with the short_open_tag configuration setting enabled, while for PHP 5.4.0 and later it is always available. The purpose of all these delimiters is to separate PHP code from non-PHP content, such as JavaScript code or HTML markup. The first form of delimiters, <?php and ?>, in XHTML and other XML documents, creates correctly formed XML processing instructions. This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML. Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. PHP 5 introduced type declarations that allow functions to force their parameters to be objects of a specific class, arrays, interfaces or callback functions. However, before PHP 7, type declarations could not be used with scalar types such as integers or strings. Below is an example of how PHP variables are declared and initialized. Unlike function and class names, variable names are case-sensitive. Both double-quoted ("") and heredoc strings provide the ability to interpolate a variable's value into the string. PHP treats newlines as whitespace in the manner of a free-form language, and statements are terminated by a semicolon. PHP has three types of comment syntax: /* */ marks block and inline comments; // or # are used for one-line comments. The echo statement is one of several facilities PHP provides to output text.[citation needed] In terms of keywords and language syntax, PHP is similar to C-style syntax. if conditions, for and while loops and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.[citation needed] PHP is loosely typed. It stores integers in a platform-dependent range, either as a 32, 64 or 128-bit signed integer equivalent to the C-language long type. Unsigned integers are converted to signed values in certain situations, which is different behaviour to many other programming languages. Integer variables can be assigned using decimal (positive and negative), octal, hexadecimal, and binary notations. Floating-point numbers are also stored in a platform-specific range. They can be specified using floating-point notation, or two forms of scientific notation. PHP has a native Boolean type that is similar to the native Boolean types in Java and C++. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in Perl and C++. The null data type represents a variable that has no value; NULL is the only allowed value for this data type. Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources. Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in hashes with both keys and values, and the two can be intermingled. PHP also supports strings, which can be used with single quotes, double quotes, nowdoc or heredoc syntax. The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes. PHP defines a large array of functions in the core language and many are also available in various extensions; these functions are well documented online PHP documentation. However, the built-in library has a wide variety of naming conventions and associated inconsistencies, as described under history above. Custom functions may be defined by the developer: As of 2026, the output of the above sample program is "I am currently 31 years old." In lieu of function pointers, functions in PHP can be referenced by a string containing their name. In this manner, normal PHP functions can be used, for example, as callbacks or within function tables. User-defined functions may be created at any time without being prototyped. Functions may be defined inside code blocks, permitting a run-time decision as to whether or not a function should be defined. There is a function_exists function that determines whether a function with a given name has already been defined. Function calls must use parentheses, with the exception of zero-argument class constructor functions called with the PHP operator new, in which case parentheses are optional.[citation needed] Since PHP 4.0.1 create_function(), a thin wrapper around eval(), allowed normal PHP functions to be created during program execution; it was deprecated in PHP 7.2 and removed in PHP 8.0 in favor of syntax for anonymous functions or "closures" that can capture variables from the surrounding scope, which was added in PHP 5.3. Shorthand arrow syntax was added in PHP 7.4: In the example above, getAdder() function creates a closure using passed argument $x, which takes an additional argument $y, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as a parameter to other functions, etc. Unusually for a dynamically typed language, PHP supports type declarations on function parameters, which are enforced at runtime. This has been supported for classes and interfaces since PHP 5.0, for arrays since PHP 5.1, for "callables" since PHP 5.4, and scalar (integer, float, string and boolean) types since PHP 7.0. PHP 7.0 also has type declarations for function return types, expressed by placing the type name after the list of parameters, preceded by a colon. For example, the getAdder function from the earlier example could be annotated with types like so in PHP 7: By default, scalar type declarations follow weak typing principles. So, for example, if a parameter's type is int, PHP would allow not only integers, but also convertible numeric strings, floats or Booleans to be passed to that function, and would convert them. However, PHP 7 has a "strict typing" mode which, when used, disallows such conversions for function calls and returns within a file. Basic object-oriented programming functionality was added in PHP 3 and improved in PHP 4. This allowed for PHP to gain further abstraction, making creative tasks easier for programmers using the language. Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance. In previous versions of PHP, objects were handled like value types. The drawback of this method was that code had to make heavy use of PHP's "reference" variables if it wanted to modify an object it was passed rather than creating a copy of it. In the new approach, objects are referenced by handle, and not by value. PHP 5 introduced private and protected member variables and methods, along with abstract classes, final classes, abstract methods, and final methods. It also introduced a standard way of declaring constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception handling model. Furthermore, PHP 5 added interfaces and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach language construct. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference at compile time. If the developer creates a copy of an object using the reserved word clone, the Zend engine will check whether a __clone() method has been defined. If not, it will call a default __clone() which will copy the object's properties. If a __clone() method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so the programmer can start with a by-value replica of the source object and only override properties that need to be changed. The visibility of PHP properties and methods is defined using the keywords public, private, and protected. The default is public, if only var is used; var is a synonym for public. Items declared public can be accessed everywhere. protected limits access to inherited classes (and to the class that defines the item). private limits visibility only to the class that defines the item. Objects of the same type have access to each other's private and protected members even though they are not the same instance. The following is a basic example of object-oriented programming in PHP 8: This program outputs the following: Implementations The only complete PHP implementation is the original, known simply as PHP. It is the most widely used and is powered by the Zend Engine. To disambiguate it from other implementations, it is sometimes unofficially called "Zend PHP". The Zend Engine compiles PHP source code on-the-fly into an internal format that it can execute, thus it works as an interpreter. It is also the "reference implementation" of PHP, as PHP has no formal specification, and so the semantics of Zend PHP define the semantics of PHP. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility. PHP's single-request-per-script-execution model, and the fact that the Zend Engine is an interpreter, leads to inefficiency; as a result, various products have been developed to help improve PHP performance. In order to speed up execution time and not have to compile the PHP source code every time the web page is accessed, PHP scripts can also be deployed in the PHP engine's internal format by using an opcode cache, which works by caching the compiled form of a PHP script (opcodes) in shared memory to avoid the overhead of parsing and compiling the code every time the script runs. An opcode cache, Zend Opcache, is built into PHP since version 5.5. Another example of a widely used opcode cache is the Alternative PHP Cache (APC), which is available as a PECL extension. While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these are compilers or support JIT compilation, and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility.[citation needed] Alternative implementations include the following: Licensing PHP is free software released under the PHP License, which stipulates that: Products derived from this software may not be called "PHP", nor may "PHP" appear in their name, without prior written permission from group@php.net. You may indicate that your software works in conjunction with PHP by saying "Foo for PHP" instead of calling it "PHP Foo" or "phpfoo". This restriction on the use of "PHP" makes the PHP License incompatible with the GNU General Public License (GPL), while the Zend License is incompatible due to an advertising clause similar to that of the original BSD license. Development and community PHP includes various free and open-source libraries in its source distribution or uses them in resulting PHP binary builds. PHP is fundamentally an Internet-aware system with built-in modules for accessing File Transfer Protocol (FTP) servers and many database servers, including PostgreSQL, MySQL, Microsoft SQL Server and SQLite (which is an embedded database), LDAP servers, and others. Numerous functions are familiar to C programmers, such as those in the stdio family, are available in standard PHP builds. PHP allows developers to write extensions in C to add functionality to the PHP language. PHP extensions can be compiled statically into PHP or loaded dynamically at runtime. Numerous extensions have been written to add support for the Windows API, process management on Unix-like operating systems, multibyte strings (Unicode), cURL, and several popular compression formats. Other PHP features made available through extensions include integration with Internet Relay Chat (IRC), dynamic generation of images and Adobe Flash content, PHP Data Objects (PDO) as an abstraction layer used for accessing databases, and even speech synthesis. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions. The PHP Extension Community Library (PECL) project is a repository for extensions to the PHP language. Most of the community focuses on web development, and PHP running server side (though also serving JavaScript for the client side), and some exceptional uses are for e.g. standalone graphical applications (with PHP-GTK unmaintained now for over a decade), and even drone control. Some other projects, such as Zephir, provide the ability for PHP extensions to be created in a high-level language and compiled into native PHP extensions. Such an approach, instead of writing PHP extensions directly in C, simplifies the development of extensions and reduces the time required for programming and testing. By December 2018 the PHP Group consisted of ten people: Thies C. Arntzen, Stig Bakken, Shane Caraveo, Andi Gutmans, Rasmus Lerdorf, Sam Ruby, Sascha Schumann, Zeev Suraski, Jim Winstead, and Andrei Zmievski. Zend Technologies provides a PHP Certification based on PHP 8 exam (and previously based on PHP 7 and 5.5) for programmers to become certified PHP developers. The PHP Foundation On 26 November 2021, the JetBrains blog announced the creation of The PHP Foundation, which will sponsor the design and development of PHP. The foundation hires "Core Developers" to work on the PHP language's core repository. Roman Pronskiy, a member of the foundation's board, said that they aim to pay "market salaries" to developers. The response to the foundation has been largely positive, with commentators praising its role in ensuring the continued development of PHP and helping to stabilise the language's community and popularity. Germany's Sovereign Tech Fund provided more than 200,000 Euros to support the PHP Foundation. Installation and configuration There are two primary ways for adding support for PHP to a web server – as a native web server module, or as a CGI executable. PHP has a direct module interface called server application programming interface (SAPI), which is supported by many web servers including Apache HTTP Server, Microsoft IIS, Caddy (through FrankenPHP) and iPlanet Web Server. Some other web servers, such as OmniHTTPd, support the Internet Server Application Programming Interface (ISAPI), which is Microsoft's web server module interface. If PHP has no module support for a web server, it can always be used as a Common Gateway Interface (CGI) or FastCGI processor; in that case, the web server is configured to use PHP's CGI executable to process all requests to PHP files. PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the official PHP distribution since version 5.3.3. When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers. When using PHP for command-line scripting, a PHP command-line interface (CLI) executable is needed. PHP supports a CLI server application programming interface (SAPI) since PHP 4.3.0. The main focus of this SAPI is developing shell applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviours. PHP has a direct module interface called SAPI for different web servers; in case of PHP 5 and Apache 2.0 on Windows, it is provided in form of a DLL file called php5apache2.dll, which is a module that, among other functions, provides an interface between PHP and the web server, implemented in a form that the server understands. This form is what is known as a SAPI.[citation needed] There are different kinds of SAPIs for various web server extensions. For example, in addition to those listed above, other SAPIs for the PHP language include the Common Gateway Interface and command-line interface. PHP can also be used for writing desktop graphical user interface (GUI) applications, by using the "PHP Desktop". GitHub. or discontinued PHP-GTK extension. PHP-GTK is not included in the official PHP distribution, and as an extension, it can be used only with PHP versions 5.1.0 and newer. The most common way of installing PHP-GTK is by compiling it from the source code. When PHP is installed and used in cloud environments, software development kits (SDKs) are provided for using cloud-specific features. For example: Numerous configuration options are supported, affecting both core PHP features and extensions. Configuration file php.ini is searched for in different locations, depending on the way PHP is used. The configuration file is split into various sections, while some of the configuration options can be also set within the web server configuration. Use PHP is a general-purpose scripting language that is especially suited to server-side web development, in which case PHP generally runs on a web server. Any PHP code in a requested file is executed by the PHP runtime, usually to create dynamic web page content or dynamic images used on websites or elsewhere. It can also be used for command-line scripting and client-side graphical user interface (GUI) applications. PHP can be deployed on most web servers, many operating systems and platforms, and can be used with many relational database management systems (RDBMS). Most web hosting providers support PHP for use by their clients. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use. Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting, and it is similar to other server-side scripting languages that provide dynamic content from a web server to a client, such as Python, Microsoft's ASP.NET, Sun Microsystems' JavaServer Pages, and mod_perl. PHP has also attracted the development of many software frameworks that provide building blocks and a design structure to promote rapid application development (RAD).[citation needed] Some of these include PRADO, CakePHP, Symfony, CodeIgniter, Laravel, Yii Framework, Phalcon and Laminas, offering features similar to other web frameworks. The LAMP architecture has become popular in the web industry as a way of deploying web applications. PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer to Python, Perl, or some mix of the three. Similar packages, WAMP and MAMP, are also available for Windows and macOS, with the first letter standing for the respective operating system. Although both PHP and Apache are provided as part of the macOS base install, users of these packages seek a simpler installation mechanism that can be more easily kept up to date.[citation needed] For specific and more advanced usage scenarios, PHP offers a well-defined and documented way for writing custom extensions in C or C++.[non-primary source needed] Besides extending the language itself in form of additional libraries, extensions are providing a way for improving execution speed where it is critical and there is room for improvements by using a true compiled language. PHP also offers well-defined ways for embedding itself into other software projects. That way PHP can be easily used as an internal scripting language for another project, also providing tight interfacing with the project's specific internal data structures. PHP received mixed reviews due to lacking support for multithreading at the core language level, though using threads is made possible by the "pthreads" PECL extension. A command line interface, php-cli, and two ActiveX Windows Script Host scripting engines for PHP have been produced.[citation needed] PHP is used for Web content management systems including MediaWiki, WordPress, Joomla, Drupal, Moodle, eZ Publish, eZ Platform, and SilverStripe. As of January 2013[update], PHP was used in more than 240 million websites (39% of those sampled) and was installed on 2.1 million web servers. As of 20 February 2026[update] (three months after PHP 8.5's release), PHP is used as the server-side programming language on 72% of websites where the language could be determined; PHP 8 is the most used version of the language with 56.6% of websites using PHP being on that version, while 34.3% use PHP 7, 9% use PHP 5 and 0.1% use PHP 4. Security In 2019, 11% of all vulnerabilities listed by the National Vulnerability Database were linked to PHP; historically, about 30% of all vulnerabilities listed since 1996 in this database are linked to PHP. Technical security flaws of the language itself or of its core libraries are not frequent (22 in 2009, about 1% of the total although PHP applies to about 20% of programs listed). Recognizing that programmers make mistakes, some languages include taint checking to automatically detect the lack of input validation which induces many issues. Such a feature has been proposed for PHP in the past, but either been rejected or the proposal abandoned. Third-party projects such as Suhosin and Snuffleupagus aim to remove or change dangerous parts of the language. Historically, old versions of PHP had some configuration parameters and default values for such runtime settings that made some PHP applications prone to security issues. Among these, magic_quotes_gpc and register_globals configuration directives were the best known; the latter made any URL parameters become PHP variables, opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script. Support for "magic quotes" and "register globals" settings has been deprecated since PHP 5.3.0, and removed from PHP 5.4.0. Another example for the potential runtime-settings vulnerability comes from failing to disable PHP execution (for example by using the engine configuration directive) for the directory where uploaded files are stored; enabling it can result in the execution of malicious code embedded within the uploaded files. The best practice is to either locate the image directory outside of the document root available to the web server and serve it via an intermediary script or disable PHP execution for the directory which stores the uploaded files.[citation needed] Also, enabling the dynamic loading of PHP extensions (via enable_dl configuration directive) in a shared web hosting environment can lead to security issues. Implied type conversions that result in different values being treated as equal, sometimes against the programmer's intent, can lead to security issues. For example, the result of the comparison '0e1234' == '0' is true, because strings that are parsable as numbers are converted to numbers; in this case, the first compared value is treated as scientific notation having the value (0×101234), which is zero. Errors like this resulted in authentication vulnerabilities in Simple Machines Forum, Typo3 and phpBB when MD5 password hashes were compared. The recommended way is to use hash_equals() (for timing attack safety), strcmp or the identity operator (===), as '0e1234' === '0' results in false.[citation needed] In a 2013 analysis of over 170,000 website defacements, published by Zone-H, the most frequently (53%) used technique was the exploitation of file inclusion vulnerability, mostly related to insecure usage of the PHP language constructs include, require, and allow_url_fopen. PHP includes rand() and mt_rand() functions which use a pseudorandom number generator, and are not cryptographically secure. As of version 8.1, the random_int() function is included, which uses a cryptographically secure source of randomness provided by the system. There are two attacks that can be performed over PHP entropy sources: "seed attack" and "state recovery attack".[citation needed] As of 2012, a $250 GPU can perform up to 230 MD5 calculations per second, while a $750 GPU can perform four times as many calculations at the same time. In combination with a "birthday attack" this can lead to serious security vulnerabilities.[citation needed] The PHP development team provides official bug fixes for two years following release of each minor version followed by another two years where only security fixes are released. After this, the release is considered end of life and no longer officially supported. Extended long-term support beyond this is available from commercial providers, such as Zend and others See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Orion_(constellation)#cite_ref-pa30_469_3-0] | [TOKENS: 4993] |
Contents Orion (constellation) Orion is a prominent set of stars visible during winter in the northern celestial hemisphere. It is one of the 88 modern constellations; it was among the 48 constellations listed by the 2nd-century AD/CE astronomer Ptolemy. It is named after a hunter in Greek mythology. Orion is most prominent during winter evenings in the Northern Hemisphere, as are five other constellations that have stars in the Winter Hexagon asterism. Orion's two brightest stars, Rigel (β) and Betelgeuse (α), are both among the brightest stars in the night sky; both are supergiants and slightly variable. There are a further six stars brighter than magnitude 3.0, including three making the short straight line of the Orion's Belt asterism. Orion also hosts the radiant of the annual Orionids, the strongest meteor shower associated with Halley's Comet, and the Orion Nebula, one of the brightest nebulae in the sky. Characteristics Orion is bordered by Taurus to the northwest, Eridanus to the southwest, Lepus to the south, Monoceros to the east, and Gemini to the northeast. Covering 594 square degrees, Orion ranks 26th of the 88 constellations in size. The constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 26 sides. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 04h 43.3m and 06h 25.5m , while the declination coordinates are between 22.87° and −10.97°. The constellation's three-letter abbreviation, as adopted by the International Astronomical Union in 1922, is "Ori". Orion is most visible in the evening sky from January to April, winter in the Northern Hemisphere, and summer in the Southern Hemisphere. In the tropics (less than about 8° from the equator), the constellation transits at the zenith. From May to July (summer in the Northern Hemisphere, winter in the Southern Hemisphere), Orion is in the daytime sky and thus invisible at most latitudes. However, for much of Antarctica in the Southern Hemisphere's winter months, the Sun is below the horizon even at midday. Stars (and thus Orion, but only the brightest stars) are then visible at twilight for a few hours around local noon, just in the brightest section of the sky low in the North where the Sun is just below the horizon. At the same time of day at the South Pole itself (Amundsen–Scott South Pole Station), Rigel is only 8° above the horizon, and the Belt sweeps just along it. In the Southern Hemisphere's summer months, when Orion is normally visible in the night sky, the constellation is actually not visible in Antarctica because the Sun does not set at that time of year south of the Antarctic Circle. In countries close to the equator (e.g. Kenya, Indonesia, Colombia, Ecuador), Orion appears overhead in December around midnight and in the February evening sky. Navigational aid Orion is very useful as an aid to locating other stars. By extending the line of the Belt southeastward, Sirius (α CMa) can be found; northwestward, Aldebaran (α Tau). A line eastward across the two shoulders indicates the direction of Procyon (α CMi). A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Rigel is part of the Winter Circle asterism. Sirius and Procyon, which may be located from Orion by following imaginary lines (see map), also are points in both the Winter Triangle and the Circle. Features Orion's seven brightest stars form a distinctive hourglass-shaped asterism, or pattern, in the night sky. Four stars—Rigel, Betelgeuse, Bellatrix, and Saiph—form a large roughly rectangular shape, at the center of which lie the three stars of Orion's Belt—Alnitak, Alnilam, and Mintaka. His head is marked by an additional eighth star called Meissa, which is fairly bright to the observer. Descending from the Belt is a smaller line of three stars, Orion's Sword (the middle of which is in fact not a star but the Orion Nebula), also known as the hunter's sword. Many of the stars are luminous hot blue supergiants, with the stars of the Belt and Sword forming the Orion OB1 association. Standing out by its red hue, Betelgeuse may nevertheless be a runaway member of the same group. Orion's Belt, or The Belt of Orion, is an asterism within the constellation. It consists of three bright stars: Alnitak (Zeta Orionis), Alnilam (Epsilon Orionis), and Mintaka (Delta Orionis). Alnitak is around 800 light-years away from Earth, 100,000 times more luminous than the Sun, and shines with a magnitude of 1.8; much of its radiation is in the ultraviolet range, which the human eye cannot see. Alnilam is approximately 2,000 light-years from Earth, shines with a magnitude of 1.70, and with an ultraviolet light that is 375,000 times more luminous than the Sun. Mintaka is 915 light-years away and shines with a magnitude of 2.21. It is 90,000 times more luminous than the Sun and is a double star: the two orbit each other every 5.73 days. In the Northern Hemisphere, Orion's Belt is best visible in the night sky during the month of January at around 9:00 pm, when it is approximately around the local meridian. Just southwest of Alnitak lies Sigma Orionis, a multiple star system composed of five stars that have a combined apparent magnitude of 3.7 and lying at a distance of 1150 light-years. Southwest of Mintaka lies the quadruple star Eta Orionis. Orion's Sword contains the Orion Nebula, the Messier 43 nebula, Sh 2-279 (also known as the Running Man Nebula), and the stars Theta Orionis, Iota Orionis, and 42 Orionis. Three stars comprise a small triangle that marks the head. The apex is marked by Meissa (Lambda Orionis), a hot blue giant of spectral type O8 III and apparent magnitude 3.54, which lies some 1100 light-years distant. Phi-1 and Phi-2 Orionis make up the base. Also nearby is the young star FU Orionis. Stretching north from Betelgeuse are the stars that make up Orion's club. Mu Orionis marks the elbow, Nu and Xi mark the handle of the club, and Chi1 and Chi2 mark the end of the club. Just east of Chi1 is the Mira-type variable red giant star U Orionis. West from Bellatrix lie six stars all designated Pi Orionis (π1 Ori, π2 Ori, π3 Ori, π4 Ori, π5 Ori, and π6 Ori) which make up Orion's shield. Around 20 October each year, the Orionid meteor shower (Orionids) reaches its peak. Coming from the border with the constellation Gemini, as many as 20 meteors per hour can be seen. The shower's parent body is Halley's Comet. Hanging from Orion's Belt is his sword, consisting of the multiple stars θ1 and θ2 Orionis, called the Trapezium and the Orion Nebula (M42). This is a spectacular object that can be clearly identified with the naked eye as something other than a star. Using binoculars, its clouds of nascent stars, luminous gas, and dust can be observed. The Trapezium cluster has many newborn stars, including several brown dwarfs, all of which are at an approximate distance of 1,500 light-years. Named for the four bright stars that form a trapezoid, it is largely illuminated by the brightest stars, which are only a few hundred thousand years old. Observations by the Chandra X-ray Observatory show both the extreme temperatures of the main stars—up to 60,000 kelvins—and the star forming regions still extant in the surrounding nebula. M78 (NGC 2068) is a nebula in Orion. With an overall magnitude of 8.0, it is significantly dimmer than the Great Orion Nebula that lies to its south; however, it is at approximately the same distance, at 1600 light-years from Earth. It can easily be mistaken for a comet in the eyepiece of a telescope. M78 is associated with the variable star V351 Orionis, whose magnitude changes are visible in very short periods of time. Another fairly bright nebula in Orion is NGC 1999, also close to the Great Orion Nebula. It has an integrated magnitude of 10.5 and is 1500 light-years from Earth. The variable star V380 Orionis is embedded in NGC 1999. Another famous nebula is IC 434, the Horsehead Nebula, near Alnitak (Zeta Orionis). It contains a dark dust cloud whose shape gives the nebula its name. NGC 2174 is an emission nebula located 6400 light-years from Earth. Besides these nebulae, surveying Orion with a small telescope will reveal a wealth of interesting deep-sky objects, including M43, M78, and multiple stars including Iota Orionis and Sigma Orionis. A larger telescope may reveal objects such as the Flame Nebula (NGC 2024), as well as fainter and tighter multiple stars and nebulae. Barnard's Loop can be seen on very dark nights or using long-exposure photography. All of these nebulae are part of the larger Orion molecular cloud complex, which is located approximately 1,500 light-years away and is hundreds of light-years across. Due to its proximity, it is one of the most intense regions of stellar formation visible from Earth. The Orion molecular cloud complex forms the eastern part of an even larger structure, the Orion–Eridanus Superbubble, which is visible in X-rays and in hydrogen emissions. History and mythology The distinctive pattern of Orion is recognized in numerous cultures around the world, and many myths are associated with it. Orion is used as a symbol in the modern world. In Siberia, the Chukchi people see Orion as a hunter; an arrow he has shot is represented by Aldebaran (Alpha Tauri), with the same figure as other Western depictions. In Greek mythology, Orion was a gigantic, supernaturally strong hunter, born to Euryale, a Gorgon, and Poseidon (Neptune), god of the sea. One myth recounts Gaia's rage at Orion, who dared to say that he would kill every animal on Earth. The angry goddess tried to dispatch Orion with a scorpion. This is given as the reason that the constellations of Scorpius and Orion are never in the sky at the same time. However, Ophiuchus, the Serpent Bearer, revived Orion with an antidote. This is said to be the reason that the constellation of Ophiuchus stands midway between the Scorpion and the Hunter in the sky. The constellation is mentioned in Horace's Odes (Ode 3.27.18), Homer's Odyssey (Book 5, line 283) and Iliad, and Virgil's Aeneid (Book 1, line 535). In old Hungarian tradition, Orion is known as "Archer" (Íjász), or "Reaper" (Kaszás). In recently rediscovered myths, he is called Nimrod (Hungarian: Nimród), the greatest hunter, father of the twins Hunor and Magor. The π and o stars (on upper right) form together the reflex bow or the lifted scythe. In other Hungarian traditions, Orion's Belt is known as "Judge's stick" (Bírópálca). In Ireland and Scotland, Orion was called An Bodach, a figure from Irish folklore whose name literally means "the one with a penis [bod]" and was the husband of the Cailleach (hag). In Scandinavian tradition, Orion's Belt was known as "Frigg's Distaff" (friggerock) or "Freyja's distaff". The Finns call Orion's Belt and the stars below it "Väinämöinen's scythe" (Väinämöisen viikate). Another name for the asterism of Alnilam, Alnitak, and Mintaka is "Väinämöinen's Belt" (Väinämöisen vyö) and the stars "hanging" from the Belt as "Kaleva's sword" (Kalevanmiekka). There are claims in popular media that the Adorant from the Geißenklösterle cave, an ivory carving estimated to be 35,000 to 40,000 years old, is the first known depiction of the constellation. Scholars dismiss such interpretations, saying that perceived details such as a belt and sword derive from preexisting features in the grain structure of the ivory. The Babylonian star catalogues of the Late Bronze Age name Orion MULSIPA.ZI.AN.NA,[note 1] "The Heavenly Shepherd" or "True Shepherd of Anu" – Anu being the chief god of the heavenly realms. The Babylonian constellation is sacred to Papshukal and Ninshubur, both minor gods fulfilling the role of "messenger to the gods". Papshukal is closely associated with the figure of a walking bird on Babylonian boundary stones, and on the star map the figure of the Rooster is located below and behind the figure of the True Shepherd—both constellations represent the herald of the gods, in his bird and human forms respectively. In ancient Egypt, the stars of Orion were regarded as a god, called Sah. Because Orion rises before Sirius, the star whose heliacal rising was the basis for the Solar Egyptian calendar, Sah was closely linked with Sopdet, the goddess who personified Sirius. The god Sopdu is said to be the son of Sah and Sopdet. Sah is syncretized with Osiris, while Sopdet is syncretized with Osiris' mythological wife, Isis. In the Pyramid Texts, from the 24th and 23rd centuries BC, Sah is one of many gods whose form the dead pharaoh is said to take in the afterlife. The Armenians identified their legendary patriarch and founder Hayk with Orion. Hayk is also the name of the Orion constellation in the Armenian translation of the Bible. The Bible mentions Orion three times, naming it "Kesil" (כסיל, literally – fool). Though, this name perhaps is etymologically connected with "Kislev", the name for the ninth month of the Hebrew calendar (i.e. November–December), which, in turn, may derive from the Hebrew root K-S-L as in the words "kesel, kisla" (כֵּסֶל, כִּסְלָה, hope, positiveness), i.e. hope for winter rains.: Job 9:9 ("He is the maker of the Bear and Orion"), Job 38:31 ("Can you loosen Orion's belt?"), and Amos 5:8 ("He who made the Pleiades and Orion"). In ancient Aram, the constellation was known as Nephîlā′, the Nephilim are said to be Orion's descendants. In medieval Muslim astronomy, Orion was known as al-jabbar, "the giant". Orion's sixth brightest star, Saiph, is named from the Arabic, saif al-jabbar, meaning "sword of the giant". In China, Orion was one of the 28 lunar mansions Sieu (Xiù) (宿). It is known as Shen (參), literally meaning "three", for the stars of Orion's Belt. The Chinese character 參 (pinyin shēn) originally meant the constellation Orion (Chinese: 參宿; pinyin: shēnxiù); its Shang dynasty version, over three millennia old, contains at the top a representation of the three stars of Orion's Belt atop a man's head (the bottom portion representing the sound of the word was added later). The Rigveda refers to the constellation as Mriga (the Deer). Nataraja, "the cosmic dancer", is often interpreted as the representation of Orion. Rudra, the Rigvedic form of Shiva, is the presiding deity of Ardra nakshatra (Betelgeuse) of Hindu astrology. The Jain Symbol carved in the Udayagiri and Khandagiri Caves, India in 1st century BCE has a striking resemblance with Orion. Bugis sailors identified the three stars in Orion's Belt as tanra tellué, meaning "sign of three". The Seri people of northwestern Mexico call the three stars in Orion's Belt Hapj (a name denoting a hunter) which consists of three stars: Hap (mule deer), Haamoja (pronghorn), and Mojet (bighorn sheep). Hap is in the middle and has been shot by the hunter; its blood has dripped onto Tiburón Island. The same three stars are known in Spain and most of Latin America as "Las tres Marías" (Spanish for "The Three Marys"). In Puerto Rico, the three stars are known as the "Los Tres Reyes Magos" (Spanish for The Three Wise Men). The Ojibwa/Chippewa Native Americans call this constellation Mesabi for Big Man. To the Lakota Native Americans, Tayamnicankhu (Orion's Belt) is the spine of a bison. The great rectangle of Orion is the bison's ribs; the Pleiades star cluster in nearby Taurus is the bison's head; and Sirius in Canis Major, known as Tayamnisinte, is its tail. Another Lakota myth mentions that the bottom half of Orion, the Constellation of the Hand, represented the arm of a chief that was ripped off by the Thunder People as a punishment from the gods for his selfishness. His daughter offered to marry the person who can retrieve his arm from the sky, so the young warrior Fallen Star (whose father was a star and whose mother was human) returned his arm and married his daughter, symbolizing harmony between the gods and humanity with the help of the younger generation. The index finger is represented by Rigel; the Orion Nebula is the thumb; the Belt of Orion is the wrist; and the star Beta Eridani is the pinky finger. The seven primary stars of Orion make up the Polynesian constellation Heiheionakeiki which represents a child's string figure similar to a cat's cradle. Several precolonial Filipinos referred to the belt region in particular as "balatik" (ballista) as it resembles a trap of the same name which fires arrows by itself and is usually used for catching pigs from the bush. Spanish colonization later led to some ethnic groups referring to Orion's Belt as "Tres Marias" or "Tatlong Maria." In Māori tradition, the star Rigel (known as Puanga or Puaka) is closely connected with the celebration of Matariki. The rising of Matariki (the Pleiades) and Rigel before sunrise in midwinter marks the start of the Māori year. In Javanese culture, the constellation is often called Lintang Waluku or Bintang Bajak, referring to the shape of a paddy field plow. The imagery of the Belt and Sword has found its way into popular Western culture, for example in the form of the shoulder insignia of the 27th Infantry Division of the United States Army during both World Wars, probably owing to a pun on the name of the division's first commander, Major General John F. O'Ryan. The film distribution company Orion Pictures used the constellation as its logo. In artistic renderings, the surrounding constellations are sometimes related to Orion: he is depicted standing next to the river Eridanus with his two hunting dogs Canis Major and Canis Minor, fighting Taurus. He is sometimes depicted hunting Lepus the hare. He sometimes is depicted to have a lion's hide in his hand. There are alternative ways to visualise Orion. From the Southern Hemisphere, Orion is oriented south-upward, and the Belt and Sword are sometimes called the saucepan or pot in Australia and New Zealand. Orion's Belt is called Drie Konings (Three Kings) or the Drie Susters (Three Sisters) by Afrikaans speakers in South Africa and are referred to as les Trois Rois (the Three Kings) in Daudet's Lettres de Mon Moulin (1866). The appellation Driekoningen (the Three Kings) is also often found in 17th and 18th-century Dutch star charts and seaman's guides. The same three stars are known in Spain, Latin America, and the Philippines as "Las Tres Marías" (The Three Marys), and as "Los Tres Reyes Magos" (The Three Wise Men) in Puerto Rico. Even traditional depictions of Orion have varied greatly. Cicero drew Orion in a similar fashion to the modern depiction. The Hunter held an unidentified animal skin aloft in his right hand; his hand was represented by Omicron2 Orionis and the skin was represented by the five stars designated Pi Orionis. Saiph and Rigel represented his left and right knees, while Eta Orionis and Lambda Leporis were his left and right feet, respectively. As in the modern depiction, Mintaka, Alnilam, and Alnitak represented his Belt. His left shoulder was represented by Betelgeuse, and Mu Orionis made up his left arm. Meissa was his head, and Bellatrix his right shoulder. The depiction of Hyginus was similar to that of Cicero, though the two differed in a few important areas. Cicero's animal skin became Hyginus's shield (Omicron and Pi Orionis), and instead of an arm marked out by Mu Orionis, he holds a club (Chi Orionis). His right leg is represented by Theta Orionis and his left leg is represented by Lambda, Mu, and Epsilon Leporis. Further Western European and Arabic depictions have followed these two models. Future Orion is located on the celestial equator, but it will not always be so located due to the effects of precession of the Earth's axis. Orion lies well south of the ecliptic, and it only happens to lie on the celestial equator because the point on the ecliptic that corresponds to the June solstice is close to the border of Gemini and Taurus, to the north of Orion. Precession will eventually carry Orion further south, and by AD 14000, Orion will be far enough south that it will no longer be visible from the latitude of Great Britain. Further in the future, Orion's stars will gradually move away from the constellation due to proper motion. However, Orion's brightest stars all lie at a large distance from Earth on an astronomical scale—much farther away than Sirius, for example. Orion will still be recognizable long after most of the other constellations—composed of relatively nearby stars—have distorted into new configurations, with the exception of a few of its stars eventually exploding as supernovae, for example Betelgeuse, which is predicted to explode sometime in the next million years. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/LSI_Logic] | [TOKENS: 2167] |
Contents LSI Logic LSI Logic Corporation was an American ASIC and EDA company founded in Santa Clara, California. The company designed and sold semiconductors and software that accelerated storage and networking in data centers, mobile networks and client computing. In April 2007, LSI Logic merged with Agere Systems and rebranded the firm as LSI Corporation.On May 6, 2014, LSI Corporation was acquired by Avago Technologies (now known as Broadcom Inc.) for $6.6 billion. History LSI Logic Corporation was incorporated in November 1980 by Wilfred J. Corrigan and began operating in early 1981 using leased facilities in Santa Clara, California. The name "LSI" referred to Large Scale Integration. Corrigan recruited co-founders Bill O'Meara (VP Marketing and Sales), Rob Walker (VP Engineering) and Mitchell "Mick" Bohn (CFO). Initial funding of $6 million came from a consortium of venture capitalists, including Kleiner Perkins Caufield & Byers II, Institutional Venture Partners, and Technical Development Capital Ltd. A second round of $16 million in funding from Sequoia Capital, a group of investment bankers from the UK and First Interstate Bank came In March 1982. That year, LSI Logic had $5 million in sales and a loss of $3.7 million. The initial plan called for a line of CMOS gate arrays created from “masterslices” which were uncommitted transistors customized to a specific application by the deposition of unique metal interconnections. The intention was to have the masterslices manufactured by external semiconductor companies and then do the metallization themselves. In order to jump start the business, they licensed an existing CMOS gate array design from California Devices Inc. (CDI) and reverse engineered and improved on an ECL gate array design from Motorola. The first interactive CAD system was called LSI Design System (LDS). The initial EDA flow was based on simulation from TEGAS and place and route from Silvar-Lisco, integrated on Megatek hardware. What made them unique from other ASIC vendors at the time was that they willing to ship the software to their customers rather than keeping it in-house, which was the strategy used by market leaders at the time. In 1982 they started development of their own in-house CAD tools and moved to Silicon Graphics hardware. By 1988, the EDA industry had developed enough that customers wanted to be able to use 3rd party tools. Sales grew rapidly and they were able to launch a successful initial public offering on the Nasdaq exchange on May, 13 1983. The offering was underwritten by Morgan Stanley & Co and Hambrecht & Quist. 7 million shares of common stock were issued at a price of $21 per share. The stock hit a peak of $25.50 during the day and closed at $24 a share which valued the company at $588M. Once underwriters options were exercised the total offering brought in $153 million. Stock symbol: LLSI. In 1984, LSI Logic formed a Japanese affiliate, Nihon LSI Logic Corporation, and British subsidiary LSI Logic Ltd. In February 1985, a Canadian subsidiary, LSI Logic Corporation of Canada, Inc., was formed. In 1985, the firm entered into a joint venture called Nihon Semiconductor, Inc. together with Kawasaki Steel—Japan's third largest steel manufacturer—to build a $100 million wafer fabrication plant in Tsukuba, Japan. In 1987, LSI Logic was among the 14 founding members of SEMATECH, but later withdrew from the organization in January 1992. In December 1987, LSI Logic licensed from MIPS Computer Systems the rights to manufacture the R2000 and R3000 processors, and the right to implement the MIPS I instruction set architecture (ISA) in their own ASIC designs. In March 1988, LSI Logic agrees to manufacture and sell the SPARC RISC microprocessor under license from SUN Microsystems. In October 1988, LSI Logic acquired a controlling stake in Video Seven Inc., a designer, manufacturer, and marketer of PC graphics boards In April 1989, LSI Logic merged its G-2 Inc PC chipsets and Video Seven Inc. graphics chip buses to create Headland Technology Inc, a subsidiary to be run by LSI Logic founder Bill O'Meara In October 1989, LSI Logic transferred its stock listing from NASDAQ: LLSI to NYSE: LSI. In July 1991, LSI Logic entered into an agreement with Sanyo Electric of Japan to make a set of chips that translate an HDTV signal into a television image. In July 1992, LSI Logic announced CoreWare subsystems as part of its ASIC design flow . In 1993, Sony Computer Entertainment chose LSI Logic as their ASIC partner, charged with fitting the PlayStation CPU on a single chip. LSI's CoreWare could do it, while other offers made to Sony needed two chips. Sony also worked with LSI's engineers develop the graphics engine, DMA controller, I/O and bus controllers. In 1995, LSI Logic acquired all the remaining shares (45%) of its Canadian subsidiary LSI Logic Corporation of Canada, Inc., which it did not already own. In 1997, LSI Logic acquired Mint Technology, an engineering services company. In August 1998, LSI Logic acquired Symbios Logic from Hyundai Electronic for $760 million cash. In February 1999, LSI Logic acquired Seeq Technology for $106 million in stock, adding physical-layer based Ethernet technology to LSI's product line. In January 2000, LSI Logic established a $50M venture fund to invest in startups in the communication sector. In May 2000, LSI Logic acquired IntraServer for $70 million, with expectations to add their rapidly expanding customer base to LSI's own. In November 2000, LSI Logic acquired Syntax Systems, and in August 2001 the groups merged to become LSI Logic Storage Systems, and later Engenio Information Technologies. In March 2001 LSI Logic acquired C-Cube Microsystems, a video compression semiconductor company, for $878 million in stock. In September 2001 LSI Logic acquired the RAID adapter division from American Megatrends in a $221 million cash transaction. Included in this deal, LSI received AMI's MegaRAID software intellectual property, host bus adapter products and 200 RAID employees. In January 2002 LSI Logic and Storage Technology Corporation (StorageTek) entered an alliance making StorageTek the distributor of their co-branded storage products. In August 2002 LSI Logic acquired Mylex from IBM, to expand its storage technologies. In November 2003, LSI Logic sold its Tsukuba, Japan wafer fabrication facility to ROHM Company, Ltd. for $23.5 million. The Engenio division of LSI Logic filed for its own IPO in 2004, but withdrew citing adverse market conditions after the burst of the dot-com bubble. In May 2005, Abhi Talwalkar joined LSI Logic as president and CEO, and was also appointed to the board of directors. Talwalkar was an executive at Intel Corporation before joining LSI. Wilfred Corrigan served as Chief Executive Officer and Chairman of the Board from 1981 to June 2005 and Chairman from June 2005 until May 2006. In April 2006, LSI Logic sold the Gresham, Oregon design and manufacturing facility to ON Semiconductor for $105 million in cash In October 2006, LSI Logic agreed to an all-stock merger with Agere Systems worth about $4 billion. In March 2007, LSI Logic acquired SiliconStor Inc., a provider of semiconductor solutions for enterprise storage networks, for approximately $55 million in cash. In April 2007, LSI Logic completed its merger with Agere Systems Inc., who previously owned LSI's Mobility Products Group, and rebranded the firm LSI Corporation. In July 2007, Magnum Semiconductor Inc. a spin-off of Cirrus Logic Inc., acquired LSI Corporation's consumer products business and 13 percent of LSI's workforce. These lines included architectures named DoMiNo and Zevio, evolutions of the C-Cube Microsystems technology. In August 2007, LSI Corporation signed an agreement with STATS ChipPAC Ltd to sell its Pathumthani, Thailand semiconductor assembly and test operations for $100 million. In October 2007, LSI Corporation acquired Tarari, a maker of silicon and software, for $85 million in cash. That month, LSI Corporation completed its sale of its Mobility Division to Infineon Technologies AG (Munich) for €330 million in cash. Approximately 700 LSI employees transferred to Infineon in the deal. In April 2009, LSI Corporation bought the 3ware RAID adapter business of Applied Micro Circuits Corporation. In July 2009, LSI Corporation acquires NAS vendor ONStor, Inc. for $25 million. In March 2011, LSI Corporation announced its sale of its Engenio external storage systems business to NetApp for $480 million in cash. The sale of the Engenio division, which generated revenues of $705 million in 2010, completed in May. In January 2012, LSI Corporation completed the acquisition of SandForce, which produced flash memory controllers (for $370 million reported in October 2011). LSI started producing its own PCIe cards for data center servers, using SandForce's flash controller chips, under their new Nytro product line that April. This included three different products: LSI Nytro WarpDrive Application Acceleration Cards, LSI Nytro XD Application Acceleration Storage Solution, and LSI Nytro MegaRAID Application Acceleration Cards. In December 2012, LSI Corporation transferred its stock listing from NYSE: LSI to NASDAQ (Global Select Market): LSI. On December 16, 2013, Avago Technologies (which later acquired Broadcom Corporation, then renamed itself as Broadcom Ltd., then in 2018 changed its name to Broadcom Inc.) announced it would be acquiring LSI Corporation for $6.6 billion in cash. The transaction closed on May 6, 2014. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Kimi_(chatbot)] | [TOKENS: 860] |
Contents Kimi (chatbot) Kimi is an artificial intelligence (AI) chatbot and series of large language models developed by Chinese company Moonshot AI. Its first version, released in 2023, was known for supporting up to 128,000 tokens of context. Kimi K2, an open-weight model released in July 2025, showed strong performances on coding benchmarks. History Moonshot AI was founded in March 2023 in China. In October 2023, the company officially released the Kimi chatbot and began closed-beta testing. On 16 November 2023, Kimi was released to the general public based on the Moonshot model. The first version of Kimi supported lossless context of 128,000 tokens, making it the first AI model that was capable of accepting contexts of this size. In March 2024, Moonshot AI began closed beta testing of an updated version of Kimi with a 2 million character context window. In July 2024, Kimi's "context caching" feature entered public beta. On 11 October 2024, Kimi Explore Edition, featuring AI-powered autonomous search, went live globally; monthly active users have since exceeded 36 million. In November 2024, Kimi began internal testing of an AI video generation model. On 20 January 2025, Kimi K1.5 was released. Moonshot AI claimed it matched the performance of OpenAI o1 in mathematics, coding, and multimodal reasoning capabilities. In April 2025, Kimi-VL, an open source 16 billion parameter mixture of experts (MoE) large language model with 3 billion active parameters, was released. In June, a reasoning model named Kimi-VL-Thinking was also released. In June 2025, Kimi-Dev, a 72B parameter coding-focused model based on Qwen2.5-72B, was released. It achieved state of the art performance among open source models on the SWE-bench Verified benchmark. Also in June, Moonshot AI released Kimi-Researcher, an autonomous AI research agent available through Kimi's website and app. In July 2025, Moonshot AI released Kimi K2, a 1 trillion parameter mixture of experts large language model with 32 billion active parameters which was open sourced under a modified MIT license. It achieved state of the art performance in coding benchmarks while still offering good performance in other benchmarks. On 9 September 2025, Moonshot AI released an updated version of K2, Kimi-K2-Instruct-0905, which improved its performance in coding tasks and increased its context window from 128K tokens to 256K tokens. In September 2025, Moonshot AI added an agentic AI feature to Kimi known as "OK Computer" (likely named after the Radiohead album of the same name). It is capable of creating multi-page websites and editable slides from simple user prompts and can process up to 1 million rows of input data at once, and output text, audio, images, and video. In October 2025, Moonshot AI released Kimi Linear, a 48 billion parameter MoE model with 3 billion active parameters. It uses a more efficient attention method known as Kimi Delta Attention (KDA), which reduces memory usage and improves generation speed at longer context window sizes. In January 2026, Moonshot AI released Kimi K2.5, a 1 trillion parameter MoE model with 32 billion active parameters. The model is multimodal in vision and language understanding with advanced agentic capabilities, instant and thinking modes, as well as conversational and agentic paradigms. Model versions Pricing The Kimi apps are free to use with general rate limits. However, there are three subscription plans known as "Moderato", "Allegretto", and "Vivace" (all named after tempo markings). The plans offer higher usage of the K2 model, access to K2 Turbo, a version of the model that runs on faster hardware, extended access to Kimi Researcher and OK Computer, and faster Kimi slides generation. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Operator_overloading] | [TOKENS: 1436] |
Contents Operator overloading In computer programming, operator overloading, sometimes termed operator ad hoc polymorphism, is a specific case of polymorphism, where different operators have different implementations depending on their arguments. Operator overloading is generally defined by a programming language, a programmer, or both. Rationale Operator overloading is syntactic sugar, and is used because it allows programming using notation nearer to the target domain and allows user-defined types a similar level of syntactic support as types built into a language. It is common, for example, in scientific computing, where it allows computing representations of mathematical objects to be manipulated with the same syntax as on paper. Operator overloading does not change the expressive power of a language (with functions), as it can be emulated using function calls. For example, consider variables a, b and c of some user-defined type, such as matrices: a + b * c In a language that supports operator overloading, and with the usual assumption that the * operator has higher precedence than the + operator, this is a concise way of writing: Add(a, Multiply(b, c)) However, the former syntax reflects common mathematical usage. Examples In this case, the addition operator is overloaded to allow addition on a user-defined type Time in C++: Addition is a binary operation, which means it has two operands. In C++, the arguments being passed are the operands, and the temp object is the returned value. The operation could also be defined as a class method, replacing lhs by the hidden this argument; However, this forces the left operand to be of type Time: Note that a unary operator defined as a class method would receive no apparent argument (it only works from this): The less-than (<) operator is often overloaded to sort a structure or class: Like with the previous examples, in the last example operator overloading is done within the class. In C++, after overloading the less-than operator (operator<), standard sorting functions can be used to sort some classes. Starting in C++20 with the introduction of the three-way comparison operator (operator<=>), all the order operators can be defined by just defining that operator. The three-way comparison operator exists in many languages, including C++, Python, Rust, Swift, and PHP. Other languages, such as Java and C# instead use a method Comparable.compareTo(). Criticisms Operator overloading has often been criticized[weasel words] because it allows programmers to reassign the semantics of operators depending on the types of their operands. For example, the use of the << operator in C++ a << b shifts the bits in the variable a left by b bits if a and b are of an integer type, but if a is an output stream then the above code will attempt to write a b to the stream. Because operator overloading allows the original programmer to change the usual semantics of an operator and to catch any subsequent programmers by surprise, it is considered good practice to use operator overloading with care (the creators of Java decided not to use this feature, although not necessarily for this reason[original research?]). Another, more subtle, issue with operators is that certain rules from mathematics can be wrongly expected or unintentionally assumed. For example, the commutativity of + (i.e. that a + b == b + a) does not always apply; an example of this occurs when the operands are strings, since + is commonly overloaded to perform a concatenation of strings (i.e. "bird" + "song" yields "birdsong", while "song" + "bird" yields "songbird"). A typical counter[citation needed] to this argument comes directly from mathematics: While + is commutative on integers (and more generally any complex number), it is not commutative for other "types" of variables. In practice, + is not even always associative, for example with floating-point values due to rounding errors. Another example: In mathematics, multiplication is commutative for real and complex numbers but not commutative in matrix multiplication. Catalog A classification of some common programming languages is made according to whether their operators are overloadable by the programmer and whether the operators are limited to a predefined set. Timeline of operator overloading The ALGOL 68 specification allowed operator overloading. Extract from the ALGOL 68 language specification (page 177) where the overloaded operators ¬, =, ≠, and abs are defined: Note that no special declaration is needed to overload an operator, and the programmer is free to create new operators. For dyadic operators their priority compared to other operators can be set: Ada supports overloading of operators from its inception, with the publication of the Ada 83 language standard. However, the language designers chose to preclude the definition of new operators. Only extant operators in the language may be overloaded, by defining new functions with identifiers such as "+", "*", "&" etc. Subsequent revisions of the language (in 1995 and 2005) maintain the restriction to overloading of extant operators. In C++, operator overloading is more refined than in ALGOL 68. Java language designers at Sun Microsystems chose to omit overloading. When asked about operator overloading, Brian Goetz of Oracle responded "Value types first, then we can talk about it.", suggesting that it could potentially be added after Project Valhalla. Python allows operator overloading through the implementation of methods with special names. For example, the addition (+) operator can be overloaded by implementing the method obj.__add__(self, other). Ruby allows operator overloading as syntactic sugar for simple method calls. Lua allows operator overloading as syntactic sugar for method calls with the added feature that if the first operand doesn't define that operator, the method for the second operand will be used. Microsoft added operator overloading to C# in 2001 and to Visual Basic .NET in 2003. C# operator overloading is very similar in syntax to C++ operator overloading: Scala treats all operators as methods and thus allows operator overloading by proxy. In Raku, the definition of all operators is delegated to lexical functions, and so, using function definitions, operators can be overloaded or new operators added. For example, the function defined in the Rakudo source for incrementing a Date object with "+" is: Since "multi" was used, the function gets added to the list of multidispatch candidates, and "+" is only overloaded for the case where the type constraints in the function signature are met. While the capacity for overloading includes +, *, >=, the postfix and term i, and so on, it also allows for overloading various brace operators: [x, y], x[y], x{y}, and x(y). Kotlin has supported operator overloading since its creation by overwriting specially named functions (like plus(), inc(), rangeTo(), etc.) Because both Kotlin and Java compile to .class, when converted back to Java this will just be represented as: Operator overloading in Rust is accomplished by implementing the traits in std::ops. See also References |
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[SOURCE: https://en.wikipedia.org/wiki/Picolisp] | [TOKENS: 703] |
Contents PicoLisp PicoLisp is a programming language, a dialect of the language Lisp. It runs on operating systems including Linux and others that are Portable Operating System Interface (POSIX) compliant. Its most prominent features are simplicity and minimalism. It is built on one internal data type: a cell. On the language level, a programmer can use three different data types (numbers, symbols, and lists) being represented by cells and differentiated by bits at the end of the cell. It is free and open-source software released under an MIT License (X11). Features Functions can accept arbitrary types and numbers of arguments. Macros are needed only in rare cases and are implemented using the quote function. PicoLisp does not include Lisp's lambda function. This is because the quote function is changed to return all its arguments unevaluated, not only the car of the first. A special feature is the intrinsic create, read, update, and delete (CRUD) functioning. Persistent symbols are first-class citizens (objects), they are loaded from database files automatically when accessed, and written back when modified. Applications are written using a class hierarchy of entities and relations. Other features include: Prolog engine, database engine and database queries, distributed databases, inlining of C language functions and native C function calls, child process management, interprocess communication, browser graphical user interface (GUI), and internationalization and localization. History The design of PicoLisp is most similar to the first version of MacLisp, Interlisp and mainly Portable Standard Lisp. It was ported to DOS and SCO Unix. Since 1993, it was used mainly on Linux. In the mid-1990s, database functions were added.[citation needed] The first versions were written in a mix of C and assembly language. In 1999, a first rewrite from scratch was done, fully in C. In 2002, that version was released under a GNU General Public License (GNU GPL). In 2010, it changed to an MIT/X11 license. In 2009, the 64-bit version was released, another rewrite, this time written in generic assembly, which in turn is implemented in PicoLisp. This version adds support for coroutines. In December 2010, a Java version named Ersatz PicoLisp was released. In September 2014, Burger announced the PilMCU project on the PicoLisp development listserv, an effort with George Orais to implement PicoLisp in hardware directly. In July 2015, Burger announced PilOS - The PicoLisp Operating System, a minimal prototype based on the modification of PilMCU targeting embedded applications. It runs on standard x86-64 PC hardware, directly off the BIOS and includes all the features of 64-bit PicoLisp (minus native function calls, due to the fact there is no other native environment such as the C standard library); in principle, it works as its own operating system. In the summer of 2016, development of PilBox ("PicoLisp Box") – a generic Android app allowing to write apps in pure PicoLisp – was started. It is still being developed and maintained. In 2021, PicoLisp was re-implemented in LLVM and released as pil21. The source language which is compiled to LLVM-IR is also in PicoLisp syntax. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Baobhan_sith] | [TOKENS: 475] |
Contents Baobh-shìth The baobh-shìth (Scottish Gaelic pronunciation: [ˈpɤːv ˈhiː], literally "fairy witch" or "fairy hag" in Scottish Gaelic, plural baobhan-sìth Scottish Gaelic pronunciation: [ˈpɤːvan ˈʃiː]) is a female fairy in the folklore of the Scottish Highlands, though they also share certain characteristics in common with the succubus. They appear as beautiful women who seduce their victims before attacking them and killing them. Folklore There are numerous stories about the baobhan-sìth with a general theme of hunters being attacked in the wilderness at night. In the tale recorded by Mackenzie, there were four men who went hunting and took shelter for the night in a lonely shieling or hut. One of the men supplied vocal music while the others began dancing. The men expressed a desire for partners to dance with, and soon after that four women entered the hut. Katharine Briggs suggested that the baobhan-sìth was unable to catch the fourth man among the horses because of the iron with which the horses were shod, iron being a traditional fairy vulnerability. In a similar tale one of the men noticed that the women had deer hooves instead of feet and fled from them. He returned the next morning to find that the other hunters had their "throats cut and chests laid open". In a third story the hunters took refuge in a cave. Each of the men said he wished his own sweetheart were there that night, but one of them, named Macphee, who was accompanied by his black dog, said he preferred his wife to remain at home. At that moment a group of young women entered the cave, and the men who had wished for their sweethearts were killed. Macphee was protected by his dog who drove the women from the cave. One recurring motif in these stories is that the baobhan-sìth appear almost immediately after the hunters express their desire for female companionship. This is connected with a traditional Scottish belief that if one were to make a wish at night without also invoking God's protection, then that wish would be granted in some terrible manner. In popular culture See also References |
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[SOURCE: https://en.wikipedia.org/wiki/Hulu] | [TOKENS: 7893] |
Contents Hulu Hulu (/ˈhuːluː/, HOO-loo) is an over-the-top content brand and American subscription streaming media service owned by Disney Streaming, a subsidiary of the Disney Entertainment segment of the Walt Disney Company. It is one of the most-subscribed video on demand streaming media services, with 64.1 million paid memberships. Its headquarters are located in Los Angeles, California, with offices in Santa Monica, California (the former West Coast bureau for HBO), New York City, and Seattle, Washington. Hulu was launched on October 29, 2007, initially as a joint venture between News Corporation and NBC Universal; Providence Equity, Disney, and Time Warner later made investments in the service. Hulu originally served as an aggregator, streaming recent episodes of programs from the companies' television networks (including ABC, NBC, and Fox). In 2010, Hulu launched a subscription service, initially branded as "Hulu Plus," which featured full seasons of programs from the companies and other partners, and access to new episodes immediately after their airing. In 2016, Hulu syndicated its free library to Yahoo in order to focus exclusively on Hulu Plus. In 2017, the company launched "Hulu + Live TV"—a superset of Hulu Plus also offering access to broadcast and cable television channels. In 2019, Disney acquired a majority stake in Hulu as part of its acquisition of News Corporation successor 21st Century Fox, and subsequently acquired the remaining stakes held by AT&T and Comcast in 2019 and 2023, respectively, giving it full ownership. Following the acquisition, Disney began to establish synergies between Hulu and its sister service Disney+, including integrating a Hulu content hub into the Disney+ library for users subscribed to both services. In 2025, Disney announced plans to eventually discontinue Hulu's existing apps in favor of a shared platform with Disney+, although they will remain separate subscriptions. Aside from a Japanese version of the service launched in 2011 (which would be acquired by Nippon Television in 2014), Hulu did not pursue a wider international expansion until 2025, when Disney announced that Hulu would replace its Star brand for general entertainment content on Disney+ outside of the United States. In January 2025, Disney announced its intent to acquire a 70% majority stake in competing streaming television service FuboTV. The sale is expected to be completed by late-2025 or early-2026; the merged business will consist of the FuboTV and the Hulu + Live TV businesses, and will remain led by Fubo CEO David Gandler. Etymology The name Hulu comes from two Mandarin Chinese phrases, húlu (葫芦; 葫蘆; "calabash, bottle gourd") and hùlù (互录; 互錄; "interactive recording"). Jason Kilar, who served as CEO of Hulu, said the name comes from a Chinese proverb: Hulu is Mandarin for gourd. And so when we were launching Hulu, we thought, "what a great name that is." And it had this great sort of symbolism of the holder of precious things, which is the holder of premium content. So that's why we named it Hulu. History Individuals who were instrumental[vague] in the founding of Hulu include Bruce Campbell, Peter Chernin, JB Perrette, Mike Lang, Beth Comstock, George Kliavkoff, Darren Feher, and Jason Kilar. Rus Yusupov, the lead designer on Hulu's original design team, played a key role in shaping the platform's initial interface and user experience. Hulu was announced in March 2007 with AOL, NBC Universal (then co-owned by General Electric and Vivendi), MSN, Myspace (then owned by News Corporation), and Yahoo! planned as "initial distribution partners." Jason Kilar was named Hulu CEO in late 2007. NBC shut down its earlier online video effort NBBC in order to focus on Hulu. The name Hulu was chosen in late August 2007, when the website went live with an announcement only and no content. It invited users to leave their email addresses for the upcoming beta test. In October 2007, Hulu began the private beta testing by invitation, and later allowed users to invite friends. Hulu launched for public access in the United States on March 12, 2008. Hulu began an advertising campaign during NBC's broadcast of Super Bowl XLIII with an initial ad starring Alec Baldwin titled "Alec in Huluwood." Advertisements have since aired featuring Eliza Dushku, Seth MacFarlane, Denis Leary, and Will Arnett.[citation needed] In July 2007, Providence Equity, the owner of Newport Television, became one of the earliest "outside" investors by purchasing a 10% stake in the company for US$100 million equity investment, before the company was known as "Hulu." With its investment came a seat on the board of directors, where Providence was said to act as an "independent voice on the board." In April 2009, the Walt Disney Company joined the Hulu consortium as a stakeholder, with plans to offer content from ABC, ESPN and Disney Channel. Early in 2010, Hulu chief executive Jason Kilar said the service had made a profit in two quarters and that the company could top $100 million in revenue by summer 2010, more than its income for all of 2009. ComScore says monthly video streams reached 903 million in January 2010, over three times the figure for a year earlier, and second only to YouTube. On August 16, 2010, a report revealed that Hulu was planning an initial public offering (IPO) which could value the company at more than $2 billion. In June 2011, an "unsolicited offer" caused Hulu to begin "weighing whether to sell itself". However, Hulu and its owners refused to sell the company, as none of the bidders offered an amount that was satisfactory to its owners. In September of that year, the service launched in Japan; marking Hulu's first and only international expansion. Hulu generated $420 million in revenue in 2011, $80 million short of the company's target. The vacant CEO post was officially filled by former Fox Networks President Mike Hopkins on October 17, 2013. In October 2012, Providence sold its 10% stake to "Hulu's media owners" and ceased participation in the board. On February 27, 2014, Nippon Television Network Corporation acquired Hulu's Japanese business. The service would retain the "Hulu" brand and technology in Japan under a subsidiary of Nippon as part of a separate agreement. On August 3, 2016, Time Warner acquired a 10% stake of Hulu. Hopkins exited and was named Sony Pictures TV Chairman. Fox Networks Group COO Randy Freer was named CEO on October 24, 2017. On March 20, 2019, Disney acquired 21st Century Fox, giving it a 60% majority stake in Hulu. On April 15, 2019, AT&T sold its 10% stake in Hulu back to the company for $1.43 billion, leaving Disney with 67% and Comcast with 33%. Comcast, the only other shareholder, announced on May 14, 2019, that it had agreed to cede its control to Disney, and reached an agreement for Disney to purchase its 33% stake in Hulu as early as 2024. On May 14, 2019, Comcast relinquished its control in Hulu to Disney effective immediately. As a result, the streaming service became a division of Walt Disney Direct-to-Consumer & International (DTCI) with Comcast effectively becoming a silent partner. Under the agreement, Comcast's 33% stake could be sold to Disney at fair market value as early as 2024. The fair market value would be determined at that time, but Disney guaranteed a minimum valuation of the entire company at $27.5 billion (valuing the Comcast stake as worth at least $9.075 billion). Randy Freer would report to Disney executive Kevin Mayer. Disney stated that its control of Hulu was the third major component of its direct-to-consumer strategy, complementing its sports streaming service ESPN+, and its then-forthcoming Disney+. Hulu would be oriented towards "general" entertainment and content targeting mature audiences. NBCUniversal would continue to license its content to the service through at least 2024, but had the option to begin transitioning its exclusivity deals with Hulu to non-exclusive terms beginning in 2020, and to end other content deals beginning in 2022. On July 31, 2019, Disney reorganized Hulu's reporting structure, placing Hulu's Scripted Originals team under Disney General Entertainment Content. Under the new structure, Hulu's SVP of Original Scripted Content would report directly to the chairman of Disney Television Studios and ABC Entertainment. As of November 2019, FX and Fox Searchlight were assigned to supply Hulu with content. In January 2020, Disney eliminated the role of Hulu CEO, with its top executives to report directly to DTCI and Walt Disney Television. On January 31, 2020, Freer resigned as CEO of Hulu and the position was eliminated; Hulu's top executives now report directly to DTCI and Walt Disney Television. In June 2021, Comcast accused Disney of undermining Hulu's growth and value by not engaging in international expansion of the service, having instead added the Star brand as an extension of Disney+ in selected markets. On September 7, 2021, Hulu announced that the prices of its main video on-demand and ad-free plans would increase by $1 each to $6.99 and $12.99 per-month beginning October 8. In October 2021, Hulu president Kelly Campbell resigned, and was subsequently appointed the president of NBCUniversal's competing service Peacock. On November 22, 2021, Disney and WarnerMedia reached a deal to let select 20th Century Studios and Searchlight Pictures films stream on Disney+, Hulu and HBO Max in 2022. In March 2022, NBCUniversal decided that it would pull content from Hulu and move it to Peacock, beginning in September. In January 2022, Joe Earley became president of Hulu. In September 2022, Chapek indicated that Disney was considering merging Hulu into Disney+ because the model had been successful outside the United States without any content friction. To accelerate the plan, he said that Disney would love to buy out Comcast's 33.3% stake in Hulu earlier than their previously agreed 2024 timeline. However, Comcast had not offered reasonable terms for an early buyout and had instead expressed interest in buying Hulu themselves if it were for sale. On May 18, 2023, it was announced that Disney+ and Hulu would remove nearly 60 original films and series on May 26 in order to "cut costs." The news sparked some backlash, mostly towards the initial decision to remove Howard, the documentary on the life of lyricist Howard Ashman, on the eve of Pride Month and the release of the live-action adaptation of The Little Mermaid. However, it was confirmed the next day that film will remain available on the service. On July 10, 2023, Hulu launched an adult animation and anime hub known as Animayhem, featuring several different 20th Television Animation programs, including American Dad, Bob's Burgers, Family Guy, The Cleveland Show, and King of the Hill, among various others. Additionally, new seasons of Futurama and King of the Hill were commissioned for the service, while the company also showcased an "immersive" experience at San Diego Comic-Con to promote the occasion, titled Hulu Animayhem: Into the Second Dimension. The hub was also launched on Disney+ internationally the following year. On September 6, 2023, Comcast CEO Brian L. Roberts announced that Hulu's equity fair value would be assessed as of September 30. In November 2023, Disney began their acquisition of Comcast's stake in Hulu. The two companies previously agreed to a minimum floor price of $8.6 billion, which was paid for on December 1. As of August 2024, Disney and Comcast remained in a dispute over Hulu's valuation in connection with fully completing the transaction, with an arbitration decision expected in 2025. On June 9, 2025, both parties resolved the dispute, with Disney paying Comcast an extra $438.7 million in addition to the minimum floor price for their remaining stake of Hulu, closing on or before July 24, 2025. On December 6, 2023, Disney began to roll out an integration of Hulu as a content hub on the Disney+ platform for subscribers to both services. On August 6, 2025, Disney announced that it would discontinue the standalone Hulu apps and completely merge the service into the Disney+ platform. Hulu will still remain available as a standalone subscription, but its content will be accessed from a new "unified" app to be released in 2026. In addition, Disney replaced the Star brand on Disney+ in international markets with Hulu on October 8, 2025. On September 30, 2025, stockholders of FuboTV approved a planned merger of the company with Hulu + Live TV to form a larger company that will be controlled by Disney. The Fubo deal calls for Fubo to merge with Hulu + Live TV, a sister platform to the Hulu streaming app, with Disney owning approximately 70% of the newly expanded entity. Fubo’s existing management team, led by co-founder and CEO David Gandler will run the new Fubo. Fubo and Hulu + Live TV will continue to be available to consumers as separate offerings post-close. Fubo has said it expects the deal to close in the fourth quarter of 2025 or the first quarter of 2026. On October 29, 2025, Disney completed its acquisition of a majority stake in Fubo, which made it the No. 6 pay-television operator in the United States when combined with Hulu + Live TV. Disney will control 70% of the new streaming organization, with Fubo shareholders retaining the rest. Fubo’s current management team, led by co-founder and CEO David Gandler, will run the merged Fubo and Hulu + Live TV businesses. On January 7, 2026, Disney revealed plans to shut down the standalone Hulu app for the Nintendo Switch on February 5, 2026 to unify the service with Disney+ into a single app. Content From January 17, 2011, to April 24, 2014, Hulu streamed its own in-house web series The Morning After, a light-hearted pop-culture news show. It was produced by Hulu in conjunction with Jace Hall's HDFilms and stars Brian Kimmet and Ginger Gonzaga. Producing the show was a first for the company, which in the past has been primarily a content distributor. On January 16, 2012, Hulu announced that it would be airing its first original script based program, titled Battleground, which premiered in February 2012. The program aired on Hulu's free web service rather than on the subscription-based Hulu Plus. Battleground is described as a documentary-style political drama. Later that same month, Hulu announced it would air The Fashion Fund, a six-part reality series, and the winner of the show would receive $300,000 to start their career. To continue with its original programming movement, Hulu announced that there would be a total of seven original programs that were planned to air on its service: Battleground, Day in the Life, and Up to Speed were previously mentioned; and on April 19, Hulu added four more shows to its list: Don't Quit Your Daydream, Flow, The Awesomes, and We Got Next. Some of these programs began airing in 2012, while others premiered over the next few years. On May 21, 2012, Hulu announced it would be bringing Kevin Smith to its lineup of original programming. Smith hosts a movie discussion show titled Spoilers, which began airing in mid-2012. In March 2016, Lionsgate Premiere and Hulu jointly acquired distribution rights to the film Joshy, which was later released on August 12, 2016. On May 4, 2016, Hulu acquired The Beatles: Eight Days a Week, as its first documentary acquisition, as part of a planned Hulu Documentary Films collection. The film premiered theatrically on September 15, before debuting on the streaming service on September 17. On March 3, 2025, Hulu streamed the 97th Academy Awards in simulcast with ABC, making the first time that the Oscars were streamed on the platform. However, the airing was plagued with multiple technical problems. These included some server outages in the beginning of the award ceremony, as well as the live event ending just before the Best Actress nominees were announced. Following the start of its service, Hulu signed deals with several new content providers making additional material available to consumers. At launch, Hulu streamed movies and shows from co-owners News Corporation and NBCUniversal, as well as from Sony Pictures, MGM, Warner Bros., and Lionsgate. On April 30, 2009, the Walt Disney Company announced that it would join the venture, purchasing a 27% stake in Hulu. On June 1, 2011, Hulu announced a deal to add hundreds of films from Miramax to the service. Starting August 15, 2011, viewers of content from Fox and related networks are required to authenticate paid cable or satellite service wherever Fox streams episodes, including on Hulu, to be able to watch them the morning after the first airing. Non-subscribers will see those episodes delayed a week before they are viewable. On October 28, 2011, Hulu announced that they had signed a five-year deal with The CW, giving the streaming site access to next-day content from five of the six major networks. On September 18, 2013, Hulu announced a multi-year deal with the BBC that would deliver 2,000 episodes from 144 different titles in the first 12 months.[citation needed] In 2015, Hulu began offering content from Showtime for an additional $8.99/month, which is cheaper than Showtime's own streaming service. On June 16, 2016, Hulu announced a deal with the Disney-ABC Television Group for the exclusive SVOD rights to past seasons of seven Disney Channel, Disney Junior and Disney XD series, and more than 20 Disney Channel original movies. The CW's agreement with Hulu ended September 18, 2016; in-season streaming of current CW programs moved to the network's own digital platforms, and Netflix began to carry past seasons of The CW's programs through 2019. As of January 2017[update], a limited amount of content from CBS's library is available on-demand, mostly limited to shows that are no longer producing new episodes. A deal was reached to bring live broadcasts of CBS and several affiliated channels to Hulu's upcoming live streaming service as well as to make more shows available on-demand. In April 2018, Hulu announced a partnership with Spotify that allows users to purchase both streaming services for a discounted price per month. This discount also includes an even larger discounted rate for university students. Hulu distributes video on its own website and syndicates its hosting to other sites, and allows users to embed Hulu clips on their websites. In addition to NBC, ABC and Fox programs and movies, Hulu carries shows from networks: A&E, Big Ten Network, Bravo, E!, Fox Sports 2, FX, PBS, NFL Network, Oxygen, RT America, Fox Sports 1, Sundance TV, Syfy, USA Network, NBCSN, and online comedy sources such as Onion News Network. Hulu retains between thirty and fifty percent of advertising revenue generated by the shows it distributes. In November 2009, Hulu also began to establish partnerships with record labels to host music videos and concert performances on the site, including EMI in November 2009, and Warner Music Group in December 2009. In early March 2010, Viacom announced that it was pulling two of the website's most popular shows, The Colbert Report and The Daily Show, off Hulu. The programs had been airing on Hulu since late 2008. A spokesman for Viacom noted that "in the current economic model, there is not that much in it for us to continue at this time. If they can get to the point where the monetization model is better, then we may go back." In February 2011, both shows were made available for streaming on Hulu again. The Daily Show was again removed from Hulu in March 2017 in order to push viewers to watch the program on Viacom and Comedy Central's apps. In 2012, Viz Media, Aniplex of America, and other distributors teamed up to create Neon Alley. It had launched on October 2, 2012, as a 24/7 web channel, but in 2014 it had switched to Hulu-only. The site contained exclusive dub premieres with anime such as Accel World, Blue Exorcist, Magi: The Labyrinth of Magic, Fate/Zero and the uncut version of Sailor Moon. It also had shows such as Naruto and Naruto: Shippuden, Death Note, Inuyasha, Bakuman, Ranma ½, One Piece, One-Punch Man, and Bleach. It went defunct on May 4, 2016. However, Hulu still hosts over 300 anime from Funimation, Aniplex of America, Viz Media, and Sentai Filmworks, and selected anime began resume to release on Hulu following the deal between Disney and Sony Pictures since 2021. In April 2017, Hulu signed a first-run license deal with Annapurna Pictures. Hulu also has output deals with IFC Films and Magnolia Pictures. Hulu in May 2018 announced its first-ever license deal with DreamWorks Animation, becoming the exclusive streaming home for future DWA movies feature films, as well as library films. DWA had streamed exclusively through Netflix since 2013. Films will be available on the service in 2019, while original series will be available later in 2020.[citation needed] In October 2018, PocketWatch launched 90 22-minute episodes of repackaged content from their YouTube creator partners on Hulu and Amazon Prime Video and partnered with Paramount Pictures to license them to international distributors. On December 4, 2018, Hulu confirmed an exclusive multi-year first-look SVOD deal with Funimation, and the deal was later folded into Disney-Sony deal on April 21, 2021. In June 2019, Hulu and FX signed an output deal with Lionsgate, where Hulu and FX would respectably gain the streaming and television rights to films released under the Lionsgate label in 2020 and 2021. In August 2019, Hulu agreed to control the streaming rights films released by Bleecker Street. On March 2, 2020, Hulu launched a dedicated "hub" for content from FX branded as "FX on Hulu", with the service becoming the exclusive streaming outlet for current and past series from the network. Beginning with Breeders, new episodes of FX original series also become available on Hulu immediately after their television airing, and selected series will also premiere exclusively on the service. On January 14, 2021, it was announced that following an exclusive 3-week IMAX engagement, Searchlight's Nomadland would be released on Hulu alongside a regular limited theatrical and drive-in run in the United States on February 19. On April 21, 2021, Disney reached a deal for television and streaming rights to Sony Pictures films from 2022 through 2026, which includes library rights for some of its franchises like Spider-Man, Jumanji and Hotel Transylvania franchises, etc., and licensing anime under Funimation and Crunchyroll brands and anime released by Aniplex of America, and post-pay-one window rights to new releases (after their exclusivity period with Netflix expires). This deal covers Disney+, Hulu, and Disney's television channels. On May 17, 2021, it started Onyx Collective which is a content brand for creators. On August 31, 2021, Disney announced that it would fold the American version of Hotstar—a niche streaming service targeting Indian Americans—In late 2022, with its original entertainment content migrating to Hulu. In October 2025, Hulu acquired the rights to the Spanish thriller Innate, originally developed by Netflix Spain. In early 2024, Hulu faced criticism for airing AI-generated advertisements which were seen as promoting a pro-Israel narrative. One such advertisement depicted Gaza as a tourist destination rather than acknowledging its complex geopolitical context. An article by Vice highlighted that many viewers found these advertisements controversial due to perceived factual inaccuracies and insensitivity to the ongoing conflict. This led to calls for boycotting Hulu and its parent company, Disney, which holds a majority stake in Hulu and the major online advertising provider of Disney's online platforms, including Disney+. First and third-party content providers for Hulu. Asterisk (*) denotes third parties, while several international providers secure content deals through Disney+. By early 2026, the traditional "next-day" streaming model on Hulu transitioned following the full integration of Hulu into Disney+. Next-day access is now primarily restricted to Disney-owned properties and third parties with active output deals: Services Hulu's subscription service was launched in a software release life cycle on June 29, 2010, and officially launched on November 17, 2010, under the branding Hulu Plus. The service remained advertising-supported, but it offers an expanded content library including full seasons, day-after access to current season content and more episodes of shows available. Hulu also launched Hulu Plus apps on other types of devices, including mobile, digital media players, and video game consoles. By the end of 2011, Hulu Plus had around 1.5 million subscribers. On April 29, 2015, it was announced that the "Hulu Plus" branding would be discontinued, and that the service would be henceforth marketed as simply "Hulu" to place it in-line with its subscription-only competitors. By then, the service had grown to 9 million subscribers. In July 2015, Hulu was exploring an advertising-free subscription option for around $12 to $14 a month. This was confirmed as going forward as of September 2, 2015[update], with a "No Commercials" plan priced at $11.99, $4 more than the $7.99 monthly rate for a "Limited Commercials" subscription, though a few highlighted network series (fewer than 10) would retain pre-roll and post-roll[clarification needed] ad pods. Starting in 2019, Hulu plans to begin displaying on-screen ads when the viewer pauses the show, although it is unclear whether this will apply to customers on the $11.99/month No Ads plan. In May 2016, Hulu announced that it had reached 12 million subscribers. In January 2018, Hulu announced that it had reached 17 million subscribers. On August 8, 2016, Hulu announced that it would discontinue its free video on-demand content, and syndicate it to Yahoo! on a new website known as Yahoo! Screen. This service featured recent episodes of ABC, Fox, and NBC series until its 2019 discontinuation. The Hulu website is now devoted exclusively to the subscription service. In May 2018, Hulu introduced 5.1 surround sound on select devices for its original content. In December 2016 Hulu began streaming content in 4K, also limited to its original content. 4K video was quietly rolled back in 2018, and reintroduced in July 2019. Hulu added HDR for some of its original content in August 2021. On January 23, 2019, Hulu announced a $2 price drop for the basic ad-supported plan to $5.99. The $5.99 monthly plan has previously been offered as a promotional offer since late 2017 where users that signed up (or reactivated accounts that had previously ended their service) during the offer period would keep the price for an entire year before paying the regular rate. Since the launch of Disney+ in November 2019, the service has been available in the United States in a bundle with Hulu and ESPN+, priced at $12.99 per-month for the ad-supported tier of Hulu, and $18.99 for the ad-free tier of Hulu. On September 7, 2021, Disney announced that Hulu would be getting a price increase on October 8, 2021. The ad-supported Hulu plan would increase from $5.99 to $6.99 a month, while the ad-free Hulu plan would increase from $11.99 to $12.99 a month. The Hulu live TV plan and the Disney bundle, which includes Disney+, Hulu with ads and ESPN+ for $13.99 a month, would not get a price increase at this time. On May 4, 2016, Hulu announced that it planned to begin offering an over-the-top "live programming from broadcast and cable brands" some time in 2017. On November 1, 2016, co-owners 21st Century Fox, including Fox Networks Group (Fox, Fox Sports, Fox News Channel, FX Networks, and National Geographic) and the Walt Disney Company, including Disney–ABC Television Group and ESPN Inc. (ABC, Disney Channel, Disney Jr., Disney XD, Freeform, ESPN, ESPN2, ESPNU, SEC Network, and ESPN3) agreed to supply their channels to the streaming service, joined by Warner Bros. Discovery, including Turner Broadcasting System (TBS, TNT, Turner Classic Movies, TruTV, CNN, HLN, CNN International, Cartoon Network, Adult Swim, and Boomerang) on August 3, 2016, which previously reached an agreement with Hulu. The service, originally marketed as "Hulu with Live TV," launched in beta on May 3, 2017, featuring content from NBCUniversal (Bravo, Cozi TV, NBC, Oxygen, SYFY, Universal Kids, and Telemundo), A+E Networks (A&E, History, and Lifetime), CBS Corporation (CBS, Pop TV, Smithsonian Channel, and Showtime), and Scripps Networks Interactive (Cooking Channel, Food Network, and HGTV). The service was later renamed "Hulu + Live TV" and included live streams of more than 75 broadcast and cable-originated channels, including feeds of the five major broadcast networks – ABC, CBS, NBC, Fox and The CW – as well as cable channels owned by Hulu-part-owner Disney, along with NFL Network, Paramount Global with Showtime, A+E Networks, Comcast's NBCUniversal, Fox Corporation, Warner Bros. Discovery with HBO, Cinemax, and Starz available as add-ons for an extra fee. Hulu representatives stated that it intends to negotiate carriage agreements with independently owned broadcasting groups to gain distribution rights to local stations from additional markets. By May 2018, the service had reached 800,000 subscribers. On November 29, 2018, Hulu + Live TV added the Discovery Networks (Discovery, TLC, MotorTrend, Animal Planet and Investigation Discovery) to the Scripps Networks Interactive package featured within the Hulu + Live TV core offering. More Discovery-brand channels were also made available through add-on packages; Destination America, Discovery Family, Science Channel, Discovery Life, and American Heroes Channel were added to the $7.99-per-month Entertainment package and Discovery Channel and Discovery Familia were added to the $4.99-per-month Spanish language package. In the third quarter of 2019, Hulu overtook Sling TV as the top OTT pay television service in the United States, with 2.7 million subscribers. The service was initially priced at $39.99 per-month. In December 2019, the price had been increased to $54.99 per month (after having previously been raised to $44.99). In November 2020, the rate for Hulu + Live TV increased to $64.99 per month. The rate for the ad-free plan with Live TV included also increased to $70.99. On January 19, 2021, Nexstar's NewsNation launched on Hulu + Live TV. On April 30, the service added nine ViacomCBS (now Paramount) networks (BET, Comedy Central, MTV, Nickelodeon, Paramount Network, VH1, CMT, Nick Jr. Channel, and TV Land) to the base package, along with BET Her, MTV2, MTV Classic, Nicktoons and TeenNick on the Entertainment add-on. On November 10, Disney stated that Hulu + Live TV had reached four million subscribers. On December 21, it was announced that unlimited DVR, Disney+ and ESPN+ will be included with Hulu + Live TV moving forward, but the price of the service would be increased by $5. On November 14, 2022, Hulu announced that it had added The Weather Channel and Comedy.TV at the start of the month and that Hallmark Channel and Hallmark Movies & Mysteries would be added that day. Hallmark Drama also became available in the Entertainment Add-On. Hulu also announced that on December 1, five Vevo music video channels would be launched, along with theGrio Television Network, JusticeCentral.TV, and The Weather Channel en Español. On January 6, 2025, FuboTV agreed to sell a 70% majority stake in its vMVPD business to Disney and merge with Hulu's live TV service. The merged company will be led by Fubo's executive team and remain a public company, but with Disney holding majority control of its board. Both the Fubo and Hulu + Live TV services will continue to operate under their respective brands, with Fubo being responsible for carriage negotiations. The deal excludes the Hulu video on-demand service, which will continue to be exclusively held by Disney. As part of the agreement, Fubo also settled with a lawsuit against ESPN Inc. (majority-owned by Disney), Fox Corporation, and Warner Bros. Discovery due to their announcement of a sports streaming joint venture, with Fubo winning a lawsuit in August 2024 and being granted a preliminary injection to stop its launch. The consortium plans to make a one-time payment of $220 million. Fubo also reached a carriage agreement for Disney's suite of channels. The merger is expected to be completed between 12 and 18 months, pending regulatory approval. On May 22, 2025, Hulu reached a carriage agreement with TelevisaUnivision, adding Univision, UniMás, TUDN, and Galavisión to Hulu + Live TV beginning June 3, 2025. The agreement was made ahead of the 2025 CONCACAF Gold Cup. Viewership Viewership numbers for the site are tracked by measurement firms such as YouGov, Comscore, Nielsen Media Research, and Quantcast. In partnership with comScore, Hulu is the first digital company to receive multi-platform measurement at an individual level that includes co-viewing for living room devices.[citation needed] The reliability of these metrics has been drawn into question, partly due to widely divergent estimates. For example, between May and June 2010, ComScore updated its scoring methodology and its estimates for Hulu. Hulu's viewers would go from 43.5 million to 24 million in one month. In a comScore digital trends report in 2010, comScore's Digital Year in Review report found that Hulu was watched twice as much as viewers who watched on the websites of the five major TV networks combined. Hulu in May 2018 announced it has surpassed 20 million subscribers in the United States. The tally, which puts the company about 36 million subscriptions behind Netflix, was disclosed at a media presentation at the newly named Hulu Theater at Madison Square Garden in New York. "Hulu said it has grown total engagement by more than 60%, with 78% of viewing taking place in the living room on connected TVs." Awards and nominations Hulu original series The Handmaid's Tale won two awards at the 33rd annual Television Critics Association Awards for Program of the Year and Outstanding Achievement in Drama. At the 69th Primetime Emmy Awards, Hulu earned a total of eight awards for the series and became the first streaming service to win Outstanding Drama Series. The Handmaid's Tale also received Emmys for Outstanding Directing, Outstanding Writing, Outstanding Cinematography and Outstanding Production Design. Elisabeth Moss won the Emmy for Outstanding Lead Actress, and Ann Dowd the award for Outstanding Supporting Actress. At the 75th Golden Globe Awards The Handmaid's Tale took home two awards, Best TV Drama and Best Actress in a Drama TV Series (Elisabeth Moss). At the 2016 Critics' Choice Documentary Awards, Hulu's first-released documentary, The Beatles: Eight Days A Week – The Touring Years won the award for Best Music Documentary. The documentary also received Grammy Awards for Best Music Film at the 2017 Grammy Awards and Best Documentary at the 16th Annual Movies for Grownups Awards. At the Creative Arts Emmy Awards, the documentary earned two Emmys including Outstanding Sound Editing and Outstanding Sound Mixing. At the 68th Primetime Emmy Awards in 2016, Hulu received its first Emmy Award nominations for its Original series, 11.22.63 and for Triumph's Election Special 2016. In 2016, Hulu received its first Golden Globe Awards nomination for its original series Casual for TV series, Comedy. In 2020, Hulu original series The Bravest Knight won the GLAAD Media Award for Outstanding Kids and Family Programming. U.S. News & World Report ranked Hulu its 'Best Live Streaming Service' of 2022. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Enceladus#Potential_habitability] | [TOKENS: 10493] |
Contents Enceladus Enceladus is the sixth-largest moon of Saturn and the 18th largest in the Solar System. It is about 500 kilometres (310 miles) in diameter, about a tenth of that of Saturn's largest moon, Titan. It is covered by clean, freshly deposited snow hundreds of meters thick, making it one of the most reflective bodies of the Solar System. Consequently, its surface temperature at noon reaches only −198 °C (75.1 K; −324.4 °F), far colder than a light-absorbing body would be. Despite its small size, Enceladus has a wide variety of surface features, ranging from old, heavily cratered regions to young, tectonically deformed terrain. Enceladus was discovered on August 28, 1789, by William Herschel, but little was known about it until the two Voyager spacecraft, Voyager 1 and Voyager 2, flew by Saturn in 1980 and 1981. In 2005, the spacecraft Cassini started multiple close flybys of Enceladus, revealing its surface and environment in greater detail. In particular, Cassini discovered water-rich plumes venting from the south polar region. Cryovolcanoes near the south pole shoot geyser-like jets of water vapour, molecular hydrogen, other volatiles, and solid material, including sodium chloride crystals and ice particles, into space, totalling about 200 kilograms (440 pounds) per second. More than 100 geysers have been identified. Some of the water vapour falls back as snow, now several hundred metres thick; the rest escapes and supplies most of the material making up Saturn's E ring. According to NASA scientists, the plumes are similar in composition to comets. In 2014, NASA reported that Cassini had found evidence for a large south polar subsurface ocean of liquid water with a thickness of around 10 km (6 mi). The existence of Enceladus's subsurface ocean has since been mathematically modelled and replicated. These observations of active cryoeruptions, along with the finding of escaping internal heat and very few (if any) impact craters in the south polar region, show that Enceladus is currently geologically active. Like many other satellites in the extensive systems of the giant planets, Enceladus participates in an orbital resonance. Its resonance with Dione excites its orbital eccentricity, which is damped by tidal forces, tidally heating its interior and driving the geological activity. Cassini performed chemical analysis of Enceladus's plumes, finding evidence for hydrothermal activity, possibly driving complex chemistry. Ongoing research on Cassini data suggests that Enceladus's hydrothermal environment could be habitable to some of Earth's hydrothermal vent's microorganisms, and that plume-found methane could be produced by such organisms. History Enceladus was discovered by William Herschel on August 28, 1789, during the first use of his new 1.2 m (47 in) 40-foot telescope, then the largest in the world, at Observatory House in Slough, England. Its faint apparent magnitude (HV = +11.7) and its proximity to the much brighter Saturn and Saturn's rings make Enceladus difficult to observe from Earth with smaller telescopes. Like many satellites of Saturn discovered prior to the Space Age, Enceladus was first observed during a Saturnian equinox, when Earth is within the ring plane. At such times, the reduction in glare from the rings makes the moons easier to observe. Prior to the Voyager missions the view of Enceladus improved little from the dot first observed by Herschel. Only its orbital characteristics were known, with estimations of its mass, density and albedo. Enceladus is named after the giant Enceladus of Greek mythology. The name, like the names of each of the first seven satellites of Saturn to be discovered, was suggested by William Herschel's son John Herschel in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope. He chose these names because Saturn, known in Greek mythology as Cronus, was the leader of the Titans. Geological features on Enceladus are named by the International Astronomical Union (IAU) after characters and places from Richard Francis Burton's 1885 translation of The Book of One Thousand and One Nights. Impact craters are named after characters, whereas other feature types, such as fossae (long, narrow depressions), dorsa (ridges), planitiae (plains), sulci (long parallel grooves), and rupes (cliffs) are named after places. The IAU has officially named 85 features on Enceladus, most recently Samaria Rupes, formerly called Samaria Fossa. Planetary moons other than Earth's were never given symbols in the astronomical literature. Denis Moskowitz, a software engineer who designed most of the dwarf planet symbols, proposed a Greek epsilon (the initial of Enceladus) combined with the crook of the Saturn symbol as the symbol of Enceladus (). This symbol is not widely used. Shape and size Enceladus is a relatively small satellite composed of ice and rock. It is a scalene ellipsoid in shape; its diameters, calculated from images taken by Cassini's ISS (Imaging Science Subsystem) instrument, are 513 km between the sub- and anti-Saturnian poles, 503 km between the leading and trailing hemispheres, and 497 km between the north and south poles. Enceladus is only one-seventh the diameter of Earth's Moon. It ranks sixth in both mass and size among the satellites of Saturn, after Titan (5,150 km), Rhea (1,530 km), Iapetus (1,440 km), Dione (1,120 km) and Tethys (1,050 km). Orbit and rotation Enceladus is one of the major inner satellites of Saturn along with Dione, Tethys, and Mimas. It orbits at 238,000 km (148,000 mi) from Saturn's center and 180,000 km (110,000 mi) from its cloud tops, between the orbits of Mimas and Tethys. It orbits Saturn every 32.9 hours, fast enough for its motion to be observed over a single night of observation. Enceladus is currently in a 2:1 mean-motion orbital resonance with Dione, completing two orbits around Saturn for every one orbit completed by Dione. This resonance maintains Enceladus's orbital eccentricity (0.0047), which is known as a forced eccentricity. This non-zero eccentricity results in tidal deformation of Enceladus. The dissipated heat resulting from this deformation is the main heating source for Enceladus's geologic activity. Enceladus orbits within the densest part of Saturn's E ring, the outermost of its major rings, and is the main source of the ring's material composition. Like most of Saturn's larger satellites, Enceladus rotates synchronously with its orbital period, keeping one face pointed toward Saturn. Unlike Earth's Moon, Enceladus does not appear to librate more than 1.5° about its spin axis. However, analysis of the shape of Enceladus suggests that at some point it was in a 1:4 forced secondary spin–orbit libration. This libration could have provided Enceladus with an additional heat source. Plumes from Enceladus, which are similar in composition to comets, have been shown to be the source of the material in Saturn's E ring. The E ring is the widest and outermost ring of Saturn (except for the tenuous Phoebe ring). It is an extremely wide but diffuse disk of microscopic icy or dusty material distributed between the orbits of Mimas and Titan. Mathematical models show that the E ring is unstable, with a lifespan between 10,000 and 1 million years; therefore, particles composing it must be constantly replenished. Enceladus is orbiting inside the ring, at its narrowest but highest density point. In the 1980s, some astronomers suspected that Enceladus is the main source of particles for the ring. This hypothesis was confirmed by Cassini's first two close flybys in 2005. The Cosmic Dust Analyzer (CDA) "detected a large increase in the number of particles near Enceladus", confirming it as the primary source for the E ring. Analysis of the CDA and INMS data suggest that the gas cloud Cassini flew through during the July encounter, and observed from a distance with its magnetometer and UVIS, was actually a water-rich cryovolcanic plume, originating from vents near the south pole. Visual confirmation of venting came in November 2005, when Cassini imaged geyser-like jets of icy particles rising from Enceladus's south polar region. (Although the plume was imaged before, in January and February 2005, additional studies of the camera's response at high phase angles, when the Sun is almost behind Enceladus, and comparison with equivalent high-phase-angle images taken of other Saturnian satellites, were required before this could be confirmed.) Geology Voyager 2 was the first spacecraft to observe Enceladus's surface in detail, in August 1981. Examination of the resulting highest-resolution imagery revealed at least five different types of terrain, including several regions of cratered terrain, regions of smooth (young) terrain, and lanes of ridged terrain often bordering the smooth areas. Extensive linear cracks and scarps were observed. Given the relative lack of craters on the smooth plains, these regions are probably less than a few hundred million years old. Accordingly, Enceladus must have been recently active with "water volcanism" or other processes that renew the surface. The fresh, clean ice that dominates its surface makes Enceladus the most reflective body in the Solar System, with a visual geometric albedo of 1.38 and bolometric Bond albedo of 0.81±0.04. Because it reflects so much sunlight, its surface only reaches a mean noon temperature of −198 °C (−324 °F), somewhat colder than other Saturnian satellites. Observations during three flybys on February 17, March 9, and July 14, 2005, revealed Enceladus's surface features in much greater detail than the Voyager 2 observations. The smooth plains, which Voyager 2 had observed, resolved into relatively crater-free regions filled with numerous small ridges and scarps. Numerous fractures were found within the older, cratered terrain, suggesting that the surface has been subjected to extensive deformation since the craters were formed. Some areas contain no craters, indicating major resurfacing events in the geologically recent past. There are fissures, plains, corrugated terrain and other crustal deformations. Several additional regions of young terrain were discovered in areas not well imaged by either Voyager spacecraft, such as the bizarre terrain near the south pole. All of this indicates that Enceladus's interior is liquid today, even though it should have been frozen long ago. The Enceladean surface is covered in snow deposited by its geysers. It is several hundred metres in depth in most places, up to an estimated 700 meters at its thickest. Its depth can be estimated by how it sinks into fissures in the surface. In order for it to be as thick as it is, without being more compacted than it is, the geysers must have recently been more active than they are now. Impact cratering is a common occurrence on many Solar System bodies. Much of Enceladus's surface is covered with craters at various densities and levels of degradation. This subdivision of cratered terrains on the basis of crater density (and thus surface age) suggests that Enceladus has been resurfaced in multiple stages. Cassini observations provided a much closer look at the crater distribution and size, showing that many of Enceladus's craters are heavily degraded through viscous relaxation and fracturing. Viscous relaxation allows gravity, over geologic time scales, to deform craters and other topographic features formed in water ice, reducing the amount of topography over time. The rate at which this occurs is dependent on the temperature of the ice: warmer ice is easier to deform than colder, stiffer ice. Viscously relaxed craters tend to have domed floors, or are recognized as craters only by a raised, circular rim. Dunyazad crater is a prime example of a viscously relaxed crater on Enceladus, with a prominent domed floor. Voyager 2 found several types of tectonic features on Enceladus, including troughs, scarps, and belts of grooves and ridges. Results from Cassini suggest that tectonics is the dominant mode of deformation on Enceladus, including rifts, one of the more dramatic types of tectonic features that were noted. These canyons can be up to 200 km long, 5–10 km wide, and 1 km deep. Such features are geologically young, because they cut across other tectonic features and have sharp topographic relief with prominent outcrops along the cliff faces. Evidence of tectonics on Enceladus is also derived from grooved terrain, consisting of lanes of curvilinear grooves and ridges. These bands, first discovered by Voyager 2, often separate smooth plains from cratered regions. Grooved terrains such as the Samarkand Sulci are reminiscent of grooved terrain on Ganymede. Unlike those seen on Ganymede, grooved topography on Enceladus is generally more complex. Rather than parallel sets of grooves, these lanes often appear as bands of crudely aligned, chevron-shaped features. In other areas, these bands bow upwards with fractures and ridges running the length of the feature. Cassini observations of the Samarkand Sulci have revealed dark spots (125 and 750 m wide) located parallel to the narrow fractures. Currently, these spots are interpreted as collapse pits within these ridged plain belts. In addition to deep fractures and grooved lanes, Enceladus has several other types of tectonic terrain. Many of these fractures are found in bands cutting across cratered terrain. These fractures probably propagate down only a few hundred metres into the crust. Many have probably been influenced during their formation by the weakened regolith produced by impact craters, often changing the strike of the propagating fracture. Another example of tectonic features on Enceladus are the linear grooves first found by Voyager 2 and seen at a much higher resolution by Cassini. These linear grooves can be seen cutting across other terrain types, like the groove and ridge belts. Like the deep rifts, they are among the youngest features on Enceladus. However, some linear grooves have been softened like the craters nearby, suggesting that they are older. Ridges have also been observed on Enceladus, though not nearly to the extent as those seen on Europa. These ridges are relatively limited in extent and are up to one kilometre tall. One-kilometer high domes have also been observed. Given the level of resurfacing found on Enceladus, it is clear that tectonic movement has been an important driver of geology for much of its history. Two regions of smooth plains were observed by Voyager 2. They generally have low relief and have far fewer craters than in the cratered terrains, indicating a relatively young surface age. In one of the smooth plain regions, Sarandib Planitia, no impact craters were visible down to the limit of resolution. Another region of smooth plains to the southwest of Sarandib is criss-crossed by several troughs and scarps. Cassini has since viewed these smooth plains regions, like Sarandib Planitia and Diyar Planitia at much higher resolution. Cassini images show these regions filled with low-relief ridges and fractures, probably caused by shear deformation. The high-resolution images of Sarandib Planitia revealed a number of small impact craters, which allow for an estimate of the surface age, either 170 million years or 3.7 billion years, depending on assumed impactor population.[b] The expanded surface coverage provided by Cassini has allowed for the identification of additional regions of smooth plains, particularly on Enceladus's leading hemisphere (the side of Enceladus that faces the direction of motion as it orbits Saturn). Rather than being covered in low-relief ridges, this region is covered in numerous criss-crossing sets of troughs and ridges, similar to the deformation seen in the south polar region. This area is on the opposite side of Enceladus from Sarandib and Diyar Planitiae, suggesting that the placement of these regions is influenced by Saturn's tides on Enceladus. Images taken by Cassini during the flyby on July 14, 2005, revealed a distinctive, tectonically deformed region surrounding Enceladus's south pole. This area, reaching as far north as 60° south latitude, is covered in tectonic fractures and ridges. The area has few sizeable impact craters, suggesting that it is the youngest surface on Enceladus and on any of the mid-sized icy satellites. Modelling of the cratering rate suggests that some regions of the south polar terrain are possibly as young as 500,000 years or less. Near the center of this terrain are four fractures bounded by ridges, unofficially called "tiger stripes". They appear to be the youngest features in this region and are surrounded by mint-green-colored (in false colour, UV–green–near IR images), coarse-grained water ice, seen elsewhere on the surface within outcrops and fracture walls. Here the "blue" ice is on a flat surface, indicating that the region is young enough not to have been coated by fine-grained water ice from the E ring. Results from the visual and infrared mapping spectrometer (VIMS) instrument suggest that the green-coloured material surrounding the tiger stripes is chemically distinct from the rest of the surface of Enceladus. VIMS detected crystalline water ice in the stripes, suggesting that they are quite young (likely less than 1,000 years old) or the surface ice has been thermally altered in the recent past. VIMS also detected simple organic (carbon-containing) compounds in the tiger stripes, chemistry not found anywhere else on Enceladus thus far. One of these areas of "blue" ice in the south polar region was observed at high resolution during the July 14, 2005, flyby, revealing an area of extreme tectonic deformation and blocky terrain, with some areas covered in boulders 10–100 m across. The boundary of the south polar region is marked by a pattern of parallel, Y- and V-shaped ridges and valleys. The shape, orientation, and location of these features suggest they are caused by changes in the overall shape of Enceladus. As of 2006 there were two theories for what could cause such a shift in shape: the orbit of Enceladus may have migrated inward, leading to an increase in Enceladus's rotation rate. Such a shift would lead to a more oblate shape; or a rising mass of warm, low-density material in Enceladus's interior may have led to a shift in the position of the current south polar terrain from Enceladus's southern mid-latitudes to its south pole. Consequently, the moon's ellipsoid shape would have adjusted to match the new orientation. One problem of the polar flattening hypothesis is that both polar regions should have similar tectonic deformation histories. However, the north polar region is densely cratered, and has a much older surface age than the south pole. Thickness variations in Enceladus's lithosphere is one explanation for this discrepancy. Variations in lithospheric thickness are supported by the correlation between the Y-shaped discontinuities and the V-shaped cusps along the south polar terrain margin and the relative surface age of the adjacent non-south polar terrain regions. The Y-shaped discontinuities, and the north–south trending tension fractures into which they lead, are correlated with younger terrain with presumably thinner lithospheres. The V-shaped cusps are adjacent to older, more heavily cratered terrains. Following Voyager's encounters with Enceladus in the early 1980s, scientists postulated it to be geologically active based on its young, reflective surface and location near the core of the E ring. Based on the connection between Enceladus and the E ring, scientists suspected that Enceladus was the source of material in the E ring, perhaps through venting of water vapour. The first Cassini sighting of a plume of icy particles above Enceladus's south pole came from the Imaging Science Subsystem (ISS) images taken in January and February 2005, though the possibility of a camera artefact delayed an official announcement. Data from the magnetometer instrument during the February 17, 2005, encounter provided evidence for a planetary atmosphere. The magnetometer observed a deflection or "draping" of the magnetic field, consistent with local ionization of neutral gas. During the two following encounters, the magnetometer team determined that gases in Enceladus's atmosphere are concentrated over the south polar region, with atmospheric density away from the pole being much lower. Unlike the magnetometer, the Ultraviolet Imaging Spectrograph failed to detect an atmosphere above Enceladus during the February encounter when it looked over the equatorial region, but did detect water vapour during an occultation over the south polar region during the July encounter. Cassini flew through this gas cloud on a few encounters, allowing instruments such as the ion and neutral mass spectrometer (INMS) and the cosmic dust analyser (CDA) to directly sample the plume. (See 'Composition' section.) The November 2005 images showed the plume's fine structure, revealing numerous jets (perhaps issuing from numerous distinct vents) within a larger, faint component extending out nearly 500 km (310 mi) from the surface. The particles have a bulk velocity of 1.25 ± 0.1 kilometres per second (2,800 ± 220 miles per hour), and a maximum velocity of 3.40 km/s (7,600 mph). Cassini's UVIS later observed gas jets coinciding with the dust jets seen by ISS during a non-targeted encounter with Enceladus in October 2007. The combined analysis of imaging, mass spectrometry, and magnetospheric data suggests that the observed south polar plume emanates from pressurized subsurface chambers, similar to Earth's geysers or fumaroles. Fumaroles are probably the closer analogy, since periodic or episodic emission is an inherent property of geysers. The plumes of Enceladus were observed to be continuous to within a factor of a few. The mechanism that drives and sustains the eruptions is thought to be tidal heating. The intensity of the eruption of the south polar jets varies significantly as a function of the position of Enceladus in its orbit. The plumes are about four times brighter when Enceladus is at apoapsis (the point in its orbit most distant from Saturn) than when it is at periapsis. This is consistent with geophysical calculations which predict the south polar fissures are under compression near periapsis, pushing them shut, and under tension near apoapsis, pulling them open. Strike-slip tectonics may also drive localized extension along alternating (left- and right- lateral) transtensional zones (e.g., pull-apart basins) over the Tiger Stripes, thereby regulating jet activity within these regions. Much of the plume activity consists of broad curtain-like eruptions. Optical illusions from a combination of viewing direction and local fracture geometry previously made the plumes look like discrete jets. The extent to which cryovolcanism really occurs is a subject of some debate. At Enceladus, it appears that cryovolcanism occurs because water-filled cracks are periodically exposed to vacuum, the cracks being opened and closed by tidal stresses. Before the Cassini mission, little was known about the interior of Enceladus. However, flybys by Cassini provided information for models of Enceladus's interior, including a better determination of the mass and shape, high-resolution observations of the surface, and new insights on the interior. Initial mass estimates from the Voyager program missions suggested that Enceladus was composed almost entirely of water ice. However, based on the effects of Enceladus's gravity on Cassini, its mass was determined to be much higher than previously thought, yielding a density of 1.61 g/cm3. This density is higher than those of Saturn's other mid-sized icy satellites, indicating that Enceladus contains a greater percentage of silicates and iron. Castillo, Matson et al. (2005) suggested that Iapetus and the other icy satellites of Saturn formed relatively quickly after the formation of the Saturnian subnebula, and thus were rich in short-lived radionuclides. These radionuclides, like aluminium-26 and iron-60, have short half-lives and would produce interior heating relatively quickly. Without the short-lived variety, Enceladus's complement of long-lived radionuclides would not have been enough to prevent rapid freezing of the interior, even with Enceladus's comparatively high rock–mass fraction, given its small size. Given Enceladus's relatively high rock–mass fraction, the proposed enhancement in 26Al and 60Fe would result in a differentiated body, with an icy mantle and a rocky core. Subsequent radioactive and tidal heating would raise the temperature of the core to 1,000 K, enough to melt the inner mantle. For Enceladus to still be active, part of the core must have also melted, forming magma chambers that would flex under the strain of Saturn's tides. Tidal heating, such as from the resonance with Dione or from libration, would then have sustained these hot spots in the core and would power the current geological activity. In addition to its mass and modelled geochemistry, researchers have also examined Enceladus's shape to determine if it is differentiated. Porco, Helfenstein et al. (2006) used limb measurements to determine that its shape, assuming hydrostatic equilibrium, is consistent with an undifferentiated interior, in contradiction to the geological and geochemical evidence. However, the current shape also supports the possibility that Enceladus is not in hydrostatic equilibrium, and may have rotated faster at some point in the recent past (with a differentiated interior). Gravity measurements by Cassini show that the density of the core is low, indicating that the core contains water in addition to silicates. Evidence of liquid water on Enceladus began to accumulate in 2005, when scientists observed plumes containing water vapour spewing from its south polar surface, with jets moving 250 kg of water vapour every second at up to 2,189 km/h (1,360 mph) into space. Soon after, in 2006 it was determined that Enceladus's plumes are the source of Saturn's E Ring. The sources of salty particles are uniformly distributed along the tiger stripes, whereas sources of "fresh" particles are closely related to the high-speed gas jets. The "salty" particles are heavier and mostly fall back to the surface, whereas the fast "fresh" particles escape to the E ring, explaining its salt-poor composition of 0.5–2% of sodium salts by mass. Gravimetric data from Cassini's December 2010 flybys showed that Enceladus likely has a liquid water ocean beneath its frozen surface, but at the time it was thought the subsurface ocean was limited to the south pole. The top of the ocean probably lies beneath a 30-to-40-kilometre-thick (19 to 25 mi) ice shelf. The ocean may be 10 km (6.2 mi) deep at the south pole. Measurements of Enceladus's "wobble" as it orbits Saturn—called libration—suggests that the entire icy crust is detached from the rocky core and therefore that a global ocean is present beneath the surface. The amount of libration (0.120° ± 0.014°) implies that this global ocean is about 26 to 31 kilometres (16 to 19 miles) deep. For comparison, Earth's ocean has an average depth of 3.7 kilometres. The Cassini spacecraft flew through the southern plumes on several occasions to sample and analyse its composition. As of 2019, the data gathered is still being analysed and interpreted. The plumes' salty composition (-Na, -Cl, -CO3) indicates that the source is a salty subsurface ocean. The INMS instrument detected mostly water vapour, as well as traces of molecular nitrogen, carbon dioxide, and trace amounts of simple hydrocarbons such as methane, propane, acetylene and formaldehyde. The plumes' composition, as measured by the INMS, is similar to that seen at most comets. Cassini also found traces of simple organic compounds in some dust grains, as well as larger organics such as benzene (C6H6), and complex macromolecular organics as large as 200 atomic mass units, and at least 15 carbon atoms in size. The mass spectrometer detected molecular hydrogen (H2) which was in "thermodynamic disequilibrium" with the other components, and found traces of ammonia (NH3). A model suggests that Enceladus's salty ocean (-Na, -Cl, -CO3) has an alkaline pH of 11 to 12. The high pH is interpreted to be a consequence of serpentinization of chondritic rock that leads to the generation of H2, a geochemical source of energy that could support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus's plumes. Further analysis in 2019 was done of the spectral characteristics of ice grains in Enceladus's erupting plumes. The study found that nitrogen-bearing and oxygen-bearing amines were likely present, with significant implications for the availability of amino acids in the internal ocean. The researchers suggested that the compounds on Enceladus could be precursors for "biologically relevant organic compounds". A 2025 paper reported the detection of organic molecules in plume samples taken by the Cosmic Dust Analyzer. During the flyby of July 14, 2005, the Composite Infrared Spectrometer (CIRS) found a warm region near the south pole. Temperatures in this region ranged from 85 to 90 K, with small areas showing as high as 157 K (−116 °C), much too warm to be explained by solar heating, indicating that parts of the south polar region are heated from the interior of Enceladus. The presence of a subsurface ocean under the south polar region is now accepted, but it cannot explain the source of the heat, with an estimated heat flux of 200 mW/m2, which is about 10 times higher than that from radiogenic heating alone. Several explanations for the observed elevated temperatures and the resulting plumes have been proposed, including venting from a subsurface reservoir of liquid water, sublimation of ice, decompression and dissociation of clathrates, and shear heating, but a complete explanation of all the heat sources causing the observed thermal power output of Enceladus has not yet been settled. Heating in Enceladus has occurred through various mechanisms ever since its formation. Radioactive decay in its core may have initially heated it, giving it a warm core and a subsurface ocean, which is now kept above freezing through unidentified mechanisms. Geophysical models indicate that tidal heating is a main heat source, perhaps aided by radioactive decay and some heat-producing chemical reactions. A 2007 study predicted the internal heat of Enceladus, if generated by tidal forces, could be no greater than 1.1 gigawatts, but data from Cassini's infrared spectrometer of the south polar terrain over 16 months, indicate that the internal heat generated power is about 4.7 gigawatts, and suggest that it is in thermal equilibrium. The observed power output of 4.7 gigawatts is challenging to explain from tidal heating alone, so the main source of heat remains a mystery. Most scientists think the observed heat flux of Enceladus is not enough to maintain the subsurface ocean, and therefore any subsurface ocean must be a remnant of a period of higher eccentricity and tidal heating, or the heat is produced through another mechanism. Tidal heating occurs through the tidal friction processes: orbital and rotational energy are dissipated as heat in the crust of an object. In addition, to the extent that tides produce heat along fractures, libration may affect the magnitude and distribution of such tidal shear heating. Tidal dissipation of Enceladus's ice crust is significant because Enceladus has a subsurface ocean. A computer simulation that used data from Cassini was published in November 2017, and it indicates that friction heat from the sliding rock fragments within the permeable and fragmented core of Enceladus could keep its underground ocean warm for up to billions of years. It is thought that if Enceladus had a more eccentric orbit in the past, the enhanced tidal forces could be sufficient to maintain a subsurface ocean, such that a periodic enhancement in eccentricity could maintain a subsurface ocean that periodically changes in size. A 2016 analysis claimed that "a model of the tiger stripes as tidally flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that eruptions are maintained over geological timescales." Previous models suggest that resonant perturbations of Dione could provide the necessary periodic eccentricity changes to maintain the subsurface ocean of Enceladus, if the ocean contains a substantial amount of ammonia. The surface of Enceladus indicates that the entire moon has experienced periods of enhanced heat flux in the past. The present-day radiogenic heating rate is 3.2 × 1015 ergs/s (or 0.32 gigawatts), assuming Enceladus has a composition of ice, iron and silicate materials. Heating from long-lived radioactive isotopes uranium-238, uranium-235, thorium-232 and potassium-40 inside Enceladus would add 0.3 gigawatts to the observed heat flux. The presence of Enceladus's regionally thick subsurface ocean suggests a heat flux ≈10 times higher than that from radiogenic heating in the silicate core. The exotic "hot start" hypothesis posits that Enceladus began as ice and rock that contained rapidly decaying short-lived radioactive isotopes of aluminium, iron and manganese. Enormous amounts of heat were then produced as these isotopes decayed for about 7 million years, resulting in the consolidation of rocky material at the core surrounded by a shell of ice. Although the heat from radioactivity would decrease over time, the combination of radioactivity and tidal forces from Saturn's gravitational tug could prevent the subsurface ocean from freezing. Because no ammonia was initially found in the vented material by INMS or UVIS, which could act as an antifreeze, it was thought such a heated, pressurized chamber would consist of nearly pure liquid water with a temperature of at least 270 K (−3 °C), because pure water requires more energy to melt. In July 2009 it was announced that traces of ammonia had been found in the plumes during flybys in July and October 2008. Reducing the freezing point of water with ammonia would also allow for outgassing and higher gas pressure, and less heat required to power the water plumes. The subsurface layer heating the surface water ice could be an ammonia–water slurry at temperatures as low as 170 K (−103 °C), and thus less energy is required to produce the plume activity. However, the observed 4.7 gigawatts heat flux is enough to power the cryovolcanism without the presence of ammonia. Origin Mimas, the innermost of the round moons of Saturn and directly interior to Enceladus, is a geologically dead body, even though it should experience stronger tidal forces than Enceladus. This apparent paradox can be explained in part by temperature-dependent properties of water ice (the main constituent of the interiors of Mimas and Enceladus). The tidal heating per unit mass is given by the formula where ρ is the (mass) density of the satellite, n is its mean orbital motion, r is the satellite's radius, e is the orbital eccentricity of the satellite, μ is the shear modulus and Q is the dimensionless dissipation factor. For a same-temperature approximation, the expected value of qtid for Mimas is about 40 times that of Enceladus. However, the material parameters μ and Q are temperature dependent. At high temperatures (close to the melting point), μ and Q are low, so tidal heating is high. Modelling suggests that for Enceladus, both a 'basic' low-energy thermal state with little internal temperature gradient, and an 'excited' high-energy thermal state with a significant temperature gradient, and consequent convection (endogenic geologic activity), once established, would be stable. For Mimas, only a low-energy state is expected to be stable, despite its being closer to Saturn. So the model predicts a low-internal-temperature state for Mimas (values of μ and Q are high) but a possible higher-temperature state for Enceladus (values of μ and Q are low). Additional historical information is needed to explain how Enceladus first entered the high-energy state (e.g. more radiogenic heating or a more eccentric orbit in the past). The significantly higher density of Enceladus relative to Mimas (1.61 vs. 1.15 g/cm3), implying a larger content of rock and more radiogenic heating in its early history, has also been cited as an important factor in resolving the Mimas paradox. It has been suggested that for an icy satellite the size of Mimas or Enceladus to enter an 'excited state' of tidal heating and convection, it would need to enter an orbital resonance before it lost too much of its primordial internal heat. Because Mimas, being smaller, would cool more rapidly than Enceladus, its window of opportunity for initiating orbital resonance-driven convection would have been considerably shorter. Enceladus is losing mass at a rate of 200 kg/second. If mass loss at this rate continued for 4.5 Gyr, the satellite would have lost approximately 30% of its initial mass. A similar value is obtained by assuming that the initial densities of Enceladus and Mimas were equal. It suggests that tectonics in the south polar region is probably mainly related to subsidence and associated subduction caused by the process of mass loss. In 2016, a study of how the orbits of Saturn's moons should have changed due to tidal effects suggested that all of Saturn's satellites inward of Titan, including Enceladus (whose geologic activity was used to derive the strength of tidal effects on Saturn's satellites), may have formed as little as 100 million years ago. A later study from 2019 estimated that the ocean is around one billion years old. Enceladus ejects plumes of salted water laced with grains of silica-rich sand, nitrogen (in ammonia), and organic molecules, including trace amounts of simple hydrocarbons such as methane (CH4), propane (C3H8), acetylene (C2H2) and formaldehyde (CH2O), which are carbon-bearing molecules. This indicates that hydrothermal activity —an energy source— may be at work in Enceladus's subsurface ocean. Models indicate that the large rocky core is porous, allowing water to flow through it, transferring heat and chemicals. It was confirmed by observations and other research. Molecular hydrogen (H2), a geochemical source of energy that can be metabolized by methanogen microbes to provide energy for life, could be present if, as models suggest, Enceladus's salty ocean has an alkaline pH from serpentinization of chondritic rock. The presence of an internal global salty ocean with an aquatic environment supported by global ocean circulation patterns, with an energy source and complex organic compounds in contact with Enceladus's rocky core, may advance the study of astrobiology and the study of potentially habitable environments for microbial extraterrestrial life. Geochemical modelling results concerning not-yet-detected phosphorus indicate the moon meets potential abiogenesis-requirements. However, phosphates have been detected from a cryovolcanic plume detected by Cassini and is discussed in a paper in the June 14, 2023, issue of Nature entitled "Detection of Phosphates Originating From Enceladus's Ocean". The presence of a wide range of organic compounds and ammonia indicates their source may be similar to the water/rock reactions known to occur on Earth and that are known to support life. Therefore, several robotic missions have been proposed to further explore Enceladus and assess its habitability. Some of the proposed missions are: Journey to Enceladus and Titan (JET), Enceladus Explorer (En-Ex), Enceladus Life Finder (ELF), Life Investigation For Enceladus (LIFE), and Enceladus Life Signatures and Habitability (ELSAH). In June 2023, astronomers reported that the presence of phosphates on Enceladus has been detected, completing the discovery of all the basic chemical ingredients for life on the moon. On December 14, 2023, astronomers reported the first time discovery, in the plumes of Enceladus, 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." On April 13, 2017, NASA announced the discovery of possible hydrothermal activity on Enceladus's sub-surface ocean floor. In 2015, the Cassini probe made a close fly-by of Enceladus's south pole, flying within 48.3 km (30.0 mi) of the surface, as well as through a plume in the process. A mass spectrometer on the craft detected molecular hydrogen (H2) from the plume, and after months of analysis, the conclusion was made that the hydrogen was most likely the result of hydrothermal activity beneath the surface. It has been speculated that such activity could be a potential oasis of habitability. The presence of ample hydrogen in Enceladus's ocean means that microbes – if any exist there – could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. The chemical reaction is known as "methanogenesis" because it produces methane as a byproduct, and is at the root of the tree of life on Earth, the birthplace of all life that is known to exist. Exploration The two Voyager spacecraft made the first close-up images of Enceladus. Voyager 1 was the first to fly past Enceladus, at a distance of 202,000 km on November 12, 1980. Images acquired from this distance had very poor spatial resolution, but revealed a highly reflective surface devoid of impact craters, indicating a youthful surface. Voyager 1 also confirmed that Enceladus was embedded in the densest part of Saturn's diffuse E ring. Combined with the apparent youthful appearance of the surface, Voyager scientists suggested that the E ring consisted of particles vented from Enceladus's surface. In 2017, a reprocessing of departure images from the probe revealed a possible precovery image of Enceladus's plumes. Voyager 2 passed closer to Enceladus (87,010 km) on August 26, 1981, allowing higher-resolution images to be obtained. These images showed a young surface. They also revealed a surface with different regions with vastly different surface ages, with a heavily cratered mid- to high-northern latitude region, and a lightly cratered region closer to the equator. This geologic diversity contrasts with the ancient, heavily cratered surface of Mimas, another moon of Saturn slightly smaller than Enceladus. The geologically youthful terrains came as a great surprise to the scientific community, because no theory was then able to predict that such a small (and cold, compared to Jupiter's highly active moon Io) celestial body could bear signs of such activity. The answers to many remaining mysteries of Enceladus had to wait until the arrival of the Cassini spacecraft on July 1, 2004, when it entered orbit around Saturn. Given the results from the Voyager 2 images, Enceladus was considered a priority target by the Cassini mission planners, and several targeted flybys within 1,500 km of the surface were planned as well as numerous, "non-targeted" opportunities within 100,000 km of Enceladus. The flybys have yielded significant information concerning Enceladus's surface, as well as the discovery of water vapour with traces of simple hydrocarbons venting from the geologically active south polar region. These discoveries prompted the adjustment of Cassini's flight plan to allow closer flybys of Enceladus, including an encounter in March 2008 that took it to within 48 km of the surface. Cassini's extended mission included seven close flybys of Enceladus between July 2008 and July 2010, including two passes at only 50 km in the later half of 2008. Cassini performed a flyby on October 28, 2015, passing as close as 49 km (30 mi) and through a plume. Confirmation of molecular hydrogen (H2) would be an independent line of evidence that hydrothermal activity is taking place in the Enceladus seafloor, increasing its habitability. Cassini has provided strong evidence that Enceladus has an ocean with an energy source, nutrients and organic molecules, making Enceladus one of the best places for the study of potentially habitable environments for extraterrestrial life. On December 14, 2023, astronomers reported the first time discovery, in the plumes of Enceladus, 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." The discoveries Cassini made at Enceladus have prompted studies into follow-up mission concepts, including a probe flyby (Journey to Enceladus and Titan or JET) to analyse plume contents in situ, a lander by the German Aerospace Center to study the habitability potential of its subsurface ocean (Enceladus Explorer), and two astrobiology-oriented mission concepts (the Enceladus Life Finder and Life Investigation For Enceladus (LIFE)). The European Space Agency (ESA) was assessing concepts in 2008 to send a probe to Enceladus in a mission to be combined with studies of Titan: Titan Saturn System Mission (TSSM). TSSM was a joint NASA/ESA flagship-class proposal for exploration of Saturn's moons, with a focus on Enceladus, and it was competing against the Europa Jupiter System Mission (EJSM) proposal for funding. In February 2009, it was announced that NASA/ESA had given the EJSM mission priority ahead of TSSM, although TSSM will continue to be studied and evaluated. In November 2017, Russian billionaire Yuri Milner expressed interest in funding a "low-cost, privately funded mission to Enceladus which can be launched relatively soon." In September 2018, NASA and the Breakthrough Initiatives, founded by Milner, signed a cooperation agreement for the mission's initial concept phase. The spacecraft would be low-cost, low mass, and would be launched at high speed on an affordable rocket. The spacecraft would be directed to perform a single flyby through Enceladus's plumes in order to sample and analyse its content for biosignatures. NASA provided scientific and technical expertise through various reviews, from March 2019 to December 2019. In 2022, the Planetary Science Decadal Survey by the National Academy of Sciences recommended that NASA prioritize its newest probe concept, the Enceladus Orbilander, as a Flagship-class mission, alongside its newest concepts for a Mars sample-return mission and the Uranus Orbiter and Probe. The Enceladus Orbilander would be launched on a similarly affordable rocket, but would cost about $5 billion, and be designed to endure eighteen months in orbit inspecting Enceladus's plumes before landing and spending two Earth years conducting surface astrobiology research. In 2024, ESA named a mission to Enceladus its top priority. Currently known as the L4 mission, it is an orbiter and lander proposed for launch in 2042, with arrival at Enceladus in 2053. See also References Further reading External links |
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Contents Python (programming language) Python is a high-level, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Python is dynamically type-checked and garbage-collected. It supports multiple programming paradigms, including structured (particularly procedural), object-oriented and functional programming. Guido van Rossum began working on Python in the late 1980s as a successor to the ABC programming language. Python 3.0, released in 2008, was a major revision and not completely backward-compatible with earlier versions. Beginning with Python 3.5, capabilities and keywords for typing were added to the language, allowing optional static typing. As of 2026[update], the Python Software Foundation supports Python 3.10, 3.11, 3.12, 3.13, and 3.14, following the project's annual release cycle and five-year support policy. Python 3.15 is currently in the alpha development phase, and the stable release is expected to come out in October 2026. Earlier versions in the 3.x series have reached end-of-life and no longer receive security updates. Python has gained widespread use in the machine learning community. It is widely taught as an introductory programming language. Since 2003, Python has consistently ranked in the top ten of the most popular programming languages in the TIOBE Programming Community Index, which ranks based on searches in 24 platforms. History Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands. It was designed as a successor to the ABC programming language, which was inspired by SETL, capable of exception handling and interfacing with the Amoeba operating system. Python implementation began in December 1989. Van Rossum first released it in 1991 as Python 0.9.0. Van Rossum assumed sole responsibility for the project, as the lead developer, until 12 July 2018, when he announced his "permanent vacation" from responsibilities as Python's "benevolent dictator for life" (BDFL); this title was bestowed on him by the Python community to reflect his long-term commitment as the project's chief decision-maker. (He has since come out of retirement and is self-titled "BDFL-emeritus".) In January 2019, active Python core developers elected a five-member Steering Council to lead the project. The name Python derives from the British comedy series Monty Python's Flying Circus. (See § Naming.) Python 2.0 was released on 16 October 2000, featuring many new features such as list comprehensions, cycle-detecting garbage collection, reference counting, and Unicode support. Python 2.7's end-of-life was initially set for 2015, and then postponed to 2020 out of concern that a large body of existing code could not easily be forward-ported to Python 3. It no longer receives security patches or updates. While Python 2.7 and older versions are officially unsupported, a different unofficial Python implementation, PyPy, continues to support Python 2, i.e., "2.7.18+" (plus 3.11), with the plus signifying (at least some) "backported security updates". Python 3.0 was released on 3 December 2008, and was a major revision and not completely backward-compatible with earlier versions, with some new semantics and changed syntax. Python 2.7.18, released in 2020, was the last release of Python 2. Several releases in the Python 3.x series have added new syntax to the language, and made a few (considered very minor) backward-incompatible changes. As of January 2026[update], Python 3.14.3 is the latest stable release. All older 3.x versions had a security update down to Python 3.9.24 then again with 3.9.25, the final version in 3.9 series. Python 3.10 is, since November 2025, the oldest supported branch. Python 3.15 has an alpha released, and Android has an official downloadable executable available for Python 3.14. Releases receive two years of full support followed by three years of security support. Design philosophy and features Python is a multi-paradigm programming language. Object-oriented programming and structured programming are fully supported, and many of their features support functional programming and aspect-oriented programming – including metaprogramming and metaobjects. Many other paradigms are supported via extensions, including design by contract and logic programming. Python is often referred to as a 'glue language' because it is purposely designed to be able to integrate components written in other languages. Python uses dynamic typing and a combination of reference counting and a cycle-detecting garbage collector for memory management. It uses dynamic name resolution (late binding), which binds method and variable names during program execution. Python's design offers some support for functional programming in the "Lisp tradition". It has filter, map, and reduce functions; list comprehensions, dictionaries, sets, and generator expressions. The standard library has two modules (itertools and functools) that implement functional tools borrowed from Haskell and Standard ML. Python's core philosophy is summarized in the Zen of Python (PEP 20) written by Tim Peters, which includes aphorisms such as these: However, Python has received criticism for violating these principles and adding unnecessary language bloat. Responses to these criticisms note that the Zen of Python is a guideline rather than a rule. The addition of some new features had been controversial: Guido van Rossum resigned as Benevolent Dictator for Life after conflict about adding the assignment expression operator in Python 3.8. Nevertheless, rather than building all functionality into its core, Python was designed to be highly extensible via modules. This compact modularity has made it particularly popular as a means of adding programmable interfaces to existing applications. Van Rossum's vision of a small core language with a large standard library and easily extensible interpreter stemmed from his frustrations with ABC, which represented the opposite approach. Python claims to strive for a simpler, less-cluttered syntax and grammar, while giving developers a choice in their coding methodology. Python lacks do .. while loops, which Rossum considered harmful. In contrast to Perl's motto "there is more than one way to do it", Python advocates an approach where "there should be one – and preferably only one – obvious way to do it". In practice, however, Python provides many ways to achieve a given goal. There are at least three ways to format a string literal, with no certainty as to which one a programmer should use. Alex Martelli is a Fellow at the Python Software Foundation and Python book author; he wrote that "To describe something as 'clever' is not considered a compliment in the Python culture." Python's developers typically prioritize readability over performance. For example, they reject patches to non-critical parts of the CPython reference implementation that would offer increases in speed that do not justify the cost of clarity and readability.[failed verification] Execution speed can be improved by moving speed-critical functions to extension modules written in languages such as C, or by using a just-in-time compiler like PyPy. Also, it is possible to transpile to other languages. However, this approach either fails to achieve the expected speed-up, since Python is a very dynamic language, or only a restricted subset of Python is compiled (with potential minor semantic changes). Python is meant to be a fun language to use. This goal is reflected in the name – a tribute to the British comedy group Monty Python – and in playful approaches to some tutorials and reference materials. For instance, some code examples use the terms "spam" and "eggs" (in reference to a Monty Python sketch), rather than the typical terms "foo" and "bar". A common neologism in the Python community is pythonic, which has a broad range of meanings related to program style: Pythonic code may use Python idioms well; be natural or show fluency in the language; or conform with Python's minimalist philosophy and emphasis on readability. Syntax and semantics Python is meant to be an easily readable language. Its formatting is visually uncluttered and often uses English keywords where other languages use punctuation. Unlike many other languages, it does not use curly brackets to delimit blocks, and semicolons after statements are allowed but rarely used. It has fewer syntactic exceptions and special cases than C or Pascal. Python uses whitespace indentation, rather than curly brackets or keywords, to delimit blocks. An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block. Thus, the program's visual structure accurately represents its semantic structure. This feature is sometimes termed the off-side rule. Some other languages use indentation this way; but in most, indentation has no semantic meaning. The recommended indent size is four spaces. Python's statements include the following: The assignment statement (=) binds a name as a reference to a separate, dynamically allocated object. Variables may subsequently be rebound at any time to any object. In Python, a variable name is a generic reference holder without a fixed data type; however, it always refers to some object with a type. This is called dynamic typing—in contrast to statically-typed languages, where each variable may contain only a value of a certain type. Python does not support tail call optimization or first-class continuations; according to Van Rossum, the language never will. However, better support for coroutine-like functionality is provided by extending Python's generators. Before 2.5, generators were lazy iterators; data was passed unidirectionally out of the generator. From Python 2.5 on, it is possible to pass data back into a generator function; and from version 3.3, data can be passed through multiple stack levels. Python's expressions include the following: In Python, a distinction between expressions and statements is rigidly enforced, in contrast to languages such as Common Lisp, Scheme, or Ruby. This distinction leads to duplicating some functionality, for example: A statement cannot be part of an expression; because of this restriction, expressions such as list and dict comprehensions (and lambda expressions) cannot contain statements. As a particular case, an assignment statement such as a = 1 cannot be part of the conditional expression of a conditional statement. Python uses duck typing, and it has typed objects but untyped variable names. Type constraints are not checked at definition time; rather, operations on an object may fail at usage time, indicating that the object is not of an appropriate type. Despite being dynamically typed, Python is strongly typed, forbidding operations that are poorly defined (e.g., adding a number and a string) rather than quietly attempting to interpret them. Python allows programmers to define their own types using classes, most often for object-oriented programming. New instances of classes are constructed by calling the class, for example, SpamClass() or EggsClass()); the classes are instances of the metaclass type (which is an instance of itself), thereby allowing metaprogramming and reflection. Before version 3.0, Python had two kinds of classes, both using the same syntax: old-style and new-style. Current Python versions support the semantics of only the new style. Python supports optional type annotations. These annotations are not enforced by the language, but may be used by external tools such as mypy to catch errors. Python includes a module typing including several type names for type annotations. Also, mypy supports a Python compiler called mypyc, which leverages type annotations for optimization. 1.33333 frozenset() Python includes conventional symbols for arithmetic operators (+, -, *, /), the floor-division operator //, and the modulo operator %. (With the modulo operator, a remainder can be negative, e.g., 4 % -3 == -2.) Also, Python offers the ** symbol for exponentiation, e.g. 5**3 == 125 and 9**0.5 == 3.0. Also, it offers the matrix‑multiplication operator @ . These operators work as in traditional mathematics; with the same precedence rules, the infix operators + and - can also be unary, to represent positive and negative numbers respectively. Division between integers produces floating-point results. The behavior of division has changed significantly over time: In Python terms, the / operator represents true division (or simply division), while the // operator represents floor division. Before version 3.0, the / operator represents classic division. Rounding towards negative infinity, though a different method than in most languages, adds consistency to Python. For instance, this rounding implies that the equation (a + b)//b == a//b + 1 is always true. Also, the rounding implies that the equation b*(a//b) + a%b == a is valid for both positive and negative values of a. As expected, the result of a%b lies in the half-open interval [0, b), where b is a positive integer; however, maintaining the validity of the equation requires that the result must lie in the interval (b, 0] when b is negative. Python provides a round function for rounding a float to the nearest integer. For tie-breaking, Python 3 uses the round to even method: round(1.5) and round(2.5) both produce 2. Python versions before 3 used the round-away-from-zero method: round(0.5) is 1.0, and round(-0.5) is −1.0. Python allows Boolean expressions that contain multiple equality relations to be consistent with general usage in mathematics. For example, the expression a < b < c tests whether a is less than b and b is less than c. C-derived languages interpret this expression differently: in C, the expression would first evaluate a < b, resulting in 0 or 1, and that result would then be compared with c. Python uses arbitrary-precision arithmetic for all integer operations. The Decimal type/class in the decimal module provides decimal floating-point numbers to a pre-defined arbitrary precision with several rounding modes. The Fraction class in the fractions module provides arbitrary precision for rational numbers. Due to Python's extensive mathematics library and the third-party library NumPy, the language is frequently used for scientific scripting in tasks such as numerical data processing and manipulation. Functions are created in Python by using the def keyword. A function is defined similarly to how it is called, by first providing the function name and then the required parameters. Here is an example of a function that prints its inputs: To assign a default value to a function parameter in case no actual value is provided at run time, variable-definition syntax can be used inside the function header. Code examples "Hello, World!" program: Program to calculate the factorial of a non-negative integer: Libraries Python's large standard library is commonly cited as one of its greatest strengths. For Internet-facing applications, many standard formats and protocols such as MIME and HTTP are supported. The language includes modules for creating graphical user interfaces, connecting to relational databases, generating pseudorandom numbers, arithmetic with arbitrary-precision decimals, manipulating regular expressions, and unit testing. Some parts of the standard library are covered by specifications—for example, the Web Server Gateway Interface (WSGI) implementation wsgiref follows PEP 333—but most parts are specified by their code, internal documentation, and test suites. However, because most of the standard library is cross-platform Python code, only a few modules must be altered or rewritten for variant implementations. As of 13 March 2025,[update] the Python Package Index (PyPI), the official repository for third-party Python software, contains over 614,339 packages. Development environments Most[which?] Python implementations (including CPython) include a read–eval–print loop (REPL); this permits the environment to function as a command line interpreter, with which users enter statements sequentially and receive results immediately. Also, CPython is bundled with an integrated development environment (IDE) called IDLE, which is oriented toward beginners.[citation needed] Other shells, including IDLE and IPython, add additional capabilities such as improved auto-completion, session-state retention, and syntax highlighting. Standard desktop IDEs include PyCharm, Spyder, and Visual Studio Code; there are web browser-based IDEs, such as the following environments: Implementations CPython is the reference implementation of Python. This implementation is written in C, meeting the C11 standard since version 3.11. Older versions use the C89 standard with several select C99 features, but third-party extensions are not limited to older C versions—e.g., they can be implemented using C11 or C++. CPython compiles Python programs into an intermediate bytecode, which is then executed by a virtual machine. CPython is distributed with a large standard library written in a combination of C and native Python. CPython is available for many platforms, including Windows and most modern Unix-like systems, including macOS (and Apple M1 Macs, since Python 3.9.1, using an experimental installer). Starting with Python 3.9, the Python installer intentionally fails to install on Windows 7 and 8; Windows XP was supported until Python 3.5, with unofficial support for VMS. Platform portability was one of Python's earliest priorities. During development of Python 1 and 2, even OS/2 and Solaris were supported; since that time, support has been dropped for many platforms. All current Python versions (since 3.7) support only operating systems that feature multithreading, by now supporting not nearly as many operating systems (dropping many outdated) than in the past. All alternative implementations have at least slightly different semantics. For example, an alternative may include unordered dictionaries, in contrast to other current Python versions. As another example in the larger Python ecosystem, PyPy does not support the full C Python API. Creating an executable with Python often is done by bundling an entire Python interpreter into the executable, which causes binary sizes to be massive for small programs, yet there exist implementations that are capable of truly compiling Python. Alternative implementations include the following: Stackless Python is a significant fork of CPython that implements microthreads. This implementation uses the call stack differently, thus allowing massively concurrent programs. PyPy also offers a stackless version. Just-in-time Python compilers have been developed, but are now unsupported: There are several compilers/transpilers to high-level object languages; the source language is unrestricted Python, a subset of Python, or a language similar to Python: There are also specialized compilers: Some older projects existed, as well as compilers not designed for use with Python 3.x and related syntax: A performance comparison among various Python implementations, using a non-numerical (combinatorial) workload, was presented at EuroSciPy '13. In addition, Python's performance relative to other programming languages is benchmarked by The Computer Language Benchmarks Game. There are several approaches to optimizing Python performance, despite the inherent slowness of an interpreted language. These approaches include the following strategies or tools: Language Development Python's development is conducted mostly through the Python Enhancement Proposal (PEP) process; this process is the primary mechanism for proposing major new features, collecting community input on issues, and documenting Python design decisions. Python coding style is covered in PEP 8. Outstanding PEPs are reviewed and commented on by the Python community and the steering council. Enhancement of the language corresponds with development of the CPython reference implementation. The mailing list python-dev is the primary forum for the language's development. Specific issues were originally discussed in the Roundup bug tracker hosted by the foundation. In 2022, all issues and discussions were migrated to GitHub. Development originally took place on a self-hosted source-code repository running Mercurial, until Python moved to GitHub in January 2017. CPython's public releases have three types, distinguished by which part of the version number is incremented: Many alpha, beta, and release-candidates are also released as previews and for testing before final releases. Although there is a rough schedule for releases, they are often delayed if the code is not ready yet. Python's development team monitors the state of the code by running a large unit test suite during development. The major academic conference on Python is PyCon. Also, there are special Python mentoring programs, such as PyLadies. Naming Python's name is inspired by the British comedy group Monty Python, whom Python creator Guido van Rossum enjoyed while developing the language. Monty Python references appear frequently in Python code and culture; for example, the metasyntactic variables often used in Python literature are spam and eggs, rather than the traditional foo and bar. Also, the official Python documentation contains various references to Monty Python routines. Python users are sometimes referred to as "Pythonistas". Languages influenced by Python See also Notes References Further reading External links |
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Contents Meta Platforms Meta Platforms, Inc. (doing business as Meta) is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, WhatsApp, Messenger, Threads and Manus. The company also operates an advertising network for its own sites and third parties; as of 2023[update], advertising accounted for 97.8 percent of its total revenue. Meta has been described as a part of Big Tech, which refers to the largest six tech companies in the United States, Alphabet (Google), Amazon, Apple, Meta (Facebook), Microsoft, and Nvidia, which are also the largest companies in the world by market capitalization. The company was originally established in 2004 as TheFacebook, Inc., and was renamed Facebook, Inc. in 2005. In 2021, it rebranded as Meta Platforms, Inc. to reflect a strategic shift toward developing the metaverse—an interconnected digital ecosystem spanning virtual and augmented reality technologies. In 2023, Meta was ranked 31st on the Forbes Global 2000 list of the world's largest public companies. As of 2022, it was the world's third-largest spender on research and development, with R&D expenses totaling US$35.3 billion. History Facebook filed for an initial public offering (IPO) on January 1, 2012. The preliminary prospectus stated that the company sought to raise $5 billion, had 845 million monthly active users, and a website accruing 2.7 billion likes and comments daily. After the IPO, Zuckerberg would retain 22% of the total shares and 57% of the total voting power in Facebook. Underwriters valued the shares at $38 each, valuing the company at $104 billion, the largest valuation yet for a newly public company. On May 16, one day before the IPO, Facebook announced it would sell 25% more shares than originally planned due to high demand. The IPO raised $16 billion, making it the third-largest in US history (slightly ahead of AT&T Mobility and behind only General Motors and Visa). The stock price left the company with a higher market capitalization than all but a few U.S. corporations—surpassing heavyweights such as Amazon, McDonald's, Disney, and Kraft Foods—and made Zuckerberg's stock worth $19 billion. The New York Times stated that the offering overcame questions about Facebook's difficulties in attracting advertisers to transform the company into a "must-own stock". Jimmy Lee of JPMorgan Chase described it as "the next great blue-chip". Writers at TechCrunch, on the other hand, expressed skepticism, stating, "That's a big multiple to live up to, and Facebook will likely need to add bold new revenue streams to justify the mammoth valuation." Trading in the stock, which began on May 18, was delayed that day due to technical problems with the Nasdaq exchange. The stock struggled to stay above the IPO price for most of the day, forcing underwriters to buy back shares to support the price. At the closing bell, shares were valued at $38.23, only $0.23 above the IPO price and down $3.82 from the opening bell value. The opening was widely described by the financial press as a disappointment. The stock set a new record for trading volume of an IPO. On May 25, 2012, the stock ended its first full week of trading at $31.91, a 16.5% decline. On May 22, 2012, regulators from Wall Street's Financial Industry Regulatory Authority announced that they had begun to investigate whether banks underwriting Facebook had improperly shared information only with select clients rather than the general public. Massachusetts Secretary of State William F. Galvin subpoenaed Morgan Stanley over the same issue. The allegations sparked "fury" among some investors and led to the immediate filing of several lawsuits, one of them a class action suit claiming more than $2.5 billion in losses due to the IPO. Bloomberg estimated that retail investors may have lost approximately $630 million on Facebook stock since its debut. S&P Global Ratings added Facebook to its S&P 500 index on December 21, 2013. On May 2, 2014, Zuckerberg announced that the company would be changing its internal motto from "Move fast and break things" to "Move fast with stable infrastructure". The earlier motto had been described as Zuckerberg's "prime directive to his developers and team" in a 2009 interview in Business Insider, in which he also said, "Unless you are breaking stuff, you are not moving fast enough." In November 2016, Facebook announced the Microsoft Windows client of gaming service Facebook Gameroom, formerly Facebook Games Arcade, at the Unity Technologies developers conference. The client allows Facebook users to play "native" games in addition to its web games. The service was closed in June 2021. Lasso was a short-video sharing app from Facebook similar to TikTok that was launched on iOS and Android in 2018 and was aimed at teenagers. On July 2, 2020, Facebook announced that Lasso would be shutting down on July 10. In 2018, the Oculus lead Jason Rubin sent his 50-page vision document titled "The Metaverse" to Facebook's leadership. In the document, Rubin acknowledged that Facebook's virtual reality business had not caught on as expected, despite the hundreds of millions of dollars spent on content for early adopters. He also urged the company to execute fast and invest heavily in the vision, to shut out HTC, Apple, Google and other competitors in the VR space. Regarding other players' participation in the metaverse vision, he called for the company to build the "metaverse" to prevent their competitors from "being in the VR business in a meaningful way at all". In May 2019, Facebook founded Libra Networks, reportedly to develop their own stablecoin cryptocurrency. Later, it was reported that Libra was being supported by financial companies such as Visa, Mastercard, PayPal and Uber. The consortium of companies was expected to pool in $10 million each to fund the launch of the cryptocurrency coin named Libra. Depending on when it would receive approval from the Swiss Financial Market Supervisory authority to operate as a payments service, the Libra Association had planned to launch a limited format cryptocurrency in 2021. Libra was renamed Diem, before being shut down and sold in January 2022 after backlash from Swiss government regulators and the public. During the COVID-19 pandemic, the use of online services, including Facebook, grew globally. Zuckerberg predicted this would be a "permanent acceleration" that would continue after the pandemic. Facebook hired aggressively, growing from 48,268 employees in March 2020 to more than 87,000 by September 2022. Following a period of intense scrutiny and damaging whistleblower leaks, news started to emerge on October 21, 2021 about Facebook's plan to rebrand the company and change its name. In the Q3 2021 earnings call on October 25, Mark Zuckerberg discussed the ongoing criticism of the company's social services and the way it operates, and pointed to the pivoting efforts to building the metaverse – without mentioning the rebranding and the name change. The metaverse vision and the name change from Facebook, Inc. to Meta Platforms was introduced at Facebook Connect on October 28, 2021. Based on Facebook's PR campaign, the name change reflects the company's shifting long term focus of building the metaverse, a digital extension of the physical world by social media, virtual reality and augmented reality features. "Meta" had been registered as a trademark in the United States in 2018 (after an initial filing in 2015) for marketing, advertising, and computer services, by a Canadian company that provided big data analysis of scientific literature. This company was acquired in 2017 by the Chan Zuckerberg Initiative (CZI), a foundation established by Zuckerberg and his wife, Priscilla Chan, and became one of their projects. Following the rebranding announcement, CZI announced that it had already decided to deprioritize the earlier Meta project, thus it would be transferring its rights to the name to Meta Platforms, and the previous project would end in 2022. Soon after the rebranding, in early February 2022, Meta reported a greater-than-expected decline in profits in the fourth quarter of 2021. It reported no growth in monthly users, and indicated it expected revenue growth to stall. It also expected measures taken by Apple Inc. to protect user privacy to cost it some $10 billion in advertisement revenue, an amount equal to roughly 8% of its revenue for 2021. In meeting with Meta staff the day after earnings were reported, Zuckerberg blamed competition for user attention, particularly from video-based apps such as TikTok. The 27% reduction in the company's share price which occurred in reaction to the news eliminated some $230 billion of value from Meta's market capitalization. Bloomberg described the decline as "an epic rout that, in its sheer scale, is unlike anything Wall Street or Silicon Valley has ever seen". Zuckerberg's net worth fell by as much as $31 billion. Zuckerberg owns 13% of Meta, and the holding makes up the bulk of his wealth. According to published reports by Bloomberg on March 30, 2022, Meta turned over data such as phone numbers, physical addresses, and IP addresses to hackers posing as law enforcement officials using forged documents. The law enforcement requests sometimes included forged signatures of real or fictional officials. When asked about the allegations, a Meta representative said, "We review every data request for legal sufficiency and use advanced systems and processes to validate law enforcement requests and detect abuse." In June 2022, Sheryl Sandberg, the chief operating officer of 14 years, announced she would step down that year. Zuckerberg said that Javier Olivan would replace Sandberg, though in a “more traditional” role. In March 2022, Meta (except Meta-owned WhatsApp) and Instagram were banned in Russia and added to the Russian list of terrorist and extremist organizations for alleged Russophobia and hate speech (up to genocidal calls) amid the ongoing Russian invasion of Ukraine. Meta appealed against the ban, but it was upheld by a Moscow court in June of the same year. Also in March 2022, Meta and Italian eyewear giant Luxottica released Ray-Ban Stories, a series of smartglasses which could play music and take pictures. Meta and Luxottica parent company EssilorLuxottica declined to disclose sales on the line of products as of September 2022, though Meta has expressed satisfaction with its customer feedback. In July 2022, Meta saw its first year-on-year revenue decline when its total revenue slipped by 1% to $28.8bn. Analysts and journalists accredited the loss to its advertising business, which has been limited by Apple's app tracking transparency feature and the number of people who have opted not to be tracked by Meta apps. Zuckerberg also accredited the decline to increasing competition from TikTok. On October 27, 2022, Meta's market value dropped to $268 billion, a loss of around $700 billion compared to 2021, and its shares fell by 24%. It lost its spot among the top 20 US companies by market cap, despite reaching the top 5 in the previous year. In November 2022, Meta laid off 11,000 employees, 13% of its workforce. Zuckerberg said the decision to aggressively increase Meta's investments had been a mistake, as he had wrongly predicted that the surge in e-commerce would last beyond the COVID-19 pandemic. He also attributed the decline to increased competition, a global economic downturn and "ads signal loss". Plans to lay off a further 10,000 employees began in April 2023. The layoffs were part of a general downturn in the technology industry, alongside layoffs by companies including Google, Amazon, Tesla, Snap, Twitter and Lyft. Starting from 2022, Meta scrambled to catch up to other tech companies in adopting specialized artificial intelligence hardware and software. It had been using less expensive CPUs instead of GPUs for AI work, but that approach turned out to be less efficient. The company gifted the Inter-university Consortium for Political and Social Research $1.3 million to finance the Social Media Archive's aim to make their data available to social science research. In 2023, Ireland's Data Protection Commissioner imposed a record EUR 1.2 billion fine on Meta for transferring data from Europe to the United States without adequate protections for EU citizens.: 250 In March 2023, Meta announced a new round of layoffs that would cut 10,000 employees and close 5,000 open positions to make the company more efficient. Meta revenue surpassed analyst expectations for the first quarter of 2023 after announcing that it was increasing its focus on AI. On July 6, Meta launched a new app, Threads, a competitor to Twitter. Meta announced its artificial intelligence model Llama 2 in July 2023, available for commercial use via partnerships with major cloud providers like Microsoft. It was the first project to be unveiled out of Meta's generative AI group after it was set up in February. It would not charge access or usage but instead operate with an open-source model to allow Meta to ascertain what improvements need to be made. Prior to this announcement, Meta said it had no plans to release Llama 2 for commercial use. An earlier version of Llama was released to academics. In August 2023, Meta announced its permanent removal of news content from Facebook and Instagram in Canada due to the Online News Act, which requires Canadian news outlets to be compensated for content shared on its platform. The Online News Act was in effect by year-end, but Meta will not participate in the regulatory process. In October 2023, Zuckerberg said that AI would be Meta's biggest investment area in 2024. Meta finished 2023 as one of the best-performing technology stocks of the year, with its share price up 150 percent. Its stock reached an all-time high in January 2024, bringing Meta within 2% of achieving $1 trillion market capitalization. In November 2023 Meta Platforms launched an ad-free service in Europe, allowing subscribers to opt-out of personal data being collected for targeted advertising. A group of 28 European organizations, including Max Schrems' advocacy group NOYB, the Irish Council for Civil Liberties, Wikimedia Europe, and the Electronic Privacy Information Center, signed a 2024 letter to the European Data Protection Board (EDPB) expressing concern that this subscriber model would undermine privacy protections, specifically GDPR data protection standards. Meta removed the Facebook and Instagram accounts of Iran's Supreme Leader Ali Khamenei in February 2024, citing repeated violations of its Dangerous Organizations & Individuals policy. As of March, Meta was under investigation by the FDA for alleged use of their social media platforms to sell illegal drugs. On 16 May 2024, the European Commission began an investigation into Meta over concerns related to child safety. In May 2023, Iraqi social media influencer Esaa Ahmed-Adnan encountered a troubling issue when Instagram removed his posts, citing false copyright violations despite his content being original and free from copyrighted material. He discovered that extortionists were behind these takedowns, offering to restore his content for $3,000 or provide ongoing protection for $1,000 per month. This scam, exploiting Meta’s rights management tools, became widespread in the Middle East, revealing a gap in Meta’s enforcement in developing regions. An Iraqi nonprofit Tech4Peace’s founder, Aws al-Saadi helped Ahmed-Adnan and others, but the restoration process was slow, leading to significant financial losses for many victims, including prominent figures like Ammar al-Hakim. This situation highlighted Meta’s challenges in balancing global growth with effective content moderation and protection. On 16 September 2024, Meta announced it had banned Russian state media outlets from its platforms worldwide due to concerns about "foreign interference activity." This decision followed allegations that RT and its employees funneled $10 million through shell companies to secretly fund influence campaigns on various social media channels. Meta's actions were part of a broader effort to counter Russian covert influence operations, which had intensified since the invasion. At its 2024 Connect conference, Meta presented Orion, its first pair of augmented reality glasses. Though Orion was originally intended to be sold to consumers, the manufacturing process turned out to be too complex and expensive. Instead, the company pivoted to producing a small number of the glasses to be used internally. On 4 October 2024, Meta announced about its new AI model called Movie Gen, capable of generating realistic video and audio clips based on user prompts. Meta stated it would not release Movie Gen for open development, preferring to collaborate directly with content creators and integrate it into its products by the following year. The model was built using a combination of licensed and publicly available datasets. On October 31, 2024, ProPublica published an investigation into deceptive political advertisement scams that sometimes use hundreds of hijacked profiles and facebook pages run by organized networks of scammers. The authors cited spotty enforcement by Meta as a major reason for the extent of the issue. In November 2024, TechCrunch reported that Meta were considering building a $10bn global underwater cable spanning 25,000 miles. In the same month, Meta closed down 2 million accounts on Facebook and Instagram that were linked to scam centers in Myanmar, Laos, Cambodia, the Philippines, and the United Arab Emirates doing pig butchering scams. In December 2024, Meta announced that, beginning February 2025, they would require advertisers to run ads about financial services in Australia to verify information about who are the beneficiary and the payer in a bid to regulate scams. On December 4, 2024, Meta announced it will invest US$10 billion for its largest AI data center in northeast Louisiana, powered by natural gas facilities. On the 11th of that month, Meta experienced a global outage, impacting accounts on all of their social media and messaging applications. Outage reports from DownDetector reached 70,000+ and 100,000+ within minutes for Instagram and Facebook, respectively. In January 2025, Meta announced plans to roll back its diversity, equity, and inclusion (DEI) initiatives, citing shifts in the "legal and policy landscape" in the United States following the 2024 presidential election. The decision followed reports that CEO Mark Zuckerberg sought to align the company more closely with the incoming Trump administration, including changes to content moderation policies and executive leadership. The new content moderation policies continued to bar insults about a person's intellect or mental illness, but made an exception to allow calling LGBTQ people mentally ill because they are gay or transgender. Later that month, Meta agreed to pay $25 million to settle a 2021 lawsuit brought by Donald Trump for suspending his social media accounts after the January 6 riots. Changes to Meta's moderation policies were controversial among its oversight board, with a significant divide in opinion between the board's US conservatives and its global members. In June 2025, Meta Platforms Inc. has decided to make a multibillion-dollar investment into artificial intelligence startup Scale AI. The financing could exceed $10 billion in value which would make it one of the largest private company funding events of all time. In October 2025, it was announced that Meta would be laying off 600 employees in the artificial intelligence unit to perform better and simpler. They referred to their AI unit as "bloated" and are seeking to trim down the department. This mass layoff is going to impact Meta’s AI infrastructure units, Fundamental Artificial Intelligence Research unit (FAIR) and other product-related positions. Mergers and acquisitions Meta has acquired multiple companies (often identified as talent acquisitions). One of its first major acquisitions was in April 2012, when it acquired Instagram for approximately US$1 billion in cash and stock. In October 2013, Facebook, Inc. acquired Onavo, an Israeli mobile web analytics company. In February 2014, Facebook, Inc. announced it would buy mobile messaging company WhatsApp for US$19 billion in cash and stock. The acquisition was completed on October 6. Later that year, Facebook bought Oculus VR for $2.3 billion in cash and stock, which released its first consumer virtual reality headset in 2016. In late November 2019, Facebook, Inc. announced the acquisition of the game developer Beat Games, responsible for developing one of that year's most popular VR games, Beat Saber. In Late 2022, after Facebook Inc rebranded to Meta Platforms Inc, Oculus was rebranded to Meta Quest. In May 2020, Facebook, Inc. announced it had acquired Giphy for a reported cash price of $400 million. It will be integrated with the Instagram team. However, in August 2021, UK's Competition and Markets Authority (CMA) stated that Facebook, Inc. might have to sell Giphy, after an investigation found that the deal between the two companies would harm competition in display advertising market. Facebook, Inc. was fined $70 million by CMA for deliberately failing to report all information regarding the acquisition and the ongoing antitrust investigation. In October 2022, the CMA ruled for a second time that Meta be required to divest Giphy, stating that Meta already controls half of the advertising in the UK. Meta agreed to the sale, though it stated that it disagrees with the decision itself. In May 2023, Giphy was divested to Shutterstock for $53 million. In November 2020, Facebook, Inc. announced that it planned to purchase the customer-service platform and chatbot specialist startup Kustomer to promote companies to use their platform for business. It has been reported that Kustomer valued at slightly over $1 billion. The deal was closed in February 2022 after regulatory approval. In September 2022, Meta acquired Lofelt, a Berlin-based haptic tech startup. In December 2025, it was announced Meta had acquired the AI-wearables startup, Limitless. In the same month, they also acquired another AI startup, Manus AI, for $2 billion. Manus announced in December that its platform had achieved $100mm in recurring revenue just 8 months after its launch and Meta said it will scale the platform to many other businesses. In January 2026, it was announced Meta proposed acquisition of Manus was undergoing preliminary scrutiny by Chinese regulators. The examination concerns the cross-border transfer of artificial intelligence technology developed in China. Lobbying In 2020, Facebook, Inc. spent $19.7 million on lobbying, hiring 79 lobbyists. In 2019, it had spent $16.7 million on lobbying and had a team of 71 lobbyists, up from $12.6 million and 51 lobbyists in 2018. Facebook was the largest spender of lobbying money among the Big Tech companies in 2020. The lobbying team includes top congressional aide John Branscome, who was hired in September 2021, to help the company fend off threats from Democratic lawmakers and the Biden administration. In December 2024, Meta donated $1 million to the inauguration fund for then-President-elect Donald Trump. In 2025, Meta was listed among the donors funding the construction of the White House State Ballroom. Partnerships February 2026, Meta announced a long-term partnership with Nvidia. Censorship In August 2024, Mark Zuckerberg sent a letter to Jim Jordan indicating that during the COVID-19 pandemic the Biden administration repeatedly asked Meta to limit certain COVID-19 content, including humor and satire, on Facebook and Instagram. In 2016 Meta hired Jordana Cutler, formerly an employee at the Israeli Embassy to the United States, as its policy chief for Israel and the Jewish Diaspora. In this role, Cutler pushed for the censorship of accounts belonging to Students for Justice in Palestine chapters in the United States. Critics have said that Cutler's position gives the Israeli government an undue influence over Meta policy, and that few countries have such high levels of contact with Meta policymakers. Following the election of Donald Trump in 2025, various sources noted possible censorship related to the Democratic Party on Instagram and other Meta platforms. In February 2025, a Meta rep flagged journalist Gil Duran's article and other "critiques of tech industry figures" as spam or sensitive content, limiting their reach. In March 2025, Meta attempted to block former employee Sarah Wynn-Williams from promoting or further distributing her memoir, Careless People, that includes allegations of unaddressed sexual harassment in the workplace by senior executives. The New York Times reports that the arbitration is among Meta's most forcible attempts to repudiate a former employee's account of workplace dynamics. Publisher Macmillan reacted to the ruling by the Emergency International Arbitral Tribunal by stating that it will ignore its provisions. As of 15 March 2025[update], hardback and digital versions of Careless People were being offered for sale by major online retailers. From October 2025, Meta began removing and restricting access for accounts related to LGBTQ, reproductive health and abortion information pages on its platforms. Martha Dimitratou, executive director of Repro Uncensored, called Meta's shadow-banning of these issues "One of the biggest waves of censorship we are seeing". Disinformation concerns Since its inception, Meta has been accused of being a host for fake news and misinformation. In the wake of the 2016 United States presidential election, Zuckerberg began to take steps to eliminate the prevalence of fake news, as the platform had been criticized for its potential influence on the outcome of the election. The company initially partnered with ABC News, the Associated Press, FactCheck.org, Snopes and PolitiFact for its fact-checking initiative; as of 2018, it had over 40 fact-checking partners across the world, including The Weekly Standard. A May 2017 review by The Guardian found that the platform's fact-checking initiatives of partnering with third-party fact-checkers and publicly flagging fake news were regularly ineffective, and appeared to be having minimal impact in some cases. In 2018, journalists working as fact-checkers for the company criticized the partnership, stating that it had produced minimal results and that the company had ignored their concerns. In 2024 Meta's decision to continue to disseminate a falsified video of US president Joe Biden, even after it had been proven to be fake, attracted criticism and concern. In January 2025, Meta ended its use of third-party fact-checkers in favor of a user-run community notes system similar to the one used on X. While Zuckerberg supported these changes, saying that the amount of censorship on the platform was excessive, the decision received criticism by fact-checking institutions, stating that the changes would make it more difficult for users to identify misinformation. Meta also faced criticism for weakening its policies on hate speech that were designed to protect minorities and LGBTQ+ individuals from bullying and discrimination. While moving its content review teams from California to Texas, Meta changed their hateful conduct policy to eliminate restrictions on anti-LGBT and anti-immigrant hate speech, as well as explicitly allowing users to accuse LGBT people of being mentally ill or abnormal based on their sexual orientation or gender identity. In January 2025, Meta faced significant criticism for its role in removing LGBTQ+ content from its platforms, amid its broader efforts to address anti-LGBTQ+ hate speech. The removal of LGBTQ+ themes was noted as part of the wider crackdown on content deemed to violate its community guidelines. Meta's content moderation policies, which were designed to combat harmful speech and protect users from discrimination, inadvertently led to the removal or restriction of LGBTQ+ content, particularly posts highlighting LGBTQ+ identities, support, or political issues. According to reports, LGBTQ+ posts, including those that simply celebrated pride or advocated for LGBTQ+ rights, were flagged and removed for reasons that some critics argue were vague or inconsistently applied. Many LGBTQ+ activists and users on Meta's platforms expressed concern that such actions stifled visibility and expression, potentially isolating LGBTQ+ individuals and communities, especially in spaces that were historically important for outreach and support. Lawsuits Numerous lawsuits have been filed against the company, both when it was known as Facebook, Inc., and as Meta Platforms. In March 2020, the Office of the Australian Information Commissioner (OAIC) sued Facebook, for significant and persistent infringements of the rule on privacy involving the Cambridge Analytica fiasco. Every violation of the Privacy Act is subject to a theoretical cumulative liability of $1.7 million. The OAIC estimated that a total of 311,127 Australians had been exposed. On December 8, 2020, the U.S. Federal Trade Commission and 46 states (excluding Alabama, Georgia, South Carolina, and South Dakota), the District of Columbia and the territory of Guam, launched Federal Trade Commission v. Facebook as an antitrust lawsuit against Facebook. The lawsuit concerns Facebook's acquisition of two competitors—Instagram and WhatsApp—and the ensuing monopolistic situation. FTC alleges that Facebook holds monopolistic power in the U.S. social networking market and seeks to force the company to divest from Instagram and WhatsApp to break up the conglomerate. William Kovacic, a former chairman of the Federal Trade Commission, argued the case will be difficult to win as it would require the government to create a counterfactual argument of an internet where the Facebook-WhatsApp-Instagram entity did not exist, and prove that harmed competition or consumers. In November 2025, it was ruled that Meta did not violate antitrust laws and holds no monopoly in the market. On December 24, 2021, a court in Russia fined Meta for $27 million after the company declined to remove unspecified banned content. The fine was reportedly tied to the company's annual revenue in the country. In May 2022, a lawsuit was filed in Kenya against Meta and its local outsourcing company Sama. Allegedly, Meta has poor working conditions in Kenya for workers moderating Facebook posts. According to the lawsuit, 260 screeners were declared redundant with confusing reasoning. The lawsuit seeks financial compensation and an order that outsourced moderators be given the same health benefits and pay scale as Meta employees. In June 2022, 8 lawsuits were filed across the U.S. over the allege that excessive exposure to platforms including Facebook and Instagram has led to attempted or actual suicides, eating disorders and sleeplessness, among other issues. The litigation follows a former Facebook employee's testimony in Congress that the company refused to take responsibility. The company noted that tools have been developed for parents to keep track of their children's activity on Instagram and set time limits, in addition to Meta's "Take a break" reminders. In addition, the company is providing resources specific to eating disorders as well as developing AI to prevent children under the age of 13 signing up for Facebook or Instagram. In June 2022, Meta settled a lawsuit with the US Department of Justice. The lawsuit, which was filed in 2019, alleged that the company enabled housing discrimination through targeted advertising, as it allowed homeowners and landlords to run housing ads excluding people based on sex, race, religion, and other characteristics. The U.S. Department of Justice stated that this was in violation of the Fair Housing Act. Meta was handed a penalty of $115,054 and given until December 31, 2022, to shadow the algorithm tool. In January 2023, Meta was fined €390 million for violations of the European Union General Data Protection Regulation. In May 2023, the European Data Protection Board fined Meta a record €1.2 billion for breaching European Union data privacy laws by transferring personal data of Facebook users to servers in the U.S. In July 2024, Meta agreed to pay the state of Texas US$1.4 billion to settle a lawsuit brought by Texas Attorney General Ken Paxton accusing the company of collecting users' biometric data without consent, setting a record for the largest privacy-related settlement ever obtained by a state attorney general. In October 2024, Meta Platforms faced lawsuits in Japan from 30 plaintiffs who claimed they were defrauded by fake investment ads on Facebook and Instagram, featuring false celebrity endorsements. The plaintiffs are seeking approximately $2.8 million in damages. In April 2025, the Kenyan High Court ruled that a US$2.4 billion lawsuit in which three plaintiffs claim that Facebook inflamed civil violence in Ethiopia in 2021 could proceed. In April 2025, Meta was fined €200 million ($230 million) for breaking the Digital Markets Act, by imposing a “consent or pay” system that forces users to either allow their personal data to be used to target advertisements, or pay a subscription fee for advertising-free versions of Facebook and Instagram. In late April 2025, a case was filed against Meta in Ghana over the alleged psychological distress experienced by content moderators employed to take down disturbing social media content including depictions of murders, extreme violence and child sexual abuse. Meta moved the moderation service to the Ghanaian capital of Accra after legal issues in the previous location Kenya. The new moderation company is Teleperformance, a multinational corporation with a history of worker's rights violation. Reports suggests the conditions are worse here than in the previous Kenyan location, with many workers afraid of speaking out due to fear of returning to conflict zones. Workers reported developing mental illnesses, attempted suicides, and low pay. In 26 January 2026, a New Mexico state court case was filed, suggesting that Mark Zuckerberg approved allowing minors to access artificial intelligence chatbot companions that safety staffers warned were capable of sexual interactions. In 2020, the company UReputation, which had been involved in several cases concerning the management of digital armies[clarification needed], filed a lawsuit against Facebook, accusing it of unlawfully transmitting personal data to third parties. Legal actions were initiated in Tunisia, France, and the United States. In 2025, the United States District court for the Northern District of Georgia approved a discovery procedure, allowing UReputation to access documents and evidence held by Meta. Structure Meta's key management consists of: As of October 2022[update], Meta had 83,553 employees worldwide. As of June 2024[update], Meta's board consisted of the following directors; Meta Platforms is mainly owned by institutional investors, who hold around 80% of all shares. Insiders control the majority of voting shares. The three largest individual investors in 2024 were Mark Zuckerberg, Sheryl Sandberg and Christopher K. Cox. The largest shareholders in late 2024/early 2025 were: Roger McNamee, an early Facebook investor and Zuckerberg's former mentor, said Facebook had "the most centralized decision-making structure I have ever encountered in a large company". Facebook co-founder Chris Hughes has stated that chief executive officer Mark Zuckerberg has too much power, that the company is now a monopoly, and that, as a result, it should be split into multiple smaller companies. In an op-ed in The New York Times, Hughes said he was concerned that Zuckerberg had surrounded himself with a team that did not challenge him, and that it is the U.S. government's job to hold him accountable and curb his "unchecked power". He also said that "Mark's power is unprecedented and un-American." Several U.S. politicians agreed with Hughes. European Union Commissioner for Competition Margrethe Vestager stated that splitting Facebook should be done only as "a remedy of the very last resort", and that it would not solve Facebook's underlying problems. Revenue Facebook ranked No. 34 in the 2020 Fortune 500 list of the largest United States corporations by revenue, with almost $86 billion in revenue most of it coming from advertising. One analysis of 2017 data determined that the company earned US$20.21 per user from advertising. According to New York, since its rebranding, Meta has reportedly lost $500 billion as a result of new privacy measures put in place by companies such as Apple and Google which prevents Meta from gathering users' data. In February 2015, Facebook announced it had reached two million active advertisers, with most of the gain coming from small businesses. An active advertiser was defined as an entity that had advertised on the Facebook platform in the last 28 days. In March 2016, Facebook announced it had reached three million active advertisers with more than 70% from outside the United States. Prices for advertising follow a variable pricing model based on auctioning ad placements, and potential engagement levels of the advertisement itself. Similar to other online advertising platforms like Google and Twitter, targeting of advertisements is one of the chief merits of digital advertising compared to traditional media. Marketing on Meta is employed through two methods based on the viewing habits, likes and shares, and purchasing data of the audience, namely targeted audiences and "look alike" audiences. The U.S. IRS challenged the valuation Facebook used when it transferred IP from the U.S. to Facebook Ireland (now Meta Platforms Ireland) in 2010 (which Facebook Ireland then revalued higher before charging out), as it was building its double Irish tax structure. The case is ongoing and Meta faces a potential fine of $3–5bn. The U.S. Tax Cuts and Jobs Act of 2017 changed Facebook's global tax calculations. Meta Platforms Ireland is subject to the U.S. GILTI tax of 10.5% on global intangible profits (i.e. Irish profits). On the basis that Meta Platforms Ireland Limited is paying some tax, the effective minimum US tax for Facebook Ireland will be circa 11%. In contrast, Meta Platforms Inc. would incur a special IP tax rate of 13.125% (the FDII rate) if its Irish business relocated to the U.S. Tax relief in the U.S. (21% vs. Irish at the GILTI rate) and accelerated capital expensing, would make this effective U.S. rate around 12%. The insignificance of the U.S./Irish tax difference was demonstrated when Facebook moved 1.5bn non-EU accounts to the U.S. to limit exposure to GDPR. Facilities Users outside of the U.S. and Canada contract with Meta's Irish subsidiary, Meta Platforms Ireland Limited (formerly Facebook Ireland Limited), allowing Meta to avoid US taxes for all users in Europe, Asia, Australia, Africa and South America. Meta is making use of the Double Irish arrangement which allows it to pay 2–3% corporation tax on all international revenue. In 2010, Facebook opened its fourth office, in Hyderabad, India, which houses online advertising and developer support teams and provides support to users and advertisers. In India, Meta is registered as Facebook India Online Services Pvt Ltd. It also has offices or planned sites in Chittagong, Bangladesh; Dublin, Ireland; and Austin, Texas, among other cities. Facebook opened its London headquarters in 2017 in Fitzrovia in central London. Facebook opened an office in Cambridge, Massachusetts in 2018. The offices were initially home to the "Connectivity Lab", a group focused on bringing Internet access to those who do not have access to the Internet. In April 2019, Facebook opened its Taiwan headquarters in Taipei. In March 2022, Meta opened new regional headquarters in Dubai. In September 2023, it was reported that Meta had paid £149m to British Land to break the lease on Triton Square London office. Meta reportedly had another 18 years left on its lease on the site. As of 2023, Facebook operated 21 data centers. It committed to purchase 100% renewable energy and to reduce its greenhouse gas emissions 75% by 2020. Its data center technologies include Fabric Aggregator, a distributed network system that accommodates larger regions and varied traffic patterns. Reception US Representative Alexandria Ocasio-Cortez responded in a tweet to Zuckerberg's announcement about Meta, saying: "Meta as in 'we are a cancer to democracy metastasizing into a global surveillance and propaganda machine for boosting authoritarian regimes and destroying civil society ... for profit!'" Ex-Facebook employee Frances Haugen and whistleblower behind the Facebook Papers responded to the rebranding efforts by expressing doubts about the company's ability to improve while led by Mark Zuckerberg, and urged the chief executive officer to resign. In November 2021, a video published by Inspired by Iceland went viral, in which a Zuckerberg look-alike promoted the Icelandverse, a place of "enhanced actual reality without silly looking headsets". In a December 2021 interview, SpaceX and Tesla chief executive officer Elon Musk said he could not see a compelling use-case for the VR-driven metaverse, adding: "I don't see someone strapping a frigging screen to their face all day." In January 2022, Louise Eccles of The Sunday Times logged into the metaverse with the intention of making a video guide. She wrote: Initially, my experience with the Oculus went well. I attended work meetings as an avatar and tried an exercise class set in the streets of Paris. The headset enabled me to feel the thrill of carving down mountains on a snowboard and the adrenaline rush of climbing a mountain without ropes. Yet switching to the social apps, where you mingle with strangers also using VR headsets, it was at times predatory and vile. Eccles described being sexually harassed by another user, as well as "accents from all over the world, American, Indian, English, Australian, using racist, sexist, homophobic and transphobic language". She also encountered users as young as 7 years old on the platform, despite Oculus headsets being intended for users over 13. See also References External links 37°29′06″N 122°08′54″W / 37.48500°N 122.14833°W / 37.48500; -122.14833 |
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[SOURCE: https://en.wikipedia.org/wiki/Pike_(programming_language)] | [TOKENS: 379] |
Contents Pike (programming language) Pike is an general-purpose, high-level, cross-platform, dynamic programming language, with a syntax similar to that of C. Unlike many other dynamic languages, Pike is both statically and dynamically typed, and requires explicit type definitions. It features a flexible type system that allows the rapid development and flexible code of dynamically typed languages, while still providing some of the benefits of a statically-typed language. Pike features garbage collection, advanced data types, and first-class anonymous functions, with support for many programming paradigms, including object-oriented, functional and imperative programming. Pike is free software, released under the GPL, LGPL and MPL licenses. History Pike has its roots in LPC, which was a language developed for MUDs. Programmers at Lysator in Linköping, Sweden, most notably Fredrik Hübinette and Per Hedbor, separated the language and virtual machine from the rest of the MUD driver, and used it as a rapid prototyping language for various applications, calling it LPC4. LPC's license did not allow use for commercial purposes, and so a new GPL implementation was written in 1994, called μLPC (micro LPC). In 1996, μLPC was renamed to Pike in order to provide a more commercially viable name. Although the name of the company has changed over the years, the company now known as Roxen Internet Software employed many Pike developers, and provided resources for Pike's development. Roxen is also the name of a web server developed by the company in Pike. In 2002, the programming environment laboratory at Linköping University took over maintenance of Pike from Roxen. Several Pike programmers have found their way to the Linköping office of Opera Software, where the language plays a central role in the server/gateway parts of the Opera Mini application. Example See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Lod#cite_ref-Brink_23-0] | [TOKENS: 4733] |
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 Banshee A banshee (/ˈbænʃiː/ BAN-shee; Modern Irish bean sí [bʲanˠ ˈʃiː], from Old Irish: ben síde [bʲen ˈʃiːðʲe], "woman of the fairy mound" or "fairy woman") is a female spirit in Irish folklore who heralds the death of a family member, usually by screaming, wailing, shrieking, or keening. Her name is connected to the mythologically important tumuli or "mounds" that dot the Irish countryside, which are known as síde (singular síd) in Old Irish. Description Sometimes she has long streaming hair, which she may be seen combing, with some legends specifying she can only keen while combing her hair. She wears a grey cloak over a green dress, and her eyes are red from continual weeping. She may be dressed in white with red hair and a ghastly complexion, according to a firsthand account by Ann, Lady Fanshawe in her Memoirs. Lady Wilde in her books provides others: The size of the banshee is another physical feature that differs between regional accounts. Though some accounts of her standing unnaturally tall are recorded, the majority of tales that describe her height state the banshee's stature as short, anywhere between one foot and four feet. Her exceptional shortness often goes alongside the description of her as an old woman, though it may also be intended to emphasize her state as a fairy creature. Sometimes the banshee assumes the form of some sweet-singing virgin of the family who died young, and has been given the mission by the invisible powers to become the harbinger of coming doom to her mortal kindred. Or she may be seen at night as a shrouded woman, crouched beneath the trees, lamenting with a veiled face; or flying past in the moonlight, crying bitterly: and the cry of this spirit is mournful beyond all other sounds on earth, and betokens certain death to some member of the family whenever it is heard in the silence of the night. In John O'Brien's Irish-English dictionary, the entry for Síth-Bhróg states: "hence bean-síghe, plural mná-síghe, she-fairies or women-fairies, credulously supposed by the common people to be so affected to certain families that they are heard to sing mournful lamentations about their houses by night, whenever any of the family labours under a sickness which is to end by death, but no families which are not of an ancient & noble Stock, are believed to be honoured with this fairy privilege". Keening In Ireland and parts of Scotland, a traditional part of mourning is the keening woman (bean chaointe), who wails a lament —in Irish: caoineadh ('weeping'), pronounced [ˈkɯiːnʲə] in the Irish dialects of Munster and southern County Galway, [ˈkɯiːnʲuː] in Connacht (except south Galway) and (particularly west) Ulster, and [ˈkɯːnʲuw] in Ulster, particularly in the traditional dialects of north and east Ulster, including County Louth. This keening woman may in some cases be a professional, and the best keeners would be in high demand. Irish legend speaks of a lament being sung by a fairy woman, or banshee. She would sing it when a family member died or was about to die, even if the person had died far away and news of their death had not yet come. In those cases, her wailing would be the first warning the household had of the death. The banshee is also a predictor of death. If someone is about to enter a situation where it is unlikely they will come out alive she will warn people by screaming or wailing, giving rise to a banshee also being known as a wailing woman. The banshee was also associated with the death coach, being said to either summon it with her keening or to travel in tandem with it. When several banshees appear at once, it indicates the death of someone great or holy. The tales sometimes recounted that the woman, though called a fairy, was a ghost, often of a specific murdered woman, or a mother who died in childbirth. In some parts of Leinster, she is referred to as the bean chaointe ('keening woman') whose wail can be so piercing that it shatters glass. In Scottish folklore, a similar creature is known as the bean nighe or ban nigheachain ('little washerwoman') or nigheag na h-àth ('little washer at the ford') and is seen washing the bloodstained clothes or armour of those who are about to die. In Welsh folklore, a similar creature is known as the cyhyraeth. Accounts reach as far back as 1380 to the publication of the Cathreim Thoirdhealbhaigh (Triumphs of Torlough) by Sean mac Craith. Mentions of banshees can also be found in Norman literature of that time. Associated families Some sources suggest that the banshee laments only the descendants of the "pure Milesian stock" of Ireland, with the original belief appearing to associate the folklore with a number of ancient Irish families. According to this tradition, a banshee would not lament or visit someone of Saxon or Norman descent or who came to Ireland later. Most, but not all, surnames associated with banshees have the Ó or Mc/Mac prefix – that is, surnames of Goidelic origin, indicating a family native to the Insular Celtic lands rather than those of the Norse, Anglo-Saxon, or Norman. There are some exceptions to this lore, including that a banshee may lament a person who had been "gifted with music and song". For example, there are accounts of the Geraldines hearing a banshee – as they had reputedly become "more Irish than the Irish themselves" – and that the Bunworth Banshee, associated with the Rev. Charles Bunworth (a name of Anglo-Saxon origin), heralded the death of an Irish person who had been a patron to musicians. According to tradition, some families had their own banshee, with the Ua Briain banshee, named Aibell, being the ruler of 25 other banshees who would always be at her attendance. See also References Further reading External links |
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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/Presidency_of_George_W._Bush] | [TOKENS: 12792] |
Contents Presidency of George W. Bush George W. Bush's tenure as the 43rd president of the United States began with his first inauguration on January 20, 2001, and ended on January 20, 2009. Bush, a Republican from Texas, took office after defeating the Democratic incumbent vice president Al Gore in the 2000 presidential election. Four years later, he won re-election in the 2004 presidential election, after defeating the Democratic nominee John Kerry. Alongside Bush's presidency, the Republican Party also held their majorities in the House of Representatives and the Senate during the 108th and 109th U.S. Congresses following the 2002 and 2004 elections, thereby attained an overall federal government trifecta. Bush was constitutionally limited to two terms and was succeeded by Democrat Barack Obama, who won the 2008 presidential election against Bush's preferred succcessor, John McCain. He is the eldest son of the 41st president, George H. W. Bush. A decisive event reshaping Bush's administration were the terrorist attacks on September 11, 2001. In its aftermath, Congress created the Department of Homeland Security and Bush declared a global war on terrorism. He ordered an invasion of Afghanistan in an effort to overthrow the Taliban, destroy al-Qaeda, and capture Osama bin Laden. He also signed the controversial Patriot Act in order to authorize surveillance of suspected terrorists. In 2003, Bush ordered an invasion of Iraq, alleging that the Saddam Hussein regime possessed weapons of mass destruction. Intense criticism came when neither WMD stockpiles nor evidence of an operational relationship with al-Qaeda were found. Before 9/11, Bush had pushed through a $1.3 trillion tax cut program and the No Child Left Behind Act, a major education bill. He also pushed for socially conservative efforts, such as the Partial-Birth Abortion Ban Act and faith-based welfare initiatives. Also in 2003, he signed the Medicare Prescription Drug, Improvement, and Modernization Act, which created Medicare Part D. In economic terms, Bush's legacy is mixed, with GDP growth running at 2.3% annualised from the start of 2001 to the third quarter of 2008. This was 1.4% below the rate under Bill Clinton, and notably weaker than the 3.3% average since 1953. The average hourly wage for households only grew by 1.1% adjusted for inflation compared to 6.7% under Clinton. From January 2001 to October 2008, 4,414,000 jobs were created. However, productivity posted the best average annual growth since Lyndon B. Johnson's tenure and corporate profits grew 9.4% in current dollars, the best advance since Reagan. During his second term, Bush reached multiple free trade agreements and successfully nominated John Roberts and Samuel Alito to the Supreme Court. He sought major changes to Social Security and immigration laws, but both efforts failed. The wars in Afghanistan and Iraq continued, and in 2007 he launched a surge of troops in Iraq. The Bush administration's response to Hurricane Katrina and the dismissal of U.S. attorneys controversy came under attack, with a drop in his approval ratings. The 2008 financial crisis dominated his last days in office as policymakers looked to avert a major economic disaster, and he established the Troubled Asset Relief Program (TARP) to buy toxic assets from financial institutions. At various points in his presidency, Bush was among both the most popular and unpopular presidents in U.S. history. He received the highest recorded approval ratings in the wake of the September 11 attacks, but also one of the lowest such ratings during the Iraq War and the 2008 financial crisis. Although public sentiment of Bush has improved since he left office, scholars ranked his presidency as below-average. 2000 election The oldest son of George H. W. Bush, the 41st president of the United States, George W. Bush emerged as a presidential contender in his own right with his victory in the 1994 Texas gubernatorial election. After winning re-election by a decisive margin in the 1998 Texas gubernatorial election, Bush became the widely acknowledged front-runner in the race for the Republican nomination in the 2000 presidential election. In the years preceding the 2000 election, Bush established a stable of advisers, including supply-side economics advocate Lawrence B. Lindsey and foreign policy expert Condoleezza Rice. With a financial team led by Karl Rove and Ken Mehlman, Bush built up a commanding financial advantage over other prospective Republican candidates. Though several prominent Republicans declined to challenge Bush, Arizona senator John McCain launched a spirited challenge that was supported by many moderates and foreign policy hawks. McCain's loss in the South Carolina primary effectively ended the 2000 Republican primaries, and Bush was officially nominated for president at the 2000 Republican National Convention. Bush selected former secretary of defense Dick Cheney as his running mate; though Cheney offered little electoral appeal and had health problems, Bush believed that Cheney's extensive experience would make him a valuable governing partner. With Democratic President Bill Clinton term-limited, the Democrats nominated Vice President Al Gore of Tennessee for president and Senator Joe Lieberman of Connecticut for vice president. Bush's campaign emphasized their own candidate's character in contrast with that of Clinton, who had been embroiled in the Lewinsky scandal. Bush held a substantial lead in several polls taken after the final debate in October, but the unearthing of Bush's 1976 DUI arrest appeared to sap his campaign's momentum. By the end of election night, Florida emerged as the key state in the election, as whichever candidate won the state would win the presidency. Bush held an extremely narrow lead in the vote by the end of election night, triggering an automatic recount. The Florida Supreme Court ordered a partial manual recount, but the United States Supreme Court effectively ordered an end to this process, on equal protection grounds, in the case of Bush v. Gore, leaving Bush with a victory in both the state and the election. Bush won the presidential election with 271 electoral votes and 47.9% of the popular votes, while Al Gore received 266 electoral votes and 48.4% of the popular vote.[a] Bush thus became the fourth person to win the presidency while losing the popular vote. In the concurrent congressional elections, Republicans briefly secured a government trifecta after retaining their majorities in the House of Representatives and the Senate, leaving the partisan balance in the Senate at 50 Republicans and 50 Democrats, with vice president Dick Cheney's tie-breaking vote giving Republicans control of the chamber. Administration Rejecting the idea of a powerful White House chief of staff, Bush had high-level officials report directly to him rather than Chief of Staff Andrew Card. Vice President Cheney emerged as the most powerful individual in the White House aside from Bush himself. Bush brought to the White House several individuals who had worked under him in Texas, including Senior Counselor Karen Hughes, Senior Adviser Karl Rove, legal counsel Alberto Gonzales, and Staff Secretary Harriet Miers. Other important White House staff appointees included Margaret Spellings as a domestic policy adviser, Michael Gerson as chief speechwriter, and Joshua Bolten and Joe Hagin as White House deputy chiefs of staff. Paul H. O'Neill, who had served as deputy director of the OMB under Gerald Ford, was appointed secretary of the treasury, while former Missouri senator John Ashcroft was appointed attorney general. As Bush had little foreign policy experience, his appointments would serve an important role in shaping U.S. foreign policy during his tenure. Several of his initial top foreign policy appointees had served in his father's administration; Vice President Cheney had been secretary of defense, National Security Adviser Condoleezza Rice had served on the National Security Council, and deputy secretaries Paul Wolfowitz and Richard Armitage had also served in important roles. Secretary of State Colin Powell had served as chairman of the Joint Chiefs of Staff under the first president Bush. Bush had long admired Powell, and the former general was Bush's first choice for the position. Secretary of Defense Donald Rumsfeld, who had served in the same position during the Ford administration, rounded out the key figures in the national security team. Rumsfeld and Cheney, who had served together in the Ford administration, emerged as the leading foreign policy figures during Bush's first term. O'Neill, who opposed the Iraq War and feared that the Bush tax cuts would lead to deficits, was replaced by John W. Snow in February 2003. Frustrated by the decisions of the Bush administration, particularly the launching of the Iraq War, Powell resigned following the 2004 elections. He was replaced by Rice, while then-deputy national security adviser Stephen Hadley took Rice's former position. Most of Bush's top staffers stayed on after the 2004 election, although Spellings joined the Cabinet as secretary of education and Gonzales replaced Ashcroft as attorney general. In early 2006, Card left the White House in the wake of the Dubai Ports World controversy and several botched White House initiatives, and he was replaced by Joshua Bolten. Bolten stripped Rove of some of his responsibilities and convinced Henry Paulson, the head of Goldman Sachs, to replace Snow as secretary of the treasury. After the 2006 elections, Rumsfeld was replaced by former CIA director Robert Gates. The personnel shake-ups left Rice as one of the most prominent individuals in the administration, and she played a strong role in directing Bush's second term foreign policy. Gonzales and Rove both left in 2007 after controversy regarding the dismissal of U.S. attorneys, and Gonzales was replaced by Michael Mukasey, a former federal judge. Judicial appointments After the 2004 election, many expected that the aging Chief Justice William Rehnquist would step down from the United States Supreme Court. Cheney and White House Counsel Harriet Miers selected two widely respected conservatives, D.C. Circuit Court of Appeals judge John Roberts and Fourth Circuit judge Michael Luttig, as the two finalists. In June 2005, Justice Sandra Day O'Connor unexpectedly announced that she would retire from the court, and Bush nominated Roberts for her position the following month. After Rehnquist died in September, Bush briefly considered elevating Associate Justice Antonin Scalia to the position of chief justice, but instead chose to nominate Roberts for the position. Roberts won confirmation from the Senate in a 78–22 vote, with all Republicans and a narrow majority of Democrats voting to confirm Roberts. To replace O'Connor, the Bush administration wanted to find a female nominee, but was unsatisfied with the conventional options available. Bush settled on Miers, who had never served as a judge, but who had worked as a corporate lawyer and White House staffer. Her nomination immediately faced opposition from conservatives (and liberals) who were wary of her unproven ideology and lack of judicial experience. After Senate Majority Leader Bill Frist informed Bush that Miers did not have the votes necessary to win confirmation, Miers withdrew from consideration. Bush then nominated Samuel Alito, who received strong support from conservatives but faced opposition from Democrats. Alito won confirmation in a 58–42 vote in January 2006. In the years immediately after Roberts and Alito took office, the Roberts Court was generally more conservative than the preceding Rehnquist Court, largely because Alito tended to be more conservative than O'Connor had been. Bush also appointed 62 judges to the United States Courts of Appeals, 261 judges to the United States district courts, and 2 judges to the United States Court of International Trade. Among them were two future Supreme Court associate justices: Neil Gorsuch to a seat on the Court of Appeals for the Tenth Circuit in 2006, and Brett Kavanaugh to the Court of Appeals District of Columbia Circuit in 2006. Domestic affairs Bush's promise to cut taxes was the centerpiece of his 2000 presidential campaign, and upon taking office, he made tax cuts his first major legislative priority. A budget surplus had developed during the Bill Clinton administration, and with the Federal Reserve chairman Alan Greenspan's support, Bush argued that the best use of the surplus was to lower taxes. By the time Bush took office, reduced economic growth had led to less robust federal budgetary projections, but Bush maintained that tax cuts were necessary to boost economic growth. After Treasury secretary Paul O'Neill expressed concerns over the tax cut's size and the possibility of future deficits, Vice President Cheney took charge of writing the bill, which the administration proposed to Congress in March 2001. Bush initially sought a $1.6 trillion tax cut over a ten-year period, but ultimately settled for a $1.35 trillion tax cut. The administration rejected the idea of "triggers" that would phase out the tax reductions should the government again run deficits. The Economic Growth and Tax Relief Reconciliation Act of 2001 won the support of congressional Republicans and a minority of congressional Democrats, and Bush signed it into law in June 2001. The act lowered the top income tax rate from 39 percent to 35 percent, and it also reduced the estate tax. The narrow Republican majority in the Senate necessitated the use of the reconciliation, which in turn necessitated that the tax cuts would phase out in 2011 barring further legislative action. After the tax bill was passed, Senator Jim Jeffords left the Republican Party and began caucusing with the Democrats, giving them control of the Senate. After Republicans re-took control of the Senate during the 2002 mid-term elections, Bush proposed further tax cuts. With little support among Democrats, Congress passed the Jobs and Growth Tax Relief Reconciliation Act of 2003, which cut taxes by another $350 billion over 10 years. That law also lowered the capital gains tax and taxes on dividends. Collectively, the Bush tax cuts reduced federal individual tax rates to their lowest level since World War II, and government revenue as a share of gross domestic product declined from 20.9% in 2000 to 16.3% in 2004. Most of the Bush tax cuts were later made permanent by the American Taxpayer Relief Act of 2012, though that act rolled back the tax cuts on top earners. Contrary to the rhetoric of the Bush administration and Republicans, the budget deficit increased, leaving many to believe the tax cuts were at fault. Statements by President Bush, Vice President Dick Cheney, and Senate Majority Leader Bill Frist that these tax cuts effectively "paid for themselves" were disputed by the CBPP, the U.S. Treasury Department and the CBO. Aside from tax cuts, Bush's other major policy initiative upon taking office was education reform. Bush had a strong personal interest in reforming education, especially regarding the education of low-income and minority groups. He often derided the "soft bigotry of low expectations" for allowing low-income and minority groups to fall behind. Although many conservatives were reluctant to increase federal involvement in education, Bush's success in campaigning on education reform in the 2000 election convinced many Republicans, including Congressman John Boehner of Ohio, to accept an education reform bill that increased federal funding. Seeking to craft a bipartisan bill, Bush courted Democratic senator Ted Kennedy, a leading liberal senator who served as the ranking member on the Senate Committee on Health, Education, and Pensions. Bush favored extensive testing to ensure that schools met uniform standards for skills such as reading and math. Bush hoped that testing would make schools more accountable for their performances and provide parents with more information in choosing which schools to send their children. Kennedy shared Bush's concern for the education of impoverished children, but he strongly opposed the president's proposed school vouchers, which would allow parents to use federal funding to pay for private schools. Both men cooperated to pass the No Child Left Behind Act, which dropped the concept of school vouchers but included Bush's idea of nationwide testing. Both houses of Congress registered overwhelming approval for the bill's final version, which Bush signed into law in January 2002. However, Kennedy would later criticize the implementation of the act, arguing that Bush had promised greater federal funding for education. Shortly after the September 11 attacks, Bush announced the creation of the Office of Homeland Security and appointed former governor of Pennsylvania Tom Ridge its director. After Congress passed the Homeland Security Act to create the Department of Homeland Security (DHS), Ridge became the first director of the newly created department. The department was charged with overseeing immigration, border control, customs, and the newly established Transportation Security Administration (TSA), which focused on airport security. Though the FBI and CIA remained independent agencies, the DHS was assigned jurisdiction over the Coast Guard, the Immigration and Naturalization Service (which was divided into three agencies), the United States Customs Service (which was also divided into separate agencies), and the Federal Emergency Management Agency. The Homeland Security Act represented the most significant departmental reorganization since the National Security Act of 1947. On October 26, 2001, Bush signed into law the Patriot Act. Passed on the president's request, the act permitted increased sharing of intelligence among the U.S. Intelligence Community and expanded the government's domestic authority to conduct surveillance of suspected terrorists. The Patriot Act also authorized the use of roving wiretaps on suspected terrorists and expanded the government's authority to conduct surveillance of suspected "lone wolf" terrorists. Bush also secretly authorized the National Security Agency to conduct warrantless surveillance of communications in and out of the United States. McCain's 2000 presidential campaign brought the issue of campaign finance reform to the fore of public consciousness in 2001. McCain and Russ Feingold pushed a bipartisan campaign finance bill in the Senate, while Chris Shays (R-CT) and Marty Meehan (D-MA) led the effort of passing it in the House. In just the second successful use of the discharge petition since the 1980s, a mixture of Democrats and Republicans defied Speaker Dennis Hastert and passed a campaign finance reform bill. The House approved the bill with a 240–189 vote, while the bill passed the Senate in a 60–40 vote, the bare minimum required to overcome the filibuster. Throughout the congressional battle on the bill, Bush declined to take a strong position. However, in March 2002, Bush signed into law the Bipartisan Campaign Reform Act, stating that he thought the law would improve the financing system for elections but was "far from perfect." The law placed several limits on political donations and expenditures, and closed loopholes on contribution limits on donations to political candidates by banning the use of so-called "soft money." Portions of the law restricting independent expenditures would later be struck down by the Supreme Court in the 2010 case of Citizens United v. FEC. After the passage of the Bush tax cuts and the No Child Left Behind Act, Bush turned his domestic focus to healthcare. He sought to expand Medicare so it would also cover the cost of prescription drugs, a program that became known as Medicare Part D. Many congressional Democrats opposed the bill because it did not allow Medicare to negotiate the prices of drugs, while many conservative Republicans opposed the expansion of the government's involvement in healthcare. Assisted by Speaker of the House Dennis Hastert and Senate majority leader Bill Frist, Bush overcame strong opposition and won passage of his Medicare bill. In December 2003, Bush signed the Medicare Prescription Drug, Improvement, and Modernization Act, the largest expansion of Medicare since the program's creation in 1965. After winning re-election in 2004, Bush made the partial privatization of Social Security his top domestic priority. He proposed restructuring the program so that citizens could invest some of the money they paid in payroll taxes, which fund the Social Security program. The president argued that Social Security faced an imminent funding crisis and that reform was necessary to ensure its continuing solvency. Bush expected a difficult congressional battle over his proposal, but, as he put it, "I've got political capital, and I intend to spend it." Groups like the AARP strongly opposed the plan, as did moderate Democrats like Max Baucus, who had supported the Bush tax cuts. Ultimately, Bush failed to win the backing of a single congressional Democrat for his plan, and even moderate Republicans like Olympia Snowe and Lincoln Chafee refused to back privatization. In the face of unified opposition, Republicans abandoned Bush's Social Security proposal in mid-2005. Hurricane Katrina, one of the largest and most powerful hurricanes ever to strike the United States, ravaged several states along the Gulf of Mexico in August 2005. On a working vacation at his ranch in Texas, Bush initially allowed state and local authorities to respond to the natural disaster. The hurricane made landfall on August 29, devastating the city of New Orleans after the failure of that city's levees. Over eighteen hundred people died in the hurricane, and Bush was widely criticized for his slow response to the disaster. Stung by the public response, Bush removed Federal Emergency Management Agency director Michael D. Brown from office and stated publicly that "Katrina exposed serious problems in our response capability at all levels of government." After Hurricane Katrina, Bush's approval rating fell below 40 percent, where it would remain for the rest of his tenure in office. Although he concentrated on other domestic policies during his first term, Bush supported immigration reform throughout his administration. In May 2006, he proposed a five-point plan that would increase border security, establish a guest worker program, and create a path to citizenship for the twelve million illegal immigrants living in the United States. The Senate passed the Comprehensive Immigration Reform Act of 2006, which included many of the president's proposals, but the bill did not pass the House of Representatives. After Democrats took control of Congress in the 2006 mid-term elections, Bush worked with Ted Kennedy to re-introduce the bill as the Comprehensive Immigration Reform Act of 2007. The bill received intense criticism from many conservatives, who had become more skeptical of immigration reform, and it failed to pass the Senate. After years of financial deregulation accelerating under the Bush administration, banks lent subprime mortgages to more and more home buyers, causing a housing bubble. Many of these banks also invested in credit default swaps and derivatives that were essentially bets on the soundness of these loans. In response to declining housing prices and fears of an impending recession, the Bush administration arranged passage of the Economic Stimulus Act of 2008. Falling home prices started threatening the financial viability of many institutions, leaving Bear Stearns, a prominent U.S.-based investment bank, on the brink of failure in March 2008. Recognizing the growing threat of a financial crisis, Bush allowed Treasury secretary Paulson to arrange for another bank, JPMorgan Chase, to take over most Bear Stearn's assets. Out of concern that Fannie Mae and Freddie Mac might also fail, the Bush administration put both institutions into conservatorship. Shortly afterwards, the administration learned that Lehman Brothers was on the verge of bankruptcy, but the administration ultimately declined to intervene on behalf of Lehman Brothers. Paulson hoped that the financial industry had shored itself up after the failure of Bear Stearns and that the failure of Lehman Brothers would not strongly impact the economy, but news of the failure caused stock prices to tumble and froze credit. Fearing a total financial collapse, Paulson and the Federal Reserve took control of American International Group (AIG), another major financial institution that teetered on the brink of failure. Hoping to shore up the other banks, Bush and Paulson proposed the Emergency Economic Stabilization Act of 2008, which would create the $700 billion Troubled Asset Relief Program (TARP) to buy toxic assets. The House rejected TARP in a 228–205 vote; although support and opposition crossed party lines, only about one-third of the Republican caucus supported the bill. After the Dow Jones Industrial Average dropped 778 points on the day of the House vote, the House and Senate both passed TARP. Bush later extended TARP loans to U.S. automobile companies, which faced the 2008–2010 automotive industry crisis due to the weak economy. Though TARP helped end the financial crisis, it did not prevent the onset of the Great Recession, which would continue after Bush left office. On his first day in office, President Bush reinstated the Mexico City policy, thereby blocking federal aid to foreign groups that offered assistance to women in obtaining abortions. Days later, he announced his commitment to channeling more federal aid to faith-based service organizations, despite the fears of critics that this would dissolve the traditional separation of church and state in the United States. To further this commitment, he created the White House Office of Faith-Based and Community Initiatives to assist faith-based service organizations. In 2003, Bush signed the Partial-Birth Abortion Ban Act, which banned intact dilation and extraction, an abortion procedure. Early in his administration, President Bush became personally interested in the issue of stem cell research. The Clinton administration had issued guidelines allowing the federal funding of research utilizing stem cells, and Bush decided to study the situation's ethics before issuing his own executive order on the issue. Evangelical religious groups argued that the research was immoral as it destroyed human embryos, while various advocacy groups touted the potential scientific advances afforded by stem cell research. In August 2001, Bush issued an executive order banning federal funding for research on new stem cell lines; the order allowed research on existing stem cell lines to continue. In July 2006, Bush used his first presidential veto on the Stem Cell Research Enhancement Act, which would have expanded federal funding of embryonic stem cell research. A similar bill was passed in both the House of Representatives and the Senate early in mid-2007 as part of House Speaker Nancy Pelosi's 100-Hour Plan, but was vetoed by Bush. After the Supreme Court struck down a state sodomy law in the 2003 case of Lawrence v. Texas, conservatives began pushing for the Federal Marriage Amendment, which would define marriage as a union between a man and a woman. Bush endorsed this proposal and made it part of his campaign during the 2004 and 2006 election cycles. However, President Bush did break from his party in his tolerance of civil unions for homosexual couples. Bush was staunchly opposed to euthanasia and supported Attorney General John Ashcroft's ultimately unsuccessful suit against the Oregon Death with Dignity Act. However, while he was governor of Texas, Bush had signed a law giving hospitals the authority to remove life support from terminally ill patients against the wishes of spouses or parents, if the doctors deemed it as medically appropriate. This perceived inconsistency in policy became an issue in 2005, when Bush signed controversial legislation to initiate federal intervention in the court battle of Terri Schiavo, a comatose Florida woman who ultimately died. In March 2001, the Bush administration announced that it would not implement the Kyoto Protocol, an international treaty signed in 1997 that required nations to reduce their greenhouse gas emissions. The administration argued that ratifying the treaty would unduly restrict U.S. growth while failing to adequately limit emissions from developing nations. The administration questioned the scientific consensus on climate change. Bush stated that he believed global warming is real and a serious problem, although he asserted that there existed a "debate over whether it's man-made or naturally caused". The Bush administration's stance on global warming remained controversial in the scientific and environmental communities. Critics alleged that the administration misinformed the public and did not do enough to reduce carbon emissions and deter global warming. On January 6, 2009, President Bush designated the world's largest protected marine area. The Pacific Ocean habitat includes the Mariana Trench and the waters and corals surrounding three uninhabited islands in the Northern Mariana Islands, Rose Atoll in American Samoa, and seven islands along the equator. In July 2002, following several accounting scandals such as the Enron scandal, Bush signed the Sarbanes–Oxley Act into law. The act expanded reporting requirements for public companies Shortly after the start of his second term, Bush signed the Class Action Fairness Act of 2005, which had been a priority of his administration and part of his broader goal of instituting tort reform. The act was designed to remove most class action lawsuits from state courts to federal courts, which were regarded as less sympathetic to plaintiffs in class action suits. Bush endorsed civil rights and appointed blacks, women and gays to high positions. The premier cabinet position, Secretary of State, went to Colin Powell (2001–2005), the first Black appointee at that high a level. He was followed by Condoleezza Rice (2005–2009), the first Black woman. Attorney General Alberto Gonzales (2005–2007) was and remains in 2024 the highest appointed Hispanic in the history of American government. In addition Bush appointed the first senior officials who were publicly gay. However he campaigned against quotas, and warned that affirmative action that involved quotas were unacceptable. He deliberately selected minorities known as opponents of affirmative action for key civil rights positions. Thus in 2001 Bush nominated Linda Chavez to be the first Latina in the cabinet as Secretary of Labor. She had to withdraw when it was reported that a decade earlier she had hired an illegal immigrant. Foreign affairs Upon taking office, Bush had little experience with foreign policy, and his decisions were guided by his advisers. Bush embraced the views of Cheney and other neoconservatives, who de-emphasized the importance of multilateralism; neoconservatives believed that because the United States was the world's lone superpower, it could act unilaterally if necessary. At the same time, Bush sought to enact the less interventionist foreign policy he had promised during the 2000 campaign. Though the first several months of his presidency focused on domestic issues, the Bush administration pulled the U.S. out of several existing or proposed multilateral agreements, including the Kyoto Protocol, the Anti-Ballistic Missile Treaty, and the International Criminal Court. Terrorism had emerged as an important national security issue in the Clinton administration, and it became one of the dominant issues of the Bush administration. In the late 1980s, Osama bin Laden had established al-Qaeda, a militant Sunni Islamist multi-national organization that sought to overthrow Western-backed governments in Saudi Arabia, Jordan, Egypt, and Pakistan. In response to Saudi Arabia's decision to begin hosting U.S. soldiers in 1991, al-Qaeda had begun a terrorist campaign against U.S. targets, orchestrating attacks such as the 1998 United States embassy bombings and the 2000 USS Cole bombing. During Bush's first months in office, U.S. intelligence organizations intercepted communications indicating that al-Qaeda was planning another attack on the United States, but foreign policy officials were unprepared for a major attack on the United States. Bush was briefed on al-Qaeda's activities, but focused on other foreign policy issues during his first months in office. On September 11, 2001, al-Qaeda terrorists hijacked four airliners and flew two of them into the twin towers of the World Trade Center in New York City, destroying both 110-story skyscrapers. A third plane crashed into Pentagon, and a fourth plane was brought down in Pennsylvania following a struggle between the terrorists and the aircraft's passengers. The attacks had a profound effect on many Americans, who felt vulnerable to international attacks for the first time since the end of the Cold War. Appearing on national television on the night of the attacks, Bush promised to punish those who had aided the attacks, stating, "we will make no distinction between the terrorists who committed these acts and those who harbor them." In the following days, Bush urged the public to renounce hate crimes and discrimination against Muslim-Americans and Arab-Americans. He also declared a "war on terror", instituting new domestic and foreign policies in an effort to prevent future terrorist attacks. As Bush's top foreign policy advisers were in agreement that merely launching strikes against al-Qaeda bases would not stop future attacks, the administration decided to overthrow Afghanistan's conservative Taliban government, which harbored the leaders of al-Qaeda. Powell took the lead in assembling allied nations in a coalition that would launch attacks on multiple fronts. The Bush administration focused especially on courting Pakistani leader Pervez Musharraf, who agreed to join the coalition. On September 14, Congress passed a resolution called the Authorization for Use of Military Force Against Terrorists, authorizing the president to use the military against those responsible for the attacks. On October 7, 2001, Bush ordered the invasion of Afghanistan. General Tommy Franks, the commander of the United States Central Command (CENTCOM), drew up a four-phase invasion plan. In the first phase, the U.S. built up forces in the surrounding area and inserted CIA and special forces operatives who linked up with the Northern Alliance, an Afghan resistance group opposed to the Taliban. The second phase consisted of a major air campaign against Taliban and al-Qaeda targets, while the third phase involved the defeat of the remaining Taliban and al-Qaeda forces. The fourth and final phase consisted of the stabilization of Afghanistan, which Franks projected would take three to five years. The war in Afghanistan began on October 7 with several air and missile strikes, and the Northern Alliance began its offensive on October 19. The capital of Kabul was captured on November 13, and Hamid Karzai was inaugurated as the new president of Afghanistan. However, the senior leadership of the Taliban and al-Qaeda, including bin Laden, avoided capture. Karzai would remain in power for the duration of Bush's presidency, but his effective control was limited to the area around Kabul, as various warlords took control of much of the rest of the country. While the Karzai's government struggled to control the countryside, the Taliban regrouped in neighboring Pakistan. As Bush left office, he considered sending additional troops to bolster Afghanistan against the Taliban, but decided to leave the issue for the next administration. After the September 11 attacks, Bush's approval ratings increased tremendously. Inspired in part by the Truman administration, Bush decided to use his newfound political capital to fundamentally change U.S. foreign policy. He became increasingly focused on the possibility of a hostile country providing weapons of mass destruction (WMDs) to terrorist organizations. During his early 2002 State of the Union Address, Bush set forth what has become known as the Bush Doctrine, which held that the United States would implement a policy of preemptive military strikes against nations known to be harboring or aiding a terrorist organization hostile to the United States. Bush outlined what he called the "Axis of Evil," consisting of three nations that, he argued, posed the greatest threat to world peace due to their pursuit of weapons of mass destruction and potential to aid terrorists. The axis consisted of Iraq, North Korea and Iran. Bush also began emphasizing the importance of spreading democracy worldwide, stating in 2005 that "the survival of liberty in our land depends on the success of liberty in other land." Pursuant to this newly interventionist policy, the Bush administration boosted foreign aid and increased defense expenditures. Defense spending rose from $304 billion in fiscal year 2001 to $616 billion in fiscal year 2008. During the presidency of his father, the United States had launched the Gulf War against Iraq after the latter invaded Kuwait. Though the U.S. forced Iraq's withdrawal from Kuwait, it left Saddam Hussein's administration in place, partly to serve as a counterweight to Iran. After the war, the Project for the New American Century, consisting of influential neoconservatives like Paul Wolfowitz and Cheney, advocated for the overthrow of Hussein. Iraq had developed biological and chemical weapons prior to the Gulf War; after the war, it had submitted to WMD inspections conducted by the United Nations Special Commission until 1998, when Hussein demanded that all UN inspectors leave Iraq. The administration believed that, by 2001, Iraq was developing weapons of mass destruction, and could possibly provide those weapons to terrorists. Some within the administration also believed that Iraq shared some responsibility for the September 11 attacks, and hoped that the fall of Hussein's regime would help spread democracy in the Middle East, deter the recruitment of terrorists, and increase the security of Israel. In the days following the September 11 attacks, hawks in the Bush administration such as Wolfowitz argued for immediate military action against Iraq, but the issue was temporarily set aside in favor of planning the invasion of Afghanistan. Beginning in September 2002, the Bush administration mounted a campaign designed to win popular and congressional support for the invasion of Iraq. In October 2002, Congress approved the Iraq Resolution, authorizing the use of force against Iraq. While congressional Republicans almost unanimously supported the measure, congressional Democrats were split in roughly equal numbers between support and opposition to the resolution. Bowing to domestic and foreign pressure, Bush sought to win the approval of the United Nations before launching an attack on Iraq. Led by Powell, the administration won the November 2002 passage of United Nations Security Council Resolution 1441, which called on Iraq to dismantle its WMD program. Meanwhile, senior administration officials became increasingly convinced that Iraq did indeed possess WMDs and was likely to furnish those WMDs to al-Qaeda; CIA Director George Tenet assured Bush that it was a "slam dunk" that Iraq possessed a stockpile of WMDs. After a U.N. weapons inspections team led by Hans Blix, as well as another team led by Mohamed ElBaradei, failed to find evidence of an ongoing Iraqi WMD program, Bush's proposed regime change in Iraq faced mounting international opposition. Germany, China, France, and Russia all expressed skepticism about the need for regime change, and the latter three countries each possessed veto power on the United Nations Security Council. At the behest of British prime minister Tony Blair, who supported Bush but hoped for more international cooperation, Bush dispatched Powell to the U.N. to make the case to the Security Council that Iraq maintained an active WMD program. Though Powell's presentation preceded a shift in U.S. public opinion towards support of the war, it failed to convince the French, Russians, or Germans. Contrary to the findings of Blix and ElBaradei, Bush asserted in a March 17 public address that there was "no doubt" that the Iraqi regime possessed weapons of mass destruction. Two days later, Bush authorized Operation Iraqi Freedom, and the Iraq War began on March 20, 2003. U.S.-led coalition forces, led by General Franks, launched a simultaneous air and land attack on Iraq on March 20, 2003, in what the American media called "shock and awe." With 145,000 soldiers, the ground force quickly overcame most Iraqi resistance, and thousands of Iraqi soldiers deserted. The U.S. captured the Iraqi capital of Baghdad on April 9, but Hussein escaped and went into hiding. While the U.S. and its allies quickly achieved military success, the invasion was strongly criticized by many countries; UN secretary-general Kofi Annan argued that the invasion was a violation of international law and the U.N. Charter. On May 1, 2003, Bush delivered the "Mission Accomplished speech," in which he declared the end of "major combat operations" in Iraq. Despite the failure to find evidence of an ongoing WMD program[b] or an operational relationship between Hussein and al-Qaeda, Bush declared that the toppling of Hussein "removed an ally of al-Qaeda" and ended the threat that Iraq would supply weapons of mass destruction to terrorist organizations. Believing that only a minimal residual American force would be required after the success of the invasion, Bush and Franks planned for a drawdown to 30,000 U.S. troops in Iraq by August 2003. Meanwhile, Iraqis began looting their own capital, presenting one of the first of many challenges the U.S. would face in keeping the peace in Iraq. Bush appointed Paul Bremer to lead the Coalition Provisional Authority (CPA), which was charged with overseeing the transition to self-government in Iraq. In his first major order, Bremer announced a policy of de-Ba'athification, which denied government and military jobs to members of Hussein's Ba'ath Party. This policy angered many of Iraq's Sunnis, many of whom had joined the Ba'ath Party merely as a career move. Bremer's second major order disbanded the Iraqi military and police services, leaving over 600,000 Iraqi soldiers and government employees without jobs. Bremer also insisted that the CPA remain in control of Iraq until the country held elections, reversing an earlier plan to set up a transition government led by Iraqis. These decisions contributed to the beginning of the Iraqi insurgency opposed to the continuing U.S. presence. Fearing the further deterioration of Iraq's security situation, General John Abizaid ordered the end of the planned drawdown of soldiers, leaving over 130,000 U.S. soldiers in Iraq. The U.S. captured Hussein on December 13, 2003, but the occupation force continued to suffer casualties. Between the start of the invasion and the end of 2003, 580 U.S. soldiers died, with two thirds of those casualties occurring after Bush's "Mission Accomplished" speech. After 2003, more and more Iraqis began to see the U.S. as an occupying force. The fierce fighting of the First Battle of Fallujah alienated many in Iraq, while cleric Muqtada al-Sadr encouraged Shia Muslims to oppose the CPA. Sunni and Shia insurgents engaged in a campaign of guerrilla warfare against the United States, blunting the technological and organizational advantages of the U.S. military. While fighting in Iraq continued, Americans increasingly came to disapprove of Bush's handling of the Iraq War, contributing to a decline in Bush's approval ratings. Bremer left Iraq in June 2004, transferring power to the Iraqi Interim Government, which was led by Ayad Allawi. In January 2005, the Iraqi people voted on representatives for the Iraqi National Assembly, and the Shia United Iraqi Alliance formed a governing coalition led by Ibrahim al-Jaafari. In October 2005, the Iraqis ratified a new constitution that created a decentralized governmental structure dividing Iraq into communities of Sunni Arabs, Shia Arabs, and Kurds. After a December 2005 election, Jafari was succeeded as prime minister by another Shia, Nouri al-Maliki. The elections failed to quell the insurgency, and hundreds of U.S. soldiers stationed in Iraq died during 2005 and 2006. Sectarian violence between Sunnis and Shias also intensified following the 2006 al-Askari mosque bombing. In a December 2006 report, the bipartisan Iraq Study Group described the situation in Iraq as "grave and deteriorating," and the report called for the U.S. to gradually withdraw soldiers from Iraq. As the violence mounted in 2006, Rumsfeld and military leaders such as Abizaid and George Casey, the commander of the coalition forces in Iraq, called for a drawdown of forces in Iraq, but many within the administration argued that the U.S. should maintain its troop levels. Still intent on establishing a democratic government in Iraq, the Bush administration rejected a drawdown and began planning for a change in strategy and leadership following the 2006 elections. After the elections, Bush replaced Rumsfeld with Gates, while David Petraeus replaced Casey and William J. Fallon replaced Abizaid. Bush and his National Security Council formed a plan to "double down" in Iraq, increasing the number of U.S. soldiers in hopes of establishing a stable democracy. After Maliki indicated his support for an increase of U.S. soldiers, Bush announced in January 2007 that the U.S. would send an additional 20,000 soldiers to Iraq as part of a "surge" of forces. Though Senator McCain and a few other hawks supported Bush's new strategy, many other members of Congress from both parties expressed doubt or outright opposition to it. In April 2007, Congress, now controlled by Democrats, passed a bill that called for a total withdrawal of all U.S. troops by April 2008, but Bush vetoed the bill. Without the votes to override the veto, Congress passed a bill that continued to fund the war but also included the Fair Minimum Wage Act of 2007, which increased the federal minimum wage. U.S. and Iraqi casualties continuously declined after May 2007, and Bush declared that the surge had been a success in September 2007. He subsequently ordered a drawdown of troops, and the number of U.S. soldiers in Iraq declined from 168,000 in September 2007 to 145,000 when Bush left office. The decline in casualties following the surge coincided with several other favorable trends, including the Anbar Awakening and Muqtada al-Sadr's decision to order his followers to cooperate with the Iraqi government. In 2008, at the insistence of Maliki, Bush signed the U.S.–Iraq Status of Forces Agreement, which promised complete withdrawal of U.S. troops by the end of 2011. The U.S. would withdraw its forces from Iraq in December 2011, though it later re-deployed soldiers to Iraq to assist government forces in the Iraqi Civil War. During and after the invasion of Afghanistan, the U.S. captured numerous members of al-Qaeda and the Taliban. Rather than bringing the prisoners before domestic or international courts, Bush decided to set up a new system of military tribunals to try the prisoners. In order to avoid the restrictions of the United States Constitution, Bush held the prisoners at secret CIA prisons in various countries as well as at the Guantanamo Bay detention camp. Because the Guantanamo Bay camp is on territory that the U.S. technically leases from Cuba, individuals within the camp are not accorded the same constitutional protections that they would have on U.S. territory. Bush also decided that these "enemy combatants" were not entitled to all of the protections of the Geneva Conventions as they were not affiliated with sovereign states. In hopes of obtaining information from the prisoners, Bush allowed the use of "enhanced interrogation techniques" such as waterboarding. The treatment of prisoners at Abu Ghraib, a U.S. prison in Iraq, elicited widespread outrage after photos of prisoner abuse were made public. In 2005, Congress passed the Detainee Treatment Act, which purported to ban torture, but in his signing statement Bush asserted that his executive power gave him the authority to waive the restrictions put in place by the bill. Bush's policies suffered a major rebuke from the Supreme Court in the 2006 case of Hamdan v. Rumsfeld, in which the court rejected Bush's use of military commissions without congressional approval and held that all detainees were protected by the Geneva Conventions. Following the ruling, Congress passed the Military Commissions Act of 2006, which effectively overturned Hamdan. The Supreme Court overturned a portion of that act in the 2008 case of Boumediene v. Bush, but the Guantanamo detention camp remained open at the end of Bush's presidency. The Israeli–Palestinian conflict, ongoing since the middle of the 20th century, continued under Bush. After President Clinton's 2000 Camp David Summit had ended without an agreement, the Second Intifada had begun in September 2000. While previous administrations had tried to act as a neutral authority between the Israelis and Palestinians, the Bush administration placed the blame for the violence on the Palestinians, angering Arab states such as Saudi Arabia. However, Bush's support for a two-state solution helped smooth over a potential diplomatic split with the Saudis. In hopes of establishing peace between the Israelis and Palestinians, the Bush administration proposed the road map for peace, but his plan was not implemented and tensions were heightened following the victory of Hamas in the 2006 Palestinian elections. Believing that protectionism hampered economic growth, Bush concluded free trade agreements with numerous countries. When Bush took office, the United States had free trade agreements with just three countries: Israel, Canada, and Mexico. Bush signed the Chile–United States Free Trade Agreement and the Singapore–United States Free Trade Agreement in 2003, and he concluded the Morocco-United States Free Trade Agreement and the Australia–United States Free Trade Agreement the following year. He also concluded the Bahrain–United States Free Trade Agreement, the Oman–United States Free Trade Agreement, the Peru–United States Trade Promotion Agreement, and the Dominican Republic–Central America Free Trade Agreement. Additionally, Bush reached free trade agreements with South Korea, Colombia, and Panama, though agreements with these countries were not ratified until 2011. In 2002 the US withdrew from the U.S.-Russian Anti-Ballistic Missile Treaty. This marked the first time in post-WW2 history that the United States has withdrawn from a major international arms treaty. China expressed displeasure at America's withdrawal. Then newly elected Russian President Vladimir Putin stated that American withdrawal from the ABM Treaty was a mistake, and subsequently in a 1 March 2018 Presidential Address to the Federal Assembly announced the development of a series of technologically new missile systems in response to the Bush withdrawal. In Oliver Stone's 2017 The Putin Interviews, Putin said that in trying to persuade Russia to accept US withdrawal from the treaty, both Clinton and Bush had tried to convince him of an emerging nuclear threat from Iran. On 14 July 2007, Russia announced that it would suspend implementation of its Treaty on Conventional Armed Forces in Europe obligations, effective after 150 days. This failure can be said to mark the start of the Putinian Revanchism. Bush emphasized creating a better personal relationship with Russian president Vladimir Putin in order to ensure harmonious relations between the U.S. and Russia. After meeting with Putin in June 2001, both presidents expressed optimistic views regarding cooperation between the two former Cold War rivals. After the 9/11 attacks, Putin allowed the U.S. to use Russian airspace, and Putin encouraged Central Asian states to grant basing rights to the U.S. In May 2002, the U.S. and Russia signed the Strategic Offensive Reductions Treaty, which sought to dramatically reduce the nuclear stockpiles of both countries. Relations between Bush and Putin cooled during Bush's second term, as Bush became increasingly critical of Putin's suppression of political opponents in Russia, and they fell to new lows after the outbreak of the Russo-Georgian War in 2008. In his 2002 State of the Union Address, Bush grouped Iran with Iraq and North Korea as a member of the "Axis of Evil", accusing Iran of aiding terrorist organizations. In 2006, Iran re-opened three of its nuclear facilities, potentially allowing it to begin the process of building a nuclear bomb. After the resumption of the Iranian nuclear program, many within the U.S. military and foreign policy community speculated that Bush might attempt to impose regime change on Iran. In December 2006, the United Nations Security Council unanimously passed Resolution 1737, which imposed sanctions on Iran in order to curb its nuclear program. North Korea had developed weapons of mass destruction for several years prior to Bush's inauguration, and the Clinton administration had sought to trade economic assistance for an end to the North Korean WMD program. Though Secretary of State Powell urged the continuation of the rapprochement, other administration officials, including Vice President Cheney, were more skeptical of the good faith of the North Koreans. Bush instead sought to isolate North Korea in the hope that the regime would eventually collapse. North Korea launched missile tests on July 5, 2006, leading to United Nations Security Council Resolution 1695. The country said on October 3, "The U.S. extreme threat of a nuclear war and sanctions and pressure compel the DPRK to conduct a nuclear test", which the Bush administration denied and denounced. Days later, North Korea followed through on its promise to test nuclear weapons. On October 14, the Security Council unanimously passed United Nations Security Council Resolution 1718, sanctioning North Korea for the test. In the waning days of his presidency, Bush attempted to re-open negotiations with North Korea, but North Korea continued to develop its nuclear programs. Shortly after taking office, Bush pledged $200 million to The Global Fund to Fight AIDS, Tuberculosis and Malaria. Finding this effort insufficient, Bush assembled a team of experts to find the best way for the U.S. reduce the worldwide damage caused by the AIDS epidemic. The experts, led by Anthony S. Fauci, recommended that the U.S. focus on providing antiretroviral drugs to developing nations in Africa and the Caribbean. In his State of the Union message in January 2003, President Bush outlined a five-year strategy for global emergency AIDS relief, the President's Emergency Plan For AIDS Relief. With the approval of Congress, Bush committed $15 billion to this effort, which represented a huge increase compared to funding under previous administrations. Near the end of his presidency, Bush signed a re-authorization of the program that doubled its funding. By 2012, the PEPFAR program provided antiretroviral drugs for over 4.5 million people. Controversies In July 2005, Bush and Vice President Dick Cheney's respective chief political advisers, Karl Rove and Lewis "Scooter" Libby, came under fire for revealing the identity of covert Central Intelligence Agency (CIA) agent Valerie Plame to reporters in the CIA leak scandal. Plame's husband, Joseph C. Wilson, had challenged Bush's assertion that Hussein had sought to obtain uranium from Africa, and a special prosecutor was tasked with determining whether administration officials had leaked Plame's identity in retribution against Wilson. Libby resigned on October 28, hours after his indictment by a grand jury on multiple counts of perjury, false statements, and obstruction in this case. In March 2007, Libby was convicted on four counts, and Cheney pressed Bush to pardon Libby. Rather than pardoning Libby or allowing him to go to jail, Bush commuted Libby's sentence, creating a split with Cheney, who accused Bush of leaving "a soldier on the battlefield." In December 2006, Bush dismissed eight United States attorneys. Though these attorneys serve at the pleasure of the president, the large-scale mid-term dismissal was without precedent, and Bush faced accusations that he had dismissed the attorneys for purely political reasons. During the 2006 elections, several Republican officials complained that the U.S. attorneys had not sufficiently investigated voter fraud. With the encouragement of Harriet Miers and Karl Rove, Attorney General Gonzales dismissed eight U.S. attorneys who were considered insufficiently supportive of the administration's policies. Though Gonzales argued that the attorneys had been fired for performance reasons, publicly released documents showed that the attorneys were dismissed for political reasons. As a result of the dismissals and the subsequent congressional investigations, Rove and Gonzales both resigned. A 2008 report by the Justice Department inspector general found that the dismissals had been politically motivated, but no one was ever prosecuted in connection to the dismissals. Approval ratings During Bush’s presidency, his approval ratings experienced extreme fluctuations. Following the September 11 terrorist attacks, Bush achieved an all-time high approval rating of 90%, the highest since tracking began in 1937. However, his approval ratings sharply declined over the years, reaching a low of 25% in the Gallup Poll in 2008 amid the fallout from the 2008 financial crisis, marking the third-lowest approval rating for any president in the modern era. Bush began his presidency with ratings near fifty percent. In the time of national crisis following the September 11 attacks, polls showed approval ratings of greater than 85%, peaking in one October 2001 poll at 92%, and a steady 80–90% approval for about four months after the attacks. Afterward, his ratings steadily declined as the economy suffered and the Iraq War initiated by his administration continued. By early 2006, his average rating was averaging below 40%, and in July 2008, a poll indicated a near all-time low of 22%. Upon leaving office the final poll recorded his approval rating as 19%, a record low for any U.S. president. Elections during the Bush presidency In the 2002 mid-term elections, Bush became the first president since the 1930s to see his own party pick up seats in both houses of Congress. Republicans picked up two seats in the Senate elections, allowing them to re-take control of the chamber. Bush delivered speeches in several venues in support of his party, campaigning on his desire to remove the administration of Saddam Hussein. Bush saw the election results as a vindication of his domestic and foreign policies. Bush and his campaign team seized on the idea of Bush as a "strong wartime leader," though this was undermined by the increasingly-unpopular Iraq War. His conservative policies on tax cuts and several other issues appealed to many on the right, but Bush could also lay claim to some centrist achievements, including No Child Left Behind, Sarbanes-Oxley, and Medicare Part D. Fearing that he might hurt Bush's re-election chances, Cheney offered to step down from the ticket, but Bush refused this offer, and the two were re-nominated without opposition at the 2004 Republican National Convention. On the advice of pollster Matthew Dowd, who perceived a steady decline in the number of swing voters, the 2004 Bush campaign emphasized turning out conservative voters rather than the persuasion of moderates. In the 2004 Democratic primaries, Senator John Kerry of Massachusetts defeated several other candidates, effectively clinching the nomination on March 2. A Vietnam War veteran, Kerry had voted to authorize the Iraq War but had come to oppose it. The Bush campaign sought to define Kerry as a "flip-flopper" due to his vote on a bill funding the Afghanistan and Iraq wars. Kerry sought to convince Republican senator John McCain to become his running mate, but chose Senator John Edwards of North Carolina for the position after McCain rejected the offer. The election saw a major jump in turnout; while 105 million people had voted in 2000, 123 million people voted in 2004. Bush won re-election with 50.7% percent of the popular vote, making him the first individual to win a majority of the popular vote since his father in 1988, while Kerry received 48.3% of the popular vote. Bush won 286 electoral votes, winning Iowa, New Mexico, and every state he won in 2000 except for New Hampshire, while Kerry received 251 electoral votes. In the concurrent congressional elections, Republicans secured a government trifecta after retaining their majorities in the House of Representatives and the Senate, and Speaker of the House Dennis Hastert and Senate Majority Leader Bill Frist both remained in their posts. Damaged by the unpopularity of the Iraq War and President Bush, the Republicans lost control of both houses of Congress in the 2006 mid-term elections. Republicans were also damaged by various scandals, including the Jack Abramoff Indian lobbying scandal and the Mark Foley scandal. The elections confirmed Bush's declining popularity, as many of the candidates he had personally campaigned for were defeated. After the elections, Bush announced the resignation of Rumsfeld and promised to work with the new Democratic majority. The 2008 elections took place on November 4. Bush was term-limited in 2008 due to the 22nd Amendment. Senator John McCain won the 2008 Republican presidential primaries, while Democratic senator Barack Obama of Illinois defeated Senator Hillary Clinton of New York to win the 2008 Democratic presidential primaries. Obama's victory in the Democratic presidential primaries was due in large part to his strong opposition to the Iraq War, as Clinton had voted to authorize the Iraq War in 2002. McCain sought to distance himself from the unpopular policies of Bush, and Bush appeared only by satellite at the 2008 Republican National Convention, making him the first sitting president since Lyndon B. Johnson to not appear at his own party's convention in 1968. McCain briefly took the lead in polls of the race taken after the Republican convention, but Obama quickly re-emerged as the leader in polls. McCain's campaign was badly damaged by the unpopularity of the Bush administration and the Iraq War, and McCain's response to the outbreak of a full-blown financial crisis in September 2008 was widely viewed as erratic. Obama won 365 electoral votes and 52.9% of the popular vote. The election gave Democrats unified control of the legislative and executive branches for the first time since the 1994 elections. After the election, Bush congratulated Obama and invited him to the White House. With the help of the Bush administration, the presidential transition of Barack Obama was widely regarded as successful, particularly for a transition between presidents of different parties. During his inauguration on January 20, 2009, Obama thanked Bush for his service as president and his support of Obama's transition. Evaluation and legacy A 2009 C-SPAN survey of historians ranked Bush in 36th place among the 42 former presidents. A 2017 C-SPAN poll of historians ranked Bush as the 33rd greatest president. A 2018 poll of the American Political Science Association's Presidents and Executive Politics section ranked Bush as the 30th greatest president. Historian Melvyn Leffler writes that the Bush administration's achievements in foreign policy "were outweighed by the administration's failure to achieve many of its most important goals." In summing up evaluations of Bush's presidency, Gary L. Gregg II writes: The Bush presidency transformed American politics, its economy, and its place in the world, but not in ways that could have been predicted when the governor of Texas declared his candidacy for America's highest office. As president, Bush became a lightning rod for controversy. His controversial election and policies, especially the war in Iraq, deeply divided the American people. Arguably his greatest moment as president was his initial, heartfelt response to the tragedy of the 9/11 attacks. Soon, however, his administration was overshadowed by the wars in Afghanistan and Iraq. President Bush's place in U.S. history will be debated and reconsidered for many years to come. Andrew Rudalevige has compiled a list of the 14 most important achievements under the Bush administration: See also Notes References Further reading Primary sources External links |
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[SOURCE: https://en.wikipedia.org/wiki/Orion_(constellation)#cite_ref-4] | [TOKENS: 4993] |
Contents Orion (constellation) Orion is a prominent set of stars visible during winter in the northern celestial hemisphere. It is one of the 88 modern constellations; it was among the 48 constellations listed by the 2nd-century AD/CE astronomer Ptolemy. It is named after a hunter in Greek mythology. Orion is most prominent during winter evenings in the Northern Hemisphere, as are five other constellations that have stars in the Winter Hexagon asterism. Orion's two brightest stars, Rigel (β) and Betelgeuse (α), are both among the brightest stars in the night sky; both are supergiants and slightly variable. There are a further six stars brighter than magnitude 3.0, including three making the short straight line of the Orion's Belt asterism. Orion also hosts the radiant of the annual Orionids, the strongest meteor shower associated with Halley's Comet, and the Orion Nebula, one of the brightest nebulae in the sky. Characteristics Orion is bordered by Taurus to the northwest, Eridanus to the southwest, Lepus to the south, Monoceros to the east, and Gemini to the northeast. Covering 594 square degrees, Orion ranks 26th of the 88 constellations in size. The constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 26 sides. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 04h 43.3m and 06h 25.5m , while the declination coordinates are between 22.87° and −10.97°. The constellation's three-letter abbreviation, as adopted by the International Astronomical Union in 1922, is "Ori". Orion is most visible in the evening sky from January to April, winter in the Northern Hemisphere, and summer in the Southern Hemisphere. In the tropics (less than about 8° from the equator), the constellation transits at the zenith. From May to July (summer in the Northern Hemisphere, winter in the Southern Hemisphere), Orion is in the daytime sky and thus invisible at most latitudes. However, for much of Antarctica in the Southern Hemisphere's winter months, the Sun is below the horizon even at midday. Stars (and thus Orion, but only the brightest stars) are then visible at twilight for a few hours around local noon, just in the brightest section of the sky low in the North where the Sun is just below the horizon. At the same time of day at the South Pole itself (Amundsen–Scott South Pole Station), Rigel is only 8° above the horizon, and the Belt sweeps just along it. In the Southern Hemisphere's summer months, when Orion is normally visible in the night sky, the constellation is actually not visible in Antarctica because the Sun does not set at that time of year south of the Antarctic Circle. In countries close to the equator (e.g. Kenya, Indonesia, Colombia, Ecuador), Orion appears overhead in December around midnight and in the February evening sky. Navigational aid Orion is very useful as an aid to locating other stars. By extending the line of the Belt southeastward, Sirius (α CMa) can be found; northwestward, Aldebaran (α Tau). A line eastward across the two shoulders indicates the direction of Procyon (α CMi). A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Rigel is part of the Winter Circle asterism. Sirius and Procyon, which may be located from Orion by following imaginary lines (see map), also are points in both the Winter Triangle and the Circle. Features Orion's seven brightest stars form a distinctive hourglass-shaped asterism, or pattern, in the night sky. Four stars—Rigel, Betelgeuse, Bellatrix, and Saiph—form a large roughly rectangular shape, at the center of which lie the three stars of Orion's Belt—Alnitak, Alnilam, and Mintaka. His head is marked by an additional eighth star called Meissa, which is fairly bright to the observer. Descending from the Belt is a smaller line of three stars, Orion's Sword (the middle of which is in fact not a star but the Orion Nebula), also known as the hunter's sword. Many of the stars are luminous hot blue supergiants, with the stars of the Belt and Sword forming the Orion OB1 association. Standing out by its red hue, Betelgeuse may nevertheless be a runaway member of the same group. Orion's Belt, or The Belt of Orion, is an asterism within the constellation. It consists of three bright stars: Alnitak (Zeta Orionis), Alnilam (Epsilon Orionis), and Mintaka (Delta Orionis). Alnitak is around 800 light-years away from Earth, 100,000 times more luminous than the Sun, and shines with a magnitude of 1.8; much of its radiation is in the ultraviolet range, which the human eye cannot see. Alnilam is approximately 2,000 light-years from Earth, shines with a magnitude of 1.70, and with an ultraviolet light that is 375,000 times more luminous than the Sun. Mintaka is 915 light-years away and shines with a magnitude of 2.21. It is 90,000 times more luminous than the Sun and is a double star: the two orbit each other every 5.73 days. In the Northern Hemisphere, Orion's Belt is best visible in the night sky during the month of January at around 9:00 pm, when it is approximately around the local meridian. Just southwest of Alnitak lies Sigma Orionis, a multiple star system composed of five stars that have a combined apparent magnitude of 3.7 and lying at a distance of 1150 light-years. Southwest of Mintaka lies the quadruple star Eta Orionis. Orion's Sword contains the Orion Nebula, the Messier 43 nebula, Sh 2-279 (also known as the Running Man Nebula), and the stars Theta Orionis, Iota Orionis, and 42 Orionis. Three stars comprise a small triangle that marks the head. The apex is marked by Meissa (Lambda Orionis), a hot blue giant of spectral type O8 III and apparent magnitude 3.54, which lies some 1100 light-years distant. Phi-1 and Phi-2 Orionis make up the base. Also nearby is the young star FU Orionis. Stretching north from Betelgeuse are the stars that make up Orion's club. Mu Orionis marks the elbow, Nu and Xi mark the handle of the club, and Chi1 and Chi2 mark the end of the club. Just east of Chi1 is the Mira-type variable red giant star U Orionis. West from Bellatrix lie six stars all designated Pi Orionis (π1 Ori, π2 Ori, π3 Ori, π4 Ori, π5 Ori, and π6 Ori) which make up Orion's shield. Around 20 October each year, the Orionid meteor shower (Orionids) reaches its peak. Coming from the border with the constellation Gemini, as many as 20 meteors per hour can be seen. The shower's parent body is Halley's Comet. Hanging from Orion's Belt is his sword, consisting of the multiple stars θ1 and θ2 Orionis, called the Trapezium and the Orion Nebula (M42). This is a spectacular object that can be clearly identified with the naked eye as something other than a star. Using binoculars, its clouds of nascent stars, luminous gas, and dust can be observed. The Trapezium cluster has many newborn stars, including several brown dwarfs, all of which are at an approximate distance of 1,500 light-years. Named for the four bright stars that form a trapezoid, it is largely illuminated by the brightest stars, which are only a few hundred thousand years old. Observations by the Chandra X-ray Observatory show both the extreme temperatures of the main stars—up to 60,000 kelvins—and the star forming regions still extant in the surrounding nebula. M78 (NGC 2068) is a nebula in Orion. With an overall magnitude of 8.0, it is significantly dimmer than the Great Orion Nebula that lies to its south; however, it is at approximately the same distance, at 1600 light-years from Earth. It can easily be mistaken for a comet in the eyepiece of a telescope. M78 is associated with the variable star V351 Orionis, whose magnitude changes are visible in very short periods of time. Another fairly bright nebula in Orion is NGC 1999, also close to the Great Orion Nebula. It has an integrated magnitude of 10.5 and is 1500 light-years from Earth. The variable star V380 Orionis is embedded in NGC 1999. Another famous nebula is IC 434, the Horsehead Nebula, near Alnitak (Zeta Orionis). It contains a dark dust cloud whose shape gives the nebula its name. NGC 2174 is an emission nebula located 6400 light-years from Earth. Besides these nebulae, surveying Orion with a small telescope will reveal a wealth of interesting deep-sky objects, including M43, M78, and multiple stars including Iota Orionis and Sigma Orionis. A larger telescope may reveal objects such as the Flame Nebula (NGC 2024), as well as fainter and tighter multiple stars and nebulae. Barnard's Loop can be seen on very dark nights or using long-exposure photography. All of these nebulae are part of the larger Orion molecular cloud complex, which is located approximately 1,500 light-years away and is hundreds of light-years across. Due to its proximity, it is one of the most intense regions of stellar formation visible from Earth. The Orion molecular cloud complex forms the eastern part of an even larger structure, the Orion–Eridanus Superbubble, which is visible in X-rays and in hydrogen emissions. History and mythology The distinctive pattern of Orion is recognized in numerous cultures around the world, and many myths are associated with it. Orion is used as a symbol in the modern world. In Siberia, the Chukchi people see Orion as a hunter; an arrow he has shot is represented by Aldebaran (Alpha Tauri), with the same figure as other Western depictions. In Greek mythology, Orion was a gigantic, supernaturally strong hunter, born to Euryale, a Gorgon, and Poseidon (Neptune), god of the sea. One myth recounts Gaia's rage at Orion, who dared to say that he would kill every animal on Earth. The angry goddess tried to dispatch Orion with a scorpion. This is given as the reason that the constellations of Scorpius and Orion are never in the sky at the same time. However, Ophiuchus, the Serpent Bearer, revived Orion with an antidote. This is said to be the reason that the constellation of Ophiuchus stands midway between the Scorpion and the Hunter in the sky. The constellation is mentioned in Horace's Odes (Ode 3.27.18), Homer's Odyssey (Book 5, line 283) and Iliad, and Virgil's Aeneid (Book 1, line 535). In old Hungarian tradition, Orion is known as "Archer" (Íjász), or "Reaper" (Kaszás). In recently rediscovered myths, he is called Nimrod (Hungarian: Nimród), the greatest hunter, father of the twins Hunor and Magor. The π and o stars (on upper right) form together the reflex bow or the lifted scythe. In other Hungarian traditions, Orion's Belt is known as "Judge's stick" (Bírópálca). In Ireland and Scotland, Orion was called An Bodach, a figure from Irish folklore whose name literally means "the one with a penis [bod]" and was the husband of the Cailleach (hag). In Scandinavian tradition, Orion's Belt was known as "Frigg's Distaff" (friggerock) or "Freyja's distaff". The Finns call Orion's Belt and the stars below it "Väinämöinen's scythe" (Väinämöisen viikate). Another name for the asterism of Alnilam, Alnitak, and Mintaka is "Väinämöinen's Belt" (Väinämöisen vyö) and the stars "hanging" from the Belt as "Kaleva's sword" (Kalevanmiekka). There are claims in popular media that the Adorant from the Geißenklösterle cave, an ivory carving estimated to be 35,000 to 40,000 years old, is the first known depiction of the constellation. Scholars dismiss such interpretations, saying that perceived details such as a belt and sword derive from preexisting features in the grain structure of the ivory. The Babylonian star catalogues of the Late Bronze Age name Orion MULSIPA.ZI.AN.NA,[note 1] "The Heavenly Shepherd" or "True Shepherd of Anu" – Anu being the chief god of the heavenly realms. The Babylonian constellation is sacred to Papshukal and Ninshubur, both minor gods fulfilling the role of "messenger to the gods". Papshukal is closely associated with the figure of a walking bird on Babylonian boundary stones, and on the star map the figure of the Rooster is located below and behind the figure of the True Shepherd—both constellations represent the herald of the gods, in his bird and human forms respectively. In ancient Egypt, the stars of Orion were regarded as a god, called Sah. Because Orion rises before Sirius, the star whose heliacal rising was the basis for the Solar Egyptian calendar, Sah was closely linked with Sopdet, the goddess who personified Sirius. The god Sopdu is said to be the son of Sah and Sopdet. Sah is syncretized with Osiris, while Sopdet is syncretized with Osiris' mythological wife, Isis. In the Pyramid Texts, from the 24th and 23rd centuries BC, Sah is one of many gods whose form the dead pharaoh is said to take in the afterlife. The Armenians identified their legendary patriarch and founder Hayk with Orion. Hayk is also the name of the Orion constellation in the Armenian translation of the Bible. The Bible mentions Orion three times, naming it "Kesil" (כסיל, literally – fool). Though, this name perhaps is etymologically connected with "Kislev", the name for the ninth month of the Hebrew calendar (i.e. November–December), which, in turn, may derive from the Hebrew root K-S-L as in the words "kesel, kisla" (כֵּסֶל, כִּסְלָה, hope, positiveness), i.e. hope for winter rains.: Job 9:9 ("He is the maker of the Bear and Orion"), Job 38:31 ("Can you loosen Orion's belt?"), and Amos 5:8 ("He who made the Pleiades and Orion"). In ancient Aram, the constellation was known as Nephîlā′, the Nephilim are said to be Orion's descendants. In medieval Muslim astronomy, Orion was known as al-jabbar, "the giant". Orion's sixth brightest star, Saiph, is named from the Arabic, saif al-jabbar, meaning "sword of the giant". In China, Orion was one of the 28 lunar mansions Sieu (Xiù) (宿). It is known as Shen (參), literally meaning "three", for the stars of Orion's Belt. The Chinese character 參 (pinyin shēn) originally meant the constellation Orion (Chinese: 參宿; pinyin: shēnxiù); its Shang dynasty version, over three millennia old, contains at the top a representation of the three stars of Orion's Belt atop a man's head (the bottom portion representing the sound of the word was added later). The Rigveda refers to the constellation as Mriga (the Deer). Nataraja, "the cosmic dancer", is often interpreted as the representation of Orion. Rudra, the Rigvedic form of Shiva, is the presiding deity of Ardra nakshatra (Betelgeuse) of Hindu astrology. The Jain Symbol carved in the Udayagiri and Khandagiri Caves, India in 1st century BCE has a striking resemblance with Orion. Bugis sailors identified the three stars in Orion's Belt as tanra tellué, meaning "sign of three". The Seri people of northwestern Mexico call the three stars in Orion's Belt Hapj (a name denoting a hunter) which consists of three stars: Hap (mule deer), Haamoja (pronghorn), and Mojet (bighorn sheep). Hap is in the middle and has been shot by the hunter; its blood has dripped onto Tiburón Island. The same three stars are known in Spain and most of Latin America as "Las tres Marías" (Spanish for "The Three Marys"). In Puerto Rico, the three stars are known as the "Los Tres Reyes Magos" (Spanish for The Three Wise Men). The Ojibwa/Chippewa Native Americans call this constellation Mesabi for Big Man. To the Lakota Native Americans, Tayamnicankhu (Orion's Belt) is the spine of a bison. The great rectangle of Orion is the bison's ribs; the Pleiades star cluster in nearby Taurus is the bison's head; and Sirius in Canis Major, known as Tayamnisinte, is its tail. Another Lakota myth mentions that the bottom half of Orion, the Constellation of the Hand, represented the arm of a chief that was ripped off by the Thunder People as a punishment from the gods for his selfishness. His daughter offered to marry the person who can retrieve his arm from the sky, so the young warrior Fallen Star (whose father was a star and whose mother was human) returned his arm and married his daughter, symbolizing harmony between the gods and humanity with the help of the younger generation. The index finger is represented by Rigel; the Orion Nebula is the thumb; the Belt of Orion is the wrist; and the star Beta Eridani is the pinky finger. The seven primary stars of Orion make up the Polynesian constellation Heiheionakeiki which represents a child's string figure similar to a cat's cradle. Several precolonial Filipinos referred to the belt region in particular as "balatik" (ballista) as it resembles a trap of the same name which fires arrows by itself and is usually used for catching pigs from the bush. Spanish colonization later led to some ethnic groups referring to Orion's Belt as "Tres Marias" or "Tatlong Maria." In Māori tradition, the star Rigel (known as Puanga or Puaka) is closely connected with the celebration of Matariki. The rising of Matariki (the Pleiades) and Rigel before sunrise in midwinter marks the start of the Māori year. In Javanese culture, the constellation is often called Lintang Waluku or Bintang Bajak, referring to the shape of a paddy field plow. The imagery of the Belt and Sword has found its way into popular Western culture, for example in the form of the shoulder insignia of the 27th Infantry Division of the United States Army during both World Wars, probably owing to a pun on the name of the division's first commander, Major General John F. O'Ryan. The film distribution company Orion Pictures used the constellation as its logo. In artistic renderings, the surrounding constellations are sometimes related to Orion: he is depicted standing next to the river Eridanus with his two hunting dogs Canis Major and Canis Minor, fighting Taurus. He is sometimes depicted hunting Lepus the hare. He sometimes is depicted to have a lion's hide in his hand. There are alternative ways to visualise Orion. From the Southern Hemisphere, Orion is oriented south-upward, and the Belt and Sword are sometimes called the saucepan or pot in Australia and New Zealand. Orion's Belt is called Drie Konings (Three Kings) or the Drie Susters (Three Sisters) by Afrikaans speakers in South Africa and are referred to as les Trois Rois (the Three Kings) in Daudet's Lettres de Mon Moulin (1866). The appellation Driekoningen (the Three Kings) is also often found in 17th and 18th-century Dutch star charts and seaman's guides. The same three stars are known in Spain, Latin America, and the Philippines as "Las Tres Marías" (The Three Marys), and as "Los Tres Reyes Magos" (The Three Wise Men) in Puerto Rico. Even traditional depictions of Orion have varied greatly. Cicero drew Orion in a similar fashion to the modern depiction. The Hunter held an unidentified animal skin aloft in his right hand; his hand was represented by Omicron2 Orionis and the skin was represented by the five stars designated Pi Orionis. Saiph and Rigel represented his left and right knees, while Eta Orionis and Lambda Leporis were his left and right feet, respectively. As in the modern depiction, Mintaka, Alnilam, and Alnitak represented his Belt. His left shoulder was represented by Betelgeuse, and Mu Orionis made up his left arm. Meissa was his head, and Bellatrix his right shoulder. The depiction of Hyginus was similar to that of Cicero, though the two differed in a few important areas. Cicero's animal skin became Hyginus's shield (Omicron and Pi Orionis), and instead of an arm marked out by Mu Orionis, he holds a club (Chi Orionis). His right leg is represented by Theta Orionis and his left leg is represented by Lambda, Mu, and Epsilon Leporis. Further Western European and Arabic depictions have followed these two models. Future Orion is located on the celestial equator, but it will not always be so located due to the effects of precession of the Earth's axis. Orion lies well south of the ecliptic, and it only happens to lie on the celestial equator because the point on the ecliptic that corresponds to the June solstice is close to the border of Gemini and Taurus, to the north of Orion. Precession will eventually carry Orion further south, and by AD 14000, Orion will be far enough south that it will no longer be visible from the latitude of Great Britain. Further in the future, Orion's stars will gradually move away from the constellation due to proper motion. However, Orion's brightest stars all lie at a large distance from Earth on an astronomical scale—much farther away than Sirius, for example. Orion will still be recognizable long after most of the other constellations—composed of relatively nearby stars—have distorted into new configurations, with the exception of a few of its stars eventually exploding as supernovae, for example Betelgeuse, which is predicted to explode sometime in the next million years. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Habitable_zone] | [TOKENS: 8741] |
Contents Habitable zone In astronomy and astrobiology, the habitable zone (HZ), the circumstellar habitable zone (CHZ), the Goldilocks zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence. As such, it is considered by many to be a major factor of planetary habitability, and the most likely place to find extraterrestrial liquid water and biosignatures elsewhere in the universe. The habitable zone is also called the Goldilocks zone, a metaphor, allusion and antonomasia of the children's fairy tale of "Goldilocks and the Three Bears", in which a little girl chooses from sets of three items, rejecting the ones that are too extreme (large or small, hot or cold, etc.), and settling on the one in the middle, which is "just right". Since the concept was first presented many stars have been confirmed to possess an HZ planet, including some systems that consist of multiple HZ planets. Most such planets, being either super-Earths or gas giants, are more massive than Earth, because massive planets are easier to detect. On November 4, 2013, astronomers reported, based on Kepler space telescope data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs in the Milky Way. About 11 billion of these may be orbiting Sun-like stars. Proxima Centauri b, located about 4.2 light-years (1.3 parsecs) from Earth in the constellation of Centaurus, is the nearest known exoplanet, and is orbiting in the habitable zone of its star. The HZ is also of particular interest to the emerging field of habitability of natural satellites because planetary mass moons in the HZ might outnumber planets. In subsequent decades, the HZ concept began to be challenged as a primary criterion for life, so the concept is still evolving. Since the discovery of evidence for extraterrestrial liquid water, substantial quantities of it are now thought to occur outside the circumstellar habitable zone. The concept of deep biospheres, like Earth's, that exist independently of stellar energy, are now generally accepted in astrobiology given the large amount of liquid water known to exist in lithospheres and asthenospheres of the Solar System. Sustained by other energy sources, such as tidal heating or radioactive decay or pressurized by non-atmospheric means, liquid water may be found even on rogue planets, or their moons. Liquid water can also exist at a wider range of temperatures and pressures as a solution, for example with sodium chlorides in seawater on Earth, chlorides and sulphates on equatorial Mars, or ammoniates, due to its different colligative properties. In addition, other circumstellar zones, where non-water solvents favorable to hypothetical life based on alternative biochemistries could exist in liquid form at the surface, have been proposed. History An estimate of the range of distances from the Sun allowing the existence of liquid water appears in Newton's Principia (Book III, Section 1, corol. 4). The philosopher Louis Claude de Saint-Martin speculated in his 1802 work Man: His True Nature and Ministry, "... we may presume, that, being susceptible of vegetation, it [the Earth] has been placed, in the series of planets, in the rank which was necessary, and at exactly the right distance from the sun, to accomplish its secondary object of vegetation; and from this we might infer that the other planets are either too near or too remote from the sun, to vegetate." Possibly the earliest use of the term habitable zone was in 1913, by Edward Maunder in his book "Are The Planets Inhabited?". Hubertus Strughold's 1953 treatise The Green and the Red Planet: A Physiological Study of the Possibility of Life on Mars used the term "ecosphere" and referred to various "zones" in which life could emerge. In the same year, Harlow Shapley wrote "Liquid Water Belt", which described the same concept in further scientific detail. Both works stressed the importance of liquid water to life. Su-Shu Huang, an American astrophysicist argued in 1960 that circumstellar habitable zones, and by extension extraterrestrial life, would be uncommon in multiple star systems, given the gravitational instabilities of those systems. The concept of habitable zones was further developed in 1964 by Stephen H. Dole in his book Habitable Planets for Man, in which he discussed the concept of the circumstellar habitable zone as well as various other determinants of planetary habitability, eventually estimating the number of habitable planets in the Milky Way to be about 600 million. At the same time, science-fiction author Isaac Asimov introduced the concept of a circumstellar habitable zone to the general public through his various explorations of space colonization. The term "Goldilocks zone" emerged in the 1970s, referencing specifically a region around a star whose temperature is "just right" for water to be present in the liquid phase. James Kasting was the first to present a detailed model for the habitable zone for exoplanets. An update to the habitable zone concept came in 2000 when astronomers Peter Ward and Donald Brownlee introduced the idea of the "galactic habitable zone", which they later developed with Guillermo Gonzalez. The galactic habitable zone, defined as the region where life is most likely to emerge in a galaxy, encompasses those regions close enough to a galactic center that stars there are enriched with heavier elements, but not so close that star systems, planetary orbits, and the emergence of life would be frequently disrupted by the intense radiation and enormous gravitational forces commonly found at galactic centers. Subsequently, some astrobiologists propose that the concept be extended to other solvents, including dihydrogen, sulfuric acid, dinitrogen, formamide, and methane, among others, which would support hypothetical life forms that use an alternative biochemistry. In 2013, further developments in habitable zone concepts were made with the proposal of a circum- planetary habitable zone, also known as the "habitable edge", to encompass the region around a planet where the orbits of natural satellites would not be disrupted, and at the same time tidal heating from the planet would not cause liquid water to boil away. Determination A 'circumstellar habitable zone' is the region around a star which allows planets with liquid water. Whether a given planet in this zone has water depends on surface conditions that are dependent on a host of different individual properties of that planet. This misunderstanding is reflected in excited reports of 'habitable planets'. Since it is completely unknown whether conditions on these distant HZ worlds could host life, different terminology is needed. Whether a body is in the circumstellar habitable zone of its host star is dependent on the radius of the planet's orbit (for natural satellites, the host planet's orbit), the mass of the body itself, and the radiative flux of the host star. Given the large spread in the masses of planets within a circumstellar habitable zone, coupled with the discovery of super-Earth planets that can sustain thicker atmospheres and stronger magnetic fields than Earth, circumstellar habitable zones are now split into two separate regions—a "conservative habitable zone" in which lower-mass planets like Earth can remain habitable, complemented by a larger "extended habitable zone" in which a planet like Venus, with stronger greenhouse effects, can have the right temperature for liquid water to exist at the surface. Estimates for the habitable zone within the Solar System range from 0.38 to 10.0 astronomical units, though arriving at these estimates has been challenging for a variety of reasons. Numerous planetary mass objects orbit within, or close to, this range and as such receive sufficient sunlight to raise temperatures above the freezing point of water. However, their atmospheric conditions vary substantially. The aphelion of Venus, for example, touches the inner edge of the zone in most estimates and, while atmospheric pressure at the surface is sufficient for liquid water, a strong greenhouse effect raises surface temperatures to 462 °C (864 °F) at which water can only exist as vapor. The entire orbits of the Moon, Mars, and numerous asteroids also lie within various estimates of the habitable zone. Only at Mars' lowest elevations (less than 30% of the planet's surface) is atmospheric pressure and temperature sufficient for water to, if present, exist in liquid form for short periods. At Hellas Basin, for example, atmospheric pressures can reach 1,115 Pa and temperatures above zero Celsius (about the triple point for water) for 70 days in the Martian year. Despite indirect evidence in the form of seasonal flows on warm Martian slopes, no confirmation has been made of the presence of liquid water at the surface. While other objects orbit partly within this zone, including comets, Ceres is the only one of planetary mass. Despite this, studies indicate the strong possibility of past liquid water on the surface of Venus, the Moon, Mars, Vesta and Ceres, suggesting a more common phenomenon than previously thought. Since sustainable liquid water is thought to be essential to support complex life, most estimates, therefore, are inferred from the effect that a repositioned orbit would have on the habitability of Earth or Venus as their surface gravity allows sufficient atmosphere to be retained for several billion years. According to the extended habitable zone concept, planetary-mass objects with atmospheres capable of inducing sufficient radiative forcing could possess liquid water farther out from the Sun. Such objects could include those whose atmospheres contain a high component of greenhouse gas and terrestrial planets much more massive than Earth (super-Earth class planets), that have retained atmospheres with surface pressures of up to 100 kbar. There are no examples of such objects in the Solar System to study; not enough is known about the nature of atmospheres of these kinds of extrasolar objects, and their position in the habitable zone cannot determine the net temperature effect of such atmospheres including induced albedo, anti-greenhouse or other possible heat sources. For reference, the average distance from the Sun of some major bodies within the various estimates of the habitable zone is: Mercury, 0.39 AU; Venus, 0.72 AU; Earth, 1.00 AU; Mars, 1.52 AU; Vesta, 2.36 AU; Ceres and Pallas, 2.77 AU; Jupiter, 5.20 AU; Saturn, 9.58 AU. In the most conservative estimates, only Earth lies within the zone; in the most permissive estimates, even Saturn at perihelion, or Mercury at aphelion, might be included. Astronomers use stellar flux and the inverse-square law to extrapolate circumstellar habitable zone models created for the Solar System to other stars. For example, according to Kopparapu's habitable zone estimate, although the Solar System has a circumstellar habitable zone centered at 1.34 AU from the Sun, a star with 0.25 times the luminosity of the Sun would have a habitable zone centered at 0.25 {\displaystyle {\sqrt {0.25}}} , or 0.5, the distance from the star, corresponding to a distance of 0.67 AU. Various complicating factors, though, including the individual characteristics of stars themselves, mean that extrasolar extrapolation of the HZ concept is more complex. Some scientists argue that the concept of a circumstellar habitable zone is actually limited to stars in certain types of systems or of certain spectral types. Binary systems, for example, have circumstellar habitable zones that differ from those of single-star planetary systems, in addition to the orbital stability concerns inherent with a three-body configuration. If the Solar System were such a binary system, the outer limits of the resulting circumstellar habitable zone could extend as far as 2.4 AU. With regard to spectral types, Zoltán Balog proposes that O-type stars cannot form planets due to the photoevaporation caused by their strong ultraviolet emissions. Studying ultraviolet emissions, Andrea Buccino found that only 40% of stars studied (including the Sun) had overlapping liquid water and ultraviolet habitable zones. Stars smaller than the Sun, on the other hand, have distinct impediments to habitability. For example, Michael Hart proposed that only main-sequence stars of spectral class K0 or brighter could offer habitable zones, an idea which has evolved in modern times into the concept of a tidal locking radius for red dwarfs. Within this radius, which is coincidental with the red-dwarf habitable zone, it has been suggested that the volcanism caused by tidal heating could cause a "tidal Venus" planet with high temperatures and no hospitable environment for life. Others maintain that circumstellar habitable zones are more common and that it is indeed possible for water to exist on planets orbiting cooler stars. Climate modeling from 2013 supports the idea that red dwarf stars can support planets with relatively constant temperatures over their surfaces despite tidal locking. Astronomy professor Eric Agol argues that even white dwarfs may support a relatively brief habitable zone through planetary migration. At the same time, others have written in similar support of semi-stable, temporary habitable zones around brown dwarfs. Also, a habitable zone in the outer parts of stellar systems may exist during the pre-main-sequence phase of stellar evolution, especially around M-dwarfs, potentially lasting for billion-year timescales. Circumstellar habitable zones change over time with stellar evolution. For example, hot O-type stars, which may remain on the main sequence for fewer than 10 million years, would have rapidly changing habitable zones not conducive to the development of life. Red dwarf stars, on the other hand, which can live for hundreds of billions of years on the main sequence, would have planets with ample time for life to develop and evolve. Even while stars are on the main sequence, though, their energy output steadily increases, pushing their habitable zones farther out; the Sun, for example, was 75% as bright in the Archaean as it is now, and in the future, continued increases in energy output will put Earth outside the Sun's habitable zone, even before it reaches the red giant phase. In order to deal with this increase in luminosity, the concept of a continuously habitable zone has been introduced. As the name suggests, the continuously habitable zone is a region around a star in which planetary-mass bodies can sustain liquid water for a given period. Like the general circumstellar habitable zone, the continuously habitable zone of a star is divided into a conservative and extended region. In red dwarf systems, gigantic stellar flares which could double a star's brightness in minutes and huge starspots which can cover 20% of the star's surface area, have the potential to strip an otherwise habitable planet of its atmosphere and water. As with more massive stars, though, stellar evolution changes their nature and energy flux, so by about 1.2 billion years of age, red dwarfs generally become sufficiently constant to allow for the development of life. Once a star has evolved sufficiently to become a red giant, its circumstellar habitable zone will change dramatically from its main-sequence size. For example, the Sun is expected to engulf the previously habitable Earth as a red giant. However, once a red giant star reaches the horizontal branch, it achieves a new equilibrium and can sustain a new circumstellar habitable zone, which in the case of the Sun would range from 7 to 22 AU. At such stage, Saturn's moon Titan would likely be habitable in Earth's temperature sense. Given that this new equilibrium lasts for about 1 Gyr, and because life on Earth emerged by 0.7 Gyr from the formation of the Solar System at latest, life could conceivably develop on planetary mass objects in the habitable zone of red giants. However, around such a helium-burning star, important life processes like photosynthesis could only happen around planets where the atmosphere has carbon dioxide, as by the time a solar-mass star becomes a red giant, planetary-mass bodies would have already absorbed much of their free carbon dioxide. Moreover, as Ramirez and Kaltenegger (2016) showed, intense stellar winds would completely remove the atmospheres of such smaller planetary bodies, rendering them uninhabitable anyway. Thus, Titan would not be habitable even after the Sun becomes a red giant. Nevertheless, life need not originate during this stage of stellar evolution for it to be detected. Once the star becomes a red giant, and the habitable zone extends outward, the icy surface would melt, forming a temporary atmosphere that can be searched for signs of life that may have been thriving before the start of the red giant stage. A planet's atmospheric conditions influence its ability to retain heat so that the location of the habitable zone is also specific to each type of planet: desert planets (also known as dry planets), with very little water, will have less water vapor in the atmosphere than Earth and so have a reduced greenhouse effect, meaning that a desert planet could maintain oases of water closer to its star than Earth is to the Sun. The lack of water also means there is less ice to reflect heat into space, so the outer edge of desert-planet habitable zones is further out. A planet cannot have a hydrosphere—a key ingredient for the formation of carbon-based life—unless there is a source for water within its stellar system. The origin of water on Earth is still not completely understood; possible sources include the result of impacts with icy bodies, outgassing, mineralization, leakage from hydrous minerals from the lithosphere, and photolysis. For an extrasolar system, an icy body from beyond the frost line could migrate into the habitable zone of its star, creating an ocean planet with seas hundreds of kilometers deep such as GJ 1214 b or Kepler-22b may be. Maintenance of liquid surface water also requires a sufficiently thick atmosphere. Possible origins of terrestrial atmospheres are currently theorized to outgassing, impact degassing, and ingassing. Atmospheres are thought to be maintained through similar processes along with biogeochemical cycles and the mitigation of atmospheric escape. In a 2013 study led by Italian astronomer Giovanni Vladilo, it was shown that the size of the circumstellar habitable zone increased with greater atmospheric pressure. Below an atmospheric pressure of about 15 millibars, it was found that habitability could not be maintained because even a small shift in pressure or temperature could render water unable to form as a liquid. Although traditional definitions of the habitable zone assume that carbon dioxide and water vapor are the most important greenhouse gases (as they are on the Earth), a study led by Ramses Ramirez and co-author Lisa Kaltenegger has shown that the size of the habitable zone is greatly increased if prodigious volcanic outgassing of hydrogen is also included along with the carbon dioxide and water vapor. The outer edge in the Solar System would extend out as far as 2.4 AU in that case. Similar increases in the size of the habitable zone were computed for other stellar systems. An earlier study by Ray Pierrehumbert and Eric Gaidos had eliminated the CO2-H2O concept entirely, arguing that young planets could accrete many tens to hundreds of bars of hydrogen from the protoplanetary disc, providing enough of a greenhouse effect to extend the outer edge of the Solar System to 10 AU. In this case, though, the hydrogen is not continuously replenished by volcanism and is lost within millions to tens of millions of years. In the case of planets orbiting in the HZs of red dwarf stars, the extremely close distances to the stars cause tidal locking, an important factor in habitability. For a tidally locked planet, the sidereal day is as long as the orbital period, causing one side to permanently face the host star and the other side to face away. In the past, such tidal locking was thought to cause extreme heat on the star-facing side and bitter cold on the opposite side, making many red dwarf planets uninhabitable; however, three-dimensional climate models in 2013 showed that the side of a red dwarf planet facing the host star could have extensive cloud cover, increasing its bond albedo and reducing significantly temperature differences between the two sides. Planetary mass natural satellites have the potential to be habitable as well. However, these bodies need to fulfill additional parameters, in particular being located within the circumplanetary habitable zones of their host planets. More specifically, moons need to be far enough from their host giant planets that they are not transformed by tidal heating into volcanic worlds like Io, but must remain within the Hill radius of the planet so that they are not pulled out of the orbit of their host planet. Red dwarfs that have masses less than 20% of that of the Sun cannot have habitable moons around giant planets, as the small size of the circumstellar habitable zone would put a habitable moon so close to the star that it would be stripped from its host planet. In such a system, a moon close enough to its host planet to maintain its orbit would have tidal heating so intense as to eliminate any prospects of habitability. A planetary object that orbits a star with high orbital eccentricity may spend only some of its year in the HZ and experience a large variation in temperature and atmospheric pressure. This would result in dramatic seasonal phase shifts where liquid water may exist only intermittently. It is possible that subsurface habitats could be insulated from such changes and that extremophiles on or near the surface might survive through adaptions such as hibernation (cryptobiosis) and/or hyperthermostability. Tardigrades, for example, can survive in a dehydrated state temperature between 0.150 K (−273 °C) and 424 K (151 °C). Life on a planetary object orbiting outside HZ might hibernate on the cold side as the planet approaches the apastron where the planet is coolest and become active on approach to the periastron when the planet is sufficiently warm. Extrasolar discoveries A 2015 review concluded that the exoplanets Kepler-62f, Kepler-186f and Kepler-442b were likely the best candidates for being potentially habitable. These are at a distance of 990, 490 and 1,120 light-years away, respectively. Of these, Kepler-186f is closest in size to Earth with 1.2 times Earth's radius, and it is located towards the outer edge of the habitable zone around its red dwarf star. Among nearest terrestrial exoplanet candidates, Tau Ceti e is 11.9 light-years away. It is in the inner edge of its planetary system's habitable zone, giving it an estimated average surface temperature of 68 °C (154 °F). Studies that have attempted to estimate the number of terrestrial planets within the circumstellar habitable zone tend to reflect the availability of scientific data. A 2013 study by Ravi Kumar Kopparapu put ηe, the fraction of stars with planets in the HZ, at 0.48, meaning that there may be roughly 95–180 billion habitable planets in the Milky Way. However, this is merely a statistical prediction; only a small fraction of these possible planets have yet been discovered. Previous studies have been more conservative. In 2011, Seth Borenstein concluded that there are roughly 500 million habitable planets in the Milky Way. NASA's Jet Propulsion Laboratory 2011 study, based on observations from the Kepler mission, raised the number somewhat, estimating that about "1.4 to 2.7 percent" of all stars of spectral class F, G, and K are expected to have planets in their HZs. The first discoveries of extrasolar planets in the HZ occurred just a few years after the first extrasolar planets were discovered. However, these early detections were all gas giant-sized, and many were in eccentric orbits. Despite this, studies indicate the possibility of large, Earth-like moons around these planets supporting liquid water. One of the first discoveries was 70 Virginis b, a gas giant initially nicknamed "Goldilocks" due to it being neither "too hot" nor "too cold". Later study revealed temperatures analogous to Venus, ruling out any potential for liquid water. 16 Cygni Bb, also discovered in 1996, has an extremely eccentric orbit that spends only part of its time in the HZ, such an orbit would causes extreme seasonal effects. In spite of this, simulations have suggested that a sufficiently large companion could support surface water year-round. Gliese 876 b, discovered in 1998, and Gliese 876 c, discovered in 2001, are both gas giants discovered in the habitable zone around Gliese 876 that may also have large moons. Another gas giant, Upsilon Andromedae d was discovered in 1999 orbiting Upsilon Andromidae's habitable zone. Announced on April 4, 2001, HD 28185 b is a gas giant found to orbit entirely within its star's circumstellar habitable zone and has a low orbital eccentricity, comparable to that of Mars in the Solar System. Tidal interactions suggest it could harbor habitable Earth-mass satellites in orbit around it for many billions of years, though it is unclear whether such satellites could form in the first place. HD 69830 d, a gas giant with 17 times the mass of Earth, was found in 2006 orbiting within the circumstellar habitable zone of HD 69830, 41 light years away from Earth. The following year, 55 Cancri f was discovered within the HZ of its host star 55 Cancri A. Hypothetical satellites with sufficient mass and composition are thought to be able to support liquid water at their surfaces. Though, in theory, such giant planets could possess moons, the technology did not exist to detect moons around them, and no extrasolar moons had been discovered. Planets within the zone with the potential for solid surfaces were therefore of much higher interest. The 2007 discovery of Gliese 581c, the first super-Earth in the circumstellar habitable zone, created significant interest in the system by the scientific community, although the planet was later found to have extreme surface conditions that may resemble Venus. Gliese 581 d, another planet in the same system and thought to be a better candidate for habitability, was also announced in 2007. Its existence was later disconfirmed in 2014, but only for a short time. As of 2015, the planet has no newer disconfirmations. Gliese 581 g, yet another planet thought to have been discovered in the circumstellar habitable zone of the system, was considered to be more habitable than both Gliese 581 c and d. However, its existence was also disconfirmed in 2014, and astronomers are divided about its existence. Discovered in August 2011, HD 85512 b was initially speculated to be habitable, but the new circumstellar habitable zone criteria devised by Kopparapu et al. in 2013 place the planet outside the circumstellar habitable zone. Kepler-22 b, discovered in December 2011 by the Kepler space probe, is the first transiting exoplanet discovered around a Sun-like star. With a radius 2.4 times that of Earth, Kepler-22b has been predicted by some to be an ocean planet. Gliese 667 Cc, discovered in 2011 but announced in 2012, is a super-Earth orbiting in the circumstellar habitable zone of Gliese 667 C. It is one of the most Earth-like planets known. Gliese 163 c, discovered in September 2012 in orbit around the red dwarf Gliese 163 is located 49 light years from Earth. The planet has 6.9 Earth masses and 1.8–2.4 Earth radii, and with its close orbit receives 40 percent more stellar radiation than Earth, leading to surface temperatures of about 60° C. HD 40307 g, a candidate planet tentatively discovered in November 2012, is in the circumstellar habitable zone of HD 40307. In December 2012, Tau Ceti e and Tau Ceti f were found in the circumstellar habitable zone of Tau Ceti, a Sun-like star 12 light years away. Although more massive than Earth, they are among the least massive planets found to date orbiting in the habitable zone; however, Tau Ceti f, like HD 85512 b, did not fit the new circumstellar habitable zone criteria established by the 2013 Kopparapu study. It is now considered as uninhabitable. Recent discoveries have uncovered planets that are thought to be similar in size or mass to Earth. "Earth-sized" ranges are typically defined by mass. The lower range used in many definitions of the super-Earth class is 1.9 Earth masses; likewise, sub-Earths range up to the size of Venus (~0.815 Earth masses). An upper limit of 1.5 Earth radii is also considered, given that above 1.5 R🜨 the average planet density rapidly decreases with increasing radius, indicating these planets have a significant fraction of volatiles by volume overlying a rocky core. A genuinely Earth-like planet – an Earth analog or "Earth twin" – would need to meet many conditions beyond size and mass; such properties are not observable using current technology. A solar analog (or "solar twin") is a star that resembles the Sun. No solar twin with an exact match as that of the Sun has been found. However, some stars are nearly identical to the Sun and are considered solar twins. An exact solar twin would be a G2V star with a 5,778 K temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation. Stars with an age of 4.6 billion years are at the most stable state. Proper metallicity and size are also critical to low luminosity variation. Using data collected by NASA's Kepler space telescope and the W. M. Keck Observatory, scientists have estimated that 22% of solar-type stars in the Milky Way galaxy have Earth-sized planets in their habitable zone. On 7 January 2013, astronomers from the Kepler team announced the discovery of Kepler-69c (formerly KOI-172.02), an Earth-size exoplanet candidate (1.7 times the radius of Earth) orbiting Kepler-69, a star similar to the Sun, in the HZ and expected to offer habitable conditions. The discovery of two planets orbiting in the habitable zone of Kepler-62, by the Kepler team was announced on April 19, 2013. The planets, named Kepler-62e and Kepler-62f, are likely solid planets with sizes 1.6 and 1.4 times the radius of Earth, respectively. With a radius estimated at 1.1 Earth, Kepler-186f, discovery announced in April 2014, is the closest yet size to Earth of an exoplanet confirmed by the transit method though its mass remains unknown and its parent star is not a Solar analog. Kapteyn b, discovered in June 2014, was thought to is a possible rocky world of about 4.8 Earth masses and about 1.5 Earth radii orbiting the habitable zone of the red subdwarf Kapteyn's Star, 12.8 light-years away. However, further analysis concluded that this claim was an artefact of stellar rotation and activity. On 6 January 2015, NASA announced the 1000th confirmed exoplanet discovered by the Kepler Space Telescope. Three of the newly confirmed exoplanets were found to orbit within habitable zones of their related stars: two of the three, Kepler-438b and Kepler-442b, are near-Earth-size and likely rocky; the third, Kepler-440b, is a super-Earth. However, Kepler-438b is found to be a subject of powerful flares, so it is now considered uninhabitable. 16 January, K2-3d a planet of 1.5 Earth radii was found orbiting within the habitable zone of K2-3, receiving 1.4 times the intensity of visible light as Earth. Kepler-452b, announced on 23 July 2015 is 50% bigger than Earth, likely rocky and takes approximately 385 Earth days to orbit the habitable zone of its G-class (solar analog) star Kepler-452. The discovery of a system of three tidally locked planets orbiting the habitable zone of an ultracool dwarf star, TRAPPIST-1, was announced in May 2016. The discovery is considered significant because it dramatically increases the possibility of smaller, cooler, more numerous and closer stars possessing habitable planets. Two potentially habitable planets, discovered by the K2 mission in July 2016 orbiting around the M dwarf K2-72 around 227 light years from the Sun: K2-72c and K2-72e are both of similar size to Earth and receive similar amounts of stellar radiation. Announced on the 20 April 2017, LHS 1140b is a super-dense super-Earth 39 light years away, 6.6 times Earth's mass and 1.4 times radius, its star 15% the mass of the Sun but with much less observable stellar flare activity than most M dwarfs. The planet is one of few observable by both transit and radial velocity that's mass is confirmed with an atmosphere may be studied. Discovered by radial velocity in June 2017, with approximately three times the mass of Earth, Luyten b orbits within the habitable zone of Luyten's Star just 12.2 light-years away. At 11 light-years away, the second closest planet, Ross 128 b, was announced in November 2017 following a decade's radial velocity study of relatively "quiet" red dwarf star Ross 128. At 1.35 times Earth's mass, is it roughly Earth-sized and likely rocky in composition. Discovered in March 2018, K2-155d is about 1.64 times the radius of Earth, is likely rocky and orbits in the habitable zone of its red dwarf star 203 light years away. One of the earliest discoveries by the Transiting Exoplanet Survey Satellite (TESS) announced on July 31, 2019, is a Super-Earth planet GJ 357 d orbiting the outer edge of a red dwarf 31 light years away. K2-18b is an exoplanet 124 light-years away, orbiting in the habitable zone of the K2-18, a red dwarf. This planet is significant for water vapor found in its atmosphere; this was announced on September 17, 2019. In September 2020, astronomers identified 24 superhabitable planet (planets better than Earth) contenders, from among more than 4000 confirmed exoplanets at present, based on astrophysical parameters, as well as the natural history of known life forms on the Earth. Habitability outside the HZ Liquid-water environments have been found to exist in the absence of atmospheric pressure and at temperatures outside the HZ temperature range. For example, Saturn's moons Titan and Enceladus and Jupiter's moons Europa and Ganymede, all of which are outside the habitable zone, may hold large volumes of liquid water in subsurface oceans. Outside the HZ, tidal heating and radioactive decay are two possible heat sources that could contribute to the existence of liquid water. Abbot and Switzer (2011) put forward the possibility that subsurface water could exist on rogue planets as a result of radioactive decay-based heating and insulation by a thick surface layer of ice. With some theorising that life on Earth may have actually originated in stable, subsurface habitats, it has been suggested that it may be common for wet subsurface extraterrestrial habitats such as these to 'teem with life'. On Earth itself, living organisms may be found more than 6 km (3.7 mi) below the surface. Another possibility is that outside the HZ organisms may use alternative biochemistries that do not require water at all. Astrobiologist Christopher McKay, has suggested that methane (CH4) may be a solvent conducive to the development of "cryolife", with the Sun's "methane habitable zone" being centered on 1,610,000,000 km (1.0×109 mi; 11 AU) from the star. This distance is coincident with the location of Titan, whose lakes and rain of methane make it an ideal location to find McKay's proposed cryolife. In addition, testing of a number of organisms has found some are capable of surviving in extra-HZ conditions. Significance for complex and intelligent life The Rare Earth hypothesis argues that complex and intelligent life is uncommon and that the HZ is one of many critical factors. According to Ward & Brownlee (2004) and others, not only is a HZ orbit and surface water a primary requirement to sustain life but a requirement to support the secondary conditions required for multicellular life to emerge and evolve. The secondary habitability factors are both geological (the role of surface water in sustaining necessary plate tectonics) and biochemical (the role of radiant energy in supporting photosynthesis for necessary atmospheric oxygenation). But others, such as Ian Stewart and Jack Cohen in their 2002 book Evolving the Alien argue that complex intelligent life may arise outside the HZ. Intelligent life outside the HZ may have evolved in subsurface environments, from alternative biochemistries or even from nuclear reactions. On Earth, several complex multicellular life forms (or eukaryotes) have been identified with the potential to survive conditions that might exist outside the conservative habitable zone. Geothermal energy sustains ancient circumvent ecosystems, supporting large complex life forms such as Riftia pachyptila. Similar environments may be found in oceans pressurised beneath solid crusts, such as those of Europa and Enceladus, outside of the habitable zone. Numerous microorganisms have been tested in simulated conditions and in low Earth orbit, including eukaryotes. An animal example is the Milnesium tardigradum, which can withstand extreme temperatures well above the boiling point of water and the cold vacuum of outer space. A desert moss, Syntrichia caninervis is one of few plants believed capable of surviving on Mars. In addition, the lichens Rhizocarpon geographicum and Rusavskia elegans have been found to survive in an environment where the atmospheric pressure is far too low for surface liquid water and where the radiant energy is also much lower than that which most plants require to photosynthesize. The fungi Cryomyces antarcticus and Cryomyces minteri are also able to survive and reproduce in Mars-like conditions. Species, including humans, known to possess animal cognition require large amounts of energy, and have adapted to specific conditions, including an abundance of atmospheric oxygen and the availability of large quantities of chemical energy synthesized from radiant energy. If humans are to colonize other planets, true Earth analogs in the HZ are most likely to provide the closest natural habitat; this concept was the basis of Stephen H. Dole's 1964 study. With suitable temperature, gravity, atmospheric pressure and the presence of water, the necessity of spacesuits or space habitat analogs on the surface may be eliminated, and complex Earth life can thrive. Planets in the HZ remain of paramount interest to researchers looking for intelligent life elsewhere in the universe. The Drake equation, sometimes used to estimate the number of intelligent civilizations in our galaxy, contains the factor or parameter ne, which is the average number of planetary-mass objects orbiting within the HZ of each star. A low value lends support to the Rare Earth hypothesis, which posits that intelligent life is a rarity in the Universe, whereas a high value provides evidence for the Copernican mediocrity principle, the view that habitability—and therefore life—is common throughout the Universe. A 1971 NASA report by Drake and Bernard Oliver proposed the "water hole", based on the spectral absorption lines of the hydrogen and hydroxyl components of water, as a good, obvious band for communication with extraterrestrial intelligence that has since been widely adopted by astronomers involved in the search for extraterrestrial intelligence. According to Jill Tarter, Margaret Turnbull and many others, HZ candidates are the priority targets to narrow waterhole searches and the Allen Telescope Array now extends Project Phoenix to such candidates. Because the HZ is considered the most likely habitat for intelligent life, METI efforts have also been focused on systems likely to have planets there. The 2001 Teen Age Message and 2003 Cosmic Call 2, for example, were sent to the 47 Ursae Majoris system, known to contain three Jupiter-mass planets and possibly with a terrestrial planet in the HZ. The Teen Age Message was also directed to the 55 Cancri system, which has a gas giant in its HZ. A Message from Earth in 2008, and Hello From Earth in 2009, were directed to the Gliese 581 system, containing three planets in the HZ—Gliese 581 c, d, and the unconfirmed g. See also References External links |
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Contents String (computer science) In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable. The latter may allow its elements to be mutated and the length changed, or it may be fixed (after creation). A string is often implemented as an array data structure of bytes (or words) that stores a sequence of elements, typically characters, using some character encoding. More general, string may also denote a sequence (or list) of data other than just characters. Depending on the programming language and precise data type used, a variable declared to be a string may either cause storage in memory to be statically allocated for a predetermined maximum length or employ dynamic allocation to allow it to hold a variable number of elements. When a string appears literally in source code, it is known as a string literal or an anonymous string. In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set called an alphabet. Purpose A primary purpose of strings is to store human-readable text, like words and sentences. Strings are used to communicate information from a computer program to the user of the program. A program may also accept string input from its user. Further, strings may store data expressed as characters yet not intended for human reading. Example strings and their purposes: The term string may also designate a sequence of data or computer records other than characters — like a "string of bits" — but when used without qualification it refers to strings of characters. History Use of the word "string" to mean any items arranged in a line, series or succession dates back centuries. In 19th-century typesetting, compositors used the term "string" to denote a length of type printed on paper; the string would be measured to determine the compositor's pay. Use of the word "string" to mean "a sequence of symbols or linguistic elements in a definite order" emerged from mathematics, symbolic logic, and linguistic theory to speak about the formal behavior of symbolic systems, setting aside the symbols' meaning. For example, logician C. I. Lewis wrote in 1918: A mathematical system is any set of strings of recognisable marks in which some of the strings are taken initially and the remainder derived from these by operations performed according to rules which are independent of any meaning assigned to the marks. That a system should consist of 'marks' instead of sounds or odours is immaterial. According to Jean E. Sammet, "the first realistic string handling and pattern matching language" for computers was COMIT in the 1950s, followed by the SNOBOL language of the early 1960s. String datatypes A string datatype is a datatype modeled on the idea of a formal string. Strings are such an important and useful datatype that they are implemented in nearly every programming language. In some languages they are available as primitive types and in others as composite types. The syntax of most high-level programming languages allows for a string, usually quoted in some way, to represent an instance of a string datatype; such a meta-string is called a literal or string literal. Although formal strings can have an arbitrary finite length, the length of strings in real languages is often constrained to an artificial maximum. In general, there are two types of string datatypes: fixed-length strings, which have a fixed maximum length to be determined at compile time and which use the same amount of memory whether this maximum is needed or not, and variable-length strings, whose length is not arbitrarily fixed and which can use varying amounts of memory depending on the actual requirements at run time (see Memory management). Most strings in modern programming languages are variable-length strings. Of course, even variable-length strings are limited in length by the amount of available memory. The string length can be stored as a separate integer (which may put another artificial limit on the length) or implicitly through a termination character, usually a character value with all bits zero such as in C programming language. See also "Null-terminated" below. String datatypes have historically allocated one byte per character, and, although the exact character set varied by region, character encodings were similar enough that programmers could often get away with ignoring this, since characters a program treated specially (such as period and space and comma) were in the same place in all the encodings a program would encounter. These character sets were typically based on ASCII or EBCDIC. If text in one encoding was displayed on a system using a different encoding, text was often mangled, though often somewhat readable and some computer users learned to read the mangled text. Logographic languages such as Chinese, Japanese, and Korean (known collectively as CJK) need far more than 256 characters (the limit of a one 8-bit byte per-character encoding) for reasonable representation. The normal solutions involved keeping single-byte representations for ASCII and using two-byte representations for CJK ideographs. Use of these with existing code led to problems with matching and cutting of strings, the severity of which depended on how the character encoding was designed. Some encodings such as the EUC family guarantee that a byte value in the ASCII range will represent only that ASCII character, making the encoding safe for systems that use those characters as field separators. Other encodings such as ISO-2022 and Shift-JIS do not make such guarantees, making matching on byte codes unsafe. These encodings also were not "self-synchronizing", so that locating character boundaries required backing up to the start of a string, and pasting two strings together could result in corruption of the second string. Unicode has simplified the picture somewhat. Most programming languages now have a datatype for Unicode strings. Unicode's preferred byte stream format UTF-8 is designed not to have the problems described above for older multibyte encodings. UTF-8, UTF-16 and UTF-32 require the programmer to know that the fixed-size code units are different from the "characters", the main difficulty currently is incorrectly designed APIs that attempt to hide this difference (UTF-32 does make code points fixed-sized, but these are not "characters" due to composing codes). Some languages, such as C++, Perl and Ruby, normally allow the contents of a string to be changed after it has been created; these are termed mutable strings. In other languages, such as Java, JavaScript, Lua, Python, and Go, the value is fixed and a new string must be created if any alteration is to be made; these are termed immutable strings. Some of these languages with immutable strings also provide another type that is mutable, such as Java and .NET's StringBuilder, the thread-safe Java StringBuffer, and the Cocoa NSMutableString. Immutability brings advantages and disadvantages: while immutable strings may require inefficiently creating many copies, they are simpler and fully thread-safe. Strings are typically implemented as arrays of bytes, characters, or code units, to allow fast access to individual units or substrings, including characters when they have a fixed length. A few languages such as Haskell implement them as linked lists instead. Many high-level languages provide strings as a primitive data type, such as JavaScript and PHP, while most others provide them as a composite data type, some with special language support in writing literals, for example, Java and C#. Some languages, such as C, Prolog and Erlang, avoid implementing a dedicated string datatype at all, instead adopting the convention of representing strings as lists of character codes. Even in programming languages having a dedicated string type, strings can usually be iterated as a sequence of character codes, like lists of integers or other values. Representations of strings depend heavily on the choice of character repertoire and the method of character encoding. Older string implementations were designed to work with repertoire and encoding defined by ASCII, or more recent extensions like the ISO 8859 series. Modern implementations often use the extensive repertoire defined by Unicode along with a variety of complex encodings such as UTF-8 and UTF-16. The term byte string usually indicates a general-purpose string of bytes, rather than strings of only (readable) characters, strings of bits, or such. Byte strings often imply that bytes can take any value and any data can be stored as-is, meaning that there should be no value interpreted as a termination value. Most string implementations are very similar to variable-length arrays with the entries storing the character codes of corresponding characters. The principal difference is that, with certain encodings, a single logical character may take up more than one entry in the array. This happens, for example, with UTF-8, where single codes (UCS code points) can take anywhere from one to four bytes, and single characters can take an arbitrary number of codes. In these cases, the logical length of the string (number of characters) differs from the physical length of the array (number of bytes in use). UTF-32 avoids the first part of the problem. The length of a string can be stored in a dope vector, separate from the storage holding the actual characters. The IBM PL/I (F) compiler used a string dope vector (SDV) for variable-length strings and for passing string parameters. The SDV contains a current length and a maximum length, and is not adjacent to the string proper. After PL/I (F), IBM dropped the SDV in favor of length-prefixed strings. The length of a string can be stored implicitly by using a special terminating character; often this is the null character (NUL), which has all bits zero, a convention used and perpetuated by the popular C programming language. Hence, this representation is commonly referred to as a C string. This representation of an n-character string takes n + 1 space (1 for the terminator), and is thus an implicit data structure. In terminated strings, the terminating code is not an allowable character in any string. Strings with length field do not have this limitation and can also store arbitrary binary data. An example of a null-terminated string stored in a 10-byte buffer, along with its ASCII (or more modern UTF-8) representation as 8-bit hexadecimal numbers is: The length of the string in the above example, "FRANK", is 5 characters, but it occupies 6 bytes. Characters after the terminator do not form part of the representation; they may be either part of other data or just garbage. (Strings of this form are sometimes called ASCIZ strings, after the original assembly language directive used to declare them.) Using a special byte other than null for terminating strings has historically appeared in both hardware[a] and software, though sometimes with a value that was also a printing character. $ was used by many assembler systems, : used by CDC systems (this character had a value of zero), and the ZX80 used " since this was the string delimiter in its BASIC language. Somewhat similar, "data processing" machines like the IBM 1401 used a special word mark bit to delimit strings at the left, where the operation would start at the right. This bit had to be clear in all other parts of the string. This meant that, while the IBM 1401 had a seven-bit word, almost no-one ever thought to use this as a feature, and override the assignment of the seventh bit to (for example) handle ASCII codes. Early microcomputer software relied upon the fact that ASCII codes do not use the high-order bit, and set it to indicate the end of a string. It must be reset to 0 prior to output. The length of a string can also be stored explicitly, for example by prefixing the string with the length as a byte value. This convention is used in many Pascal dialects; as a consequence, some people call such a string a Pascal string or P-string. Storing the string length as byte limits the maximum string length to 255. To avoid such limitations, improved implementations of P-strings use 16-, 32-, or 64-bit words to store the string length. When the length field covers the address space, strings are limited only by the available memory. If the length is bounded, then it can be encoded in constant space, typically a machine word, thus leading to an implicit data structure, taking n + k space, where k is the number of characters in a word (8 for 8-bit ASCII on a 64-bit machine, 1 for 32-bit UTF-32/UCS-4 on a 32-bit machine, etc.). If the length is not bounded, encoding a length n takes log(n) space (see fixed-length code), so length-prefixed strings are a succinct data structure, encoding a string of length n in log(n) + n space. In the latter case, the length-prefix field itself does not have fixed length, therefore the actual string data needs to be moved when the string grows such that the length field needs to be increased. Here is a Pascal string stored in a 10-byte buffer, along with its ASCII / UTF-8 representation: Many languages, including object-oriented ones, implement strings as records with an internal structure like: However, since the implementation is usually hidden, the string must be accessed and modified through member functions. text is a pointer to a dynamically allocated memory area, which might be expanded as needed. See also string (C++). Both character termination and length codes limit strings: For example, C character arrays that contain null (NUL) characters cannot be handled directly by C string library functions: Strings using a length code are limited to the maximum value of the length code. Both of these limitations can be overcome by clever programming. It is possible to create data structures and functions that manipulate them that do not have the problems associated with character termination and can in principle overcome length code bounds. It is also possible to optimize the string represented using techniques from run length encoding (replacing repeated characters by the character value and a length) and Hamming encoding[clarification needed]. While these representations are common, others are possible. Using ropes makes certain string operations, such as insertions, deletions, and concatenations more efficient. The core data structure in a text editor is the one that manages the string (sequence of characters) that represents the current state of the file being edited. While that state could be stored in a single long consecutive array of characters, a typical text editor instead uses an alternative representation as its sequence data structure—a gap buffer, a linked list of lines, a piece table, or a rope—which makes certain string operations, such as insertions, deletions, and undoing previous edits, more efficient. The differing memory layout and storage requirements of strings can affect the security of the program accessing the string data. String representations requiring a terminating character are commonly susceptible to buffer overflow problems if the terminating character is not present, caused by a coding error or an attacker deliberately altering the data. String representations adopting a separate length field are also susceptible if the length can be manipulated. In such cases, program code accessing the string data requires bounds checking to ensure that it does not inadvertently access or change data outside of the string memory limits. String data is frequently obtained from user input to a program. As such, it is the responsibility of the program to validate the string to ensure that it represents the expected format. Performing limited or no validation of user input can cause a program to be vulnerable to code injection attacks. Literal strings Sometimes, strings need to be embedded inside a text file that is both human-readable and intended for consumption by a machine. This is needed in, for example, source code of programming languages, or in configuration files. In this case, the NUL character does not work well as a terminator since it is normally invisible (non-printable) and is difficult to input via a keyboard. Storing the string length would also be inconvenient as manual computation and tracking of the length is tedious and error-prone. Two common representations are: Non-text strings While character strings are very common uses of strings, a string in computer science may refer generically to any sequence of homogeneously typed data. A bit string or byte string, for example, may be used to represent non-textual binary data retrieved from a communications medium. This data may or may not be represented by a string-specific datatype, depending on the needs of the application, the desire of the programmer, and the capabilities of the programming language being used. If the programming language's string implementation is not 8-bit clean, data corruption may ensue. C programmers draw a sharp distinction between a "string", aka a "string of characters", which by definition is always null terminated, vs. an "array of characters" which may be stored in the same array but is often not null terminated. Using C string handling functions on such an array of characters often seems to work, but later leads to security problems. String processing algorithms There are many algorithms for processing strings, each with various trade-offs. Competing algorithms can be analyzed with respect to run time, storage requirements, and so forth. The name stringology was coined in 1984 by computer scientist Zvi Galil for the theory of algorithms and data structures used for string processing. Some categories of algorithms include: Advanced string algorithms often employ complex mechanisms and data structures, among them suffix trees and finite-state machines. Character string-oriented languages and utilities Character strings are such a useful datatype that several languages have been designed in order to make string processing applications easy to write. Examples include the following languages: Many Unix utilities perform simple string manipulations and can be used to easily program some powerful string processing algorithms. Files and finite streams may be viewed as strings. Some APIs like Multimedia Control Interface, embedded SQL or printf use strings to hold commands that will be interpreted. Many scripting programming languages, including Perl, Python, Ruby, and Tcl employ regular expressions to facilitate text operations. Perl is particularly noted for its regular expression use, and many other languages and applications implement Perl compatible regular expressions. Some languages such as Perl and Ruby support string interpolation, which permits arbitrary expressions to be evaluated and included in string literals. Character string functions String functions are used to create strings or change the contents of a mutable string. They also are used to query information about a string. The set of functions and their names varies depending on the computer programming language. The most basic example of a string function is the string length function – the function that returns the length of a string (not counting any terminator characters or any of the string's internal structural information) and does not modify the string. This function is often named length, len, or size. For example, length("hello world") would return 11. Another common function is concatenation, where a new string is created by appending two strings, often this is the + addition operator. Some microprocessor's instruction set architectures contain direct support for string operations, such as block copy (e.g. In intel x86m REPNZ MOVSB). Formal theory Let Σ {\displaystyle \Sigma } be a finite set of distinct, unambiguous symbols (alternatively called characters), called the alphabet. A string (or word or expression) over Σ {\displaystyle \Sigma } is any finite sequence of symbols from Σ {\displaystyle \Sigma } . For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} , then 01011 {\displaystyle {\texttt {01011}}} is a string over Σ {\displaystyle \Sigma } . The length of a string s {\displaystyle s} is the number of symbols in s {\displaystyle s} (the length of the sequence) and can be any non-negative integer; it is often denoted as | s | {\displaystyle |s|} . The empty string is the unique string over Σ {\displaystyle \Sigma } of length 0 {\displaystyle 0} , and is denoted ε {\displaystyle \varepsilon } or λ {\displaystyle \lambda } . The set of all strings over Σ {\displaystyle \Sigma } of length n {\displaystyle n} is denoted Σ n {\displaystyle \Sigma ^{n}} . For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} , then Σ 2 = { 00 , 01 , 10 , 11 } {\displaystyle \Sigma ^{2}=\{{\texttt {00}},{\texttt {01}},{\texttt {10}},{\texttt {11}}\}} . We have Σ 0 = { ε } {\displaystyle \Sigma ^{0}=\{\varepsilon \}} for every alphabet Σ {\displaystyle \Sigma } . The set of all strings over Σ {\displaystyle \Sigma } of any length is the Kleene closure of Σ {\displaystyle \Sigma } and is denoted Σ ∗ {\displaystyle \Sigma ^{*}} . In terms of Σ n {\displaystyle \Sigma ^{n}} , For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} , then Σ ∗ = { ε , 0 , 1 , 00 , 01 , 10 , 11 , 000 , 001 , 010 , 011 , . . . } {\displaystyle \Sigma ^{*}=\{\varepsilon ,{\texttt {0}},{\texttt {1}},{\texttt {00}},{\texttt {01}},{\texttt {10}},{\texttt {11}},{\texttt {000}},{\texttt {001}},{\texttt {010}},{\texttt {011}},...\}} . Although the set Σ ∗ {\displaystyle \Sigma ^{*}} itself is countably infinite, each element of Σ ∗ {\displaystyle \Sigma ^{*}} is a string of finite length. A set of strings over Σ {\displaystyle \Sigma } (i.e. any subset of Σ ∗ {\displaystyle \Sigma ^{*}} ) is called a formal language over Σ {\displaystyle \Sigma } . For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} , the set of strings with an even number of zeros, { ε , 1 , 00 , 11 , 001 , 010 , 100 , 111 , 0000 , 0011 , 0101 , 0110 , 1001 , 1010 , 1100 , 1111 , . . . } {\displaystyle \{\varepsilon ,{\texttt {1}},{\texttt {00}},{\texttt {11}},{\texttt {001}},{\texttt {010}},{\texttt {100}},{\texttt {111}},{\texttt {0000}},{\texttt {0011}},{\texttt {0101}},{\texttt {0110}},{\texttt {1001}},{\texttt {1010}},{\texttt {1100}},{\texttt {1111}},...\}} , is a formal language over Σ {\displaystyle \Sigma } . Concatenation is an important binary operation on Σ ∗ {\displaystyle \Sigma ^{*}} . For any two strings s {\displaystyle s} and t {\displaystyle t} in Σ ∗ {\displaystyle \Sigma ^{*}} , their concatenation is defined as the sequence of symbols in s {\displaystyle s} followed by the sequence of characters in t {\displaystyle t} , and is denoted s t {\displaystyle st} . For example, if Σ = { a , b , . . . , z } {\displaystyle \Sigma =\{{\texttt {a}},{\texttt {b}},...,{\texttt {z}}\}} (i.e. the lowercase English alphabet), s = bear {\displaystyle s={\texttt {bear}}} , and t = hug {\displaystyle t={\texttt {hug}}} , then s t = bearhug {\displaystyle st={\texttt {bearhug}}} and t s = hugbear {\displaystyle ts={\texttt {hugbear}}} . String concatenation is an associative, but non-commutative operation. The empty string ε {\displaystyle \varepsilon } serves as the identity element; for any string s {\displaystyle s} , ε s = s ε = s {\displaystyle \varepsilon s=s\varepsilon =s} . Therefore, the set Σ ∗ {\displaystyle \Sigma ^{*}} and the concatenation operation form a monoid, the free monoid generated by Σ {\displaystyle \Sigma } . In addition, the length function defines a monoid homomorphism from Σ ∗ {\displaystyle \Sigma ^{*}} to the non-negative integers (that is, a function L : Σ ∗ ↦ N ∪ { 0 } {\displaystyle L:\Sigma ^{*}\mapsto \mathbb {N} \cup \{0\}} , such that L ( s t ) = L ( s ) + L ( t ) ∀ s , t ∈ Σ ∗ {\displaystyle L(st)=L(s)+L(t)\quad \forall s,t\in \Sigma ^{*}} ). A string s {\displaystyle s} is said to be a substring or factor of t {\displaystyle t} if there exist (possibly empty) strings u {\displaystyle u} and v {\displaystyle v} such that t = u s v {\displaystyle t=usv} . The relation "is a substring of" defines a partial order on Σ ∗ {\displaystyle \Sigma ^{*}} , the least element of which is the empty string. A string s {\displaystyle s} is said to be a prefix of t {\displaystyle t} if there exists a string s {\displaystyle s} such that t = s u {\displaystyle t=su} . If u {\displaystyle u} is nonempty, s {\displaystyle s} is said to be a proper prefix of t {\displaystyle t} . Symmetrically, a string s {\displaystyle s} is said to be a suffix of t {\displaystyle t} if there exists a string u {\displaystyle u} such that t = u s {\displaystyle t=us} . If u {\displaystyle u} is nonempty, s {\displaystyle s} is said to be a proper suffix of t {\displaystyle t} . Suffixes and prefixes are substrings of t {\displaystyle t} . Both the relations "is a prefix of" and "is a suffix of" are prefix orders. The reverse of a string is a string with the same symbols but in reverse order. For example, if s = abc {\displaystyle s={\texttt {abc}}} (where a {\displaystyle {\texttt {a}}} , b {\displaystyle {\texttt {b}}} , and c {\displaystyle {\texttt {c}}} are symbols of the alphabet), then the reverse of s {\displaystyle s} is cba {\displaystyle {\texttt {cba}}} . A string that is the reverse of itself (e.g., s = madam {\displaystyle s={\texttt {madam}}} ) is called a palindrome, which also includes the empty string and all strings of length 1 {\displaystyle 1} . A string s = u v {\displaystyle s=uv} is said to be a rotation of t {\displaystyle t} if t = v u {\displaystyle t=vu} . For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} the string 0011001 {\displaystyle {\texttt {0011001}}} is a rotation of 0100110 {\displaystyle {\texttt {0100110}}} , where u = 00110 {\displaystyle u={\texttt {00110}}} and v = 01 {\displaystyle v={\texttt {01}}} . As another example, the string abc {\displaystyle {\texttt {abc}}} has three different rotations, viz. abc {\displaystyle {\texttt {abc}}} itself (with u = abc {\displaystyle u={\texttt {abc}}} , v = ε {\displaystyle v=\varepsilon } ), bca {\displaystyle {\texttt {bca}}} (with u = bc , v = a {\displaystyle u={\texttt {bc}},v={\texttt {a}}} ), and cab {\displaystyle {\texttt {cab}}} (with u = c , v = ab {\displaystyle u={\texttt {c}},v={\texttt {ab}}} ). It is often useful to define an ordering on a set of strings. If the alphabet Σ {\displaystyle \Sigma } has a total order (cf. alphabetical order) one can define a total order on Σ ∗ {\displaystyle \Sigma ^{*}} called lexicographical order. The lexicographical order is total if the alphabetical order is, but is not well-founded for any nontrivial alphabet, even if the alphabetical order is. For example, if Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} and 0 < 1 {\displaystyle {\texttt {0}}<{\texttt {1}}} , then the lexicographical order on Σ ∗ {\displaystyle \Sigma ^{*}} includes the relationships ε < 0 < 00 < 000 < . . . < 0001 < . . . < 001 < . . . < 01 < 010 < . . . < 011 < 0110 < . . . < 01111 < . . . < 1 < 10 < 100 < . . . < 101 < . . . < 111 < . . . < 1111 < . . . < 11111 . . . {\displaystyle \varepsilon <{\texttt {0}}<{\texttt {00}}<{\texttt {000}}<...<{\texttt {0001}}<...<{\texttt {001}}<...<{\texttt {01}}<{\texttt {010}}<...<{\texttt {011}}<{\texttt {0110}}<...<{\texttt {01111}}<...<{\texttt {1}}<{\texttt {10}}<{\texttt {100}}<...<{\texttt {101}}<...<{\texttt {111}}<...<{\texttt {1111}}<...<{\texttt {11111}}...} With respect to this ordering, e.g. the infinite set { 1 , 01 , 001 , 0001 , 00001 , 000001 , . . . } {\displaystyle \{{\texttt {1}},{\texttt {01}},{\texttt {001}},{\texttt {0001}},{\texttt {00001}},{\texttt {000001}},...\}} has no minimal element. See Shortlex for an alternative string ordering that preserves well-foundedness. For the example alphabet, the shortlex order is ε < 0 < 1 < 00 < 01 < 10 < 11 < 000 < 001 < 010 < 011 < 100 < 101 < 0110 < 111 < 0000 < 0001 < 0010 < 0011 < . . . < 1111 < 00000 < 00001 . . . {\displaystyle \varepsilon <{\texttt {0}}<{\texttt {1}}<{\texttt {00}}<{\texttt {01}}<{\texttt {10}}<{\texttt {11}}<{\texttt {000}}<{\texttt {001}}<{\texttt {010}}<{\texttt {011}}<{\texttt {100}}<{\texttt {101}}<{\texttt {0110}}<{\texttt {111}}<{\texttt {0000}}<{\texttt {0001}}<{\texttt {0010}}<{\texttt {0011}}<...<{\texttt {1111}}<{\texttt {00000}}<{\texttt {00001}}...} A number of additional operations on strings commonly occur in the formal theory. These are given in the article on string operations. Strings admit the following interpretation as nodes on a graph, where k {\displaystyle k} is the number of symbols in Σ {\displaystyle \Sigma } : The natural topology on the set of fixed-length strings or variable-length strings is the discrete topology, but the natural topology on the set of infinite strings is the limit topology, viewing the set of infinite strings as the inverse limit of the sets of finite strings. This is the construction used for the p-adic numbers and some constructions of the Cantor set, and yields the same topology. Isomorphisms between string representations of topologies can be found by normalizing according to the lexicographically minimal string rotation. See also Explanatory notes References |
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[SOURCE: https://en.wikipedia.org/wiki/Pizza_(programming_language)] | [TOKENS: 223] |
Contents Pizza (programming language) Pizza is an open-source superset of Java 1.4, prior to the introduction of generics for the Java programming language. In addition to its own solution for adding generics to the language, Pizza also added function pointers and algebraic types with case classes and pattern matching. In August 2001, the developers made a compiler capable of working with Java. Most Pizza applications can run in a Java environment, but certain cases will cause problems. Pizza's last version was released in January 2002. Its main developers turned their focus afterwards to the Generic Java project: another attempt to add generics to Java that was officially adopted as of version 5 of the language. The pattern matching and other functional programming-like features have been further developed in the Scala programming language. Martin Odersky remarked, "we wanted to integrate the functional and object-oriented parts in a cleaner way than what we were able to achieve before with the Pizza language. [...] In Pizza we did a clunkier attempt, and in Scala I think we achieved a much smoother integration between the two." Example References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Overworld] | [TOKENS: 588] |
Contents Overworld An overworld or a hub world is, in a broad sense, an area within a video game that interconnects all its levels or locations. They are mostly common in role-playing games, though this does not exclude other video game genres, such as some platformers and strategy games. Description An overworld or hub world is an area within a video game which connects its other levels or locations. The term can also refer to a safer area which players frequently return to, like a town. They are common in adventure games, role-playing games (RPGs), platformers, and dungeon crawlers. Multiplayer games have hub worlds which serve as a centre for interaction with other players and non-player characters (NPCs). Hub worlds in single-player games are often used for worldbuilding, while hubs in multiplayer games are more purposed for storage for weapons and equipment, as well as restocking supplies. They serve as safe areas in between dangerous areas and quests where players can take on more passive actions. Wired and Kotaku described overworlds as a sort of "home" for the player in-game. They have also been considered an essential element of RPGs. History The 1981 arcade games Route-16 and 005 were among the earliest examples of a hub world. In Route-16, a driving maze game, exiting a maze takes the player to a large overworld map showing the locations of the player, cars, mazes and treasures. In 005, an early stealth game, players could enter buildings like ice rinks and warehouses from the main screen to avoid enemies, leading to different screens. The final scene tasks the players with controlling their getaway helicopter to escape and finish the level. Dubbed "a game in four screens", 005 was then described as a "RasterScan Convert-a-Game" according to The Encyclopedia of Arcade Games. In Super Mario 64 (1996), Princess Peach's Castle serves as its hub world. Free of enemies, the castle serves as a safe area where players can experiment with its movement system and serves as an entrance to all other levels. Players are free to leave the castle whenever they wish. Audio design In terms of video game music, overworld themes are often orchestral in nature, and of greater length and complexity than other pieces in the same game, due to the amount of time spent travelling the overworld map.[citation needed] Because players will usually visit a single level or area a few times in a given play session, the music for any such section of the game will typically be shorter and/or less complex, and thus less time-consuming for the designers to produce. The overworld theme frequently functions as the main theme of a game, often used as a motif for other tracks (e.g., a "romance" theme features the main melody of the overworld theme, orchestrated in a different key). See also References Further reading |
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